Optimal temperature for selective cerebral perfusion

Objective: Although combinations of hypothermic circulatory arrest and antegrade selective cerebral perfusion are used for cerebral protection during arch surgery, there is no consensus regarding the optimal temperature during selective cerebral perfusion. This study explored the effect of different temperatures during selective cerebral perfusion on cerebral metabolism and neurologic outcome. Methods: In this blinded study, 40 pigs (19-21 kg) were randomized into 4 groups after 30 minutes of hypothermic circulatory arrest at 20°C. During a 60-minute interval of selective cerebral perfusion, with flow regulated to maintain a perfusion pressure of 50 mm Hg, pigs were perfused at 10°C, 15°C, 20°C, and 25°C. Fluorescent microspheres enabled calculation of cerebral blood flow during perfusion and recovery. Hemodynamics, intracranial pressure, cerebrovascular resistance, and oxygen consumption were also monitored. Behavioral scores were obtained for 7 days after surgery. Results: Cerebral blood flow decreased significantly (P < .002) during cooling in all groups: it was significantly higher throughout selective cerebral perfusion in the 20°C to 25°C versus the 10°C to 15°C group (P = .0001) and remained higher during recovery (P = .0001). Oxygen consumption decreased significantly with cooling (P = .0001), remained low during perfusion, and rebounded with rewarming but was significantly lower at 10°C to 15°C than at 20°C to 25°C throughout selective cerebral perfusion (P = .003) and after CPB was discontinued (P = .001). Postoperative behavioral scores were significantly better after selective cerebral perfusion at 10°C to 15°C than at 20°C to 25°C (P = .001). Conclusions: This study suggests that selective cerebral perfusion at 10°C to 15°C provides better cerebral protection than selective cerebral perfusion at 20°C to 25°C, even though oxygen consumption remains low for hours after selective cerebral perfusion at 10°C to 15°C. Prompt return of metabolism to baseline levels after hypothermic circulatory arrest/selective cerebral perfusion does not necessarily predict superior behavioral outcome.