Metabolic effects of carbon dioxide insufflation during laparoscopic surgery: Changes in pH, arterial partial pressure of carbon dioxide (PaCO2) and end tidal carbon dioxide (EtCO2).
Purpose: The purpose of this study was to assess the effects of low tidal volume ventilation on patients undergoing laparoscopic surgery on partial pressure of carbon dioxide, arterial to end tidal carbon dioxide gradient and acid base excess. Methods: 30 patients undergoing laparoscopic surgery under General Anaesthesia were ventilated with tidal volume of 6 ml/kg and respiratory rate of 12breaths/minute and End tidal C02, PaC02, pH, Bicarbonate and ABE measurement was done before, during and after C02 pneumoperitoneum and analyzed. Respiratory adjustments were done for End tidal CO2 levels above 60mmHg or haemodynamic changes attributable to elevated CO2. Results: Pneumoperitoneum resulted in a significant elevation in PaCO2 (p<0.001) and a fall of pH (p <0.001), ion bicarbonate (p = 0.011), and base excess (p <0.001). A correlation was found between the EtCO2 and PaCO2 during pneumoperitoneum. No ventilatory adjustments were instituted on any of the patients as they maintained EtCO2 below 60mmHg throughout pneumoperitoneum. Conclusion: Besides the expected respiratory acidosis, a metabolic acidosis can also be present during pneumoperitoneum. EtCO2 is still a good non invasive monitor for estimation of PaCO2 during low tidal volume ventilation during pneumoperitoneum.