Accepting an Increased End Tidal CO2 During Laparoscopic Bariatric Surgery Reduces Tidal

Accepting an increased end tidal CO2 during laparoscopic bariatric surgery reduces tidal volume and lowers airway pressures.
Mulier J.P.1, Sels A 2. Dillemans B.3, Segers G.1, Casier I.1, Akin F.3, Thibaut F.3,

1AZ st Jan av Brugge, Anesthesiology, Bruges, Belgium

2 H.U.Brussel, K.U.Leuven, Business and economics, Brussels, Belgium

3 AZ st Jan av Brugge, General surgery, Bruges, Belgium,

During mechanical ventilation a high end-tidal PCO2 increases cardiac output and improves microcirculation in obese patients.(1) The goal of this study was to accept a higher end-tidal PCO2 and to measure the effect on ventilation and vasopressor use Twenty obese patients with a BMI above 40 who underwent bariatric surgery received pressure controlled ventilation (PCV) at a rate of 14 respirations/min and a positive end-expiratory pressure (PEEP) of 5 cmH2O with approval of the hospital ethical committee. The adapted pressure was set to achieve an end-tidal PCO2 below 40 mmHg in one group and below 60 mmHg in the other group. To evaluate the comparability of the groups, each patient received volume controlled ventilation (VCV) before PCV, at a tidal volume of 500 ml, a rate of 14 respirations/min, and a PEEP of 5 cmH2O while the plateau airway pressure was measured. During PCV the following parameters were measured: the adapted minute volume, the airway pressure, the end-tidal PCO2 and the amount of ephedrine injected to keep the systolic arterial pressure above 140 mmHg during inspection of the staple line. These parameters were compared between the groups using a non paired t test. Oxygen saturation measured by pulse oximetry, switching to spontaneous breathing and awakening time were also compared. There were no significant differences in BMI, age and airway pressure during VCV between the groups. Minute volume ventilation, airway pressures and ephedrine use were significantly higher in the group with low end-tidal PCO2. Ventilation at a high end-tidal PCO2 is possible. Cardiac output was not measured but was probably higher as less ephedrine was needed to elevate the blood pressure. In the group with the high end-tidal PCO2, oxygen saturation was not lower, and spontaneous breathing and awakening occurred more rapidly. We conclude that there is an advantage in slight hypoventilation in obese patients during a pneumoperitoneum with CO2.

1. Hager H. Hypercapnia improves tissue oxygenation in morbidly obese surgical patients.

Anesth Analg. 2006 Sep;103(3):677-81.