General Anesthesia

This chapter discusses general anesthesia in domestic animals. Following an introduction highlighting the threats to the patient during surgical procedures, six sections address the following concepts:

Section 1 : This course offers a comprehensive overview of the three fundamental components of general anesthesia: narcosis, which reduces patient stress by inducing sleep; myorelaxation, which provides complete muscle relaxation required for precise surgical procedures; and analgesia, which blocks pain by rendering the animal insensitive to incisions. Collectively, these components create a safe and effective surgical environment. For each part were examinated the body's adverse reflexes in response to surgical manipulations, including their classification, prevention, and how the three effects of general anesthesia are applied."

Section2: This sub-chapter covers the phases and stages of general anesthesia (GA). GA proceeds through five main phases: pre-anesthetic patient assessment, pre-induction phase, induction of GA, maintenance phase, and finally the anesthetic wake-up phase, including emergence and recovery. As for the stages of GA, they reflect the levels of central nervous system (CNS) depression and are divided into four stages, starting just after induction: Stage I (voluntary excitement), Stage II (involuntary excitement), Stage III (surgical anesthesia), and Stage IV (overdose). The surgical stage is further subdivided into different planes according to the depth of neuromuscular reflex depression: Plane I, Plane II, and Plane III, each being suited to a type of intervention (non-invasive, semi-invasive, or invasive).

Section 3: This sub-chapter examines the material used in general anesthesia, focusing on preanesthetic medications, anesthetics, the materials for their administration, and monitoring devices. The section on preanesthetic medications covers the central sedatives and analgesics administered before anesthesia, including anticholinergics, phenothiazines, benzodiazepines (BZD), alpha-2 agonists, and opioids. The section on anesthetics distinguishes between injectable anesthetics (agents for rapid action anesthesia) and inhalational anesthetics (administered via the respiratory route). Injectable anesthetics include barbiturates, phenolics, and dissociatives, while inhalational anesthetics encompass nitrous oxide and ether derivatives. Finally, the sub-chapter also addresses the material needed for administering these anesthetics, whether injectable or gaseous, as well as the necessary monitoring material.

Section 4: This sub-chapter covers General Anesthesia Techniques, detailing the principles for developing an effective protocol, including patient pre-assessment, anesthesia planning, and informed consent management. It explains patient preparation techniques, such as fasting and proper positioning. Regarding the administration of anesthetics, it distinguishes between injectables and inhalants, outlining procedures for each type and the necessary equipment. The sub-chapter also includes crucial monitoring methods, such as monitoring vital signs, depth of anesthesia, body temperature, and neuromuscular function, to ensure safe and effective management of anesthesia throughout the procedure.

Section 6: This sub-chapter addresses the risk of mortality and when it might occur during general anesthesia (GA). It also covers complications by system and their management, focusing on respiratory, cardiovascular, and metabolic complications.

Section 7: This Sub-chapter examines the different general anesthesia protocols tailored to each species and the objective of the anesthesia, whether for sedation or narcosis. It details specific protocols for dogs and cats, horses, and ruminants, considering the physiological differences and specific needs of each animal group. The protocols include choices of medications, administration techniques, and special considerations to ensure safe and effective anesthesia based on the characteristics of each species and clinical goals.