General anesthesia is used for most major surgeries and has a very low rate of serious side effects. It does carry more risks than local or regional anesthesia, but the side effects are generally minor and pass quickly. A person who has been given general anesthesia may experience headache, nausea and tiredness, but these issues are generally temporary. Only rarely do serious issues like allergic reactions, breathing problems or strokes occur.
Temporary Side Effects
Some of the potential general anesthesia side effects are due to mechanical damage to the body from the breathing tube that the anesthetist may place down the throat and into the airway to help the patient breathe while unconscious. The insertion and removal of the tube can cause injury or irritation to the throat and larynx, and often leaves the throat feeling very sore and dry. Hoarseness, coughing, and muscle spasms in the voice box or bronchial tubes in the lungs can all occur, but are uncommon. In rare cases, the teeth or other parts of the mouth and throat may be damaged when the equipment is inserted; a loose tooth could be knocked out, for example.
An increase in blood pressure and heart rate also are common general anesthesia side effects, but don't normally cause lasting complications. There may be bruising where an intravenous (IV) line was inserted along with muscle pain. Many people are tired and confused when they wake up, which may lead to coordination problems or even aggression if the person doesn't know where he or she is; these usually pass within 10 or 15 minutes, although a general feeling of tiredness can last longer.
Among the most common issues after a patient wakes up from a general anesthetic are headaches, feeling nauseous and vomiting. Patients are usually asked to fast before surgery, which leaves the stomach empty and makes vomiting less likely. A medical professional can also provide anti-nausea medication.
Shivering or trembling also is a very common side effect that occurs in about 40% of patients. This is partly due to the heat loss that usually occurs in cold operating rooms, but also can be a direct result of the anesthesia — the body's temperature thermostat resets while under general anesthesia, allowing it to tolerate the colder temperatures. When a patient wakes up, the body's thermostat returns to normal and may react to a lingering low body temperature by shivering.
Serious Side Effects
Serious general anesthesia side effects and complications during surgery are rare, but possible. Allergic reactions, infections, and lung problems can potentially occur. Heart problems and stroke are unlikely, but are also potential risks, and a condition called malignant hyperthermia, where a patient develops a dangerously high fever, is also a possibility. Waking up during surgery, called anesthesia awareness, is also known to happen, but only occurs in about 1 in 14,000 cases. The chance of dying after receiving general anesthesia is about 1 in 250,000, though this is rarely due to the anesthesia alone.
During the surgery, the anesthesiologist will pay careful attention to the patient's breathing, heart rate, and other vital signs. Anesthesiologists are trained to look for allergic reactions and other serious general anesthesia side effects, and they can react quickly to treat any that develop.
Though very rare, some serious side effects of general anesthesia can occur within a time span of two weeks after surgery. Some patients may experience pale or yellow skin or eyes, or unexplained body pain. Severe headache, nausea, or weakness may also occur. Black or bloody vomit or stool or unexplained weight loss are also indicators of a serious reaction. Anyone who experiences one or more of these side effects after undergoing general anesthesia should a visit a medical professional or the emergency room.
Many factors, including a patient’s age and current health, play a part in how he or she will respond to general anesthesia. Heart, lung, circulatory, and nervous disorders may increase the risk of problems. Medical history, drug or food allergies, and previous reactions to anesthesia are important risk factors that the patient should talk about with the surgeon or anesthesiologist. In some cases, there may be less dangerous forms of anesthesia that can be used on people who are at a high risk.
Patients should also tell the surgeon and anesthesiologist which prescription medications, herbal supplements, or over-the-counter drugs they are taking. The use of alcohol, tobacco, or illegal substances can also affect the risks of anesthesia, so these should also be discussed prior to the operation taking place. People who use opiates or cocaine may be more likely to experience anesthesia awareness, for example.