PERIOPERATIVE MONITORING WITH PULSE OXIMETRY AND LATE POSTOPERATIVE COGNITIVE DYSFUNCTION

In a randomized, blinded clinical study, we have used objective and su bjective measures to determine if perioperative monitoring with pulse oximetry-by virtue of its potential to lessen hypoxaemia-would decreas e late postoperative cognitive dysfunction. We investigated 736 adult patients undergoing elective procedures (other than cardiac, neurosurg ical or for cancer) under-regional or general anaesthesia, allocated r andomly to undergo (group I) or not to undergo (group II) pulse oximet ry monitoring in the operating theatre and recovery room. Cognitive fu nction was evaluated using the Wechsler memory scale (WMS) and continu ous reaction time (RT) test the day before surgery, and on the 7th day after operation or at discharge if that occurred before postoperative day 7. A questionnaire sent 6 weeks after surgery elicited patients' subjective perceptions regarding cognitive abilities. There were no si gnificant differences between the two groups in either the total WMS s core, the score for each WMS subtests or RT test The questionnaire rev ealed that 7% in group I and 11% in group II believed cognitive abilit ies had decreased (ns). For the 40 patients whose WMS scores were 10 p oints less after than before operation, a follow-up study was undertak en 3 months after surgery. At that time, the median WMS score had retu rned to the preoperative value. We conclude that, for these 736 patien ts, subjective and objective measures did not indicate less postoperat ive cognitive impairment after perioperative monitoring with pulse oxi metry.