Successful management of two horses with suspected pulmonary haemorrhage in recovery from general anaesthesia.

Abstract

A 24 year old warmblood mare (case 1) and a 12 year old Holsteiner gelding (case 2) were anaesthetized for bursoscopy and phacoemulsification, respectively. Both were premedicated with intramuscular acepromazine (30 μg kg). The horses were sedated with intravenous (IV) medetomidine (7-9 μg kgto effect), before anaesthetic induction with ketamine-diazepam. Anaesthesia was maintained with isoflurane in a mixture of oxygen and medical air, alongside a medetomidine constant rate infusion at 3.5 μg kghour. In recovery, 3 and 5 μg kgof medetomidine were administered IV to cases 1 and 2, respectively. After tracheal extubation, both patients developed haemoptysis exceeding an estimated 5% loss of total blood volume. This gradually ceased after IV injection of tranexamic acid (2 mg kg, both cases) and acepromazine (case 1, 15 μg kg; case 2, 20 μg kg), administered while the horses were recumbent. Oxygen insufflation was commenced on entry to the recovery box, initially via the trachea, and then the nasopharynx postextubation, until the horses stood. Both cases survived to discharge. Postanaesthetic pulmonary haemorrhage was suspected; multiple causative factors have been proposed for this rare complication. These include increased pulmonary vascular resistance secondary to αadrenoceptor agonist use, hypoxaemia and high catecholamine levels, increased intrathoracic pressures owing to respiratory obstruction and coughing, and underlying, often subclinical, respiratory disease. Particular to case 1 and 2 was the rapid injection of higher than usual doses of medetomidine in recovery owing to persistent nystagmus. Resultant pulmonary hypertension may have caused the haemorrhage observed.