Low Flow Anaesthesia

Abstract

Department of Anesthesiology, Northside Hospital, Atlanta, Georgia 30358.James C. Eisenach, M.D., Editor.Low Flow Anaesthesia: The Theory and Practice of Low Flow, Minimal Flow and Closed System Anaesthesia. By Jan A. Baum, English text revised by Geoffrey Nunn. Oxford, Butterworth-Heinemann, 1996. Pages: 212. Price:$75.00.“The dominant question is no longer whether to use [low flow anesthesia] but how to use it safely.”(H. J. Lowe and E. A. Ernst, 1981)Despite the optimism of the above quote, low flow anesthesia has not been a popular feature in most U.S. anesthesia departments to date. And that is a shame, if for no other reason (and there are many other reasons) than the huge financial advantage of the technique. Consider that many anesthesia departments are limiting the selection of induction agents, opioids, and muscle relaxants as a means of cost containment. With low flow anesthesia, one achieves large cost savings, while still using the drug (sevoflurane somewhat excepted) one wants! If lack of understanding is to blame for the low percentage of practitioners using low flows, this book will help more people shed their old “gas guzzling” style.The book is an English text revised from the original German. The book has 11 chapters-the early chapters discuss technical concepts of anesthesia systems and move onto pharmacokinetics. Next comes anesthetic methods/technical requirements, and monitoring and patient safety aspects-including a section on arguments against low flow anesthesia. Once the technical “base” has been achieved, a nice chapter on clinical practice is provided, and the book concludes with a section on perspectives and future technical developments. Although earlier books on low flow techniques (such as Lowe and Ernst's The Quantitative Practice of Anesthesia) performed a wonderful job of explaining the pharmacokinetics of the inhalational anesthetics of the time, this new book discusses new inhalation agents, new anesthetic and monitoring equipment, and even reviews five computer programs for simulation of inhalational anesthesia (some programs are complete with operating room sounds!).The future perspectives section is perhaps the most intriguing. Considering the financial advantages of closed and low flow anesthesia, will we reach a point where anesthesia machines will be manufactured on the basis of their closed and low flow function? Which would one rather buy-a potentially wasteful standard anesthesia machine, or a quantitative anesthesia machine like the new PhysioFlex (see chapter 7)? Due to electronic feedback control, a quantitative anesthesia machine would not allow the routine waste of anesthetic agent. The desired oxygen and anesthetic concentration would be entered into the machine, and infrared measurements in a feedback control loop with liquid injection would maintain the desired concentrations with virtually no waste. Current vaporizers and flow meters would be outdated-the automobile equivalent of points, condensers, and carburetors. All this would allow one to deliver the maximum possible number of MAC hours per bottle of inhalational agent. Discussions such as this make this book valuable to all practitioners.Stephen C. Grice, M.D., Department of Anesthesiology, Northside Hospital, Atlanta, Georgia 30358.