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Potential Risks of General Anesthesia

General anesthesia puts patients to sleep so they are unconscious during the surgical procedure and do not feel any pain. Anesthetics are usually delivered by a combination of injection and inhalation with injectable anaesthetics inducing unconsciousness and inhalational anaesthetics maintaining it. General anesthesia can also be given solely by any of the two forms (injection or inhalation). During the procedure, the patient’s blood oxygen level, blood pressure, heart rate, temperature and breathing are closely monitored. Other types of anesthesia, such as local and regional anesthesia, including spinal anesthesia, do not induce sleep.

Drugs used as part of general anesthesia given by injection include benzodiazepines, propofol, etomidate, ketamine, opioid analgesics, neuromuscular blocking agents and barbiturates. The most common anesthetics delivered by inhalation include halogenated ethers such as desflurane, enflurane, isoflurane, halothane and sevoflurane. They are often combined with nitrous oxide.

For healthy people, general anesthesia does not carry any major risks. However, patients over 75 years of age, those who have obstructive sleep apnea, heart and blood pressure problems, thrombosis, diabetes, conditions involving lungs (e.g. asthma, bronchitis) and kidneys, serious neurological and neurodegenerative conditions, mental disorders, drug allergies including adverse reactions to anesthetics, patients who are obese, take certain medications (e.g. blood pressure lowering agents or blood thinning drugs), smoke, regularly drink alcohol or use recreational drugs are at an increased risk of complications from general anesthesia.

The most common minor problems associated with general anesthesia include:

  • Drowsiness
  • Dizziness
  • Nausea and vomiting
  • General weakness
  • Headache
  • Muscle aches
  • Shivering
  • Sore throat
  • Vision problems

Most of these side effects disappear within 24 hours after surgery, although they can last for a few days.

Though very low, there is still risk of more serious complications associated with general anesthesia. Rare, but more serious complications, may include:

  • Drug interactions
  • Waking up briefly during anesthesia and, very rarely, feeling pain during anesthesia
  • Temporary mental confusion
  • Feeling depressed
  • Increasing the risk of dementia and developing neurodegenerative disorders such as Alzheimer’s or Parkinson’s disease in the elderly
  • Lung infections
  • Sudden blood pressure drop and direct vasodilation
  • Stroke
  • Heart attack
  • Brain damage
  • Malignant hyperthermia
  • Death

General Anesthesia and the Elderly

The elderly are more likely to experience adverse drug interactions from general anesthesia than younger patients because they typically take more medications. In addition, research shows that older people react poorly to certain anesthetics, especially barbiturates, propofol, etomidate and inhalational anesthetics, which may increase their risk of side effects, such as cognitive disturbance.

Studies also show that in people over 75 years of age general anesthesia may increase the chance of developing or speeding up the development of dementia, Parkinson’s or Alzheimer’s disease by 25%. Marked decline in cognitive function which occurs right after surgery is called postoperative cognitive dysfunction (POCD). POCD promotes neuroinflammatory reactions in the brain that cause degeneration of its cells and eventually lead to dementia. Dementia may then develop into neurodegenerative disorders, such as Alzheimer’s disease. Therefore, many doctors discourage older patients from undergoing general anesthesia.

Where to Get More Information: American Society of Anesthesiologists