Elevation of Preoperative Ammonia Level Is Not Associated With the Incidence of Postoperative Delirium in Patients with Liver Transplantation: A Propensity Score Matching Analysis

Introduction: The preoperative elevation of ammonia may be associated with postoperative neurologic complications. The aim of this study was to evaluate the effect of preoperative ammonia level on the incidence of delirium in patients after liver transplantation (LT).

Materials and methods: Patients (n = 260) who received LT from January 2010 to July 2017 in a single university hospital were retrospectively reviewed. The patients' demographic data, perioperative managements, and postoperative complications were assessed. Patients were divided into the following 2 groups: those who had a preoperative elevation (Group A, n = 158) and those with a normal range (Group C, n = 102). The cut-off value for a normal serum ammonia level in our hospital was defined as 32 μg/dL.

Results: After propensity score matching, there was no difference in the incidence of delirium between the groups (P = .784). Delirium occurred in 8 of 68 (11.76%) patients in Group A and 7 of 68 (10.29%) patients in Group C after LT. In addition, there was no difference in the incidence of delirium between the groups, even patients were categorized based on serum ammonia levels into 3 groups as follows: < 32 μg/dL (28/158 [17.72%]), 32 to 65 μg/dL (28/158 [17.72%]), and >65 μg/dL (28/158 [17.72%]) (P = .134).

Conclusions: The preoperative serum ammonia level was not related with the incidence of postoperative delirium. The high elevation group, especially those with greater than 65 μg/dL of preoperative ammonia, was also not related with the incidence of delirium. However, our study is limited by its retrospective design, so future prospective studies are needed.