Haemodynamic changes and vasopressin release are not consistently associated with carbon dioxide pneumoperitoneum in humans

Background: Conflicting haemodynamic changes, suggested to be caused by vas opressin release, have been reported during carbon dioxide (CO2) pneumoperi toneum. However, peritoneal stimulations including open surgery cause both a systemic vasopressor response and a vasopressin release, which are suppre ssed by opiate administration. Also, a decreased venous return of blood to the heart causes vasopressin release. Furthermore, previous haemodynamic as sessments of laparoscopic surgery have been conducted using various anaesth etic regimens, which are likely to have caused various haemodynamic effects . We hypothesised that intraoperative haemodynamic and/or humoral changes w ould not be observed in association with laparoscopic surgery provided that , (a) normovolaemia is continuously maintained using transoesophageal echoc ardiographic (TEE) assessment, and (b) adequate depth of general anaesthesi a is continuously maintained by bispectral index (BIS) monitoring and high plasma level opiate administration. Methods: Twenty ASA 1 women undergoing laparoscopic surgery received 10 ml. kg(-1) lactated Ringer's solution and thereafter were randomly allocated to receive intraoperatively either 8 ng.ml(-1) or 4 ng.ml(-1) plasma remifent anil concentrations while BIS was maintained at 50 +/-5 by isoflurane alter ation. The group receiving 4 ng.ml(-1) remifentanil was used as control. Ex pired CO2 was maintained within a 32-38 kPa range throughout the investigat ion. Complete TEE haemodynamic investigation was performed before pneumoper itoneum (PP) (T1), and during Pr horizontal (T2), with a head-up tilt (T3), with a head-down tilt (T4), horizontal (T5), and PP released (T6). Plasma vasopressin, epinephrine and norepinephrine levels were measured at T1, T3, and T6. ANOVA, Student's t-test and Mann-Whitney U-test were used for stat istical analysis. Results: Haemodynamic indices and humoral values did not change significant ly within and between remifentanil groups throughout the investigation (all P <0.05). Conclusion: Continuous adequate depth of anaesthesia and normovolaemia may have prevented both a humoral and a haemodynamic response, initiated in the peritoneum by the contact with CO2 in previous investigations.