TY - JOUR
T1 - Cerebral and peripheral circulatory responses ro intracranial hypertension in fetal sheep
AU - Harris, A. P.
AU - Koehler, R. C.
AU - Gleason, C. A.
AU - Douglas Jones, M.
AU - Traystman, R. J.
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 1989
Y1 - 1989
N2 - Fetal head compression during normal labor can increase intracranial pressure (ICP). We studied the cerebral and peripheral blood flow responses to ICP elevation in utero in chronically catheterized fetal sheep using the radiolabeled microsphere technique. ICP was elevated, stepwise, in increments of 6 ± 1 mm Hg by infusion of artificial cerebrospinal fluid into a lateral ventricle. When ICP was raised to within 28 mm Hg of baseline mean arterial blood pressure (i.e., ICP above 22 mm Hg), arterial pressure began to increase. Above this ICP level, up to 41 mm Hg, mean cerebral perfusion pressure was maintained by equivalent increases in arterial pressure. Cerebral blood flow and O2 uptake at the highest ICP levels were not different from baseline values. Changes in peripheral organ blood flow were graded according to the level of ICP. At the highest level (ICP = 41 mm Hg), renal, gastrointestinal, and skin blood flow decreased by 68%, 69%, and 65%, respectively. Myocardial and adrenal blood flow doubled, whereas heart rate and cardiac output were unchanged. Placental blood flow increased in proportion to arterial pressure. Arterial plasma epinephrine, norepinephrine and arginine vasopressin increased by nearly two orders of magnitude. Therefore, as ICP approaches baseline mean arterial pressure, fetal lambs are capable of sustaining cerebral perfusion by initiating profound visceral vasoconstriction without curtailing placental blood flow. Since cerebral O2 uptake was maintained, there is no evidence that stimulation of the peripheral response requires pronounced cerebral ischemia. This highly developed Cushing response may be important for ensuring cerebral viability when the fetal head is compressed during parturition.
AB - Fetal head compression during normal labor can increase intracranial pressure (ICP). We studied the cerebral and peripheral blood flow responses to ICP elevation in utero in chronically catheterized fetal sheep using the radiolabeled microsphere technique. ICP was elevated, stepwise, in increments of 6 ± 1 mm Hg by infusion of artificial cerebrospinal fluid into a lateral ventricle. When ICP was raised to within 28 mm Hg of baseline mean arterial blood pressure (i.e., ICP above 22 mm Hg), arterial pressure began to increase. Above this ICP level, up to 41 mm Hg, mean cerebral perfusion pressure was maintained by equivalent increases in arterial pressure. Cerebral blood flow and O2 uptake at the highest ICP levels were not different from baseline values. Changes in peripheral organ blood flow were graded according to the level of ICP. At the highest level (ICP = 41 mm Hg), renal, gastrointestinal, and skin blood flow decreased by 68%, 69%, and 65%, respectively. Myocardial and adrenal blood flow doubled, whereas heart rate and cardiac output were unchanged. Placental blood flow increased in proportion to arterial pressure. Arterial plasma epinephrine, norepinephrine and arginine vasopressin increased by nearly two orders of magnitude. Therefore, as ICP approaches baseline mean arterial pressure, fetal lambs are capable of sustaining cerebral perfusion by initiating profound visceral vasoconstriction without curtailing placental blood flow. Since cerebral O2 uptake was maintained, there is no evidence that stimulation of the peripheral response requires pronounced cerebral ischemia. This highly developed Cushing response may be important for ensuring cerebral viability when the fetal head is compressed during parturition.
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U2 - 10.1161/01.RES.64.5.991
DO - 10.1161/01.RES.64.5.991
M3 - Article
C2 - 2706763
AN - SCOPUS:0024590136
SN - 0009-7330
VL - 64
SP - 991
EP - 1000
JO - Circulation research
JF - Circulation research
IS - 5
ER -