I've had it once and the story is similar to WorldRunner's although I don't remember getting high. What I do remember is waking up and having absolutely no clue how much time had passed -- felt like about 5 seconds but it was actually about 2-3 hours. Groggy feeling lasts about an hour but is no worse than an average hangover.
An excerpt from universityhealth.org...
Complications from general anesthesia
Serious side effects of general anesthesia are uncommon, especially in people who are otherwise healthy. However, because general anesthesia affects the whole body, it is more likely to cause side effects than local or regional anesthesia. Fortunately, most side effects of general anesthesia are minor and can be easily managed.
General anesthesia suppresses the normal throat reflexes such as swallowing, coughing, or gagging that prevent aspiration. Aspiration occurs when an object or liquid is inhaled into the respiratory tract (the windpipe or the lungs). To help prevent aspiration, an
endotracheal (ET) tube may be inserted during general anesthesia. When an ET tube is in place, the lungs are protected so stomach contents cannot enter the lungs. Aspiration during anesthesia and surgery is very uncommon. People are usually instructed not to eat or drink anything for a specific number of hours before anesthesia so that their stomach is empty to reduce this risk.
Insertion or removal of airways may cause respiratory problems such as coughing; gagging; muscle spasms in the voice box, or larynx (laryngospasm); or bronchial tubes in the lungs (bronchospasm). Insertion of airways also may cause an increase in blood pressure (hypertension) and heart rate (tachycardia). Other complications may include damage to teeth and lips, swelling in the larynx, sore throat, and hoarseness caused by injury or irritation of the larynx. Other serious risks of general anesthesia include changes in blood pressure or heart rate or rhythm, heart attack, or
stroke. Death or serious illness or injury due solely to anesthesia is rare and is usually also related to complications from the surgery. Death occurs in about 1 in 250,000 people receiving general anesthesia, although risks are greater for those people with serious medical conditions.<SUP>
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Many people who are going to have general anesthesia express concern that they will not be completely unconscious but will "wake up" and have some awareness during the surgical procedure. However,
awareness during general anesthesia is very rare.
source link:
http://www.universityhealth.org/115447.cfm