Carbon dioxide elimination pattern in morbidly obese patients undergoing laparoscopic surgery

Abstract

BackgroundHypercapnia can result from carbon dioxide pneumoperitoneum and adversely affect the postoperative period, particularly in morbidly obese patients. The purpose of the present study was to examine carbon dioxide homeostasis using a metabolic monitor in morbidly obese and normal weight patients during laparoscopic surgical procedures. The setting was a university hospital in Italy. MethodsThe data from 25 patients with a body mass index of 47.7 ± 5.5 kg/m2 undergoing laparoscopic gastric mini-bypass were compared with the data from 25 normal weight patients undergoing laparoscopic cholecystectomy. The minute ventilation was adjusted to maintain a normal arterial partial pressure of carbon dioxide and normal end-tidal partial pressure of carbon dioxide throughout surgical procedures. The arterial partial pressure of carbon dioxide, end-tidal partial pressure of carbon dioxide, total exhaled carbon dioxide per minute, and arterial blood gas analysis were obtained at 10-minute intervals, along with other cardiorespiratory parameters. ResultsThe total exhaled carbon dioxide per minute increased by the same percentage in both groups (around 20%). In the laparoscopic cholecystectomy patients, a definite plateau in the total exhaled carbon dioxide per minute was observed within 20 minutes from the start of pneumoperitoneum but not in the morbidly obese patients. After desufflation, the total exhaled carbon dioxide per minute returned more rapidly to the baseline values in the laparoscopic cholecystectomy group than in the morbidly obese group (17.4 ± 6.2 and 24.1 ± 8.3 min, respectively). ConclusionThe results of our study have shown that the load of carbon dioxide insufflated is well tolerated in morbidly obese patients, as well as in normal patients, with proper intraoperative ventilation adjustments. However, after pneumoperitoneum, the return to a normal total exhaled carbon dioxide per minute required a longer period in the morbidly obese group. Prolonged mechanical ventilation is therefore advisable in morbidly obese patients.