The purpose of this study was to investigate the feasibility of using near infrared (NIR) spectroscopy of the liver to simultaneously assess oxygen content in combination with tissue pH, an indicator of anaerobic metabolism. Six anesthetized swine were subjected to 45 min of hemorrhagic shock followed by resuscitation with blood and crystalloid. Calibration models between NIR spectra and reference measurements of tissue pH, hepatic venous oxygen saturation (SvO2), and blood hemoglobin concentration (Hb) were developed using partial least-squares regression. Model accuracy was assessed using cross validation. The average correlation (R2) between NIR and reference measurements was 0.87, 0.68, and 0.93, respectively for pH, Hb, and SvO2. Estimated accuracy, the root mean squared deviation between spectral, and reference measurements was 0.03 pH units, 0.3 g/dL, and 6%. NIR determination of hepatic oxygen content and tissue pH during shock and resuscitation demonstrated that there can be a variance between hepatic venous oxygenation and regional tissue acidosis. NIR spectroscopy provides a technique to explore the implications of post-shock depression of tissue pH and evaluate new methods of resuscitation.
*Department of Surgery, University of Massachusetts Medical School, Worcester, Massachusetts; †Department of Surgery, Brigham and Women's Hospital, Boston, Massachusetts; and ‡Department of Anesthesiology, University of Massachusetts Medical School, Worcester, Massachusetts
Received 25 May 2000; first review completed 9 Jun 2000; accepted in final form 18 July 2000
Address reprint requests to Babs R. Soller, PhD, Department of Surgery, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA.
©2001The Shock Society