Anesthesiologists and nurse anesthetists have the opportunity and challenge of caring for a wide array of patients ranging from the healthy ASA I patient to the moribund ASA 5 patient. Despite the complexity and uniqueness of each patient, there are many common problems that occur in the operating room of which you should be aware. It is important that you have a thorough understanding of both physiology and pharmacology in order to care for patients undergoing anesthesia, and in order to be able to recognize and confidently manage intraoperative events.

Additionally, it is imperative that members of the anesthesia care team act quickly to correct any problems that occur in order to prevent harm to the patient. As opposed to standard Advanced Cardiac Life Support (ACLS) that is primarily built for unwitnessed cardiopulmonary arrest, the problems that will be described in this chapter typically occur in a setting in which (a) the problem is witnessed from its onset, (b) the patient is extensively monitored (e.g. ECG, pulse oximeter, ETCO₂), and (c) the past medical and surgical history of the patient is known. As such, while many of the underlying principles and goals of ACLS for assessment of patients in unstable, near-arrest, and arrest situations apply, numerous management steps are different. Table 17.1 lists the most common intraoperative problems that may occur during anesthesia. Almost all perioperative urgencies and emergencies will map to one of five areas of concern: cardiac, pulmonary, neurologic, metabolic/endocrine, or toxins. This is certainly true for all common intraoperative patient problems. The only additional category is that of machine or system failure (e.g. oxygen supply failure), which is not discussed in this chapter.

The goals of this chapter include providing you with a framework by which to think about the approach to the unstable patient, how you might construct a differential diagnosis for that instability, and the proper steps for initial management of common intraoperative problems. When there is a concern for an acute change in patient condition under anesthesia, having a structured approach to the patient will be of benefit. First, you should start by assessing the general hemodynamic state of the patient and proceed through a series of decision nodes to define the initial course of action. This should start with the steps of defining whether the patient has a pulse. If not, proceed with advanced cardiac life support (ACLS) management while noting the differences in the operative setting [10, 13]. If the patient has a pulse, then one should define whether there is an acute hemodynamic instability to be addressed. If so, following the steps outlined in the cardiovascular section below is indicated. If the patient appears to have adequate cardiac output, then an assessment can proceed to the other four areas of concern noted above, with pulmonary being most important in order to ensure that adequate oxygenation and ventilation are present. A progression of thought through the other possible major categories should be undertaken in sequence. At each step, one should ask the questions outlined in Fig. 17.1, which will aid in constructing a differential diagnoses, picking a leading diagnosis, and then proceeding with initial management plan. Of note, the initial diagnosis may simply be a patient state (e.g. severe hypoxemia) rather than a particular known cause. Thus, in the acute care setting the first step is to ensure that cardiopulmonary function is at a level that meets basic metabolic requirements in order to avert patient harm and then proceed to defining an exact etiology.

The cardiovascular system is often the source of many intraoperative problems as there are numerous forces at play that can effect normal homeostasis in preload, afterload, chronotropy, and inotropy. Disturbances of the cardiovascular system can be thought of originating from the following etiologies: pipes (systemic vessels), pump (RV/LV inotropy), preload, valves, vessels (coronary arteries), and voltage (conduction system). Systematically reviewing these six categories provides structure within the cardiovascular system to critically evaluate the patients condition, formulate a differential diagnosis, and quickly identify and treat the problem. Below is a brief overview of the six key components of cardiovascular integrity. For a more in-depth discussion of cardiovascular physiology, please see Chap. 18.

Pipes are the peripheral vessels (aorta – >arteries – > arterioles) that carry oxygen and nutrients to the tissues for exchange at the capillary level. They then carry CO₂ and waste back to the liver, for detoxification, and heart by the venous system (venules – > veins – > IVC and SVC). This complex system of vessels in series and in parallel accounts for the majority of afterload as systemic vascular resistance. The heart is a pump that provides cardiac output to the body. The effectiveness of the heart as a pump is affected by heart rate, stroke volume, contractility, and afterload, which is the pressure the heart must contract against to generate forward flow. Preload can be thought of as the volume of blood in the right and left ventricles at the end of diastole. This volume is important for determining the strength of contraction, which is due to myocardial stretch at the beginning of systole, according to the Frank-Starling law. The extremes of preload (severe hypovolemia and hypervolemia) both result in reduced cardiac output, but by different mechanisms. The heart has four chambers, thus there are four valves, which are responsible for both allowing forward flow of blood and halting backward flow, depending on which part of the cardiac cycle is occurring. These include the tricuspid, pulmonic, mitral, and aortic valves. The coronary arteries are the vessels that supply blood and oxygen to the myocardium. They consist of the left and right coronary arteries, which become the left anterior descending, left circumflex, and posterior descending arteries, along with a number of smaller branched arteries. Voltage refers to electrical conduction through the heart during the cardiac cycle. Normal sinus rhythm is important because it produces maximal atrio-ventricular coupling for effective filling and ejection of blood to produce a stable cardiac output. The most common problems of the cardiovascular system will be discussed below. For an extensive list with many other problems, please refer back to Table 17.1.