UMEM Educational Pearls

Title: Predicting Hemodynamic Response to Ketamine for Prehospital RSI

Category: Pharmacology & Therapeutics

Keywords: ketamine, shock index, hemodynamic, prehospital, RSI (PubMed Search)

Posted: 5/3/2016 by Bryan Hayes, PharmD (Updated: 5/7/2016)
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Ketamine is often thought to be the induction agent least associated with hypotension in the peri-intubation period. However, reports of hypotension following ketamine do exist, including 2 cases of cardiac arrest. [1] There are limited objective means to predict which patients may have an adverse hemodynamic response.

New Study

A new prospective observational study followed 112 patients in the prehospital setting who received ketamine for rapid sequence intubation. 81 had a low shock index [< 0.9], 31 had a high shock index. [2]

Shock index = HR / SBP

What They Found

Patients with a high shock index were more likely to experience hypotension (SBP < 90 mm Hg) in the peri-intubation period compared to those with a low shock index (26% vs 2%).

Application to Clinical Practice

This is the first study to evaluate a potential objective predictor for which patients may experience hypotension after RSI with ketamine. But, even with a high shock index, the majority of patients did not develop hypotension.
These findings should not lead to avoidance of ketamine in these situations, as other induction agents are equally or more likely to cause adverse hemodynamic effects.
It has been suggested to use lower induction doses in patients at risk for hypotension (with the same or higher paralytic dose). Patients with a high pre-RSI shock index may be the population in which to consider that approach.

References

Dewhirst E, et al. Cardiac arrest following ketamine administration for rapid sequence intubation. J Intensive Care Med 2013;28(6):375-9. [PMID 22644454]
Miller M, et al. Hemodynamic response after rapid sequence intubation with ketamine in out-of-hospital patients at risk of shock as defined by the shock index. Ann Emerg Med. 2016 Apr 26. Epub ahead of print. [PMID 27130803]

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