Bezold–Jarisch reflex

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The Bezold–Jarisch reflex involves a variety of cardiovascular and neurological processes which cause hypopnea (overly shallow breathing or an abnormally low respiratory rate) and bradycardia (abnormally low resting heart rate).[1]

Physiology[edit]

Prolonged upright posture results in some degree of pooling of blood in the lower extremities that can lead to diminished intracardiac volume. This phenomenon is exacerbated if the individual is dehydrated. The resultant arterial hypotension is sensed in the carotid sinus baroreceptors, and afferent nerve fibers from these receptors trigger autonomic signals that increase cardiac rate and contractility. However, pressure receptors in the wall and trabeculae of the underfilled left ventricle may then sense stimuli, activating high-pressure C-fiber afferent nerves from these receptors. They may respond by sending signals that trigger paradoxical bradycardia and decreased contractility, resulting in additional and relatively sudden arterial hypotension. The bradycardia reaction to acetic acid veratril in the cardiac pacemaker region was first described by von Bezold. Jarisch identified the reaction as chemoreceptor reflex via the vagus nerve, relayed in the nucleus tractus solitarius.

The Bezold–Jarisch reflex is responsible for the sinus bradycardia that commonly occurs within the first 60 minutes following an acute myocardial infarction,[2] and explains the occurrence of AV node block in the context of acute posterior or inferior myocardial infarction.[3] Bradycardia in this setting may be treated with atropine.

It usually occurs in nitrate therapy and use of serotonin agonists.[4] The Bezold–Jarisch reflex has been suggested as a possible cause of profound bradycardia and circulatory collapse after spinal anesthesia.[5] Also, it is one of the complications of interscalene brachial plexus block.[6] The reflex occurs with several biologically active chemicals, like nicotine and capsaicin,[7] when reaching sensitive areas.

History[edit]

It is named after Albert von Bezold and Adolf Jarisch Junior.[8] The significance of the discovery is the first recognition of chemical (non-mechanical) reflexes.

References[edit]

  1. ^ Salo LM, Woods RL, Anderson CR, McAllen RM (August 2007). "Nonuniformity in the von Bezold-Jarisch reflex". Am. J. Physiol. Regul. Integr. Comp. Physiol. 293 (2): R714–20. doi:10.1152/ajpregu.00099.2007. PMID 17567718. 
  2. ^ Goldman, Lee; Anderson, Jeffrey L. "ST SEGMENT ELEVATION ACUTE MYOCARDIAL INFARCTION AND COMPLICATIONS OF MYOCARDIAL INFARCTION". Goldman: Goldman's Cecil Medicine (24th ed.). Saunders, an imprint of Elsevier Inc. p. 444. ISBN 978-1-4377-1604-7. 
  3. ^ cite book|last=Katz|first=Arnold M.|title=Physiology of the heart|year=2001|publisher=Lippincott Williams & Wilkins|location=Philadelphia [u.a.]|isbn=0-7817-1548-2|page=595|edition=3. ed.
  4. ^ eMedicine - Syncope : Article by M Silvana Horenstein, MD
  5. ^ [Tsai T. & Greengrass R. (2007). Textbook of Regional Anesthesia and Acute Pain Management: Spinal Anesthesia. (A. Hadzic, Ed.). New York: McGraw Hill Medical.
  6. ^ Miller's Anesthesia Ch.52 Pg. 1642
  7. ^ Koji Kashihara (Nov 2009). "Roles of Arterial Baroreceptor Reflex During Bezold-Jarisch Reflex". Curr Cardiol Rev. 5(4): 263–267. 
  8. ^ synd/3165 at Who Named It?