Understanding the Risks of Anesthesia

All Anesthesia Has Risks

Patient taking anesthetic
Paul Harizan/The Image Bank/Getty Images

In addition to the general risks of surgery, anesthesia given during surgery to help sedate you and control pain poses its own risks. While anesthesia is considered safe for both adults and children, no anesthesia is risk-free, just as no surgery is risk-free.

The level of risk varies with your procedure, the age and health and the type of anesthesia. Your surgeon or anesthesia provider should give you an accurate assessment of your personal risk.

Why Can't I Eat or Drink Before Surgery

Aspiration happens when vomit is produced during surgery and is then inhaled into the lungs. Normally, you cough when a foreign object enters your airway, but the medications given during anesthesia can prevent coughing. Aspiration can cause lung infections, a blockage in the airway or a severe cough.

Patients are asked to refrain from eating or drinking in the 12 hours prior to surgery to prevent aspiration.

Heart Problems and Anesthesia

Over 25% of the patients who undergo surgery each year have heart disease, including coronary artery disease, high blood pressure or congestive heart failure. Heart problems, commonly referred to as cardiac disease, does not prevent surgery in most cases, but can increase the risk of surgery.

The type and severity of your heart disease is the primary indicator of the likelihood that surgery will trigger heart problems in the days after surgery. For example, if you have been diagnosed with atrial fibrillation and take medication for it, you would be much more likely to have problems with atrial fibrillation after surgery than a patient who has no history of heart disease.

Problems that are the most likely to occur during and after surgery include high or low blood pressure, altered heart rhythms and in much rarer cases, heart attack.

Malignant Hyperthermia (MH)

Malignant hyperthermia is a rare inherited disorder in which a patient has a severe, life-threatening reaction when anesthesia gases are inhaled or a muscle relaxant called succinylcholine is given. When a patient who has the malignant hyperthermia gene has a reaction, his temperature rises rapidly, his muscles become rigid and the body begins to break down muscle fibers. The condition is serious and can result in the death of healthy patients if doctors cannot halt or control the symptoms with medication.

Testing is available for malignant hyperthermia and is recommended prior to surgery if close relatives have been diagnosed with the disorder. A muscle biopsy, a procedure where a small piece of muscle is removed by inserting a needle into a muscle, must be taken and analyzed to determine if a patient is a carrier.

Epidural Anesthesia and Headache

regional-epidural anesthesia
Epidural Anesthesia Image. Photo © A.D.A.M.

Approximately 1% to 2% of patients who have had a spinal epidural, a type of regional anesthesia, suffer a severe headache after the medication is given. An epidural is given by injecting a numbing medication into the cerebral spinal fluid that surrounds the spine. If the spinal fluid leaks from the injection site, the decrease in spinal fluid causes a severe headache.

The headache is treated with pain medication or a “blood patch.” For a blood patch, a small amount of the patient's own blood is injected a closely as possible to the original epidural site where it can clot and stop the loss of cerebral spinal fluid.

Nausea and Vomiting

Nausea and vomiting are the most common side effects of anesthesia, but both are far better controlled after surgery than they were in the past. IV medications can now be given at the first hint of nausea to control the symptoms and prevent vomiting, which can cause significant stress on surgical incisions.

Some anesthesia providers actually provide anti-nausea medications at the end of surgery to help prevent nausea during the early part of recovery from anesthesia.

Nerve Damage and Surgery

epidural anesthesia
Epidural Anesthesia Image. Photo © A.D.A.M.

Nerve damage can results from general anesthesia, local anesthesia and regional anesthesia. While the cause of damage varies, it can range in severity from mildly annoying to disabling. In most cases, the damage is temporary and the discomfort or numbness decreases in the weeks following surgery. But a small percentage of patient have lasting nerve problems.

During local or regional anesthesia, damage can occur when medications are injected into a nerve and either the syringe or the medication used for the injection injures the nerve tissue. Damage can also occur during a spinal epidural, one type of regional anesthesia, if the spinal cord is injured by the injection of anesthetics.

Nerve damage can also result during general anesthesia, if the patient is placed in a position that when medication if the patient is lying in a position for extended periods of time that block blood flow to the nerves. An example of this type of damage is the “pins and needles” sensation when a leg is “asleep.” A person that is awake can stand up or move to relieve the problem, but a patient who is under anesthesia does not know there is a problem and cannot move.

Sore Throat

endotracheal tube for intubation during general surgery
Endotracheal Tube. Photo © A.D.A.M.

Many patients complain of a sore throat for a few days after having surgery with general anesthesia. The soreness is caused by the insertion of the endotracheal tube through the mouth into the airway. The tube is necessary for the the patient to breathe during surgery. The pain is usually minor and is treated like a typical sore throat.

In rare cases, the vocal cords can be damaged when the breathing tube is inserted, or when the tube must remain in place for an extended period of time.

Anesthesia Awareness

Anesthesia awareness happens when the medications provided to render the patient unconscious during general anesthesia are not effective but the agents used to paralyze the patient are effective. This means that the patient is unable to move or speak, but is wide awake, hearing and feeling the entire procedure.

Awareness during a surgical procedure is a rare, but it remains a concern for many patients who are anticipating having surgery with general anesthesia.

If you are concerned about anesthesia awareness or have experienced it in the past, be sure to inform your anesthesia provider. Doctors can address your concerns and your specific situation to make sure your anesthesia is adequate for your surgery.

The Inability to Urinate After Surgery

urinary catheter in place for urinary retention after surgery
Male With Urinary Catheter. Photo © A.D.A.M.

The medications that are used to paralyze the muscles of the body during general anesthesia work on many areas of the body. In some patients, the muscles of the bladder become paralyzed, and the patient is unable to urinate. The ability to urinate typically returns within 24 hours, but during that time the bladder can become uncomfortably full, making a urinary catheter necessary.


Details on Malignant Hyperthermia, American Society of Anesthesiologists http://www.asahq.org/news/asanews032808.htm

Patient Education FAQ, American Society of Anesthesiologists http://www.asahq.org/patientEducation.htm

Surgery: Scientific Principals and Practice, Third Edition. 2001. Lazar J Greenfield, MD, et al.

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