The effect of feeding on cerebral blood flow and oxygen consumption in the new‐born calf

Abstract

SUMMARY1. The effect of feeding on cerebral blood flow and oxygen consumption has been investigated in unrestrained calves between 7 and 28 days after birth.2. Cerebral blood flow was determined using an inert gas clearance technique, and oxygen consumption by the simultaneous measurement of the arterio-cerebral venous oxygen content difference.3. Cerebral blood flow increased during feeding from 74 + 4 to 116 + 9 ml. 100 g-1 min-' and reverted afterwards to the pre-feed level. No alteration in cerebral oxygen consumption occurred.4. Feeding was associated with an increase in mean arterial blood pressure and heart rate, and mild asphyxia.5. The sensitivity of the cerebral circulation to alterations in arterial PCO2 was investigated in seven calves under sodium pentobarbitone anaesthesia. In the range of arterial Pc02 15-75 mmHg the relationship was linear (r = 0-71; P < 0 001) with an average slope of 0-68 ml. 100 g-' min-mmHg Pa, co2 6. Increases in mean arterial blood pressure comparable to those occurring during feeding (96 + 6 to 159 + 8 mmHg) were produced by compression of the thoracic aorta in three calves under sodium pentobarbitone anaesthesia and were associated with an increase in cerebral blood flow from 48 + 4 to 76 + 8 ml. 100 g-1 min'. No significant change in calculated cerebral vascular resistance occurred during either feeding or aortic compression.7. These results suggest that the rise in blood pressure which occurs during feeding in the calf exceeds the autoregulatory capacity of the cerebral circulation.

Cerebral blood flow and oxidative metabolism during hypoxia and asphyxia in the new‐born calf and lamb.

“…Cerebral blood flow was measured using an inert gas clearance technique, the details of which have been described previously in their application to the calf (Gardiner, 1980b). Briefly, a bolus of hydrogen saturated saline at 38 0C is rapidly injected at the aortic root, and its clearance from cerebral venous blood recorded by a platinum electrode located in the sagittal sinus.…”

Transport of L‐phenylalanine and related amino acids at the ovine blood‐brain barrier.

“…A trephine hole was made in the mid-line immediately behind the junction of sagittal and coronal sutures. Needles were used to make two holes in the roof of the sagittal dural sinus through which were inserted a narrow-bore polyethylene cannula and a platinum electrode (Gardiner, 1980). A sintered silver-silver chloride reference electrode was positioned subcutaneously in the neck.…”

“…Measurements of rectal temperature and arterial blood gas tensions were made before and after each single pass, and arterial blood pressure was monitored continuously. Cerebral blood flow was measured by a hydrogen-clearance technique (Gardiner, 1980) and blood was taken for measurement of amino acid concentrations before each single pass.…”

“…Amino acid analysis was performed on a Chromakon 500 analyser (Kontron Instruments Ltd) using a cation-exchange resin A570 with elution by lithium buffers and subsequent colorimetric detection using ninhydrin. Cerebral blood flow (F) was determined from the slope of the cerebral venous H2 wash-out curve (Gardiner, 1980).…”

Potassium transfer from brain to blood during sustained hyponatraemia in the calf.

“…Surgical preparation was as previously described (Gardiner, 1980). Briefly, polyethylene catheters were introduced into the aorta and inferior vena cava via the saphenous vessels, the tip of one catheter being positioned just above the aortic valve.…”