Carbon dioxide absorption during laparoscopic cholecystectomy and inguinal hernia repair

Abstract

Laparoscopic surgical procedures require CO2 insufflation. The extent of CO2 absorption may differ with regard to the surgical technique used. The aim of this study was to quantify the CO2 absorption following intra- and extraperitoneal insufflation. The study was approved by the Ethics Committee and informed consent was obtained. Two groups of 25 ASA I and II patients each were prospectively studied: laparoscopic cholecystectomy (group A) and inguinal hernia repair (group B). All patients had no medical history of pulmonary or cardiac disease. All patients underwent the same standardized general anaesthesia. Following tracheal intubation, all patients were mechanically ventilated (RR=12 min−1; VT=8 ml kg−1). After 20 min (T1), baseline measurements of HB, BP, CVP, airway pressure, PET CO2 and oxygen saturation were performed and an arterial blood was sampled for gas analysis. Then, CO2 insufflation was started and the VT was adjusted to maintain PET CO2 at baseline level. After 20 min of insufflation (T2), all measurements and arterial blood gas sampling were repeated. The paired and unpaired Student's t-test was used to compare within and between groups respectively. Differences were considered significant at the P<0.01 level. Age in group A and B was 53 ± 13 and 60 ± 12 years respectively. Weight was 69 ± 9 (group A) and 72 ± 9.5 kg (group B). The comparison within groups at T1 and T2 revealed no significant differences for PET CO2, Pa CO2, HR and BP. In both groups, a statistically significant increase in peak airway pressure, CVP and VT was found. The increase in VT required to maintain normocapnia in group A was 30.9 ± 8.4% (from 556 ± 79 to 724 ± 84 mL), the required increase in group B was 55.4 ± 19.5% (from 592 ± 92 to 909 ± 104 mL). Statistical differences between groups were found for the increase in VT, CVP and airway pressure. This study provides evidence that extraperitoneal CO2 insufflation induces a greater CO2 absorption compared with intraperitoneal insufflation.