Baroreceptor Reflex (Carotid Sinus Reflex)
Responsible for the maintenance of blood pressure
Important role during acute blood loss and shock
Volatile anesthetics (particularly halothane) inhibit the heart rate component.
Concomitant use of calcium channel blockers, ACE inhibitors, or PDE inhibitors will lessen the cardiovascular response.
Patients with chronic hypertension often exhibit perioperative circulatory instability as a result of a decrease in their baroreceptor reflex response
Chemosensitive cells in the carotid bodies and the aortic body.
Sinus nerve of Hering and vagus nerve
Chemosensitive area of the medulla
At PaO2 <50 mm Hg or in acidosis
respiratory centers stimulated and increasing ventilatory drive.
Activation of the parasympathetic system
reduction in heart rate and myocardial contractility
stretch receptors located in the right atrial wall and the cavoatrial junction
vagal afferent signals
Cardiovascular center in the medulla
↑ right-sided filling pressure inhibits parasympathetic activity →↓ heart rate.
Direct effect on the SA node by stretching the atrium.
Depends on the underlying heart rate before stimulation.
chemoreceptors and mechanoreceptors within the LV wall
↑ parasympathetic tone
Noxious ventricular stimuli induces the triad of hypotension, bradycardia, and coronary artery dilatation.
Implicated in cardiovascular conditions
Myocardial ischemia or infarction
Less pronounced in patients with
Valsalva maneuver → ↓CO and BP.
Sensed by baroreceptors → sympathetic stimulation
↑heart rate and myocardial contractility.
When the glottis opens, venous return ↑ →↑BP.
Sensed by baroreceptors → stimulate parasympathetic efferent pathways to the heart.