Postoperative nausea and vomiting in women : An unglamorous aspect of anaesthesia

Postoperative nausea and vomiting (PONY) still remains a common and undesirable side effect of anaesthesia. Women are afflicted by PONY two to three times more often than men and a substantial number of patients consider PONV to be the worst part of the entire surgical procedure. Despite recent advances within the practice of anaesthesia little has been done to improve our understanding of the fundamental mechanisms of PONV. The aims of this dissertation were to identify the incidence of PONV after the various surgical procedures performed in women, and to investigate whether alternate anaesthetic regimens or prophylactic pharmacological or non-pharmacological interventions could influence the incidence of PONY Various blood- borne factors that may be of importance for the development of PONV in women undergoing breast cancer surgery were also studied. Methods: In total 546 women were included in six different studies. Women undergoing termination of pregnancy and breast cancer surgery under different anaesthetic regimens were studied with respect to the incidence of PONV and to identify potentially favourable anaesthetic combinations with regards to PONY The antiemetic effects of the 5-HT3 receptor antagonist tropisetron, intra-operative positive suggestion or coinduction with the alpha2 adrenoceptor agonist clonidine were studied in women undergoing laparascopic gynaecological surgery and breast cancer surgery under general anaesthesia. To study further the basic mechanisms responsible for PONV, various blood-borne factors (serotonin, epinephrine, norepinephrine, dopamine, vasopressin, CCK, gastrin, blood glucose and platelet count) that may be of importance for the development of PONV in women undergoing breast cancer surgery were analysed. Results: The incidences of PONV after termination of pregnancy, breast cancer surgery and laparoscopic gynaecological surgery were 7.5%, 57% and 47%, respectively. No clinically important differences with regard to the incidence of PONY were found between the anaesthetic regimens studied. Prophylactic treatment with tropisetron or intra-operative positive suggestion did not reduce the incidence of PONV, but recall of nausea and vomiting 24 hrs postoperatively was reduced in patients exposed to intra-operative positive suggestion (p < 0.05). Co-induction with clonidine reduced the dose of propofol (p < 0.04), sevoflurane (p < 0.03) and early need for ketobemidone (p < 0.04) and most importantly increased the number of PONV freepatients compared to placebo (66% vs. 36%; p < 0.04). Women with PONV after breast cancer surgery under general anaesthesia had a larger dispersion of platelet counts (p = 0.001), a reduced platelet count on the first postoperative day (p = 0.02) and a less pronounced relationship between platelet count and whole blood serotonin (p = 0.002) compared to PONV-free subjects. No reduction in epinephrine levels in response to the induction of anaesthesia (p 0.03) as well as increased levels of vasopressin (p = 0.00004), epinephrine (p = 0.005) and blood glucose (p 0.004) were also observed during the early postoperative period in patients with PONV. Conclusion: Approximately 50 % of women experience PONV after breast cancer surgery and laparoscopic gynaecological surgery. Various combinations of anaesthetic drugs did not have any major impact on the incidence of PONY but co-induction with clonidine was found to increase the number of PONV-free patients. Three different platelet-related factors and an altered epinephrine pattern were found in women suffering from PONV after breast cancer surgery, a finding that may suggest a genetic link to PONV