الفهرس 
Introduction
congenital Heart defectsOnly 14 pages are availabe for public view
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Abstract
Despite major advances in the technical aspects of surgical repair of congenital heart diseases, perioperative myocardial damage with low cardiac output remains the most common cause of morbidity and death after repair of congenital heart lesions. So, optimal myocardial protection is as important as an excellent technical repair in achieving the best long-term outcome with surgical correction. Cyanotic patients are particularly vulnerable to myocardial injury and should receive even greater attention than those without cyanosis.
A variety of myocardial protection techniques exists and despite this variation, cardioplegia remains the most significant tool used to increase myocardial protection. Hypothermic depolarizing hyperkalemic (K+ > 20 mmol/L) cardioplegia is currently the “gold standard” in cardiac surgery. However, high potassium concentration has been associated with deleterious consequences against myocardial protection. A great number of studies have shown a link between exposure to high potassium and post-cardioplegia ionic and metabolic imbalances during ischemia, and myocardial stunning, arrhythmia, tissue edema, endothelial damage, free radical production, and functional loss during reperfusion.
The objective of this study is to compare the cardioprotective effects and safety of different potassium concentrations in two cold crystalloid potassium cardioplegia against conventional one, custodiol in pediatric patients undergoing open heart surgery for total correction of TOF.
Design: double blinded prospective randomized controlled trial
Setting: Assiut University Hospitals; Al-Orman cardiac surgery center
Patients and Methods: 60 pediatric patients with Tetralogy of Fallot and undergoing open heart surgery with cardiopulmonary bypass were randomly allocated into three equal groups according to the type of cardioplegic solution. group C received 30 ml/kg of Custodiol HTK solution over 6-8 minutes and repeated if the ischemic time continues more than 120 minutes. group S received small volume high potassium concentration (K+ 30 mmol/L) cardioplegia; 10 ml/kg for induction of arrest and repeated every 20 minutes at a dose of 5 ml/kg. group L received large volume low potassium concentration (K+ 10 mmol/L) cardioplegia; 30 ml/kg for induction of arrest and repeated every 20 minutes at a dose of 15 ml/kg.
Inclusion criteria are Tetralogy of Fallot patients aged one to twelve years with hemodynamic stability scheduled for total repair under CPB with expected cross-clamp time>45 minutes. Exclusion criteria include children with acyanotic congenital heart disease, previous cardiac surgery, urgent or emergent cases, and any cases have required cardioplegia infusion in less than 20 minutes due to electrical and or mechanical activity.
Measurements: We recorded demographic and surgical data, hemodynamic parameters, arterial blood gases, type and time of cardiac rhythm return after de-clamping, need for DC, initial and maximum inotropic score during first 24 hours postoperatively, duration of inotropic score, coronary sinus blood sample withdrawn just after aortic de-clamping analyzed for pH, PCO2, oxygen saturation, base deficit and potassium, blood samples were obtained for troponin I levels pre-CBP, 6, 12 and 24 hours after aortic cross-clamping, myocardial sample was obtained from the endocardial surface of the right ventricle and placed in formalin until examination under light microscopy for detection of myocyte cellular edema as a marker of ischemic changes. Also, total amount and frequency of cardioplegia was. Pre- and postoperative echocardiography was done for evaluation of cardiac function. duration of mechanical ventilation, ICU stay and hospital stay were recorded. We recorded also 30-day mortality rate.
Results: The results of this study showed better myocardial protection in group L (lower potassium concentration) as evidenced clinically by earlier return of cardiac rhythm after de-clamping [it was (32.05 3.61) seconds in group L compared to (40.66 4.64) seconds in group C and (41.75 2.57) seconds in group S; P0.001] with most of cases had sinus rhythm (85% of cases in group L compared to 70% in both group C and group S), lower doses of inotropes/vasopressors [Initial and maximum IS were lowest in group L ; both were 12 (6.50) compared to group S; 23 (5.50) and 23.5 (4.50) respectively and group C; 15 (16.75) and 18.5 (18.50) respectively, P0.001] , and shorter durations of mechanical ventilation [4 (1.25) hours in group L, 7 (15.25) hours in group C, and 6 (1.38) hours in group S, P=0.004], ICU stay [4 (1) days in group L, 6 (3) days in group C, and 7 (2.25) days in group S, P0.001] and hospital stay [5 (2) days in group L, 8 (2.25) days in group S, 8 (1.25) days in group C, P0.001] with better cost effectiveness. This also reflected on laboratory parameters of myocardial cell damage; less cardiac troponin I level especially after six hours from aortic cross-clamping [cTnI was 30.35 ng/ml in group L compared to 32 ng/ml in group C and 58.95 ng/ml in group S, P0.001], less coronary sinus lactate[4.45 mmol/L in both group L and S compared to 6.6 mmol/L in group C, P0.001] and coronary sinus PCO2 [55 (19.25) mmHg in group L, 70.5 (26.50) mmHg in group S, and 79.22 (31.50) mmHg in group C, P=0.001]. Although this less myocardial injury and more myocardial protection in group L, this was not reflected on changes on hemodynamic parameters or histopathological examination (myocardial edema).
Conclusion: from the findings of the present study we conclude that low potassium cardioplegia may have better myocardial protection effects in pediatric cardiac surgery with better clinical outcomes. It is also simple and cost-effective formulation compared to more complex formulations with multiple additives.
Recommendations: A larger size and multicenter clinical trial is warranted to determine the myocardial protective effects of this low potassium cardioplegia formula in the future. Also, more studies are recommended to determine the optimal dose of potassium in the cardioplegic solutions and or newer additives with more better myocardial protective effects.
Declaration of interest: None declared.
Funding: Equipment used in this study was provided by Assiut University Hospitals, Assiut, Egypt. We received no additional funding.