BACKGROUND: The effect of liver resection on acetaminophen metabolism and whether it is affected by residual liver volume is poorly understood.
METHODS: We investigated the effects of liver resection on acetaminophen metabolism in a single centre, prospective observational, case-control study of inpatients. Patients undergoing liver resection were administered therapeutic post-operative acetaminophen. Glutathione and urinary acetaminophen metabolites were measured over the first three post-operative days and compared between patients with low (Group A) and high (Group B) residual liver volume.
RESULTS: 41 patients (41% female, median age 62 [IQR 53-72] years) were included. Mean urinary cysteine levels increased significantly from post-operative day 1 to 2 (578.0mg/day 95% CI 478.9-677.1 vs. 775.4mg/day, 95% CI 625.7-925.1; p=0.03). Group A (n=11) had significantly higher median levels of cysteine (day 1, 464.3mg/day [IQR 355.6-582.0]; day 3, 717.6mg/day [IQR 423.5-1104.0]) compared to Group B (n=11): day 1, 545.4mg/day (IQR 346.9-843.5); day 3, 508.1mg/day (IQR 390.8-788.4; p=0.048). No significant difference was observed in glutathione or 5-oxoproline levels between the groups.
CONCLUSION: Low residual liver volume results in altered acetaminophen metabolism, however, no evidence of glutathione deficiency was observed. Therapeutic acetaminophen is safe after major liver resection provided liver function is adequate.