29. Hemodynamic, Metabolic and Electron Microscopic Evidence Supporting the use of Intermittent Perfusion During Deep Hypothermic Circulatory Arrest (DHCA)
Stephen M. Langley, Paul J. Chai, Sara E. Miller, James R. Mault, James J. Jaggers, Steven S. Tsui, Andrew J. Lodge, Ann Lefurgey, Ross M. Ungerleider
Duke University Medical Center
Durham, N.C.
DHCA can be useful for repair of some heart defects in infant, but has been shown to cause an impairment in recovery of cerebral blood flow (CBF) and cerebral metabolism (CMRO2) may be a marker for brain injury, since CMRO2 recovers normally following cardiopulmonary bypass (CPB) when DHCA is not used. Our aims with this study were twofold. First, to investigate the effects of intermittent perfusion during DHCA in the anticipation that it would not result in significant impairment to CMRO2 following CPB and secondly, to correlate these findings with electron microscopy of the cerebral microcirculatory bed (EM).
Fifteen neonatal piglets were placed on CPB and cooled to 18°C. Each animal then underwent either 1) 60 minutes continuous CPB (control), 2) 60 minutes uninterrupted DHCA (UI-DHCA) or 3) 60 minutes DHCA with intermittent perfusion (one minute every 15 minutes) (I-DHCA). All animals were then re-warmed and weaned from CPB. Measurements of CBF and CMRO2 (radioactive Xe clearance) were taken before and after CPB. A further nine animals underwent CPB without DHCA (2 animals) or with DHCA (seven animals), under various conditions of arterial blood gas management, intermittent perfusion and reperfusion time.
UI-DHCA resulted in significant impairment to recovery of CMRO2 following CPB (p<0.05). Regardless of the blood gas strategy used, the EM following UI-DHCA revealed extensive damage characterized by perivascular intracellular and organelle edema and vascular collapse. I-DHCA, on the other hand, produced a pattern of normal CMRO2 recovery identical to controls and the EM was normal for both these groups.
Intermittent perfusion during DHCA is clinically practical and results in normal cerebral metabolic and ultrastructural recovery. Furthermore, the correlation between brain structure and CMRO2 suggests that monitoring CMRO2 in the operating room may be an outstanding way to manage brain protection during infant heart surgery.