The addition of intranasal ketamine, administered by paramedics, to usual treatment with nitrous oxide was found to alleviate acute pain and improve comfort within 30 minutes, according to a study published in the Annals of Emergency Medicine.

Researchers conducted a randomized double-blind study of 120 out-of-hospital patients (aged ≥18; median age, 54) with acute pain (ie, verbal numeric rating scale [VNRS] pain score ≥5). The primary study outcome was a reduction in VNRS pain score ≥2 points (deemed clinically significant), 30 minutes after treatment administration (nitrous oxide plus intranasal ketamine or nitrous oxide plus intranasal placebo; n=60 for both).

All study participants were offered nitrous oxide, per existing paramedic protocols, but 27% and 25% of patients in the intranasal ketamine and placebo groups, respectively did not receive it. A total of 76% vs 41% of patients who received intranasal ketamine vs placebo, respectively reported a ≥2-point reduction in VRNS score at 30 minutes (difference, 35%; 95% CI, 17%-51%). Median VNRS reduction in the intranasal ketamine group was 2.0 and 3.0 at 15 and 30 minutes, respectively, compared with 1.0 and 1.0, respectively, in the placebo group.

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In the intranasal ketamine group, 62% of participants reported adverse events compared with 20% in the placebo group (95% CI, 49%-73% and 95% CI, 12%-32%, respectively). However, these adverse events were minor, requiring no intervention.

Study limitations include the use of a single-site location, which may limit generalizability. In addition, as some patients did not receive nitrous oxide, the conclusions drawn regarding the effect of additional ketamine are limited.

“Because [the] use of…opiates is not available to primary care paramedics, they are limited to the use of inhaled nitrous oxide as an analgesic. This results in a significant burden of uncontrolled pain for patients,” noted the study authors. “In this study, primary care paramedics were able to use intranasal ketamine analgesia effectively and with apparent safety.”

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Andolfatto G, Innes K, Dick W, et al. Prehospital analgesia with intranasal ketamine (PAIN-K): A randomized double-blind trial in adults [published online March 26, 2019]. Ann Emerg Med. doi:10.1016/j.annemergmed.2019.01.048