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methohexital (meth-o-hex-i-tal)



Therapeutic: general anesthetics

Pharmacologic: barbiturates

Schedule IV


Induction of general anesthesia. Sole anesthesia in short (<15 min), minimally painful procedures. Supplement to other anesthetic agents. To produce unconsciousness during balanced anesthesia.


Produces anesthesia by depressing the CNS, probably by potentiating gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter. Therapeutic Effects: Unconsciousness and general anesthesia.

Adverse Reactions/Side Effects

CNS: SEIZURES, anxiety, emergence delirium, headache, restlessness. EENT: rhinitis. Resp: APNEA, LARYNGOSPASM, bronchospasm, coughing, dyspnea, respiratory depression. CV: CARDIORESPIRATORY ARREST, hypotension. GI: abdominal pain, hiccups, nausea, salivation, vomiting. Derm: erythema, pruritus, urticaria. Local: pain at IM site, phlebitis at IV site. MS: muscle twitching. Misc: shivering, allergic reactions.


*Implications refer primarily to any residual effects that occur typically within 24 hr after anesthesia.

Examination and Evaluation

  • Assess respiration and notify physician or nursing staff immediately if patient exhibits any interruption in respiratory rate (apnea) or signs of cardiorespiratory arrest. Signs include decreased or absent respiration, confusion, bluish color of the skin and mucous membranes (cyanosis), and difficult/labored breathing (dyspnea). Monitor pulse oximetry and perform pulmonary function tests (See Appendix I) to quantify suspected changes in ventilation and respiratory function. Apnea or cardiorespiratory arrest requires emergency care.

  • Be alert for seizures, and document the number, duration, and severity of seizures. Report these findings immediately to the physician or nursing staff.

  • Monitor signs of laryngeal spasm and bronchospasm, including tightness in the throat and chest, wheezing, cough, and severe shortness of breath. Notify physician or nursing staff immediately if these reactions occur.

  • Be alert for signs of emergence reactions, including delirium, nightmares, hallucinations, anxiety, and other changes in mood and behavior. Report these signs to the physician or nursing staff.

  • Assess blood pressure periodically and compare to normal values (See Appendix F). Report low blood pressure (hypotension), especially if patient experiences dizziness, fatigue, or other symptoms.

  • Be alert for residual muscle twitching and increased skeletal muscle tone. Report a sustained increase in muscle excitability.

  • Monitor injection site for pain, swelling, and inflammation consistent with phlebitis. Report prolonged or excessive injection site reactions to the physician.


  • Implement breathing activities and other therapeutic exercises to encourage ventilation and help overcome any residual effects of the anesthetic.

  • Because of the risk of cardiorespiratory arrest, use extreme caution during aerobic exercise and other forms of therapeutic exercise until the residual anesthetic effects have diminished. Assess exercise tolerance frequently (blood pressure, heart rate, respiratory rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

  • To minimize orthostatic hypotension, patient should move slowly when assuming a more upright position.


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