Metabolic effects of Carbon Dioxide (CO2) insufflation during laparoscopic surgery: changes in pH, arterial partial Pressure of Carbon Dioxide (PaCo2) and End Tidal Carbon Dioxide (EtCO2)
Background: Acid base alterations occur during laparoscopy with carbon dioxide insufflation. The purpose of this study was to investigate the effects of low tidal volume ventilation on acid base status during pneumoperitonium.
Materials and Methods: 30 patients undergoing laparoscopic surgery under General Anaesthesia were ventilated with tidal volume of 6 ml/kg and respiratory rate of 12 breaths/minute. Arterial blood gas analysis was done before, during and after C02 pneumoperitoneum. Arterial haemoglobin oxygen saturation by pulse oximetry (SPO2) and EtC02 were monitored continuously throughout the laparoscopy. Respiratory adjustments were done for EtCO2 levels above 60mmHg or SPO2 below 92% or adverse haemodynamic changes.
Results: low tidal volume ventilation during pneumoperitoneum resulted in a significant elevation in PaCO2 (p<0.001) and a fall of pH (p <0.001), ion bicarbonate (HCO3-) (p = 0.011), and base excess (ABE) (p <0.001). A correlation was found between the EtCO2 and PaCO2 during pneumoperitoneum. Oxygenation was well maintained during pneumoperitoneum. No ventilatory adjustments were instituted on any of the patients as they maintained EtCO2 below 60mmHg throughout pneumoperitoneum.
Conclusion: Ventilation with low tidal volume during pneumoperitoneum causes a mixed respiratory and metabolic acidosis. EtCO2 is still a good non-invasive monitor for estimation of PaCO2 during low tidal volume ventilation during pneumoperitoneum.