Abstracts of Posters; Presented at the International Anesthesia Research Society; 73rd Clinical and Scientific Congress; Los Angeles, CA; March 12-16, 1999: Ambulatory Anesthesia
INTRODUCTION: Multiple factors are thought to influence postoperative nausea and vomiting (PONV), however, the role of smoking has rarely been mentioned [1,2]. Therefore, based on data of a controlled study, we investigated the interaction of smoking and the duration of anesthesia on postoperative vomiting (PV).
METHODS: With approval of the local ethics committee and written informed consent 500 adult patients undergoing elective ENT- or eye-surgery were included in a study stratified for opioids, volatile anesthetics and prophylactic antiemetics. According to the randomization code patients received either low dose or no adjuvant opioid before induction with thiopentone. General anesthesia was maintained with either isoflurane, enflurane or sevoflurane in O2/N2 O 1:2. Prophylactic antiemetic treatment (2.5 mg droperidol, 62 mg dimenhydrinate, 2.5 mg tropisetrone, 50 mg metoclopramide or placebo) was given in a double-blind fashion. The influence of duration of anesthesia among smokers and nonsmokers on PV was analysed using the chi-square test (two-sided) and logistic regression analysis to evaluate the relative impact of smoking compared to the other risk factors.
RESULTS: Due to the randomization of the study smokers (n = 174) and nonsmokers (n = 326) were similar in all anesthetic, surgical and demographic data (all p>0.05). Logistic regression analysis revealed that among other risk factors (previous PV, motion sickness, sex and antiemetics) the duration of anesthesia (p<0.01) and its interaction with smoking (p<0i.03) significantly influenced the incidence of PV (28% among smokers in comparison to 53% among nonsmokers after 120 min) (Figure 1).
DISCUSSION: The data suggest that the effect of smoking on postoperative vomiting is more apparent after long operations and should therefore be considered in future antiemetic trials.
1. Anesth Analg 78: 7-16, 1994
2. Anesthesiology 87 (Suppl): 25, 1997