Changes in Autonomic Nerve Activity during Acute Pericardial Tamponade

Abstract

Acute experimental pericardial tamponade in anesthetized mongrel dogs produces marked alterations of autonomic reflex mechanisms. Afferent nerve activity from left ventricular receptors is inhibited during tamponade, whereas pericardial receptors are excited. Sympathetic efferent nerve activity traversing the ansae subclaviae is markedly increased during tamponade by the carotid sinus baroreceptor reflex and also by other undefined mechanisms. The increase in sympathetic activity produces a transient tachycardia and inotropic effect. A paradoxical increase in cardiac vagal efferent nerve activity occurs during the period of maximal hypotension and appears to override the normal baroreceptor reflexes. This increase in vagal efferent activity corresponds to the development of a marked bradycardia during prolonged cardiac tamponade.

Influences on the distribution of blood flow during cardiac tamponade in the conscious dog.

“…14 Sympathetic efferent nerve activity has been reported to increase during experimental cardiac tamponade, 15 and the sympathetic nervous system has been shown to be involved in sustaining cardiac performance and augmenting venous return. 16 The reninangiotensin system is known to be important in the regulation of arterial blood pressure in other conditions that result in hemodynamic deterioration.…”

Nonvagally Mediated Bradycardia during Cardiac Tamponade or Severe Hemorrhage

“…Heart rate then acceler ates almost to control levels for approximately 1 min and then a second bradycardia develops which progressively slows and eventually results in heart block, electromechanical dissociation and fibrillation. Bradycardia has been known to occur during cardiac tamponade for more than 80 years and was first described by Starling in 1897 [19], and has been studied more recently by Friedman et al [7,9], The initial bradycardia parallels the increase in cardiac vagal efferent nerve activity, which apparently is elicited by some mechanism that overrides the carotid sinus baroreceptor reflex as demonstrated by Castaner et al [5]. However, following the initial brady cardia.…”

“…The cardiac tamponade preparation was produced by making a small incision in the pericardium, inserting a polyethylene catheter into the pericardial sac and fastening the cut pericardium around the catheter with a string suture [5,7]. Tamponade was induced by injecting fixed volumes (60 cm' per increment) of warmed saline (37 °C) into the pericar dial cavity through the intrapericardia!…”

Incidence and characteristics of dysphoria in patients with cardiac tamponade

“…The authors found 99 cases in which a physician or a nurse had documented a physical or mental deterioration within 8 hours preceding the arrest. Of the 99 cases, nurses failed to notify the physician of the changes in 25 cases. An altered mental condition was noted in 19 of the 25 cases.…”

“…In this phase, the blood supply to vital organs, including the brain, is well maintained. 25 After this phase, sudden bradycardia and hypotension, phase 2, often occurs as a result of a vagal reflex called the Bezold-Jarisch reflex. This cardiac suppression is thought to be a cause of syncope.…”