Predicting immunosuppressant dosing in the early postoperative period with noninvasive indocyanine green elimination following orthotopic liver transplantation

Twenty adult patients undergoing orthotopic liver transplantation (OLT) were enrolled in this study, with the noninvasive indocyanine green plasma disappearance rate (ICG-PDR) measured both during and after OLT to assess the relationship between ICG-PDR and the ability of patients to achieve therapeutic postoperative tacrolimus immunosuppressant blood levels. Liver function was determined at both 2 and 18 hours post reperfusion with the ICG-PDR k value (1/min). Postoperative standard serum measures of liver function as well as liver biopsies were also collected and analyzed. The median ICG-PDR k value for the study group at 2 hours post reperfusion was 0.20 (0.16, 0.27), whereas at 18 hours post reperfusion, it was 0.22 (0.18, 0.35). The median change in the k value between the two ICG-PDR measurements was 0.05 (- 0.02, 0.07) with P= 0.02. There was an interaction between the postoperative day 1 (18 hours post reperfusion) ICG-PDR k value and the linear increase in the tacrolimus blood level, such that the greater the k value was, the more gradual the observed rise was in tacrolimus over time [that is, the longer it took to achieve a therapeutic blood level (>12 ng/mL), P = 0.003]. Of the 16 patients that received tacrolimus, comparable dosing on a per kilogram body weight basis was observed. Also, no significant association between ICG-PDR k values and postoperative liver biopsy results was seen. This study demonstrates that the ICG-PDR measurement is a modality with the potential to assist in achieving adequate blood levels of tacrolimus following OLT.