Objective: Mounting evidence suggests that mild to moderate hypothermia can mitigate neurologic and myocardial injury. The speed of induction appears to be a key factor in determining its efficacy. However, even when the fastest currently available cooling techniques are used, reaching target temperatures takes at least 2 hrs and usually longer. We hypothesized that infusion of refrigerated fluids could be a safe accessory method to increase cooling speed.
Design: Prospective intervention study.
Setting: University teaching hospital.
Patients: One hundred thirty-four patients with various types of neurologic injury (postanoxic encephalopathy, subarachnoid hemorrhage, or traumatic brain injury).
Measurements and main results: Hypothermia was induced in 134 patients with various types of neurologic injury, by means ice-water cooling blankets and infusion of refrigerated (4 degrees C) saline (110 patients) or saline and colloids (24 patients). An average volume of 2340 +/- 890 mL of refrigerated fluids was infused in 50 mins. Core temperatures decreased from 36.9 +/- 1.9 degrees C to 34.6 +/- 1.5 degrees C at t = 30 mins and to 32.9 +/- 0.9 degrees C at t = 60 mins (target temperature: 32 degrees C-33 degrees C). Monitoring of blood pressure, heart rhythm, central venous pressure, blood gasses, electrolyte and glucose levels, and platelet and white blood cell count revealed no additional adverse effects. Mean arterial pressure increased by 15 mm Hg, with larger increases in blood pressure occurring in hemodynamically unstable patients. No patient developed pulmonary edema.
Conclusions: Induction of hypothermia by means of cold-fluid infusion combined with ice-water cooling blankets is safe, efficacious, and quick. Because the speed of cooling is important to increase its protective effects, we recommend that cold-fluid infusion be used in all patients treated with induced hypothermia. This should be combined with another method to safely and accurately maintain hypothermia once target temperatures have been reached.