Patient Factors Associated With Subanesthetic-Dose Ketamine Infusion in the Postanesthesia Care Unit

A multi-modal approach to pain control, including subanesthetic-dose ketamine infusion (SDKI), may improve postoperative pain management, especially in patients with opioid tolerance. Identifying preoperative patient characteristics associated with receiving SDKI in the postanesthesia care unit (PACU) may help clinicians anticipate which patients could benefit from timely SDKI.

This study was designed to examine preoperative patient characteristics associated with SDKI in the PACU.

Retrospective cohort study of consecutive adults (≥18 years) undergoing scheduled surgery between January 1, 2020, and December 31, 2021, at a large academic medical center. Demographics, opioid use history, mental health diagnoses, and surgical service type were extracted from the electronic health record. A stepwise regression model was used to identify patient characteristics associated with SDKI in the PACU.

Among 6,419 patients, 90 (1.4%) received a SDKI in the PACU. Predictor variables in the final model included age (p = .031), White race (p = .014), history of psychoactive substance use (p < .001), prescribed morphine equivalent daily dose (MEDD) ≥60 mg (p = .0019) or ≥90 mg (p = .0018), and orthopedic/neurological surgery (p = .0079). Patients prescribed an MEDD ≥60 mg or ≥90 mg had nearly fourfold higher odds of receiving SDKI, whereas those with a history of mental and behavioral disorders due to psychoactive substance use had approximately threefold higher odds.

Preoperative screening for these characteristics in patients undergoing scheduled surgery may help identify patients who could benefit from proactive SDKI therapy in the immediate postoperative period.