Continuous monitoring of the electrocardiogram provides an opportunity for the veterinary surgeon to perform the surgical procedure in a safe and controlled manner. Arrhythmias can usually be eliminated by lowering the concentration of anesthetic and administering additional oxygen. Antiarrhythmic drugs are required when these measures do not control the problem and when surgery cannot be stopped. If a disturbance cannot be abolished or controlled with medication, the surgeon must weigh the potential gain of surgery against the potential risks of the arrhythmia.