Foreseeing the danger in the beach chair position: Are standard measurement methods reliable?

The aim of this study is to show whether peripheral perfusion monitoring methods reflect central perfusion during shoulder arthroscopy at beach chair position. We hypothesized that mean arterial pressure (MAP), central heart rate (CHR) and peripheral oxygenation (SaO2) measurements individually will not parallel cerebral oximetry measurements by near-infrared spectroscopy (NIRS).

Between 2011 and 2012, 53 patients who had arthroscopic rotator cuff repair surgery in the beach chair position were enrolled prospectively. Median ages of the patients were 58 (range 42-68) years. The regional cerebral oxygen saturation value of each hemisphere was continuously monitored by the use of NIRS. MAP, CHR, SaO2 and both hemispheric cerebral oxygen saturation values were recorded at six time periods peri-operatively. Correlation and differences between parameters were evaluated.

Cerebral oxygen saturation of right hemisphere was dropped >20 % in 28.3 and 45.3 % of the patients. At left hemisphere, cerebral oxygen saturation was dropped >20 % in 20.8 and 43.4 % of the patients. Peripheral saturation values were statistically different from cerebral saturation values (p < 0.001). On the other hand, there was a correlation between cerebral saturation and MAP values (p < 0.05).

Cerebral oximetry by NIRS may prove useful as a monitor for cerebral ischaemia. In the absence of NIRS, CHR can partially detect abnormalities but not trustable, and MAP is the most reliable method for monitoring.