CPR and a boatload of epinephrine, it seems.

That passage bears quoting at length, it's where I really teared up:

> At initiation of ECMO, the boy's rhythm was asystole. The boy was rewarmed with an ECMO heat exchanger-patient gradient ≤10 °C. [...] As the patient's temperature approached 22 °C (72 °F), low-frequency and low-amplitude sinusoidal electrical deflections were noted on his electrocardiogram. As the patient continued to rewarm, these phasic electrical deflections slowly increased in frequency and amplitude. At approximately 28 °C (82 °F), sinusoidal deflections organized into more classic cardiac electrical activity reminiscent of sinus bradycardia with a wide complex. Amiodarone, calcium gluconate, magnesium sulfate, bolus epinephrine, and epinephrine and norepinephrine infusions were administered. After further rewarming, sinus bradycardia developed and ultimately progressed to normal sinus rhythm...