Halothane

Halothane in Dogs and Cats: Uses, Dosage and Side Effects

Overview

• The mechanism of action of volatile anaesthetic agents is not fully clarified.

Uses of Halothane

• Induction and maintenance of anaesthesia.

Dose of Halothane in Dogs and Cats

Dogs, Cats:

• The expired concentration required to maintain surgical anaesthesia in 50% of recipients is 0.8–1.0% in animals (minimum alveolar concentration).
• Administration of other anaesthetic agents and opioid analgesics reduces the dose requirement of halothane, therefore, the dose should be adjusted according to individual
  requirement.
• Halothane at 3–4% concentration is required to induce anaesthesia in unpremedicated patients.

Side Effects of Halothane in Dogs and Cats

• Dose-dependent hypotension is caused by a decrease in heart rate and myocardial contractility, albeit these side effects fade over time.
• Lowers blood flow to the liver.
• In the presence of other arrhythmogenic variables, such as catecholamines, hypoxia, and hypercarbia, halothane enhances the formation of ventricular arrhythmias.
• Halothane passes through the placental barrier and affects babies delivered through caesarean section.
• Up to 25% of halothane breathed is oxidatively metabolised by hepatic cytochrome.

Contraindications of Halothane in Dogs and Cats

• Do not use in patients with liver disease

Some Notes:

• Sedatives, opioid agonists and N2O reduce the concentration of halothane required to achieve surgical anaesthesia.
• Because halothane is extremely potent and highly volatile, it should only be given using a properly calibrated vaporizer.
• Because it is more soluble in blood than isoflurane and sevoflurane, it causes slower induction and recovery from anaesthesia than the other drugs.
• The halothane concentration required to maintain anaesthesia is determined by the other medications used in the anaesthesia protocol; the concentration should be changed based on clinical assessment of anaesthetic depth.
• In most species, MAC is around 0.9%.