Halothane

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Halothane :-

is a potent inhalational anaesthetic. It is a clear, colourless liquid. It is a poor analgesic, but when co-administered with nitrous oxide and oxygen, it is effective and convenient. It is inexpensive and used world-wide, although only infrequently in the UK. Although apparently simple to use, its therapeutic index is relatively low and overdose is easily produced. Warning signs of overdose are bradycardia, hypotension and tachypnoea. Halothane produces moderate muscular relaxation, but this is rarely sufficient for major abdominal surgery. It potentiates most non-depolarizing muscle relaxants, as do other volatile anaesthetics. Adverse effects • Cardiovascular: • ventricular dysrhythmias; • bradycardia mediated by the vagus; • hypotension; • cerebral blood flow is increased, which contraindicates its use where reduction of intracranial pressure is desired (e.g. head injury, intracranial tumours). • Respiratory: respiratory depression commonly occurs, resulting in decreased alveolar ventilation due to a reduction in tidal volume, although the rate of breathing increases. • Hepatic. There are two types of hepatic dysfunction following halothane anaesthesia: mild, transient subclinical hepatitis due to the reaction of halothane with hepatic macromolecules, and (very rare) massive hepatic necrosis due to formation of a hapten–protein complex and with a mortality of 30–70%. Patients most at risk are middle-aged, obese women who have previously (within the last 28 days) had halothane anaesthesia. Halothane anaesthesia is contraindicated in those who have had jaundice or unexplained pyrexia following halothane anaesthesia, and repeat exposure is not advised within three months. • Uterus: halothane can cause uterine atony and postpartum haemorrhage.
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