The intent of this book is to provide a succinct resource for anesthesiologists to use when formulating an anesthetic regimen for both routine and complex cases based on expert opinion and referenced literature. The book leverages from recent advances in clinical pharmacology to describe how anesthetics behave and aims to present this information in such a way that practicing clinicians find it useful.
Clinical pharmacologists have devoted years of research to describing drug behavior. Some of their work is interesting, and certainly relevant to medical practice in general, but not to an anesthesiologist. For example, anesthesiologists rarely, if ever, consider the half-life of propofol when formulating an induction dose. Half-life offers no insight into the onset and duration of loss of consciousness. Much of their research, however, is relevant to anesthetic practice, but uses complex math models to predict drug concentrations and their associated effects. Unfortunately, these models are too complicated to use during patient care. Anesthesiologists, for example, never use tri-exponential equations to determine the optimal dose of fentanyl.
A significant advance in anesthetic drug pharmacology is the use of computers to simulate drug behavior. Where appropriate and supported by published models, simulations will be used throughout this book to illustrate drug concentrations that result from various dosing regimens, predictions of selected drug effects, and interactions between various classes of anesthetic drugs.
Although simulations offer a power tool to visualize drug behavior, readers should be aware of their limitations. The science behind modeling techniques is evolving. Creating a robust pharmacologic model is an expensive and tedious process. Because of these reasons, many anesthetic drugs remain poorly characterized while others have been characterized with relatively simple models. Selected newer anesthetic drugs, developed in an era of sophisticated modeling techniques, have been characterized with more complex models. They may account for patient age, body habitus, or other patient demographics. Simulations presented in the book utilize the best available models at the time of its writing, but newer models are certainly on the horizon. As newer models become available, regular updates to this book will be provided.
It is important to recognize that all simulations are inherently wrong. They use population models to predict how drugs will behave in an individual. Many models were developed from observations in healthy volunteers, not patients. Other models were developed from observations in patients with unique demographics. Given the extensive interindividual variability, it is nearly impossible for models to consistently make accurate predictions. Thus, as with any simulation, these limitations should be considered when interpreting the simulations presented in this book.
The book is divided into six sections. The first section provides an overview of basic principles of clinical pharmacology and how they can be adapted to patient care. The second and third sections address anesthetic and other types of drugs (ie, antiemetics, antiseizure medications, etc) anesthesiologists routinely use. The fourth section will explore how patient demographics, described as covariates such as age and weight, influence anesthetic drug behavior. The fifth section will rely on simulation to illustrate various anesthetic techniques for premedication, induction and maintenance of anesthesia, moderate sedation, and postoperative pain control. This section will briefly explore how various anesthetic techniques compare with one another. The sixth section will provide a selection of sample cases associated with challenging considerations when dosing an anesthetic.
I wish to thank the many contributors to this book, whose expertise in clinical pharmacology have made Clinical Pharmacology for Anesthesiology, a distinctive addition to the anesthesia literature. Many of the contributing authors are thought leaders on topics covered in this text and have published numerous manuscripts on topics related to anesthetic drug behavior. Specifically, I wish to thank Noah Syroid, whose programming expertise and creative rendering of anesthetic drug pharmacology was instrumental in developing many of the figures used in this book. I also wish to thank the editors at McGraw Hill for their commitment and consistent support in preparing and editing this text. Finally I am grateful to my wife and family for their enduring support and encouragement, without which this book would not have come to fruition.