Comparison of low-flow cardiopulmonary bypass and circulatory arrest on brain oxygen and metabolism.
BACKGROUND
In the neonatal brain we measured oxygen (Bo(2)), extracellular striatal dopamine (DA), and striatal tissue levels of ortho-tyrosine (o-tyr) during low-flow cardiopulmonary bypass (LFCPB) or deep hypothermic circulatory arrest (DHCA) and the post-bypass recovery period.


METHODS
Newborn piglets were assigned to sham (n = 6), LFCPB (n = 8), or DHCA (n = 6) groups. Animals were cooled to 18 degrees C and underwent DHCA or LFCPB (20 mL x kg(-1) x min(-1)) for 90 minutes. The Bo(2) was measured by quenching the phosphorescence, DA by microdialysis, and hydroxyl radicals by o-tyr levels. The results are presented as the mean +/- SD (p < 0.05 was significant).


RESULTS
Baseline Bo(2) was between 45 to 60 mm Hg. At the end of LFCPB, Bo(2) was 10.5 +/- 1.2 mm Hg. By 5 and 30 minutes of arrest during DHCA, Bo(2) fell to 4.2 +/- 2.5 mm Hg and 1.4 +/- 0.7 mm Hg, respectively. Compared with control, extracellular DA did not change during LFCPB. During DHCA extracellular levels of DA increased, by 750-fold from baseline at 45 minutes and to a maximum of 53000-fold at 75 minutes. After 2 hours of recovery from DHCA, the o-tyr within the striatum increased about sixfold as compared with control. There was no change in o-tyr measured after LFCPB.


CONCLUSIONS
In DHCA, but not LFCPB, levels of DA and o-tyr increased considerably in the striatum of piglets, a finding that may indicate the exhaustion of cellular energy levels and contribute substantially to cellular injury.
Schultz
Steven
S
Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Creed
Jennifer
J
Schears
Gregory
G
Zaitseva
Tatiana
T
Greeley
William
W
Wilson
David F
DF
Pastuszko
Anna
A
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D002315:Cardiopulmonary Bypass / Q000379:methods*; D003342:Corpus Striatum / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D005110:Extracellular Space / Q000737:chemistry; D006324:Heart Arrest, Induced; D017665:Hydroxyl Radical / Q000378:metabolism; D007036:Hypothermia, Induced; D017551:Microdialysis; D010100:Oxygen / Q000378:metabolism*; D013552:Swine; D014443:Tyrosine / Q000378:metabolism
D017665:Hydroxyl Radical; D014443:Tyrosine; C026741:2-tyrosine; D010100:Oxygen; D004298:Dopamine