Treatment and monitoring of coagulation abnormalities in children undergoing heart surgery

Factor XIII levels, clot strength, and impact of fibrinogen concentrate in infants undergoing cardiopulmonary bypass: a mechanistic sub-study of the FIBCON trial

BACKGROUND

Acquired factor XIII (FXIII) deficiency after major surgery can increase postoperative bleeding. We evaluated FXIII contribution to clot strength and the effect of fibrinogen concentrate administration on FXIII activity in infants undergoing cardiac surgery using cardiopulmonary bypass.

METHODS

We conducted a prospectively planned, mechanistic sub-study, nested within the Fibrinogen Concentrate Supplementation in the Management of Bleeding During Paediatric Cardiopulmonary Bypass: A Phase 1B/2A, Open-Label Dose Escalation Study (FIBCON) trial, which investigated fibrinogen concentrate supplementation during cardiopulmonary bypass (ISRCTN: 50553029) in 111 infants (median age 6.4 months). The relationships between platelet number, fibrinogen concentration, and FXIII activity with rotational thromboelastometry clot strength (EXTEM-MCF) in blood taken immediately before cardiopulmonary bypass and after separation from bypass were estimated using multivariable linear regression. Changes in coagulation variables over time were quantified using a generalised linear model comparing three groups: fibrinogen concentrate-supplemented infants, placebo, and a third cohort with lower bleeding risk.

RESULTS

Overall, 48% of the variability (multivariable R²) in EXTEM-MCF clot strength was explained by three factors: the largest contribution was from FXIII activity (partial R²=0.21), followed by platelet number (partial R²=0.14), and fibrinogen concentration (partial R²=0.095). During cardiopulmonary bypass, mean platelet count fell by a similar amount in the three groups (-36% to -41%; interaction P=0.98). Conversely, fibrinogen concentration increased in all three groups: 132% in the fibrinogen concentrate-supplemented group, 26% in the placebo group, and 51% in the low-risk group. A similar increase was observed for FXIII activity (61%, 23%, and 25%, respectively; interaction P<0.0001).

CONCLUSIONS

FXIII contribution to clot strength is considerable in infants undergoing cardiac surgery. Fibrinogen concentrate supplementation also increased FXIII activity, and hence clot strength.

CLINICAL TRIAL REGISTRATION

ISRCTN: 50553029.

Recombinant Factor VIIa in Pediatric Cardiac Surgery

OBJECTIVES

Recombinant activated factor VIIa (rVIIa) is used off-label for refractory bleeding after cardiac surgery. This study reviewed the indications, usage rates, and complications of rVIIa.

DESIGN

A retrospective case-control observational study.

SETTING

A single quaternary pediatric hospital.

PARTICIPANTS

All children undergoing cardiac surgery with cardiopulmonary bypass over a three-year period.

INTERVENTIONS

Administration of rVIIa as rescue therapy for refractory bleeding after weaning from cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

Onethousand, five hundred fifteen cardiopulmonary bypass procedures were reviewed. Patients receiving rVIIa were each matched to two control patients by age, procedure type, and bypass time. Data collected included weight, crossclamp time, anticoagulant and antifibrinolytic dose, return to the operating room for bleeding, thrombotic events, and extracorporeal membrane oxygenation (ECMO) circuit interventions. Forty-two patients received rVIIa (2.8%). Major systemic thrombotic complications were observed in 19% (controls 12.5%) of patients; 80% of recombinant factor VIIa patients requiring postoperative ECMO had interventions for circuit thrombosis (controls 31.25%); 4.76% of rVIIa recipients required reexploration for intractable bleeding (controls 1.39%).

CONCLUSIONS

This study added to understanding regarding the use of recombinant factor VIIa in pediatric cardiac surgery and reported increased thrombotic complications, especially for children who progress to ECMO. Prospective studies to better understand the pathophysiology of coagulopathy and hemorrhage in pediatric cardiac surgery and the role of hemostatic agents, such as rVIIa, are required.

TEG Platelet Mapping and Impedance Aggregometry to Predict Platelet Transfusion During Cardiopulmonary Bypass in Pediatric Patients

Background: Cardiopulmonary bypass-related platelet dysfunction can increase the risk of intra- and post-operative bleeding in children undergoing cardiac surgery. More accurate laboratory tests that identify acquired platelet abnormalities could allow for rapid identification of patients at risk of bleeding and provide therapies that could reduce bleeding and platelet transfusions. We hypothesized that thromboelastography with platelet mapping (TEG-PM) and multiple electrode impedance aggregometry (MEIA) as functional measures of platelet function would predict who will require platelet transfusion. Our secondary hypothesis was that platelet aggregation at both arachidonic acid (AA) and adenosine diphosphate (ADP) receptors would correlate between TEG-PM and MEIA results. Methods: In this prospective study from August 2013 to December 2015, children from newborn to 5 years of age with congenital heart disease undergoing cardiopulmonary bypass had blood samples collected and analyzed at four time points: pre-bypass, post-bypass, post-operatively on arrival to the Cardiac Intensive Care Unit, and 24 h after arrival. Results: Of the 44 patients analyzed, the 10 patients who received peri-operative platelet transfusion were significantly younger (p = 0.05), had higher STAT (Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery) Mortality Categories (p < 0.002) and longer cardiopulmonary bypass times (p = 0.02). In univariate analysis, four variables were associated with peri-operative platelet transfusion: pre-operative age [OR 0.95 (0.93, 0.98), p = 0.03], cardiopulmonary bypass time [1.5 (1.31, 1.68), p = 0.008], STAT Mortality Category [3.64 (3.40, 3.87), p < 0.001], and TEG-PM ADP [0.79 (0.65, 0.93), p = 0.04]. ROC analysis demonstrated moderate predictive value of TEG-PM ADP with AUC of 0.745 (0.59, 0.91). A TEG-PM ADP value of less than or equal to 21 had 85% sensitivity and 70% specificity for platelet transfusion. In the multivariate analysis, only STAT Mortality Category predicted platelet transfusion. TEG-PM and MEIA results correlated for the AA receptor at all 4 time points, but the same tests at the ADP receptors did not correlate. Conclusions: TEG-PM ADP may provide more clinically relevant information regarding platelet function compared to the MEIA at the ADP receptor in children requiring cardiopulmonary bypass. There was limited correlation between TEG-PM and MEIA results which raises a concern about the accuracy of these tests at the ADP receptor. Lower pre-operative TEG-PM ADP MA may predict intra-operative platelet transfusions; however, larger studies are needed to determine the utility of TEG-PM and MEIA in guiding platelet transfusions in this population.

Perioperative monitoring of platelet function in paediatric cardiac surgery by thromboelastometry, or platelet aggregometry?

BACKGROUND

Impaired platelet function increases the risk of bleeding complications in cardiac surgery. Reliable assessment of platelet function can improve treatment. We investigated whether thromboelastometry detects clinically significant preoperative, perioperative, and postoperative adenosine diphosphate (ADP)-dependent platelet dysfunction in paediatric cardiac surgery patients.

METHODS

Fifty-seven children were included in a single-centre prospective observational study. Clot formation (modified rotational thromboelastometry with heparinase, HEPTEM) and platelet aggregation (multiple electrode aggregometry) were analysed at five time points before, during, and after surgery. The accuracy of thromboelastometric indices of platelet function [maximal clot firmness (MCF) and clot formation time (CFT)] to detect ADP-dependent platelet dysfunction (defined as ADP-induced aggregation ≤30 units) was calculated with receiver operating characteristics analysis, which also identified optimal cut-off levels. Positive and negative predictive values for the identified cut-off levels (CFT≥166 s; MCF≤43 mm) to detect platelet function were determined.

RESULTS

The MCF and CFT were highly accurate in predicting platelet dysfunction during cardiopulmonary bypass [CPB; area under the aggregation curve 0.89 (95% confidence interval 0.80-0.97) and 0.86 (0.77-0.96), respectively] but not immediately after CPB [0.64 (0.48-0.79) and 0.67 (0.52-0.82), respectively] or on arrival at the intensive care unit [0.53 (0.37-0.69) and 0.60 (0.44-0.77), respectively]. The positive and negative predictive values were acceptable during CPB (87 and 67%, respectively, for MCF≤43 mm; 80 and 100% for CFT≥166 s) but markedly lower after surgery.

CONCLUSION

In paediatric cardiac surgery, thromboelastometry has acceptable ability to detect ADP-dependent platelet dysfunction during, but not after, CPB.

Strategies for Prevention and Management of Bleeding Following Pediatric Cardiac Surgery on Cardiopulmonary Bypass: A Scoping Review

OBJECTIVE

We aimed to systematically describe, via a scoping review, the literature reporting strategies for prevention and management of mediastinal bleeding post pediatric cardiopulmonary bypass surgery.

DATA SOURCES

MEDLINE, EMBASE, PubMed, and Cochrane CENTRAL Register.

STUDY SELECTION

Two authors independently screened publications from 1980 to 2016 reporting the effect of therapeutic interventions on bleeding-related postoperative outcomes, including mediastinal drain loss, transfusion, chest re-exploration rate, and coagulation variables. Inclusions: less than 18 years, cardiac surgery on cardiopulmonary bypass.

DATA EXTRACTION

Data from eligible studies were extracted using a standard data collection sheet.

DATA SYNTHESIS

Overall, 299 of 7,434 screened articles were included, with observational studies being almost twice as common (n = 187, 63%) than controlled trials (n = 112, 38%). The most frequently evaluated interventions were antifibrinolytic drugs (75 studies, 25%), blood products (59 studies, 20%), point-of-care testing (47 studies, 16%), and cardiopulmonary bypass circuit modifications (46 studies, 15%). The publication rate for controlled trials remained constant over time (4-6/yr); however, trials were small (median participants, 51; interquartile range, 57) and overwhelmingly single center (98%). Controlled trials originated from 22 countries, with the United States, India, and Germany accounting for 50%. The commonest outcomes were mediastinal blood loss and transfusion requirements; however, these were defined inconsistently (blood loss being reported over nine different time periods). The majority of trials were aimed at bleeding prevention (98%) rather than treatment (10%), nine studies assessed both.

CONCLUSIONS

Overall, this review demonstrates small trial sizes, low level of evidence, and marked heterogeneity of reported endpoints in the included studies. The need for more, higher quality studies reporting clinically relevant, comparable outcomes is highlighted. Emerging fields such as the use of coagulation factor concentrates, goal-directed guidelines, and anti-inflammatory therapies appear to be of particular interest. This scoping review can potentially guide future trial design and form the basis for therapy-specific systematic reviews.

Impact and Challenges of a Policy Change to Early Track Extubation in the Operating Room for Fontan

While policy changes toward early extubation in the operating room (OR) have been commonly seen in palliative surgeries in single ventricle anatomy, no systematic assessment of their impact on patient outcome has been reported. All patients aged 0-17 years admitted to a PICU in a quaternary children's hospital for post-operative management following a primary Fontan procedure between 2005 and 2011 were included. Patients for revision of Fontan or patients admitted to adult Cardiovascular Intensive Care Unit were excluded. Practice policy was changed from routine extubation in the PICU to early extubation in OR in January 2008. Data were compared between the pre-policy-change era (2005-2007) and the post-policy-change era (2008-2011) to assess the impact of the change on patient outcomes. Generalized linear regression (GLM) and interrupted time series (ITS) analysis were used to access the effect of policy change on PICU length of stay and post-operative fluid balance, adjusting for potential confounders using propensity scores. Root cause analysis (RCA) was conducted to describe causes of failed extubation and challenges of this policy change. One hundred twenty-seven children met inclusion criteria. Average body weight was 14.7 kg [standard deviation (SD) 3.9], and age was 3.5 years (SD 1.9). A clear change in extubation practice occurred between the pre- versus post-policy-change eras: 97.5 % were extubated in the PICU in the pre-policy-change era, as compared to 15.0 % in the post-policy-change era. The average PICU length of stay was shortened by 4.1 days from the pre-policy-change era to the post-policy-change era [95 % CI -1.2 to -6.9, p < 0.01] in the GLM, whereas the ITS analysis did not show a statistically significant difference [95 % CI 1.8 to -2.5] (p = 0.23). No statistically significant difference was observed in the fluid balance in the 24 h post-operation in both analyses. Sixteen patients (16/127, 12.6 %) were reintubated mainly for hemodynamic instability in the pre-policy-change era (6/39, 15.4 %) and excessive bleeding or respiratory etiologies in the post-policy-change era (10/88, 11.4 %). Significant reduction of PICU length of stay was achieved without any evidence of worsening of patient outcomes. RCA suggests watchful observations with respect to bleeding and respiratory etiologies are the key to prevent failure of extubation in the current practice.

Rotational thromboelastometry in the diagnosis of coagulopathy in major pediatric surgical operations

OBJECTIVES

To examine the correlation between rotational thromboelastometry (ROTEM) and coagulopathy after major pediatric surgical operations.

METHODS

From November 2013 until April 2015, pediatric cases who underwent major noncardiac surgeries and met the coagulopathy-risk criteria were reviewed for postoperative clinically significant coagulopathy (CSC). Two ROTEM studies, EXTEM and INTEM, were performed at the immediately postoperatively without the results being taken into any clinical decision making.

RESULTS

Seventy-seven operations on 73 patients were included in this analysis. CSC occurred following 24 operations (32%) with a significantly higher incidence when a patient had a higher coagulopathy risk. On univariate analysis, evidence of diffuse bleeding in the operative field and massive bleeding were the 2 parameters with the strongest association with CSC. INTEM and EXTEM had specificities in diagnosing CSC of 75.5% and 94.3%, respectively. When each individual EXTEM and INTEM item was analyzed against CSC using ROC analysis, clot forming time (CFT) gave the largest under the curve area. The cut-off CFTs that gave the highest sensitivity and specificity in this study were 120seconds for EXTEM and 100seconds for INTEM.

CONCLUSION

Postoperative coagulopathy is a risk that should always be considered in pediatric surgical operations. Thromboelastometry can be a hemostatic test providing high predictive value for this condition.

Evaluation of dynamic parameters of thrombus formation measured on whole blood using rotational thromboelastometry in children undergoing cardiac surgery: a descriptive study

BACKGROUND

Total thrombus formation velocity calculated using amplitude parameters obtained at different times could be used to estimate the amplification and the propagation phases observed during coagulation processes, and therefore might be useful to predict postoperative hemostatic products administration in pediatric patients.

METHODS

We retrospectively analyzed data from 49 children <3 months of age who underwent cardiac surgery. Children ≤1 month of age routinely received fresh frozen plasma during bypass while children >1 month of age did not. The EXTEM parameters were used to calculate velocity curves using amplitudes obtained at different times, the area under the curve called total thrombus formation and the maximum rate of thrombus formation. These parameters were compared between children who received fresh frozen plasma and those who did not. Receiver operating characteristics curves were used to define variables that could be used to predict postoperative fresh frozen plasma transfusion.

RESULTS

Total thrombus formation and maximum rate of thrombus formation significantly increased in children who received fresh frozen plasma compared to those who did not. Both total thrombus formation and maximum rate of thrombus formation have a better specificity to predict postoperative fresh frozen plasma transfusion compared to clotting time or maximal clot firmness.

CONCLUSION

Based on this descriptive study, dynamic ROTEM(®) parameters of total thrombus formation could be used to estimate the amplification and the propagation phases of coagulation in children. These parameters might be used in further well-designed study to predict the need for hemostatic products in children undergoing cardiac surgery with cardiopulmonary bypass.

Marked changes in platelet count and function following pediatric congenital heart surgery

BACKGROUND

Reduced hemostatic capacity is common following congenital heart surgery using cardiopulmonary bypass (CPB). The etiology is multifactorial with dilutional coagulopathy, as well as platelet adhesion and activation in the CPB circuit and oxygenator. The purpose of the present study was to evaluate platelet count and function in children following CPB.

METHODS

In a prospective, observational study comprising 40 children, platelet count and function (Multiplate Analyzer(®)) were measured before surgery, immediately after bypass, and on the first postoperative day. Furthermore, conventional coagulation analysis and thromboelastometry (ROTEM(®)) were carried out.

RESULTS

A significant decrease in platelet count was observed immediately after coming of bypass (P < 0.001) and persisted to the first postoperative day (P = 0.002). Platelet function was reduced immediately after bypass after induction with ADP (P < 0.001) or TRAP (P = 0.03). The duration of CPB correlated significantly with the decrease in platelet count (r = -0.62, P = 0.0001) and reduction in platelet function (r = -0.42-0.63; P < 0.01). Moderate to deep hypothermia during CPB was associated with a decreased platelet function (P = 0.01-0.12), whereas cyanosis or previous heart surgery caused no further changes in platelet function following CPB.

CONCLUSION

Both platelet count and platelet function were significantly reduced after CPB in children undertaken correctional heart surgery. Duration of CPB and hypothermia was associated with significant changes in platelet function.

Coagulation and the surgical neonate

Both coagulopathy and abnormal thrombosis can complicate the anesthetic and surgical management of neonatal patients; however, the patterns of bleeding and thrombosis in neonates differ from those in adults or older children. Severe coagulopathic bleeding most commonly occurs during heart surgery and almost certainly contributes to morbidity and mortality in this population. Such severe bleeding is rare during other surgery; the exception is babies presenting to the operating room with established coagulopathy secondary to severe sepsis. Alternatively, pathological thrombosis will mainly occur in association with indwelling vascular access devices or surgically created vascular shunts. There are important differences between the coagulation system in neonates and older patients. The implication of this is that therapies established in other patient groups will not be optimal for neonates without adaptation. While evidence from high-quality clinical trials is rarely available, an understanding of how coagulation in neonates differs can help to guide practice. This review will discuss important differences between the coagulation system of neonates and older patients and how these relate to newer models of coagulation. The emphasis will be on issues likely to impact on perioperative care. In particular, the management of severe bleeding, the manipulation of coagulation during heart surgery, and the management of coagulopathy in septic neonates will be discussed in detail.

Implementation of a transfusion algorithm to reduce blood product utilization in pediatric cardiac surgery

AIM

The goal of this project is to measure the impact of standardization of transfusion practice on blood product utilization and postoperative bleeding in pediatric cardiac surgery patients.

BACKGROUND

Transfusion is common following cardiopulmonary bypass (CPB) in children and is associated with increased mortality, infection, and duration of mechanical ventilation. Transfusion in pediatric cardiac surgery is often based on clinical judgment rather than objective data. Although objective transfusion algorithms have demonstrated efficacy for reducing transfusion in adult cardiac surgery, such algorithms have not been applied in the pediatric setting.

METHODS

This quality improvement effort was designed to reduce blood product utilization in pediatric cardiac surgery using a blood product transfusion algorithm. We implemented an evidence-based transfusion protocol in January 2011 and monitored the impact of this algorithm on blood product utilization, chest tube output during the first 12 h of intensive care unit (ICU) admission, and predischarge mortality.

RESULTS

When compared with the 12 months preceding implementation, blood utilization per case in the operating room odds ratio (OR) for the 11 months following implementation decreased by 66% for red cells (P = 0.001) and 86% for cryoprecipitate (P < 0.001). Blood utilization during the first 12 h of ICU did not increase during this time and actually decreased 56% for plasma (P = 0.006) and 41% for red cells (P = 0.031), indicating that the decrease in OR transfusion did not shift the transfusion burden to the ICU. Postoperative bleeding, as measured by chest tube output in the first 12 ICU hours, did not increase following implementation of the algorithm. Monthly surgical volume did not change significantly following implementation of the algorithm (P = 0.477). In a logistic regression model for predischarge mortality among the nontransplant patients, after accounting for surgical severity and duration of CPB, use of the transfusion algorithm was associated with a 0.247 relative risk of mortality (P = 0.013).

CONCLUSIONS

These results indicate that introduction of an objective transfusion algorithm in pediatric cardiac surgery significantly reduces perioperative blood product utilization and mortality, without increasing postoperative chest tube losses.

Successful aortic valve replacement surgery in a patient with severe haemophilia a with low titre inhibitor

In spite of the modern day innovations, managing severe Haemophilia patients with inhibitors continues to be a challenge. The management of patients with severe haemophilia with inhibitors who are undergoing major surgeries like open heart surgery is technically demanding, fraught with peri-operative complications and needs a multidisciplinary approach. We describe a young man with severe haemophilia with low titre inhibitors who underwent a successful open heart surgery and aortic valve replacement, supported only with bolus doses of Factor VIII and tranexamic acid without any complications.