Side effects, best thought of as undesired effects of a medical therapy occurring along with the desired treatment, often occur following an anesthetic. Distinct from a complication, which implies harm or risk to the patient, side effects after anesthesia produce inconvenience and discomfort but usually not harm.
Nausea and Vomiting
Nausea and vomiting comprise the most well known of the anesthetic side effects. Up to 30 percent of patients experience at least nausea. This number jumps to 70 percent in patients known to be at high risk, according to the article "Consensus Guidelines for Managing Postoperative Nausea and Vomiting," published in the journal Anesthesia and Analgesia in 2003. Patient risk factors include female gender, non-smoking status, a history of motion sickness, and prior nausea or vomiting with anesthesia. Certain types of surgery also carry different risks for nausea. For example, the risk goes up with intra-abdominal surgery as compared to surgery on the limbs. Breast, brain, eye and ear surgery also increase this side effect. Longer surgeries also involve more risk of nausea and vomiting in the postoperative period. Not surprisingly, some types of anesthesia cause more nausea than others. General anesthesia using opioid medications and gas lead to more problems than local anesthesia or nerve blocks.
Most cases of a postoperative sore throat result from the breathing tube placed in the windpipe, between the vocal cords, during a general anesthetic. Although carefully positioned, sore throat may still result due to the sensitive nature of the windpipe. Even without a breathing tube, the oxygen and anesthesia gases produce a drying effect that irritates the mucous membranes of the throat. Lozenges and ice relieve the symptoms of the sore throat which resolves on its own in a few days.
Shivering and shaking bother about 40 percent of patients after an anesthetic, according to "Miller's Anesthesia, 7th edition." Intuitively, loss of heat during the surgery accounts for a great number of these cases. But because patients with normal body temperature also sometimes shiver, other properties of the anesthetic seem to be at play as well. Warming with forced air blankets and warm IV fluids treat those with lowered body temperature. Drugs such as the narcotic meperidine, through a poorly understood mechanism, effectively resolve shivering in non-thermogenic shivering, which is the type not due to low temperature.
Soreness and muscle aches account for another group of side effects after anesthesia. One of the medications used during anesthesia, succinylcholine, causes muscles to contract and then relax, which can result in residual muscle aches. General soreness also results from lying still on the operating table. Unlike natural sleep, the body can't make adjustments in position during anesthetic unconsciousness. Being in the same position for long periods of time causes muscles and joints to become stiff and sore. In addition, the flat and stiff design of the operating tables caters to surgical access and not comfort, further contributing to general body aching after surgery.