From the Guidelines
Baroreceptor firing decreases in hypotension (low blood pressure).
Mechanism of Baroreceptor Firing
- Baroreceptors are stretch receptors that are activated when distended by an increase in arterial pressure, located in the aortic arch and the carotid sinus 1.
- In the context of hypotension, the decreased arterial pressure leads to reduced stretching of these receptors, resulting in decreased baroreceptor firing.
Pathophysiology of Orthostatic Hypotension
- The pathophysiology of orthostatic hypotension involves a progressive decrease in cardiac output, presumably due to venous pooling of blood, leading to unstable and decreased blood pressure 1.
- Baroreceptor malfunctioning may disorganize the discharge activity of vascular sympathetic fibers, leading to ineffective vasoconstrictor activity before syncope 1.
Clinical Implications
- The decrease in baroreceptor firing in hypotension triggers a reflex response, including cardioinhibition and vasodepression (i.e., vasodilatation), which can ultimately lead to syncope 1.
From the Research
Baroreceptor Firing in Hypotension
- In hypotension, baroreceptor firing decreases due to the reduced stretch in the arterial wall 2, 3.
- The decrease in baroreceptor firing leads to an increase in sympathetic nerve activity, which aims to increase blood pressure 4, 5.
- The baroreceptors reset to the new lower blood pressure level, allowing them to maintain their sensitivity to changes in blood pressure 3.
- The resetting of baroreceptors in chronic hypotension is stable and is not accompanied by changes in gain sensitivity, as observed in hypertension 3.
- During hypoxic hypotension, baroreceptor sensitivity decreases, leading to a reduction in the reflex capabilities to sustain simultaneous reductions in oxygen and pressure 5.