The exact mechanism is unclear; however, it is suggested that 5-hydroxytryptamine (5-H[T.sub.3])-receptor antagonism during the sympathectomy induced by spinal blockade may decrease the risk of mechanoreceptor activation in the left ventricle, which could have resulted in the subsequent activation of the Bezold-Jarisch reflex
, with hypotension and bradycardia.
[26,27] This can be explained by the fact that fentanyl can cause hypotension and bradycardia due to activation of the Bezold-Jarisch reflex
triggered by a reduced cardiac venous return in combination with affective mechanisms such as pain or fear and Propofol being venodilatory.
The Bezold-Jarisch reflex
. A historical perspective of cardiopulmonary reflexes.
Lastly, patients with PE may develop a vasovagal-like reaction, such as the Bezold-Jarisch reflex
, which results in transient arterial hypotension and cerebral hypoperfusion.
The responses to the stimulation of chemosensitive cardiopulmonary receptors (the Bezold-Jarisch reflex
) were determined by a bolus injection of Phenylbiguanide (PBG) at a dose of 5.0 mg x [kg.sup.-1].
According to Rea and Thames (1993), the hypotension is often the result of a vasodepressor reaction, precipitated by the Bezold-Jarisch reflex
. This reflex, triggered by numerous psychological stressors (Sledge, 1978), originates in the heart, where sensory receptors respond to mechanical and chemical stimuli by increasing the C-fiber vagal afferent signaling to the brain.
The inhibitory reflex called Bezold-Jarisch reflex
is triggered when sensory receptors are simulated by mechanical stretch.
It was formerly believed that the Bezold-Jarisch reflex
was the triggering factor for neurocardiogenic syncope.
The mechanisms of SND during exercise are thought to be mainly due to increased provocation of the Bezold-Jarisch reflex
caused by inferior ischemia or direct sinus node ischemia or coronary angiography or intrinsic sinus node dysfunction.
In this way, another important finding in our research was that there was restoration of the baroreflex bradycardia and tachycardia corroborating with others investigators that demonstrated that physical training also improves the baroreflex control (Liu et al., 2002), chemoreflex, and the Bezold-Jarisch reflexes
(Pliquett et al., 2003; Zhao et al., 1996) in experimentally induced heart failure, and hypertensive humans and rats (Brum et al., 2000; Somers et al., 1988).