“Redheads Need More Anesthesia” – Fact Or Fiction?

RK.md

The notion that natural redheads need “more anesthesia” and/or are resistant to certain medications has been spread by the media (ie, Time Magazine and The New York Times), the scientific literature, and even seasoned anesthesiologists who (anecdotally) claim this to be true.

The “basic science” behind this stems from the high prevalence of allele mutations in redheads in the melanocortin-1-receptor (MC1R) gene. Normally this receptor stimulates eumelanin production in melanocytes. These mutations favor the production of pheomelanin which is responsible for the red hair, lighter skin, etc. Interestingly, subtypes in this receptor family are also expressed in the central nervous system and may antagonize opioid pathways leading to variations in the experience of pain. We still don’t know all the details!

Surgical general anesthesia (GA) must address four primary components: unconsciousness, memory, pain, and movement. These are better known as hypnosis, amnesia, analgesia, and immobility, respectively. I use a combination of volatile gas anesthetics with intravenous medications to confer the aforementioned state. As with anything else in medicine, every patient is different based on their age, comorbidities, etc… but does red hair actually make a difference? Let’s look at the literature.

In 2004, Liem et al. showed that in a head-to-head comparison of 20 healthy women, the redhead phenotype required a higher alveolar concentration of desflurane to not “feel” an electrical stimulus (a surrogate for minimal alveolar concentration, or MAC). However, almost a decade later, the same institution found that specifically with propofol, the most common IV hypnotic I use, redheads exhibit similar pharmacokinetics/dynamics to dark haired individuals.

Myles et al. performed a prospective, matched cohort study with a larger sample size (468 healthy adults) receiving inhaled GA with subsequent multivariate analysis showing that there was no significant difference in recovery times/pain scores in redheads accounting for what drugs/doses were used.

Remember that anecdotes are not data. Enough said.

We are still early in understanding how inhaled anesthetics actually work at the lipid bilayer, membrane protein level. Perhaps future research will examine if specific redhead-associated allele mutations do indeed affect the functional mechanism of anesthetics. Until then, this “myth” is just that. I do NOT change my anesthetic plan just because someone is a redhead.