A method of improving brain function in a hypothermic patient is provided. The method comprises administering to the patient an amount of a fibroblast growth factor 21 (FGF21) effective to increase RNA binding motif 3 (RBM3) production in nerve cells of the patient. The method is useful, for example, where the patient is or will be undergoing cardiac surgery or spinal surgery, such as requiring deep hypothermia circulatory arrest (DHCA), or is subject to an emergency preservation and resuscitation (EPR) method, or where a patient suffers from mild/moderate/severe traumatic brain injury (TBI), ventricular fibrillation cardiac arrest (VFCA), subarachnoid hemorrhage (SAH), subdural hematoma (SH), cerebral vasospasm, neonatal abusive head trauma (a.k.a. shaken baby syndrome), neonatal hypoxic ischemic encephalopathy (HIE), asphyxia cardiac arrest (ACA), treatment of spinal injury, prophylaxis in spinal surgery, stroke, and drug overdose.