title: Tolerance of the developing heart to ischemia: impact of hypoxemia from birth.
abstract: Many infants who require cardiac surgery have cyanotic heart disease. We assessed the relative tolerances to ischemia of hearts from immature normoxemic rabbits versus hearts from immature rabbits subjected to hypoxemia since birth. Normoxemic animals were raised from birth in an environment where the inspired fractional concentration of oxygen (FIO2) was 0.21; for the hypoxemic studies FIO2 was reduced to 0.09. Hearts (n = 6/group) from normoxemic and chronically hypoxemic rabbits at 7-12, 21-28, 35-44, and 51-56 days of age underwent aerobic "working" perfusion with Krebs bicarbonate buffer, and cardiac function was measured. Hearts were then arrested by a 3-min infusion with either cold (14 degrees C) Krebs buffer (hypothermia alone group) or St. Thomas' Hospital II solution (hypothermia plus cardioplegia group) before 6 h of hypothermic (14 degrees C) global ischemia. Hearts were reperfused, and postischemic creatine kinase leakage and recovery of function were measured. For hearts protected with hypothermia alone, recovery of aortic flow was better in hearts hypoxemic from birth compared with normoxemic controls at 7-12 days (78 +/- 7 vs. 60 +/- 6%, P < 0.05) and 21-28 days old (81 +/- 12 vs. 26 +/- 28%, P < 0.05). Protection with hypothermia plus cardioplegia was also better in hearts hypoxemic from birth compared with normoxemic controls at 7-12 days (74 +/- 8 vs. 63 +/- 10%, P < 0.05) and 21-28 days old (84 +/- 3 vs. 71 +/- 5%, P < 0.05). Protection with hypothermia alone and hypothermia plus cardioplegia was no different within chronically hypoxemic age groups.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Cardiothoracic Surgery, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: E J
authors.initials: EJ
authors.lastname: Baker
authors.forename: L E
authors.initials: LE
authors.lastname: Boerboom
authors.forename: G N
authors.initials: GN
authors.lastname: Olinger
authors.forename: J E
authors.initials: JE
authors.lastname: Baker
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001639:Bicarbonates; D002122:Calcium Chloride; D002314:Cardioplegic Solutions; D003402:Creatine Kinase / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D006321:Heart / Q000254:growth & development; D007036:Hypothermia, Induced; D000860:Hypoxia / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D066298:In Vitro Techniques; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008274:Magnesium; D017202:Myocardial Ischemia / Q000209:etiology* / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000209:etiology / Q000517:prevention & control; D010477:Perfusion; D011189:Potassium Chloride; D011247:Pregnancy; D011817:Rabbits; D012965:Sodium Chloride
chemical_list: D001639:Bicarbonates; D002314:Cardioplegic Solutions; D007527:Isoenzymes; C041711:St. Thomas' Hospital cardioplegic solution; D012965:Sodium Chloride; D011189:Potassium Chloride; D007770:L-Lactate Dehydrogenase; D003402:Creatine Kinase; D008274:Magnesium; D002122:Calcium Chloride