Isoflurane and the Coronary Steal Controversy of the 1980s: Origin, Resolution, and Legacy

Isoflurane was introduced for general clinical use in North America in 1981. Shortly thereafter, in 1983, a study suggested that the anesthetic was a potent coronary vasodilator that could cause coronary steal and myocardial ischemia in patients with coronary artery disease. Myocardial ischemia results from small-vessel dilation which leads to increased blood flow to well-perfused myocardium and decreased blood flow to myocardium with borderline perfusion. This action of isoflurane raised concerns and threatened its use. By the early 1990s, these concerns were resolved by carefully performed clinical and experimental studies demonstrating no evidence of adverse cardiac changes during isoflurane administration as long as hemodynamic variables were tightly controlled. Indeed, the controversy sparked by the 1983 study led to a chain of experimental studies that ultimately demonstrated ironically that isoflurane has a preconditioning, cardioprotective effect. This chapter in anesthesia history underscores the importance of allowing the passage of time before assessing the clinical and scientific impact of a research finding.