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Ann Thorac Surg 2006;81:625-633
© 2006 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Cardiac Output Augmentation During Hypoxemia Improves Cerebral Metabolism After Hypothermic Cardiopulmonary Bypass

Division of Pediatric Cardiac Surgery, Doernbecher Children's Hospital, Oregon Health & Science University, Portland, Oregon

Accepted for publication June 10, 2005.

^_* Address correspondence to Dr Ungerleider, Cardiothoracic Surgery, Oregon Health & Science University, Pediatric Cardiac Surgery, Doernbecher Children's Hospital, 3181 SW Sam Jackson Park Rd, DC8S, Portland, OR 97239-3098 (Email: ungerlei{at}ohsu.edu).

Presented at the Fortieth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 26–28, 2004.

BACKGROUND: Hypothermic circulatory arrest (HCA) impairs cerebral oxygen delivery (CDO₂) and cerebral oxygen consumption (CMRO₂), which are further reduced by perioperative hypoxemia. This study investigates if continuous hypothermic low-flow cardiopulmonary bypass (HLF) or intermittent hypothermic low-flow cardiopulmonary bypass (IHLF) can prevent reductions in CDO₂ and CMRO₂ during hypoxemia.

METHODS: Eighteen neonatal piglets, cooled to 16° to 18°C with cardiopulmonary bypass (CPB), were randomly assigned into three groups: HCA, HLF (50 cc · kg^–1 · min^–1), or IHLF (1 minute of HLF for every 15 minutes of HCA). After 60 minutes of hypothermia, normothermic CPB (100 cc · kg^–1 · min^–1) was established and cerebral perfusion data measured at hyperoxemia (PaO₂ 150 to 250 mm Hg), hypoxemia (PaO₂ 50 to 60 mm Hg), and severe hypoxemia (PaO₂ 30 to 40 mm Hg), and with increased CPB flow (200 cc · kg^–1 · min^–1) during severe hypoxemia.

RESULTS: The CMRO₂ (in mL O₂ · 100 g^–1 · min^–1) was lower after HCA (2.5 ± 0.3), compared with HLF (4.1 ± 0.5, p = 0.02) and IHLF (6.2 ± 0.8, p = 0.002). Within groups, the change from hyperoxemia to severe hypoxemia resulted in decreased CMRO₂: HCA (1.3 ± 0.2, p = 0.004), HLF (3.0 ± 0.5, p = 0.01), and IHLF (2.9 ± 0.5, p = 0.01). During severe hypoxemia, increasing CPB flow (from 100 cc · kg^–1 · min^–1 to 200 cc · kg^–1 · min^–1) improved CMRO₂: HCA (1.9 ± 0.5, p = 0.05), HLF (4.2 ± 0.5, p = 0.05), and IHLF (7.4 ± 0.5, p = 0.04).

CONCLUSIONS: Hypoxemia reduces CDO₂ and CMRO₂ despite the method of hypothermic CPB. Increased CPB flow during hypoxemia can restore both CDO₂ and CMRO₂ to values found with hyperoxemia and slower CPB flows. Augmenting cardiac output during periods of perioperative hypoxemia may prevent cerebral injury after exposure to hypothermic cardiopulmonary bypass.

Related Article

Hypothermic Low-Flow Cardiopulmonary Bypass Impairs Pulmonary and Right Ventricular Function More Than Circulatory Arrest

Jess M. Schultz, Tara Karamlou, Julia Swanson, Irving Shen, and Ross M. Ungerleider
Ann. Thorac. Surg. 2006 81: 474-480. [Abstract] [Full Text] [PDF]

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