Near-infrared monitoring of hemoglobin content in the kidney during ischemia

Abstract

Near infrared spectroscopy was used to monitor changes in hemoglobin concentration in the kidney of 9 anesthetized rabbits during ischemic conditions. Laser diodes (775, 810, 862, and 904 nm) were placed on the surface of the kidney, the transmitted light was detected by a photomultiplier. Three stages of ischemia were induced in the kidney by occluding the abdominal aorta to approximately 1/3, 2/3 and total occlusion. Hemoglobin content was monitored during 10 minutes of occlusion followed by 10 minutes of recovery. The occlusions resulted in an average decrease in blood pressure of 36%, 53% and 100% in the abdominal aorta. The partial occlusions resulted in an increasing trend in total hemoglobin content during the 10 minutes occlusion followed by a return to baseline hemoglobin concentration. Within the first 30 seconds of the total occlusion maneuver, an immediate decrease in hemoglobin content was observed. During the occlusion the hemoglobin content increases slowly, corresponding to an increase in reduced hemoglobin content. Oxygenated hemoglobin content remained constant during the occlusion and increased immediately when the occlusion was released.