There is a common belief that redheads require more anesthesia for surgery than non-redheads. (1–6) They may also be resistant to local anesthetics, such as lidocaine (a local anesthetic used by both dentists and anesthesiologists), apparently resulting in fewer visits to the dentist due to fears about dental injections inadequately numbing teeth. (5) This perception is understandable, as several publications in the lay press support it and many physicians and anesthesiologists also believe it to be true. (6)

Historically, redheads have been associated with hot-tempers and perceived as more emotional, which might suggest they need more drugs and anesthetic gases to maintain sleep during surgery. In fact, a brief Internet search reveals hundreds of articles and blogs detailing the unique personality traits of redheads. According to these articles, redheads are more emotional; are more fiery and have volatile tempers; seem to have greater sexual attractiveness and sexual drive (“red on the head, fire in bed”); and, in Russian culture at least, redheads are crazy!

Much of the conjecture about redheads and anesthesia came from small studies in mice and humans, but the most highly-quoted study was from the Cleveland Clinic. Their researchers studied 20 women and found significantly greater requirements for anesthesia for redheads than for dark-haired women (all women had the MC1R gene mutation

associated with red hair). (1) However, a later study by the same researchers in 2013 found no difference in IV anesthetic requirements for red-haired females. The study concluded: “Anecdotal impressions among anesthesiologists that propofol [a common IV anesthetic] requirements are increased in redheads thus seem unsubstantiated.” (7)

Indeed, a larger study performed by Australian researchers in 2012 examined 468 adult patients undergoing surgery under general anesthesia and, contrary to prior findings, showed that patients with red hair had no higher anesthesia drug requirements than patients with black or brown hair. (8) The researchers concluded: “We found no evidence that redheads had increased anesthetic requirement or faster speed of recovery after surgery. Nor was there any evidence of a difference in pain response, pain intensity, or other adverse effects after anesthesia and surgery … We could find no evidence that a patient’s natural hair color meaningfully affects anesthetic requirements …" (8)

All patients undergoing surgery need different doses of anesthesia drugs and gases to achieve a satisfactory anesthetic state, and while certain patients might require more or less than the average patient, it is not always easy to predict what a given patient will require. The very elderly, for instance, typically require smaller doses of anesthetic drugs. But, while all people differ in their drug requirements for anesthesia, there is no current evidence to suggest that redheads need more. Further research may present new findings and change our opinion, but these recent studies demonstrate that redheads are no different from their dark-haired counterparts, at least when it comes to anesthesia … As for those other personality traits, well — that is an area for new (and perhaps more intriguing) research.

References

1. Liem EB, Lin CM, Suleman MI, et.al. Anesthetic requirement is increased in redheads. Anesthesiology 2004; 101:279-283.
2. Xing y, Sonner JM, Eger EI, Cascio M, Sessler DI. Mice with a melanocortin 1 receptor mutation have a slightly greater minimum alveolar concentration than control mice. Anesthesiology 2004; 101:544-546.
3. Liem EB, Joiner TV, Tsued AK, Sessler DI. Increased sensitivity to thermal pain and reduced subcutaneous lidocaine efficacy in redheads. Anesthesiology 2005; 102:509-514.
4. Delaney A, Keighren M, Fleetwood-Walker SM, et.al. Involvement of the melanocortin-1 receptor in acute pain and pain of inflammatory but not neuropathic origin. PLoS One 2010; 5:e12498.
5. Binkley CJ, Beacham A, Neace W, Gregg RG, Liem EB, Sessler DI. Genetic variations associated with red hair color and fear of dental pain, anxiety regarding dental care and avoidance of dental care. J Am Dent Assoc. 2009;140:896–905
6. Mogil JS, Ritchie J, Smith SB, et al. Melanocortin-1 receptor gene variants affect pain and mu-opioid analgesia in mice and humans. J Med Genet. 2005; 42:583-587.
7. Anthony G. Doufas, MD, PhD, Mukadder Orhan-Sungur, MD, Ryu Komatsu, MD. Bispectral Index Dynamics During Propofol Hypnosis Is Similar in Red-Haired and Dark-Haired Subjects. Anesth Analg 2013;116:319–26
8. PS Myles, FF Buchanan, et.al. The effect of hair colour on anaesthetic requirements and recovery time after surgery. Anaesth Intensive Care 2012; 40:683-689.

Dr. O'Connor is a professor of Anesthesiology at Rush University Medical Center in Chicago. This article was previously published on Ginger Parrot.