(Last Updated On: January 25, 2016)

Background/Motivation

A healthy 38yo male presents with anterior left shoulder dislocation. No known history of opioid use, pain scale 8/10 and he appeared uncomfortable. When discussing pain management, the Attending suggests we begin with morphine and use ketamine as an adjunct.

I wondered why not just start with ketamine first as it has been known to have analgesic properties in low doses.

Article

Motov S et al. Intravenous Subdissociative-Dose Ketamine versus Morphine for Analgesia in the Emergency Department: A Randomized Controlled Trial. Annals of Emergency Medicine 2015. PMID: 25817884

Design

Prospective, randomized, double-blind trial in 711-bed community teaching hospital over 1 year. 90 adult patients total enrolled in study   

Inclusion: age 18-55, acute flank/back/abdominal pain, pain scale >5 out of 10 on numeric rating scale, acute pain defined as onset <7 days

Exclusion: pregnancy, breastfeeding, altered mental status,allergy to morphine or ketamine, weight <46 kg or > 115 kg, unstable vital signs (systolic blood pressure<90 or >150 beats/min), medical history of acute head or eye injury, seizure, intracranial hypertension, chronic pain, renal or hepatic insufficiency, alcohol or drug abuse, psychiatric illness, recent (4 hours before) opioid use

Standard Analgesia: Morphine 0.1 mg/kg

Modified Analgesia: Ketamine 0.3 mg/kg

Outcomes

Primary: reduction of pain at 30 minutes from medication administration

Secondary: incidence of rescue analgesia at 30 or 60mins

Findings     

  • Pain scores at time 0 were similar in the 2 groups.
  • The mean difference in pain numeric rating scale score for ketamine versus morphine was 0.1.
  • At 15 mins more patients given ketamine reported complete resolution of pain from 8.6 to 3.2.
  • Change in mean pain scores was not significantly different in ketamine and morphine groups 8.6/8.5 at baseline to 4.1/3.9 at 30 minutes.

Adverse Effects:

  • More patients who received ketamine experienced adverse effects: dizziness (20%), disorientation (27%), mood at 15 minutes but no clinically concerning side effects.

Discussion points:

  • Sample size was small and did not reach minimal sample size for adequate power
  • Increased adverse effects of dizziness and disorientation in the ketamine group
  • Ketamine group had higher complete resolution of pain (44%) than morphine (13%) at 15 mins
  • At 30 mins, ketamine group (4) required more rescue medication versus morphine group (0).
  • Future studies should look at appropriate dosing with minimal adverse effects

Summary

Giving low dose ketamine 0.3mg/kg for acute pain is as effective as morphine 0.1 mg/kg at 30 minutes.

Application to our practice

Previous studies have examined Ketamine as an adjunct to opioids using 0.3mg/kg ketamine dosing[1]. This study examines ketamine use alone at low dose as initial agent for pain management.

My opinion – Glad to see similar pain relief between groups but concerned about the greater adverse effects in ketamine group.  The adverse effects resolved after 30 minutes, but the patients still experience them.

I want more studies investigating the appropriate dose of ketamine that improves pain without the adverse effects.  Also, there were a lot of exclusion criteria in this study so not as applicable to the general ED patient.

I plan to use ketamine as initial analgesic for future young healthy patients with no medical problems that present with acute pain.  

Patience Ngwang, MD University of Illinois at Chicago Chief Resident Medical Education

 

 

 

Dr. Lesueur is a current Chief Resident at UIC’s EM Program.

Click to Read Attending Response - Dr. Michael Joo

Thank-you Patience for including me in the knowledge bomb.  Nice summary above.  Here are my thoughts on the paper and use of ketamine for analgesia.

This study provides evidence that ketamine may be used for initial pain control without the use of opioids or as an adjunct to opioid use.  Below are patient populations that I believe will benefit the most from use of ketamine.

  1. Groups where respiratory depression is a concern due to other underlying disease.  Examples include morbidly obese patients, OSA patients, patients with underlying lung disease and baseline hypercarbia and hypoxia, or patients with difficult airways.

  2. Opioid-naive patients.  Goal is to give LESS opioids.  Ketamine may be given first and then give lower doses of opioids as needed for tighter pain control.

  3. Patients that require immediate pain relief such as fractures/dislocations prior to taking to imaging studies.  Ketamine offers quick pain control and fast metabolism with low risk of cardiovascular and respiratory compromise.  There is less of a requirement to set-up complicated monitoring

  4. Soft/hypotensive patients that require pain control, but fentanyl is not having desired effect.

A couple of notes about use of ketamine.  It is essential to know the dosages and how to administer appropriately; confidence in these areas will greatly reduce the fear of other staff.  Nursing staff may be hesitant to give ketamine as a pain adjunct since it is viewed as a “conscious sedation” drug.  Remember that the dosing is sub-dissociative dosing and it is safe to use without the usual processes involved in conscious sedation.  To help use ketamine in this manner, maintain good support from pharmacy, hospital directors, and anesthesiology department and continue nursing education in the ED.

Joo

 

 

Dr. Joo is currently an attending physician at Mercy Hospital and Medical Center.

 

References

Low-dose Ketamine improves pain relief in patients receiving intravenous opioids for acute pain in the emergency deparment: results of a randomized, double-blind, clinical trial. Beaudoin FL, Lin C, Guan W, Merchant RC. Acad Emerg Med. 2014