What did they do?

Using a randmoized, double-blind crossover study, Fong et al anaesthetized eight male volunteers twice with 1.2% isoflurane for 1 hour, after propofol induction. In the final 10 minutes subjects were randomized to IV caffeine or placebo. No opioids were administered.

Receiving IV caffeine hastened emergence by over 40%, as measured by BIS and psychomotor testing.

Return of gag reflex was used as the marker of emergence, although time to emergence was consistent with eye opening and BIS.

How much caffeine did they give?!?

15 mg/kg of caffeine citrate, equivalent to 7.5 mg/kg of base caffeine – the same caffeine as in two large cups of coffee for a 70 kg male.

Come on, surely this isn't that important?

Although the mean 7 min difference may not appear clinically significant, especially when using more modern volatiles, this study is a good proof of concept of how caffeine may be a useful clinical tool when faced with delayed emergence after anesthesia and for patients at greatest risk of persistent psychomotor depression post-anesthesia, such as the elderly.

summary

• Robert Fong, Lingzhi Wang, James P Zacny, Suhail Khokhar, Jeffrey L Apfelbaum, Aaron P Fox, and Zheng Xie.
• From the Departments of Anesthesia and Critical Care (R.F., L.W., J.P.Z., S.K., J.L.A., Z.X.) Neurobiology (A.P.F.), University of Chicago, Chicago, Illinois the Department of Anesthesia, Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, China (L.W.) the Cancer Center (J.P.Z.) the College of Medicine (S.K.), University of Illinois at Chicago, College of Medicine, Chicago, Illinois.
• Anesthesiology. 2018 Nov 1; 129 (5): 912-920.

What We Already Know About This TopicWHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: There are currently no drugs clinically available to reverse general anesthesia. We previously reported that caffeine is able to accelerate emergence from anesthesia in rodents. This study was carried out to test the hypothesis that caffeine accelerates emergence from anesthesia in humans.MethodsWe conducted a single-center, randomized, double-blind crossover study with eight healthy males. Each subject was anesthetized twice with 1.2% isoflurane for 1 h. During the final 10 min of each session, participants received an IV infusion of either caffeine citrate (15 mg/kg, equivalent to 7.5 mg/kg of caffeine base) or saline placebo. The primary outcome was the average difference in time to emergence after isoflurane discontinuation between caffeine and saline sessions. Secondary outcomes included the end-tidal isoflurane concentration at emergence, vital signs, and Bispectral Index values measured throughout anesthesia and emergence. Additional endpoints related to data gathered from postanesthesia psychomotor testing.ResultsAll randomized participants were included in the analysis. The mean time to emergence with saline was 16.5 ± 3.9 (SD) min compared to 9.6 ± 5.1 (SD) min with caffeine (P = 0.002), a difference of 6.9 min (99% CI, 1.8 to 12), a 42% reduction. Participants emerged at a higher expired isoflurane concentration, manifested more rapid return to baseline Bispectral Index values, and were able to participate in psychomotor testing sooner when receiving caffeine. There were no statistically significant differences in vital signs with caffeine administration and caffeine-related adverse events.ConclusionsIntravenous caffeine is able to accelerate emergence from isoflurane anesthesia in healthy males without any apparent adverse effects.

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