Tissue hemoglobin O2 saturation during resuscitation of traumatic shock monitored using near infrared spectrometry

Background: Near infrared (NIR) spectrometry offers a noninvasive monitor of tissue hemoglobin O-2 saturation and has been developed to report a quantitative clinical variable, Sto(2) [= HbO(2)/(HbO(2) + Hb)]. In this study, a prototype NIR oximeter was used to investigate the hypothesis that changes in systemic O-2 delivery index (Do(2)I) would be reflected by changes in Sto(2) in skeletal muscle, subcutaneous tissue, or both, as reperfusion occurs during shock resuscitation. Sto(2) was also compared with other indices of severity of shock or adequacy of resuscitation, including arterial base deficit, lactate, gastric mucosal Pco(2) (Pgco(2)), and mixed venous hemoglobin O-2 saturation (Svo(2)). Methods: Skeletal muscle and subcutaneous tissue Sto(2) were monitored simultaneously in eight severely injured trauma patients (88% blunt mechanism; age, 42 +/- 6 years; Injury Severity Score, 27 +/- 3) during standardized shock resuscitation in the intensive care unit with the primary goal of Do(2)I 600 mL O-2/min/m(2) for 24 hours, and for an additional 12 hours during transition from resuscitation to standard intensive care unit care. Results: Skeletal muscle Sto(2) increased significantly from 15 +/- 2% (mean +/- SEM) at the start of resuscitation to 49 +/- 14% at 24 hours, and to similar to 55% from 25 to 36 hours. Subcutaneous tissue Sto(2) similar to 82% and was significantly greater than skeletal muscle Sto(2) throughout. Do(2)I increased significantly from 372 +/- 54 to 718 +/- 47 mL O-2/min/m(2) during resuscitation, Over 36 hours, mean Do(2)I and skeletal muscle Sto(2) were highly correlated (r = 0.95). Neither Do(2)I-Pgco(2) nor Do(2)I-Svo(2) were significantly correlated; neither Svo(2) nor subcutaneous tissue Sto(2) changed significantly. Conclusion: Hemoglobin O-2 saturation was monitored noninvasively and simultaneously in skeletal muscle and subcutaneous tissues as Sto(2) (%) by using a prototype NIR oximeter. Skeletal muscle Sto(2) tracked systemic O-2 delivery during and after resuscitation. As a rapidly deployable, noninvasive monitor of peripheral tissue oxygenation and O-2 delivery, skeletal muscle Sto(2) obtained using NIR spectrometry would be useful to guide resuscitation in the intensive care unit, to monitor resuscitation status in the operating room, and, potentially, in combination with indicators such as base deficit and lactate, to detect shock during initial assessment of the severe trauma patient in the emergency department.