Superstitions for the Everyday Anaesthetist

My iPhone autocorrect always changes “cancer” in reference to the nasty disease to “Cancer”, as if it assumes I’d much rather discuss the magical influences of stars clumped together by an imaginative eye. You know, rather than a thing that is actually a part of the real world.

I’m not going to go through the long history of astrology and culture but it’s fair to say it’s a tenacious concept. You don’t need to read the columns or watch late night psychic hotline shows to realise that once a concept drops anchors deep in the mind, it’s hard to shake off.

And while I’d like to boil a particularly nauseating brew of herbal tea to pour scorn on this from a great height, I’ve spent my career so far living with tenacious ideas in medicine that don’t quite hold. Which is why I’ve sometimes cracked the metaphorical knuckles just a little more when I come across a redhead.

The Special Status of the Flame-Locked Patient

Handing over information about a patient is the moment’s pause in the trapeze act. Words hang suspended waiting for the next person in the chain to reach out and grab them wholly. Missing the catch can have pretty grim consequences. So we want to get the vital details right.

Keep this in mind when I say that the words that sometimes get thrown out there can include:

“This patient’s a redhead.”

And it’s not entirely a joke.

Because a barely related photo of an orang-utan would have been too obvious. [Via Wikimedia commons and Marshmallowbunnywabbit]

Because a barely related photo of an orang-utan would have been too obvious. [Via Wikimedia commons and Marshmallowbunnywabbit]

Redheads. Maligned and nicknamed all for the cruel joke of being born with a skin shade perfectly designed for moon travel. Why would we care for a second when we’re planning an operation though?

Well it’s not about colour matching operating theatre fashions. It’s because redheads are just known trouble. Harder to place a cannula in the vein. More likely to be “fiery”. Prone to post-operative craziness. Known bleeders when it comes to the sharp cutting bit of proceedings. And most importantly for an anaesthetist, resistant to the effects of pain relief and anaesthesia.

While it’s not quite a superstition to make a doctor spit on the ground or carry salt for a quick shoulder throw, there’s a slight edge to the observation. And every time something goes not quite right for a redhead, the collected wisdom of redheads being a challenge gets a little more wizened. It’s all a bit unfair for any orange-tonsured innocents.

The Mutant Redheads

Why would we even think this? Well it does start with a tiny bit of reality. Red hair isn’t a matter of melanin, but a result of a mutation in the melanocortin-1 receptor gene. So the red hair isn’t just a variant of the standard pigment. It’s more of a unique and special snowflake situation. And sometimes genetic differences correspond with different interactions with drugs.

Lots of different observations have helped give the story of the difficult redhead the kernel of academic respectability that lets a superstition really take hold. These come from both animal and human research and are quite nicely touched on in an editorial in the latest Canadian Journal of Anaesthesia.

Some previous work has shown that redheaded women needed 19% more of a particular type of anaesthetic to be prevented by moving from a big electrical stimulus. That’s not quite the same as surgery, but it is interesting. Mice with the melanocortin-1 receptor gene knocked out also seem to need more anaesthesia to stop movement to a noxious stimulus. Redheads don’t seem to get the same results from local anaesthetic under the skin either.

Add all these vaguely suggestive yet isolated observations, particularly with an easily identifiable marker, and the suspicion that redheads are trouble has a good chance to take hold. Of course, we still haven’t provided much of a biological explanation for why there should be any difference when it comes to redheads and anaesthesia.

Multitasking Receptors

Those melanocortin-1 receptors turn up in various parts of the brain, although the central nervous system is not that blessed with them overall. What is more apparent is the overlap amongst the melanocortin receptors and this family of receptors are often coupled up with opioid receptors, the same ones that some of our stronger analgesics work on, throughout the brain and spine. So one suggestion is that there’s an antagonistic relationship between the two, where an activated melanocortin receptor doesn’t let an opioid do it’s job.

It’s a link, but it could do with a bit more flesh on it. And it needs a bit of evidence that we’re trying to find this flesh because of a real world issue.

Leaving the Mice Behind

Ginger-hued mice are probably wonderful, but the real issue for an anaesthetist relates to the possibility that human redheads are less likely to respond to pain relief medicine and more resistant to the soporific song of our anaesthetic agents. This combination sounds like something that might put a patient at greater risk of being aware of what is going on during an operation. Having people aware is pretty much the opposite of what we’re aiming for with a general anaesthetic of course.

Fortunately a group from the US were interested enough to take their bigger research on awareness during operations and specifically look at the influence of those pesky red hairs. It’s the sort of comprehensive effort that you’d expect from work which includes methodology gems like a ‘greedy matching algorithm’ (which incidentally is now the name for any future band I might be involved with).

From their larger study sample of 5713 patients, 319 reported they were natural redheads. When looking at this particular group there was no observable difference in the rates of awareness. Of course awareness isn’t that common so they may just not have had enough subjects to be certain. Nevertheless, there wasn’t a stark and obvious difference to be found.

The authors go further than that. They couldn’t find any advance that anaesthetists altered their approach to the anaesthetic for the ginger population. Nor was there any clinically significant difference in the apparent depth of hypnosis or any of the significant things that plague patients in the time after they wake up from the operation.

So basically redheads just weren’t that special when it came to the serious drugs. Embrace sweet normality, ginger comrades.

Same, Same

It’s just one paper but at least there’s some reassurance on offer for redheads – they’re not that likely to have a tougher trip through their anaesthetic and they probably haven’t been receiving some form of drug discrimination.

More broadly this reminder that we don’t need to eye redheads with suspicion should also tell us something about tales handed down between generations. They shouldn’t be assumed to be true. Some of them don’t even have a basis in even a handful of observations.

For as much as I’d say it’s important to build the experience of clinician into any evaluation of evidence in medicine, sometimes that experience only brings with it old superstitions.

The algorithm for superstition could sometimes be written as:

Chance physical trait + one off experience + potential biological pathway = superstitious “fact”.

Happily evidence-based medicine should self-correct as long as people are asking questions. Because if we just accept the old stories we get told, we might as well start asking the stars for pointers.

References:

The editorial referred to is this one:

Sessler DI. Red hair and anaesthetic requirement. Can J Anaesth. 2015 Feb 15 [Epub ahead of print] 

The article in all its glory is

Gradwohl SC, Aranake A, Abdallah  AB, et al. Intraoperative awareness risk, anaesthetic sensitivity, and anaesthetic management for patients with natural red hair: a matched cohort study. Can J Anaesth. 2015 Feb 14 [Epub ahead of print]

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