In a pediatric patient rescued from cold water with pulselessness and apnea, which statement about the mammalian diving reflex is most applicable?

• A. The mammalian diving reflex provides benefits only in arctic temperatures.
• B. The child may respond to ACLS drugs given at longer intervals because the reflex shifts the oxygen-hemoglobin dissociation curve to the left.
• C. The reflex eliminates the need for defibrillation or pacing.
• D. The reflex prevents hypoxia in the myocardium.

Answer: (B)

In this situation the mammalian diving reflex can play a protective role by both reducing oxygen use and altering how oxygen is carried in the blood. When a child is submerged in cold water, the reflex causes bradycardia and peripheral vasoconstriction, which slows overall metabolism and prioritizes blood flow to the heart and brain. Cold exposure also shifts the oxyhemoglobin dissociation curve to the left, meaning hemoglobin holds onto oxygen more tightly and releases it more slowly to tissues.

With oxygen being conserved in the blood and tissue demand being reduced, the patient can tolerate longer intervals between ACLS drug administrations during resuscitation. The leftward shift supports maintaining arterial oxygen content for a longer period, even as perfusion and metabolic needs fluctuate during CPR.

The other statements don’t fit as well: benefits aren’t limited to arctic temperatures, the reflex does not remove the need for defibrillation or pacing, and while it helps preserve oxygen delivery, it doesn’t guarantee complete protection from myocardial hypoxia.