Point-of-Care Ultrasound and Right Ventricular Strain: Utility in the Diagnosis of Pulmonary Embolism

Ramzi Ibrahim MD, João Paulo Ferreira MD

Department of Medicine, University of Arizona – Tucson and Banner University Medical Center

Tucson AZ USA

Abstract

Pulmonary emboli are associated with high morbidity and mortality, prompting early diagnostic and therapeutic considerations. Utilization of rapid point-of-care ultrasound (POCUS) to assess for signs of pulmonary emboli can provide valuable information to support immediate treatment. We present a case of suspected pulmonary embolism in the setting of pharmacological prophylaxis for venous thromboembolism with identification of right heart strain on bedside POCUS exam. Early treatment with anticoagulation was initiated considering the clinical presentation and POCUS findings. CT angiogram of the chest revealed bilateral pulmonary emboli, confirming our suspicion. Utilizing POCUS in a case of suspected pulmonary emboli can aid in clinical decision making.

Case Presentation

Our patient is a 50-year-old man with a history of morbid obesity, obstructive sleep apnea, and poorly controlled diabetes mellitus type 2 who was admitted to the hospital for sepsis secondary to left foot cellulitis and found to have left foot osteomyelitis with necrosis of the calcaneus. The patient was started on intravenous antimicrobials, underwent incision and debridement, and completed a partial calcanectomy of the left foot. During the hospital course, he remained on subcutaneous unfractionated heparin at 7,500 units three times a day for prevention of deep vein thrombosis. On post-operative day 12, he developed acute onset of dyspnea requiring 2 liters of supplemental oxygen and was slightly tachycardic in the low 100s. He complained of chest tightness without pain, however, he denied lower extremity discomfort, palpitations, orthopnea, or diaphoresis. Electrocardiogram was remarkable for sinus tachycardia without significant ST changes, T-wave inversions, conduction defects, or QTc prolongation. Rapid point-of-care ultrasound (POCUS) at bedside revealed interventricular septal bowing, hypokinesia of the mid free right ventricular wall, and increased right ventricle to left ventricle size ratio (>1:1 respectively) (Figures 1 and 2).

Figure 1. A: Static apical 4-chamber view showing interventricular bowing into the left ventricle (blue arrow), significantly enlarged right ventricle, and right ventricular free wall hypokinesia (green arrow). B: Video of apical 4-chamber view.

Figure 2. A: Static parasternal short axis view showing interventricular septal bowing in the left ventricle (green arrow). B: Video of parasternal short axis view.

With these findings, the patient was started on therapeutic anticoagulation. CT angiogram of the chest revealed a large burden of bilateral pulmonary emboli (PE). The pulmonary embolism severity index (PESI) score was 130 points which is associated with a 10%-24.5% mortality rate in the following 30 days. Formal echocardiogram showed a severely dilated right ventricle with reduced systolic function, paradoxical septal movement, and a D-shaped left ventricle. Patient remained hemodynamically stable and was discharged home after transition from heparin to rivaroxaban.

Discussion

Pulmonary emboli remain a commonly encountered pathological phenomenon in the hospital setting with a mortality rate ranging from <5% to 50% (1). Venous thromboembolism prophylaxis has been shown to reduce the risk of VTE in hospitalized patients, however, this does not eliminate the risk completely. Prompt diagnosis allows earlier treatment and improved outcomes however this is often challenging given the lack of specificity associated with its characteristic clinical symptoms (2). In the proper context, utilization of POCUS can aid the diagnosis of PE by assessing for signs of right ventricular strain. Characteristic findings seen on a cardiac-focused POCUS that represent right ventricular strain include McConnell’s sign (defined as right ventricular free wall akinesis/hypokinesis with sparing of the apex), septal flattening, right ventricular enlargement, tricuspid regurgitation, and tricuspid annular plane systolic excursion under 1.6 cm (3). Their respective sensitivities and specificities are highly dependent on the pre-test probability. For example, a prospective cohort study completed by Daley et al. (4) in 2019 showed that for patients with a clinical suspicion of PE, sensitivity of right ventricular strain was 100% for a PE in patients with a heart rate (HR) >110 beats per minute, and a sensitivity of 92% if HR >100 BPM. This study provides evidence to support the use of cardiac focused POCUS in ruling out pulmonary emboli in patients with signs of right ventricular strain and abnormal hemodynamic parameters such as tachycardia. Additionally, in settings where hemodynamic instability is present and the patient cannot be taken to the CT scanner for fear of decompensation, rapid POCUS assessment can be helpful. In our patient, given the acute need for supplemental oxygenation and dyspnea, along with his risk factors for a thromboembolic event, the use of POCUS aided in our clinical decision making. The yield of information that can be provided by POCUS is vital for early diagnostic and therapeutic decision making for patients with a clinical suspicion of pulmonary emboli.

References

1. Torbicki A, Perrier A, Konstantinides S, et al. Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC). Eur Heart J. 2008 Sep;29(18):2276-315. [CrossRef][PubMed]
2. Roy PM, Meyer G, Vielle B, et al. Appropriateness of diagnostic management and outcomes of suspected pulmonary embolism. Ann Intern Med. 2006 Feb 7;144(3):157-64. [CrossRef][PubMed]
3. Alerhand S, Sundaram T, Gottlieb M. What are the echocardiographic findings of acute right ventricular strain that suggest pulmonary embolism? Anaesth Crit Care Pain Med. 2021 Apr;40(2):100852. [CrossRef] [PubMed]
4. Daley JI, Dwyer KH, Grunwald Z, et al. Increased Sensitivity of Focused Cardiac Ultrasound for Pulmonary Embolism in Emergency Department Patients With Abnormal Vital Signs. Acad Emerg Med. 2019 Nov;26(11):1211-1220. [CrossRef][PubMed]

Cite as: Ibrahim R, Ferreira JP. Point-of-Care Ultrasound and Right Ventricular Strain: Utility in the Diagnosis of Pulmonary Embolism. Southwest J Pulm Crit Care Sleep. 2022;25(2):34-36. doi: https://doi.org/10.13175/swjpccs040-22 PDF

Ultrasound for Critical Care Physicians: Caught in the Act

Uzoamaka Ogbonnah MD¹

Isaac Tawil MD²

Trenton C. Wray MD²

Michel Boivin MD¹

¹Department of Internal Medicine

²Department of Emergency Medicine

University of New Mexico School of Medicine

Albuquerque, NM USA

A 16-year-old man was brought to the Emergency Department via ambulance after a fall from significant height. On arrival to the trauma bay, the patient was found to be comatose and hypotensive with a blood pressure of 72/41 mm/Hg. He was immediately intubated, started on norepinephrine drip with intermittent dosing of phenylephrine, and transfused with 3 units of packed red blood cells. He was subsequently found to have extensive fractures involving the skull and vertebrae at cervical and thoracic levels, multi-compartmental intracranial hemorrhages and dissection of the right cervical internal carotid and vertebral arteries. He was transferred to the intensive care unit for further management of hypoxic respiratory failure, neurogenic shock and severe traumatic brain injury. Following admission, the patient continued to deteriorate and was ultimately declared brain dead 3 days later. The patient’s family opted to make him an organ donor

On ICU day 4, one day after declaration of brain death, while awaiting organ procurement, the patient suddenly developed sudden onset of hypoxemia and hypotension while being ventilated. The patient had a previous trans-esophageal echo (TEE) the day prior (Video 1). A repeat bedside TEE was performed revealing the following image (Video 2).

Video 1. Mid-esophageal four chamber view of the right and left ventricle PRIOR to onset of hypoxemia.

Video 2. Mid-esophageal four chamber view of the right and left ventricle AFTER deterioration.

What is the cause of the patient’s sudden respiratory deterioration? (Click on the correct answer to be directed to an explanation)

1. Atrial Myxoma
2. Fat emboli syndrome
3. Thrombus in-transit and pulmonary emboli
4. Tricuspid valve endocarditis

Cite as: Ogbonnah U, Tawil I, Wray TC, Boivin M. Ultrasound for critical care physicians: Caught in the act. Southwest J Pulm Crit Care. 2018;17(1):36-8. doi: https://doi.org/10.13175/swjpcc091-18 PDF 

Ultrasound for Critical Care Physicians: A Pericardial Effusion of Uncertain Significance

Brandon Murguia  M.D.

Department of Medicine

University of New Mexico School of Medicine

Albuquerque, NM USA

A 75-year-old woman with known systolic congestive heart failure (ejection fraction of 40%), chronic atrial fibrillation on rivaroxaban oral anticoagulation, morbid obesity, and chronic kidney disease stage 3, was transferred to the Medical Intensive Care Unit for acute hypoxic respiratory failure thought to be secondary to worsening pneumonia.

She had presented to the emergency department 3 days prior with shortness of breath, malaise, left-sided chest pain, and mildly-productive cough over a period of 4 days. She had mild tachycardia on presentation, but was normotensive without tachypnea, hypoxia, or fever. Routine labs were remarkable for a leukocytosis of 15,000 cells/μL. Cardiac biomarkers were normal, and electrocardiogram demonstrated atrial fibrillation with rapid ventricular rate of 114 bpm. Chest x-ray revealed cardiomegaly and left lower lobe consolidation consistent with bacterial pneumonia. Patient was admitted to the floor for intravenous antibiotics, cardiac monitoring, and judicious isotonic fluids if needed.

On night 2 of hospitalization, the patient developed respiratory distress with tachypnea, pulse oximetry of 80-85%, and increased ventricular response into the 140 bpm range. The patient remained normotensive. A portable anterior-posterior chest x-ray showed cardiomegaly and now complete opacification of the left lower lobe. She was transferred to the MICU for suspected worsening pneumonia and congestive heart failure.

Upon arrival to the intensive care unit, vital signs were unchanged and high-flow nasal cannula was started at 6 liters per minute. A focused point-of-care cardiac ultrasound (PCU) was done, limited in quality by patient body habitus, but nonetheless demonstrating the clear presence of a moderate pericardial effusion on subcostal long axis view.

Figure 1: Subcostal long axis view of the heart.

What should be done next regarding this pericardial effusion? (Click on the correct answer for the answer and explanation)

1. Observe, this is not significant.
2. Additional echocardiographic imaging /evaluation.
3. Immediate pericardiocentesis.
4. Fluid challenge.

Cite as: Murguia B. Ultrasound for critical care physicians: a pericardial effusion of uncertain significance. Southwest J Pulm Crit Care. 2016;13(5):261-5. doi: https://doi.org/10.13175/swjpcc127-16 PDF

Ultrasound for Critical Care Physicians: Now My Heart Is Still Somewhat Full

Krystal Chan, MD

Bilal Jalil, MD

Department of Internal Medicine

University of New Mexico School of Medicine

Albuquerque, NM USA

A 48-year-old man with a history of hypertension, intravenous drug abuse, hepatitis C, and cirrhosis presented with 1 day of melena and hematemesis. While in the Emergency Department, the patient was witnessed to have approximately 700 mL of hematemesis with tachycardia and hypotension. The patient was admitted to the Medical Intensive Care Unit for hypotension secondary to acute blood loss. He was found to have a decreased hemoglobin, elevated international normalized ratio (INR), and sinus tachycardia. A bedside echocardiogram was performed.

Figure 1. Apical four chamber view of the heart.

Figure 2. Longitudinal view of the inferior vena cava entering into the right atrium.

What is the best explanation for the echocardiographic findings shown above? (Click on the correct answer for an explanation and discussion)

1. Atrial Fibrillation
2. Atrial Myxoma
3. Cardiac Lymphoma
4. Tricuspid Valve Endocarditis
5. Tumor Thrombus

Cite as: Chan K, Jalil B. Ultrasound for critical care physicians: now my heart is still somewhat full. Southwest J Pulm Crit Care. 2016;12(6):236-9. doi: http://dx.doi.org/10.13175/swjpcc054-16 PDF 

Ultrasound for Critical Care Physicians: Two’s a Crowd

A 43 year old previously healthy woman was transferred to our hospital with refractory hypoxemia secondary to acute respiratory distress syndrome (ARDS) due to H1N1 influenza. She had presented to the outside hospital one week prior with cough and fevers. Chest radiography and computerized tomography of the chest revealed bilateral airspace opacities due to dependent consolidation and bilateral ground glass opacities. A transthoracic echocardiogram at the time of the patient’s admission was reported as not revealing any significant abnormalities.

At the outside hospital she was placed on mechanical ventilation with low tidal volume, high Positive end-expiratory pressure (20 cm H20), and a Fraction of inspired Oxygen (FiO2) of 1.0. Paralysis was later employed without significant improvement.

Upon arrival to our hospital, patient was severely hypoxemic with partial pressure of oxygen / FiO2  (P/F) ratio of 43. She was paralyzed with cis-atracurium and placed on airway pressure release ventilation (APRV) with the following settings (pressure high 28 cm H2O, pressure low 0 cm H2O, time high 5.5 sec, time low 0.5 sec). The patient remained severely hypoxemic with on oxygen saturation in the high 70 percent range.

A bedside echocardiogram was performed (Figures 1 and 2).

Figure 1. Subcostal long axis echocardiogram.

Figure 2. Subcostal short axis echocardiogram

What abnormality is demonstrated by the short and long axis subcostal views? (Click on the correct answer for an explanation)

1. Acute cor pulmonale likely due to ARDS
2. Acute myocardial infarction
3. Low left-sided ejection fraction
4. Pericardial tamponade

Cite as: Abukhalaf J, Boivin M. Ultrasound for critical care physicians: two's a crowd. Southwest J Pulm Crit Care. 2016 Mar;12(3):104-7. doi: http://dx.doi.org/10.13175/swjpcc028-16 PDF

Ultrasound for Critical Care Physicians: Hungry Heart

A 31-year-old incarcerated man with a past medical history of intravenous drug use and hepatitis C, presented with a one week history of dry, non-productive cough, orthopnea and exertional dyspnea. He denied current intravenous drug use, and endorsed that the last time he used was before he was incarcerated over 3 years ago, his last tattoo was in prison, 6 months prior. He was found to have an oxygen saturation of 77% on room air, fever of 40º C, heart rate of 114 bpm, and blood pressure of 80/50 mmHg. The patient had a leukocytosis of 14 x10⁹/L, and a chest x-ray demonstrating patchy airspace disease. Blood cultures were sent and he was treated with antibiotics and vasopressors for septic shock. The patient was intubated for acute hypoxemic respiratory failure secondary to multifocal pneumonia. A bedside transthoracic echocardiogram was performed. 

Figure 1. Apical four chamber view echocardiogram with color Doppler over the mitral valve.

Figure 2. Right Ventricular (RV) inflow view echocardiogram from same patient

What is the likely diagnosis supported by the echocardiogram? (Click on the correct answer for an explanation)

1. Massive pulmonary embolism
2. Mitral valve endocarditis
3. Pericardial tamponade
4. Tricuspid valve endocarditis

Cite as: Villalobos N, Stoltze K, Azeem M. Ultrasound for critical care physicians: hungry heart. Southwest J Pulm Crit Care. 2016;12(1):24-7. doi: http://dx.doi.org/10.13175/swjpcc007-16 PDF

Ultrasound for Critical Care Physicians: Now My Heart Is Even More Full

Bilal Jalil, MD

Michel Boivin, MD

Division of Pulmonary, Critical Care and Sleep Medicine

University of New Mexico School of Medicine

Albuquerque, NM

A 49-year-old man with type 2 diabetes, intravenous drug abuse and heart failure presented to the emergency room with 2 weeks of progressively worsening chest pain, lower extremity swelling and shortness of breath. The patient was found to have an elevated troponin as well as brain natriuretic peptide and the absence of ischemic electrocardiogram findings. The patient was admitted to the medical ICU for hypoxic respiratory failure and shock of uncertain etiology. Clinically he seemed to be in decompensated heart failure and a bedside echocardiogram was performed (Figures 1 and 2).

Figure 1. Parasternal short axis view at the level of the aortic valve

Figure 2. Apical 4 chamber view.

What is the best explanation for the echocardiographic findings shown above? (Click on the correct answer for the explanation)

1. Atrial myxoma
2. Cardiac amyloidosis
3. Cardiac lymphoma
4. Takotsubo cardiomyopathy
5. Tricuspid valve endocarditis

Reference as: Jalil B, Boivin M. Ultrasound for critical care physicians: now my heart is even more full. Souhtwest J Pulm Crit Care. 2015;10(2):83-6. doi: http://dx.doi.org/10.13175/swjpcc020-15 PDF

Ultrasound for Critical Care Physicians: A Tempting Dilemma

Issam Marzouk MD

Lana Melendres MD

Michel Boivin MD

Division of Pulmonary, Critical Care and Sleep

Department of Medicine

University of New Mexico School of Medicine

MSC 10-5550

Albuquerque, NM 87131 USA

A 46 year old woman presented with progressive severe hypoxemia and a chronic appearing pulmonary embolus on chest CT angiogram to the intensive care unit. The patient was hemodynamically stable, but had an oxygen saturation of 86% on a high-flow 100% oxygen mask. The patient had been previously investigated for interstitial lung disease over the past 2 year, this was felt to be due to non-specific interstitial pneumonitis. Her echocardiogram findings are as presented below (Figures 1 and 2).

Figure 1. Parasternal long axis view. Upper panel: static image. Lower panel: video.

 

Figure 2. Apical four chamber view. Upper panel: static image. Lower panel: video

The patient had refractory hypoxemia despite trials of high flow oxygen and non-invasive positive pressure ventilation. She had mild symptoms at rest but experienced severe activity intolerance secondary to exertional dyspnea. Vitals including blood pressure remained stable and normal during admission and the patient had a pulsus paradoxus measurement of < 10 mmHg. She had previously had an echocardiogram 6 months before that revealed significant pulmonary hypertension.

What would be the most appropriate next step regarding management of her echocardiogram findings? (click on the correct answer to move to the next panel)

1. Diagnostic pericardiocentesis
2. Urgent therapeutic pericardiocentesis
3. Avoid pericardiocentesis at this time
4. Urgent thrombolysis with tissue plasminogen activator

Reference as: Marzouk I, Melendres L, Boivin M. Ultrasound for critical care physicians: a tempting dilemma. Southwest J Pulm Crit Care. 2014;9(3):193-6. doi: http://dx.doi.org/10.13175/swjpcc128-14 PDF

Ultrasound for Critical Care Physicians: Cardiogenic Shock-This Is Not a Drill

Ramakrishna Chaikalam, MD 

Shozab Ahmed, MD

Division of Pulmonary, Critical Care and Sleep

University of New Mexico

Albuquerque, NM

A 45-year-old woman with no significant past history developed gradual onset of shortness of breath and cough over 1 week. She presented to the emergency department. Her initial chest x-ray showed an enlarged heart and bilateral pulmonary edema. The patient became progressively hypotensive and hypoxic and was intubated. Transthoracic echocardiography is shown below (Figure 1).

Figure 1. Transthoracic echocardiogram in the para-sternal long axis view of the heart.

What intra-cardiac device in the left ventricle is pictured on the image? (Click on the correct answer to proceed to the next panel)

1. Amplatz closure device of atrial septal defect
2. Extracorporeal membrane oxygenator (ECMO) cannula
3. Impella device
4. Intra-aortic balloon pump
5. Pacemaker lead

Reference as: Chaikalam R, Ahmed S. Ultrasound for critical care physicians: cardiogenic shock-this is not a drill. Southwest J Pulm Crit Care. 2014;9(1):27-9. doi: http://dx.doi.org/10.13175/swjpcc091-14 PDF

Ultrasound for Critical Care Physicians: Really, At Her Age?

A 71 year old woman presented with dyspnea since late 2013 and denies a prior history of dyspnea. She had a cardiac pacemaker placed in 2008 for sick sinus syndrome. Her physical exam was unremarkable and her SpO2 was 96% on room air. However,  it decreased to 84% with exercise. Chest x-ray and pulmonary function testing were unremarkable (a DLco was unable to be performed). A transthoracic echocardiogram was performed (Figure 1).

Figure 1. Movie with Doppler flow of transthoracic echocardiogram. 

Which of the following best explains the patient's dyspnea and hypoxia? (Click on the correct answer to proceed to the next panel)

1. Cardiac tamponade
2. Decreased cardiac contractility
3. Intracardiac shunt
4. Mitral insufficiency
5. Ventilation perfusion mismatch from COPD

Reference as: Wesselius LJ. Ultrasound for critical care physicians: really, at her age? Southwest J Pulm Crit Care. 2014;8(5):278-9. doi: http://dx.doi.org/10.13175/swjpcc061-14 PDF

Ultrasound for Critical Care Physicians: Hypotension After a MVA

A 25 year old woman was a restrained driver in a rollover motor vehicle accident (MVA) and suffered a C5-C6 fracture-dislocation with spinal cord injury. She was lucid and able to follow commands and could move her upper extremities but not her lower extremities. She was given approximately 6 liters of fluid but required vasopressors to maintain her blood pressure. Initial ECG revealed a normal sinus rhythm without significant ST changes (Figure 1).

Figure 1. Initial ECG.

Upon initial evaluation her blood pressure was low. Bedside ultrasound of the left anterior second intercostal space revealed a sliding lung sign and a 4 chamber view of her heart  was performed (Figure 2).

Figure 2. Four chamber view from the cardiac ultrasound.  

Which of the following is the most likely cause of her hypotension?

1. Blunt cardiac injury
2. Intravascular volume depletion
3. Neurogenic stunned myocardium
4. Pericardial tamponade
5. Pneumothorax

Reference as: Schmitz ED. Ultrasound for critical care physicians: hypotension after a MVA. Southwest J Pulm Crit Care. 2014;8(3):176-8. doi: http://dx.doi.org/10.13175/swjpcc023-14 PDF

Resuscitative EChocardiography for the Evaluation and management of Shock: The RECES protocol

Jarrod M. Mosier^1,2

Lori Stolz^1,

John Bloom²

Josh Malo²

Linda Snyder²

Albert Fiorello¹

Srikar Adhikari¹

¹ Department of Emergency Medicine, University of Arizona, Tucson, AZ

²Department of Medicine, Section of Pulmonary, Critical Care, Allergy and Sleep, University of Arizona, Tucson, AZ

Abstract  

Purpose: Ultrasound use by emergency medicine and critical care physicians in the evaluation of the critically ill patient has increased in recent years. Several protocols exist to aid in diagnosing the etiology of shock and identifying rapidly reversible conditions in the undifferentiated hypotension patient. Currently, no protocol provides hemodynamic data or is designed to guide ongoing resuscitation of the critically ill patient with hypotension.

Methods: An evidence-based protocol was developed based on the components of echocardiography that have been supported in the literature for bedside evaluation of the critically ill patient.

Results: The RECES protocol provides diagnostic and hemodynamic information regarding volume responsiveness , presence of pericardial effusion with tamponade physiology (right ventricular diastolic collapse), systolic failure (poor contractility, decreased stroke volume and cardiac output), diastolic dysfunction (mitral valve inflow velocities and tissue Doppler), Right ventricular systolic failure, acute valvular rupture, obvious wall motion abnormalities, and signs of pressure or volume overload (septal flattening on parasternal short axis).

Conclusion: The RECES protocol is a proposed instrument for rapidly and repeatedly assessing the etiology and initial hemodynamic parameters of the patient in shock. Additionally, repeated exams will allow monitoring interventions and guide ongoing resuscitation.

Introduction  

Ultrasound has become indispensible for emergency medicine physicians and intensivists in the evaluation and management of patients in shock. Bedside ultrasound is no longer used solely for central line placement and the diagnosis of intra-abdominal free fluid. The emergency bedside applications being used with frequency span nearly every body system. The body of literature substantiating the ability of clinicians to accurately perform and interpret point-of-care ultrasound studies is robust and growing.

For patients in shock, several goal-directed ultrasound protocols have been described in the literature. Each of these is aimed at finding rapidly reversible etiologies of shock in the undifferentiated hypotensive patient (i.e. tamponade, pneumothorax, intra-abdominal hemorrhage) (1-6). Though similar in their aim, they each differ in respect to the pathology sought, views obtained and the scope of the exam. Of these protocols, systematic study has been undertaken in only two. Jones et al. (2) have demonstrated that goal-directed ultrasound early in the presentation of patients with shock can improve the accuracy of the treating physician’s diagnosis within 15 minutes of patient arrival from 50% accuracy at baseline to 80% accuracy with the use of ultrasound. Manno et al. (6) found a bedside ultrasound protocol in all admitted ICU patients changed the admitting diagnosis in 25.6% of patients, prompted further testing in 18.4% of patients and altered medical therapy in 17.6% of patients.

Bedside cardiac ultrasound in particular has been adopted as a key component of the emergent evaluation of critically ill patients (7,8). Cardiac ultrasound in the hands of non-cardiologist and non-radiologist clinicians has been shown to be accurate and reliable in diagnosing a wide array of pathologies. One paper has described a limited echocardiography protocol for use in trauma intensive care patients with the aim of evaluating for pericardial effusion, ventricular function and volume status (9). All whole-body sonography protocols that have been described for the evaluation of shock incorporate a limited cardiac exam. Within both studies described above, the cardiac portion yielded positive findings most frequently (2,6). However, despite these advances in clinical practice, to our knowledge no standardized, goal-directed bedside echocardiography protocol currently exists to guide the ongoing resuscitation of patients in shock.

This novel goal-directed echocardiography protocol was developed to provide immediate diagnostic information as to the etiology of shock similar to other protocols as well as provide hemodynamic information useful to guiding and assessing therapy during ongoing resuscitation. The protocol is taught to critical care and emergency ultrasound fellows at our institution as well as emergency medicine residents rotating in the ICU. It is designed to go beyond diagnosing the etiology of shock and to guide on-going resuscitation of critically ill patients through their hemodynamic crisis. The initial exam serves as a benchmark to which future exams are compared, and subsequent exams monitor the hemodynamic response to interventions. The intention is that this protocol be used on a recurring and as-needed basis to supplement the standard hemodynamic monitoring in a patient with shock

This protocol [Table 1] is evidence-based.

Table 1. Evaluation parameters: Goal-directed Assessment.  (Editor's note: the size on your browser may need to be enlarged to adequately view the table).  

It incorporates the elements of the bedside cardiac exam that have been proven in the literature to be accurate and useful in the emergency setting. It is not designed to replace standard comprehensive echocardiography but rather to be used in locations or situations where obtaining a complete echocardiogram is not possible or feasible given time of day, availability of formal echo services and clinical condition of the patient. Additionally, the protocol can be repeated after an intervention to assess progress during resuscitation whereas repeated formal echocardiograms are not reasonable. The information obtained at the bedside from this protocol is potentially useful for diagnosing the etiology of shock, and guiding resuscitation of patients with hemodynamic instability. It is not intended to manage the subtleties of chronic cardiovascular disease or valvular disease.

A key element to the use of this protocol is the potential to determine response to therapy to help on-going resuscitation of patients with hemodynamic instability. In a volume-depleted patient, for example, a repeat exam could be performed following each fluid bolus. Traditionally, clinical exam findings of excessive fluid administration can be monitored but occur after the desired intravascular volume status has been surpassed and possible patient harm has been done. A patient in shock who, after several liters of fluid, no longer demonstrates intravascular volume depletion can be assuredly started on vasopressors. Additionally, a patient who continues to demonstrate volume responsiveness with a large stroke volume may be started on vasopressors in the setting of diastolic failure. This phenomenon is also seen as a result in increased arterial elastance which is unlikely to improve from further fluid administration.

This protocol [Table 1] proceeds with several qualitative questions along with obtaining several quantitative hemodynamic parameters in the process. Following is a description of each step in the protocol:

1. Pericardial effusion

Q: Is there a pericardial effusion present? Yes or No

Q: If there is a pericardial effusion present, is there evidence of tamponade physiology (i.e. right ventricular diastolic collapse and/or plethoric inferior vena cava)? Yes or No

This protocol begins with an evaluation for pericardial effusion. The use of bedside ultrasound to diagnose pericardial effusion was one of the first applications employed by emergency medicine and critical care specialists. Emergency physicians can detect pericardial effusion on bedside ultrasound with a sensitivity of 96% and a specificity of 98% (10). Hand-carried ultrasound units have been used in cardiac ICUs to identify pericardial effusion (11). Although the sensitivity and specificity of these handheld units was 75% and 88% respectively, for all effusions, all false negatives had less than 20 mls of pericardial fluid on contrast enhanced CT and all false positives were estimated to be trace as well (11). Bedside ultrasound in undifferentiated dyspneic patients found pericardial effusion in 13.6% of patients, 29% of which required pericardiocentesis (12). If identified, the clinician can then evaluate for echocardiographic signs of tamponade. The elements of comprehensive echocardiographic evaluation for tamponade that are likely to be obtainable with a bedside machine by a non-cardiologist clinician are right ventricular diastolic collapse and inferior vena cava plethora (Figure 1) (13,14). However, as described below, inferior vena cava plethora can be caused by any elevation of right-sided pressures and should be interpreted in the context of the other findings on the exam.

Figure 1. Panel A: Plethoric, non-collapsible IVC suggests elevated right sided pressures or tamponade physiology. Panel B: Presence of pericardial effusion on subxyphoid view is small, but shows diastolic right ventricular collapse. Panel C: M-mode on parasternal long axis suggests tamponade physiology.

2. Global systolic function

Q: Is the left ventricular global systolic function decreased, normal, or hyperdynamic?

Q: What is the stroke volume and cardiac output?

In this protocol, left ventricular systolic function is assessed globally and is graded as decreased, normal, or hyperdynamic, rather than quantitatively estimating left ventricular ejection fraction (LVEF). Although LVEF is a numerical representation of left ventricular function, it is difficult to obtain in the acute setting and influenced by critical illness, as well as anatomic and physiologic factors limiting adequate endocardial visualization (15). Additionally, as LVEF is not influenced by hemodynamic parameters (preload, afterload), it is less useful for the acute hemodynamic evaluation of the patient in shock (16). E-point septal separation (EPSS) has been compared to magnetic resonance imaging methods of calculating ejection fraction with good correlation; however that correlation declines in the presence of wall motion abnormalities and valvular disease (17,18). Ahmadpour et al. (19) demonstrated EPSS to be a reliable index of ventricular performance in coronary artery disease patients but only as a predictor of decreased ejection fraction rather than estimating the exact ejection fraction. Secko et al. (20) showed that novice emergency physician obtained EPSS measurements correlated well with visual estimates of EF; however EPSS as a continuous variable did not correlate well with fractional shortening measurements in a study by Weekes et al. (21). These data would suggest that estimating LVEF by either estimating quantitatively or by EPSS is inconsistent and not indicative of the underlying hemodynamic state. Instead of attempting to quantify ejection fraction, this protocol uses visual estimates of LV systolic function obtained in each view, which have been shown to be accurate and easily performed at the bedside (16,22-24).

3.   IVC

Q: Is the IVC small (<2cm) or large (>2cm)?

Q: Is the IVC dynamic (>20% change in diameter with respiration)?

Assessing volume responsiveness in hypotensive patients is of paramount importance for restoring intravascular volume without deleteriously volume overloading the patient, which has been shown to worsen outcomes (25-28).Traditionally, central venous pressure (CVP) has been used as an endpoint of volume resuscitation (29). CVP as a measure of ventricular preload has been shown to poorly correlate with intravascular volume status and volume responsiveness (30-32). Rather than static CVP measurements, dynamic volume assessments reflected by cardiopulmonary interactions are more accurate and reliable for predicting improved cardiac index with volume infusion (33-40). Bedside ultrasound assessment of dynamic changes in inferior vena cava diameter with either distensibility (IVCd) in the case of a mechanically ventilated patient or collapsibility in a spontaneous breathing is a pre-heart/lung observation of cardiopulmonary interactions and has been shown to be reliable for predicting volume responsiveness (34,35,39,41,42). This protocol uses IVCd as one of three assessments of volume responsiveness along with obliteration of the LV cavity on parasternal short axis (papillary level) and left ventricular outflow tract VTi. Since evidence of IVCd measurement in the presence of cirrhosis and alternative ventilator modes such as airway pressure release ventilation (APRV) is lacking, it is not ideal as the sole assessment for volume responsiveness. A plethoric IVC can be seen in both high right-sided pressure (pulmonary embolism, RV infarct) and in tamponade physiology. A plethoric IVC in the absence of pericardial effusion should alert the physician to the presence of high right-sided pressure or RV volume overload. Additionally, determination of adequate intravascular volume status can guide clinicians in initiation or titration of pressor support.

4. Volume Responsiveness

Q: Does this patient appear to be volume responsive (i.e. in addition to IVC collapsibility, is there a hyperdynamic LV with cavity obliteration on systole and is there variability in the LVOT VTi)? Yes or No

In addition to IVCd, this protocol uses a global assessment of the left ventricular dynamics and the left ventricular outflow tract velocity time integral (LVOT VTi) respiratory variation as assessments of volume responsiveness (Figure 2).

Figure 2. Collapsibility of the IVC (Panel A, top left), hyperdynamic left ventricle with obliteration of the LV cavity on parasternal short axis (Panel B, top right), and variability of the left ventricular outflow tract with inspiration (Panel C, bottom) are indicators of volume responsiveness.

Left ventricular end diastolic area (LVEDA), if seen as cavitary obliteration or “kissing papillary muscles” on parasternal short axis, has been shown to correlate with the presence of hypovolemia (43,44). LVOT VTi variability has recently been shown to correlate well with non-invasive cardiac output monitors to determine volume responsiveness in hypotensive patients (45,46). The LVOT VTi obtained on an apical 5 chamber can be used with the LVOT diameter obtained in the parasternal long axis view to calculate the stroke volume and cardiac output (Figure 3) (47,48).

Figure 3. Stroke volume (SV) and cardiac output. The stroke volume is calculated by measuring the diameter of the LVOT on parasternal long axis (Panel A, left) and the LVOT VTi (Panel B, right) [SV= Vti x π(LVOTd/2)²]. Cardiac output is calculated by multiplying SV by the heart rate.

The LVOT VTi represents a Doppler assessment of cardiopulmonary interactions that translates to stroke volume variation, pulse pressure variation, and systolic pressure variation as seen on an arterial line tracing which has been well correlated with volume responsiveness (33,36,37,41,42,49).

Case 1:  A 48-year-old male is admitted to the intensive care unit (ICU) with septic shock secondary to spontaneous bacterial peritonitis. He had received several liters of crystalloid in the ED and remains hypotensive with poor perfusion. RECES protocol was performed on admission to the ICU, which demonstrated the patient was volume responsive; however the stroke volume and cardiac output were elevated suggesting increased vascular elastance rather than intravascular volume depletion. The patient was placed on a vasopressor with improved tissue perfusion and indicators of shock.

5. Diastolic dysfunction

Q: Is there diastolic dysfunction? Yes or No

Q: Is there evidence of elevated left atrial pressure? Yes or No

Diastoloic dysfunction plays an increased role as patients age or have chronic hypertension (50). Hemodynamically, this leads to an increased likelihood of pulmonary edema with aggressive fluid resuscitation, which has been shown to increase mortality (25,27,28). In this protocol, mitral valve inflow velocities by pulsed wave Doppler (PWD) are used to assess diastolic dysfunction. Mitral E and A waves accurately reflect the pressure gradient between the left atrium and left ventricle and have been shown to be superior to LVEF for estimation of left ventricular function (50). Mitral annulus tissue Doppler (TDI) is used to differentiate between pseudonormal inflow velocity patterns and decreased LV compliance as well as estimate left atrial pressure (50). In grade I diastolic dysfunction, mitral inflow velocities demonstrate an E-A reversal. As left ventricular compliance worsens, the E-A pattern returns to normal; however, the velocities increase, representing the left atrium “pushing” the blood into the left ventricle rather than the ventricle “sucking” blood from the atrium as the cavitary pressure drops below atrial pressure in the normal heart (51). In mechanically ventilated patients diastolic velocities may be altered to some degree by changes in left ventricular compliance, mainly through changes in right ventricular compliance via ventricular interdependence. Additionally, estimated pulmonary artery systolic pressures >40mmHg in the absence of known pulmonary hypertension, lung disease, or systolic failure may indicate undiagnosed diastolic dysfunction and caution over-resuscitation with fluids. Emergency physicians can accurately perform this exam at the bedside as shown by Unluer and colleagues (52).

Case 2:  An 81-year-old male presents with 3 days of productive cough and fever. The patient is found to be hypotensive and tachycardic with high suspicion for severe sepsis. Electrocardiogram demonstrates LVH with strain, and labs are consistent with a severe sepsis syndrome. RECES protocol is performed on this patient which demonstrates grade III diastolic dysfunction and moderate mitral regurgitation which limited the amount of crystalloid given to avoid worsened pulmonary edema and ARDS.

6. Wall motion abnormalities

Q: Is there any obvious wall motion abnormality (global or regional)? Yes or No

In a critically ill patient, differentiating shock-induced cardiac dysfunction from cardiogenic shock is difficult. Serial troponins may be helpful but may also be misleading, as in the case of sepsis-induced cardiomyopathy. The consensus statement on the use of focused cardiac ultrasound in the emergent setting recommends comprehensive echocardiography for the diagnosis of wall motion abnormalities (8). To our knowledge, there exists only one paper evaluating the ability of non-cardiologist clinicians to diagnose wall-motion abnormalities. This study showed that a 30-minute training module significantly improved the ability of emergency physicians to identify wall motion abnormalities (53). Though this has not been studied directly, we postulate that a negative exam performed and interpreted by a non-cardiologist clinician, given the skill required in image acquisition and interpretation, does not rule out the presence of wall motion abnormalities. However, a clearly positive exam noted by a bedside clinician in a patient with undifferentiated or multi-factorial shock could dramatically improve the quality of their resuscitation. A positive exam will require interpretation in consideration with the clinical picture and ancillary data. For example, sepsis-induced cardiomyopathy may present as global hypokinesia or unmask underlying ischemic cardiac disease especially in the presence of vasopressors or inotropes. 

7. Right ventricle

Q: Is the right ventricle dilated? Yes or No

Q: Is there tricuspid regurgitation? Yes or No

Q: What is the systolic function of the right ventricle (TAPSE)?

Q: Is there evidence of right ventricular pressure or volume overload (i.e. septal flattening in systole or diastole)?

Q: What is the estimated pulmonary artery systolic pressure?

The right ventricular systolic movement differs greatly from the left ventricle. As opposed to the rotational component to left ventricular contraction, the right ventricular free wall moves towards the septum, followed by longitudinal contraction bringing the base towards the apex (54). As such, the tricuspid annular plane systolic excursion (TAPSE) using M-mode through lateral tricuspid annulus on an apical 4-chamber view is a reliable measurement of right ventricular systolic function (Figure 4) (54-57).

Figure 4. Tricuspid annular plane systolic excursion (TAPSE). M-mode through the lateral tricuspid annulus will demonstrate the amount of longitudinal excursion of the tricuspid annulus during systole. This has been shown to be a reliable indicator of right ventricular systolic function.

Elevations in RV afterload or decreases in contractility are reflected by a lower TAPSE (<16mm) (54,55). Septal movement is also used to demonstrate pressure or volume overload of the right ventricle. Obtained from a parasternal short axis view, septal flattening in systole represents pressure overload of the right ventricle whereas septal flattening in diastole represents volume overload (54). The presence of septal flattening along with a decreased TAPSE should alert the practioner to elevated pulmonary pressures and RV failure in the acutely hypotensive patient. Pulmonary artery systolic pressure can be calculated by continuous wave (CW) Doppler of the tricuspid regurgitation jet obtained on an apical 4 chamber view (p=4V²) (58). PA systolic pressure may be helpful to determine acute vs. chronic RV failure as the right ventricle is unable to overcome acute elevations in PA pressure >40mmHg (54,59,60).

Case 3:  A 56-year-old female presents by EMS with a seizure. She is found to be hypoxemic, unresponsive to supplemental oxygen, and hypotensive. She is given a fluid bolus immediately in the emergency department (ED), which worsens her hypotension and hypoxemia. The RECES protocol performed showed a dilated, hypodynamic right ventricle with a measured TAPSE of 12mm (severely decreased). tPA was administered and repeat RECES exam demonstrated an improved TAPSE of 16mm after 2 hours.  

8. Valves

Q: Is there obvious mitral, tricuspid, or aortic valve regurgitation? Yes or No

No systematic study has been performed evaluating the ability of emergency or critical care physicians to diagnose valvular pathology with bedside ultrasound. A study done comparing handheld bedside sonography performed by cardiologists to standard echocardiography found good agreement between studies in diagnosing morphologic aortic and mitral valvular pathology (61). Literature describing clinician-performed bedside echocardiography to diagnose valvular disease is limited to case reports (62-64). Despite this, a grossly abnormal valve could be recognizable by bedside clinician sonographers. In scenarios of papillary muscle rupture or valvular vegetations, recognition of these conditions would dramatically influence care. A strong regurgitant jet across the aortic or mitral valve in the setting of shock should alert the physician to acute valvular incompetence or, in the right clinical setting, endocarditis with valvular deterioration.

Limitations

The RECES protocol is not without its limitations. First, there requires a training period to not only learn the mechanics of acquiring the ultrasound images, but also gaining the knowledge base to interpret the findings and manipulate hemodynamics based on those findings. The protocol attempts to simplify complex echocardiographic principles into simple questions, however still requires somewhat intricate knowledge of hemodynamic principles to interpret. Although ultrasound training has become a required component of emergency medicine training and enthusiasm is increasing in critical care training, there still remains a large proportion of physicians in both specialties with limited to no ultrasound skills and would be required to attend a national course to gain the prerequisite skill. Secondly, although echocardiography is immensely helpful in the critically ill, it can also be very difficult in some patients. Many patients are intubated and cannot cooperate with positioning, obese, or have chronic lung disease limiting the ability to acquire appropriate views.

Conclusion

This protocol does not intend to replace comprehensive echocardiography. The machine quality and level of training of bedside clinicians cannot match the level of expertise available with comprehensive echocardiography. However, there are many scenarios in which comprehensive echocardiography cannot be feasibly obtained for a critically ill patient. This protocol is intended to be rapidly performed and allow a treating physician to make immediate clinical decisions when circumstances do not allow for comprehensive echocardiography. Additionally, a limitation of comprehensive echocardiography in the early period of resuscitation is that the information obtained can quickly become obsolete in the setting of a dynamic situation of disease progression and aggressive resuscitation. However, a key component of this protocol is re-evaluation throughout the resuscitation to account for these rapid changes.

Our experience with this protocol shows that others with similar or adequate training in echocardiography can use this protocol to determine the volume responsiveness (IVCd, LVOT VTi) of their patient as well as presence of pericardial effusion with tamponade physiology (RV diastolic collapse, MV inflow variability), systolic failure (poor contractility, decreased SV and CO), diastolic dysfunction (MV inflow velocities and TDI), RV systolic failure (TAPSE), acute valvular rupture, obvious wall motion abnormalities, and signs of pressure or volume overload (septal flattening on parasternal short axis). Future studies should evaluate the learning curve for mastering the ultrasound skills necessary for reliably performing the RECES protocol.

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Corresponding Author: 

Jarrod M. Mosier, MD

Assistant Professor

Department of Emergency Medicine

Department of Medicine, Section of Pulmonary, Critical Care, Allergy and Sleep

University of Arizona

1609 N Warren

FOB 122C

Tucson, Az 85719

Phone: 775-527-1292

Fax: 520-626-2480

jmosier@aemrc.arizona.edu

Disclosures: None for any authors

Reference as: Mosier JM, Stolz L, Bloom J, Malo J, Snyder L, Fiorello A, Adhikari S. Resuscitative EChocardiography for the Evaluation and management of Shock: The RECES protocol. Southwest J Pulm Crit Care. 2014;8(2):110-25. doi: http://dx.doi.org/10.13175/swjpcc177-13 PDF

Ultrasound for Critical Care Physicians: Hypotension

A 68 year old man is transferred to the intensive care unit because of hypotension. An ultrasound of the heart and inferior vena cava (IVC) were performed (Figure 1).

Figure 1. Upper panel: subxiphoid view of heart. Lower panel: inferior vena cava.

What is the cause of the hypotension? (Click on the correct answer)

1. Cardiogenic shock secondary to cardiomyopathy
2. Intracardiac thrombus
3. Intravascular volume depletion
4. Massive pulmonary embolism
5. Pericardial effusion

Reference as: Mosier JM. Ultrasound for critical care physicians: hypotension. Southwest J Pulm Crit Care. 2013;8(1):41-3. doi: http://dx.doi.org/10.13175/swjpcc176-13 PDF

Fat Embolism Syndrome: Improved Diagnosis Through the Use of Bedside Echocardiography

Douglas T. Summerfield, MD

Kelly Cawcutt, MD

Robert Van Demark, MD

Matthew J. Ritter, MD

Departments of Anesthesia and Pulmonary/Critical Care Medicine

Mayo Clinic

Rochester, MN

Case Report

A 77 year old female with a past medical history of dementia, chronic atrial fibrillation requiring anticoagulation, hypertension, biventricular congestive heart failure with a preserved left ventricular ejection fraction, pulmonary hypertension, and chronic obstructive pulmonary disease (COPD) presented to the emergency room after she sustained a ground level fall while sitting in a chair. The patient reportedly fell asleep while sitting at the kitchen table, and subsequently fell to her right side. According to witnesses, she did not strike her head, and there was no observed loss of consciousness. As part of her initial evaluation, at an outside hospital, radiographs of the pelvis, hip, and knee were obtained. These identified a definitive right superior pubic ramus fracture with inferior displacement and a questionable fracture of the right femoral neck. Shortly thereafter, the patient was transferred to our hospital for further management. On exam, the patient had a painful right hip limiting active motion and her right lower extremity was neurovascularly intact without paresthesias or dysesthesias. The remainder of the exam was unremarkable. In the emergency room, a repeat radiograph showed no evidence of a right femur fracture. Later in the evening a CT scan of the pelvis with intravenous contrast showed acute fractures through the right superior and inferior pubic rami with associated hematoma. Multiple tiny bony fragments were noted adjacent to the superior pubic ramus fracture (Figure 1).

Figure 1. CT scan demonstrating acute fractures through the superior and inferior pubic rami with associated hematoma. Multiple tiny bone fragments are adjacent to the superior pubic ramus fracture.

The CT did not show an apparent femur fracture. MRI of the pelvis and hip were ordered to assess for a femoral fracture; however this was not obtained secondary to patient confusion thus no quality diagnostic images were produced. The orthopedic service concluded that surgery was not required for the stable, type 1 lateral compression injury that resulted from the fall.

The patient was admitted to a general medicine floor for non-surgical management which included weight bearing as tolerated as well as therapy with physical medicine and rehabilitation. On admission, her vital signs were stable, including a heart rate of 89, blood pressure of 159/89, respirations of 20, with the exception of her peripheral oxygen saturation which was 89% on room air. Over the next several hospital days, she continued to have low oxygen saturations, began requiring fluid boluses to maintain an adequate mean arterial blood pressure (secondary to systolic blood pressure falling to the 70-80mmHg range intermittently) and she developed acute kidney injury with her creatinine increasing to 4.2 from her baseline of 1.1.  Nephrology was consulted to evaluate the acute kidney injury and their impression was acute renal failure secondary to contrast administration for the initial CT scan, in the setting of chronic spironolactone and furosemide use. The patient’s mental status remained altered, her speech although typically understandable was non-coherent, and she remained bed-bound. Due to her underlying dementia, her baseline mental status was difficult to determine and this combined with her opioids for pain control were felt to contribute to her mental status.

During her first dialysis session, the patient developed hypotension and hypoxemia which necessitated a rapid response call and transfer to the intensive care unit (ICU). The impression at the time of transfer to the ICU was septic shock with multi-organ dysfunction syndrome, presumably from a urinary source. The initial exam by the ICU team demonstrated what was thought to be considerable acute mental status change with agitation and moaning, hypotension, hypoxemia, and continued renal failure. Further review of her hospital course revealed that these changes had slowly been progressing since admission. Stabilization in the ICU included placement of a right internal jugular central venous catheter, blood pressure support with vasopressors, as well as intubation and high level of ventilatory support, including inhaled alprostadil, for severe hypoxemic respiratory failure. In addition, she was also placed on continuous renal replacement therapy.

In order to better assess the patient’s fluid status, the service fellow assessed the vena cava with the bedside ultrasound. While observing the collapsibility of the IVC, small hyperechoic spheres were observed traveling through the IVC proximally towards the right heart. A subcostal window focusing on the right ventricle demonstrated the same hyperechoic spheres whirling within the right ventricle. These same spheres were seen in both the four chamber view (Figure 2), as well as the short axis view and were present for several hours.

Figure 2. Four chambered view revealing right ventricular bowing as well as small hyperechoic spheres present in the right ventricle and atria.

Two hours later, a formal bedside echocardiogram was performed to evaluate the right heart structure and function. The estimated right ventricular systolic pressure was at 70 mm Hg, indicating severe pulmonary hypertension. The right ventricle was enlarged, and there was severe tricuspid regurgitation. Again there continued to be small hyperechoic spheres within her right ventricle as well as her right atria. Per the formal cardiologist reading, these were consistent with fat emboli. Further laboratory evaluation, including the presence of urinary fat, helped confirm the diagnosis of fat emboli syndrome.

Supportive care was continued, but without obvious improvement. After a family care conference, she was transitioned to palliative care and died.

Background

Fat emboli (FE) and fat emboli syndrome (FES) have been described clinically and pathologically since the 1860’s. Early work by Zenker in 1862 first described the pathologic significance of fat embolism with the link of fat to bone marrow release during fractures was discovered by Wagner in 1865. Despite the 150 years since its discovery, the diagnosis of Fat Embolism remains elusive. FE is quite common with the presence of intravascular pulmonary fat seen in greater than 90% of patients with skeletal trauma at autopsy (1). However, the presence of pulmonary fat alone does not necessarily mean the patient will develop FES. In a case series of 51 medical and surgical ICU patients, FE was identified in 28 (51%) of patients, none of whom had classic manifestations of FES (2).

The three major components of FES have classically consisted of the triad of petechial rash, progressive respiratory failure, and neurologic deterioration. The incidence following orthopedic procedures ranges from 0.25% to 35% (3). The wide variation of the reported incidence may in part be due to the fact that FES can affect almost every organ system and the classic symptoms are only present either transiently or in varying degrees, and may not manifest for 12-72 hours after the initial insult (4). The patient we present represents both the lack of the classic triad and the delayed onset of signs and symptoms, illustrating the elusiveness of the diagnosis.

Of the major clinical criteria, the cardio-pulmonary symptoms are the most clinically significant. Symptoms occur in up to 75% of patients with FES and range from mild hypoxemia to ARDS and/or acute cor pulmonale. The timing of symptoms may coincide with manipulation of a fracture, and there have been numerous reports of this occurring intraoperatively with direct visualization of fat emboli seen on trans-esophageal echo (TEE) (5-8).

The classic petechial rash, which was not noted in our patient, is typically seen on the upper anterior torso, oral mucosa, and conjunctiva. It is usually resolved within 24 hours and has been attributed to dermal vessel engorgement, endothelial fragility, and platelet damage all from the release of free fatty acids (9). The clinical manifestation of this “classic” finding varies widely and has been reported in 25-95% of the cases (4, 10).

Neurologic dysfunction can range from headache to seizure and coma and is thought to be secondary to cerebral edema due to multifactorial insults. These neurologic changes are seen in up to 86% of patients, and on MRI produce multiple small, non-confluent hyper intensities that appear within 30 minutes of injury. The number and size correlate to GCS, and subsequently reversal of the lesions is seen during neurologic recovery. (11,12).

Temporary CNS dysfunction usually occurs 24-72 hours after initial injury and acute loss of consciousness immediately post-operatively has been documented. Of note, this loss of consciousness may not be a catastrophic event. In a case report by Nandi et al., a patient with acute loss of consciousness made full neurologic recovery within four hours (13). In the retina, direct evidence of FE and FES manifests as cotton-wool spots and flame-like hemorrhages (1). However these findings are only detected in 50% of patient with FES (14)

FES also affects the hematological system, producing anemia and thrombocytopenia 37% and 67% of the time, respectively (15, 16). Thrombocytopenia is correlated to an increased A-a gradient, which Akhtar et al. noted that some clinicians include this finding in the criteria to diagnose FES (1).

Diagnosis

Given the broad and varying manifestations of FES, others have broadened the criteria. The Lindeque criteria require a femur fracture. The FES Index is a scoring system which includes vitals, radiographic findings, and blood gas results. Weisz and colleagues include laboratory values such as fat macroglobulenemia and serum lipid changes. Miller and colleagues (17) even proposed an autopsy diagnosis using histopathic samples. The most widely used criteria are set forth by Gurd and Wilson and require two out of three major criteria be met, or one major plus four out of five minor criteria. Major criteria include pulmonary symptoms, petechial rash, and neurological symptoms. Minor criteria include pyrexia, tachycardia, jaundice, platelet drop by >50%, elevated ESR, retinal changes, renal dysfunction, presence of urinary or sputum fat, and fat macroglobulinemia (1). Of note, none of the proposed diagnostic criteria include direct visualization of fat emboli via ultrasound or echocardiography (18-22) (Table 1).

Table 1: Gurd's Criteria for Diagnosis of FES

Gurd AR. Fat embolism: an aid to diagnosis. J Bone Joint Surg Br. 1970;52(4):732-7. [PubMed]

Mechanism

Two theories explain the systemic symptoms seen in FES. The mechanical theory describes how intramedullary free fat is released into the venous circulation directly from the fracture site or from increased intramedullary pressure during an orthopedic procedure. The basis for the theory is that the fat particles produce mechanical obstruction. However, not all fat emboli translocated into the circulation are harmful. It is estimated that fat particles larger than 8 μm embolize (23-25). As they accumulate in the lungs, aggregates larger than 20 μm occlude the pulmonary vasculature (26). Particles 7-10 μm particles can cross pulmonary capillary beds to affect the skin, brain, and kidneys. On a larger scale, the embolized free fatty acids produce ischemia and the subsequent release of inflammatory markers (27). The mechanism of this systemic spread beyond the pulmonary capillaries is not well understood. Patients without a patent foramen ovale or proven pulmonary shunt develop FES (28). Interestingly enough, other patients with a large fat emboli burden in the pulmonary microvasculature have not progressed to FES (29). One possible explanation for this may be elevated right-sided pressures force pulmonary fat into systemic circulation (1).

The biochemical theory has also been proposed to explain the systemic organ damage. The mechanism describes that enzymatic degradation of fat particles in the blood stream brings about the release of free fatty acids (FFA) (30, 31). FFA and the toxic intermediaries then cause direct injury on the lung and other organs. The fact that many of the symptoms are seen much later than the initial injury would support the Biochemical Theory. This theory also has an obstructive component to it as it recognizes that large fat particles coalesce to obstruct pulmonary capillary beds (11).

Discussion

Fat emboli syndrome is a rare and difficult clinical diagnosis. Currently there is no diagnostic test for FES and even the reported incidence is quite variable. The wide clinical presentation of FES makes the diagnosis challenge, and classic pulmonary involvement does not always occur (31). Furthermore, the symptoms overlap with other illness such as infection, as it did in this patient who was initially thought to be septic. The delayed onset of symptoms may further confound its identification. Finally, the traditional criteria used to diagnosis FES are variable depending on which source is referenced. Case-in-point is the Lindque criteria which require the presence of a femur fracture. By this requirement the patient presented in this case would not have been diagnosed with FES as she presented with a pelvic fracture.

The patient in this case was likely suffering from undiagnosed FES from the time of her admission. Since it did not present in the classic fashion, her progressive respiratory failure and neurologic deterioration were incorrectly attributed to congestive heart failure and opioid administration.

In this patient, the diagnosis of FE was somewhat unexpected, although it was within the differential. For this case the implementation of bedside ultrasound proved critical to the correct diagnosis and subsequent outcome. Instead of following other possible diagnoses and treatment options such as sepsis in this tachycardic, hypotensive patient, supportive care was employed with the diagnosis of fat embolism in mind.

The use of ultrasound imaging is not well studied for the diagnosis of FES, however it may provide an additional tool for making this difficult diagnosis when the classic triad of rash, cardiopulmonary symptoms, and neurologic changes is not seen or is in doubt. When used to evaluate for cardiogenic causes of acute hypotension, bedside cardiac ultrasound may reveal findings suggestive of FES, as it did in this case.

Review of the literature (5-8) confirms similar echogenic findings from fat emboli as seen by TEE intraoperatively during orthopedic procedures. However, similar spheres can be seen in a number of other instances. Infusion of blood products, such as packed red blood cells, may create similar acoustic images. No blood products had been given to the patient at the time of the bedside ultrasound. Additionally cardiologists have traditionally used agitated saline to look for patent foramen ovale. This and air embolism after placement of a central venous catheter can both produce similar images. In this case the emboli were seen traveling through the inferior vena cava, inferior and distal to the right side of the heart. The right internal jugular catheter would not have showered air emboli to that location, additionally once these were seen circulating in the right ventricle, the first action performed was to ensure all ports on the central line were secure. Given that these hyperechoic spheres were present for hours, air emboli would be less likely to be the underlying etiology. The images were later seen during the formal cardiac echo, and again validated by the cardiologist as being consistent with fat emboli.

To our knowledge this is the first case report of critical care bedside echocardiography (BE), assisting with the diagnosis of fat emboli syndrome. This is in contrast to TEE which has been used to diagnose FE and presumed FES in hemodynamically unstable patients in the operating room (5-8).

BE is attractive as it requires less training than TEE and can be repeated at the bedside as the clinical picture changes. By itself BE cannot differentiate FE from FES, but since the practitioner using it is presumably familiar with the patient’s condition, it can be used to augment the diagnosis when other findings are also suggestive of FE.

It has been suggested that a basic level of expertise in bedside echocardiography can be achieved by the non-cardiologist in as little as 12 hours of didactic and hands-on teaching. Given this amount of training, the novice ultrasonographer should be able to identify severe left or right ventricular failure, pericardial effusions, regional wall motion abnormalities, gross valvular abnormalities, and volume status by assessing the size and collapsibility of the inferior vena cava (32-37). Potentially, based on this case, the list could include FE with FES in the correct clinical context, pending further clinical validation.

In conclusion, this is the first reported case of bedside ultrasonography assisting in the diagnosis of FES in the ICU. The case illustrates the diagnostic challenge of FE and FES and also highlights the potential utility of bedside ultrasonography as a diagnostic tool.

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Reference as: Summerfield DT, Cawcutt K, Van Demark R, Ritter MJ. Fat embolism syndrome: improved diagnosis through the use of bedside echocardiography. Southwest J Pulm Crit Care. 2013;7(4):255-64. doi: http://dx.doi.org/10.13175/swjpcc109-13 PDF

Ultrasound for Critical Care Physicians: Sickle Cell Crisis

A 32 year old man was admitted a week earlier with sickle cell pain crisis. He had developed increasing dyspnea, oxygen desaturation and bilateral pulmonary infiltrates.  He had a pulseless electric activity code blue and an ultrasound of the heart was obtained (Figure 1).

Figure 1. Subxiphoid view ultrasound of the heart.

What does the ultrasound show?

1. Aortic dissection
2. Aortic stenosis
3. Enlarged left ventricle
4. Enlarged right ventricle
5. Pericardial effusion

Reference as: Raschke RA. Ultrasound for critical care physicians: sickle cell crisis. Southwest J Pulm Crit Care. 2013:7(2):110-1. doi: http://dx.doi.org/10.13175/swjpcc113-13 PDF