Effect of discontinuing a constant rate intravenous infusion of lidocaine on recovery from general anesthesia with isoflurane in horses: A randomized clinical trial

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Objective To evaluate the effect of discontinuing intravenous (IV) lidocaine infusions 30 minutes before the end of inhalational anesthesia on recovery from general anesthesia in horses. Study Design Randomized controlled clinical study. Animals Forty healthy adult horses undergoing general anesthesia for magnetic resonance imaging. Methods All horses underwent a standard anesthetic protocol. Lidocaine was injected IV as a loading dose (2 mg kg -1 ), followed by a continuous rate IV infusion of 3 mg kg -1 hour -1 . Horses were randomly allocated to one of two groups: discontinuation of the infusion 30 minutes before the end of anesthesia (Group DC, n = 20), or continuation until the end of anesthesia (Group C, n = 20). A 3-axis accelerometer was secured around the withers to obtain accelerometry-based recovery scores (RS). Lower scores correlate with higher quality recovery and higher scores correlate with lower quality recovery. Recorded variables included time to first movement, time to sternal recumbency, time to standing, and number of standing attempts. RS (mean ± standard deviation) was analyzed using a Student's t-test. Significance was set at p < 0.05. Results Mean RS were 22 ± 7 and 25 ± 8 for Groups C and DC, respectively ( p = 0.175). Median times to first movement, sternal recumbency, and standing were 43 (21–69), 56 (29–90), and 61 (29–111) minutes for group C, and 33 (21–69), 45 (26–97), and 50 (36–97) minutes for group DC, respectively. The median number of stand attempts was 1 (1–5) for both groups. Conclusions and Clinical Relevance Discontinuing lidocaine infusions 30 minutes before the end of inhalational anesthesia did not improve recovery quality compared to infusions continued until the end. These findings do not support a benefit of early lidocaine discontinuation in this context.