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Department of Hepatology, University of Copenhagen, Rigshospitalet, Denmark
To the Editor:
In patients with an increased plasma bilirubin concentration undergoing liver transplantation, Madsen et al. (1) reported that near-infrared spectroscopy (NIRS) determined cerebral oxygenation (Somanetics; Troy, MI) is low suggesting that bilirubin also absorbs light although cerebral oxygenation increased during the reperfusion phase.
We report results from NIRS in a female patient (aged 62 yr) with graft failure after liver transplantation for fulminant hepatic failure. The patient was in hepatic coma (IV) and mechanically ventilated (15th day) with 45% O2. Blood gases were within normal limits. The blood bilirubin was 695 µmol · L-1. The pupils were with normal light reaction. A dual-channel Somatics determined cerebral and forearm muscle oxygenation, but the oximeter was unable to respond. Even with an increase in mean arterial pressure from 64 to 110 mm Hg and increased middle cerebral artery blood velocity (from 34 to 58 cm · s-1) during IV infusion of noradrenaline, tissue oxygenation still remained unmeasurable. Retranplatation was considered, but the patient died from septic shock before a donor became available.
The present study supports that severe hyperbilirubinemia makes the use of NIRS to estimate cerebral oxygenation impossible even in cases with significant alterations in cerebral blood flow during transplantation or in the ICU. NIRS using multiple wavelengths may overcome this problem.
References
Department of Anesthesiology University of Copenhagen Rigshospitalet, Denmark
In Response:
Drs. Nielsen and Larsen’s finding in their letter adds to the demonstration of the difficulties in measuring cerebral oxygen saturation (ScO2) with transcutaneous near-infrared spectrophotometry in severely icteric patients. In 48 liver transplant patients, we found the 95% prediction interval for the reperfusion-related increase in ScO2 to include 0% at a bilirubin value of approximately 650 mmol · L-1 (1). In one severely icteric female patient (bilirubin of 619 mmol · L-1) the ScO2 did not change at all, but she humorously assured me that her brain was well functioning by spontaneously naming the last 15 or so Danish kings. Interventional studies as described by Nielsen and Larsen with simultaneous measurements of ScO2 by transcutaneous near-infrared spectrophotometry and cerebral perfusion by transcranial Doppler would help elucidate the problem further. Bilirubin metabolites accumulate in skin and may absorb a large fraction of the near-infrared light (1). Determinations of ScO2 would be valuable before and after first bilirubin in blood and then biliverdin in skin have cleared.
References
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