Tissue hemoglobin O-2 saturation during resuscitation of traumatic shock monitored using near infrared spectrometry

Background: Near infrared (NIR) spectrometry offers a noninvasive monitor o f tissue hemoglobin O-2 saturation and has been developed to report a quant itative clinical variable, Sto(2) [= HbO(2)/(HbO(2) + Hb)]. In this study, a prototype NIR oximeter was used to investigate the hypothesis that change s 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 occ urs 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 hemog lobin O-2 saturation (Svo(2)). Methods: Skeletal muscle and subcutaneous tissue Sto(2) were monitored simu ltaneously in eight severely injured trauma patients (88% blunt mechanism; age, 42 +/- 6 years; Injury Severity Score, 27 +/- 3) during standardized s hock 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% (mea n +/- 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 8 2% 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 simul taneously in skeletal muscle and subcutaneous tissues as Sto(2) (%) by usin g a prototype NIR oximeter. Skeletal muscle Sto(2) tracked systemic O-2 del ivery 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 resuscitati on in the intensive care unit, to monitor resuscitation status in the opera ting room, and, potentially, in combination with indicators such as base de ficit and lactate, to detect shock during initial assessment of the severe trauma patient in the emergency department.