Clinical Experience, Characteristics, and Performance of an Acetaminophen Absorption Test in Critically Ill Patients.

Background: Altered drug and nutrient absorption presents a unique challenge in critically ill patients. Performing an acetaminophen absorption test (AAT) has been used as a marker for gastric motility and upper small bowel absorption; thus, it may provide objective data regarding enteral absorptive ability in critically ill patients.

Study Question: What is the clinical experience with AAT when used as a surrogate marker for enteral absorption in critically ill patients?

Study Design: This single-center, retrospective, cohort study evaluated serum acetaminophen concentrations within 180 minutes following 1-time enteral administration of an AAT. Patients admitted to the surgical and medical intensive care units and medical intensive care units over a 7-year period were evaluated. Groups were defined as positive (acetaminophen concentration of ≥10 mg/L) or negative (acetaminophen concentration of <10 mg/L) AAT.

Measures And Outcomes: The outcomes were to describe the clinical experience, characteristics, and performance of AAT.

Results: Forty-eight patients were included. Patients were 58.5 ± 14 years of age, mostly male (58.3%), and admitted to the surgical intensive care unit (66.7%). Median hospital length of stay was 47.5 (27-78.8) days. Thirty-four patients (70.8%) had a positive AAT [median concentration, 14 (12-18) mg/L]. Median time to first detectable concentration was 37 (33-64) minutes. AAT characteristics were similar between the groups including total dose, weight-based dose, time to first and second assays, drug formulation, and site of administration between groups. There were no independent risk factors identified on regression analysis for negative AAT.

Conclusions: An acetaminophen dose of 15 mg/kg with 2 coordinated serum concentrations approximately 30 and 60 minutes after administration is a reasonable construct for AAT. Future research is needed to assess AAT utility, safety, and clinical outcomes for predicting patient ability to absorb enteral feeds and medications.