Managing a vasovagal reaction

Nursing, Apr 2001 by Hadaway, Lynn C

YOU'RE INSERTING a peripheral I.V. catheter in Tom Harris, 28, who needs LV. fluids before an outpatient surgical procedure. He has no allergies or chronic illnesses.

Mr. Harris is sitting on the edge of the bed and appears anxious as you explain the venipuncture procedure. His veins look healthy, but your first attempt at cannulation is unsuccessful. You succeed on the second attempt, but he immediately becomes diaphoretic and pale and complains of nausea and dizziness.

You quickly help him lie down on the bed and take his vital signs. His pulse is 50 and his BP is 90/40, compared with initial readings of 84 and 120/70. He's sweating and shivering.

Mr. Harris is having a vasovagal reaction. Research has shown that patients under age 40 and those who are sitting during the procedure are at a greater risk for vasovagal reactions than older patients and those who are lying down during the procedure. Other risk factors include a history of fainting, multiple venipuncture attempts, and lengthy cannulation procedures.

Paradoxical reaction

Vasovagal or neurocardiogenic syncope is caused by a malfunction in the autonomic nervous system. Normally, when a person is upright, decreased venous return to the heart triggers a sympathetic response. Baroreceptors in the carotid arteries and aortic arch, and C-fibers in the heart signal the brain to produce more epinephrine, which raises the heart rate and causes vasoconstriction. These responses increase BP and cardiac output. Anxiety also triggers this normal response.

In some people, however, pain or emotional stress causes vigorous left ventricular contractions that activate cardiac mechanoreceptors and the vagus nerve, interrupting the normal sympathetic response. This parasympathetic stimulation causes vasodilation and decreased heart rate, lowering BP further and leading to near syncope or syncope.

Additional signs and symptoms of a vasovagal episode include complaints of feeling hot or cold, vomiting, and shivering.

Your interventions

Although most episodes of vasovagal syncope are benign and self-limiting, some cases can result in asystole. A patient who loses consciousness for more than a few seconds during a vasovagal reaction may need IN. fluids and atropine.

During your initial assessment, ask the patient about previous fainting episodes; someone with a history of fainting is seven-and-a-half times more likely to have a vasovagal reaction during venipuncture. Position such a patient supine for venipuncture because he's eight times more likely to have a vasovagal reaction if he's sitting.

An expert in venipuncture should perform cannulations for patients at high risk for vasovagal reactions. Reducing the number and duration of cannulation procedures also helps.

As Mr. Harris relaxes, his vital signs return to normal. Teach him to tell future health care providers about his history of vasovagal reaction to prevent problems.

BY LYNN C. HARDAWAY, RN,C, CRNI, MEd Principal

Lynn Hadaway Associates, Inc. * Milner, Ga.