Cerebral and peripheral near-infrared spectroscopy: an alternative transfusion trigger?

Abstract

To develop a transfusion trigger based on tissue oxygenation, near-infrared spectroscopy (NIRS) was evaluated in a model of compensated haemorrhage. Regional haemoglobin oxygen saturation from the cerebral cortex (CsO2) and the gastrocnemius muscle (PsO2) was monitored (using an INVOS 4100 near-infrared oximeter) in 30 patients during acute normovolaemic haemodilution to a target haemoglobin of 11 g/dl. Arterial oxygen saturation, end-tidal carbon dioxide tension, mean arterial pressure and haemoglobin concentration were also measured. During blood collection, CsO2 and PsO2 fell by a mean (95% CI) of 8 (5.3-10.7)% (P < 0.001) and 5.5 (3.2-7.8)% (P < 0.001), respectively. Arterial pressure and oxygen saturation did not change, whilst the end-tidal carbon dioxide tension fell by 2.3 (0.8-3.8) mmHg (P = 0.004). Haemoglobin concentration correlated with CsO2 (R = 0.76, P < 0.001) and PsO2 (R = 0.63, P < 0.001), as did the volume of blood removed. CsO2 and PsO2 fell predictably during compensated blood loss. With further research, NIRS may be developed into a transfusion trigger.