Shock Index as a Predictor of Post-Intubation Hypotension and Cardiac Arrest; A Review of the Current Evidence

Endotracheal intubation is a lifesaving procedure that is performed in various settings within the hospital or even in the pre-hospital field. However, it can result in serious hemodynamic complications, such as post-intubation hypotension (PIH) and cardiac arrest. The most promising predictor of such complications is the shock index (SI), which holds great prognostic value for multiple disorders. On the other hand, most of the studies that have assessed the predictability of the pre-intubation SI have been small and were limited to a particular setting of a single center; thus, the results were not generalizable, and the predictive value vary according to the setting. This review comprehensively assessed the utility of the pre-intubation SI for predicting PIH and post-intubation cardiac arrest by classifying and comparing evidence compiled from various settings, such as pre-hospital settings, emergency departments (EDs), intensive care units (ICUs), and operating rooms (ORs). The vast majority of these studies, conducted in ED and ICU settings, which revealed a significant correlation between an elevated SI and PIH or post-intubation cardiac arrest. The reliability and simplicity of obtaining a pre-intubation SI value are important considerations that encourage the extension of its use to all in-hospital intubations. Further studies are required to assess the predictive value of the SI in the pre-hospital setting.