Addition of tramadol to anticholinergic premedication for the prophylaxis of post-anaesthetic shivering

Abstract

Anticholinergic agents can increase the incidence and severity of post-anaesthetic shivering [1]. Tramadol is very effective in the treatment of shivering [2]. The aim of this randomized, double-blind, placebo-controlled study was to assess the effects of the addition of tramadol to glycopyrronium administered pre-operatively on post-anaesthetic shivering. After institutional approval, informed consent was obtained from 36 adult female outpatients, ASA grade I or II, who presented for gynaecological laparoscopic surgery of about one hour duration. None were obese, febrile or taking vasoactive, antidepressant or analgesic drugs, or had a history of cardiovascular, respiratory, endocrine or neurological disease. One hour before surgery patients were given (i.m.) either saline, or glycopyrronium 5 μg kg−1 (max 400 μg), or tramadol 1.5 mg kg−1 + glycopyrronium 5 μg kg−1. General anaesthesia was induced with fentanyl 1.5 μg kg−1, propofol 1.5-2.5 mg kg−1 and atracurium 0.25 mg kg−1 and maintained with 66% N2O in O2 and isoflurane ≥1.2 MAC unless blood pressure decreased by more than 20%. An oesophageal thermistor probe (MC 9200 Exacon®) introduced 25 cm below the corniculate cartilages was used for continuous measurement of central temperature. Neuromuscular blockade was allowed to wear off without pharmacological reversal whenever possible. In the recovery room, patients received O2 and a cotton blanket. Shivering was graded as in table 14. Data were analysed using ANOVA, Chi-square and Kruskall-Wallis one-way ANOVA.Table 14: (abstract 54). Classification of shivering Four patients were excluded retrospectively due to incorrect premedication or pharmacological reversal of neuromuscular blockade. The three groups were similar with respect to demographic and anaesthetic data, presented as mean ± SD (table 15). No patients in the tramadol group shivered early in the recovery unit, compared with six patients in the saline group and eight patients in the glycopyrronium group (Kruskall-Wallis, P=0.005). However, three patients in the tramadol group and two patients in the saline group shivered later.Table 15: (abstract 54) Patient characteristics and study observations Pre-operative administration of tramadol caused a significant decrease in the incidence of post-anaesthetic shivering. Further studies are required to investigate the mechanism of these effects and to evaluate the peri-operative use of tramadol in anaesthetic practice.