Risks and predictors of blood transfusion in pediatric patients undergoing open heart operations

Treatment and monitoring of coagulation abnormalities in children undergoing heart surgery

Bleeding is a considerable clinical problem during and after pediatric heart surgery. While the primary cause of bleeding is surgical trauma, its treatment is often complicated by the presence of coagulopathy. The principle causes of coagulopathy are discussed to provide a context for treatment. The role of laboratory and point of care tests, which aim to identify the cause of bleeding in the individual patient, is also discussed. An attempt is made to examine the current evidence for available therapies, including use of blood products and, more recently proposed, approaches based on human or recombinant factor concentrates.

Benefits and risks of red blood cell transfusion in pediatric patients undergoing cardiac surgery

As the number of neonates and young infants undergoing cardiac surgery requiring cardiopulmonary bypass (CPB) increases, red blood cell (RBC) transfusion will continue to be an integral part of the practice of pediatric cardiac anesthesiology. The decision of when to transfuse RBCs to these patients is complex and influenced by multiple factors such as size, presence of cyanotic heart disease, complexity of the surgical procedure, and the hemostatic alterations induced by CPB. The known benefits of RBC transfusion include an increase in the oxygen-carrying capacity of blood, improved tissue oxygenation, and improved hemostasis. Unfortunately, there is no minimum hemoglobin level that serves as a transfusion trigger for all pediatric patients undergoing cardiac surgery. Physiologic signs such as tachycardia, hypotension, low mixed venous oxygen saturation and increased oxygen extraction ratios can provide objective evidence of the need to augment a given hemoglobin level. Nevertheless, the benefits of RBC transfusion must be balanced against its risks and, in recent years, RBC transfusion has been subjected to intense scrutiny. The adverse consequences of RBC transfusion include the transmission of infectious diseases and immune-mediated and nonimmune-mediated complications. Advances in donor selection, infectious disease testing of donated blood, use of leukocyte reduction and irradiation of blood in defined situations have improved the safety of the blood supply in terms of infection transmission. However, a growing number of prospective randomized clinical trials are finding an association between RBC transfusion and an increased risk of morbidity and mortality even with the use of leuko-reduced blood. Thus, it is becoming increasingly important that the decision to transfuse RBCs be made with a thorough understanding of the benefit-to-risk ratio. This review addresses the benefits and risks of RBC transfusion, pertinent data acquired in the setting of congenital cardiac surgery and techniques designed to minimize the need for RBC transfusion.

Red blood cell transfusion for infants with single-ventricle physiology

The purpose of this study was to assess how red blood cell (RBC) transfusions impact hemodynamic parameters in infants with single-ventricle lesions. This was a retrospective chart review. The setting was a pediatric cardiac intensive care unit at a tertiary care children's hospital. Fifty-nine patients <1 year of age with single-ventricle physiology who received a blood transfusion between December 2007 and April 2009 were analyzed. They received a total of 183 transfusions. Exclusion criteria included transfusions given within 72 h of cardiac surgery or transfusions given to patients with active bleeding. There were no interventions. The study population was divided into terciles based on pretransfusion hemoglobin (Hgb) concentration. The pretransfusion Hgb concentration in group A was 7.8 to 12.3 gm/dl, in group B was 12.4 to 13.2 gm/dl, and in group C was 13.3 to 15.7 gm/dl. Heart rate, blood pressure, arterial saturation, and cerebral near-infrared spectroscopy (cNIRS) values before transfusion, as well as at 1, 2, 4, 8, and 12 h after transfusion, were collected. There was significant improvement in diastolic blood pressure, arterial saturation, and cNIRS in group A after 12 h. Transfusions given in group B also resulted in improvement in diastolic blood pressure and arterial saturation, with less robust response of cNIRS. In group C, only arterial saturation values increased significantly. RBC transfusions can improve hemodynamics and markers of oxygen delivery in infants with single-ventricle physiology, but further studies are needed to determine an optimal Hgb level in this population. Interventions to increase Hgb above this level may be of limited benefit.

Red blood cell transfusion in critically ill children: a narrative review

OBJECTIVE

To review the pathophysiology of anemia, as well as transfusion-related complications and indications for red blood cell (RBC) transfusion, in critically ill children. Although allogeneic blood has become increasingly safer from infectious agents, mounting evidence indicates that RBC transfusions are associated with complications and unfavorable outcomes. As a result, there has been growing interest and efforts to limit RBC transfusion, and indications are being revisited and revamped. Although a so-called restrictive RBC transfusion strategy has been shown to improve morbidity and mortality in critically ill adults, there have been relatively few studies on RBC transfusion performed in critically ill children.

DATA SOURCES

Published literature on transfusion medicine and outcomes of RBC transfusion. STUDY SELECTION, DATA EXTRACTION, AND SYNTHESIS: After a brief overview of physiology of oxygen transportation, anemia compensation, and current transfusion guidelines based on available literature, risks and outcomes of transfusion in general and in critically ill children are summarized in conjunction with studies investigating the safety of restrictive transfusion strategies in this patient population.

CONCLUSIONS

The available evidence does not support the extensive use of RBC transfusions in general or critically ill patients. Transfusions are still associated with risks, and although their benefits are established in limited situations, the associated negative outcomes in many more patients must be closely addressed. Given the frequency of anemia and its proven negative outcomes, transfusion decisions in the critically ill children should be based on individual patient's characteristics rather than generalized triggers, with consideration of potential risks and benefits, and available blood conservation strategies that can reduce transfusion needs.

Blood transfusion after pediatric cardiac surgery is associated with prolonged hospital stay

BACKGROUND

Red blood cell transfusion is associated with morbidity and mortality among adults undergoing cardiac surgery. We aimed to evaluate the association of transfusion with morbidity among pediatric cardiac surgical patients.

METHODS

Patients discharged after cardiac surgery in 2003 were retrospectively reviewed. The red blood cell volume administered during the first 48 postoperative hours was used to classify patients into nonexposure, low exposure (≤15 mL/kg), or high exposure (>15 mL/kg) groups. Cox proportional hazards modeling was used to evaluate the association of red blood cell exposure to length of hospital stay (LOS).

RESULTS

Of 802 discharges, 371 patients (46.2%) required blood transfusion. Demographic differences between the transfusion exposure groups included age, weight, prematurity, and noncardiac structural abnormalities (all p<0.001). Distribution of Risk Adjusted Classification for Congenital Heart Surgery, version 1 (RACHS-1) categories, intraoperative support times, and postoperative Pediatric Risk of Mortality Score, Version III (PRISM-III) scores varied among the exposure groups (p<0.001). Median duration of mechanical ventilation (34 hours [0 to 493] versus 27 hours [0 to 621] versus 16 hours [0 to 375]), incidence of infection (21 [14%] versus 29 [13%] versus 17 [4%]), and acute kidney injury (25 [17%] versus 29 [13%] versus 34 [8%]) were highest in the high transfusion exposure group when compared with the low or nontransfusion groups (all p<0.001). In a multivariable Cox proportional hazards model, both the low transfusion group (adjusted hazard ratio [HR] 0.80, 95% confidence interval [CI]: 0.66 to 0.97, p=0.02) and high transfusion group (adjusted HR 0.66, 95% CI: 0.53 to 0.82, p<0.001) were associated with increased LOS. In subgroup analyses, both low transfusion (adjusted HR 0.81, 95% CI: 0.65 to 1.00, p=0.05) and high transfusion (adjusted HR 0.65, 95% CI: 0.49 to 0.87, p=0.004) in the biventricular group but not in the single ventricle group was associated with increased LOS.

CONCLUSIONS

Blood transfusion is associated with prolonged hospitalization of children after cardiac surgery, with biventricular patients at highest risk for increased LOS. Future studies are necessary to explore this association and refine transfusion practices.

Neurocognitive profiles of preterm infants randomly assigned to lower or higher hematocrit thresholds for transfusion

OBJECTIVE

Preterm infants are frequently transfused with red blood cells based on standardized guidelines or clinical concerns that anemia taxes infants' physiological compensatory mechanisms and thereby threatens their health and well-being. The impact of various transfusion guidelines on long-term neurocognitive outcome is not known. The purpose of this study is to evaluate long-term neurocognitive outcome on children born prematurely and treated at birth with different transfusion guidelines.

METHODS

Neurocognitive outcomes were examined at school age for 56 preterm infants randomly assigned to a liberal (n = 33) or restrictive (n = 23) transfusion strategy. Tests of intelligence, achievement, language, visual-spatial/motor, and memory skills were administered. Between-group differences were assessed.

RESULTS

Those in the liberal transfusion group performed more poorly than those in the restrictive group on measures of associative verbal fluency, visual memory, and reading.

CONCLUSIONS

Findings highlight possible long-term neurodevelopmental consequences of maintaining higher hematocrit levels.

Blood transfusion is associated with prolonged duration of mechanical ventilation in infants undergoing reparative cardiac surgery

OBJECTIVE

Perioperative transfusion has adverse effects in adults undergoing cardiac surgery. We sought to investigate whether greater use of blood and blood products might be an independent predictor of prolonged postoperative recovery, indicated by duration of mechanical ventilation (DMV), after reparative infant heart surgery.

DESIGN

Secondary analysis of prospectively collected data from two randomized trials of hematocrit strategy during cardiopulmonary bypass in infant heart surgery to explore the association of DMV with perioperative transfusion and other variables.

SETTING

Tertiary pediatric hospital.

PATIENTS

Two hundred seventy infants undergoing two ventricle corrective cardiac surgery without aortic arch reconstruction.

MEASUREMENTS AND MAIN RESULTS

In univariable analyses, longer DMV was associated with younger age and lower weight at surgery, diagnostic group, and higher intraoperative and postoperative blood product transfusion (each p < .001). In multivariable proportional hazard regression, longer total support time and greater intraoperative and early postoperative blood products per kg were the strongest predictors of longer DMV. Patients in the highest tertile of intraoperative blood products per kg had an instantaneous risk of being extubated approximately half that of patients in the lowest tertile (hazard ratio, 0.51; 95% confidence interval, 0.35, 0.73). Patients who received any blood products on postoperative day 1, compared with those who did not, had a hazard ratio for extubation of 0.65 (95% confidence interval, 0.50, 0.85).

CONCLUSIONS

In this exploratory secondary analysis of infants undergoing two ventricular repair of congenital heart disease without aortic arch obstruction, greater intraoperative and early postoperative blood transfusion emerged as potential important risk factors for longer DMV. Future prospective clinical trials are needed to determine whether reduction in blood product administration hastens postoperative recovery after infant heart surgery.

Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery

BACKGROUND

The majority of pediatric cardiac surgery patients receive blood transfusions. We hypothesized that the routine use of intraoperative thromboelastometry to guide transfusion decisions would reduce the overall proportion of patients receiving transfusions in pediatric cardiac surgery.

METHODS

One hundred pediatric cardiac surgery patients were included in the study. Fifty patients (study group) were prospectively included and compared with 50 procedure- and age-matched control patients (control group). In the study group, thromboelastometry, performed during cardiopulmonary bypass, guided intraoperative transfusions. Intraoperative and postoperative transfusions of packed red blood cells, fresh frozen plasma, platelets, and fibrinogen concentrates, and postoperative blood loss and hemoglobin levels were compared between the 2 groups.

RESULTS

The proportion of patients receiving any intraoperative or postoperative transfusion of packed red blood cells, fresh frozen plasma, platelets, or fibrinogen concentrates was significantly lower in the study group than in the control group (32 of 50 [64%] vs 46 of 50 [92%], respectively; P < 0.001). Significantly fewer patients in the study group received transfusions of packed red blood cells (58% vs 78%, P = 0.032) and plasma (14% vs 78%, P < 0.001), whereas more patients in the study group received transfusions of platelets (38% vs 12%, P = 0.002) and fibrinogen concentrates (16% vs 2%, P = 0.015). Neither postoperative blood loss nor postoperative hemoglobin levels differed significantly between the study group and the control group.

CONCLUSIONS

The results suggest that routine use of intraoperative thromboelastometry in pediatric cardiac surgery to guide transfusions is associated with a reduced proportion of patients receiving transfusions and an altered transfusion pattern.

Circulating matrix metalloproteinase levels after ventricular septal defect repair in infants

BACKGROUND

Surgery for congenital heart disease initiates a complex inflammatory response that can influence the postoperative course. However, broad integration of the cytokine and proteolytic cascades (matrix metalloproteinases: MMPs), which may contribute to postoperative outcomes, has not been performed.

METHODS AND RESULTS

Using a low-volume (50-60 μL), high-sensitivity, multiplex approach, we serially measured a panel of cytokines (interleukins 2, 4, 6, 8, and 10, tumor necrosis factor alpha, interleukin 1β, and granulocyte-macrophage colony stimulating factor) and matrix metalloproteinases (matrix metalloproteinases 2, 3, 7, 8, 9, 12, and 13) in patients (n = 9) preoperatively and after repair of ventricular septal defect. Results were correlated with outcomes such as inotropic requirement, oxygenation, and fluid balance. Serial changes in perioperative plasma levels of the cytokines and matrix metalloproteinases exhibited distinct temporal profiles. Plasma levels of interleukins 2, 8, and 10 and matrix metalloproteinase 9 peaked within 4 hours, whereas levels of matrix metalloproteinase 3 and 8 remained elevated at 24 and 48 hours after crossclamp removal. Area-under-the-curve analysis of early cytokine levels were associated with major clinical variables, including inverse correlations between early interleukin 10 levels and cumulative inotrope requirement at 48 hours (r: -0.85; P < .005) and late matrix metalloproteinase 7 levels and cumulative fluid balance (r: -0.90; P < .001).

CONCLUSIONS

The unique findings of this study were that serial profiling a large array of cytokines and proteolytic enzymes after surgery for congenital heart disease can provide insight into relationships between changes in bioactive molecules to early postoperative outcomes. Specific patterns of cytokine and matrix metalloproteinase release may hold significance as biomarkers for predicting and managing the postoperative course after surgery for congenital heart disease.

Effects of aprotinin or tranexamic acid on proteolytic/cytokine profiles in infants after cardiac surgery

BACKGROUND

After cardiopulmonary bypass (CPB), elaboration of cytokines, and subsequent induction of interstitial proteases, such as matrix metalloproteinases (MMPs), can result in a complex postoperative course. The serine protease inhibitor, aprotinin, which has been used in congenital heart surgery putatively for modulating fibrinolysis is now unavailable, necessitating the use of lysine analogues such as tranexamic acid (TXA). The present study tested the hypothesis that distinctly different plasma profiles of signaling molecules and proteases would be differentially affected after the administration of aprotinin or TXA in the context of congenital cardiac surgery and CPB.

METHODS

Thirty-seven patients (age, 4.8 +/- 0.3 months) undergoing corrective surgery for ventricular septal defect and tetralogy of Fallot received either aprotinin (n = 22) or TXA (n = 15). Using a high throughput multiplex suspension immunoassay, plasma was serially quantified for cytokines and MMPs: before aprotinin or TXA (baseline), after separation from CPB, and 4, 12, 24, and 48 hours post-CPB.

RESULTS

Tumor necrosis factor-alpha increased initially after CPB in both the aprotinin and TXA groups, but at 24 and 48 hours post-CPB was approximately 50% lower in the aprotinin group (p < 0.05). The IL-10 levels were threefold higher in the TXA group compared with the aprotinin group immediately post-CBP (p < 0.05). Plasma levels of MMP types associated with inflammation, MMP-8, and MMP-9, were twofold higher in the late post-CPB period in the TXA group when compared with the aprotinin group.

CONCLUSIONS

After ventricular septal defect or tetralogy of Fallot repair in children, cytokine induction occurs, which is temporally related to the emergence of a specific MMP profile. Moreover, these unique findings demonstrated differential effects between the serine protease inhibitor aprotinin and the lysine analogue TXA with respect to cytokine and MMP induction in the early postoperative period. The different cytokine-proteolytic profile between these antifibrinolytics may in turn influence biologic processes in the postoperative period.