Surgery & Anesthesia · 1966
National Halothane Study
Halothane reached clinical practice in 1956 and was rapidly adopted because it was nonflammable, potent, and smoother to administer than the ether and cyclopropane it replaced. Within a few years, case reports began appearing of fatal hepatic necrosis in patients who had received it, some after a single exposure but more often after repeat anesthetics. The anesthesiology community was divided: some believed halothane was causally responsible, others attributed the deaths to hypotension, surgical trauma, or coincident disease. No single institution had enough cases to answer the question, and there was no infrastructure for pooling data across hospitals.
The National Halothane Study was organized to provide that infrastructure. Under the leadership of John Bunker and with analytic direction from Lincoln Moses, a biostatistician at Stanford, investigators assembled postoperative records from 34 hospitals covering approximately 850,000 anesthetic administrations between 1959 and 1962. It was among the largest retrospective outcome studies conducted in surgery or anesthesia to that point. Published in JAMA in 1966, the study found that massive hepatic necrosis after any anesthetic occurred at roughly 1 in 10,000 cases.
The critical finding for halothane specifically was that its rate of hepatic necrosis was not clearly elevated above that of other agents once the data were adjusted for patient characteristics, surgical procedure, and institutional factors. Halothane was used preferentially in healthier patients undergoing elective surgery, a selection bias that had made earlier comparisons misleading. After controlling for those variables, the excess attributed to halothane largely disappeared.
The result quieted the immediate alarm, but it did not close the case entirely. Subsequent smaller case series, particularly from the 1970s, documented an idiosyncratic hepatitis syndrome that appeared specifically after repeat halothane exposure, sometimes with fever and eosinophilia suggesting an immune mechanism. The syndrome was real but rare, with later analyses estimating the risk at roughly 1 in several tens of thousands of repeat exposures. Halothane continued in clinical use for decades, especially in pediatric anesthesia where its track record was long, but was eventually displaced by newer volatile agents with less hepatic metabolism.
The study's most durable contribution was organizational rather than pharmacological. Coordinating retrospective outcome data across dozens of hospitals, applying consistent case definitions, and controlling for institutional variation in patient mix established a model for anesthesia outcomes research. Later anesthesia quality collaboratives, including procedure-outcome registries that began forming in the 1980s and 1990s, drew on the multi-site data-sharing design that Bunker and Moses had developed.
Key People
- John Bunker — Anesthesiologist who chaired the National Halothane Study committee
- Lincoln Moses — Biostatistician who led the study's analytic design at Stanford
- Henry Beecher — Harvard anesthesiologist who helped establish the study's research framework
JAMA, 1966
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