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CEREBRAL HYPOXIA

Cerebral hypoxia occurs when the supply of oxygen to the brain is reduced for any
reason. An acute or chronic syndrome

ETIOLOGY

All forms of hypoxia, including anemic, anoxic, histotoxic, and stagnant forms
cause some degree of cerebral hypoxia but signs referable to cerebral dysfunction
occur only when the hypoxia is severe.

The hypoxia of the brain may be secondary to a general systemic hypoxia or be

caused by lesions restricted to the cranial cavity.

Cerebral hypoxia secondary to general hypoxia

Q Poisoning by hydrocyanic acid or nitrite
o Acute heart failure in severe copper deficiency in cattle
Anesthetic accidents
o Terminally in pneumonia, congestive heart failure
o During or at birth in foals .
Cerebral hypoxia secondary to i ntracra nial lesion
- In increased intracranial pressure
- In brain edema.


PATHOGENESIS:

The central nervous system is extremely sensitive to hypoxia, and degeneration

occurs if the deprivation is prolonged for more than a few minutes.
The effects of the hypoxia vary with the speed of onset and with the severity.
When the onset is sudden there is usually a transitory period during which excitation phenomena occur and this is followed by a period of loss of function.

If recovery occurs, a second period of excitation usually develops as function returns. In more chronic cases the excitation phase is not observed, the signs being mainly those of loss of function.

These signs include dullness and lethargy when deprivation is moderate, and unconsciousness when it is severe. All forms of nervous activity are depressed but the higher centers are more susceptible than medullary centers and the pattern of
development of signs may suggest this.

CLIN ICAL FINDINGS:

Acute and chronic syndromes occur depending on the severity of the hypoxia.

Acute cerebral hypoxia is manifested by a sudden onset of paralysis of all brain functions, including tetraparesis and unconsciousness. Muscle tremor, beginning about the head and spreading to the trunk and limbs, followed by recumbency, clonic convulsions.

In chronic hypoxia there is lethargy, dullness, ataxia, weakness, blindness and

in some cases muscle tremor or convulsions.


In both acute and chronic hypoxia the signs of the primary disease will also
be evident. Cerebral hypoxia of fetal calves is thought to be a cause of weakness and failure to suck after birth, leading to the eventual death of the calf from starvation .

Clinically there is little to differentiate cerebral hypoxia from hypoglycemia or

polioencephalomalacia in which similar signs occur.

TREATM ENT

-An increase in oxygen delivery is essential and can usually only be provided by
removing the causative agent.
-A respiratory stimulant (such as doxapram) may be advantageous in acute cases and artificial respiration may be necessary and effective.