13.5: General Anesthesia: Overview

Anesthesia is a medical procedure that uses drugs for CNS suppression to enable painless surgeries and procedures. The selection of anesthetics is influenced by their pharmacokinetic properties, side effects, and patient characteristics. Various types of anesthesia include general, local, regional, spinal, and inhalational.

General anesthesia induces unconsciousness in the whole body, while the others target specific areas or sensations. It is administered to minimize adverse effects, maintain physiological homeostasis during surgery, and improve postoperative outcomes by blocking or treating components of the surgical stress response. General anesthesia involves multiple components like amnesia, analgesia, unconsciousness, immobility in response to noxious stimulation, and attenuation of autonomic responses to noxious stimulation. General anesthetics are classified based on their cellular mechanisms and the anatomic sites they impact. They can either inhibit excitatory systems or activate inhibitory ones. Hemodynamic effects of general anesthesia often involve a decrease in systemic arterial blood pressure due to direct vasodilation, myocardial depression, blunted baroreceptor control, and a generalized decrease in central sympathetic tone. Respiratory effects include reduced ventilatory drive and reflexes that maintain airway patency, necessitating assisted or controlled ventilation. Endotracheal intubation helps avoid aspiration deaths during general anesthesia. Hypothermia, a common occurrence during surgery, results from low ambient temperatures, exposed body cavities, cold intravenous fluids, altered thermoregulatory control, and reduced metabolic rate. Nausea and vomiting are common postoperative complications induced by anesthetics' action on the chemoreceptor trigger zone and the brainstem vomiting center. Adjunct agents such as benzodiazepines, analgesics, α₂-agonists, and neuromuscular blockers are often used alongside general anesthetics to enhance their effectiveness and manage side effects.

Anesthesia induces temporary loss of sensation and awareness through various agents.

There are different types of anesthesia, including general, local, and regional anesthesia. General anesthesia alters neuronal transmission in the CNS, resulting in a reversible state of unconsciousness.

General anesthesia is primarily used during surgeries to ensure optimal patient comfort and procedural effectiveness.

It necessitates monitoring for hemodynamic stability, adequate ventilation and oxygenation, preventing hypothermia, and mitigating potential adverse effects such as nausea and vomiting.

General anesthesia involves multiple components like amnesia, analgesia, unconsciousness, and immobility in response to noxious stimulation.

The choice of anesthetic depends on the patient's physical condition, anatomical site, and surgical procedure duration. Some examples include inhalational agents like volatile halogenated ethers and intravenous agents such as propofol and barbiturates.

Additionally, adjunct agents like benzodiazepines, α₂ agonists and neuromuscular blockers are often used to enhance the effects of general anesthetics.