The effects of hypocapnic ventilation on mental function in elderly patients undergoing cataract surgery

Mental function was studied using the Rivermead Behavioural Memory Test and the Unprepared Simple Reaction Time test in 83 elderly patients for cataract surgery. Three groups of patients were studied: Group N (n = 40) whose lungs were ventilated to a mean PaCO2 of 4.9 kPa, Group H (n = 30) who were hyperventilated to a mean PaCO2 of 2.9 kPa, and Group L (n = 13) who received local anaesthesia for surgery. The psychometric tests were administered on the day before the operation, and 4 days and 4 weeks after the operation. Statistically significant changes in the performance of hyperventilated patients could not be demonstrated using these tests.