The American Society of Anesthesiology agrees with the conventional definition of general anesthesia as a loss of consciousness induced by drugs, from which a patient cannot be aroused even with painful stimulation. Manipulating human physiology and alertness with medications carries inherent risks. Serious problems remain rare, however, despite thousands of general anesthetic administrations every day.
General Anesthesia: With Breathing Tube
This endotracheal tube, although not required in every anesthetic, is sometimes used to facilitate delivery of oxygen and gas during surgery. The time between loss of consciousness and insertion of the tube, although brief, presents potential danger. Unexpected difficulty with placement can lower oxygen levels. Anesthesia providers, trained in emergency airway interventions, respond quickly to correct these problems. Increased risks also occur in asthmatics or other patients with lung disease as the breathing tube can irritate the airway and precipitate an asthma attack.
A more common danger results from the metal, flashlight-like device used in the mouth to position the tube between the vocal cords as damage to teeth can occur in anywhere from less than 1 percent to 12 percent of patients, according to an analysis published in the journal "Anesthesiology."
General Anesthesia: No Breathing Tube
Although not always appropriate, certain types of masks, either on the mouth or over the nose and mouth, can also deliver oxygen and gas anesthesia. With no barrier or tube blocking the windpipe, saliva, acid from the stomach, or other secretions can enter the airway. This occasionally results in laryngospasm, a sudden spasm of the laryngeal cords that can cause dangerous closure of the vocal cords as well as a diminished oxygen supply to the lungs. Rarely, pneumonia results.
Life-threatening Reactions
Although very rare, with an incidence of one in 12,000 pediatric and one in 40,000 adult anesthetics, malignant hyperthermia causes life-threatening complications, according to the text, "Stoelting's Anesthesia and Co-Existing Disease." This genetic condition results in a hypermetabolic state, meaning that heart rate, breathing, temperature and muscle contraction increase significantly. If not promptly and aggressively treated, organ failure and death may result. Allergic reactions also occur with a very small percentage of patients, resulting in shock. Heart or lung problems resulting in serious danger occur predominantly in patients with pre-existing risk factors.
Special Considerations
Some factors predispose patients to more risk. The very young and very old often fare worse with physiologic challenges such as general anesthesia. Deterioration of function endangers patients who already have significant lung, heart, brain, liver or kidney problems. Studies continue to investigate the dangers of anesthetics on specific populations such as children and Alzheimer's patients. True awareness under anesthesia is rare, about one in 1,000, according to the American Society of Anesthesiology, with many of those cases having known risks such as trauma surgery.
References
- "Stoelting's Anesthesia and Co-Existing Disease"; Roberta Hines and Katherine Marschall, editors; 2008
- "Anesthesiology"; Practice Advisory for Intraoperative Awareness and Brain Function Monitoring"; American Society of Anesthesiologists Task Force on Intraoperative Awareness; 2006
- "Anesthesiology"; Perianesthetic Dental Injuries: Frequency, Outcomes, and Risk Factors"; ME Warner; May 1999
