Dose Responses of Ibuprofen In Vitro on Platelet Aggregation and Coagulation in Human and Pig Blood Samples.

INTRODUCTION: Ibuprofen is commonly used by warfighters in the deployed environment. This study investigated its dose effects on in vitro coagulation in human and pig blood. METHODS: Blood samples were collected from 6 normal volunteers and 6 healthy pigs and processed to make platelet-adjusted samples (100 × 10(3)/µL, common transfusion trigger in trauma). Ibuprofen was added to the samples at concentrations of 0 µg/mL (control), the concentration from the highest recommended oral dose (163 µg/mL, 1×), and 2×, 4×, 8×, 10×, 12×, 16×, and 20×. Platelet aggregation by Chrono-Log aggregometer and coagulation by rotational thrombelastogram (Rotem) were assessed at 15 minutes after the addition of ibuprofen. RESULTS: A robust inhibition of ibuprofen on arachidonic acid-induced platelet aggregation was observed at all doses tested in human or pig blood. Collagen-stimulated platelet aggregation was inhibited starting at 1× in human blood and 4× in pig blood. Rotem measurements were similarly compromised in pig and human blood starting at 16×, except clot formation time was prolonged at 1× in human blood (all p < 0.05). CONCLUSION: Ibuprofen inhibited platelet aggregation at recommended doses, and compromised coagulation at higher doses. Human blood was more sensitive to ibuprofen inhibition. Further effort is needed to investigate ibuprofen dose responses on coagulation in vivo.

Effect of Ibuprofen dose on platelet aggregation and coagulation in blood samples from pigs.

INTRODUCTION: Ibuprofen is commonly used by Soldiers in the deployed environment. This study investigated its dose-effects on in vitro coagulation. METHODS: Blood samples were collected from 4 normal healthy pigs and were processed to make platelet-adjusted (100×10(3)/µL) blood samples. Ibuprofen was added to the samples at doses of 0 µg/mL (control), recommended oral dose (163 µg/mL, 1×), 2×, 4×, 8×, 10×, 12×, 16×, and 20×. Arachidonic acid or collagen-stimulated platelet aggregation was assessed at 15 minutes after the addition of ibuprofen. Coagulation was assessed with measurements of prothrombin time (PT) and activated partial thromboplastin time (aPTT), and thrombelastography by Rotem. RESULTS: A robust inhibition of ibuprofen on arachidonic acid-induced platelet aggregation was observed at all doses tested. Collagen-stimulated platelet aggregation was inhibited to 71%±5% and 10%±5% of the control values at ibuprofen doses of 4× and 20×, respectively (both p<0.05). No changes were observed in PT at any dose, but aPTT was prolonged at dose of 16× and 20×. Rotem measurements of coagulation time, clot formation time, maximum clot firmness, and A10 were compromised at dose 16× and 20× (all p<0.05). CONCLUSION: Ibuprofen inhibited platelet aggregation at recommended doses, but did not compromise aPTT or coagulation profile until at 16 times the recommended doses and higher. Further effort is needed to clarify whether there are different dose-responses between human and pig blood samples in trauma situations.

Effects of synthetic versus natural colloid resuscitation on inducing dilutional coagulopathy and increasing hemorrhage in rabbits.

BACKGROUND: : On the basis of logistic benefits of colloids over crystalloids, the U.S. military selected Hextend for resuscitation of combat casualties in the field. We investigated the effects of resuscitation with this fluid, as well as other colloids, on coagulation and uncontrolled bleeding in rabbits subjected to a splenic injury. METHODS: : Anesthetized male New Zealand white rabbits (3.3 kg +/- 0.2 kg) were divided into three groups and subjected to hypothermia (35 degrees C +/- 0.5 degrees C) and approximately 40% isovolemic blood exchange (hemodilution) with Hextend (H); Dextran70 (D); or 5% human albumin (A) solution (n = 8/group). Complete blood count, arterial blood gas, and coagulation values were measured before and after hemodilution. Laparotomy was performed and a standard splenic injury causing uncontrolled hemorrhage was made. Rabbits were resuscitated (25 mL/kg) with the same colloid used for hemodilution to restore baseline blood pressure. Animals were monitored for 2 hours or until death. Blood loss and survival times were measured. RESULTS: : There were no differences among groups in pH, Hct, fibrinogen, or platelets before or after hemodilution. Hct, fibrinogen, and platelets were reduced by 45% to 60% in all groups. Prothrombin time (PT) and activated partial thromboplastin time were prolonged in all the rabbits with the greatest increase in A group. Thrombelastograph (TEG) analysis showed longer initial reaction (R) and clotting (K) times, slower clotting rate and lower clot strength in H and D than A diluted blood. R time was faster and K time remained unchanged in A group after hemodilution. Thrombin generation potential and peak concentration of thrombin were unchanged in A samples but significantly reduced in H and D diluted samples. Subsequent splenic injury led to almost equal blood losses ( approximately 54 +/- 1 mL/kg) in H and D groups, which were higher (p < 0.01) than in A rabbits (37 +/- 4 mL/kg). This resulted in death of 100% (H), 75% (D), and 50% (A) of the rabbits with significant difference in survival time among the groups. CONCLUSION: : TEG and thrombin generation assays identified more severe coagulopathy development with H and D than A dilution, whereas plasma PT and activated partial thromboplastin time measurements did not differentiate between these colloids. These results suggest that resuscitation with albumin maintained coagulation function, decreased blood loss, and improved survival time compared with the synthetic colloids.

In vivo bleeding time and in vitro thrombelastography measurements are better indicators of dilutional hypothermic coagulopathy than prothrombin time.

BACKGROUND: The coagulopathy of trauma is generally confirmed by prothrombin time (PT) > or =16 seconds or an international normalized ratio > or =1.5. However, the utility of these values as a screening test is unknown. We examined different coagulation tests to determine the best predictor of coagulopathic bleeding and mortality in a small animal hemorrhage model. METHODS: Coagulopathy was induced in male New Zealand White rabbits by warfarin (W; 2 mg/kg for 2 days; n = 7), or hemodilution and hypothermia (HH; 50% blood exchange with Hextend, 34.5 +/- 0.3 degrees C; n = 7). Normal (N) rabbits without pretreatment served as the control (n = 7). Blood samples collected after coagulopathy induction and analyzed by prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG) tests. Liver bleeding time (BT) was also measured before injury. An uncontrolled hemorrhage was created by a longitudinal splenic incision and the abdomen was closed. Rabbits were resuscitated with Hextend solution (25 mL/kg) to return blood pressure to baseline and monitored for 2 hours or until death at which time blood loss was measured. RESULTS: Warfarin-induced coagulopathy increased BT, PT, and aPTT. TEG showed increased reaction (R) and clot formation (K) times and marked decrease in clotting rate (alpha angle and Vmax). Hemodilution hypothermia coagulopathy increased only BT and aPTT, and decreased the clotting rate (alpha angle and Vmax) and strength of the clot. After injury, blood losses were higher in coagulopathic rabbits (W = 54.6 +/- 4.2 and HH = 51.1 +/- 8.9 mL/kg) than in normal rabbits (30.6 +/- 12.4 mL/kg) and resulted in 86%, 100%, and 0% death, respectively. BT and Vmax consistently predicted coagulopathic bleeding and death in all animals. CONCLUSION: Although satisfactory in warfarin-induced coagulopathy, PT was not a valid screening test for dilutional and hypothermic coagulopathy. BT and TEG measurements of blood clotting rate are better indicators of coagulopathic bleeding and mortality in this lethal hemorrhage model.

The potential utility of fibrin sealant dressing in repair of vascular injury in swine.

BACKGROUND: A previous study in which fibrin sealant dressing (FSD) secured hemostasis in major arterial hemorrhage for 96 hours suggested the applicability of this dressing in damage control operations after severe trauma. The objective of this study was to determine the effective duration of FSD hemostatic function in vivo and to examine its potential utility for definitive repair of a major arterial injury in swine. METHODS: High pressure bleeding in an infrarenal aortotomy was controlled by placing FSD on the wound with 4-minute compression (n = 15). If hemostasis was achieved, the abdominal cavity was closed. Surviving animals were killed at 2, 4, 6, and 8 weeks and aortotomy sites collected for histology. RESULTS: FSD stopped arterial hemorrhage after 4-minute compression in 14 of 15 (93%) pigs. Dressings failed in two pigs at 36 and 53 minutes after treatment. Twelve (80%) animals recovered and resumed normal activities. Of the remaining 12, two developed rebleeding at the aortotomy site on days 8 and 11 and were killed; another was killed because of idiopathic low hematocrit on day 10. Nine pigs survived until scheduled to be killed, maintaining hemostasis with stable hematological values. In the surviving animals, serial computed tomography scans showed formation of a pseudoaneurysm at the aortotomy site, which resolved after 2 to 3 weeks. The initial vascular defect and pseudoaneurysm were filled with fibroblast-myoblast collagen rich tissues covered by endothelium. CONCLUSION: FSD can seal an arterial injury, stop high pressure bleeding, and prevent rebleeding for at least 7 days. The dressing may be most beneficial in damage control operations. If combined with an elective interventional radiologic procedure (e.g. embolization or stenting), it may also offer an alternative to suture repair of vascular injuries in cases where profuse bleeding obstructs visualization.

Comparison of hemorrhage control agents applied to lethal extremity arterial hemorrhages in swine.

BACKGROUND: QuikClot powder (QC), chitosan dressing (CD), and fibrin sealant dressing (FSD) are new hemostatic products touted to be more effective in controlling severe extremity bleeding than the current standard gauze dressing. All have been utilized in the global war on terrorism. Our objective was to evaluate the hemostatic efficacy of these three products in a model of severe extremity arterial hemorrhage that could not be stopped by standard gauze treatment. METHODS: A model of severe extremity arterial hemorrhage was developed in swine that was 100% fatal with standard gauze application and manual compression. The Army Field Bandage (AFB) was the standard gauze control. Anesthetized animals (n = 60, 15/group, 37.7 +/- 2.5 kg) were splenectomized and instrumented. A reproducible femoral artery injury was created using a 6 mm aortic punch, and free bleeding was allowed for 45 seconds. Each hemostatic agent was applied twice with three-minute compressions. All products were applied on actively bleeding wounds through a pool of blood. Fluid resuscitation was started with the first compression and titrated to a mean pressure of 65 mm Hg. Animals were observed for 180 minutes or until death. Endpoints were percent survival, survival time, blood loss, resuscitation volume, wound temperatures and tissue histology. Data are expressed as mean +/- SD and analyzed by Fisher's exact, logrank, and nonparametric ANOVA tests. RESULTS: Baseline physiologic parameters were similar among groups. AFB did not produce hemostasis. QC also showed no hemostatic benefit, and QC treatment markedly increased maximum wound temperatures to an average of 70.8 +/- 4.2 degrees C (p < 0.001). CD stopped bleeding temporarily in only one animal. There were no survivors in the AFB, QC, or CD groups. CD numerically prolonged survival time (58.9 +/- 21.1 minute) compared with the control (38.4 +/- 24.7 minutes, p = 0.045) but the difference was not significant. FSD reduced bleeding (p < 0.05) and prevented exsanguination in 10/15 (2/3) animals, and resulted in a significantly longer average survival time (p < 0.0001). CONCLUSION: FSD was superior to other currently utilized hemostatic products in controlling lethal arterial hemorrhage in this model of a fatal extremity wound. CD showed some hemostatic benefit. The exothermic reaction of QC was significant and resulted in gross and histologic tissue changes of unknown clinical significance. Controlled human studies with the promising products are required.