***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Ischemia-reperfusion injury during open heart surgery related to unsuccessful myocardial protection may increase morbidity or mortality . We analyze the clinical outcome after cardiac surgery with a cardioplegic solution based on intracellular components added with histidine-ketoglutarate-tryptophan . METHODS Thirty patients programmed for elective open heart surgery were r and omized into two groups . In group I ( n = 15 ) , myocardial protection was carried out with Bretschenider solution ( HTK ) , and in group II ( n = 15 ) with conventional crystalloid cardioplegia . The incidence of arrhythmias , inotropic support requirement , and length-of-stay in the intensive care unit were evaluated . RESULTS During reperfusion , there was no difference in incidence of arrhythmias ; however , in the postoperative period group I had a lower incidence of arrhythmias ( p = 0.001 ) . Inotropic support ( p = 0.003 ) and length-of-stay in the intensive care unit ( p = 0.037 ) were lower in group I. There were no deaths in either group . CONCLUSIONS It was concluded that myocardial protection with Bretschneider solution effectively decreases incidence of arrhythmias , inotropic support , and length-of-stay in the intensive care unit BACKGROUND We hypothesized that blood cardioplegia preserves myocardial metabolism and function more effectively than St Thomas ' crystalloid cardioplegia in infant cardiac surgery . METHODS Thirty infants with atrioventricular septal defects were r and omly allocated to either blood or crystalloid intermittent cold ( 4 degrees C ) cardioplegia . Arterial and coronary sinus blood was analyzed for lactate and oxygen . Cardiac output ( thermodilution ) and left ventricular function ( echocardiography ) were evaluated . RESULTS The lactate concentration in coronary sinus blood early after bypass was significantly higher after crystalloid cardioplegia than after blood cardioplegia ( 2.1 + /- 0.3 vs 1.3 + /- 0.1 mmol/L , p = 0.006 ) , with a significant myocardial release of lactate after crystalloid but not after blood cardioplegia . Oxygen extraction ( arterial-coronary sinus O2 content ) was higher early after crystalloid cardioplegia ( 3.02 + /- 0.13 vs 2.35 + /- 0.22 mmol/L , p = 0.01 ) , possibly reflecting a difference in oxygen debt . The cardiac index was higher after blood cardioplegia ( 4.9 + /- 0.3 vs 4.0 + /- 0.3 L/min(-1)/m(-2 ) , p = 0.04 ) and echocardiographic grading of left ventricular function was better ( 4.1 + /- 0.17 vs 3.5 + /- 0.22 arbitrary units , p = 0.046 ) . CONCLUSIONS This study indicates that blood cardioplegia preserves myocardial metabolism and function more effectively than crystalloid cardioplegia in infant cardiac surgery . The clinical significance of this finding is uncertain , but the more than 20 % increase in cardiac index in the critical phase during weaning from bypass may be advantageous OBJECTIVES A single or dual-dose strategy for myocardial protection is attractive in long operations , in avoiding the need to interrupt the procedure to re-administer cardioplegia . We hypothesized that a single administration of Bretschneider histidine-tryptophan-ketoglutarate ( HTK ) crystalloid solution ( Custodiol ) offers myocardial protection comparable with repeated tepid blood cardioplegia . METHODS We review ed a prospect ively compiled single-centre data base containing all adult cardiac procedures performed from January 2005 to January 2011 . Preoperative demographic and investigative data , operative variables and postoperative ( 30-day ) mortality and morbidity were compared between the Custodiol and blood cardioplegia groups . The study primary endpoints were 30-day mortality , return to the operating theatre , myocardial infa rct ion , stroke , postoperative requirement for an intra-aortic balloon pump , new renal failure , prolonged ventilation and re-admission to hospital within 30 days . Propensity score matching was performed to correct for any bias that may have been associated with the usage of Custodiol . RESULTS A total of 1900 cardiac surgical procedures were identified of which 126 ( 7 % ) utilized Custodiol and 1774 ( 93 % ) used blood cardioplegia as the primary cardioplegic agent . After propensity-score matching , we were able to match 71 Custodiol cases one-to-one to those receiving blood cardioplegia . There were no statistically significant differences noted for any of the endpoints studied after propensity-score matching . In particular , the proportion of mortality ( blood cardioplegia : 1 vs Custodiol 4 % , P = 0.63 ) any mortality/morbidity ( blood cardioplegia : 35 vs Custodiol : 39 % P = 0.46 ) was similar between the groups . CONCLUSIONS The use of Custodiol is convenient , simple and at least as safe as tepid blood cardioplegia for myocardial protection in complex cardiac operations . A r and omized prospect i ve comparison of myocardial protection strategies is warranted Background —The advantages of blood cardioplegia include the oxygen-carrying capacity , superior oncotic and buffering properties , and endogenous antioxidants contained in blood . However , the partial dilution of blood in 4:1 ( blood : crystalloid ) cardioplegic solutions may nullify these advantages and progressively dilute blood during continuous retro grade delivery . This study tested the hypothesis that all-blood ( 66:1 ) cardioplegia provides superior myocardial protection compared with dilute ( 4:1 ) cardioplegia delivered in a continuous retro grade modality during surgical reperfusion of evolving myocardial infa rct ion . Methods and Results —After 60 minutes of left anterior descending coronary artery ( LAD ) occlusion , anesthetized canines were placed on cardiopulmonary bypass and r and omized to either all-blood cardioplegia ( AB group ) or dilute blood cardioplegia ( Dil group ) . After cross clamping , arrest was induced with 5 minutes of tepid ( 30 ° C ) ante grade potassium all-blood or dilute blood cardioplegia and maintained with tepid retro grade coronary sinus cardioplegia for a total of 1 hour . The LAD was released after 30 minutes of arrest , simulating revascularization . The cardioplegia hematocrit for the Dil group was lower than that for the AB group ( 7±1 % versus 12±2 % , P < 0.05 ) ; at the end of bypass , systemic hematocrit was lower in the Dil group than in the Ab group ( 15±1 % versus 20±1 % , P < 0.05 ) . Infa rct size ( triphenyltetrazolium chloride staining ) was comparable between the AB and Dil groups ( 29.6±2.9 % versus 30.3±3.9 % of area at risk ) , and there was no difference in area-at-risk myocardium systolic shortening ( by sonomicrometry , −0.3±1 % versus −0.4±1 % ) . Tissue edema after bypass tended to be greater in the Dil group compared with the AB group in the heart ( 82±0 % versus 81±1 % ) , lung ( 79±1 % versus 78±1 % ) , liver ( 75±1 % versus 74±0 % ) , and skeletal muscle ( 76±1 % versus 73±2 % ) and was significantly greater in the duodenum ( 80±1 % versus 79±1 % , P < 0.05 ) and kidney ( 82±1 % versus 79±1 % , P < 0.05 ) . Postexperimental endothelial function ( relaxation of acetylcholine ) was impaired in LADs of the AB group versus the Dil group ( 59±6 % versus 77±5 % , P < 0.05 ) . Conclusions —Both all-blood cardioplegia and dilute cardioplegia have disadvantages , but these do not have an impact on the pathogenesis of infa rct size or recovery of regional contractile function While blood : crystalloid cardioplegia is the clinical st and ard for patients undergoing cardiopulmonary bypass ( CPB ) , it has been postulated that whole blood minicardioplegia may benefit the severely injured heart by reducing cardioplegic volume , thereby reducing myocardial edema . To test this hypothesis , we compared the cardioprotection of a popular 4:1 blood : crystalloid cardioplegia to whole blood minicardioplegia ( WB ) in a porcine model of acute myocardial ischemia . Yorkshire pigs ( n = 20 ) were placed on atriofemoral bypass and subjected to 30 minutes of global normothermic ischemia . Animals were r and omized to receive either 4:1 cold cardioplegia ( n = 10 ) or WB cold cardioplegia ( n = 10 ) delivered ante grade continuously for 90 minutes . Baseline ( BL ) echocardiographic determination of left ventricular mass ( LVM ) was compared within groups for cardiac edema ( % ) measured by histologic morphometrics . All ( 100 % ) animals receiving WB were successfully weaned off CPB , whereas only 40 % of animals receiving 4:1 were successfully weaned off CPB . Cardiac edema percentage ( p < .004 ) and LVM ( p < .05 ) were significantly decreased in the WB group compared with 4:1 . WB cardioplegia increases the number of hearts successfully weaned from CPB and decreases cardiac edema in our porcine model of acute myocardial ischemia . This finding implies whole blood cardioplegia may be more protective in a select group of patients undergoing extended CPB time by decreasing myocardial edema BACKGROUND Blood cardioplegia has been widely accepted in clinical cardiac surgery based on its excellent oxygen delivery and pH buffering capacity . To further conserve blood during clinical cardiac surgery , we formulated a new crystalloid cardioplegic solution containing histidine ( 100 mol/L ) as the pH buffering agent . METHODS Sixty patients being applied Histidine Buffered Solution ( HBS ) ( n = 27 ) or Cold Blood Cardioplegic solution ( CBC ) ( n = 33 ) , both at 4 degrees C , were studied prospect ively . Pre- and post-bypass left-ventricular ( LV ) volume was measured by echocardiography . With a ventricular pressure catheter , LV pressure-volume loops were constructed to determine the slope of the end-systolic pressure-volume relationship ( Emax ) without inotropes . RESULTS There were no postoperative deaths in either group . Thirty minutes after reperfusion Emax was significantly better in the HBS group than in the CBC group ( 6.0 + /- 1.0 mmHg/cm3 vs 3.7 + /- 0.8 mmHg/cm3 ) . Cardiac Index was also significantly higher in HBS group than in CBC group with lower inotropic requirement . Homologous blood transfusion was avoided in 64 % of the patients receiving HBS versus 48 % of the patients with CBC . CONCLUSIONS We conclude that the new histidine-buffered cardioplegic solution provides effective protection with excellent recovery of pump performance in clinical open heart surgery OBJECTIVE Although experimental studies have indicated that blood cardioplegia may be superior to crystalloid cardioplegia for myocardial protection , clinical data still remain uncertain . In a previous r and omised study from our institution , including 1440 patients undergoing coronary artery bypass grafting ( CABG ) , no beneficial effects of blood cardioplegia were seen in any relevant outcome variables . The investigation was therefore extended to a patient population having longer pump times and ischaemic periods . METHODS Over a 48-month period , all patients undergoing aortic valve replacement with or without CABG performed by two surgeons , were prospect ively r and omised to receive either intermittent cold retro grade blood cardioplegia ( group B ) or intermittent cold retro grade crystalloid cardioplegia ( group C ) during aortic cross-clamping . RESULTS A total of 345 patients aged 28 - 90 years ( median , 72 years ) entered the study ( group B , n=172 , group C , n=173 ) . All relevant demographic and operative variables were similar for both groups . As for the clinical course , no statistically significant differences were seen concerning spontaneous sinus rhythm after aortic declamping , use of inotropic drugs , duration of ventilatory support , bleeding and rate of allogeneic blood transfusions , perioperative myocardial infa rct ion , episodes of atrial fibrillation , stroke or minor neurological dysfunction , renal function , infections , physical rehabilitation or mortality . Further , in the patients with the longest ischaemic times , no statistically significant differences between the groups could be demonstrated . CONCLUSIONS There were no indications that retro grade cold blood cardioplegia was superior to retro grade cold crystalloid cardioplegia patients undergoing aortic valve replacement , with or without CABG OBJECTIVES Histidine-tryptophan-ketoglutarate ( HTK-Custodiol ) cardioplegic solution is administered as one single dose for more than 2 
    Output:
    
Some solutions , del Nido cardioplegia in particular , were found to have few or no significant human trials to back the rigor required in such a highly specialized field as cardiovascular surgery .
Without this research , surgeon preference remains the primary determining factor for deciding which cardioplegic solution to use .