anoxic-ischaemic encephalopathy

anoxic-ischaemic encephalopathy

An encephalopathy caused by a lack of oxygen to the brain, due to hypotension and/or respiratory failure.

Clinical findings
Mild hypoxias cause inattentiveness, impaired judgment and incoordination. In severe hypoxia or anoxia, as in cardiac arrest, consciousness is lost within seconds, but recovery will be complete if cardiorespiratory function is restored within 5 minutes; after 5 minutes there is serious and permanent injury to the brain, especially to the globus pallidus, cerebellum, hippocampus and the “border zone regions” of the parieto-occipital lobes. As a general rule, if there is no loss of consciousness, then permanent brain damage is rare. Intact brainstem function (ciliospinal, oculovestibular and pupillary light responses and intact doll's-head eye movements) usually have a better outlook; absence of these reflexes and pupils fixed to light indicate a poor prognosis.

Aetiology
• Acute myocardial infarction.
• Cardiac arrest.
• Haemorrhage with shock and circulatory collapse.
• Shock.
• Asphyxia (drowning, strangulation, aspiration of vomitus or blood, compression of the trachea by haemorrhage, surgery or foreign bodies).
• Diseases that paralyse the muscles of respiration or compromise the CNS respiratory drive (trauma, vascular disease in brain, epilepsy), causing respiratory failure followed by cardiac failure.
• Carbon monoxide poisoning.