Effects of Temperature and Propofol on Hepatic Blood Flow
1996; Lippincott Williams & Wilkins; Volume: 82; Issue: 2 Linguagem: Inglês
10.1097/00000539-199602000-00040
ISSN1526-7598
Autores Tópico(s)Thermal Regulation in Medicine
ResumoTo the Editor: We read with interest the article by Leslie et al. [1] in which the authors studied the effects of temperature and propofol on hepatic blood flow. The authors measured clearance using an indicator dye but never gave an actual value of estimated hepatic blood flow. From previous studies, one would assume this value to be approximately 1000 mL/min. We were surprised by the conclusion that propofol reduced the clearance of indocyanine green (ClICG). A decrease in hepatic blood flow after propofol administration has been reported, but this is not a consistent finding. Studies in rats demonstrated that propofol infusion maintained or increased liver blood flow [2]. Similarly in dogs, Haber et al. [3] found that propofol administration did not affect hepatic arterial blood flow. It may well be that the finding of a reduction in liver blood flow after propofol administration is related to the method used to estimate the blood flow. The authors assumed that the hepatic extraction of ICG remained at 0.7 and was unaffected by their treatments. The authors did not include hepatic vein cannulation in their patients, and therefore it is impossible to assess whether temperature or propofol affected their intrinsic clearance of ICG. Lange et al. [4] have demonstrated that propofol interferes with the ClICG, decreasing this value by 54% at induction and by 38% during maintenance of anesthesia. This will make estimates of liver blood flow in the presence of propofol virtually invalid in the absence of hepatic vein blood samples for the intrinsic ClICG[5]. Previous authors have clearly stated that hepatic vein cannulation is necessary for hepatic blood flow estimates if the intrinsic clearance of an indicator dye, such as ICG, is affected by any aspect of the study [5,6]. It would appear that the effects of propofol on hepatic blood flow in humans remain to be clarified. This of course would require the use of a measurement technique for liver blood flow that is not influenced by the presence of propofol or the use of invasive hepatic vein cannulation. F. J. Lou Carmichael, PhD, MD, FRCPC Departments of Anaesthesia and Pharmacology The Toronto Hospital, Western Division Toronto, Ontario M5T 2S8, Canada
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