Written by Matt Lipton
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For acute non-specific low back pain (LBP), intradermal sterile water injection (ISWI) + IV NSAID reduced pain and improved patient satisfaction vs IV NSAID alone.
Why does this matter?
Nonspecific low back pain can be quite unsatisfying to treat in the ED. Is there a way that we can decrease the patient’s pain with more than a shot of ketorolac? The authors investigate a new, simple procedure to decrease pain and increase patient satisfaction by injecting sterile water in the region of maximal pain.
Are you sure they are using just water?!
This was a prospective RCT with 112 patients equally split into 2 groups; everyone received an IV NSAID, but the intervention group received the ISWI. As for the details of the procedure, they used a 26-gauge, 0.5 inch insulin syringe to inject 0.1cc sterile water in a square pattern (each side was 3cm) around the area of maximal pain. Each injection created a small skin wheal, similar to a TB skin test. See image below from the article for reference. At 10 min post-ISWI, the patient’s pain was significantly improved, and the pain relief persisted for 24 hours (still statistically significant). Interestingly, the authors note that this procedure has been shown effective for other painful conditions of the back, such as kidney stones and LBP from labor. Finally, the authors state that other studies have shown less reduction in pain if the procedure was performed with sterile saline!
As for ED patient satisfaction? The ISWI group was highly satisfied 88% of the time, compared to the control group, which was highly satisfied only 16% of the time.
After reading this article, I feel like I don’t actually understand anything about pain. Although I still have a hard time accepting the results of this well-done study, this is a potentially practice-changing paper for me. Since this is an essentially risk-free intervention (with the exception of brief pain) with potential significant benefit, I will offer the ISWI procedure to nearly all my ED patients with acute lower back pain.
Pro tip: Many EDs stock vials of 10cc of sterile water that you can order. This is more practical than using a 1000cc bottle of sterile water and throwing away the unused 999.6cc.
From cited article
Source
The effectiveness of intradermal sterile water injection for low back pain in the emergency department: A prospective, randomized controlled study. Am J Emerg Med. 2021 Apr;42:103-109. doi: 10.1016/j.ajem.2021.01.038. Epub 2021 Jan 20.
Reviewed by Clay Smith
Placebo effect?
My guess is that the effect is likely due to inhibition of C-fibers due to the stimulation of A-beta fibers and release of endogenous opioids triggered by the transdermal injection. Interesting concept that may have utility in a variety of painful conditions!
In the latter 80s I worked for a month with a neurologist Dr. Payne (really) who would go weekly to the VA to treat the gentlemen there.
He would put a few cc of sterile water into a syringe, tell them “this is just water, you know” and with desperate voices they’d said “I know, cmon!” And he’d rapidly stab and inject their trapezius in multiple sites, putting a small amount of water at each site. They were go grateful.
He/I found it fascinating. He told me that it got great results for some chronic pain patients. He mused out loud: was it the water really affecting the nerves? Acupuncture? Placebo? Mechanical damage to the sites triggering a reaction? We never settled the question. But, again, this was 25+ years ago…