Robert C. Gosselin

The effects of flavanol-rich cocoa and aspirin on ex vivo platelet function

BACKGROUND Flavanols modulate platelet function in vitro, but less is known of their in vivo effects and how they compare to pharmacological platelet inhibitors. We investigated the effect of a flavanol-rich cocoa beverage (897 mg/ml) in combination with and in comparison to aspirin on platelet function and activation in healthy subjects. METHODS AND RESULTS On separate test days in a crossover design, 16 healthy adults consumed aspirin (81 mg), cocoa (as a beverage), or aspirin plus cocoa. Platelet activation was measured by surface expression of P-selectin and PAC-1 binding to the activated conformation of the GPIIb/IIIa receptor (GPIIb/IIIa-act). Platelet function was measured on an analyzer (the PFA-100) that measures shear stress-induced platelet plug formation in response to collagen-epinephrine or collagen-ADP. Plasma epicatechin concentrations peaked approximately 2 h after subjects were given either the cocoa or aspirin plus cocoa. After 6 h, cocoa inhibited epinephrine-induced platelet function. Epinephrine-induced platelet function was inhibited 2 and 6 h after aspirin, and after aspirin plus cocoa. Epinephrine-stimulated P-selectin expression was inhibited by aspirin at 6 h, and after 2 and 6 h by aspirin plus cocoa. ADP-stimulated P-selectin expression was not affected by the treatments. Cocoa and aspirin, given separately, reduced epinephrine-stimulated GPIIb/IIIa-act expression at 2 and 6 h, respectively, and at 2 and 6 h when given together, suggesting an additive effective. ASA plus cocoa inhibited ADP-stimulated GPIIb/IIIa-act expression at 6 h. CONCLUSIONS Flavanol-rich cocoa inhibited epinephrine-stimulated platelet activation and function. These effects were qualitatively similar to aspirin, but less profound. These results emphasize the need to further examine the effects of food flavonoids for platelet modulating effects.

Platelet Activation and Function after Trauma

BACKGROUND Abnormal hemostasis is associated with many of the complications of trauma-associated morbidity and mortality. Platelets are integral in the maintenance of hemostasis. METHODS Samples were obtained from 100 trauma patients on arrival at the emergency room (initial time) and at 24, 48, and 72 hours later. Samples were also obtained from 10 healthy controls at the same time intervals. Using flow cytometry, three parameters were used to measure platelet activation: platelet microparticles, expression of P-selectin (CD62P), and expression of the activated conformation of glycoprotein IIb-IIIa (PAC-1 binding). Platelet function was measured using a platelet function analyzer (PFA-100, Dade International Inc., Miami, FL). RESULTS One hundred trauma patients were enrolled. The average age was 40 years, 75% were men, and 84% had blunt injuries. The mean Injury Severity Score was 22.3 +/- 10.9 (mean +/- SD) and the average Glasgow Coma Scale score was 11 +/- 4. All three platelet activation parameters were increased in trauma patients versus controls for all time periods (p < 0.001). Trauma patients had a trend toward a shorter initial collagen/epinephrine closure time versus controls (p = 0.096). Compared with the 24-, 48-, and 72-hour time intervals, initial collagen/epinephrine closure times were shortened (p < 0.001, p < 0.001, and p < 0.001). Platelet function returned to normal reference ranges within 24 hours but platelet activation parameters remained elevated at least 72 hours after initial trauma. In contrast, when trauma patients with and without brain injury were compared, brain injury patients had increased platelet activation but decreased platelet function (increased collagen/epinephrine closure times). In addition, there was a significant prolongation in collagen/epinephrine closure times for the 24-, 48-, and 72-hour time points in nonsurviving patients versus survivors. There was no association between platelet activation and function and other adverse outcomes including pulmonary embolism, deep venous thrombosis, and disseminated intravascular coagulation. CONCLUSION Severe injury usually results in increased platelet activation and function. However, the combination of increased platelet activation with decreased function was associated with increased mortality.

Cocoa and Wine Polyphenols Modulate Platelet Activation and Function

There is speculation that dietary polyphenols can provide cardioprotective effects due to direct antioxidant or antithrombotic mechanisms. We report in vitro and postingestion ex vivo effects of cocoa procyanidins, a procyanidin-rich cocoa beverage and dealcoholized red wine (DRW) on human platelet activation. In a series of in vitro studies, cocoa procyanidin trimers, pentamers or DRW (3 and 10 micromol/L) were incubated with citrated peripheral whole blood in the presence and absence of platelet agonists. Platelet activation was detected using fluorescent-labeled monoclonal antibodies recognizing the fibrinogen binding conformation of GPIIb-IIIa (referred to herein as PAC-1 binding) and the activation-dependent platelet epitope CD62P (P-selectin). The percentage of CD42a-positive platelets coexpressing PAC-1 binding and/or CD62P was determined by multiparameter flow cytometry. Procyanidin trimers, pentamers and DRW added to whole blood in vitro increased PAC-1 binding and P-selectin expression. In contrast, procyanidin trimers, pentamers and DRW inhibited the platelet activation in response to epinephrine. The effects on platelet activation of cocoa beverage and DRW consumption were also studied in healthy subjects. Citrated blood was obtained before and 2 and 6 h after the ingestion of a cocoa beverage, a caffeine-containing beverage, DRW or water. Platelet activation was measured by flow cytometry. The consumption of DRW did not affect the expression of activation-dependent platelet antigens, either unstimulated or after ex vivo activation with epinephrine. However, the consumption of DRW increased PAC-1 binding in response to 100 micromol/L ADP ex vivo. Cocoa consumption reduced platelet response to agonists ex vivo. The ingestion of water had no effect on platelet activation, whereas a caffeine-containing beverage augmented the response of platelets to epinephrine. In summary, select cocoa procyanidins and DRW added to whole blood in vitro increased expression of platelet activation markers in unstimulated platelets but suppressed the platelet activation response to epinephrine. In contrast, cocoa consumption suppressed unstimulated and stimulated platelet activation in whole blood. This suppressive effect observed on platelet reactivity may explain in part the reported cardioprotective effects of dietary polyphenols.

Systemic stress response after laparoscopic and open gastric bypass

BACKGROUND The magnitude of the systemic stress response is proportional to the degree of operative trauma. We hypothesized that laparoscopic gastric bypass (GBP) is associated with reduced operative trauma compared with open GBP, resulting in a lower systemic stress response. STUDY DESIGN Forty-eight patients with a body mass index of 40 to 60 were randomly assigned to laparoscopic (n = 26) or open (n = 22) GBP Blood samples were measured at baseline and at 1, 24, 48, and 72 hours postoperatively. Metabolic (insulin, glucose, epinephrine, norepinephrine, dopamine, ACTH, cortisol), acute phase (C-reactive protein), and cytokine (interleukin [IL]-6, IL-8, tumor necrosis factor [TNF]-alpha) responses were measured. Catabolic response was also measured by calculating the nitrogen balance at 24 and 48 hours postoperatively. RESULTS The two groups of patients were similar in terms of age, gender, and preoperative body mass index. The mean operative time was longer for laparoscopic GBP than for open GBP (229 +/- 50 versus 207 43 minutes). After laparoscopic and open GBP, plasma concentrations of insulin, glucose, epinephrine, dopamine, and cortisol increased; IL-8 and TNF-alpha remained unchanged; and negative nitrogen balances occurred at 24 and 48 hours. There was no significant difference in these parameters between groups. Concentrations of norepinephrine, ACTH, C-reactive protein, and IL-6 levels also increased, but these levels were significantly lower after laparoscopic GBP than after open GBP (p < 0.05). CONCLUSIONS Systemic stress response after laparoscopic GBP is similar to that after open GBP, except that concentrations of norepinephrine, ACTH, C-reactive protein, and IL-6 are lower after laparoscopic than after open GBP. These findings may suggest a lower degree of operative injury after laparoscopic GBP.

Increased use of prophylactic vena cava filters in trauma patients failed to decrease overall incidence of pulmonary embolism.

BACKGROUND Recent studies have reported that placement of vena cava filters (VCFs) early after injury may decrease the incidence of pulmonary embolism (PE) in high-risk trauma patients. STUDY DESIGN This was a retrospective review of all trauma patients with placement of VCFs admitted to a single level-1 trauma center between 1989 and 1997. Two cohorts corresponding to years of high or low prophylactic VCF use (PVCF) were compared. RESULTS Records were reviewed for 299 trauma patients identified as having had placement of a VCE Two hundred forty-eight filters were placed before the diagnosis of PE. During years of low PVCF use, the overall PE incidence was 0.31%; during years of high PVCF use, the incidence of PE was higher at 0.48% (p = 0.045, chi-square). CONCLUSIONS Increased use of PVCFs failed to decrease the overall rate of PE in our trauma patient population.

High-level long-term white blood cell microchimerism after transfusion of leukoreduced blood components to patients resuscitated after severe traumatic injury

BACKGROUND: Long‐term white blood cell (WBC) microchimerism (MC), of at least 2 years, has been reported in trauma patients receiving fresh nonleukoreduced (non‐LR) blood. It is unknown, however, whether this occurs with LR blood products that are nearly devoid of WBCs. Twenty‐seven patients transfused with LR and non‐LR blood products were studied after severe traumatic injury. A secondary aim was to explore donor‐recipient mixed lymphocyte reactivity in vitro.

Effect of critical injury on plasma antithrombin activity: Low antithrombin levels are associated with thromboembolic complications

OBJECTIVE Determine whether severe injury results in decreased plasma antithrombin (AT) activity and whether this decreased AT activity is associated with thromboembolic complications. DESIGN Prospective observational. SUBJECTS A total of 157 critically injured trauma patients. METHODS Each patient underwent laboratory analysis on arrival to the emergency room at hours 8, 16, 24, and 48, and days 3, 4, 5, and 6. Laboratory analyses included AT, tissue factor pathway inhibitor, protein C, prothrombin fragment 1.2, thrombin-antithrombin complex, and D-dimer. Patients were followed for thromboembolic complications including: deep venous thrombosis (DVT), pulmonary embolus, disseminated intravascular coagulation (DIC) and adult respiratory distress syndrome (ARDS). RESULTS Mean Injury Severity Score was 23 (+/-11). AT activity fell below normal in 95 (61%) patients; AT activity rose to greater than normal in 51 (32%) patients. Nine (6%) patients developed DVT, two (1%) pulmonary embolus, 13 (8%) DIC and 26 (17%) ARDS. Using logistic regression analysis, low AT levels were a significant predictor of DVT, DIC, and ARDS (p < 0.05). Supranormal At levels were associated with closed head injury (p < 0.05). D-dimer levels were inversely correlated with AT (p < 0.05). CONCLUSIONS AT activity was depressed in critically injured patients. Patients with head injury developed supranormal AT activity. The risk factors for AT deficiency mimicked those for thromboembolism. Patients with decreased AT activity were at increased risk for thromboembolic complications. Given heparins dependence on AT, these data call into question the use of unmonitored heparin thromboembolism prophylaxis.

Dabigatran Effects on the International Normalized Ratio, Activated Partial Thromboplastin Time, Thrombin Time, and Fibrinogen: A Multicenter, In Vitro Study:

Background: Patients receiving the direct thrombin inhibitor dabigatran may have selected anticoagulation assays performed as part of routine care. The effect of dabigatran on the international normalized ratio (INR), activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen requires clarification. Objective: To describe the effect of dabigatran on selected assays in North America and the United Kingdom. Methods: Pooled normal plasma enriched with dabigatran at concentrations of 25, 50, 75, 100, 125, 150, 200, 300, 400, and 500 ng/mL were sent blinded to 19 centers in the US, the UK, and Canada to assess the effect of dabigatran on routine coagulation screening tests, the INR, aPTT, TT, and fibrinogen. Results: Data were returned from 16 centers. For effects on INR, Neoplastine CI Plus and Simplastin HTF were the most sensitive and Thromborel S the least sensitive to increasing dabigatran concentrations. For the aPTT, all reagents demonstrated decreasing sensitivity to increasing dabigatran concentrations. Measured fibrinogen either demonstrated no change or factitious decrease with increasing dabigatran concentrations. Commercial TT methods were very sensitive to low concentrations of dabigatran, with 9 of 10 reporting sites exceeding test limits at dabigatran concentrations of 100 ng/mL. Conclusions: The INR, aPTT, and TT rise as dabigatran concentrations increase. Both the INR and aPTT increase in a linear pattern with marginal slopes, creating challenges in using these assays as reliable means for assessing the amount of dabigatran present. The commercial TT assay is very sensitive at low concentrations of dabigatran. Fibrinogen test results may be either unaffected or lower in the presence of dabigatran.

Reversing Dabigatran in Life-threatening Bleeding Occurring During Cardiac Ablation With Factor Eight Inhibitor Bypassing Activity

Objectives:We report a case of a patient receiving dabigatran who developed a life-threatening bleeding complication during cardiac ablation that rapidly resolved after administration of Factor Eight Inhibitor Bypassing Activity (FEIBA). Background:Therapeutic anticoagulation with warfarin during cardiac ablation has been shown to reduce the risk of stroke and systemic embolism. Cardiac tamponade is a potentially life-threatening procedural complication requiring emergent reversal of anticoagulation and pericardiocentesis. Dabigatran is superior to warfarin in preventing stroke and systemic embolism in nonvalvular atrial fibrillation, but has not been evaluated for use during cardiac ablation. Dabigatran is without a known reversal agent and, should tamponade occur during ablation, it is unclear what reversal strategy could be used to establish hemostasis. Methods and Results:A 67-year-old man with history of atrial fibrillation with rapid ventricular rate, two previous atrial fibrillation ablations, and prescribed dabigatran 150 mg bid was admitted for an atrial fibrillation ablation procedure. The last dabigatran dose was 7 hours prior to procedure. During the procedure, a transseptal perforation occurred, requiring an emergent pericardiocentesis. Within 60 minutes, approximately 4.5 L of blood was removed via the pericardiocentesis. Low-dose FEIBA (3159 units, 26 U/kg actual body weight) over 15 minutes was administered. Hemostasis was noted within minutes of initiating the infusion with cessation of bleeding after administration was complete. Conclusion:This case report describes the potential ability of a low dose of the activated prothrombin complex concentrate, FEIBA, to reestablish hemostasis independent of the pharmacologic effects of dabigatran. Additional studies are warranted to confirm the findings of our observation.

Reversal of Elevated International Normalized Ratios and Bleeding with Low-Dose Recombinant Activated Factor VII in Patients Receiving Warfarin

Study Objective. To assess the effectiveness of using low‐dose recombinant activated factor VII (rFVIIa) to reverse the effects of warfarin in critically ill patients with major bleeding events.