Autonomic Mechanisms Associated with Heart Rate and Vasoconstrictor Reserves

Abstract

Introduction: Hemorrhage is accompanied by baroreflex-mediated tachycardia and vasoconstriction. The difference between baseline and maximum responses is defined as the heart rate (HR) and vasoconstrictor reserve . Objective To test the hypothesis that higher HR and vasoconstrictor reserves in subjects with high tolerance (HT) to central hypovolemia is associated with greater reserve for sympathoexcitation and vagal withdrawal compared with low tolerant (LT) subjects. Methods: R R intervals (RRI), systolic arterial pressure (SAP), estimated stroke volume, and muscle sympathetic nerve activity (MSNA) were measured during lower body negative pressure (LBNP) designed to induce pre-syncope. Subjects with tolerance </= 60 mmHg LBNP were classified as LT (n = 22) while subjects who tolerated LBNP levels >60 mmHg were classified as HT (n = 56). Spontaneous cardiac baroreflex sensitivity (BRS) was assessed via RRISAP down down sequences.

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Document Details

Document Type
Technical Report
Publication Date
Nov 15, 2011
Accession Number
ADA618698

Entities

People

  • Caroline A Rickards
  • Kathy L. Ryan
  • Victor A Convertino

Organizations

  • United States Army Institute of Surgical Research

Tags

DTIC Thesaurus Topics

  • Blood
  • Blood Volume
  • Cardiac Arrhythmias
  • Cardiovascular Physiological Phenomena
  • Cardiovascular System
  • Combat Casualty Care
  • Data Analysis
  • Health Services
  • Heart Rate
  • Hemorrhage
  • Hemorrhagic Shock
  • Hypovolemia
  • Medical Personnel
  • Monitoring
  • Statistical Analysis
  • Vascular Diseases
  • Wounds And Injuries

Fields of Study

  • Medicine

Readers

  • Cardiovascular Physiology