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

Background and Objectives To develop a transfusion trigger based on tissue oxygenation, near-infrared spectroscopy (NIRS) was evaluated in a model of compensated haemorrhage. Patients and Methods 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. Results 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. Conclusions CsO₂ and PsO₂ fell predictably during compensated blood loss. With further research, NIRS may be developed into a transfusion trigger. [ABSTRACT FROM AUTHOR]