title: Effect of calcium and preischemic hypothermia on recovery of myocardial function after cardioplegic ischemia in neonatal lambs.
abstract: Hypothermia has been reported to increase intracellular ionized calcium, which may aggravate injury resulting from ischemia and reperfusion. The effects of plasma ionized calcium concentration ([Ca2+]) during hypothermic perfusion on recovery after 2 hours of cold cardioplegic ischemia were evaluated in 32 isolated, blood-perfused neonatal lamb hearts. Three groups of hearts (B, C, and D) were perfusion-cooled for 10 minutes to a myocardial temperature of 17 degrees C and then arrested with St. Thomas' Hospital cardioplegic solution. Group A had 10 minutes of normothermic perfusion before cardioplegia. Group B had cooling with normal [Ca2+]. Group C had citrate added as cooling was started to lower [Ca2+] (0.26 mmol/L), and it was not normalized until 15 minutes into reperfusion. Group D received citrate plus Ca2+ to give normal [Ca2+] during cooling. Groups B and D showed a significantly reduced recovery (p < 0.05) in left ventricular systolic function (developed pressure and the rate of pressure rise) and diastolic function (stiffness constant) than groups A and C. During preischemic cooling, oxygen consumption per beat and coronary vascular resistance increased significantly in groups B and D, but both oxygen consumption and coronary vascular resistance were significantly lower in group C than in groups B and D so long as [Ca2+] was low. The data show that preischemic hypothermia results in reduced postischemic recovery of function compared with simultaneous induction of cardioplegia and hypothermia. Low [Ca2+] during preischemic hypothermia and early reperfusion offsets this deleterious effect of hypothermia.
authors.affiliation: Department of Cardiovascular Surgery, Harvard Medical School, Boston, Mass.
authors.forename: M
authors.initials: M
authors.lastname: Aoki
authors.forename: F
authors.initials: F
authors.lastname: Nomura
authors.forename: H
authors.initials: H
authors.lastname: Kawata
authors.forename: J E
authors.initials: JE
authors.lastname: Mayer
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000097:blood*; D006324:Heart Arrest, Induced / Q000379:methods*; D007036:Hypothermia, Induced; D017202:Myocardial Ischemia / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology; D012756:Sheep; D014655:Vascular Resistance / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology*
chemical_list: D002118:Calcium