Carbon Dioxide Homeostasis and Recovery after General Anaesthesia

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Abstract
The influence of different levels of CO2 during general anesthesia on postoperative recovery was studied. Female patients (60) undergoing abdominal gynecological surgery were divided into 2 groups. Thirty patients were > 60 yr old and 30 were < 46 yr old. Artificial ventilation with added CO2 during general anesthesia with thiopentone, N2O-O2, alcuronium and fentanyl was used. According to the arterial CO2 tension [PaCO2], patients were allocated to subgroups (hypercarbic, PaCO2 7.3 kPa [kilopascal]; normocarbic, PaCO2 5.3 kPa) and 2 different levels of hypocarbia (older patients PaCO2 3.7 kPa and younger patients PaCO2 2.9 kPa). As criteria for recovery, a battery of recovery tests and postoperative questionnaires were used. Regardless of age, patients subjected to hypercarbic ventilation scored better in the recovery tests than patients subjected to normo- or hypocarbia. Normocarbic ventilation also gave better results than hypobaric ventilation. The level of hypocarbia used in the older patients and that used in the younger patients, although different, resulted in nearly the same deterioration of scoring in the recovery tests. This deterioration was seen in some patients up to 48 h postoperatively. No subjective differences were elicited from the questionnaires after various types of ventilation.