• Joel Parlow, Ian Gilron, Brian Milne, Deborah Dumerton-Shore, Elizabeth Orr, and Rachel Phelan.
• Department of Anesthesiology & Perioperative Medicine, Queen's University & Kingston General Hospital, 76 Stuart Street, Kingston, Ontario, Canada. parlowj@queensu.ca
• Can J Anaesth. 2010 Apr 1; 57 (4): 337-42.

PurposeDrug effects can be unpredictable during cardiac surgery due to factors that may influence drug concentration, such as extracorporeal oxygenation and hemodilution. The primary aim of the current investigation was to determine whether plasma gabapentin concentration is altered by cardiopulmonary bypass (CPB).MethodsFollowing approval from the Research Ethics Board and written informed consent, we conducted this open-label prospective cohort investigation. A convenience sample of 16 patients, who were scheduled for coronary bypass surgery, received oral gabapentin 600 mg as follows: 90 min prior to induction of anesthesia, following tracheal extubation, and then every eight hours for a total of four doses. Plasma gabapentin concentration, as well as pain and sedation scores, were documented.ResultsPlasma gabapentin concentrations were unaltered during CPB (31.9 +/- 12.7 mumol.L(-1) prior to CPB, 35.6 +/- 12.9 to 37.2 +/- 9.6 mumol.L(-1) during CPB). However, using the current protocol, drug accumulation (reflected by increased drug concentrations) was observed following the third (58.2 +/- 19.5 micromol.L(-1)) and the fourth (71.9 +/- 34.3 micromol.L(-1)) doses. Pain and sedation scores and opioid requirements were comparable with those found in other studies.ConclusionPlasma gabapentin concentration is unaltered during CPB following preoperative administration. Drug accumulation following third and fourth postoperative doses suggests the need for therapeutic drug monitoring in future trials. Gabapentin is well established as an effective adjunct analgesic in a number of surgical settings. Randomized controlled trials are necessary to evaluate analgesic efficacy, optimal dosing, and adverse effects in the setting of cardiac surgery.

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