Significant decrease of cerebral oxygen saturation during single-lung ventilation measured using absolute oximetry

Single-lung ventilation (SLV) during thoracic surgery causes important cardiopulmonary disturbances. Absolute cerebral oximetry was used to determine the incidence and magnitude of the decrease in cerebral oxygen saturation (Sct(o(2))) in patients undergoing SLV during thoracic surgery.

Data were obtained from 20 consecutive patients undergoing thoracic surgery and necessitating SLV of more than 1 h. The FORESIGHTtrade mark (CASMED, USA) absolute oximeter was used to measure left, right, and average absolute Sct(o(2)) every 5 min from the awake state to extubation. Bispectral index and standard monitoring parameters were also recorded every 5 min. Blood gas analysis was performed every 15 min. Data median (IQR) (range) were analysed using repeated-measures anova and Spearman's correlation test, P<0.05.

Patients [median age 65 yr (range 46-75)] showed an absolute Sct(o(2)) of 80% (78, 82) (74-87) in the awake state, which decreased to a minimum Sct(o(2)) value of 63% (57, 65) (53-73) during SLV to recover to an Sct(o(2)) of 71% immediately after extubation. During SLV, all patients had a decrease of more than 15% of the initial Sct(o(2)) and 70% of patients had a decrease of more than 20%. The decrease in Sct(o(2)) was not correlated with any standard clinical parameters, for example, arterial pressure, blood loss, peripheral oxygen saturation, or Pa(o(2)).

Thoracic surgery with SLV seems to be associated with a significant decrease of Sct(o(2)) in the majority of patients. Parameters such as peripheral oxygen saturation or Po(2) which are used to guide SLV during thoracic surgery are not sufficient to detect significant cerebral oxygen desaturations.