Background: Post-operative nausea and vomiting (PONV) is believed and previously reported to be influenced by the weather and the phase of the moon. We therefore determined the effects of specific and general weather patterns as well as the lunar phase on PONV in adults undergoing balanced inhalation anaesthesia.
Methods: The incidence of PONV was prospectively evaluated in 1801 patients undergoing elective surgical, urologic and head and neck procedures. Air temperature, barometric pressure, air water vapour pressure and the general weather situation were obtained from the National Weather Institute in Germany on the days of surgery. Corresponding categories of temperature, pressure, vapour pressure and their day-to-day changes, the general weather situation and the phase of the moon were used to group the patient data. The differences between the proportion of patients having PONV and the proportion predicted to have PONV according to their calculated risk were determined for each category. Further, bivariate and multivariate testing was applied.
Results: Within 24 h after anaesthesia, PONV occurred in 555 of the patients (31%). There was no correlation between weather conditions and PONV occurrence or between the phase of the moon and PONV occurrence. Even when corrected for the patients' risk and other potentially confounding factors in multivariate logistic regression analysis, no statistically significant impact of the hypothesized factors could be detected.
Conclusion: These data suggest that neither the weather nor the phases of the moon have any clinically relevant effect on the incidence of PONV after general anaesthesia.