Pain control is one of the primary responsibilities of an emergency physician. At our disposable are a variety of medications and procedures (nerve blocks, etc) we use at our discretion based on the severity of pain, effectiveness of analgesia, time to administer, and side effects of the treatment.
As an alternative to traditional analegesia (acetaminophen, NSAIDs, opioids), a systematic review of the literature on low-dose ketamine, otherwise known as subdissociative dose ketamine (<1mg/kg), for analgesia was recently published on Academic Emergency Medicine. Most of us have used ketamine for procedural sedation and as an induction agent for its dissociative effects, but it is not often utilized for analgesia.
In the review, four studies (all RCTs) were reviewed with the primary outcome being change in pain score and the secondary outcome being occurrence of adverse events such as vomiting or dissociation. 2 of the 4 studies reported significant reductions in pain while 1 study other study reported lower pain scores without absolute numbers. 2 studies demonstrated a reduction in opiate use by patients. A pediatric study reported increased vomiting with ketamine although this was not reported in adult studies.
Since this review, there have been new studies published and others are in the works. For now, subdissociative ketamine may be an alternative to or for pain refractory to traditional analgesia, possibly even for an unstable, hypotensive patient you want to give analgesia to prior to cardioversion. One recent study (3) recommends 0.3mg/kg for optimal analgesia. However, future RCTs are needed to describe its efficacy and safety.
Academic EM systematic review:
2. Low-dose ketamine vs morphine for acute pain in the ED: a randomized controlled trial.
3. Low-dose ketamine improves pain relief in patients receiving intravenous opioids for acute pain in the emergency department: results of a randomized, double-blind, clinical trial.