Evaluation of cerebrovascular carbon dioxide reactivity in patients with diabetes mellitus under sedative doses of propofol

The present study compared cerebrovascular CO2 reactivity in diabetic patients on different treatment modalities under sedative doses of propofol. Fifteen patients with diabetes mellitus (on three different antidiabetic treatment modalities) who required mechanical ventilation during intensive care therapy were studied, sedation during mechanical ventilation being maintained using propofol. As controls, 6 patients without diabetes were monitored. A 2.5-MHz pulsed transcranial Doppler probe was attached to the head of the patient at the right temporal window for continuous measurement of mean blood flow velocity in the middle cerebral artery (Vmca). After establishing baseline values of Vmca and cardiovascular hemodynamics, end-tidal CO2 was decreased by increasing ventilatory frequency by 5–8 breaths·min−1. Values for absolute and relative CO2 reactivity in insulintreated patients were lower than those in the other three groups (absolute CO2 reactivity [means ± SD]: control, 3.1 ± 0.6 cm·s−1·mmHg−1, diet, 3.8 ± 1.4 cm·s−1·mmHg−1; oral antidiabetic drug 3.2 ± 0.9 cm·s−1·mmHg−1; insulin, 1.1 ± 0.6 cm·s−1·mmHg−1; P = 0.002).