Blood cardioplegia: do we still need to dilute?

The comparison of del nido cardioplegia and crystalloid-based blood cardioplegia in adult isolated coronary bypass surgery: A randomized controlled trial

BACKGROUND AND AIM

In our study, patients who underwent isolated coronary artery bypass surgery (CABG) using Del Nido cardioplegia (DNC) and crystalloid-based cold blood cardioplegia (CBC) were compared.

SUBJECT AND METHODS

In this study, two groups of patients who underwent isolated CABG using DNC (n = 106) and CBC (n = 107) were prospectively randomized. Groups were compared in terms of many results such as troponin T, returning spontaneous rhythm, and cardioplegia volume.

RESULTS AND CONCLUSIONS

Median troponin T levels of the DNC and CBC groups were compared for the 0^th hour (baseline), 12^th, 36^th, and 60^th hours. There was no statistical difference between groups in troponin T levels of the baseline 0^th hour (18[33] vs. 22[27] pg/ml; P = 0.724). Troponin T levels at the 12^th hour were less in the DNC group than the CBC group but no statistical difference between the groups (790[735] vs. 826[820] pg/ml; P = 0.068), respectively. Troponin T levels at 36^th and 60^th hours were higher in the CBC group compared to the DNC group, and a statistical difference was observed (580[546] vs. 650[550] pg/ml; P = 0.030) and (359[395] vs. 421[400] pg/ml; P = 0.020), respectively. After X-clamping, the spontaneous rhythm rate was statistically higher in the DNC group than the CBC group (72.60% vs. 37.40%; P < 0.001). There was no statistical difference between the groups in terms of postoperative arrhythmia, hospital stay, and mortality rates (P > 0.05). Based on data we acquired from the study, we think that DNC is at least as safe and effective as CBC in adult CABG cases.

Theoretical and Practical Aspects in the Use of Bretschneider Cardioplegia

The race for an ideal cardioplegic solution has remained enthusiastic since the beginning of the modern cardiac surgery era. The Bretschneider solution, belonging to the “intracellular cardioplegic” group, is safe and practical in myocardial protection during ischemic time. Over time, some particular concerns have arisen regarding the effects on cardiac metabolism and postoperative myocardial functioning. This paper reviews the most important standpoints in terms of theoretical and practical analyses.

Intermittent antegrade warm-blood versus cold-blood cardioplegia in children undergoing open heart surgery: a protocol for a randomised controlled study (Thermic-3)

INTRODUCTION

Surgical repair of congenital heart defects often requires the use of cardiopulmonary bypass (CPB) and cardioplegic arrest. Cardioplegia is used during cardiac surgery requiring CPB to keep the heart still and to reduce myocardial damage as a result of ischaemia-reperfusion injury. Cold cardioplegia is the prevalent method of myocardial protection in paediatric patients; however, warm cardioplegia is used as part of usual care throughout the UK in adults. We aim to provide evidence to support the use of warm versus cold blood cardioplegia on clinical and biochemical outcomes during and after paediatric congenital heart surgery.

METHODS AND ANALYSIS

We are conducting a single-centre randomised controlled trial in paediatric patients undergoing operations requiring CPB and cardioplegic arrest at the Bristol Royal Hospital for Children. We will randomise participants in a 1:1 ratio to receive either 'cold-blood cardioplegia' or 'warm-blood cardioplegia'. The primary outcome will be the difference between groups with respect to Troponin T levels over the first 48 postoperative hours. Secondary outcomes will include measures of cardiac function; renal function; cerebral function; arrythmias during and postoperative hours; postoperative blood loss in the first 12 hours; vasoactive-inotrope score in the first 48 hours; intubation time; chest and wound infections; time from return from theatre until fit for discharge; length of postoperative hospital stay; all-cause mortality to 3 months postoperative; myocardial injury at the molecular and cellular level.

ETHICS AND DISSEMINATION

This trial has been approved by the London - Central Research Ethics Committee. Findings will be disseminated to the academic community through peer-reviewed publications and presentation at national and international meetings. Patients will be informed of the results through patient organisations and newsletters to participants.

TRIAL REGISTRATION NUMBER

ISRCTN13467772; Pre-results.

Strategies for blood conservation in pediatric cardiac surgery

Cardiac surgery accounts for the majority of blood transfusions in a hospital. Blood transfusion has been associated with complications and major adverse events after cardiac surgery. Compared to adults it is more difficult to avoid blood transfusion in children after cardiac surgery. This article takes into account the challenges and emphasizes on the various strategies that could be implemented, to conserve blood during pediatric cardiac surgery.

Is microplegia really superior to standard blood cardioplegia? The results from a meta-analysis

Background:

Microplegia (whole blood cardioplegia with reduced volume) retains all the advantages of blood cardioplegia (such as superior oxygen-carrying capacity, better osmotic properties and antioxidant capability, etc.) without the potential disadvantages of hemodilution (such as myocardial edema). We sought to perform a systematic review and meta-analysis to compare microplegia and standard blood cardioplegia on the cardioprotective effects for patients undergoing coronary artery bypass grafting (CABG).

Methods:

MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were searched for relevant controlled trials published in English, from their inception up to May 15th, 2013. Data on low output syndrome, spontaneous return to sinus rhythm, volume of cardioplegia and perioperative myocardial infarction were analyzed.

Results:

Five studies, totaling 296 patients, were included out of 77 retrieved citations. The microplegia group used less volume of cardioplegia (WMD, -514.79 ml, 95%CI: -705.37 ml to -324.21 ml) when compared with the standard blood cardioplegia group. There were no statistical differences in the incidence of low output syndrome (RR, 0.95, 95%CI: 0.55 to 1.62), spontaneous return to sinus rhythm (RR, 1.64, 95%CI: 0.61 to 4.41) and perioperative myocardial infarction (RR, 0.62, 95%CI: 0.19 to 2.08).

Conclusions:

Microplegia was associated with less volume of cardioplegia, whereas the incidence of spontaneous return to sinus rhythm and perioperative myocardial infarction were similar, but large controlled randomized trials are still needed to confirm this.

Predictors of low cardiac output syndrome after isolated coronary artery bypass surgery: trends over 20 years

BACKGROUND

Postoperative low cardiac output syndrome (LCOS) is associated with high morbidity and mortality after coronary artery bypass grafting (CABG). We sought to examine trends in predictors of LCOS after isolated CABG.

METHODS

A total of 25,176 consecutive patients who underwent isolated CABG between 1990 and 2009 were included. To examine trends over time, we divided patients into four equivalent eras (1990 to -1994, n = 6,489; 1995 to 1999, n = 8,175; 2000 to 2004, n = 6,741; 2005 to 2009, n = 3,797). We used multivariable analysis to identify predictors of LCOS.

RESULTS

The prevalence of LCOS declined from 9.1% (1990 to 1994) to 2.4% (2005 to 2009, p < 0.001). The following were the major independent predictors of LCOS for the entire cohort (odds ratios in parentheses): reoperative CABG (4.1); earlier year of operation (4.1, 2.6, 1.7 for the first, second, and third eras, respectively); left ventricular ejection fraction (LVEF) less than 0.20 (3.5), emergency surgery (2.7), cardiogenic shock (2.3), female gender (2), and LVEF 0.20 to 0.39 (2). Unlike other risk factors, the impact of LVEF less than 0.20 on development of postoperative LCOS increased substantially in the latest era (odds ratio, 7.8) compared with (odds ratios, 3.1, 4.3, and 3.2) the first, second, and third eras, respectively.

CONCLUSIONS

The impact of LVEF less than 0.20 on development of postoperative LCOS has increased markedly in the latest era of our study. Prudent preoperative evaluation in patients with severe left ventricular dysfunction is critical. Further innovative research in myocardial protection and circulatory support is warranted in patients with severe left ventricular dysfunction.

Warm pediatric cardiac surgery: European experience

Cold pediatric cardiac surgery has been a dogma for 50 years. However, the beneficial effects of cold perfusion are counterbalanced by the drawbacks of hypothermia. Thus, we propose a major paradigm shift from hypothermic surgery to warm perfusion and intermittent warm blood cardioplegia. This approach gives satisfactory results even with prolonged aortic crossclamp times. The major advantages are reduced time to extubation and shorter intensive care unit stay. Warm pediatric surgery is an anecdotal phenomenon no more; over 10,000 procedures have been carried out in Europe. All types of cardiopathy have been treated, including arterial switch, total pulmonary anomalous venous return, interruption of the aortic arch, and hypoplastic left heart syndrome. Once surgeons decide to shift from hypothermia to normothermia, they never decide to shift back to hypothermia. This fact is evidence of the satisfactory clinical outcome obtained with this technique. The technique and the composition of microplegia is identical in all European centers, the only variable factor being the interval between microplegia injections, which varies from 10 to 25 min. We hope that the increasing interest in pediatric warm surgery will hearten new candidates.

Perfusionist strategies for blood conservation in pediatric cardiac surgery

There is increasing concern about the safety of homologous blood transfusion during cardiac surgery, and a restrictive transfusion practice is associated with improved outcome. Transfusion-free pediatric cardiac surgery is unrealistic for the vast majority of procedures in neonates or small infants; however, considerable progress has been made by using techniques that decrease the need for homologous blood products or even allow bloodless surgery in older infants and children. These techniques involve a decrease in prime volume by downsizing the bypass circuit with the help of vacuum-assisted venous drainage, microplegia, autologous blood predonation with or without infusion of recombinant (erythropoietin), cell salvaging, ultrafiltration and retrograde autologous priming. The three major techniques which are simple, safe, efficient, and cost-effective are: a prime volume as small as possible, cardioplegia with negligible hydric balance and circuit residual blood salvaged without any alteration. Furthermore, these three techniques can be used for all the patients, including emergencies and small babies. In every pediatric surgical unit, a strategy to decrease or avoid blood bank transfusion must be implemented. A strategy to minimize transfusion requirement requires a combined effort involving the entire surgical team with pre-, peri-, and postoperative planning and management.

Use of (all-blood) miniplegia versus crystalloid cardioplegia in an experimental model of acute myocardial ischemia

PURPOSE

Several methods of myocardial protection have been used. The use of all-blood solutions modified with glutamate and aspartate has increased. Its use in situations of acute ischemia provides improved contractile function, "resuscitating" the previously lesioned muscle. The dilution preconized by literature is around 25% of the hematocrit. The present study evaluates an all-blood cardioplegia solution with tepid 1% dilution, denominated miniplegia.

MATERIAL AND METHOD

Pigs of the Large-White breed were used with an isolated heart and perfused with blood of a support animal. Three groups (n = 7 per group) were designated with the following treatments: Control group (CO), St. Thomas solution (ST), continuous normothermic all-blood solutions (SG). After the stabilization period, systolic pressure (PS), diastolic pressure (PD), developed pressure (PD), stress of the wall, elastance, and passive stiffness were recorded. The hearts were submitted to 30 minutes of regional ischemia with the clamping of the anterior interventricular artery, and subsequently to 90 minutes of global ischemia with the use of the three different treatments during this period. At the beginning of global ischemia, the coronary clamp was removed. The hearts were again reperfused. Upon three minutes into reperfusion the hearts were defibrillated when necessary. Measurements were taken every 30 minutes to 90 minutes into reperfusion.

RESULTS

The SG presented a better recovery of the ventricular function in several of the parameters recorded. The ST group was inferior to the SG group, which in turn was superior to the CO group in some of the parameters analyzed. A higher number of defibrillations were needed to reestablish coordinated heart beats in the ST and CO groups. There were no differences related to the percentage of wet weight between the SG and ST groups, and the percentage was higher in the CO group.

CONCLUSION

The use of all-blood miniplegia provided superior protection when compared to global ischemia or crystalloid cardioplegia in acutely ischemic hearts. The model employed is very close to the clinical situation due to the use of blood as a perfusate.

Perfusion approaches to blood conservation

There are several perfusion techniques that can contribute to blood conservation. Minimizing existing circuit components, using mini-circuits and the maneuver of retrograde autologous priming can be considered steps in prime reduction. Microplegia systems may also reduce systemic as well as cardiac hemodilutional effects. Cell savers can scavenge shed blood, wash the red cells, and may return the red cells to the patient in a concentrated form. When a patient is already hemodiluted, ultrafiltation can be used to hemoconcentrate the patient and to drive their existing hemoglobin levels up. Ultimately, the optimal form of blood conservation comes from team-work, communication, and a combination of efforts.

Minimally-Diluted Blood Cardioplegia Supplemented With Potassium and Magnesium for Combination of 'Initial, Continuous and Intermittent Bolus' Administration

BACKGROUND

The present study was designed to examine the hypothesis that minimally-diluted blood cardioplegia (BCP) supplemented with potassium and magnesium provides superior myocardial protection in comparison with the standard-diluted BCP for a combination of 'initial, continuous, and intermittent bolus' BCP administration.

METHODS AND RESULTS

Seventy patients undergoing elective coronary revascularization between 1997 and 2001 (M : F =55:15, mean age 67.6+/-7.5 years) were randomly divided into 2 groups: Group C (n=35) was given the standard 4:1-diluted blood-crystalloid BCP, and Group M (n=35) was given minimally-diluted BCP supplemented with potassium-chloride and magnesium-sulfate. The BCP temperature was maintained at 30 degrees C. Cardioplegic arrest was induced with 2 min of initial antegrade BCP infusion, followed by continuous retrograde BCP infusion. Intermittent antegrade BCP was infused every 30 min for 2 min. The time required for achieving cardioplegic arrest was significantly shorter in Group M (47.5+/-16.3 vs 62.5+/-17.6 s, p<0.0001). The number of patients showing spontaneous heart beat recovery after reperfusion was significantly larger in Group M (28 vs 15, p=0.0029), and the number of patients suffering from atrial fibrillation during the postoperative period was significantly smaller in Group M (n=3 vs 11, p=0.034). Both the postoperative maximum dopamine dose (3.57+/-2.46 vs 5.44+/-2.23 microg/kg per min, p=0.0014) and peak creatine kinase-MB (19.5+/-8.5 vs 25.8+/-11.9 IU/L, p=0.0128) were significantly less in Group M. The number of patients showing paradoxical movement of the ventricular septum in the early postoperative echocardiography was significantly smaller in Group M (9 vs 24, p=0.0007).

CONCLUSIONS

These results suggest that 'initial, continuous and intermittent bolus' administration of minimally-diluted BCP supplemented with potassium and magnesium is a reliable and effective technique for intraoperative myocardial protection.

Optimal dose and mode of delivery of Na+/H+ exchange-1 inhibitor are critical for reducing postsurgical ischemia-reperfusion injury

BACKGROUND

In clinical trials, perioperative intravenous Na(+)/H(+) exchange isoform-1 (NHE1) inhibitors were only moderately effective in high-risk patients undergoing surgical reperfusion (GUARDIAN trial). However, effective myocardial concentrations of NHE1 inhibitor may not have been achieved by parenteral administration alone. We tested the hypothesis that increasing doses of NHE1 inhibitor EMD 87580 ((2-methyl-4,5-di-(methylsulfonyl)-benzoyl)-guanidine) delivered in blood cardioplegia (BCP) and by parenteral route at reperfusion reduce myocardial injury after surgical reperfusion of evolving infarction.

METHODS

Twenty-six anesthetized dogs underwent 75 minutes of left anterior descending coronary artery occlusion, followed by cardiopulmonary bypass and 60 minutes of arrest with multidose 10 degrees C BCP. In the control group (n = 8), BCP was not supplemented. In the three EMD-BCP groups, BCP was supplemented with 10 micromol/L EMD 87580 (EMD-10, n = 5), 20 micromol/L EMD 87580 (EMD-20, n = 5), or 20 micromol/L EMD 87580 combined with an immediate reperfusion bolus (5 mg/kg intravenously) (EMD-20R, n = 8). The left anterior descending coronary artery occlusion was released just before the second infusion of BCP. Reperfusion continued for 120 minutes after discontinuation of cardiopulmonary bypass.

RESULTS

Postischemic systolic and diastolic function in the area at risk was dyskinetic in all groups. Infarct size (percentage of area at risk) was not significantly reduced in the EMD-10 (26.2% +/- 3.6%) and EMD-20 (22.5% +/- 2.4%) groups versus control (30.7% +/- 2.4%); however, infarct size was significantly reduced in the EMD-20R group (16.1% +/- 2.8%, p = 0.003). Edema in the area at risk in the EMD-10 (81.1% +/- 0.5% water content), EMD-20 (81.7% +/- 0.3%), and EMD-20R (81.9% +/- 0.3%) groups was less than in controls (83.2% +/- 0.2%), (p < 0.056). Neutrophil accumulation (myeloperoxidase activity) in postischemic area-at-risk myocardium was less in the EMD-20R group versus the control group (5.3 +/- 0.7 versus 8.7 +/- 1.4 absorbance units x min(-1) x g(-1); p = 0.05), which suggests an attenuated postischemic inflammatory response.

CONCLUSIONS

Optimal delivery of NHE1 inhibitor to the heart through combined cardioplegia and parenteral routes significantly attenuates myocardial injury after surgical reperfusion of regional ischemia. Timing, dose, and mode of delivery of NHE1 inhibitors are important to their efficacy.

How to avoid problems in redo coronary artery bypass

BACKGROUND

Redo cardiac surgery still carries higher mortality and increased morbidity as compared with primary coronary revascularizations. Various steps can be taken to decrease the incidences of adverse outcomes. From our experience, we have accumulated safe steps to be taken during the surgical procedure to reach a positive outcome.

METHODS

We reviewed our own experience of redo coronary artery bypass surgery (CABG) at two institutions during the last 4 years. Though the surgeons were the same at both institutions, because of institutional variability of patient referrals, operative equipment, anesthesia management, and preoperative care, we kept the data separate. Five surgeons performed CABG with almost similar myocardial preservation techniques; however, the surgical skill varied slightly depending on the seniority and clinical experience. We performed 433 redo coronary artery revascularizations at one institution and 201 in the second institution. Fifteen percent of these patients also had additional procedures, such as valve repair, valve replacement, or aneurysm resection. In this patient group, 160 patients underwent either urgent or emergent CABG. Urgent surgery was defined as patient revascularization during the same admission as cardiac catheterization, and emergency surgery was defined as a patient undergoing surgery on the same day as the catheterization, especially when hemodynamic instability was present. The total mortality was 7%, while the elective redo CABG mortality was 3%. The length of stay ranged from 8.5 to 12.6 days. The morbidity included perioperative stroke in 18 patients and nonfatal perioperative myocardial infarction (MI) in 19 patients. Major factors contributing to the mortality were stroke, perioperative bleeding and exploration, renal failure, respiratory failure, and malnutrition.

CONCLUSION

We outlined the precautions and safe surgical approaches to be undertaken during redo CABG for a successful outcome.

Intermittent antegrade hyperkalaemic warm blood cardioplegia supplemented with magnesium prevents myocardial substrate derangement in patients undergoing coronary artery bypass surgery

OBJECTIVE

The influence of the addition of magnesium on myocardial protection with intermittent antegrade warm blood hyperkalaemic cardioplegia in patients undergoing coronary artery surgery was investigated and compared with intermittent antegrade warm blood hyperkalaemic cardioplegia only.

METHODS

Twenty-three patients undergoing primary elective coronary revascularization were randomized to one of two different techniques of myocardial protection. In the first group, myocardial protection was induced using intermittent antegrade warm blood hyperkalaemic cardioplegia. In the second group, the same technique was used except that magnesium was added to the cardioplegia. Intracellular substrates (ATP, lactate and amino acids) were measured in left ventricular biopsies collected 5 min after institution of cardiopulmonary bypass, after 30 min of ischaemic arrest and 20 min after reperfusion.

RESULTS

There were no significant changes in the intracellular concentration of ATP or free amino acid pool in biopsies taken at the end of the period of myocardial ischaemia. However, the addition of magnesium prevented the significant increase in the intracellular concentration of lactate seen with intermittent antegrade warm blood hyperkalaemic cardioplegia. Upon reperfusion there was a significant fall in ATP and amino acid concentration when the technique of intermittent antegrade warm blood hyperkalaemic cardioplegia was used but not when magnesium was added to the cardioplegia.

CONCLUSIONS

This work shows that intermittent antegrade warm blood hyperkalaemic cardioplegia supplemented with magnesium prevents substrate derangement early after reperfusion.

Minimally diluted tepid blood cardioplegia

BACKGROUND

To evaluate the effects of minimally diluted tepid blood cardioplegia, a prospective, randomized study was undertaken.

METHODS

Thirty-seven patients undergoing isolated primary coronary artery bypass grafting were randomized to receive standard 4:1 diluted tepid blood cardioplegia (4:1 group, n = 18) or minimally diluted tepid blood cardioplegia (Mini group, n = 19). Cardioplegic solution was delivered in an intermittent antegrade fashion in both groups. Myocardial oxygen and lactate metabolism, release of the MB isoenzyme of creatine kinase and thiobarbituric acid reactive substances, and cardiac function were measured during and after the operation.

RESULTS

Myocardial oxygen consumption was significantly greater and lactate release was significantly lower in the Mini group than in the 4:1 group during cardioplegia. Minimally diluted blood cardioplegia resulted in more prompt resumption of lactate extraction, lower levels of release of the myocardial-specific isoenzyme of creatine kinase and thiobarbituric acid reactive substances during reperfusion, and better postoperative left ventricular function compared with the standard 4:1 cardioplegia.

CONCLUSIONS

Minimally diluted tepid blood cardioplegia may provide superior myocardial protection than the standard 4:1 dilution technique by optimizing the aerobic environment through an increase in oxygen supply during intermittent cardioplegia.