INCREASING THE COLLOID OSMOTIC-PRESSURE OF CARDIOPULMONARY BYPASS PRIME AND NORMOTHERMIC BLOOD CARDIOPLEGIA MINIMIZES MYOCARDIAL EDEMA AND PREVENTS CARDIAC DYSFUNCTION

Our recent work demonstrated that normothermic continuous antegrade bl ood cardioplegia results in cardiac dysfunction related to myocardial oedema, This oedema was partially due to increased myocardial microvas cular fluid filtration induced by crystalloid hemodilution. We hypothe sized that increasing the colloid osmotic pressure of blood cardiopleg ia would stop fluid filtration into the cardiac interstitium, thus pre venting myocardial oedema and cardiac dysfunction. Methods: We determi ned myocardial water content in six dogs by microgravimetry and myocar dial lymph flow from the major prenodal cardiac lymphatic. Preload rec ruitable stroke work was derived from sonomicrometry and micromanometr y, The dogs were subjected to normothermic cardiopulmonary bypass prim ed with 6% hetastarch and 1 h of normothermic continuous antegrade blo od cardioplegia (4:1 blood:6% hetastarch colloid osmotic pressure 21 /- 2 mmHg) delivered at 50 mmHg perfusion pressure. Results: We found that despite increased colloid osmotic pressure, a small but significa nt increase in myocardial water content still occurred during blood ca rdioplegia, As myocardial lymph flow virtually ceased during cardiople gia, myocardial microvascular filtration must have been present. Howev er, increased myocardial lymph flow following cardioplegia resulted in complete oedema resolution associated with normal left ventricular pe rformance post-cardiopulmonary bypass. Conclusions: Our data show that the plegic myocardium is prone to oedema formation because of both re latively enhanced fluid filtration and lymph flow cessation. We conclu de that increasing the colloid osmotic pressure of normothermic blood cardioplegia minimizes myocardial oedema, thus preventing post-cardiop ulmonary bypass cardiac dysfunction. (C) 1998 The International Societ y for Cardiovascular Surgery. Published by Elsevier Science Ltd. All r ights reserved.