Intravenous Ketamine for Pain Control in First-Trimester Surgical Abortion: Interim Analysis of a Randomized Controlled Trial

Abstract

Objectives: Surgical abortion is common, with most completed in the first trimester. Gold standard pain control is intravenous (IV) fentanyl and midazolam, requiring continuous cardio-respiratory monitoring, a potential challenge where this monitoring is unavailable. Ketamine is a sedative and analgesic without the cardio-respiratory depression risk associated with IV opioids, representing a potential alternative. Investigating non-opiate pain control methods is imperative given the context of the opioid crisis. This is an interim analysis of 45 participants from a randomized controlled trial comparing IV ketamine, oral morphine, and IV fentanyl for pain control in first-trimester surgical abortion. We hypothesize that ketamine will provide better pain control than morphine.

Methods: This is a double-blind, single-centre superiority trial of 3 parallel groups. Participants were ≥18 years old with confirmed intrauterine pregnancy of gestational age <12 weeks. Pain was assessed using the Visual Analogue Scale and the Wong-Baker Faces Pain Rating Scale.

Results: In total, 2 participants were excluded post-randomization for 43 treated. Findings indicate that ketamine (n = 14; M = 0.7; 95% CI 0.1-1.3) provides better intra-operative pain control than morphine (n = 15, M = 4.4, 95% CI 2.9-5.9) and fentanyl (n = 14; M = 4.3; 95% CI 3.0-5.6; P < 0.001). The ketamine group was more satisfied with the anaesthetic method than the morphine group (P = 0.017). No group experienced serious adverse events.

Conclusions: Findings support continuation of the randomized controlled trial and highlight ketamine as a compelling non-opiate pain control option in first-trimester surgical abortion. Ketamine use may represent more optimal pain control in settings where continuous cardio-respiratory monitoring is unavailable.

Keywords: abortion; anesthetics; fentanyl; induced; ketamine; morphine.