Halothane: The End of an Era?

Pediatric anesthesia is constantly undergoing improvements. Many factors contribute to these improvements, with research being a primary contributor to better clinical care. In this month’s issue of Anesthesia & Analgesia, Friesen et al. (1) present the clinically useful results of their research of the effect of halothane on hemodynamic variables during induction of anesthesia in infants after a variable preoperative fast. Potentially adverse decreases in hemodynamic variables were the most intense in infants after a prolonged fast. The study confirmed two truisms that our mentors have taught us and we, as well as our mentors, have on occasion experienced: halothane is not always well tolerated in infants, and halothane is often poorly tolerated in dehydrated infants. Friesen et al.’s study also is one of the final pages of a great book. During the past 40 to 50 years, a great deal has been written about halothane’s use in anesthesia. Halothane, our “gold standard” inhaled anesthetic, has been a vital component in pediatric anesthesia. This keystone to our practice is now about to be replaced by a better anesthetic for the induction of anesthesia in children. The replacement of halothane by sevoflurane has been a gradual, evidence-based swing in practice patterns. Sevoflurane entered our clinical practice after initial research meticulously established efficacy, safety, and ease of administration. Some clinicians rapidly adopted this new inhaled anesthetic, while others were skeptical. Many pediatric anesthesiologists were reluctant to switch away from halothane. We had learned the art of working with it. We respected its side effects and were able to manipulate its strengths to our patient’s advantage. Recently-trained anesthesiologists rapidly accepted sevoflurane and wisely avoided the experience of the more challenging learning curve associated with halothane. Senior staff were more reluctant to use sevoflurane, possibly because they were aware that all previous attempts to replace halothane had been unsuccessful, in spite of major marketing ploys. But now the pendulum has swung and sevoflurane is increasingly becoming the key anesthetic for an inhaled anesthetic in children. While clinicians have gradually switched to sevoflurane for mask-inhaled induction of anesthesia, so has science. Only 2 to 3 years ago, there were typically two types of studies involving sevoflurane. First, there were studies on the efficacy and safety of sevoflurane. Second, there were studies comparing outcomes after sevoflurane to a gold standard, usually halothane. Most children in studies involving assessment of drugs incorporated in anesthetic practice, such as antiemetics, received halothane. But in the past 24 months, results of a literature search show dramatic changes. Multidrug comparisons now show that sevoflurane is the gold standard. Even more striking is the switch to sevoflurane from halothane as the maintenance anesthetic, while other pediatric anesthesia-related drugs were being studied. Is halothane of historical interest? No! For most of us, it is still easily exchanged for sevoflurane. But for new trainees, that will not be the case, and they will be expected to use sevoflurane rather exclusively. Currently, the cost of sevoflurane is much more than halothane, but this cost difference should decrease with time, which will further reduce halothane usage. However, there will also be areas in our practice where sevoflurane is not available for a variety of legitimate reasons. For example, anesthesia in the third world will likely remain within the realm of halothane. Also, isolated areas in our practice may be equipped appropriately, but still lack a sevoflurane vaporizer. Finally, there will be areas in our practice where some of halothane’s “adverse effects,” such as myocardial depression, may be of clinical advantage. So, welcome to the new leader, but do not forget a cherished friend. Halothane can still have a place in our practice, although dramatically different.

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