Gastric air tonometry during laparoscopic cholecystectomy: a comparison oftwo PaCO2 levels

Purpose: Pneumoperitoneum can cause disturbances in acid-base balance and s planchnic perfusion. We studied the effect of ventilation on acid-base bala nce and gastric mucosal tonometric values in patients undergoing laparoscop ic cholecystectomy. Methods: Twenty-four patients (ASAI-II)were randomly allocated into two gro ups. In the fixed ventilation group, ventilation was constant allowing free increase in PCO2, while in the constant CO2 group end-tidal PCO2 was fixed with ventilatory adjustment. Intraabdominal pressure was limited to 12 mmH g. Arterial acid-base balance, automated air tonometric variables and gastr ic mucosal to arterial PCO2 gap were determined frequently from anesthesia induction until three hours postoperatively. Results: During pneumoperitoneum, in the tired ventilation group arterial P CO2 changed from 5.0 +/- 0.2 to 6.6 +/- 0.4 kPa and pH from 7.43 +/- 0.03 t o 7.33 +/- 0.04, tonometric PCO2 from 5.1 +/- 0.5 to 6.9 +/- 0.4 and pH fro m 7.44 +/- 0.04 to 7.33 +/- 0.04. In the constant CO2 group these variables remained at control levels (P < 0.01 between groups). The PCO2 gap remaine d unchanged without any differences between the groups. In the recovery roo m all measured variables were within normal range in both groups. Conclusion: Despite inter-group differences in arterial and tonometric PCO2 and pH values during CO2 pneumoperitoneum, the patients did not develop sp lanchnic hypoperfusion detectable by air tonometric method, as indicated by normal PCO2 gap in both groups throughout the study.