Platelet activation and aggregation during cardiopulmonary bypass

Supplemental fibrinogen restores thrombus formation in cardiopulmonary bypass-induced platelet dysfunction ex vivo

BACKGROUND

Major cardiac surgery related blood loss is associated with increased postoperative morbidity and mortality. Platelet dysfunction is believed to contribute to post-cardiopulmonary bypass (CPB)-induced microvascular bleeding. We hypothesised that moderately hypothermic CPB induces platelet dysfunction and that supplemental fibrinogen can restore in vitro thrombus formation.

METHODS

Blood from 18 patients, undergoing first-time elective isolated aortic valve surgery was drawn before CPB, 30 min after initiation of CPB, and after CPB and protamine administration, respectively. Platelet aggregation was quantified by optical aggregometry, platelet activation by flow-cytometric detection of platelet surface expression of P-selectin, annexin V, and activated glycoprotein IIb/IIIa, thrombus formation under flow and effect of supplemental fibrinogen (4 mg ml-1) on in vitro thrombogenesis.

RESULTS

Post-CPB adenosine-diphosphate and TRAP-6-induced aggregation decreased by 40% and 10% of pre-CPB levels, respectively (P<0.0001). Although CPB did not change glycoprotein IIb/IIIa receptor expression, it increased the percentage of unstimulated P-selectin (1.2% vs 7%, P<0.01) positive cells and annexin V mean fluorescence intensity (15.5 vs 17.2, P<0.05), but decreased percentage of stimulated P-selectin (52% vs 26%, P<0.01) positive cells and annexin V mean fluorescence intensity (508 vs 325, P<0.05). Thrombus area decreased from 6820 before CPB to 5230 after CPB (P<0.05, arbitrary units [a.u.]). Supplemental fibrinogen increased thrombus formation to 20 324 and 11 367 a.u. before CPB and after CPB, respectively (P<0.001), thereby restoring post-CPB thrombus area to levels comparable with or higher than pre-CPB baseline.

CONCLUSIONS

Single valve surgery using moderately hypothermic CPB induces partial platelet dysfunction. Thrombus formation was restored in an experimental study design by ex vivo supplementation of fibrinogen.

Association of serum PCSK9 levels with platelet function in patients with acute coronary syndromes

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates low-density lipoprotein (LDL) homeostasis and plays a key role in acute coronary syndrome (ACS). The cardioprotective effect of PCSK9 inhibition extends beyond LDL cholesterol reduction, involving regulation of platelet function by not yet unraveled mechanisms. Oxidized-LDL (ox-LDL) is increased during ACS and induces platelet activation via binding to platelet surface. We will evaluate serum PCSK9 and its correlation with platelet reactivity and platelet-ox-LDL binding in Chinese ACS patients.

METHOD AND DESIGN

In this pilot cross-sectional study, we will enroll 115 Chinese participants aged 30 to 75 years with ACS. Blood sample will be obtained after the first maintenance dose of aspirin and clopidogrel during morning time. Serum PCSK9 will be measured by an enzyme-linked immunoadsorbent assay. Platelet reactivity will be assessed by; Platelet activation (P-selectin and GPIIbIIIa expression using flow cytometry) and; Platelet aggregation using light transmission aggregometry in response to various stimuli. On-treatment platelet reactivity is measured by adenosine diphosphate-induced platelet aggregation. Binding of ox-LDL to platelet will be evaluated by flow cytometry. Spearman correlations will be used to determine association of serum PCSK9 with platelet functional parameters and platelet-ox-LDL binding. Additionally, continuous PCSK9 levels will be categorized into tertiles of equal size to investigate its association with on-treatment platelet reactivity.

DISCUSSION

This study will reveal possible relationship between serum PCSK9 and platelet reactivity in the setting of ACS which may shed light on therapeutic potential in platelet inhibition by targeting PCSK9. The study will also explore the association of serum PCSK9 and platelet-ox-LDL binding, an important mechanism for platelet-LDL interplay, to provide mechanistic insight into PCSK9-mediated regulation of platelet reactivity.

Platelet Function is Preserved After Moderate Cardiopulmonary Bypass Times But Transiently Impaired After Protamine

OBJECTIVES

Previous studies have described impaired platelet function after cardiopulmonary bypass (CPB). Whether this is still valid in contemporary cardiac surgery is unclear. This study aimed to quantify changes in function and number of platelets during CPB in a present-day cardiac surgery cohort.

DESIGN

Prospective, controlled clinical study.

SETTING

A single-center university hospital.

PARTICIPANTS

Thirty-nine patients scheduled for coronary artery bypass graft surgery with CPB.

INTERVENTIONS

Platelet function and numbers were measured at 6 timepoints in 39 patients during and after coronary artery bypass graft surgery; at baseline before anesthesia, at the end of CPB, after protamine administration, at intensive care unit (ICU) arrival, 3 hours after ICU arrival, and on the morning after surgery.

MEASUREMENTS AND MAIN RESULTS

Platelet function was assessed with impedance aggregometry and flow cytometry. Platelet numbers are expressed as actual concentration and as numbers corrected for dilution using hemoglobin as a reference marker. There was no consistent impairment of platelet function during CPB with either impedance aggregometry or flow cytometry. After protamine administration, a decrease in platelet function was seen with impedance aggregometry and for some markers of activation with flow cytometry. Platelet function was restored 3 hours after arrival in the ICU. During CPB (85.0 ± 21 min), the number of circulating platelets corrected for dilution increased from 1.73 ± 0.42 × 10⁹/g to 1.91 ± 0.51 × 10⁹/g (p < 0.001).

CONCLUSIONS

During cardiac surgery with moderate CPB times, platelet function was not impaired, and no consumption of circulating platelets could be detected. Administration of protamine transiently affected platelet function.

Reoperation for bleeding after cardiac surgery

BACKGROUND

Postoperative cardio-surgical haemostatic management is centre-specific and experience-based, which leads to a variability in patient care. This study aimed to identify which postoperative haemostatic interventions may reduce the need for reoperation after cardiac surgery in adults.

METHODS

A retrospective case-control study in a tertiary centre. Adult, elective, primary cardiac surgical patients were selected (n = 2098); cases (n = 42) were patients who underwent reoperation within 72 h after the initial surgery. Interventions administered to control surgical bleeding were compared for the need to re-operate using multiple logistic regression.

RESULTS

Rate of cardiac surgical reoperation was 2% in the study population. Three variables were found to be associated with cardiac reoperation: preoperative administration of fresh frozen plasma (OR 5.45, CI 2.34-12.35), cumulative volume of chest tube drainage and cumulative count of packed red blood cells transfusion on ICU (OR 1.98, CI 1.56-2.51).

CONCLUSION

No significant difference among specific types of postoperative haemostatic interventions was found between patients who needed reoperation and those who did not. Perioperative transfusion of fresh frozen plasma, postoperative transfusion of packed cells and cumulative volume of chest tube drainage were associated with reoperation after cardiac surgery. These variables could help predict the need for reoperation.

Platelet Function Test in Coronary Artery Bypass Grafting: Does It Predict Postoperative Bleeding?

Background Patients undergoing on-pump coronary artery bypass grafting (CABG) are at increased risk of perioperative bleeding and morbidity associated with transfusion as a result of acquired and pharmacologically induced impaired platelet function.

Settings and Design In this a prospective observational study where 52 patients underwent on-pump CABG were analyzed with ROTEM platelet aggregometry.

Materials and Methods Patients were assigned to the “nonexcessive” and “excessive” postoperative bleeding groups according to the postoperative chest tube drainage over 24 hours. Platelet function was assessed by ROTEM platelet using three different activators (arachidonic acid, adenosine diphosphate, and thrombin receptor-activating peptide), at two perioperative time points (T1, before heparinization and T2, 5–10 minutes after protamine administration).

Results There were no differences regarding demographic, pre–cardiopulmonary bypass (CPB) platelet count and antiplatelet therapy. Platelet function was impaired over the time course in all parameters with three different activators. At T2 point, area under the curve (AUC) of all the three platelet indices, that is, TRAPTEM, ARATEM, and ADPTEM, showed significant difference between excessive and nonexcessive groups. At both T1 and T2 points, the amplitude after 6 minutes (A6) and maximum slope (MS) parameters of TRAPTEM, ARATEM, and ADPTEM tests were not significantly different in excessive and nonexcessive groups. At T1 point, AUC was also not significantly different in all three ROTEM platelet tests. Results after protamine administration showed correlation with postoperative chest tube drainage. Cut-off values, as determined by receiver operating characteristics (ROC) analyses, had a consistently weak positive predictive value for all tests at T2 time point, whereas negative predictive values were higher.

Conclusion Platelet function analysis using ROTEM platelet can help to exclude platelet dysfunction as the reason for bleeding after cardiac surgery. Point-of-care platelet function analysis, particularly in combination with viscoelastic testing can reduce perioperative bleeding and transfusion requirements, as well as improve patient outcomes in cardiac surgery.

Renal and Cerebral Hypoxia and Inflammation During Cardiopulmonary Bypass

Cardiac surgery-associated acute kidney injury and brain injury remain common despite ongoing efforts to improve both the equipment and procedures deployed during cardiopulmonary bypass (CPB). The pathophysiology of injury of the kidney and brain during CPB is not completely understood. Nevertheless, renal (particularly in the medulla) and cerebral hypoxia and inflammation likely play critical roles. Multiple practical factors, including depth and mode of anesthesia, hemodilution, pump flow, and arterial pressure can influence oxygenation of the brain and kidney during CPB. Critically, these factors may have differential effects on these two vital organs. Systemic inflammatory pathways are activated during CPB through activation of the complement system, coagulation pathways, leukocytes, and the release of inflammatory cytokines. Local inflammation in the brain and kidney may be aggravated by ischemia (and thus hypoxia) and reperfusion (and thus oxidative stress) and activation of resident and infiltrating inflammatory cells. Various strategies, including manipulating perfusion conditions and administration of pharmacotherapies, could potentially be deployed to avoid or attenuate hypoxia and inflammation during CPB. Regarding manipulating perfusion conditions, based on experimental and clinical data, increasing standard pump flow and arterial pressure during CPB appears to offer the best hope to avoid hypoxia and injury, at least in the kidney. Pharmacological approaches, including use of anti-inflammatory agents such as dexmedetomidine and erythropoietin, have shown promise in preclinical models but have not been adequately tested in human trials. However, evidence for beneficial effects of corticosteroids on renal and neurological outcomes is lacking. © 2021 American Physiological Society. Compr Physiol 11:1-36, 2021.

Role of Platelet Function Test in Predicting Postoperative Bleeding Risk after Coronary Artery Bypass Grafting: A Prospective Observational Study

Patients undergoing cardiac surgery are at risk of excessive bleeding and its associated complications. Excessive bleeding during and after cardiac surgery has an incidence of ~20%. Massive bleeding and subsequent requirement for blood product administration and mediastinal reexploration are associated with significant morbidity and mortality. Postoperative, nonsurgical bleeding in cardiac surgical patients is often multifactorial. Platelet dysfunction, excessive fibrinolysis, hypothermia, preoperative anemia, and deficiency of coagulation factors or their dilution are all suggested etiologies of postoperative bleeding. In the Arachidonic Acid Thromboelastometry (ARATEM) test, platelets are activated with arachidonic acid; in Adenosine diphosphate Thromboelastometry (ADPTEM) test, platelets are activated with adenosine diphosphate; and in TRAPTEM test, platelets are activated with thrombin receptor-activating peptide 6. Measurement time is 6 minutes, and results are expressed in three different parameters: A6 (amplitude at 6 minutes, in Ohm); MS (maximum slope of the aggregation curve in Ohm/min), and AUC (area under the curve in Ohm.min). Algorithm-based point-of-care platelet function testing helped us to preemptively give the right blood component therapy, avoiding fibrinolytic bleeding in the postoperative period.

Effects of remote ischemic preconditioning on platelet activation and reactivity in patients undergoing cardiac surgery using cardiopulmonary bypass: a randomized controlled trial

During cardiopulmonary bypass (CPB), platelet activation and dysfunction are associated with adverse outcomes. Remote ischemic preconditioning (RIPC) has been shown to attenuate platelet activation. We evaluated the effects of RIPC on platelet activation during CPB in patients undergoing cardiac surgery. Among 58 randomized patients, 26 in the RIPC group and 28 in the sham-RIPC group were analyzed. RIPC consisted of 4 cycles of 5-min ischemia induced by inflation of pneumatic cuff pressure to 200 mmHg, followed by 5-min reperfusion comprising deflation of the cuff on the upper arm. Platelet activation was assessed using flow cytometry analysis of platelet activation markers. The primary endpoint was the AUC of CD62P expression during the first 3 h after initiation of CPB. Secondary outcomes were the AUC of PAC-1 expression and monocyte-platelet aggregates (MPA) during 3 h of CPB. The AUCs of CD62P expression during 3 h after initiation of CPB were 219.4 ± 43.9 and 211.0 ± 41.2 MFI in the RIPC and sham-RIPC groups, respectively (mean difference, 8.42; 95% CI, -14.8 and 31.7 MFI; p =.471). The AUCs of PAC-1 expression and MPA did not differ between groups. RIPC did not alter platelet activation and reactivity during CPB in patients undergoing cardiac surgery.

Changes in MicroRNA Expression Level of Circulating Platelets Contribute to Platelet Defect After Cardiopulmonary Bypass

OBJECTIVES

Platelet defect mechanisms after cardiopulmonary bypass remain unclear. Our hypothesis microRNA expressions in circulating platelets significantly change between pre and post cardiopulmonary bypass, and consequent messenger RNA and protein expression level alterations cause postcardiopulmonary bypass platelet defect.

DESIGN

Single-center prospective observational study.

SETTING

Operating room of Kyoto Prefectural University of Medicine.

PATIENTS

Twenty-five adult patients scheduled for elective cardiac surgeries under cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In the initial phase, changes in microRNA expression between pre and post cardiopulmonary bypass underwent next generation sequencing analysis (10 patients). Based on the results, we focused on changes in mir-10b and mir-96, which regulate glycoprotein 1b and vesicle-associated membrane protein 8, respectively, and followed them until messenger RNA and protein syntheses (15 patients) using quantitative polymerase chain reaction and Western blotting. Seven microRNAs including mir-10b and mir-96 exhibited significant differences in the initial phase. In the subsequent phase, mir-10b-5p and mir-96-5p overexpressions were confirmed, and glycoprotein 1b and vesicle-associated membrane protein 8 messenger RNA levels were significantly decreased after cardiopulmonary bypass: fold differences (95% CI): mir-10b-5p: 1.35 (1.05-2.85), p value equals to 0.01; mir-96-5p: 1.59 (1.06-2.13), p value equals to 0.03; glycoprotein 1b messenger RNA: 0.46 (0.32-0.60), p value of less than 0.001; and vesicle-associated membrane protein messenger RNA: 0.70 (0.56-0.84), p value of less than 0.001. Glycoprotein 1b and vesicle-associated membrane protein 8 were also significantly decreased after cardiopulmonary bypass: glycoprotein 1b: 82.6% (71.3-93.8%), p value equals to 0.005; vesicle-associated membrane protein 8: 79.0% (70.7-82.3%), p value of less than 0.001.

CONCLUSIONS

Expressions of several microRNAs in circulating platelets significantly changed between pre and post cardiopulmonary bypass. Overexpressions of mir-10b and mir-96 decreased glycoprotein 1b and vesicle-associated membrane protein 8 messenger RNA as well as protein, possibly causing platelet defect after cardiopulmonary bypass.

Changes in platelet Bax levels contribute to impaired platelet response to thrombin after cardiopulmonary bypass: prospective observational clinical and laboratory investigations

Background

Anucleate platelets can undergo apoptosis in response to various stimuli, as do nucleated cells. Cardiopulmonary bypass (CPB) causes platelet dysfunction and can also activate platelet apoptotic pathways. We therefore evaluated time-dependent changes in blood platelet Bax (a pro-apoptotic molecule) levels and platelet dysfunction after cardiac surgery.

Methods

We assessed blood samples obtained from subjects having on-pump or off-pump coronary artery bypass graft surgery ( n =20 each). We also evaluated the in vitro effects of platelet Bax increase in eight healthy volunteers.

Results

Thrombin-induced platelet calcium mobilisation and platelet-surface glycoprotein Ib (GPIb) expression were lowest at weaning from CPB and did not recover on postoperative day one. On-pump surgery increased platelet expression of Bax, especially the oligomerised form, along with translocation of Bax from the cytosol to mitochondria and platelet-surface tumour necrosis factor-alpha (TNF-α)-converting enzyme (TACE) expression. In contrast, mitochondrial cytochrome c expression was reduced. While similar in direction, the magnitude of the observed changes was smaller in patients having off-pump surgery. In vitro , a cell-permeable Bax peptide increased platelet Bax expression to the same extent seen during bypass and produced similar platelet changes. These apoptotic-like changes were largely reversed by Bcl-xL pre-administration, and were completely reversed by combined application of inhibitors that stabilise outer mitochondrial membrane permeability and TACE.

Conclusions

CPB increases platelet Bax expression, which contributes to reduced platelet-surface GPIb expression and thrombin-induced platelet calcium changes. These changes in platelet apoptotic signalling might contribute to platelet dysfunction after CPB.

Clinical trial registration

UMIN Clinical Trials Registry (number UMIN000006033).

The association between platelet dysfunction and adverse outcomes in cardiac surgical patients

Haemostatic activation during cardiopulmonary bypass is associated with prothrombotic complications. Although it is not possible to detect and quantify haemostatic activation directly, platelet dysfunction, as measured with point-of-care-assays, may be a useful surrogate. In this study, we assessed the association between cardiopulmonary bypass-associated platelet dysfunction and adverse outcomes in 3010 cardiac surgical patients. Platelet dysfunction, as measured near the end of the rewarming phase of cardiopulmonary bypass, was calculated as the proportion of non-functional platelets after activation with collagen. Logistic regression and multivariable analyses were applied to assess the relationship between platelet dysfunction and a composite of in-hospital death; myocardial infarction; stroke; deep vein thrombosis or pulmonary embolism; and acute kidney injury (greater than a two-fold increase in creatinine). The outcome occurred in 251 (8%) of 3010 patients. The median (IQR [range]) percentage platelet dysfunction was less for those without the outcome as compared with those with the outcome; 14% (8-28% [1-99%]) vs. 19% (11-45% [2-98%]), p < 0.001. After risk adjustment, platelet dysfunction was independently associated with the composite outcome (p < 0.001), such that for each 1% increase in platelet dysfunction there was an approximately 1% increase in the composite outcome (OR 1.012; 95%CI 1.006-1.018). This exploratory study suggests that cardiopulmonary bypass-associated platelet dysfunction has prognostic value and may be a useful clinical measure of haemostatic activation in cardiac surgery.

Perioperative point of care platelet function testing and postoperative blood loss in high-risk cardiac surgery patients

Postoperative coagulopathic bleeding is common in cardiac surgery and associated with increased morbidity and mortality. Platelet function is affected by multiple factors, including patient and procedural characteristics. Point-of-care (POC) multiple electrode aggregometry (MEA) can rapidly detect and quantify platelet dysfunction and could contribute to optimal patient blood management. In patients undergoing CABG and heart valve surgery platelet function was assessed using POC MEA at four different perioperative timepoints in response to stimulation with four specific receptor agonists (ADP, AA, COL, TRAP). Postoperative bleeding was recorded during 24 h after surgery. Regression analyses were performed to establish associations between perioperative platelet function and postoperative blood loss. Ninety-nine patients were included in the study. Fifty-nine patients (60%) were on antiplatelet therapy (APT) at time of surgery. ADP- and AA-induced platelet aggregation declined during CPB and after decannulation from CPB, with a maximum decrease of 55% for ADP (35 vs. 77 AU at baseline; P < 0.001) and 78% for ASPI (14 vs. 64 AU at baseline; P < 0.001). A linear relationship was present between ADP-induced platelet aggregometry at baseline and postoperative blood loss (r = -0.249; P = 0.015). In aspirin users, the maximum decline in platelet function between baseline and CPB decannulation was related to postoperative blood loss (r = 0.308; P = 0.037). In multivariate analysis, a reduced ADP platelet function prior to surgery remained associated with postoperative blood loss (r = -0.239; P = 0.012). Reduced ADP-induced platelet aggregation at baseline is associated with increased postoperative blood loss in high-risk cardiac surgery patients.

Endotoxin Removal from Whole Blood by a Novel Adsorption Resin: Efficiency and Hemocompatibility

The structural component of Gram- bacteria, endotoxin (ET), induces the release of endogenous mediators of sepsis. Attempts to remove these downstream molecules in vivo, have not improved survival. However, extracorporeal strategies such as continuous renal replacement therapy or therapeutic plasmapheresis have shown benefit. We are presenting an affinity-based extracorporeal technology for the removal of ET from whole blood. The small-scale device contains an adsorbent that removed 75% of ET present in whole blood. This affinity resin displayed good hemocompatibility regarding the coagulation pathway. Minimal platelet, neutrophil and complement activation were observed. There was also no evidence of consumption of coagulation factors or cell loss. In as much as ET participates in both the inflammatory and coagulation abnormalities in sepsis, this method represents an efficient and hemocompatible way to remove ET from whole blood, which, in an extracorporeal setting, may improve the outcome of sepsis.

The β-d-Endoglucuronidase Heparanase Is a Danger Molecule That Drives Systemic Inflammation and Correlates with Clinical Course after Open and Endovascular Thoracoabdominal Aortic Aneurysm Repair: Lessons Learnt from Mice and Men

Thoracoabdominal aortic aneurysm (TAAA) is a highly lethal disorder requiring open or endovascular TAAA repair, both of which are rare, but extensive and complex surgical procedures associated with a significant systemic inflammatory response and high post-operative morbidity and mortality. Heparanase is a β-d-endoglucuronidase that remodels the endothelial glycocalyx by degrading heparan sulfate in many diseases/conditions associated with systemic inflammation including sepsis, trauma, and major surgery. We hypothesized that (a) perioperative serum levels of heparanase and heparan sulfate are associated with the clinical course after open or endovascular TAAA repair and (b) induce a systemic inflammatory response and renal injury/dysfunction in mice. Using a reverse-translational approach, we assessed (a) the serum levels of heparanase, heparan sulfate, and the heparan sulfate proteoglycan syndecan-1 preoperatively as well as 6 and 72 h after intensive care unit (ICU) admission in patients undergoing open or endovascular TAAA repair and (b) laboratory and clinical parameters and 90-day survival, and (c) the systemic inflammatory response and renal injury/dysfunction induced by heparanase and heparan sulfate in mice. When compared to preoperative values, the serum levels of heparanase, heparan sulfate, and syndecan-1 significantly transiently increased within 6 h of ICU admission and returned to normal within 72 h after ICU admission. The kinetics of any observed changes in heparanase, heparan sulfate, or syndecan-1 levels, however, did not differ between open and endovascular TAAA-repair. Postoperative heparanase levels positively correlated with noradrenalin dose at 12 h after ICU admission and showed a high predictive value of vasopressor requirements within the first 24 h. Postoperative heparan sulfate showed a strong positive correlation with interleukin-6 levels day 0, 1, and 2 post-ICU admission and a strong negative correlation with lactate clearance during the first 6 h post-ICU admission. Moreover, systemic administration of heparanase and heparan sulfate induced an inflammatory response and a small degree of renal dysfunction in mice. In conclusion, these results suggest that heparanase and heparan sulfate exhibit a substantial role as clinically relevant danger molecules and may serve as both, promising biomarkers and therapeutic targets in patients undergoing open or endovascular TAAA repair and, indeed, other conditions associated with significant systemic inflammation.

Changes in platelet function independent of pharmacotherapy following coronary intervention in non-ST-elevation myocardial infarction patients

BACKGROUND

High on treatment platelet reactivity (HTPR) is common in patients receiving clopidogrel following an acute coronary syndrome (ACS); it's also associated with increased morbidity and mortality. More potent and predictable antiplatelet drugs have addressed this issue at the expense of increased bleeding. Identification of HTPR and the targeted use of more potent antiplatelet drugs has, so far, broadly failed. We investigate this approach in terms of the timing of platelet function testing and how this can impact on the ability of these bedside tests to predict HTPR around the time of coronary intervention.

METHODS

High risk ACS patients treated with 5 days of clopidogrel had platelet function assessed using the multiple electrode aggregometry system (MEA) pre, post and 24 h following percutaneous coronary intervention (PCI). Simultaneous detailed analysis of platelet status was undertaken with quantification of platelet bound and soluble p-selectin and mass spectrometry quantification of the eicosanoid 12-HETE.

RESULTS

As assessed by MEA 40.5% of patients had HTPR pre-PCI; mean aggregation units (AU) in response to ADP were 499.1 ± 46.3 pre-PCI, 407.6 ± 37.7 post-PCI and 269.1 ± 24.6 AU 24 h post-PCI (pre to post PCI p > 0.05, pre to 24 h post-PCI p = 0.0002). This highly significant drop in platelet reactivity was contrasted with on-going expression of platelet bound p-selectin, increased soluble p-selectin and rising 12-HETE concentrations.

CONCLUSIONS

This study outlines significant changes in ex-vivo platelet aggregation that occur within 24 h of PCI in high risk NSTEMI patients using bedside PFT. Whilst there were no changes in antiplatelet therapy during the study period its clear that timing is crucial when assessing high on treatment residual platelet activity.

The role of point-of-care platelet function testing in predicting postoperative bleeding following cardiac surgery: a systematic review and meta-analysis

This systematic review and meta-analysis appraises the utility of point-of-care platelet function tests for predicting blood loss and transfusion requirements in cardiac surgical patients, and analyses whether their use within a transfusion management algorithm is associated with improved patient outcomes. We included 30 observational studies incorporating 3044 patients in the qualitative assessment, and nine randomised controlled trials including 1057 patients in the meta-analysis. Platelet function tests demonstrated significant variability in their ability to predict blood loss and transfusion requirements. Their use within a blood transfusion algorithm demonstrated a reduction in blood loss at longest follow-up (mean difference -102.9 ml (95% CI -149.9 to -56.1 ml), p < 0.001), and transfusion of packed red cells (RR 0.86 (95% CI 0.78-0.94), p = 0.001) and fresh frozen plasma (RR 0.42 (95% CI 0.30-0.59), p < 0.001). Viscoelastic methods used in combination with other platelet function tests achieved greater reduction in blood loss (mean difference -111.8 ml (95% CI -174.9 to -49.1 ml), p = 0.0005) compared with their use alone (mean difference -90.6 ml (95% CI 166.1-15.0 ml), p = 0.02). We conclude that incorporation of point-of-care platelet function tests into transfusion management algorithms is associated with a reduction in blood loss and transfusion requirements in cardiac surgery patients.

A 2014 Update on Coagulation Management for Cardiopulmonary Bypass

Coagulopathy after cardiac surgery with cardiopulmonary bypass is a serious complication that may result in massive bleeding requiring transfusion of significant amounts of blood products, plasma, and platelets. In addition to increased patient morbidity and mortality it is associated with longer hospital stay and increased resource utilization. The current review discusses aspects in cardiopulmonary bypass–induced coagulopathy with emphasis on point-of-care testing and individualized “goal-directed” therapy in patients who develop excessive bleeding after cardiac surgery.

Open aortic valve replacement in a patient with Glanzmann's thrombasthenia: a multidisciplinary strategy to minimize perioperative bleeding

BACKGROUND

Glanzmann thrombasthenia (GT) is an autosomal recessive disorder in which the platelet (PLT) glycoprotein IIb/IIIa complex is either deficient or dysfunctional. In its most severe form, GT may result in spontaneous bleeding, although most cases are first detected in the setting of an invasive procedure.

CASE REPORT

A 59-year-old male with Type I GT and a history of transfusion reactions to PLT infusions developed severe aortic stenosis secondary to bicuspid valve disease. He successfully underwent open aortic valve replacement with cardiopulmonary bypass without perioperative bleeding complications.

RESULTS

A multidisciplinary team (anesthesia, hematology, cardiac surgery, and transfusion medicine) was established to optimize perioperative hematologic management. Bleeding risk was assessed given the patient's prior history and a dosing timeline for administration of blood products and recombinant clotting factors was established. Successful management was achieved during the operation by prophylactic administration of HLA-matched PLTs and Factor VIIa. Prophylactic PLT administration was continued through the immediate postoperative period and no bleeding complications occurred. Thromboelastograms (TEGs) were used in conjunction with traditional hematologic laboratory analysis to optimize clinical management.

CONCLUSION

Patients with GT requiring cardiac surgical procedures are at high risk for perioperative bleeding complications. This case report illustrates the importance of multidisciplinary planning, TEG analysis, and the judicious use of recombinant factors to minimize operative bleeding risk.

Decreasing the need for transfusion: infant cardiac surgery using hemodilution and recombinant factor VIIa

Many strategies, including intraoperative acute normovolemic hemodilution (ANH) and pharmacologic agents, exist to minimize the use of allogeneic blood products in pediatric congenital heart surgery. Recombinant activated factor VIIa (rFVIIa) is a hemostatic agent approved for the treatment of bleeding episodes and prevention of bleeding in surgical interventions in patients with hemophilia A or B with inhibitors, acquired hemophilia, or congenital factor VII deficiency. Off-label use in nonhemophilic patients for uncontrolled hemorrhage is increasing although still under investigation. We present our experience with ANH and rFVIIa in nine patients. All were <16 months of age and underwent complex cardiac surgery with the end point of achieving hemostasis while decreasing or eliminating the need for allogeneic blood products. Clinically, we have observed rapid hemostasis in patients who underwent ANH and then had autologous blood reinfused after cardiopulmonary bypass, along with rFVIIa, without any time delay. The patients required no allogeneic blood products and therefore results suggested the potential utility of this practice. The study group consisted of nine patients <16 months of age who received rFVIIa in the operating room after open-heart surgery. Amount of autologous blood removed preoperatively, blood product use, time from protamine to rFVIIa administration, platelet count, INR, and fibrinogen level were retrospectively obtained. Of the nine patients, the three who underwent the most aggressive hemodilution received rFVIIa most rapidly and required no allogeneic blood products to achieve hemostasis although they had an average lower fibrinogen level on admission to the cardiothoracic intensive care unit. These preliminary data suggest that hemodilution before surgical stimulation and the rapid administration of rFVIIa, along with the reintroduction of autologous blood, may decrease or potentially eliminate the need for allogeneic blood products. Prospective trials are warranted to further explore this technique.

Combined blockade of ADP receptors and PI3-kinase p110β fully prevents platelet and leukocyte activation during hypothermic extracorporeal circulation

Extracorporeal circulation (ECC) and hypothermia are used to maintain stable circulatory parameters and improve the ischemia tolerance of patients in cardiac surgery. However, ECC and hypothermia induce activation mechanisms in platelets and leukocytes, which are mediated by the platelet agonist ADP and the phosphoinositide-3-kinase (PI3K) p110β. Under clinical conditions these processes are associated with life-threatening complications including thromboembolism and inflammation. This study analyzes effects of ADP receptor P₂Y₁₂ and P₂Y₁ blockade and PI3K p110β inhibition on platelets and granulocytes during hypothermic ECC. Human blood was treated with the P₂Y₁₂ antagonist 2-MeSAMP, the P₂Y₁ antagonist MRS2179, the PI3K p110β inhibitor TGX-221, combinations thereof, or PBS and propylene glycol (controls). Under static in vitro conditions a concentration-dependent effect regarding the inhibition of ADP-induced platelet activation was found using 2-MeSAMP or TGX-221. Further inhibition of ADP-mediated effects was achieved with MRS2179. Next, blood was circulated in an ex vivo ECC model at 28°C for 30 minutes and various platelet and granulocyte markers were investigated using flow cytometry, ELISA and platelet count analysis. GPIIb/IIIa activation induced by hypothermic ECC was inhibited using TGX-221 alone or in combination with P₂Y blockers (p<0.05), while no effect of hypothermic ECC or antiplatelet agents on GPIIb/IIIa and GPIbα expression and von Willebrand factor binding was observed. Sole P₂Y and PI3K blockade or a combination thereof inhibited P-selectin expression on platelets and platelet-derived microparticles during hypothermic ECC (p<0.05). P₂Y blockade alone or combined with TGX-221 prevented ECC-induced platelet-granulocyte aggregate formation (p<0.05). Platelet adhesion to the ECC surface, platelet loss and Mac-1 expression on granulocytes were inhibited by combined P₂Y and PI3K blockade (p<0.05). Combined blockade of P₂Y₁₂, P₂Y₁ and PI3K p110β completely inhibits hypothermic ECC-induced activation processes. This novel finding warrants further studies and the development of suitable pharmacological agents to decrease ECC- and hypothermia-associated complications in clinical applications.

Haemostatic therapy in coronary artery bypass graft patients with decreased platelet function: comparison of fibrinogen concentrate with allogeneic blood products

BACKGROUND

Patients undergoing coronary artery bypass grafting (CABG) are at risk of postoperative bleeding because of decreased platelet function and cardiopulmonary bypass (CPB)-induced haemostatic impairment. Fibrinogen concentration decreases by 34-42% of the preoperative level by the end of CPB. An inverse relationship between perioperative plasma fibrinogen levels and postoperative bleeding has been reported in CABG patients. Administration of fibrinogen concentrate after weaning from CPB in patients with diffuse microvascular bleeding may help promote haemostasis. We compared patient outcomes following fibrinogen concentrate administration or transfusion of allogeneics in CABG patients with decreased platelet function.

METHODS

Thirty-eight patients with decreased preoperative platelet function in Multiplate aggregometry were included. Patients with bleeding after CPB received either fibrinogen concentrate (guided by the measurement of fibrin clot quality using the FIBTEM thromboelastometric test) or allogeneics.

RESULTS

Twenty-nine of 38 patients received haemostatic therapy (bleeding + fibrinogen group, n = 10; bleeding + allogeneics group, n = 19). Total transfusion (median (interquartile range)) was significantly lower in the bleeding + fibrinogen group (0 (0, 3.8) units), compared with the bleeding + allogeneics group (6 (5, 8) units, p = 0.0073). Bolus administration of fibrinogen concentrate increased FIBTEM maximum clot firmness from 10.5 (9.3, 11) mm after CPB to 20.5 (20, 21.8) mm at the end of surgery. Postoperative outcomes were similar in both groups. No treatment-related complications were observed after fibrinogen concentrate.

CONCLUSIONS

In CABG patients with bleeding after CPB, FIBTEM-guided administration of fibrinogen concentrate resulted in overall decreased transfusion, compared with haemostatic therapy with allogeneics. Fibrinogen concentrate administration increased the fibrin clot quality and helped achieve haemostasis.

Peri-operative platelet function testing: the potential for reducing ischaemic and bleeding risks

The pivotal role of platelet activation and reactivity during atherothrombotic event occurrence associated with acute coronary syndromes (ACS) or percutaneous coronary interventions (PCI) is well established. Numerous translational research studies have established a threshold level of platelet reactivity during dual antiplatelet therapy above which a higher risk for ischaemic event occurrence has been observed. The clinical validity of these threshold values in reducing ischemic event occurrence with modified P2Y12 receptor therapy is currently under investigation in large-scale clinical trials. The association between on-treatment platelet reactivity measured by an ex vivo assay and the occurrence of bleeding events is less established. Currently, there is limited evidence of an association between platelet inhibition and coronary artery bypass grafting (CABG)- related bleeding in patients on clopidogrel therapy indicating that preoperative platelet function monitoring may guide both the timing of elective CABG and the administration of blood products in patients needing surgery. However, in the absence of a large-scale prospective clinical trial, routine platelet function monitoring and modification of timing of surgery based on platelet function monitoring are currently not recommended.

Platelet CD36 surface expression levels affect functional responses to oxidized LDL and are associated with inheritance of specific genetic polymorphisms

CD36 modulates platelet function via binding to oxidized LDL (oxLDL), cell-derived microparticles, and thrombospondin-1. We hypothesized that the level of platelet CD36 expression may be associated with inheritance of specific genetic polymorphisms and that this would determine platelet reactivity to oxLDL. Analysis of more than 500 subjects revealed that CD36 expression levels were consistent in individual donors over time but varied widely among donors (200-14,000 molecules per platelet). Platelet aggregometry and flow cytometry in a subset of subjects with various CD36 expression levels revealed a high level of correlation (r² = 0.87) between platelet activation responses to oxLDL and level of CD36 expression. A genome-wide association study of 374 white subjects from the Cleveland Clinic ASCLOGEN study showed strong associations of single nucleotide polymorphisms in CD36 with platelet surface CD36 expression. Most of these findings were replicated in a smaller subset of 25 black subjects. An innovative gene-based genome-wide scan provided further evidence that single nucleotide polymorphisms in CD36 were strongly associated with CD36 expression. These studies show that CD36 expression on platelets varies widely, correlates with functional responses to oxLDL, and is associated with inheritance of specific CD36 genetic polymorphisms, and suggest that inheritance of specific CD36 polymorphisms could affect thrombotic risk.

Comparison of the centrifugal and roller pump in elective coronary artery bypass surgery—a prospective, randomized study with special emphasis upon platelet activation

Objective--Evaluation of the centrifugal pump vs roller pump concerning effects upon platelet function, hemolysis and clinical outcome in elective coronary artery bypass surgery. Design--Thirty-four patients were randomized to centrifugal or roller pump. Platelet activation was studied by flow cytometry before, during and up to 3 days after bypass. Results--Duration of bypass, ischemic period, peripheral anastomoses, hospital stay and mortality did not differ. In roller pump patients, platelet aggregates increased by 250% between end of bypass and 3 h postoperatively (p < 0.001). A secondary, fivefold increase in number of platelet aggregates was found on the 3rd postoperative day (p < 0.001). In the centrifugal pump group, these changes were not significant. Hemolysis increased (20%) at end of bypass and 3 h postoperatively (p < 0.005), and decreased to preoperative levels the next day without group difference. Conclusion--Platelet aggregation was significantly increased in roller compared with centrifugal pump patients, indicating higher susceptibility to postoperative thrombotic complications with the roller pump. Otherwise, there was no clinical evidence for superiority of the centrifugal pump.

Inflammatory response and platelet activation after off-pump coronary artery bypass surgery

BACKGROUND

Cardiac surgery induces a systemic inflammatory activation and alterations in the hemostatic cascade. The responses contribute to postoperative complications but may also have protective effects. We investigated the relationship between inflammation, hemostasis and bleeding after off-pump coronary artery bypass surgery (OPCAB).

METHODS

Ten OPCAB patients were included in a prospective descriptive study. Selected markers of inflammation (IL-6, IL-8, PMN-elastase, C3a, and SC5b-9), and hemostasis (platelet count, ss-thromboglobulin, anti-thrombin, D-dimer and fibrinogen) were measured before and immediately after surgery. Postoperative bleeding was registered.

RESULTS

Inflammatory variables did not alter significantly during surgery while ss-thromboglobulin concentrations increased and anti-thrombin and fibrinogen decreased. There were significant postoperative correlations between PMN-elastase and ss-thromboglobulin (r=0.82, p=0.004), between PMN-elastase and fibrinogen (r=0.69, p=0.03) and between C3a and ss-thromboglobulin (r=0.71, p=0.02). In addition, there were significant inverse correlations between postoperative bleeding and pre- and postoperative fibrinogen levels (r=-0.76, p=0.011 and r=-0.84, p=0.002 respectively), between bleeding and postoperative ss-thromboglobulin levels (r=-0.66, p=0.04) and between bleeding and postoperative PMN-elastase (r=-0.75, p=0.01).

CONCLUSIONS

The results give further evidence for an association between the inflammatory response and hemostasis after cardiac surgery.

Evaluation of a new platelet function analyzer in cardiac surgery: a comparison of modified thromboelastography and whole-blood aggregometry

OBJECTIVES

Impaired hemostasis of multiple etiologies are often present in patients undergoing cardiopulmonary bypass (CPB) surgery. Platelet dysfunction is considered to be important in the early postoperative period. Therefore, a new whole-blood platelet function analyzer was compared with thromboelastography in predicting postoperative hemostatic outcomes as measured by blood loss and blood product use.

DESIGN

Prospective study.

SETTING

Teaching hospital.

PARTICIPANTS

The study enrolled 54 patients scheduled for coronary artery bypass surgery with CPB.

INTERVENTIONS

Coagulation and platelet function were assessed preoperatively, after CPB, at 3 hours, and at 24 hours after surgery by using thromboelastography and impedance aggregometry. Patients were divided into a transfused and nontransfused group on the basis of postoperative transfusion requirements. Postoperative blood loss and requirements of blood transfusions were documented until 24 hours postoperatively.

MEASUREMENTS AND MAIN RESULTS

Twenty-five patients (46%) received postoperative blood transfusions. Impaired hemostasis occurred after CPB detected by thromboelastography (p < 0.01) and impedance aggregometry (p < 0.01). In contrast to thromboelastography, preoperative adenosine diphosphate-mediated aggregometry correlated with postoperative requirements for blood transfusion (Spearman r = -0.302, p < 0.05) and was significantly lower in patients receiving allogeneic blood transfusion compared with nontransfused patients (p < 0.05). Neither aggregometry nor thromboelastography was correlated with postoperative blood loss.

CONCLUSION

Impedance aggregometry as well as thromboelastography are able to detect impaired hemostasis after CPB. In contrast to thromboelastography, aggregometry using a new whole-blood aggregometer identified patients with a reduced risk for postoperative transfusion requirements.

Protease activated receptors: clinical relevance to hemostasis and inflammation

The protease-activated receptors (PARs) are a unique family of vascular receptors that confer on cells an ability to sense, and respond to, local changes in the proteolytic environment. They are activated by serine proteases of the blood coagulation cascade, notably thrombin, and are linked to thrombotic and inflammatory effector pathways. In surgery with cardiopulmonary bypass (CPB), thrombin is generated in large quantities in the extracorporeal circuit and can exert systemic effects by way of platelet and endothelial PAR1. Aprotinin (Trasylol), a serine protease inhibitor used in cardiac surgery, preserves platelet function, and attenuates the inflammatory response by protecting the PAR 1 receptor on platelets and endothelium.

Perioperative Management of a Heterozygous Carrier of Glanzmann’s Thrombasthenia Submitted to Coronary Artery Bypass Grafting With Cardiopulmonary Bypass

Glanzmann's thrombasthenia is a congenital hemorrhagic disorder transmitted as an autosomal recessive trait and characterized by altered production and/or assembly of the platelet membrane glycoprotein IIb/IIIa receptor. We describe the perioperative management of a heterozygous carrier of Glanzmann's thrombasthenia submitted to cardiac surgery with cardiopulmonary bypass and the case was complicated by early excessive postoperative bleeding.

Effect of Clopidogrel Premedication in Off-Pump Cardiac Surgery

Background— Premedication with clopidogrel has reduced thrombotic complications after percutaneous coronary revascularization procedures. However, because of the enhanced and irreversible platelet inhibition by clopidogrel, patients requiring surgical revascularization have a higher risk of bleeding complications and transfusion requirements. A principal benefit of surgical coronary revascularization without cardiopulmonary bypass is its lower hemorrhagic sequelae. The purpose of this study was to evaluate the effect of preoperative clopidogrel administration in the incidence of hemostatic reexploration, blood product transfusion rates, morbidity, and mortality in patients undergoing off-pump coronary artery bypass graft surgery using a large patient sample and a risk-adjusted approach.

Methods and Results— Two hundred eighty-one patients (17.9%) did and 1291 (82.1%) did not receive clopidogrel before their surgery, for a total of 1572 patients undergoing isolated off-pump coronary artery bypass graft surgery between January 2000 and June 2002. Risk-adjusted logistic regression analyses and a matched pair analyses by propensity scores were used to assess the association between clopidogrel administration and reoperation as a result of bleeding, intraoperative and postoperative blood transfusions received, and the need for multiple transfusions. Hemorrhage-related preoperative risk factors identified in the literature and those found significant in a univariate model were used. The clopidogrel group had a higher likelihood of hemostatic reoperations (odds ratio [OR], 5.1; 95% confidence interval [CI], 2.47 to 10.47; P <0.01) and an increased need in overall packed red blood cell (OR, 2.6; 95% CI, 1.94 to 3.60; P <0.01), multiple unit (OR, 1.6; 95% CI, 1.07 to 2.48; P =0.02), and platelet (OR, 2.5; 95% CI, 1.77 to 3.66; P <0.01) transfusions. Surgical outcomes and operative mortality (1.4% versus 1.4%; P =1.00) were not statistically different.

Conclusions— Clopidogrel administration in the cardiology suite increases the risk for hemostatic reoperation and the requirements for blood product transfusions during and after off-pump coronary artery bypass graft surgery.