The aim of the present study was to investigate whether changes in hepatic oxygenation can be detected by time-resolved spectroscopy (TRS) placed on the skin surface above the liver.
Methods: With approval of the local Hospital Ethics Committee and informed consent, six healthy volunteers aged 28.8 (25-36) years, and five patients with chronic renal failure aged 70.6 (58-81) years were studied. In six healthy volunteers, following echography, TRS (TRS-10, Hamamatsu Photonics K.K., Hamamatsu, Japan) probes consisting of a near-infrared light (at 760, 800, 835 nm) emitter and a receiver optode, were placed 4 cm apart on the abdominal skin surface above the liver or at least 10 cm distant from the liver. In five patients with chronic renal failure, following echography, TRS probes were placed 4 cm apart on the skin surface above the liver during hemodialysis (HD).
Results: In six healthy volunteers, the values of abdominal total hemoglobin concentration (tHb) were significantly higher in the liver area than in the other area (80.6±26.81 vs 44.6±23.1 μM, p=0.0017), while the value of abdominal SO2 in the liver area was nearly the same as that in the other area (71.5±3.6 vs 73.6±4.6%, p=0.19). The values of mean optical pathlength and scattering coefficient (μ's) at 800 nm in the liver area were significantly different from those in the other area (21.3±4.9 vs 29.2±5 cm, p=0.0004, and 7.97±1.14 vs 9.02±0.51 cm(-1), p=0.015). One of five patients with chronic renal failure complained of severe abdominal pain during HD, and abdominal SO2 decreased from 53 to 22%; however, pain relief occurred following cessation of HD, and SO2 recovered to the baseline level.
Conclusions: Our data suggest that the optical properties of the liver may be measured by the TRS placed on the skin surface, and the hepatic oxygenation may act as a non-invasive monitoring for early detection of intestinal ischemia.
Keywords: Liver; Near-infrared spectroscopy; Splanchnic ischemia; Time-resolved spectroscopy; Tissue oxygenation.