Whats new in emergencies, trauma and shock? Shock, Sonography and survival in emergency care!

The presence of hypotension or shock in the setting of acute illness is associated with high mortality rates. Early assessment for the etiology of shock and prompt treatment have been shown to have a profound effect on the disease outcome;[12] however, clinical evaluation has certain limitations. Shock has been categorized into four classic subtypes.[3] These include:

Hypovolemic shock e.g., massive hemorrhage, gastrointestinal (GI) losses;

Distributive shock e.g., anaphylactic shock, neurogenic shock;

Cardiogenic shock, due to pump failure, e.g., myocardial infarction, advanced cardiomyopathy; and

Obstructive shock e.g., cardiac tamponade, tension pneumothorax, massive pulmonary embolism.

At the bedside, it is often difficult to accurately categorize the patient's clinical condition into one of the subtypes of shock and the physical findings may overlap. In addition, it is not easy to perform Swan-Ganz catheterization in hypotensive patients for rapid assessment of intravascular hemodynamic status.

Because of the noninvasive nature of ultrasound and the feasibility to perform repeated quick assessment in sick patients, this modality has become the frontline diagnostic tool for emergency care. In critically ill-patients with multiple injuries, focused assessment using sonography for trauma (FAST) has now become the standard of care; however, use of ultrasound for evaluation of medical patients with shock is not being routinely used in clinical practice. Since the turn of the century, there have been several attempts at using this diagnostic modality for evaluation of patients with hypotension and shock. Rose et al. described the role of ultrasound approach for empiric evaluation of the undifferentiated hypotensive patients (UHP protocol).[4] Early goal-directed ultrasound for emergency department (ED) patients with hypotension have been shown to decrease the time to the final diagnosis.[5] Since bedside ultrasound and echocardiography are becoming and integral component of emergency medicine, several other protocols have been developed during the last few years for evaluation of patients with shock, poly-trauma, sepsis, respiratory, distress, and cardiac arrest. Some of these include: TRINITY,[6] Extended-FAST,[7] FATE,[8] BLEEP,[9] FEER,[10] BEAT,[11] The Rapid Ultrasound for SHock (RUSH) HI-MAP,[12] ACES,[13] Boyd Echo,[14] FEEL-Resuscitation,[15] Elmer/Noble Protocol,[16] EGLS,[17] FREE,[18] FALLS,[19] POCUS-Fast and Reliable[20] and RUSH-Pump/Tank/Pipes.[2021] Some of the protocols such as BLUE[22] and RADIUS[23] have been devised for the assessment of dyspnea. Use of sonography has been shown to help stabilize patients in the ED[24] and also in management of patients with primary non-arrhythmogenic cardiac arrest.[25]

In order to amalgamate different components of ultrasonic evaluation of various organs for quick diagnosis of underlying cause of shock, Weingart et al.[12] developed RUSH protocol in a rapid, standardized sequence. The RUSH protocol aims at early integration of bedside ultrasound into clinical assessment for rapid and accurate diagnosis of shock in the ED. The RUSH protocol involves a three-stage bed-side assessment of various physiological components simplified as: Step 1 – The pump (cardiac evaluation), Step 2 – The tank (volume status), Step 3 – The pipes (vascular system). The entire examination can be completed in less than 2 min by using standard portable ultrasound machines. It is recommended to use a phased-array transducer (3.5-MHz) to allow adequate thoracoabdominal intercostal scanning, and a linear array transducer (7.5-10 MHz) for the required venous examinations and for the assessment of pneumothorax. The procedure should be done in a sequence in the order of the HI-MAP acronym: Heart, Inferior Vena Cava, Morrison's and FAST abdominal views, Aorta and Pneumothorax. Using the HI-MAP sequence for evaluation, we can recognize the cause of shock in majority of the cases and institute appropriate treatment promptly.

It may appear that there are multiple protocols for assessment of various physiological functions in patients with shock; however, careful examination of these would reveal common features in most of these protocols. In most cases, it is advisable for the clinicians to start with the evaluation of the heart and inferior vena cava and other components may be added, as required. Further, it may be pointed out that in a given case, based on the clinical scenario, it may not be mandatory to go through the entire protocol and the physician may tailor the assessment to conduct more focused evaluation.

Ghane et al. have assessed the accuracy of RUSH protocol in categorizing the type of shock. The predictability was determined using sensitivity, specificity, positive and negative predictive value and kappa index. It was seen that RUSH protocol had high sensitivity in determining hypovolemic, cardiogenic and obstructive shock and high specificity in determining hypovolemic, cardiogenic, obstructive and mixed etiology shock. The authors have also tried to highlight the importance of using the RUSH protocol as an additional tool to the clinical picture of the patient. Future studies focusing on the strength of associations between various components of the RUSH protocol with possibly larger sample size will help in improving the RUSH protocol from where it stands today.