06 May 2021
In today’s #KYJ we look at this rare immunisation complication. Shoulder injury related to vaccine administration (SIRVA) seems like a no brainer.
Your flesh was pierced with a sharp implement then an immunogenicity fluid was squirted inside your shoulder/upper arm... yeah, that’s likely to hurt a little. But how long? Within 48-72 hours any pain from a vaccine given into your deltoid should be resolved.
But for a tiny number of vaccine recipients, their arm develops a disproportionately large quantity of pain and swelling. The pain is not resolving at the 24-48 hour mark, but actually worsening or just starting at 24 hrs post shot. In these rare cases, the inflammation of their shoulder joint structures is more likely. It’s called SIRVA and is a shoulder injury related to vaccine administration (literally) but there is usually a trigger.
Most cases of SIRVA occur when the vaccine has been given outside of the safe triangle of the deltoid. Given too high or too low and there is serious risk of tendon or worse, ligament and bursa injection. These structures are tough and fibrous, so plunging even a small volume of vaccine into these tight dense structures causes one of two things: First is the hydraulic damage of forcing fluid into a tiny compartment.
This tears and stretches the structure causing bleeding and the inflammatory repair process to be initiated. Pain is often immediate, and the person shows discomfort during administration. The second issue is more sinister. It related to a pocket or bubble of vaccine being forced into a dense structure that raises the internal compartment pressure above perfusion pressure. This slows blood supply to that tissue causing first ischaemia then necrosis in much the same way as a pressure sore on a persons heel or bum. It is a pressure injury, just internal. This is a form of compartment syndrome.
As tissues die, they are again subject to the whole inflammatory process. In very rare cases the injection may be way too high and cause rotor cuff injuries, or be right into the joint bursa. This causes a bursitis that can last weeks So... SIRVA is rare.
It’s not the usual sore arm post injection that 50-60% of people experience .
It’s ongoing worsening pain lasting more than 72 hours post injection. Avoiding SIRVA is best achieved by ensuring that the safe triangle approach to arm injections is used. The deltoid is a meaty triangular (delta) shaped muscle. Grab it and stab it in the middle, and you can’t go wrong. Most vaccines use a 25g needle. You need to know your length. 90 degrees, and all the way for a 25mm 25g.
If you’re using a long shank 25g or a standard 23g then 2/3 to 3/4 of the needle length is good. If you hit bone (and you will at least once in your career) pull back a mm or two before injecting. Inject slow. A flu shot or tetanus, should take 3-5 sec. Too fast and you will stretch muscle and potentially tear fibres.
This lady had a convenient tattoo on each arm to remind her kids and partner where to inject prochlorperizine during migraine episodes. I thought that was cool. Don’t forget your flu shots . At least 2 weeks between flu and Covid shots.... perhaps go 3 just to be sure.