Updated: Jun 18, 2021
Author: Branden Chen
Editors: Shamsia Ahmed and Liane Xu
Artists: Tiffany Chen
General anesthesia needs to accomplish two things: block pain and induce unconsciousness. The former is done through chemical interactions that begin once the anesthetic has entered the bloodstream, either by inhalation or intravenously. When tissue damage sensing nerve cells called nociceptors identify signs of tissue damage, a signal is sent to the brain via a series of electrical impulses. General anesthesia works by creating a blockage of charge in the nerve cells that interpret what to do with the pain signals they receive. This is achieved by binding to receptors on the nerve cells, leaving negatively charged particles open to entering the cell, while preventing positively charged particles from doing the same. This blockage prevents pain signals from being sent to those nerve cells. Unconsciousness is induced by reducing the number of connections in the brain that would usually govern awareness, decision making, and critical thinking.
Typically, general anesthesia has great effects on hemodynamics (the flow of blood throughout the body), as well as affecting a wide range of cardiac functions, such as a patient’s heart rate, blood pressure, and cardiac output. These effects typically start during the first of general anesthesia. Anesthesia causes peripheral vasodilation, increasing blood flow to skeletal muscle tissue and resulting in a decrease in systemic vascular resistance, increasing blood pressure. This change in blood pressure is detected by baroreceptors around the heart, influencing cardiovascular function. However, anesthetics administered via inhalation causes dose-dependent decreases in the activity of these baroreceptors, thus reducing the body’s natural compensatory responses to change in blood pressure. They may also cause cardiac dysrhythmias or irregular rhythm for the heart’s beating.
Due to all the danger that anesthesia poses for patients both with and without preexisting cardiovascular conditions, anesthesiologists have a particularly tough job making sure that the patient is fit to go under general anesthesia. Anesthesiologists must evaluate the risks in a patient’s medical condition and history that could lead to increased perioperative cardiac risk. For example, patients with ischemic heart disease, congestive cardiac failures, and other cardiovascular problems are more prone to developing these surgical cardiac complications. Therefore, the anesthesiologist must keep in mind these preexisting conditions, making the anesthetic development individualized depending on the needs and medical state of the patient. Typically, the anesthetic process requires gentle and cautionary measures from the anesthesiologist to avoid tachycardia and hypotension.
Currently, the use of epidural anesthesia is a decent choice as a method of dealing with the drawbacks of general anesthesia and the overall postoperative treatment. Epidural anesthesia has shown evidence of reducing cardiac and pulmonary complications in surgical patients. The epidural allows for the inhibition of the sympathetic nervous system, which prevents fatal heart attacks and severe chest pain. Thoracic Epidural Anesthesia may prevent these incidences of heart arrhythmias and myocardial infarctions. However, epidural anesthesia, just like general anesthesia, poses risks. For example, epidural anesthesia has been linked to neurologic deficits, not from hemorrhage or infection. The body’s absorption of these local anesthetics can induce seizures, loss of airway reflexes, respiratory depression, coma, and cardiac malfunctions. Important cardiovascular risks include bradycardia and hypotension. Although these issues are uncommon, they still pose a threat to the health of those undergoing major surgery without preexisting health conditions, resulting in more damage than repair.
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