What are Vagal Maneuvers?
A vagal maneuver is an action that is taken to slow down the heart rate by stimulating the vagus nerve. The vagus nerve is the longest nerve of the autonomic nervous system and helps regulate many critical aspects of human physiology, including heart rate, blood pressure, sweating, and digestion.
Stimulation of the vagal nerve releases acetylcholine, which slows the pulse. Simple maneuvers may include holding your breath for 20 to 60 seconds, dipping your face in cold water, coughing, or tensing the stomach muscles as if simulating a bowel movement.
Patients with supraventricular tachycardia, atrial fibrillation, and other illnesses may be trained to perform vagal maneuvers on themselves. However, over-stimulation of the vagus nerve can cause fainting.
In addition to the vagal maneuvers listed above, a physician may sometimes try another vagal maneuver (known as carotid sinus massage) in the emergency room to help slow a patient’s heart rate. It should be noted that this technique should only be performed by a trained healthcare provider.
When Should ACLS Providers Use Vagal Maneuvers?
There are two types of rhythms where vagal maneuvers are recommended:
- Regular narrow complex rhythms, minus sinus tachycardia.
- Narrow QRS with a regular rhythm, such as SVT.
Regular Narrow Complex Rhythms
It’s important that healthcare providers are able to classify the type of tachycardia (wide or narrow, regular or irregular) and implement the appropriate interventions as outlined in the Tachycardia Algorithm.
If ACLS providers notice a regular narrow complex rhythm, except sinus tachycardia, they should treat the patient with a combination of vagal maneuvers and adenosine.
Sinus tachycardia is caused by external influences on the heart, such as fever, anemia, hypotension, blood loss, or exercise. These are systemic conditions, not cardiac conditions, which is why vagal maneuvers are not recommended even though they may slow the heart rate.
If the rhythm does not convert, ACLS providers will need to monitor the patient and transport them to the next level of care or obtain expert consultation. If the patient becomes unstable, healthcare providers will need to prepare for immediate unsynchronized shock or synchronized cardioversion.
Narrow QRS with a Regular Rhythm
The therapy for narrow QRS with a regular rhythm is similar to how healthcare providers treat regular narrow complex rhythms – vagal maneuvers plus adenosine.
Vagal maneuvers and adenosine are the preferred initial interventions for terminating narrow-complex tachycardias that are symptomatic but stable and supraventricular in origin (SVT). Vagal maneuvers alone (including carotid sinus massage) will terminate about 25 percent of SVTs. Adenosine will likely be required to treat the remainder.
If SVT does not respond to vagal maneuvers, healthcare providers should administer 6mg of adenosine via rapid IV push in a large vein, like the antecubital vein, over one second. They should follow that with a 20mL saline flush and elevate that arm immediately.
If SVT does not convert within one to two minutes, ACLS providers should administer a second dose of adenosine – 12mg via rapid IV push and follow that again with a 20mL saline flush.