Cardiac arrhythmias associated with acute major haemorrhage during craniectomy in a dog

An estimated 43% of total blood volume was lost during craniectomy in a 32-kg Labrador retriever. One episode of bradycardia, followed by ventricular tachycardia occurred during surgery when the rate of haemorrhage exceeded fluid replacement. Sinus rhythm was re-established with intravenous lidocaine (1.25 mg kg^-1). Twenty-four hours later, premature ventricular complexes appeared followed by episodes of ventricular tachycardia, some requiring lidocaine treatment. Myocardial hypoxia resulting either from hypovolaemia and/or air embolism (the right transverse venous sinus was damaged during surgery) may have caused the arrhythmias. Mild intracranial hypertension may have aggravated the problem.