Show me the POCUS
POCUS in ACLS
Point of Care Ultrasound (POCUS) improves diagnostic accuracy and affect patient management in patients undergoing cardiac arrest. Resuscitation guidelines from the American Heart Association, the American Society of Echocardiography and the American College of Emergency Physicians as well as the European Resuscitation Council advocate POCUS use in cardiac arrest. The current recommendations is to use cardiac ultrasound if it can be performed without it interfering with standard advanced cardiovascular life support protocols. It use is as an additional diagnostic tool to identify potentially reversible causes.
POCUS is only recommended in PEA and asystolic rhythms and should not delay lifesaving treatment of ventricular arrhythmias. POCUS can 1. Identify organized cardiac contractility and help differentiate pulseless electrical activity (PEA) from pseudo-PEA; 2. It can also determine a cardiac cause of the arrest; 3. Guide lifesaving procedures at bedside. True PEA is defined as the clinical absence of ventricular contraction despite the presence of electrical activity, whereas pseudo-PEA is defined as the presence of ventricular contractility visualized on cardiac ultrasound in a patient without palpable pulses.
Multiple protocols have been designed with the intent of integrating POCUS into advanced cardiac life support (ACLS safely). However there is no single best approach is widely accepted as best practice. What is clear though is that time is of the essence in arrest cases and a clinician should avoid exceeding the 10 second pauses between chest compressions.
Regarding the use of POCUS to make prognostic implications. Operationally the idea is to either continue with resuscitation efforts with in patients with the possibility of survival or termination in futile cases. Based on a recent systemic review of POCUS during resuscitation of adults with a non-traumatic cardiac arrest, the evidence for it use to make prognostic implications is very low. POCUS should not be used for prognostication purposes. In short, it is acceptable to continue resuscitation efforts that end up proving futile than to erroneously terminate resuscitation in a patient who would have otherwise survived.
Hs and Ts
The reversible cause of cardiac arrest are recognized into the Mnemonic of Hs and Ts and for review here they are:
Hydrogen ion (acidosis)
Hypo/Hyperkalemia
Hypothermia
Toxins
Of the above conditions, we will be looking at those that can be seen on FoCUS and are highlighted in blue.
Clinical diagnosis of the following conditions are common in the perioperative period and have a temporal relation to an intervention and include: Anaphylaxis, Local Anesthetic Systemic Toxicity, Anesthetic Overdose, Auto-PEEP or Malignant hyperthermia.
No standardized protocol exists on the use of POCUS in cardiac arrest. However there are steps that we need to take in order to improve patient safety and optimize medical decision making and include the following:
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POCUS should only be used during rhythm check and should not interfere with CPR efforts
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Prepare the curvilinear or the phased array probe so that image acquisition lasts 10 seconds. Clips usually record 3 seconds of your scan.
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Appoint a 'Time Keeper' so that POCUS lasts less than 10 seconds.
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On pulse check ONLY acquire. Interpret images when chest compressions have resumed.
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During the time of chest compressions, the sonographer can look at extra cardiac images such as Lung/Abdomen/ Vascular.
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The sonographer should communicate results.
PEA vs Pseudo PEA
POCUS can assist in determining between these two possibilities in patients with suspected PEA on cardiac arrest. An estimated 80% of in-hospital cardiac arrests consist of non-shockable rhythms. The role of FoCUS here is to confirm rhythm classification. A true PEA is one in which electrical activity is not coupled with mechanical motion of the heart by either a palpable pulse or detectable contractility on ultrasound .
Pseudo PEA is mechanical contraction seen on POCUS that can include any of the following:
1. Ventricular Fibrillation with wide complex QRS seen on EKG and fast rhythmic heart movement in which case an unsynchronized shock is warranted
2. Supraventricular Tachycardia with narrow complex QRS coupled with fast rhythmic heart movement and in which a synchronized shock is warranted.
On the following clips we see PEA vs Pseudo PEA
Asystole/PEA
VT/VF/SVT depending on EKG
VT/VF/SVT depending on EKG
Hs : Hypoxemia
At this point in the ACLS algorithm you have addressed hypoxemia and have secured the patient's airway or are in the process of doing so. Severe hypoxemia leads to bradycardia and ultimately to PEA. FoCUS can help us determine if the cause of the arrest is associated with hypoxemia. Both cardiogenic and non cardiogenic pulmonary edema will present with diffuse B lines. Consolidations and atelectasis with or without large pleural effusions can also be seen on ultrasound. Gastric ultrasound can also assist you in determining if there was a significant risk for aspiration, specially if gastric contents were seen in the airway on intubation.
Lung POCUS can assist you in determining the cause of the hypoxemia as seen below.
Consolidation
Pulmonary Edema
Pleural Effusion
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Gastric POCUS can assist you in determining if there was an increased aspiration risk specially if food contents were seen on intubation.
Grade 2 Antrum with clear contents
Full stomach
Full stomach
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Hs : Hypovolemia
Signs of hypovolemia include a small ventricular chamber size and a collapsed inferior vena cava. You may not see a collapsed ventricles. Should hypovolemia be on the differential the interrogation should proceed with the focused assessment with sonography for trauma to identify free fluid or other acute pathology that may necessitate thoracotomy or laparotomy.
Ts: Cardiac Tamponade
The clinician should have a high index of suspicion the expected signs of tamponade are absent. These include pulsus paradoxus or jugular vein distention since they are obscured during cardiac arrest. To make matters complicated the ultrasound findings associated with tamponade are only present when there is preserved cardiac activity. These include hyperdynamic left ventricle and diastolic collapse of the RV as well as paradoxical septal shift during spontaneous inspiration. Thus presence of pericardial effusion should prompt consideration for tamponade as the precipitating cause. Multiple views are needed to rule out a pericardial effusion since even a focal clot can lead to tamponade physiology.
Ts: Tension Pneumothorax
Tension pneumothorax is defined as air trapped in the pleural space under positive pressure, displacing mediastinal structures and resulting in decreased cardiac output. Lung ultrasound has exceptional specificity for pneumothorax (98.4%) when you can visualize lung point which implies it can be used to rule it in. Visualization of lung sliding, B lines or lung pulse rules out this possibility as the cause of cardiac arrest. In other situations you will be somewhere in the middle, that is you cannot rule it out or rule it in. This is because you will visualize isolated A lines with no lung sliding. A presumptive diagnosis of pneumothorax is thus made specially if there is a temporal relation to a precipitating event: invasive procedure near the pleura or trauma to the chest. The chest compressions in CPR can cause a pneumothorax themselves.
Ts: Thrombosis, Coronary
Visualizing severe left or right ventricular hypokinesis raises the concern for coronary thrombosis on the differential. Accurate identification of regional wall motion abnormalities is beyond the scope of FoCUS. However myocardial ischemia is frequently associated ventricular tachycardia or fibrillation which implies that on this setting this is a cause of pseudo PEA.
Ts: Thrombosis, Pulmonary
Pulmonary embolism is a common cause of PEA. FoCUS rarely leads to confirmatory findings including a clot-in-transit or McConnell's sign. Right ventricular dilation and dysfunction are highly non-sensitive (56% when used in combination). This implies that their absence does not imply there is no pulmonary embolism thus it cannot be ruled out according to the American Society of Echocardiography based on this finding alone.
In the presence of right ventricular (RV) failure the lower extremities can be assessed for the presence of clot. The presence of deep vein thrombosis (DVT) should warrant a discussion on empiric anticoagulation or thrombolytic therapy. Absence of DVT should prompt consideration for other causes of RV failure. Consideration of pulmonary hypertensive crisis should be considered when chronic RV changes are seen including a thick free wall RV and a large RA.
POSSIBLE PULMONARY EMBOLISM
The following clips are specific for PE and include Clot-in-transit, McConnell's sign and paradoxical septal motion. Their absence does NOT exclude PE on your differential.
Also seen here is a positive DVT exam on lower extremities increases your post test probability of PE.
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References
1. Jonathan A. Paul, Oliver P. F. Panzer; Point-of-care Ultrasound in Cardiac Arrest. Anesthesiology 2021; 135:508–519 doi: https://doi.org/10.1097/ALN.0000000000003811
2. Merchant R and all. Part 1: Executive Summary: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Circulation. 2020;142:S337–S357. https://doi.org/10.1161/CIR.0000000000000918
3. Berg KM and all. Adult Advanced Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation. 2020;142:S92–S139. https://doi.org/10.1161/CIR.0000000000000893
4. Labovitz AJ, Noble VE, Bierig M, Goldstein SA, Jones R, Kort S, Porter TR, Spencer KT, Tayal VS, Wei K: Focused cardiac ultrasound in the emergent setting: A consensus statement of the American Society of Echocardiography and American College of Emergency Physicians. J Am Soc Echocardiogr. 2010; 23:1225–30