Cerebral oxygenation when ventilated or spontaneously breathing: a randomised control trial

Cerebral oxygenation is an important area of concern during shoulder surgery in the beach chair position. Although infrequent, patients may experience serious morbidity or mortality secondary to the cerebral ischaemia which may follow cerebral desaturation. There is no published randomised control trial studying the effect of spontaneous ventilation vs intermittent positive pressure ventilation (IPPV) on cerebral oximetry.

We randomised 40 patients (20 in each treatment group) undergoing arthroscopic shoulder surgery to either breathe spontaneously or receive IPPV during their surgery. Other elements of anaesthetic care were standardised. We recorded a baseline measure of cerebral oxygen saturation immediately prior to induction of anaesthesia for each cerebral hemisphere. We measured cerebral oxygenation throughout the intraoperative period, but the treating anaesthetist was blinded to this data. The primary outcome was time-averaged change in cerebral oxygenation during the intraoperative period. The secondary outcome was the incidence of cerebral desaturation events, defined as a ≥ 20% fall below baseline, or an absolute value of 55% or less.

We collected and analysed data on all 40 patients. The intraoperative increase in cerebral oximetry (mean, sd) for the left and right cerebral hemispheres was 10.5 (7.62) and 12.6 (6.24) for spontaneously breathing patients and 12.9 (7.65) and 11.0 (6.49) for IPPV patients (p = 0.332 and p = 0.427 respectively). There were three cerebral desaturation events in spontaneously breathing patients and eight in ventilated patients (p = 0.155).

Ventilatory strategy (IPPV vs spontaneous ventilation) did not have a statistically significant impact on cerebral oxygenation in this study.

This trial was retrospectively registered on 10/2/2023 with the ANZCTR. TRN ACTRN12623000143628.