THIOPENTONE

THIOPENTONE


Introduction:
  • Ultrashort-acting barbiturate.
  • Due to rapid redistribution.
  • Careful injection technique to prevent intra arterial injection in antecubital fossa.
  • Avoided in antecubital fossa & given in veins over outer aspect of forearm only.
Actions:

  • Anticonvulsant action – 
  • DOC in neurosurgical procedures.
  • Cerebroprotection – 
  • Decreases ICT, cerebral perfusion, O2 consumption & cerebral metabolic rate.
  • DOC for cerebral protection.
  • Decreases intraocular pressure.
  • Poor analgesic.
  • Painful procedure not be done.
  • Produces hyperalgesia.
  • Poor muscle relaxant property.

Uses:

  • As anticonvulsant – DOC in neurosurgical procedures.
  • Inducing agent in anesthesia.
  • Dose for induction = 3-5 mg/ kg.
  • Medically induced coma.
  • Euthanasia – IV thiopental is rapid way accomplishing euthanasia.
  • Phobia – For desensitization.
  • Truth serum:
  • Used to uncover truth.
  • By suppressing higher cortical neurons involved in lying without affecting truth revealing centers.
  • To facilitate recall of painful repressed memories.

Contraindications

  • Acute intermittent prophyria.
  • Cardiovascular instability or shock.
  • Respiratory obstruction.
  • No availability of airway equipment
  • Status asthmaticus.
  • Pericardial Tamponade.
  • In hypovolemia & shock.
  • Avoided in antecubital fossa – To prevent intra-arterial injection complication.

Adverse effects:

  • IV injection of thiopentone is painful.
  • Hypotension due to vasodilation –-> Reflex tachycardia.
  • May result in cardiovascular collapse in presence of hypovolemia, shock or sepsis.
  • Cause respiratory depression, laryngospasm & bronchospasm.
  • Mild muscular excitatory movement (tremor, twitching, cough, hiccup).
  • Produce hypersensitivity, rash, angioedema, photosensitivity.
  • Dreadful complications on intra-arterial injection.
Intra-arterial injection of thiopentone:
  • Common with injection in antecubital vein.
  • Avoided at antecubital fossa.
  • Produces thrombosis, vasospasm ischemia, necrosis —> gangrene.
  • 1st symptom = Burning pain.
  • 1st sign = Blanching of hand due to vasospasm.
  • Prevented by given in veins over outer aspect of forearm only.

Management:

  • Leaving needle in-situ in artery.
  • Brachial block (stellate ganglion block).
  • Heparin injection – To prevent thrombosis.
  • Dilution of thiopental by injection of saline into artery.
  • Papaverine or prostacyclin injection – To relieve spasm.
  • Urokinase, streptokinase, vasodilators, steroid & lignocaine used.

Exam Important

  • Thiopentone is ultrashort-acting barbiturate due to rapid redistribution.
  • Thiopentone needs careful injection technique to prevent intra arterial injection, particularly in antecubital fossa.
  • Thiopentone injections are avoided in antecubital fossa & given in veins over outer aspect of forearm only.
  • Thiopentone has anticonvulsant action, hence DOC in neurosurgical procedures.
  • Thiopentone decreases ICT, cerebral perfusion, O2 consumption & cerebral metabolic rate & hence, cerebroprotective.
  • Thiopentone decreases IOT, has poor muscle relaxant property & is poor analgesic hence not used for painful procedure.
  • Thiopentone is used for medically induced coma & as truth serum.
  • IV injection of thiopentone is painful.
  • Thiopentone produces dreadful complications on intra-arterial injection, particularly on antecubital fossa.
  • Thiopentone injections are avoided in antecubital fossa to prevent intraarterial complications.
  • Intraarterial injection complication of thiopentone is mostly due to accidental injection into antecubital vein.
  • Intraarterial injection complication of thiopentone is prevented by given in veins over outer aspect of forearm only.
  • Intra-arterial injection of thiopentone produces thrombosis, vasospasm ischemia, necrosis leading to gangrene.
  • 1st symptom of intra-arterial injection of thiopentone is burning pain.
  • 1st sign of intra-arterial injection of thiopentone is blanching of hand due to vasospasm.
  • Intraarterial injection complication of thiopentone is managed by leaving needle in-situ in artery, brachial block (stellate ganglion block), Heparin injection preventing thrombosis, Papaverine or prostacyclin injection relieving spasm.
  • Thiopentone causes hypotension due to vasodilation, hence contraindicated in hypovolemia, shock or sepsis.
  • Thiopentone produce hypersensitivity, rash, angioedema, photosensitivity.
  • Mild muscular excitatory movement like tremor, twitching, cough, hiccup are seen with thiopentone.
  • Thiopentone is contraindicated in status asthmaticus, respiratory obstruction & in acute intermittent porphyria.
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