288 EFFECT OF HYPOVOLEMIC HYPOTENSION (HVH) ON CEREBRAL METABOLISM IN NEWBORN PIGLETS

We studied the effects of HVH on systemic and cerebral metabolism of glucose (gl.mmol/L), lactate (lac.mmol/L) and O2 content (C'O2 vol.%) in eight, 1-4 days old piglets under anesthesia during assisted ventilation. HVH was induced by exsanguination dropping t.hemean BP to 40 mmHg (50% of baseline) for 60'. Arterial (art.) venous from saggital sinus (v), lac. gl. and C'O2 and CSF lac. were measured sequentially. Cerebral blood flow (CBF) was measured with radioactive microspheres. Results: (x±SE: p values for significant difference as compared to baseline: *<0.05, **<0.01). During HVH, CSF lac., art. lac., gl. and Δ art.-v for lac. increased. The product of CBF and Δ art .-v C'O2 was constant, indicating brain oxygenation remained stable during HVH. We therefore conclude: 1) Increased art.-v lac. and CSF lac. are due to systemic increase in lac. production; 2) Therefore, increase in CSF lac. by itself does not reflect brain compromise during HVH; and 3) By changing flow and O2 extraction rates, brain maintains its oxygenation under a wide range of adverse situations.