Anaesthesia for the High Risk Patient

Abstract

This 265-page softcover book has been complied from the effort of some 22 contributors. It aims to provide practical information on the management of high-risk patients by quoting numerous studies and providing sufficient background information to enable an understanding of the principles and rationale behind anesthetic and perioperative management. When I first picked this book up, I expected it to be a “cookbook” of techniques. It is not. This excellent text relies heavily on clinical and scientific studies, and where these studies have weakness the authors readily point them out. This text is not a substitute for major anesthetic texts but concentrates on principles of management of challenging situations. A great deal of emphasis is placed on cardiovascular risk and cardiac disease in general. Many studies are referenced, and one can see how the principles of patient management have actually evolved as the designs of these studies have improved. This book is divided into 17 chapters. These are referenced in the body of the text, and each one concludes with an impressive section entitled “Further Reading” and then “References.” The book relies heavily on the terms reserve, functional capacity, exercise tolerance, and optimization, as well as on implications for the type and site of surgery and its duration. The format is clearly designed to provide easy access to information presented in a concise manner. The actual styles of the chapters vary. Some relate more to basic physiology, medical principles, and pharmacology, whereas others are more practical, discussing the principles of anesthetic techniques for high-risk patients. However, all styles have a firm scientific basis. Almost every body system is considered in this text. The chapters devoted primarily to cardiac risk are especially impressive. Solidly based on scientific and clinical trials, they cover topics such as epidemiology, risk stratification, invasive and noninvasive preoperative testing (especially as these affect outcome), the importance of functional capacity (expressed in terms of metabolic equivalents), concurrent diabetes, and specific cardiovascular lesions, to name only a few. For example, in both animal and human models a coronary stenosis will start to produce flow limitations at rest only when the sectional diameter is reduced by 85–90%. However, under conditions of maximal flow (exercise or pharmacologically induced vasodilatation), stenosis with as little as 45% reduction in cross-sectional diameter will cause flow limitation manifesting as effort induced angina. Thus, the sensitivity of diagnostic physiological tests is markedly improved with increased flow enabling the detection of lesser stenosis. Other chapters cover topics such as respiratory risk, analgesia for the high-risk patient, local anesthetic techniques, the elderly patient, optimization, gastrointestinal considerations, renal considerations, anemia, the role of the cardiology consult, and the actual meaning of risk, again to name only a few. Similarly, considerations with respect to a couple of commonly used outpatient drugs—ketamine and nitrous oxide—are emphasized. For example, ketamine may increase oxygen extraction by tissues, thus helping prevent lactic acidosis, especially in the septic model. In addition, the traditional division of α, β, and dopamine receptor agonist properties on the basis of micrograms per kilogram per minute has now shown that the vasoconstrictor action occurs at much lower doses than what were originally thought. The excellent chapter on the elderly patient goes system-by-system into the changes induced by the aging process. It further emphasizes those factors of importance in preoperative assessment; preparation; anesthetic techniques; and, of course, the principles of optimization. The only so-called flaw I found in this text is the occasional misspelling of arrhythmia. Despite these minor nuances, this book could easily be classified as a must-have text in the reference library of any healthcare professional, especially those providing anesthesia and sedation services.