Single-Dose Gabapentin Does Not Augment Postoperative Analgesia in Ambulatory Arthroscopic Shoulder Surgery

Abstract

In Response: We appreciate this opportunity to respond to Drs. Clendenen and Harrisson (1) who raise several questions regarding our article (2). Concerning their first point, there was a minimum of 2 h between gabapentin administration and interscalene brachial plexus block (respectively 150 ± 28 min in the placebo group and 146 ± 25 min in the gabapentin group). The interval between gabapentin administration and first patient assessment in the PACU was 290 ± 34 min in the placebo group and 286 ± 45 min in the gabapentin group (approximately 5 h). The first assessment was thus when gabapentin was well absorbed and remained at high concentration in the plasma. When our study began in September 2003, published studies usually used 1200 mg of gabapentin. However, this dose is frequently associated with side effects, especially somnolence and dizziness. We thus judged 1200 mg to be excessive for patients undergoing outpatient surgery and empirically selected 800 mg as an appropriate trade-off between toxicity and potential benefit. Presumably, a larger dose would increase potential benefit, but surely at the cost of increasing (and probably unacceptable) toxicity. Seven patients were excluded from the study because they required morphine in the PACU. Six patients received 3 mg of morphine, and one received 6 mg. Such small amounts that were required suggests a partial block, rather than a failure block. In our institute, usually we use a bolus of 20 mL of ropivacaine 0.5% for arthroscopic procedures when interscalene block is combined with general anesthesia. It is not exceptional that patients complain about a pain behind the shoulder. We believe that this pain results from incomplete block of suprascapular nerve. After receiving morphine these seven patients behaved exactly like the others. While we excluded these patients to maintain scientific rigor, the results would have been virtually identical had their results remained in the analysis. Frédéric Adam, MD Daniel I. Sessler, MD Marcel Chauvin, MD Département d'Anesthésie-Réanimation Hôpital Ambroise Paré AP-HP, 9 Avenue Charles de Gaulle Boulogne, Billancourt, France [email protected]