Cushing reflex
The Cushing reflex is an increase in blood pressure with an occasional drop in heart rate with an increase in intracranial pressure . The connection was described in 1901 by the American neurosurgeon Harvey Cushing .
formula
The brain perfusion pressure (CPP):
- CPP = MAP (mean arterial pressure) - ICP (intracranial pressure)
Pathophysiology
If the intracranial pressure increases due to a space-occupying process (e.g. bleeding , edema formation ), the perfusion pressure of the brain decreases. The cerebral blood flow and the oxygen supply to the nerve cells decrease. In order to keep the ratio of mean arterial and intracranial pressure constant, the body increases the blood pressure very strongly (up to 300 mmHg systolic possible). This in turn increases the ICP and the arterial pressure has to increase even more. In addition, the heart rate drops because the heart has to "recover" from the enormous stress. The pressure pulse occurs . The cause is an increase in sympathetic activity in the ventrolateral medulla oblongata (center of the sympathetic tone-generating efferents).
The blood pressure will eventually regulate itself. The administration of antihypertensive drugs (e.g. urapidil ) is therefore contraindicated (↓ blood pressure + urapidil → Ø pressure) unless there is active bleeding into the brain (e.g. due to a bleeding aneurysm ), in which case the Blood pressure can be lowered systolic to a maximum of 160 mmHg.
Individual evidence
- ^ H. Cushing: Concerning a definite regulatory mechanism of the vasomotor center which controls blood pressure during cerebral compression . In: Bull Johns Hopkins Hosp. Band 12 , 1901, pp. 290-292 .
