Halothane has a direct effect on the SA node and conducting system leading to a slowing in impulse generation and conduction and predisposes to re-entry phenomena. Catecholamines also have potent effects on impulse conduction, so the interaction of halothane and exogenous or endogenous catecholamines may cause ventricular arrhythmias. Ventricular ectopic beats are common. However rhythm disturbances such as ventricular tachycardia or rarely ventricular fibrillation may occur. Arrhythmias occurring during halothane anaesthesia can often be resolved by reducing the concentration of halothane, ensuring adequate ventilation thereby preventing hypercarbia, increasing the inspired oxygen concentration and providing an adequate depth of anaesthesia for the surgical procedure.
Drugs increasing heart rate include ketamine, ether, atropine and pancuronium.
Drugs decreasing heart rate include opioids, beta blockers and halothane. A.B.C. Check the airway is patent Check the patient is breathing adequately or is being ventilated correctly Listen for equal air entry into both lungs Circulation - check pulse, blood pressure, oxygen saturation. Increase the inspired oxygen concentration Reduce the inspired volatile agent concentration Ensure that ventilation is adequate to prevent CO 2 build up. If so ask them to stop while you treat the arrhythmia. If the arrhythmia is causing haemodynamic instability, rapid recognition and treatment is required.