A busy hockey weekend delayed this topic. I thought this would be a quick one, but there are some interesting and complex issues…and as we move deeper into the vaccination series, there’s even less information on which to base decisions.

This post deals with issues surrounding vaccination at or near the time of surgery. Typically, we try not to load up on different procedures at the same time, but sometimes surgery may coincide with optimal timing for vaccination, or the time of surgery might be one of the few (or only) times an animal is seen by a veterinarian and thus the only opportunity to vaccinate (e.g. trap/neuter/release programs, barn cats).

When thinking about if/when/how to vaccinate, we need to consider a variety of factors, including impact on vaccine efficacy, risk of adverse events, ability to detect and manage adverse events, and practical components.

In humans, there’s no clear evidence that vaccination at the time of surgery is associated with a poorer vaccine response or increased risk of adverse events. An older review of the effects of anesthesia on vaccinationin children (Seibert et al. 2007) stated “We conclude that the immunomodulatory influence of anesthesia during elective surgery is both minor and transient (around 48 h) and that the current evidence does not provide any contraindication to the immunization of healthy children scheduled for elective surgery. However, respecting a minimal delay of 2 days (inactivated vaccines) or 14-21 days (live attenuated viral vaccines) between immunization and anesthesia may be useful to avoid the risk of misinterpretation of vaccine-driven adverse events as postoperative complications.”

The latter part of that statement is a common recommendation, i.e. avoiding vaccination close to the time of surgery to avoid situations where there’s a try to differentiate whether a fever or other non-specific issue is the result of a developing post-surgical complication (that might lead to something more serious and needs more investigation) or a common typically transient vaccine reaction (that might just need a dose or two of an anti-inflammatory). That’s relevant to veterinary procedures to some degree, but probably a lot less than in humans, since we don’t tend to recognize mild reactions like malaise as commonly or easily in our patients. It’s still something we have to consider if a patient has a surgery and a vaccine, and is a little bit off the next day… is something brewing, or is it just from the vaccine? However, I’d say those circumstances are pretty rare.

My take home message is that it’s probably better to space out surgery and vaccines if we can, but we don’t want to miss an important opportunity to vaccinate. If there’s concern that we might not see the animal again, I’d vaccinate (especially for an important vaccine that is needed asap). If the owner is committed to bringing the animal in later (e.g. we can vaccinate at the time of suture removal or shortly thereafter), then that’s probably ideal. However, we don’t want to let perfection to be the enemy of the good, so we should err on the side of making sure the vaccine gets administered, one way or the other.

So if we decide to vaccinate around the time of surgery, when do we do it?

  • Before surgery?
  • After the procedure but while still under anesthesia?
  • During anaesthetic recovery?
  • After the animal is awake but before the animal goes home?

Here are my thoughts:

Before surgery

  • Nope. The procedure is probably more important than the vaccine. We don’t want to risk having to abandon the procedure because of a vaccine reaction. There’s also the potential that any less serious reaction could impact response to anaesthesia, particularly blood pressure.

After the procedure while still under anesthesia

  • The pros are it’s easy to vaccinate an unconscious animal. We likely still have airway and IV access in the rare event that something really bad happens.
  • The cons are we can’t necessarily identify reactions as effectively if the animal is not fully awake.
  • I’ve seen some guidance on vaccination during anesthesia in humans that recommends avoiding vaccination under anesthesia apart from some select circumstances (e.g. certain developmental or behavioural disorders, or people with extreme anxiety or needle phobia). The analogy in the veterinary world would be an animal that is very difficult to handle and vaccinate, and the risks to the animal and handlers from vaccination while the animal is conscious outweigh any minor concerns about vaccination during anesthesia (e.g. vaccination of feral cats).

During anaesthetic recovery

  • There’s a lot of overlap between this option and vaccinating while the animal is still fully anesthetized (see above). We still hopefully have IV access (but not necessarily, depending on the clinic and procedure), so it’s easier to manage a serious complication. However, anesthetic recovery is already a complex time physiologically and it might be harder to identify early signs of an adverse reaction.

After the animal is awake but before the animal goes home

  • The pros are the animal has recovered from anesthesia and is getting back to normal physiologically, and we have a better ability to detect any complications that develop. The cons are the animals has to be handled more and poked after going through a procedure. Those concerns are minor for most animals, but the additional downside (which may be the main issue) is probably logistics and the risk of forgetting to give the vaccine.

Considering all these factors, it probably makes the most sense to vaccinate after anesthetic recovery, as long as the animal can be safely handled. Ideally that’s well after anesthetic recovery, but not as the patient’s walking out the door, so there’s a bit of time to observe the animal after vaccination. If the animal is getting an anesthetic in the morning, and is going home in the evening, vaccination an hour or two before discharge might be the sweet spot.

Like a lot of issues pertaining to vaccination, our decisions should be based on consideration of costs and benefits, but are complicated by the fact that we have almost no hard data on those costs and benefits. Some common sense can guide us; while I think my comments above are pretty reasonable, they are undeniably light on evidence.