Cerebral oxygen saturation and cardiac output during anaesthesia in sitting position for neurosurgical procedures: a prospective observational study.

BACKGROUND: Neurosurgical operations in the dorsal cranium often require the patient to be positioned in a sitting position. This can be associated with decreased cardiac output and cerebral hypoperfusion, and possibly, inadequate cerebral oxygenation. In the present study, cerebral oxygen saturation was measured during neurosurgery in the sitting position and correlated with cardiac output.

METHODS: Perioperative cerebral oxygen saturation was measured continuously with two different monitors, INVOS® and FORE-SIGHT® . Cardiac output was measured at eight predefined time points using transoesophageal echocardiography.

RESULTS: Forty patients were enrolled, but only 35 (20 female) were eventually operated on in the sitting position. At the first time point, the regional cerebral oxygen saturation measured with INVOS® was 70 (sd 9)%; thereafter, it increased by 0.0187% min-1 (P<0.01). The cerebral tissue oxygen saturation measured with FORE-SIGHT® started at 68 (sd 13)% and increased by 0.0142% min-1 (P<0.01). The mean arterial blood pressure did not change. Cardiac output was between 6.3 (sd 1.3) and 7.2 (1.8) litre min-1 at the predefined time points. Cardiac output, but not mean arterial blood pressure, showed a positive and significant correlation with cerebral oxygen saturation.

CONCLUSIONS: During neurosurgery in the sitting position, the cerebral oxygen saturation slowly increases and, therefore, this position seems to be safe with regard to cerebral oxygen saturation. Cerebral oxygen saturation is stable because of constant CO and MAP, while the influence of CO on cerebral oxygen saturation seems to be more relevant.

CLINICAL TRIAL REGISTRATION: NCT01275898.