Postanaesthetic cerebral necrosis in five horses.

This research article presents a study where five adult horses developed acute neurological signs and cerebral necrosis after being anaesthetised. The majority underwent abdominal surgery for colic, one had repeated orthopedic interventions, all encountered complications during anaesthesia such as hypercapnea and hypoxaemia, which caused predominantly prosencephalic disturbances like blindness, abnormal behaviour and generalised seizures.

Study Overview

• The study focuses on five adult horses that were anaesthetized for various procedures – four for abdominal surgery due to colic and one that underwent repeated orthopaedic operations.
• Post-operation, these horses exhibited severe neurological signs including bilateral blindness with normal pupillary light responses, abnormal behaviour that varied from propulsive pacing to head pressing, profound lethargy, and generalised seizures.
• The onset of these symptoms varied between five hours and seven days after the surgery and led to the euthanisation of the horses between 24 hours and three weeks following these severe signs.

Findings

• A gross examination of the brains of three horses revealed patchy malacia or softening of the cerebral grey matter and discolouration of the adjacent white matter. This suggested extensive necrosis or death of brain tissue.
• Microscopic examination of the brain tissue further disclosed lesions that ranged from laminar neuronal necrosis in the grey matter of the cerebral cortex to more diffuse necrosis of the cortex and underlying white matter.

Possible Causes

• Four of the five horses had experienced a period of hypercapnea, an excess level of carbon dioxide in the blood, while they were anaesthetised.
• Two of these horses (with a possible third) also experienced hypoxaemia or a deficiency of oxygen in arterial blood.
• Both conditions can cause substantial neurological dysfunction which researchers believe could have led to the observed pathological changes post-anaesthesia.

Implications of the Study

• This research indicates that prolonged anaesthesia could lead to severe neurological complications in horses. There was a correlation seen between the occurrence of hypercapnea, hypoxaemia and the development of acute neurological signs and cerebral necrosis.
• Future studies should consider the impact of these conditions during anesthetic procedures, aiming to control them effectively and possibly reducing the incidence of post-anaesthetic cerebral necrosis in equines.