Ketamine for Pain Management

Abstract and Introduction

Abstract

An old anesthetic agent, ketamine is finding new use in lower doses for analgesic purposes. There are concerns stemming from its potential side effects—specifically psychomimetic effects. These side effects are directly related to dose amount. The doses used for analgesic purposes are much lower than those used for anesthesia purposes. A literature review was performed to ascertain potential side effects and/or adverse events when using ketamine for analgesia purposes. The search included CINAHL, PubMed, and Ovid using the search terms "ketamine," "ketamine infusion," "pain," "adverse events," "practice guideline," and "randomized controlled trial." Searches were limited to full-text, peer-reviewed articles and systematic reviews. Initially 1,068 articles were retrieved. The search was then narrowed by using the Boolean connector AND with various search term combinations. After adjusting for duplication, article titles and abstracts were reviewed, leaving 25 articles for an in-depth analysis. Specific exclusion criteria were then applied. The literature supports the use of ketamine for analgesic purposes, and ketamine offers a nonopioid option for the management of some pain conditions. Because ketamine is still classified as an anesthetic agent, health care institutions should develop their own set of policies and protocols for the administration of ketamine. By using forethought and understanding of the properties of ketamine, appropriate care may be planned to mitigate potential side effects and adverse events so that patients are appropriately cared for and their pain effectively managed.

Introduction

Currently approved as an anesthetic agent, ketamine is finding new use as an off-label analgesic showing promise for difficult-to-manage pain conditions and gaining application for acute postoperative pain management. Its attraction stems from its analgesic properties, potential to reduce overall opioid consumption, and hyperalgesia while still supporting respiratory and hemodynamic function. Conceivably, there will be an increased interest in using ketamine for its analgesic properties for chronic and acute pain conditions as more experience is gained with using it outside of the surgical arena. Concern stems from its potential side effects, though these may be anticipated, managed, and thus minimized. This paper seeks to provide a basic understanding of ketamine and its potential side effects and adverse reactions.

Background

Poorly managed pain may lead to many negative patient outcomes, such as longer hospital stays to manage acute postoperative pain, admission or readmission for pain management, decreased patient satisfaction, and increased cost of care (Coley et al., 2002, Joshi et al., 2014, Keller et al., 2016). Pain is also expensive. Gaskin and Richard (2012) noted that persistent (chronic) pain is estimated to cost the United States between $560-$635 billion per year in treatment and lost productivity expenses.

Anesthetic Medication Gaining Application as an Analgesic

Currently approved as a surgical anesthetic agent, ketamine is finding new use as an off-label analgesic showing promise for difficult-to-manage pain conditions such as complex regional pain syndrome (CRPS) (Niesters, Martini, & Dahan, 2014) and gaining application for acute postoperative pain management (Jouguelet-Lacoste, La Colla, Schilling, & Chelly, 2015). Findings suggest ketamine may potentially help prevent acute postoperative pain from transitioning into a difficult-to-manage chronic pain condition (McNicol, Schumann, & Haroutounian, 2014). Ketamine is an N-methyl-D-Aspartate (NMDA) receptor antagonist and is considered a dissociative anesthetic agent that in lower doses has analgesic properties (McNicol et al., 2014, Peltoniemi et al., 2016, Prommer, 2012). Its redistribution half-life is between 7 and 15 minutes and elimination half-life is between 2 and 3 hours (Lexicomp Online, 2016, Niesters et al., 2014, Peltoniemi et al., 2016). A realistic option for pain management, ketamine is attractive because it supports hemodynamic function and is not a respiratory depressant. Ketamine has shown promise for difficult-to-treat pain conditions, can be effective in reducing acute postoperative pain, and may reduce overall opioid consumption (Jouguelet-Lacoste et al., 2015, Niesters et al., 2014; Peltoniemi et al., 2016, Strayer and Nelson, 2008;). As with any medication, there are potential side effects, such as headache; sedation; psychomimetic issues such as increased visual and/or auditory disturbances; altered perception of the environment; and/or hallucinations, nausea, vomiting, and hypertension (Lexicomp Online, 2016, Peltoniemi et al., 2016). However, these side effects may be anticipated, managed, and thus minimized.

Purpose

The purpose of this paper was to perform a literature review of ketamine as a treatment for chronic and acute pain conditions, as well as common side effects and/or adverse reactions associated with its use.