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 efferent 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 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 also 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]}} this reflex takes place even when chemicals like nicotine is injected into the body.

History[edit]

It is named after Albert von Bezold and Adolf Jarisch Junior.[7]

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. ^ Katz, Arnold M. (2001). Physiology of the heart (3. ed. ed.). Philadelphia [u.a.]: Lippincott Williams & Wilkins. p. 595. ISBN 0-7817-1548-2. 
  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. ^ synd/3165 at Who Named It?