Expansion
Bradycardia, peripheral vasoconstriction and splenic contraction
Expansion
Triggered by cold water on the face, especially around the nose and forehead, with breath-holding.
- Afferent: ophthalmic division of the trigeminal nerve
- Efferent: vagus to the heart, sympathetic to the vessels
Three components, all oxygen-conserving:
- Bradycardia, which may be profound
- Peripheral vasoconstriction, diverting flow to heart and brain
- Splenic contraction, releasing stored red cells
The reflex is strongest in infants and in diving mammals, and is more pronounced with colder water.
Two clinical applications. It is used as a vagal manoeuvre in supraventricular tachycardia, particularly in children. And it partly explains survival after prolonged cold water drowning, since the combination of reflex flow redistribution and rapid hypothermic cerebral cooling can protect the brain, which is why resuscitation is continued until the patient is rewarmed.