Donʼt Abandon Test Doses

Abstract

In Response: We believe that Mulroy et al. have misinterpreted our editorial. The editorial and the article [1] that prompted it specifically apply to vascular patients. These patients are at risk for myocardial ischemia or dysfunction with a test dose of epinephrine. In fact, one of the coauthors of the letter (Batra) was an investigator in a study [2] in which electrocardiographic changes were induced with a test dose of 15 micro gram of epinephrine. Of 175 individuals tested with epinephrine, 7 had junctional rhythm; 3, premature ventricular contractions; 2, atrial tachycardia; and almost 50% (82 patients) had either T-wave flattening, T-wave inversion, or ST depression consistent with what we would today call myocardial ischemia. Careful readers of our editorial will find that our intention was not to advocate the abandonment of test doses but to suggest that determining the optimal test dose is inappropriate before a real benefit of a test dose has been shown. Many seemingly logical practices in medicine have proved useless when studied scientifically. For instance, we no longer require that 10 g of hemoglobin be given to "healthy" patients before surgical procedures when blood loss is not expected, or that potassium levels be normal before surgery in asymptomatic patients not receiving digoxin. In the past, these transfusions and potassium treatments may have resulted in more harm than help to patients. Our plea in the editorial was for rigor in using a test dose in patients at risk for complications. Although toxicity may occur from intravascular injection, there are no data to show that adding epinephrine to bupivacaine actually reduces risk or lessens complications. What we meant to communicate in the editorial was, before an optimal test dose of epinephrine is evaluated in vascular surgery patients, the real benefit versus harm of such a test dose must be determined. We should not seek the dose that is least likely to produce tachycardia, but rather a dose not associated with symptoms likely to involve greater risk than benefit. Our response to the letter of Mulroy et al. has given us the opportunity to express the ideas in our editorial more clearly. Alicia Toledano, SCD Joseph Foss, MD Michael F. Roizen, MD Department of Anesthesia and Critical Care University of Chicago Chicago, IL 60637