Key result
Physiological increases in intracranial pressure led to a 16 ± 2 mmHg increase in arterial pressure in normotensive sheep, but this response was severely attenuated to 5 ± 2 mmHg in those with renovascular hypertension.
Why the study?
Hypertension is associated with alterations in reflexes that maintain arterial pressure, but whether the intracranial baroreflex is altered was unknown.
Does renovascular hypertension attenuate the intracranial baroreflex (arterial pressure response to increased intracranial pressure) in an ovine model?
Does renovascular hypertension attenuate the intracranial baroreflex (arterial pressure response to increased intracranial pressure) in an ovine model?
Effect estimate: null (95% CI null)
Absolute Event Rate: 5% vs 16%
p-value: p=<0.05
This preclinical study demonstrates that the intracranial baroreflex, which normally increases arterial pressure to maintain cerebral perfusion during elevations in intracranial pressure, is severely attenuated in renovascular hypertension.
Attenuated intracranial baroreflex in hypertensive sheep should not change practice; leaves open its role in human cerebral perfusion.
We have previously shown that elevations in intracranial pressure (ICP) within physiological ranges in normotensive animals increase arterial pressure; termed the intracranial baroreflex. Hypertension is associated with alterations in reflexes which maintain arterial pressure however, whether the intracranial baroreflex is altered is not known. Hence, in the present study, we tested the hypothesis that in hypertension, physiological increases in ICP would not be accompanied with an increase in arterial pressure. Renovascular hypertension was associated with no change in heart rate, renal blood flow or ICP levels compared to the normotensive group. ICV infusion of saline produced a ramped increase in ICP of 20 ± 1 mmHg. This was accompanied by an increase in arterial pressure (16 ± 2 mmHg) and a significant decrease in renal vascular conductance. ICV infusion of saline in the hypertensive group also increased ICP (19 ± 2 mmHg). However, the increase in arterial pressure was significantly attenuated in the hypertensive group (5 ± 2 mmHg). Ganglionic blockade abolished the increase in arterial pressure in both groups to increased ICP. Our data indicates that physiological increases in ICP lead to increases in arterial pressure in normotensive animals but this is severely attenuated in renovascular hypertension.
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Vari et al. (2021) studied Renovascular hypertension (n=12). Intracerebroventricular (ICV) infusion of saline to increase intracranial pressure vs. Normotensive sham group was evaluated on Increase in arterial pressure in response to a physiological increase in intracranial pressure (null, 95% CI null, p=<0.05). Physiological increases in intracranial pressure led to a 16 ± 2 mmHg increase in arterial pressure in normotensive sheep, but this response was severely attenuated to 5 ± 2 mmHg in those with renovascular hypertension.
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