[Impact of environmental factors on the incidence of posteropative nausea and vomiting. Influence of the weather and cycle of the moon].

OBJECTIVE

In a survey concerning postoperative nausea and vomiting an unexpected high number of the participants stressed the impact of environmental factors, like weather and--even more surprising--the phase of the moon, on the occurrence of postoperative nausea and vomiting (PONV). Thus, the aim of this study was to determine the influence of these factors on the incidence of PONV.

METHODS

On 203 days within the 19-month study period, 2488 patients were followed up for at least 24 hours postoperatively to determine the occurrence of PONV. For each day the actual incidence of PONV was compared with the mean predicted risk of PONV calculated with two risk scores for prediction of PONV (Koivuranta, 1997; Apfel, 1998). 32 days with the most significant difference between actual and predicted incidence of PONV were analysed retrospectively by two biometeorological experts, who were blind to the information whether each day was associated with a high or low incidence of PONV, evaluated the possible impact of the weather of these days. To analyse the influence of the cycle of the moon it was prospectively classified into four different phases.

RESULTS

The two biometeorologists rated 22 out of the presented 32 days correctly. The likelihood p that this rating happened by chance is 0.0251, assuming that the likelihood for predicting each day correctly is 0.5 (independent Bernoulli-experiments, e.g. throwing a coin). However, days with a high or low incidence of PONV were equally distributed within the four phases of the moon (p = 0.97; chi 2-test with Yates' correction).

CONCLUSION

Results from this analysis suggest that the weather may have some impact on the occurrence of PONV. However, our data do not support the hypothesis that the phases of the moon have any influence on this symptom.