THIOPENTAL SODIUM

THIOPENTAL SODIUM (thye-oh-pen'tal) Pentothal Classifications: general anesthetic; sedative-hypnotic; barbiturate; Therapeutic: general anesthetic; sedative-hypnotic Pregnancy Category: C Controlled Substance: Schedule III

Availability

20 mg/mL, 25 mg/mL injection

Action

Ultrashort-acting barbiturate; induces brief general anesthesia without analgesia by depression of CNS. Loss of consciousness is rapid. Reduction in cardiac output and peripheral vasodilation frequently accompany anesthesia. Rapid redistribution of agent out of brain reduces anesthesia level and increases reflex airway hyperactivity to mechanical stimulation.

Therapeutic Effect

Muscle relaxation is slight, and reflexes are poorly controlled. Since analgesia is slight, thiopental is seldom used alone except for brief minor procedures.

Uses

To induce hypnosis and anesthesia prior to or as supplement to other anesthetic agents or as sole agent for brief (15-min) operative procedures. Also used as an anticonvulsant and sedative-hypnotic and for narcoanalysis and narcosynthesis in psychiatric disorders.

Contraindications

Hypersensitivity to barbiturates; history of paradoxic excitation; absence of suitable veins for IV administration; status asthmaticus; acute intermittent or other hepatic porphyrias; pregnancy (category C).

Cautious Use

Coronary artery disease, hypotension, shock; conditions that may potentiate or prolong hypnotic effect including excessive premedication, liver or kidney dysfunction, myxedema, Addison's disease, severe anemia, increased BUN; increased intracranial pressure; myasthenia gravis; asthma and other respiratory diseases.

Route & Dosage

Induction Adult: IV Test Dose 25–75 mg, then 50–75 mg at 20–40 sec intervals, an additional 50 mg may be given if needed Child: IV 5–6 mg/kg initially, followed by 1 mg/kg if needed Infant: IV 5–8 mg/kg Convulsions Adult: IV 75–250 mg, repeat as needed Child: IV 2–3 mg/kg/dose, repeat as needed Narcoanalysis Adult: IV 100 mg/min until confusion occurs Renal Impairment If Clcr <10 mL/min, give 75% of dose.

Administration

Intravenous Note: Verify correct IV concentration and rate of infusion to neonates, infants, children with physician. Test dose: May be given to assess unusual sensitivity to drug. Following administration, observe patient for at least 1 min for unexpected deep anesthesia or respiratory depression. PREPARE: Direct: Reconstitute each 500 mg of powder by adding at least 20 mL of sterile water for injection to yield a 2.5% solution (25 mg/1 mL).  Continuous: May be further diluted for infusion by adding 20 mL of reconstituted solution to at least 100 mL of NS or D5W. Prepare solution freshly and use promptly. If a precipitate is present, discard solution. • Unused portions should be discarded within 24 h.  ADMINISTER: Direct: Infuse each 25 mg over 1 min or more.  Continuous: Titrate to achieve desired result.   INCOMPATIBILITIES Solution/additive: Dextrose Ringer's lactate, 10% dextrose, fructose 10%, lactated Ringer's injection, amikacin, calcium chloride, calcium gluconate, cephalothin, cephapirin, chloramphenicol, chlorpromazine, cimetidine, clindamycin, codeine phosphate, dimenhydrinate, diphenhydramine, doxapram, ephedrine, fibrinolysin, glycopyrrolate, heparin, hydromorphone, insulin, levorphanol, meperidine, metaraminol, methadone, methicillin, morphine, norepinephrine, penicillin G, prochlorperazine, promazine, promethazine, sodium bicarbonate, succinylcholine, tetracycline, vancomycin. Y-site: Alfentanil, ascorbic acid, atracurium, atropine, cisatracurium, diltiazem, dobutamine, dopamine, ephedrine, epinephrine, fenoldopam, furosemide, hydromorphone, labetalol, lidocaine, lorazepam, midazolam, morphine, nicardipine, norepinephrine, pancuronium, phenylephrine, succinylcholine, sufentanil, vecuronium. Consult physician if intraarterial injection or extravasation occurs. The extravasation site will require particular attention to prevent arteritis, neuritis, and skin slough. An intraarterial injection usually causes extreme pain before patient loses consciousness.

• Store at 15°–30° C (59°–86° F). Avoid excessive heat; protect from freezing.

Adverse Effects (≥1%)

CNS: Headache, retrograde amnesia, emergence delirium, prolonged somnolence and recovery. CV: Myocardial depression, arrhythmias, circulatory depression. GI: Nausea, vomiting, regurgitation of gastric contents, rectal irritation, cramping, rectal bleeding, diarrhea. Respiratory: Respiratory depression with apnea; hiccups, sneezing, coughing, bronchospasm, laryngospasm. Body as a Whole: Hypersensitivity reactions, anaphylaxis (rare), hypothermia, thrombosis and sloughing (with extravasation); salivation, shivering, skeletal muscle hyperactivity.

Diagnostic Test Interference

Thiopental may cause decrease in I¹²³ and I¹³¹ thyroidal uptake test results.

Interactions

Drug: cns depressants, alcohol potentiate CNS and respiratory depression. phenothiazines increase risk of hypotension. Probenecid may prolong anesthesia. Herbal: Kava, valerian may potentiate sedation.

Pharmacokinetics

Onset: 30–60 sec. Duration: 10–30 min. Distribution: Distributed into muscle and liver; crosses placenta. Metabolism: In liver. Elimination: In urine. Half-Life: 12 min.

Nursing Implications

Assessment & Drug Effects

• Monitor vital signs q3–5min before, during, and after anesthetic administration until recovery and into postoperative period, if necessary.
• Report increases in pulse rate or drop in blood pressure. Hypovolemia, cranial trauma, or premedication with opioids increases potential for apnea and symptoms of myocardial depression (decreased cardiac output and arterial pressure).
• Shivering, excitement, muscle twitching may develop during recovery period if patient is in pain.

Patient & Family Education

• Onset of drug effect is rapid, with loss of consciousness within 30–60 sec.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug