Normothermia is protective during infrarenal aortic surgery

Purpose: Mild hypothermia has been suggested to be protective against tissu e ischemia during aortic operations. However, recent studies have documente d detrimental cardiac effects of hypothermia during a variety of operative procedures. The influence of different warming methods and the impact of hy pothermia during standard aortic procedures was assessed. Methods: One hundred patients who underwent repair of infrarenal aortic ane urysms or aortoiliac occlusive disease were prospectively randomized into 2 groups, receiving either a circulating water mattress or a forced air warm ing blanket. Adjuvant warming methods were standardized. The day before sur gery, 48-hour Holter monitors were applied and interpreted by a cardiologis t blinded to the treatment. Randomization resulted in equivalent groups wit h regard to patient history, indications for surgery, body mass index, leng th of surgery, and fluid requirements. Results: Core temperatures were significantly warmer during surgery (36.3 d egrees C +/- 0.7 degrees C vs 35.4 +/- 0.8 degrees C) and after surgery (36 .4 degrees C +/- 0.7 degrees C vs 35.6 degrees C +/- 0.9 degrees C) in pati ents with forced air warming (P < .001). The circulating water mattress gro up had significantly more metabolic acidosis perioperatively (P = .03). Pos toperative length of stay, cardiac complications, and death rates were not significantly different. Subgroup analysis of 83 aneurysm patients comparin g normothermia with hypothermia (temperature less than 36 degrees C) on arr ival to the recovery room identified decreased cardiac output (P = .02), th rombocytopenia (P = .02), elevated prothrombin time (P = .04), and inferior Acute Physiology and Chronic Health Evaluation (APACHE) II scores (P < .00 1) in the hypothermic group, Holter analysis revealed more sinus tachycardi a (ST) segment changes and ventricular tachycardia in hypothermic aneurysm patients (P = .05). Conclusion: Patients treated with forced air blankets had significantly les s metabolic acidosis and were kept significantly warmer than those treated with circulating water mattresses. Patients with aneurysms that were kept n ormothermic had a significantly improved clinical profile, with fewer cardi ac events on the Holter recordings. We therefore conclude that (1) normothe rmia is protective for infrarenal aortic surgical patients; and (2) forced air warming blankets provide improved temperature maintenance compared with circulating water mattresses.