In Response: We appreciate the opportunity to reply to the letter of Dr. Bernstein, which addresses several broader issues than we intended to discuss in our editorial. Acknowledging the complexity of these issues, we nonetheless wish to reiterate certain key concepts. First and most importantly, our editorial intention was to emphasize that the findings of the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatment (SUPPORT) project [1] have limited generalizablity, which the authors of the study have subsequently acknowledged [2]. In fact, these authors have now stated [2] that they do not recommend applying their results to surgical patients or to other types of patients underrepresented in the SUPPORT study. Based on vast clinical experience, it is predictable that pulmonary artery catheterization (PAC) would have negligible impact on the outcome of a population primarily composed of patients with respiratory failure and multisystem organ failure, such as those in the SUPPORT study [1]. Unfortunately, there are inadequate scientific data to define whether PAC improves outcome in particular subsets of patients with cardiovascular disease when it is used to guide therapy in a prespecified fashion. Without testing the hypothesis in a well controlled trial of limited focus to evaluate outcome benefit in discrete subpopulations of patients, the question of PAC usefulness will remain unanswered. Such an approach is neither simplistic nor naive. Indeed, after carefully deliberating the implications of their study, the SUPPORT authors have also reached the conclusion [2] that only prospective, randomized, controlled trials will provide unbiased estimates of the effect of PAC on outcomes. The propriety of our editorial comments are further validated by the recent acknowledgment [3] of Bone (author of the editorial originally accompanying the SUPPORT publication [4]) that had the ASA practice guidelines on PAC [5] been followed explicitly in the SUPPORT study, the treated subgroup would have likely had improved outcomes. Additionally, he agrees [3] with the ASA practice guidelines [5], which outline the necessary research agenda for proper evaluation of the effects of PAC on outcome. Furthermore, neither we nor the ASA practice guidelines promote routine use of the PAC, as is asserted by Dr. Bernstein. In fact, we stressed in our commentary that the rational use of any high-cost technology requires application of disciplined logic, and that routine PAC during all surgical cases of a certain type (e.g., abdominal aortic surgery) is not prudent application of an expensive resource. Finally, it was never our intention to suggest that future technologies would not supplant PAC. Our editorial does not imply this, and we, indeed, embrace advances and improvements in the ability to clinically evaluate the cardiovascular system. Our silence on this in our commentary simply reflected our desire to focus on the issue at hand-proper interpretation of the SUPPORT study and the need to evaluate our current use of PAC-rather than to dilute the discussion with the assessment of alternative technologies. Although current bioimpedance devices may more accurately measure cardiac output than earlier versions of this technology, we strongly disagree that this technique will "for certain" supplant PAC. Such certainty is not possible, primarily because of the very dilemma we currently face with PAC. Just as we previously concluded that debate over the value of PAC (especially in the perioperative setting) will not be fruitful without additional data from properly controlled trials, this equally applies to alternative technologies that are being developed to evaluate cardiovascular status. Regardless of which technologies eventually emerge as potential replacements for PAC, physicians will eventually face similar dilemmas about the impact of future technologies on outcome, and the debate of those issues will also not be resolved without appropriately designed, well conducted, randomized trials evaluating relevant outcomes in appropriate patient populations. Kenneth J. Tuman, MD Department of Anesthesiology; Rush Medical College; Chicago, IL 60612 Michael F. Roizen, MD Department of Anesthesia and Critical Care; University of Chicago; Chicago, IL 60612