Over the last decade, ketamine has shifted from pariah status to celebrity, increasingly popular for procedural sedation, delayed-sequence intubation, treatment of intracranial hypertension, and even status epilepticus. There is also a smattering of trials demonstrating its use for inpatient post-operative patients as an opiate-sparing mechanism – but how well does it work in the Emergency Department?
These authors from Brown evaluated use of ketamine for adjunctive pain control in a small, three-arm prospective, blinded comparison between “usual care”, and two doses of ketamine. Patients with severe acute pain received 0.1 mg/kg of morphine up to 10mg, followed either by placebo injection, 0.15 mg/kg ketamine, or 0.3 mg/kg ketamine. Patients were then followed for need of rescue medication.
With only 20 patients in each group, the potential for type I and type II errors are substantial. All groups derived substantial pain relief from treatment. Patients in the two ketamine groups, however, derived a greater degree of relief – and required a lower gross amount of rescue analgesia. The authors eke only a few “statistically significant” p-values out of their tiny samples, but, regardless, the underlying differences likely appropriately reflect an expected acute analgesic effect from ketamine.
Unfortunately, the largest limitation of the small sample concerns the incidence of adverse events. The largest dose of ketamine, 0.3 mg/kg, had clearly distressing effects – half the patients felt dizzy – while both ketamine groups included a handful of patients with nausea, vomiting, and confusion. On the flip side, two patients in the standard-care group suffered possible morphine-related hypotension and respiratory depression as a result of rescue analgesia.
Ketamine may have a role in acute analgesia in the Emergency Department. However, appropriate dosing and ideal patient selection remain unclear.
“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”
http://www.ncbi.nlm.nih.gov/pubmed/25377395
In my own hands, low dose ketamine administered as a bolus frequently causes distressing symptoms. However, slower administration (over 3 to 5 minutes) seems to minimize these symptoms but still allows for pain relief.
Why are we trying to fix something that is not broken?
There is nothing wrong with judicious use of short acting opiates for acute pain in the ED. Fentanyl and other opiates are a known entity, completely reversible, titratable, generally effective and very safe when given in appropriate doses. Sure there is the odd patient where an adjunct might be needed. But this is quite unusual. Why are we trying to "spare" opiates. Crazy…
So lets replace a well known drug with something that is less studied and has a miserable side effect profile. A significant portion of patients I see who have been given prehospital low dose ketamine have altered mental status. This impacts our ability to care for them and may actually increase resource utilization as more get pan-scans etc.
I also wonder how we can use a self reported pain score (VAS or NRS) in patients with altered mental status?
I love ketamine for procedural sedation and induction for DSI or RSI. But for other purposes, I think side effect profile is intolerable given other choices for analgesia. Clearly the enthusiasm exceeds the science.
We use CRIs of ketamine with fentanyl +/- lidocaine routinely in pets who have significant pain.
It is not uncommon for me to have trouble obtaining adequate pain control in certain populations in the ED. I think having an adjunct to use in these cases is very helpful. I've had luck with putting the 0.3 mg/kg in a 100cc saline bag and infusing it as a piggyback to prevent side effects. In the future we will look back on our current pain treatment options as primitive. Just because we've managed patients effectively by pummeling the opioid receptor in the past does not mean we should not be looking for new targets.
Awesome comment – and a great perspective.
As with nearly everything in medicine, characterizing anything as "never" or "always" is a recipe for disaster. Should ketamine be used routine as an adjective therapy? Probably not. Are there patients for whom escalating doses – even of safe, short acting – opiates are providing inadequate relief or safety margin? Certainly. Is ketamine a reasonable option? I think, based on studies like this, it is. But, clearly, it's not a _great_ option, and it has the potential for – if not harms – a clinically important incidence of mild adverse effect.
I've tried this a few times – mostly attempts to avoid hospitalization in sickle cell crises-like events – and I've had decidedly mixed results.