Robert Cameron Sooby, DO| EM PGY3

The Article:

Accuracy of early rapid ultrasound in shock (RUSH) examination performed by emergency physician for diagnosis of shock etiology in critically ill patients. Ghane et al. (2015). Journal of Emergencies, Trauma, and Shock. 8(1): 5–10.

The Idea:

To determine the accuracy of early RUSH examination in predicting shock type in critically ill patients, and thus allowing for earlier identification of shock etiology and initiation of shock-specific treatments.

The Study:

This was a prospective study performed between April 2013 and October 2013. A total of 52 patients in shock state (defined as SBP < 100 or shock index (HR/SBP) > 1) were enrolled. Excluded were patients with a clear cause for shock (external hemorrhage, active GI bleeding, etc.). Early bedside RUSH was performed on all patients by a single board-certified ED physician, and all patients received standard of care without delay. All patients were followed to document their final diagnosis. Of note, subsequent physicians were not blinded to results of RUSH examination. A one-page checklist was designed incorporating the main components of the RUSH exam, which included evaluation of heart, IVC, thoracic and abdominal compartments, and large vessels. Five subtypes were defined for shock: hypovolemic, distributive, cardiogenic, obstructive and mixed shock. Agreement (Kappa index) of initial impression provided by RUSH with final diagnosis, and also sensitivity, specificity, PPV, and NPV of RUSH for diagnosis of each shock type were calculated.

The Findings:

The mean duration for exam (patient's arrival till RUSH conclusion) was 20 minutes (range, 10-25 minutes). The most frequent types of shock were cardiogenic shock (12 patients, 23.1%) and mixed shock (10 patients, 19.2%). Eight patients had hypovolemic, eight distributive, and seven obstructive type of shock. Seven cases (13.5%) died before the precise cause of shock could be determined and was classified as “not defined etiology”. Kappa index for general agreement between shock type using RUSH protocol and final diagnosis was 0.70 (P value = 0.000), reflecting acceptable general agreement. For hypovolemic shock, RUSH showed excellent sensitivity and good specificity (100% and 94.6%, respectively). NPV and PPV were 94.6% and 80%, respectively. In hypovolemic patients, RUSH protocol showed 86% agreement with final diagnosis (P value < 0.001). For cardiogenic shock, RUSH showed good sensitivity (91.7%) and specificity (97.0%). RUSH showed 89% agreement (P value < 0.001) with final diagnosis. PPV and NPV were 91.7 and 97.0%, respectively. For obstructive shock, RUSH showed excellent sensitivity (100%) and good specificity (97.0%). It had the largest agreement with final diagnosis (92%, P value < 0.001). PPV and NPV were 87.5% and 100%, respectively. For distributive shock, RUSH had excellent specificity (100%) but low sensitivity (75%). It had an acceptable agreement with final diagnosis (83%, P value < 0.001). PPV and NPV were 100% and 94.9%, respectively. For mixed etiology shock, RUSH had excellent specificity (100%) but had the lowest sensitivity (70%). It also had the lowest agreement (74%, P value < 0.001) with final diagnosis. PPV and NPV were 100% and 92.1%, respectively.

The Takeaway:

When performed by experienced clinicians, RUSH can rapidly and accurately diagnose shock type in the undifferentiated hypotensive patient. This in turn allows the clinician to initiate goal-directed therapies earlier and with greater confidence. Due to its inherently dynamic physiologic nature, RUSH was less sensitive in diagnosing distributive shock. Further studies utilizing more physicians and a larger sample size will need to be conducted to assess the shortcomings of this particular study.