Vasovagal Reaction

From Anvita Health Wiki

Contents 1 Introduction 2 Etiology 3 Epidemiology 4 Pathology 5 Clinical-manifestations 6 Management 7 More General Terms 8 Additional Terms 9 References

Introduction

• A form of syncope.

Etiology

• precipitating factors

• fear
• pain
• emotional stress
• prolonged standing

• predisposing factors

• fatigue
• hunger
• hot, humid environment
• bed rest

Epidemiology

• occur less frequently in the elderly

Pathology

• orthostatic stress

• pooling of blood in the lower extremities (500-800 mL)

• compensatory increased adrenergic tone
• parasympathetic reflex

• decreased preload results in stimulation of mechano- receptors in the left ventricular wall by vigorous cardiac contraction against a relatively empty ventricle
• signals sent to midbrain from left ventricular mechano- receptors resulting in withdrawal of peripheral sympathetic tone & augmentation of vagal tone
• sudden peripheral vasodilatation, especially in skeletal muscle without compensatory rise in cardiac output
• drop in blood pressure
• bradycardia may occur

Clinical-manifestations

• prodrome

• restlessness
• weakness
• pallor
• nausea
• salivation
• sweating
• yawning

• generally occurs when standing, possibly sitting
• recovery

• prompt return of consciousness when supine
• pallor, nausea, weakness & slight confusion may persist for a short time

Management

• place patient in supine position or with head in dependent postion (below heart, i.e. between legs)
• prophylaxis:

• drinking 16 oz (1 pint) of water prior to risky setting

• muscle-tensing exercises when a prodrome is sensed [5]

• hand-clasping with interlocking fingers while pulling the elbows in opposite directions
• squeezing a ball or other object
• standing leg cross-over firmly pushing in thighs while tensing abdominal muscles

• pharmacotherapy

• see neurocardiogenic vasopressor dysfunction

• prognosis:

• worse for elderly
• 16% have major morbidity/mortality within 6 months

More General Terms

• neurocardiogenic vasopressor dysfunction (NVD)

Additional Terms

• syncope

References

1. Guide to Physical Examination & History Taking, 6th edition, Bates B, JB Lippincott, Philadelphia, 1995, pg 90-91
2. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 649
3. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
4. Journal Watch 24(2):15, 2004 Lu C-C et al,Ciculation 108:2660, 2003 PMID: [1]
5. Internal Medicine News 39(8): April 15, 2006
6. Fainting: NIH Institute and Center Resources [2]

vasovagal reaction (fainting)