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Eur J Cardiothorac Surg 2007;32:514-520. doi:10.1016/j.ejcts.2007.06.013
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved

Avoidance of hemodilution during selective cerebral perfusion enhances neurobehavioral outcome in a survival porcine model

^a Department of Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, NY 10029, USA
^b Department of Neurosurgery, Mount Sinai School of Medicine, New York, NY 10029, USA
^c Department of Anesthesiology, Division of Biostatistics, Mount Sinai School of Medicine, New York, NY 10029, USA

Received 25 April 2007; received in revised form 7 June 2007; accepted 11 June 2007.

^_* Corresponding author. Address: 5 Mead Close, Colton, Leeds LS15 9JT, United Kingdom. Tel.: +44 7774961207. (Email: jameschalstead{at}yahoo.co.uk).

Introduction: The ideal hematocrit (HCT) level during hypothermic selective cerebral perfusion (SCP) – to ensure adequate oxygen delivery without excessive perfusion – has not yet been determined. Methods: Twenty pigs (26.0 ± 2.6 kg) were randomized to low or high HCT management. The cardiopulmonary bypass (CPB) circuit was primed with crystalloid in the low HCT group (21 ± 1%), and with donor blood in the high HCT group (30 ± 1%). Pigs were cooled to 20 °C and SCP was carried out for 90 min. During rewarming, whole blood was added in the low HCT group and crystalloid in the high HCT group to produce equivalent HCT levels by the end of the procedure. Using fluorescent microspheres and sagittal sinus sampling, cerebral blood flow (CBF) and oxygen metabolism (CMRO₂) were assessed at baseline, after cooling, at two points during SCP (30 and 90 min), and at 15 min and 2 h post-CPB. In addition, a range of physiological and metabolic parameters, including intracranial pressure (ICP), were recorded throughout the procedure. The animals’ behavior was videotaped and assessed blindly for 7 days postoperatively (maximum score = 5). Results: HCT levels were equivalent at baseline, 2 h post-CPB, and at sacrifice, but significantly different (p < 0.0001) during cooling and SCP. Mean arterial pressure, pH and pCO₂, and CMRO₂ were equivalent between groups throughout. ICP was similar in the two groups throughout cooling, SCP, and rewarming, but was significantly higher in the low HCT animals after the termination of CPB. CBF was similar at baseline, but thereafter markedly higher in the low HCT group. Neurobehavioral performance was significantly better in the high HCT animals (median score 3.5 vs 4.5 on day 3, and 4.5 vs 4.75 on day 7, p = 0.003). Conclusions: Higher HCT levels for SCP produced a significantly superior functional outcome, suggesting that the higher CBF with a lower HCT may be injurious, possibly because of an increased embolic load.

Key Words: Great vessels • Cerebral protection • Hematocrit