A comparison of the incidence of hypercapnea in non-obese and morbidly obese peri-operative patients using the SenTec transcutaneous pCO2 monitor

Abstract

Obese patients are at increased risk for hypoventilation, leading to hypercapnea and acidosis. The primary objective of this study was to compare the incidence of perioperative hypercapnea in non-obese and morbidly obese patients using the SenTec transcutaneous PCO2 (tcPCO2) monitor. 10 morbidly obese subjects (BMI>40kg/m(2)) undergoing laparoscopic bariatric surgery, and 10 non-obese subjects (BMI<30kg/m(2)) undergoing laparoscopic abdominal procedures were studied, using a standardized anesthesia regimen. TcPCO2 and SpO2 were monitored continuously intraoperatively, and during the first 24h postoperatively. Opiate consumption, respiratory rate (RR), and pain scores were collected from postanesthesia care unit (PACU) and ward nursing notes. RR, SpO2, and tcPCO2 did not differ significantly between groups during PACU or ward time periods. End-tidal CO2 (EtCO2) values were similar between groups during the intraoperative period, but tcPCO2 was significantly higher in the obese group at specific time points, and trended towards being higher throughout the case. Our study did not show significant tcPCO2 differences between non-obese and obese post-surgical patients, however, it did allow for continuous, trendable, nonobtrusive monitoring throughout the perioperative period. As V/Q mismatch increases with the PaCO2/EtCO2 gradient, and this effect is most pronounced in morbidly obese patients, tcPCO2 monitoring may prove to be a useful additional monitor in these patients during the intraoperative period.