Responses to experimental subarachnoid hemorrhage in the spontaneously breathing primate

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Abstract
The pathophysiological responses to experimental subarachnoid hemorrhage (SAH) were investigated in 20 spontaneously breathing cynomolgus monkeys. Four different volumes of fresh autogenous blood were used: 1.0, 1.33, 1.67 and 2.0 cm3/kg. Five other animals had injection of 1.67 cm3/kg of mock CSF. Cerebral blood flow (CBF) was measured using the Xe-133 clearance technique. Respiratory rate and tidal volume were monitored by a Vertek pneumotach. The reduction of CBF after the SAH became more pronounced with increasing volumes of subarachnoid blood. The CBF remained reduced despite a return to normal of the cerebral perfusion pressure. Increasing SAH volumes were associated with greater abnormalities in the respiratory pattern, consisting of apnea and hyperventilation. These larger volumes were also associated with hypoxemia. Morbidity and mortality increased with increasing volumes of SAH, and are believed to be the result of a combination of decreased CBF, respiratory center disturbances, and pulmonary diffusion defects.