Experimental approach for clinical use of NIRS as a monitor of hepatic oxygenation

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In this study, we evaluated whether it was possible to apply the near infrared spectroscopy (NIRS) to monitor the hepatic oxygenation. Furthermore, it was assessed the possibility of trance-esophageal approach of NIRS.(METHODS) The hepatic blood flow was measured by Doppler flowmetry. The probes of NIRS were placed on the liver surface in-group I, and the special probe for trance-esophageal approach was inserted into the stomach in-group II.Oxy-Hb and deoxy-Hb, and cytochrome oxidase (cyt. ox.) in the liver were calculated using 4 wavelength algorithms. (RESULTS AND DISCUSSION) In group I, (1) there was a positive correlation (r = 0.97, p < 0.01) between oxy-Hb and ShvO_2 during acute hemorrhage. (2) during infusion of noradrenarine, total hepatic blood flow and total Hb (oxy-Hb + deoxy-Hb) were significantly decreased, and cyt. ox. was reduced. (3) during congestion, oxy-Hb and deoxy-Hb were increased and cyt. ox. was reduced. (4) during infusion of endotoxin, there were three dynamic changes of hepatic blood flow. Oxy-Hb and deoxy-Hb were increased in stage II and III, while cyt. ox. was reduced in stage III.From these data, we concluded that the regional hepatic oxygenation was correctly monitored by the redox state of cyt. ox.. In-group II, (1) when the black sheet placed between stomach and liver was removed, the optical density measured by the probe inserted into stomach was significantly changed. (2) During occlusion of portal vein, cyt. ox. was reduced. From these data, it was suggested that NIR light is possible to penetrate easily the wall of stomach, and the hepatic oxygenation may be monitored via stomach by the trance-esophageal approach of NIRS.