Intranasal ketamine for analgesia prior to digital nerve block- A double blind RCT!!??

Wow…

This was reportedly a double blind RCT of intranasal ketamine 50mg vs. saline placebo prior to performance of digital nerve blocks at a single centre in Iran. All the blocks were done by one doctor (listed as the third out of seven authors).

The primary outcome was reduction of pain during the block as measured on a visual analogue scale (VAS).

Results?

Exactly 100 patients were enrolled. Block pain was less in the group that got IN ketamine 28mm vs. 47mm (P less than 0.001) on the VAS. Side effects were reported to be “trivial.” This pain reduction persisted at the 45-minute mark at 21mm vs 43mm (P less than 0.001).

The authors conclude, “… IN Ketamine can be effective in reducing pain in patients with acute pain, without adding significant side effects.”

I doubt that many of us would consider giving ketamine prior to a digital nerve block. It does seem rather excessive and puts the patient at risk of side effects. (Reminds me of propofol for migraine) Perhaps we might consider inhaled nitrous oxide or intranasal fentanyl?

Unfortunately, there are a few problems and red flags with this study.

• The final study methods differ quite substantially from those listed in the trial registry found here.  The primary outcome was different, no power calculation, measuring tool different, etc.
• Intranasal ketamine burns and tastes bad. This could have unmasked blinding resulting in measurement bias.
• Data was collected in 2014. Why did it take 5 years to get published? I’m guessing it was rejected for publication from numerous journals.
• In the manuscript, there are numerous grammatical and spelling errors. What does a sloppy manuscript say about the conduct of the study?
• Why did patients continue to report substantial pain after the nerve block? Most of these blocks should have been successful at complete analgesia.
• Side effects were likely under-reported

Regardless of this study's conduct or limitations, I’m not a big fan of intranasal ketamine. Not great bang-for-buck and an undesirable side effect profile. In addition, we have experience with other drugs that are more efficacious.

Covering

Nejati A, Jalili M, Abbasi S, et al. Intranasal ketamine reduces pain of digital nerve block; a double blind randomized clinical trial. Am J Emer Med. 2019;27:1622-1626.