Postoperative nausea and vomiting: incidence, characteristics and risk factors--a prospective cohort study

Abstract

Background: Postoperative nausea and vomiting are a common complication after surgery. The objective of the study was to identify risk factors, and to determine the incidence of postoperative nausea and vomiting in a cohort of patients in a tertiary university hospital.

Methods: Prospective cohort study was conducted in a Post Anesthetic Care Unit during a period of 3 weeks. One hundred and fifty-seven adult patients subjected to scheduled non-cardiac and non-intracranial surgery were eligible for the study. Patient perioperative characteristics data were analyzed. The postoperative nausea and vomiting intensity scale and nausea visual analog scale were applied to measure postoperative nausea and vomiting at 6h and 24h after surgery. Descriptive analysis was performed and the Mann-Whitney U, Fisher's exact, or Chi-square tests were applied. A univariate and multivariate logistic binary regressions with calculation of odds ratio (OR) and its 95% confidence interval (95% CI) were performed.

Results: Thirty-nine (25%) patients and 54 (34%) patients had postoperative nausea and vomiting at 6h and 24h, respectively. Of the patients who experienced postoperative nausea and vomiting, 6 (15%) had clinically significant postoperative nausea and vomiting (postoperative nausea and vomiting intensity scale>50) at 6h and 9 (23%) at 24h. The majority of patients classified nausea as mild at 6h (57%) and 24h (56%). At 6h, 3 (10%) patients classified nausea as severe, and at 24h 5 (9%) patients reported the same. The median and interquartile ranges for nausea visual analog scale were 40 (20-60) at 6h and 50 (20-60) at 24h. Six patients (14%) at 6h, and 7 (18%) at 24h had a nausea visual analog scale score>75. Patients with postoperative nausea and vomiting intensity scale>50 had higher scores in the nausea visual analog scale at 6h (75 versus 30, P<.05) and 24h (70 versus 40, P<.05). The univariate analysis identified risk factors for postoperative nausea and vomiting: Apfel score>2 (OR 3.2, 95% CI 1.6-6.4, P=.001), previous history of postoperative nausea and vomiting (OR 2.9 95% CI 1.3-6.5, P=.009) and female patients (OR 2.7, 95% CI 1.4-5.4, P=.005). In the multivariate analysis previous history of postoperative nausea and vomiting (adjusted OR 2.5, 95% CI 1.1-5.7, P=.030) and female gender (adjusted OR 2.4, 95% CI 1.2-4.9, P=.015) were considered as independent risk factors for postoperative nausea and vomiting.

Conclusion: Most of the patients do not have clinically significant postoperative nausea and vomiting. The patients who presented with postoperative nausea and vomiting intensity scale>50 had higher scores in the nausea visual analog scale. Independent risk factors for postoperative nausea and vomiting were previous history of postoperative nausea and vomiting and being female.