Side Effects of Twilight Anesthesia

Twilight anesthesia, more commonly known as conscious sedation or sedation analgesia, according to the American Society of Anesthesiologists, consists of intravenous medications to decrease pain, reduce anxiety and facilitate relaxation during procedures such as minor surgery. Midazolam, sold commercially as Versed, and fentanyl are the two most commonly used medications in twilight sleep, notes the Encyclopedia of Surgery, although other medications such as Valium may also be used. Twilight sleep often causes fewer side effects than general anesthesia.


A brief period of amnesia normally occurs after conscious sedation using midazolam. Midazolam induces amnesia but does not decrease pain. Amensia due to midazolam normally lasts an hour after administration, but can last up to six hours, warns the Encyclopedia of Surgery. Patients should not drive home after receiving this medication for a procedure.

Cardiovascular Effects

Twilight anesthesia medications may cause bradycardia, or slow heart rate, and hypotension, or low blood pressure, according to the University of Virginia.

Central Nervous System Effects

Dizziness, agitation, blurred vision and ataxia, or lack of coordination, may occur after twilight sleep, states the University of Virginia.

Gastrointestinal Side Effects

Although less common than after general anesthesia, nausea and vomiting may occur in some people after twilight sleep, notes the American Association of Nurse Anesthetists. Fentanyl may also cause constipation.

Inadequate Anesthesia

Twilight sleep may not provide adequate anesthesia for some people. Muscular young men and anxious children may require more sedation, reports the University of Buffalo, while the elderly may require less. Not waiting an adequate amount of time for the medication to take effect may also result in pain during the procedure.

Prolonged Recovery

While most drugs used for twilight sleep clear the system within an hour or two, allowing the patient to go home but not to drive himself, some people may require prolonged recovery times.

Respiratory Depression

Fentanyl, a pain reliever often used for twilight sleep, is 50 to 100 times more potent than morphine, and may cause respiratory depression in some people. Oxygen saturation levels should be monitored with a pulse oximeter during twilight sleep to ensure adequate oxygenation. Oxygen administration or intubation, and mechanical ventilation may be required if deep respiratory depression occurs during twilight sleep. Nalaxone, a medication that reverses the narcotic effects of fentanyl, can reduce the depressive effects.

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