Intracranial Pressure Changes during Rapid Sequence Intubation: A Swine Model

Abstract

Controversy and speculation exist regarding intracranial pressure (ICP) changes produced by various combinations of rapid sequence intubation (RSI) agents. In this pilot study, we sought to develop a swine model to investigate these changes in classic RSI. Eight adult swine were instrumented with arterial and intracranial pressure monitors. Four different versions of rapid sequence intubation were then performed sequentially in each animal in a crossover trial design: regimen 1, thiopental; regimen 2, thiopental and succinylcholine; regimen 3, lidocaine, thiopental, and succinylcholine; and regimen 4, pancuronium, lidocaine, thiopental, and succinylcholine. ICP and hemodynamic parameters were recorded and compared. Trials were excluded from analysis if baseline ICP measurements were unstable or if intubation was difficult. Peak changes in ICP were noted at 2 to 3 minutes after administration of induction agents. Mean values for peak changes in ICP were as follows: regimen 1 (n = 5), 3.6 mm Hg (95% confidence interval [CI], 1.0-6.2 mm Hg); regimen 2 (n = 9), 13.6 mm Hg (95% CI, 9.6-17.6 mm Hg); regimen 3 (n = 2), 16.0 mm Hg (95% CI, -34.8-66.8 mm Hg); and regimen 4 (n = 3), 12.0 mm Hg (95% CI, -8.3-32.3 mm Hg). The model is effective. It enables investigators to examine the aggregate ICP effects of combinations of RSI medications. RSI regimens with paralysis produced threefold increases in peak ICP change compared with the sedation-only regimen. Pretreatment agents did not affect ICP changes. Future investigations can examine other agents and add experimental manipulation of ICP to simulate head injury physiology. Additional parameters including cerebral metabolism and/or oxygenation may also be explored.