Effect of mannitol on the performance of the isolated canine heart after fibrillatory arrest

Optimal osmolality for cold storage of the cardiac explant

Cell swelling is a major problem of cardiac preservation. This study evaluated the effect of storage solution osmolality on long-term preservation of cardiac function. Isolated rat hearts were flushed and stored in solutions of 260 to 350 mOsm/kg water at 0 degrees C for 9 hr. Cardiac performance was assessed using the isolated working heart reperfusion. Function of fresh unstored hearts served as the control. The stored hearts had normal heart rate after reperfusion. Other hemodynamic functions recovered to various levels of the control value and showed biphasic responses to solution osmolality. Hearts stored in hyposmotic (260 and 270 mOsm) and hyperosmotic (310, 330, and 350 mOsm) solutions performed poorly. Those stored in 280 to 290 mOsm solutions showed superior recovery in cardiac function. Among all parameters, coronary flow correlated linearly with aortic flow, cardiac output, systolic pressure, work, oxygen consumption, and coronary vascular resistance. Solutions of 280, 290, and 310 mOsm caused 6 to 9% increases in tissue water (TW) over the control hearts during 9 hr storage, whereas 350 mOsm solution maintained TW at the control level. After reperfusion, all stored hearts gained water (25 to 38%) compared to hearts with no reperfusion. Postreperfusion myocardial ATP content was only 70-79% of control level and did not correlate to function recovery. In conclusion, (1) the optimal osmolality of our preservation fluid is 280 to 290 mOsm and moderate or severe hyperosmolality is detrimental to cardiac function, and (2) preservation of coronary function may be crucial to future improvement of storage solution.

The effect of adding mannitol or albumin to a crystalloid cardioplegic solution: a prospective, randomized clinical study

To determine if the myocardial protection afforded by a cold crystalloid potassium cardioplegic solution could be improved by the addition of either mannitol or albumin, a prospective clinical study was undertaken in which 58 patients undergoing elective aortocoronary bypass were randomized to one of three groups. Each group featured a different cardioplegic solution. The solutions were a standard potassium crystalloid solution, a solution containing mannitol sufficient to raise the osmolality by 20 to 30 mOsm, and a solution containing 5% albumin. Preoperative, intraoperative, and postoperative evaluation included serial measurements of ejection fraction, myocardial-specific isoenzyme, and hemodynamic indexes of performance. Electrocardiographic evaluation for perioperative myocardial infarction and the need for postoperative inotropic and mechanical support were also included. No differences were found among the groups. Therefore, although the use of mannitol or albumin has been shown to be beneficial in an experimental setting, superiority of either additive could not be demonstrated clinically.

Effect of albumin and mannitol on organ blood flow, oxygen delivery, water content, and renal function during hypothermic hemodilution cardiopulmonary bypass

The present study was designed to determine if the addition of albumin or mannitol to the priming solution of the pump oxygenator would diminish edema in organs, without diminishing some of the beneficial effects of hemodilution on blood flow and renal function. Tissue blood flow (15 mu spheres), water content, and renal clearances were determined in 8 animals during cardiopulmonary bypass. A 2(2) factorial, completely fixed experimental design was used. All animals were placed on cardiopulmonary bypass with hemodilution (hematocrit 25 +/- 2%) and hypothermia (25 degrees +/- 1 degree C). Albumin decreased flow to the midmyocardium of the left ventricle and to the spleen, and increased flow to the inner cortex of the kidney. Albumin caused decreased urine flow and decreased urine sodium, and also diminished renal osmolar, sodium, and free-water clearances. both mannitol and albumin decreased lung water. Mannitol decreased water content of the outer renal cortex, and decreased flow to the inner cortex and medulla of the kidney and to the spleen. Mannitol had no significant effect on urine flow, renal plasma flow, or renal clearances. Neither albumin nor mannitol had any effect on water content of the intestine, stomach, liver, or myocardium where the greatest accumulation of water occurs with hemodilution. The effect of albumin on renal function is potentially deleterious during cardiopulmonary bypass because it decreases urine flow, and osmolar and free-water clearance.

An isolated, blood-perfused, feline heart preparation for evaluating pharmacological interventions during myocardial ischemia

A preparation is described in which feline hearts were perfused with arterial blood drawn from a blood-donor cat. Ventricular function was measured with a fluid-filled latex balloon within the left ventricle. Left ventricular developed pressure, maximum left ventricular dP/dt, ventricular compliance, and coronary blood flow changed only slightly during two hours of perfusion at a constant pressure of 75 mmHg. Water, sodium, potassium, and calcium contents, and creatine kinase activity of isolated hearts did not differ from the values obtained for intact hearts from the blood-donor cats. Isolated hearts subjected to 40 minutes of normothermic global ischemia with one hour of reperfusion exhibited significantly decreased contractility, but no change in ventricular compliance. Myocardial water and sodium contents were increased after 40 minutes of ischemia and reperfusion. Hearts subjected to 60 minutes of ischemia with reperfusion exhibited decreases in both contractility and compliance. A prolonged reactive hyperemic response was maintained throughout the hour of reperfusion. Myocardial sodium content increased more than could be accounted for by edema formation; decreases were observed in potassium content and creatine kinase activity while calcium content was increased. The applicability of this model for evaluating the effects of pharmacological interventions on myocardial ischemic injury are discussed.

Effect of potassium cardioplegia on myocardial ischemia and post arrest ventricular function

To assess the effects of moderate potassium cardioplegia (37 mEq/l KCl) on the severity of myocardial ischemia during arrest and on post arrest ventricular function, 32 isolated, isovolumic feline hearts were studied before, during and 1 hour after ischemic arrest. Normothermia (37 degrees C) was maintained in the remaining 16 hearts, eight without KCl and eight with KCl. Hypothermia (27 degrees C) was maintained in the remaining 16 hearts, eight with KCl and eight without KCl. Myocardial oxygen (PmO2) and carbon dioxide tensions (PmCO2) were measured by mass spectrometry. Maximum developed intraventricular pressure (max DP) and max dP/dt were used as indices of performance. Compared with normothermic or hypothermic arrest alone, the addition of potassium cardioplegia resulted in a significant reduction in the peak PmCO2 measured during the arrest period. Hypothermia alone resulted in morphologic evidence of improved myocardial preservation and a significant reduction in peak PmCO2 compared with normothermia. Post arrest ventricular function was best with the combination of hypothermic arrest and potassium cardioplegia (max DP = 96 +/- 6% of control and max dP/dt = 99 +/- 5% of control). These data suggest that the beneficial effects of postassium cardioplegia and 27 degrees hypothermia are additive, and that reduction in myocardial ischemia as evidenced by a reduction in peak PmCO2 correlated with improvement in ventricular performance in the post arrest period and with preservation of myocardial structure.

The effect of mannitol following permanent coronary occlusion

Quantitative comparisons of infarcts 24 hours after ligation of the left anterior descending coronary artery (LAD) via thoracotomy were made in 13 control and 13 dogs treated with i.v. 25% mannitol, 2 ml/min for 4 hours following occlusion. Mannitol increased serum osmolarity by 44+/-4 mOsm/L (mean +/- 1 SE) with hemodynamic effects limited to a small increase in left ventricular dP/dt. Nonperfusible tissue measured by planimetry at 24 hours was similar in both groups (46+/-4% of area defined with dye injected into the distal LAD for control versus 48+/-5% for mannitol treated dogs, P = NS). Creatine phosphokinase activity in infarcted tissues was also similar in both groups. Myocardial blood flows measured with radioactive microspheres were also similar in both groups. Collateral conductance calcultaed from retrograde flow and aortic pressure increased with the 24 hour period by 146+/-23% in the control dogs; in the mannitol treated dogs, collateral increased only 38+/-14% (P less than 0.001). Thus mannitol had no effect on ultimate infarct size. Moreover, mannitol appeared to hinder the development of collateral vessels.

Influence of mannitol on maintaining coronary flows and salvaging myocardium during ventriculotomy and during prolonged coronary artery ligation

We investigated whether prolonged infusion of hypertonic mannitol results in a sustained increase in coronary flow and reduces myocardial necrosis after ventriculotomy or two hours of circumflex coronary artery occlusion. Cardiac outputs, intracardiac pressures, and heart rates did not differ between mannitol and control animals. Those receiving mannitol after ventriculotomy had coronary flows to myocardium near the incision which did not differ from controls. During coronary occlusion, mannitol did increase flow to ischemic and peri-ischemic regions by one hour, but this increase was not sustained at two hours. On histologic examination, myocardial necrosis involving the right ventricular free wall in the ventriculotomy animals and the posterior papillary muscle and subadjacent free wall in the coronary occlusion animals, did not differ between the mannitol treated and control groups. The data obtained in the present study, combined with those from earlier evaluations of the influence of mannitol during ventriculotomy and myocardial ischemia, suggest that mannitol's ability to increase coronary flow to injured areas of myocardium is relatively short-lived.

Prevention of intraoperative myocardial injury by pretreatment with pharmacological agents

Pharmacological agents administered prior to the institution of myocardial anoxia or ischemia may protect the myocardium by preventing ATP depletion, structural damage to cell membranes and organelles, and postanoxic disturbances in coronary microcirculation. Propranolol, dipyridamole, nitroglycerin, and mannitol all have the potential to protect the myocardium in one or more of these ways and thus have promise for clinical use.