Management approaches to platelet-related microvascular bleeding in cardiothoracic surgery

Effects of subcutaneous vs. oral nanoparticle-mediated insulin delivery on hemostasis disorders in type 1 diabetes: A rat model study

Complications associated with Type 1 diabetes (T1D) have complex origins that revolve around chronic hyperglycemia; these complications involve hemostasis disorders, coagulopathies, and vascular damage. Our study aims to develop innovative approaches to minimize these complications and to compare the outcomes of the new approach with those of traditional methods. To achieve our objective, we designed novel nanoparticles comprising covalent organic frameworks (nCOF) loaded with insulin, termed nCOF/Insulin, and compared it to subcutaneous insulin to elucidate the influence of insulin delivery methods on various parameters, including bleeding time, coagulation factors, platelet counts, cortisol plasma levels, lipid profiles, and oxidative stress parameters. Traditional subcutaneous insulin injections exacerbated hemostasis disorder and vascular injuries in streptozotocin (STZ)-induced diabetic rats through increasing plasma triglycerides and lipid peroxidation. Conversely, oral delivery of nCOF/Insulin ameliorated hemostatic disorders and restored the endothelial oxidant/antioxidant balance by reducing lipid peroxidation and enhancing the lipid profile. Our study pioneers the understanding of how STZ-induced diabetes disrupts bleeding time, induces a hypercoagulable state, and causes vascular damage through lipid peroxidation. Additionally, it provides the first evidence for the involvement of subcutaneous insulin treatment in exacerbating vascular and hemostasis disorders in type 1 diabetes (T1D). Introducing an innovative oral insulin delivery via the nCOF approach represents a potential paradigm shift in diabetes management and patient care and promises to improve treatment strategies for type 1 Diabetes.

Microfluidic viscometer by acoustic streaming transducers

Measurement of fluid viscosity represents a huge need for many biomedical and materials processing applications. Sample fluids containing DNA, antibodies, protein-based drugs, and even cells have become important therapeutic options. The physical properties, including viscosity, of these biologics are critical factors in the optimization of the biomanufacturing processes and delivery of therapeutics to patients. Here we demonstrate an acoustic microstreaming platform termed as microfluidic viscometer by acoustic streaming transducers (μVAST) that induces fluid transport from second-order microstreaming to measure viscosity. Validation of our platform is achieved with different glycerol content mixtures to reflect different viscosities and shows that viscosity can be estimated based on the maximum speed of the second-order acoustic microstreaming. The μVAST platform requires only a small volume of fluid sample (∼1.2 μL), which is 16-30 times smaller than that of commercial viscometers. In addition, μVAST can be scaled up for ultra-high throughput measurements of viscosity. Here we demonstrate 16 samples within 3 seconds, which is an attractive feature for automating the process flows in drug development and materials manufacturing and production.

Consensus Statement: Hemostasis Trial Outcomes in Cardiac Surgery and Mechanical Support

BACKGROUND

Research evaluating hemostatic agents for the treatment of clinically significant bleeding has been hampered by inconsistency and lack of standardized primary clinical trial outcomes. Clinical trials of hemostatic agents in both cardiac surgery and mechanical circulatory support, such as extracorporeal membrane oxygenation and ventricular assist devices, are examples of studies that lack implementation of universally accepted outcomes.

METHODS

A subgroup of experts convened by the National Heart, Lung, and Blood Institute and the US Department of Defense developed consensus recommendations for primary outcomes in cardiac surgery and mechanical circulatory support.

RESULTS

For cardiac surgery the primary efficacy endpoint of total allogeneic blood products (units vs mL/kg for pediatric patients) administered intraoperatively and postoperatively through day 5 or hospital discharge is recommended. For mechanical circulatory support outside the perioperative period the recommended primary outcome for extracorporeal membrane oxygenation is a 5-point ordinal score of thrombosis and bleeding severity adapted from the Common Terminology Criteria for Adverse Events version 5.0. The recommended primary endpoint for ventricular assist device is freedom from disabling stroke (Common Terminology Criteria for Adverse Events AE ≥ grade 3) through day 180.

CONCLUSIONS

The proposed composite risk scores could impact the design of upcoming clinical trials and enable comparability of future investigations. Harmonizing and disseminating global consensus definitions and management guidelines can also reduce patient heterogeneity that would confound standardized primary outcomes in future research.

Plasma and Platelet Transfusions Strategies in Neonates and Children Undergoing Cardiac Surgery With Cardiopulmonary Bypass or Neonates and Children Supported by Extracorporeal Membrane Oxygenation: From the Transfusion and Anemia EXpertise Initiative-Control/Avoidance of Bleeding

OBJECTIVES

To present the recommendations and consensus statements with supporting literature for plasma and platelet transfusions in critically ill neonates and children undergoing cardiac surgery with cardiopulmonary bypass or supported by extracorporeal membrane oxygenation from the Transfusion and Anemia EXpertise Initiative-Control/Avoidance of Bleeding.

DESIGN

Systematic review and consensus conference of international, multidisciplinary experts in platelet and plasma transfusion management of critically ill children.

SETTING

Not applicable.

PATIENTS

Critically ill neonates and children following cardiopulmonary bypass or supported by extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A panel of nine experts developed evidence-based and, when evidence was insufficient, expert-based statements for plasma and platelet transfusions in critically ill neonates and children following cardiopulmonary bypass or supported by extracorporeal membrane oxygenation. These statements were reviewed and ratified by the 29 Transfusion and Anemia EXpertise Initiative-Control/Avoidance of Bleeding experts. A systematic review was conducted using MEDLINE, EMBASE, and Cochrane Library databases, from inception to December 2020. Consensus was obtained using the Research and Development/University of California, Los Angeles Appropriateness Method. Results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method. We developed one good practice statement, two recommendations, and three expert consensus statements.

CONCLUSIONS

Whereas viscoelastic testing and transfusion algorithms may be considered, in general, evidence informing indications for plasma and platelet transfusions in neonatal and pediatric patients undergoing cardiac surgery with cardiopulmonary bypass or those requiring extracorporeal membrane oxygenation support is lacking.

A droplet-based microfluidic viscometer for the measurement of blood coagulation

A continuous microfluidic viscometer is used to measure blood coagulation. The viscometer operates by flowing oil and blood into a cross section where droplets are generated. At a set pressure, the length of the droplets is inversely proportional to the viscosity of the blood sample being delivered. Because blood viscosity increases during coagulation as the blood changes from a liquid to a solid gel, the device allows to monitor coagulation by simply measuring the drop length. Experiments with swine blood were carried out in its native state and with the addition of coagulation activators and inhibitors. The microfluidic viscometer detected an earlier initiation of the coagulation process with the activator and a later initiation with the inhibitor compared to their corresponding controls. The results from the viscometer were also compared with the clinical method of thromboelastography (TEG), which was performed concurrently for the same samples. The time to initiation of coagulation in the microfluidic viscometer was correlated with the reaction time in TEG. Additionally, the total time for the measurement of clot strengthening in TEG correlated with the time for the maximum viscosity observed in the microfluidic viscometer. The microfluidic viscometer measured changes in viscosity due to coagulation faster than TEG detected the clot formation. The present viscometer is a simple technology that can be used to further study the entire coagulation process.

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.

Near-patient coagulation testing to predict bleeding after cardiac surgery: a cohort study

BACKGROUND

Coagulopathic bleeding is common after cardiac surgery and is associated with increased morbidity, mortality and healthcare costs. Implementation of blood management algorithms in which patients with severe bleeding undergo near-patient coagulation testing results in less overall bleeding and transfusion. However, it is unknown whether there is additional value from pre-emptive near-patient testing to predict whether severe bleeding will occur.

OBJECTIVES

To evaluate how well a comprehensive panel of 28 near-patient platelet and viscoelastometry tests predict bleeding after cardiac surgery, compared to prediction using baseline clinical characteristics alone.

METHODS

Single-center, prospective cohort study in adults undergoing a range of cardiac surgery procedures. The primary outcome was clinical concern about bleeding (CCB), a composite of high blood loss (chest drain volume >600 mL within 6 hours), re-operation for bleeding or administration of a pro-haemostatic treatment directed by clinician judgement.

RESULTS

In 1833 patients recruited between March 2010 and August 2012, the median number of abnormal near-patient test results was 5/28 per patient (range 0-18). CCB occurred in 449/1833 patients (24.5%). The c-statistic for a predictive model for CCB using only baseline clinical characteristics (baseline-only model) was 0.72 (95% CI 0.69-0.75). Addition of near-patient test results to this model (baseline-plus-test model) improved the prediction of CCB (c-statistic 0.75 [0.72-0.77]), but increased the number of correctly classified patients by only 18 (0.98%).

CONCLUSIONS

Near-patient coagulation testing predicts bleeding in cardiac surgery patients, but offers little improvement in prediction compared to baseline clinical characteristics alone. trial registration: ISRNCTN 20778544 (http://www.isrctn.com/).

Safety of Recombinant Human Factor XIII in a Cynomolgus Monkey Model of Extracorporeal Blood Circulation

Factor XIII (FXIII) is a thrombin-activated plasma coagulation factor critical for blood clot stabilization and longevity. Administration of exogenous FXIII to replenish depleted stores after major surgery, including cardiopulmonary bypass, may reduce bleeding complications and transfusion requirements. Thus, a model of extracorporeal circulation (ECC) was developed in adult male cynomolgus monkeys ( Macaca fascicularis) to evaluate the nonclinical safety of recombinant human FXIII (rFXIII). The hematological and coagulation profile in study animals during and after 2 h of ECC was similar to that reported for humans during and after cardiopulmonary bypass, including observations of anemia, thrombocytopenia, and activation of coagulation and platelets. Intravenous slow bolus injection of 300 U/kg (2.1 mg/kg) or 1000 U/kg (7 mg/kg) rFXIII after 2 h of ECC was well tolerated in study animals, and was associated with a dose-dependent increase in FXIII activity. No clinically significant effects in respiration, ECG, heart rate, blood pressure, body temperature, clinical chemistry, hematology (including platelet counts), or indicators of thrombosis (thrombin:antithrombin complex and D-Dimer) or platelet activation (platelet factor 4 and beta-thromboglobulin) were related to rFXIII administration. Specific examination of brain, heart, lung, liver, and kidney from rFXIII-treated animals provided no evidence of histopathological alterations suggestive of subclinical hemorrhage or thrombosis. Taken as a whole, the results demonstrate the ECC model suitably replicated the clinical presentation reported for humans during and after cardiopulmonary bypass surgery, and do not suggest significant concerns regarding use of rFXIII in replacement therapy after extracorporeal circulation.

Point-of-care platelet function testing to predict blood loss after coronary artery bypass grafting surgery: a prospective observational pilot study

Aim:

With an increase in the number of patients who are on antiplatelet medications until the day of surgery, we undertook a prospective observational study to assess the ability of thromboelastography, thromboelastography platelet mapping and aggregometry via multiplate to detect platelet dysfunction and predict blood loss following coronary artery bypass grafting (CABG) surgery.

Methods:

Platelet function was evaluated pre- and post-cardiopulmonary bypass via thromboelastography, thromboelastography platelet mapping and aggregometry via multiplate in 52 patients undergoing coronary artery bypass grafting surgery. The median chest tube drainage of all patients in the study was ascertained to stratify patients into two groups: patients with and those without evidence of excessive blood loss after cardiac surgery.

Results:

Although all modalities could detect a decrease in platelet function following cardiopulmonary bypass, univariate and multivariate regression analysis identified preoperative arachidonic acid and adenosine diphosphate testing via multiplate as independent predictors of bleeding after cardiac surgery. Receiver operating curves on these multiplate parameters showed an area under the curve of 0.68 (p=0.03) and 0.66 (p=0.01) for arachidonic acid and adenosine diphosphate assays, respectively.

Conclusion:

This pilot study shows that preoperative multiplate testing may be a better predictor of platelet dysfunction and the resultant blood loss following cardiac surgery.

Design and evaluation of a portable optical-based biosensor for testing whole blood prothrombin time

Point-of-care diagnostics (POCD) for blood coagulation benefit patients on-site, but available POCD devices are too expensive to be affordable in many countries. Optically based methodologies are cheap and reliable, and have been exploited in bench-top coagulometers to monitor coagulation with plasma, but not whole blood, which contains cellular components that cause massive interference. However, the POCD testing of whole blood gives a more accurate picture of physiological conditions than does testing plasma. In this study, a portable device for performing the prothrombin time (PT) test was designed, comprising an optical sensor, an electrical processing and control circuit to monitor the optical changes that occurred during the coagulation process in whole blood. The PT was when the slope of the first-order derivative of the coagulation curve, recorded from real-time light transmittance signals, was maximal. The POCD PT testing of 167 samples revealed that 153 (91.6%) were successfully detected and the results were highly consistent with the results of whole blood international normalized ratio (INR) (r=0.985, p<0.001) by the conventional manual method and those of plasma INR (r=0.948, p<0.001) with the ACL TOP 700 bench-top coagulometer (Beckman Colter). Hematological parameters were further analyzed, revealing that fibrinogen titers (p=0.036), red blood cell numbers (p=0.017) and distribution of red cell width (p=0.015) affected the effectiveness of the current POCD PT determination. Furthermore, a highly positive correlation was revealed between fibrinogen titers and the maximum speed of change in transmittance (v/t) (r=0.805, p<0.001), suggesting that fibrinogen might be evaluated simultaneously in this POCD testing. In conclusion, the proposed portable optical-based device performs the highly sensitive and accurate determination of whole blood PT and has commercial potential because of its small volume and low fabrication cost.

[Haemorrhage and morbidity associated with the use of tranexamic acid in cardiac surgery: a retrospective, multicentre cohort study]

INTRODUCTION

Postoperative bleeding is common complication, affecting up to 20% of patients, after cardiac bypass surgery. Fibrinolysis is one of the causes of this excessive bleeding, and for this reason the use of tranexamic acid is recommended. The problem with using this is that there are numerous guidelines and differences in the dose to be administered. Our aim was to evaluate whether there were any differences in postoperative bleeding and morbidity after cardiac surgery with the administering of different tranexamic acid doses in three university hospitals.

MATERIAL AND METHODS

A retrospective, multicentre cohort study was conducted. A total of 146 patients who were subjected to elective cardiac bypass surgery according to the anaesthetic-surgical protocol of each hospital were included in the study. The clinical histories were reviewed, and they were divided into two groups according to the tranexamic acid dose: Group A (high doses), initial dose of 20mg/kg and continuous infusion of 4 mg/kg/hour until closure of the sternotomy. A further 100mg was added to prime the bypass machine. Group B (low doses), initial dose of 10mg/kg followed by a continuous infusion of 2mg/kg/hour until closure of the sternotomy. A further 50mg was added to prime the bypass machine. Variables, such as age, sex, weight, height, type of surgical procedure (valvular, coronary or mixed), haematocrit, INR, and preoperative platelet count, time and temperature of the bypass machine, and haematocrit on sternum closure, were recorded. Among the post-operative variables collected were: debit due to drainage at 6, 12 and 24 hours after surgery, number and type of blood products transfused in the first 24 hours, need for further surgery due to haemorrhage, CVA, TIA, or a new acute myocardial infarction, convulsions, and mortality.

RESULTS

The incidence of increased bleeding (patients in the 90 percentile) was higher in Group B at all the study evaluation times (P<.05). The incidence of further surgery due to bleeding, and the need for transfusion of ≥ 3 units of packed red cells was lower in Group A (5.56%) than in Group B (13.89%). There were no significant differences in the requirements for blood products transfusions between the groups. As regards associated morbidity, there was one isolated case of convulsion and a perioperative AMI in another case in Group A, and three cases of perioperative AMI in Group B.

CONCLUSIONS

Elevated doses of tranexamic acid in cardiac bypass surgery appear to significantly reduce bleeding in the first hours after surgery compared to low doses. However, this decrease did not lead to a reduction in the needs for blood products.

Aortic valve replacement in a dialysis-dependent Jehovah's Witness: successful use of a minicircuit, microplegia, and multimodality blood conservation technique

We present the first reported case of an aortic valve replacement operation without blood transfusion in a 62-year-old Jehovah's Witness with dialysis-dependent chronic renal failure, severe anemia, severe aortic stenosis, and symptomatic angina with minimal exertion after an accident in which she suffered fractures of both her right arm and leg. She underwent successful valve replacement surgery after preoperative stabilization of her fractures and high-dose erythropoietin and iron supplement therapy preoperatively and postoperatively. The intraoperative blood conservation technique included a novel approach with a miniature cardiopulmonary bypass circuit and microplegia with limited hemodilution. High-risk valve surgery in patients who are Jehovah's Witnesses can be successful with a carefully planned multimodality blood conservation strategy.

Clinical guidelines and off-license recombinant activated factor VII: content, use, and association with patient outcomes

BACKGROUND

Recombinant activated factor VII (rFVIIa) is increasingly being used off-license for treating critical bleeding. Guidelines may therefore be useful for improving processes and outcomes. Little is known regarding guidelines for off-license rFVIIa or their association with patient outcomes.

OBJECTIVES

To investigate the availability of hospital guidelines for off-license rFVIIa use and the association between these guidelines and mortality.

METHODS

Data were extracted from the Haemostasis Registry, which collects all cases of off-license rFVIIa use in participating institutions in Australia and New Zealand. Contributing hospitals were requested to supply a copy of the institutional guideline relating to off-license rFVIIa administration. The characteristics of patients treated in accordance with all elements of the guidelines were compared with those of patients for who one or more guideline elements had been violated. The relationship between guideline-directed treatment and 28-day mortality was investigated using stepwise logistic regression.

RESULTS

Two thousand five hundred and fifty-one patients in 75 hospitals were available for analysis. Of these hospitals, 58 provided a guideline for analysis. Patients complying with all guideline elements (n = 530) did not differ from patients receiving care that violated guidelines (n = 1035) regarding age, size of dose, or gender. Guideline-directed treatment was not found to have an association with 28-day mortality following logistic regression.

CONCLUSIONS

Few patients are treated in accordance with the criteria of rFVIIa guidelines, despite their availability in the majority of hospitals. Moreover, 28-day mortality does not appear to be associated with the use of guidelines in this patient group. Refinement of guidelines relating to the off-license use of rFVIIa is therefore required.

Hemostatic and hemorrhagic problems in neurosurgical patients

BACKGROUND

Abnormalities of the hemostasis can lead to hemorrhage, and on the other hand to thrombosis. Intracranial neoplasms, complex surgical procedures, and head injury have a specific impact on coagulation and fibrinolysis. Moreover, the number of neurosurgical patients on medication (which interferes with platelet function and/or the coagulation systems) has increased over the past years.

METHOD

The objective of this review is to recall common hemostatic disorders in neurosurgical patients on the basis of the "new concept of hemostasis". Therefore the pertinent literature was searched to provide a structured and up to date manuscript about hemostasis in Neurosurgery.

FINDINGS

According to recent scientific publications abnormalities of the coagulation system are discussed. Pathophysiological background and the rational for specific (cost)-effective perioperative hemostatic therapy is provided.

CONCLUSIONS

Perturbations of hemostasis can be multifactorial and maybe encountered in the daily practice of neurosurgery. Early diagnosis and specific treatment is the prerequisite for successful treatment and good patients outcome.

Impact of genetic variation on perioperative bleeding

Variation in bleeding in the perioperative period is a complex and multifactorial event associated with immediate and delayed consequences for the patient and health care resources. Little is known about the complex genetic influences on perioperative bleeding. With the discovery of multiple variations in the human genome and ever-growing databases of well-phenotyped surgical patients, better identification of patients at risk of bleeding is becoming a reality. In this review, polymorphisms in the platelet receptor genes, plasminogen activator inhibitor, and angiotensin genes among others will be discussed. We will explore the nature, effects, and implications of the genetics that influence perioperative bleeding above and beyond surgical bleeding, particularly in cardiac surgery.

Quality assessment of platelet rich plasma during anti-platelet therapy

Platelet rich plasma (PRP) is being used with increased frequency in many surgical procedures for its known benefits of accelerated surgical wound site healing. Speculations in its efficacy in the presence of anti-platelet therapy have been proposed. To aid in defining a quality platelet rich plasma product in the presence of acetylsalicylic acid (ASA) and Plavix (clopidogrel bisulfate), we investigated three (3) groups (n = 18) of cardiac surgical patients receiving PRP. Platelet function test, platelet concentration, and quantification of growth factors (PDGF-bb and TGF-b1) were evaluated. Results showed no statistical evidence of decreased growth factors delivered to the surgical wound site in the presence of acetylsalicylic acid (ASA) and/or Plavix (clopidogrel bisulfate). Evidence in this pilot study supports the use of PRP for patients receiving Plavix and aspirin therapy without compromising the quantity of specific growth factors delivered to a wound site.

Comparison of early platelet activation in patients undergoing on-pump versus off-pump coronary artery bypass surgery

OBJECTIVE

Cardiopulmonary bypass has been shown to be associated with platelet dysfunction, which has a potential for increasing the risk of perioperative bleeding. Off-pump coronary artery bypass surgery is thought to avoid this deleterious effect of pump use on platelets. However, the influence of off-pump coronary artery bypass surgery on platelets has not been thoroughly studied.

METHODS

Accordingly, we evaluated 60 patients undergoing coronary artery bypass grafting prospectively using cardiopulmonary bypass and warm cardioplegic arrest (n = 30) or an off-pump technique (n = 30). Platelet function was evaluated before and 2 hours after coronary artery bypass grafting.

RESULTS

Among patients undergoing on-pump coronary artery bypass surgery, all studies of platelet function were significantly abnormal after surgical intervention compared with results before surgical intervention. Similarly, among patients undergoing off-pump coronary artery bypass surgery, evidence of platelet dysfunction after surgical intervention was noted, with a lower platelet count and a higher proportion of P-selectin- and Annexin V-positive platelets. However, compared with the preprocedural value, the postprocedural decrease in platelet count (78,200 x 10(3)/microL vs 103,000 x 10(3)/microL) and platelet aggregation (0.8% vs 10.9%) and increase in bleeding time (0 minutes vs +1.3 minutes), P-selectin-positive platelets (6.0% vs 9.1%), and Annexin V-positive platelets (1.7% vs 3.7%) were significantly lower in the off-pump coronary artery bypass surgery group compared with those in the on-pump coronary artery bypass surgery group, respectively.

CONCLUSIONS

Early postoperative decrease in platelet count and increase in platelet activation occurs to a much lesser extent and does not alter bleeding time or adenosine diphosphate-induced platelet aggregation in patients undergoing off-pump coronary artery bypass surgery. This lack of significant effects on platelets might in part account for the potential decreased risk in bleeding and for the preserved hemostasis seen in patients undergoing off-pump coronary artery bypass surgery compared with those undergoing on-pump coronary artery bypass grafting surgery.

Transfusion Algorithms and How They Apply to Blood Conservation: The High-risk Cardiac Surgical Patient

Considerable blood product support is administered to the cardiac surgery population. Due to the multifactorial etiology of bleeding in the cardiac bypass patient, blood products frequently and empirically are infused to correct bleeding, with varying success. Several studies have demonstrated the benefit of algorithm-guided transfusion in reducing blood loss, transfusion exposure, or rate of surgical re-exploration for bleeding. Some transfusion algorithms also incorporate laboratory-based decision points in their guidelines. Despite published success with standardized transfusion practices, generalized change in blood use has not been realized, and it is evident that current laboratory-guided hemostasis measures are inadequate to define and address the bleeding etiology in these patients.

Management of antiplatelet therapy for minimization of bleeding risk before cardiac surgery

Antiplatelet therapy is commonly administered for primary and secondary prevention of stroke, recurrent angina, myocardial infarction, and death in patients with cardiovascular disorders. It also is associated with an increased risk of bleeding. We describe the management of antiplatelet therapy in patients undergoing coronary artery bypass graft surgery. In addition, we provide basic information about the mechanisms of action by which the most common antiplatelet agents inhibit platelet function. This information is integrated with results from pharmacologic studies and clinical trials. Determining the net effect in patients undergoing coronary artery bypass graft surgery requires knowledge about the pharmacokinetics, pharmacodynamics, and clinical efficacy of each drug, and an estimation of the absolute thrombotic versus hemorrhagic risk for each patient.

The effects of a treatment protocol for cardiac surgical patients with excessive blood loss on clinical outcomes

BACKGROUND AND OBJECTIVES

Excessive blood loss (EBL) is a common complication of cardiac surgery that is associated with adverse events. The objective of this before/after study was to determine whether the implementation of a protocol for management of cardiac surgical patients with EBL was associated with improved clinical outcomes.

MATERIALS AND METHODS

In November 2002, a protocol for prompt identification and aggressive management of cardiac surgical patients with EBL was implemented at our institution. The independent relationship between protocol implementation and adverse outcomes was measured by comparing the outcomes of patients who received > or = 4 RBC (red blood cell) units within 1 day of surgery and were operated on before protocol implementation (2000-02) with those operated on after protocol implementation (2003-05), using multivariable logistic regression analysis to control for the effects of confounders. The primary outcome was a composite of adverse events that included death, renal failure, stroke, and sepsis. Bootstrapping was used to confirm the validity of the results.

RESULTS

Of the 11,314 patients who underwent surgery during the study period, 1875 (16.6%) received > or = 4 RBC units within 1 day of surgery, with 958 and 917 in the pre- and postprotocol periods, respectively. The composite adverse outcome occurred in 164 (17.1%) patients in the preprotocol period and 115 (12.5%) patients in the postprotocol period (P = 0.005). Protocol implementation was independently associated with reduced odds of the composite adverse outcome (odds ratio 0.67; 95% confidence interval 0.50, 0.91; P = 0.01). This estimate was stable in bootstrap sampling.

CONCLUSION

Implementation of a protocol to manage EBL in cardiac surgery was independently associated with improved outcomes.

Prediction of massive blood transfusion in cardiac surgery

PURPOSE

In cardiac surgery with cardiopulmonary bypass (CPB), excessive blood loss requiring the transfusion of multiple red blood cell (RBC) units is a common complication that is associated with significant morbidity and mortality. The objective of this study was to develop a prediction rule for massive blood transfusion (MBT) that could be used to optimize the management of, and research on, at-risk patients.

METHODS

Data were collected prospectively over the period from 2000 to 2005, on patients who underwent surgery with CPB at one hospital. Patients who received > or = five units of RBC within one day of surgery were classified as MBT. Logistic regression was used to appropriately select and weigh perioperative variables in the prediction rule, which was developed on the initial 60% of the sample and validated on the remaining 40%.

RESULTS

Of the 10,667 patients included, 925 (8.7%) had MBT. The clinical prediction rule included 12 variables (listed in order of predictive value: CPB duration, preoperative hemoglobin concentration, body surface area, nadir CPB hematocrit, previous sternotomy, preoperative shock, preoperative platelet count, urgency of surgery, age, surgeon, deep hypothermic circulatory arrest, and type of procedure) and was highly discriminative (c-index = 0.88). In the validation set, those classified as low-, moderate-, and high-risk by a simple risk score derived from the prediction rule had a 5%, 27%, and 58% chance of MBT, respectively.

CONCLUSION

A clinical prediction rule was developed that accurately identified patients at low-risk or high-risk for MBT. Studies are needed to determine the external generalizability and clinical utility of the prediction rule.

Point of care management of heparin administration after heart surgery

OBJECTIVES

Determination of activated partial thromboplastin time (aPTT) is used in coagulation management after heart surgery. Results from the central laboratory take long to be obtained. We sought to shorten the time to obtain coagulation results and the desired coagulation state and to reduce blood loss and transfusions using point of care (POC) aPTT determination.

DESIGN

Randomized, controlled trial.

SETTING

University-affiliated 20-bed surgical ICU.

PATIENTS AND PARTICIPANTS

Forty-two patients planned for valve surgery (Valves) and 84 for coronary artery bypass grafting (CABG) with cardiopulmonary bypass.

INTERVENTIONS

Valves and CABG were randomized to postoperative coagulation management monitored either by central laboratory aPTT (Lab group) or by POC aPTT (POC group). Heparin was administered according to guidelines.

MEASUREMENTS AND RESULTS

POC aPTT results were available earlier than Lab aPTT after venipuncture in Valves (3 +/- 2 vs. 125 +/- 68 min) and in CABG (3 +/- 4 vs. 114 +/- 62 min). Heparin was introduced earlier in the POC group in Valves (7 +/- 23 vs. 13 +/- 78 h, p = 0.01). Valves of the POC group bled significantly less than Valves in the Lab group (647 +/- 362 ml vs. 992 +/- 647 ml, p < 0.04), especially during the first 8 h after ICU admission. There was no difference in bleeding in CABG (1074 +/- 869 ml vs. 1102 +/- 620, p = NS). In Valves, fewer patients in the POC group than in the Lab group needed blood transfusions (1/21 vs. 8/21; p = 0.03). No difference was detected in CABG.

CONCLUSIONS

In Valves in the POC group the time to the desired coagulation state was reduced, as was the thoracic blood loss, reducing the number of patients transfused. This improvement was not observed in CABG. Side effects were similar in the two groups.

Platelet dysfunction during cardiopulmonary bypass assessed by a novel whole-blood aggregometer

OBJECTIVE

The purpose of this study was to assess perioperative platelet function with 2 types of monitors (a whole-blood aggregometer [WBA analyzer; Mebanix, Tokyo, Japan]) and the Sonoclot monitor [Sienco, Wheat Ridge, CO]) in patients undergoing hypothermic cardiopulmonary bypass (CPB).

DESIGN

Prospective, observational study.

SETTING

Single-center study at a university hospital.

PARTICIPANTS

Twenty-six patients who underwent coronary artery bypass grafting or valve replacement under hypothermic CPB without platelet transfusion or fresh frozen plasma administration.

INTERVENTIONS

Blood sampling was performed at the following time periods: after anesthetic induction, after CPB, and on the first postoperative day. These samples were assessed with the WBA analyzer and the Sonoclot.

MEASUREMENTS AND MAIN RESULTS

Significant attenuation of adenosine diphosphate-induced platelet aggregation was detected shortly after CPB by 2 WBA analyzer-derived parameters: a decrease in the filtration pressure rate and an increase in the platelet aggregatory threshold index. Platelet aggregation returned to the preoperative level on the next day. There was no correlation between the amount of postoperative mediastinal drainage and defects in platelet aggregation. On the other hand, time to peak obtained by the Sonoclot did not show any significant changes.

CONCLUSIONS

Whole-blood aggregation measured with the WBA analyzer detected transient platelet dysfunction shortly after CPB, whereas the Sonoclot was less sensitive to this change.

Correlation of perioperative platelet function and coagulation tests with bleeding after cardiopulmonary bypass surgery

The authors evaluated the correlation of post-cardiopulmonary bypass surgery bleeding, measured as 24-hour chest tube output/kilogram body weight, with platelet function tests using glass bead adhesion and Thrombelastograph Platelet Mapping (Haemoscope Corporation, Niles, Ill); coagulation tests; patient characteristics; surgery parameters; and visual assessment of surgical field bleeding before closure as not bleeding (code 1), oozing (code 2), and excessive bleeding (code 3). All platelet function and coagulation tests indicated significant dysfunction 15 minutes after protamine neutralization of heparin. With the exception of glass bead adherence, these assays indicated poor recovery of function 1 hour postoperatively. By multiple regression, the most significant predictors of postoperative bleeding were a low body mass index (BMI) (P < 0.0001), lowest core body temperature (P = 0.0006), and cross clamp time (P < 0.0001). Low core temperature was significantly (P < 0.0001) correlated with cross clamp time, which the authors believe is the most likely cause of coagulation and platelet dysfunction. None of the platelet function tests significantly correlated with bleeding. Looking at the highest quartile of chest tube output patients (n = 19) versus the upper and lower 50th percentile of coagulation and platelet function, bleeding could be explained for 11 patients by BMI plus surgery parameters along with coagulation and/or platelet dysfunction. In three cases without negative surgery parameters, coagulation dysfunction was observed. The remaining five cases did not give a clear indication of which parameters were primarily responsible for the bleeding.

Practical management of anticoagulation, bleeding and blood product support for cardiac surgery. Part one: bleeding and anticoagulation issues

There are many challenging problems related to bleeding and anticoagulation in cardiac surgery. Practical guidelines, which are based on available evidence, can help to direct management issues of post-bypass bleeding, perioperative anticoagulation and the use of haemostatic agents. The patient's bleeding history is the most useful preoperative screening test of haemostasis. The input of a haematologist is often valuable in a number of areas, such as preoperative assessment of patients with a significant history of bleeding, or past history of heparin-induced thrombocytopenia, a lupus anticoagulant, or recent venous thromboembolism. Cardiothoracic surgeons, anaesthetists, perfusionists and haematologists can ensure 'best practice' by being actively involved in the development of 'local' transfusion and anticoagulation guidelines, hospital transfusion committee policies, and audits.

Bleeding in Cardiac Surgery: Its Prevention and Treatment—an Evidence-Based Review

Expected and unexpected bleeding occur frequently in patients undergoing cardiac surgery. Bleeding after cardiac surgery can be broadly divided into two groups: surgical (unrecognized bleeding vessel, anastomosis, or other suture line) or nonsurgical bleeding (caused by coagulopathy). Factors influencing both surgical and nonsurgical bleeding can be further broken down into those occurring preoperatively and those that occur intraoperatively and postoperatively. A thorough understanding of these factors is necessary to reduce bleeding. This is a desirable clinical goal, because excessive bleeding is associated with adverse outcomes.

Clinical Outcomes in Cardiac Surgery: Conventional Surgery versus Bloodless Surgery

Bleeding during and after cardiac operations and the effects of cardiopulmonary bypass hemodilution commonly result in blood transfusions. Excessive microvascular bleeding can result in re-exploration and prolonged hospitalization. Nearly 20% of all blood transfusions in the United States are associated with cardiac surgery. The risks associated with the use of allogeneic blood product transfusion include mistransfusion, immunologic complications, and transmission of infectious diseases. The large demand for blood products places significant pressure on the national blood supply, resulting in frequent shortages. The variability in transfusion practice of cardiac surgery patients suggests that sound blood management and a conservative approach to this population can result in reduced transfusions without increasing morbidity or mortality and avoiding complications associated with allogeneic blood transfusion.

The effect of preoperative antiplatelet/anticoagulant prophylaxis on postoperative blood loss in cardiac surgery

In this study we sought to determine whether preoperative treatment with antiplatelet and/or anticoagulant drugs influences postoperative blood loss after coronary artery bypass graft surgery. Although prophylactic treatment to prevent ischemic events preoperatively is often necessary, the treatment frequently continues until there may be a risk of increased bleeding (i.e., within 5-7 days before surgery). With patient consent, a preincision blood sample was collected prospectively from 93 adult subjects who presented randomly. They consisted of 3 groups regarding their primary preoperative regimen: 1) no preoperative treatment within the week before surgery; 2) platelet adenosine diphosphate (ADP) receptor antagonist; 3) ADP receptor antagonist plus IV heparin. Postoperative chest tube drainage (24 h) in the group that received ADP antagonist alone was more (P < 0.05) than either of the other groups: 503 +/- 56; 633 +/- 55; 439 +/- 29 mL (mean +/- SEM) for Groups 1, 2, and 3, respectively. Combined treatment with ADP antagonist plus heparin infusion appeared to prevent the increased blood loss with the ADP antagonist alone. Preincision and postoperative plasma fibrinogen concentrations were largest (P < 0.05) in the group that received the combination treatment; mean +/- SEM for groups 1, 2, and 3 preincision, 311 +/- 17, 366 +/- 16, and 423 +/- 18 mg/dL, and postoperatively, 229 +/- 16, 267 +/- 13, and 312 +/- 16 mg/dL. Postoperative fibrinogen showed strong dependence on preoperative fibrinogen in all groups (r = 0.576 to 0.825; P = 0.01 to 10(-6)). Prevention of the increased blood loss in the ADP receptor antagonist group by the addition of a heparin infusion may have been attributable to a conservation of coagulation factors, as evidenced by the increased plasma fibrinogen concentrations with combined prophylactic treatment.

IMPLICATIONS

The objective of this study was to determine whether preoperative treatment with antiplatelet and/or anticoagulant drugs influences the extent of blood loss in the 24-h period after cardiac surgery.

Point-of-Care Testing of Hemostasis in Cardiac Surgery

An excessive perioperative blood loss, that requires transfusion of blood products, sometimes occurs in patients undergoing cardiopulmonary bypass for cardiac surgery. Blood loss and transfusion requirements in these patients may be reduced with a better control of heparin treatment and its reversal. Blood component administration in patients with excessive post-cardiopulmonary bypass bleeding has been empiric for a long time due to turnaround times of laboratory coagulation tests. Devices are now available for rapid, point-of-care assessment of hemostasis alterations to allow an appropriate, targeted therapy. In particular, a quick evaluation of platelet and coagulation defects with new point-of-care devices can optimize the administration of pharmacological and transfusion-based therapy in patients with excessive bleeding after cardiopulmonary bypass.

Intra-operative autologous blood management

The evolution of cardiac surgery has been accompanied by a wide variety of techniques and equipment available for blood conservation. It has also given us data that allows identification of preoperative risk factors for transfusion needs in other surgical specialties. There is however great diversity of opinion as to how this technology should be applied. Examples can be found in the literature of discrepancies between countries but also individual institutions . The authors encounter differences in opinion between practitioners regularly. The authors believe that the variance in opinion may be based on the experiences of single techniques and that a broader depth of practice is required to achieve best practices for intra-operative transfusion management. The most performed procedure in our experience is red cell salvage and processing with a cell-washing device (CS). There are two primary issues related to CS, cost and reduction in allogenic blood exposure. A recent meta-analysis has shown that cell salvage in orthopedic surgery decreases the proportion of patients requiring allogeneic blood transfusion peri-operatively, but post-operative cell salvage is only marginally effective in cardiac surgery. There are close analogies to be drawn from issues surrounding the whole picture of transfusion. Medical practice guidelines are frequently promoted as a way to improve the cost-effectiveness of healthcare. But non-compliance with guidelines is still a major issue. Guiding the decision to transfuse or autotransfuse can improve transfusion practices, but effective processes must first identify problem(s) in transfusion practice and then include the attending medical practitioner as an educational target. Process improvements that have been shown to be effective include, briefly meeting one-on-one with physicians, teaching at scheduled conferences, making daily clinical rounds of patients who receive transfusion, concurrently reviewing orders for transfusion before issue of the blood product, and installing algorithms and guidelines in the operating room. Transfusion practices improved with these process improvements. The success of a change of practice patterns relies on hospital administration, education and feedback, written and immediately available guidelines, employment of specially trained personnel, and establishing long-standing actions. It is the authors' observation that the success of an intra-operation blood management program is twofold, early identification of patients and a multi-team approach of Surgeon, Haematologist, Transfusion services, Anaesthetist and Perfusionist. This team approach offers far greater depth for management of intra-operative blood conservation and transfusion practice. Interventions must be patient specific and targeted toward the best possible patients outcome.

An effective treatment of severe intractable bleeding after valve repair by one single dose of activated recombinant factor VII

IMPLICATIONS

The successful treatment with recombinant factor VIIa of a patient experiencing intractable bleeding after cardiac surgery is described.