Correspondence

Openand Closed Peritoneal Lavage KenZafren, MD TomPurcell, MD/ BryanR Troop, MD, FACS

Useof Methohexital in the ED Kenneth J Abrams, MD Clifford M Gevirtz, MD, MPH Paul L Goldiner, DDS, MD/ Brian J Zink, MD Richard Salluzzo, MD

TympanicThermometerAccuracy David M Nierman, MD, FCCP/ Joseph V Stewart, MD, FACEP Douglas Webster, DO

OCTOBER|992

Open and Closed Peritoneal Lavage To the Editor." We read with interest the article "Randomized, Prospective Comparison of Open and Closed Peritoneal Lavagefor Abdominal Trauma" [December 1991;20:12901292] by Troop et al. We acknowledge the advantages of the closed technique, but the conclusion that there "were no differences in complication rates" requires clarification. Using a level of statistical significance of .05 and a power of .80, we calculated the effect of size using the approximation method of Hulley and Cummings.1 For a one-tailed study (the closed technique is no less safe than the open) with 220 subjects and a complication rate in the control group of .01, the effect size is 780%. Therefore, the study would be unable to distinguish an almost eightfold higher complication rate of the closed technique from that of the open technique. Generally, a "large" effect size refers to a difference of 80% between the group proportions.2 To detect this effect size (80% more complications in the closed-technique group, or a rate of 0.018%) would require a study sample of more than 4,000 patients. These calculations emphasize the difficulties involved in drawing conclusions from negative studies and the importance of defining clearly all • relevant parameters in such studies. Only with this information can read-

21:10 ANNALS OF EMERGENCY MEDICINE

ers judge the usefulness of the data to their clinical practices.

KenZafren, MD TomPurcell, MD Departmentof EmergencyMedicine Kern Medical Center/UCLA Bakersfield, California 1. Hulley SB, Cummings SR: Designing Clinical Research. Baltimore, Williams & Wilkins, 1988, p 215-217. 2. Cohen J: Approximate power and sample size determination for onesample and two-sample hypothesis tests. Educ Psychol Measurement 1970;30:811-831.

In Reply." We appreciate the interest of Drs Zafren and Purcell in our study and thank them for clarifying the differences in complication rates. It is quite difficult to attain a statistically significant sample size Of the magnitude needed to compare two procedures that have such low complication rates. For this reason, our study concentrated on aspects of peritoneal lavage that had not been compared, such as cost, length of time to complete the lavage, and ease of use. Bryan R Troop,MD, FACS Departmentof Surgery St John's MercyMedical Center St Louis, Missouri

Use

of

Methohexital in the ED To the Editor." We read with great interest and some trepidation the report by Zink et al, "The Efficacy and Safety of Methohexital in the Emergency Department [December 1991;20:12931298]. Use of anesthetic medications by nonanesthesio]~i~, ~ recently . . .~i~ i~ been reviewed ~nIlhnSts'~d:, Wisconsin? The appropii~}eness of these practices is questionable. As practicing anesthesiologists in a major metropolitan medical center and a Level I trauma center, we feel compelled to comment on several of the issues raised by the authors. First, the authors make reference to an educational program designed to foster familiarity wit h various neuromuscular blocking agents and potent sedative/hypnotic agents. Clearly, having a didactic level of knowledge is important to the safe administration of these agents. However, many of the patients enrolled in this study were trauma patients, who have altered pharmacodynamic responses; thus, complex anesthetic management issues are raised. These patients frequently are volume depleted and have undergone fluid resuscitation, often with crystalloid therapy, producing a dilutional hypoproteinemia. Thus, the free fraction of drug available to the central nervous system is increased, leading to markedly exaggerated effects. Fu!l understanding of these pharmacologic alterations

1298/173

Open and closed peritoneal lavage.

Correspondence Openand Closed Peritoneal Lavage KenZafren, MD TomPurcell, MD/ BryanR Troop, MD, FACS Useof Methohexital in the ED Kenneth J Abrams,...
80KB Sizes 0 Downloads 0 Views