Distinctive patterns of sequential platelet counts following blunt traumatic brain injury predict outcomes

OBJECTIVE

To determine the role of platelet counts in the context of the decision to treat patients with non-compounded, non-surgically-treated blunt traumatic brain injury (NCNS-bTBI) with anticoagulants/antiaggregants.

METHODS

A retrospective analysis of 141 anticoagulants/antiaggregants-naïve patients with NCNS-bTBI. Changes in PT-INR and prolonged aPTT were examined and correlated with Marshall and Rotterdam scores, clinical and neuroradiological outcomes.

RESULTS

Three groups of platelet counts were identified. Group 1 (83% of patients) had normal platelet counts (150,000-450,000 platelets/mm3) from admission to discharge. Group 2 (13%) developed transient thrombocytopenia (<150,000 platelets/mm3) 2-3 days post-trauma. Group 3 (4%) developed extreme thrombocytosis > 1,000,000/mm3 platelets 6-9 days post-trauma. Neither acute coagulopathy of trauma nor progressive hemorrhagic insults followed NCNS-bTBI. Moreover, while patients with thrombocytosis/extreme thrombocytosis presented with a worse Glasgow coma score (GCS) on admission (8.8 ± 2.9 vs. 13 ± 2, p < 0.01) and had longer hospitalization (13.5 ± 10.4 vs. 4.5 ± 2.1 days), their improvement at discharge was the highest (delta GCS, 4 ± 2.8 vs. 1.2 ± 2.1, p = 0.05). Traumatic subarachnoid hemorrhage was associated with isolated thrombocytosis and 'best improvement.' No thromboembolic or hemorrhagic complications occurred.

CONCLUSION

NCNS-bTBI, thrombocytosis was correlated with better outcomes and was not associated with an increased risk for developing thromboembolism or hemorrhage, precluding the immediate need for any additional antiaggregates.

Multi-Modal Venous ThromboembolicProphylaxis Aids in Risk Reduction Following Splenectomy in Female and Male Mice

INTRODUCTION

Splenectomy (SPLN) is associated with elevated risk of venous thromboembolic (VTE) disease. Enoxaparin (ENX) is a low-molecular-weight heparin agent used in VTE chemoprophylaxis. Early aspirin administration ameliorates postSPLN platelet hyperaggregability in male mice. Previous literature has excluded female mice, citing potential effects of estrogen on platelet count and activation as a reason. We hypothesized that multimodal therapy using aspirin and ENX would mitigate postoperative platelet aggregability in mice across sexes.

METHODS

Murine models of SPLN included both male and female mice. Treatment groups included placebo gavage, sham laparotomy, SPLN alone, SPLN and aspirin, SPLN and ENX, and SPLN with aspirin and ENX (n = 5 per group). Chemoprophylaxis dosing was initiated before SPLN. Mice were euthanized on post-operative day (POD) 1 or 3; platelet counts were obtained and blood samples were analyzed via electrical impedance aggregometry.

RESULTS

Females on POD 3 following SPLN demonstrated increased platelet count compared to female mice with no treatment intervention. Male and female mice demonstrated increased adenosine diphosphate (ADP)-induced platelet aggregability on POD 3 following SPLN compared to the placebo group. Treatment with aspirin and ENX decreased this post-SPLN platelet hyperaggregability in both sexes. Females demonstrated significantly higher ADP-mediated platelet aggregability in placebo, SPLN, and SPLN with aspirin and ENX when compared to males of identical treatment groups on POD 3.

CONCLUSIONS

Platelet hyperaggregability following SPLN is mediated primarily by ADP in both males and females, but higher relative aggregability is demonstrated in females. Early administration of dual-agent VTE chemoprophylaxis utilizing aspirin and ENX mitigates this hyperaggregability and may aid in VTE risk reduction across sexes.

Aspirin Administration Mitigates Platelet Hyperaggregability After Splenectomy in a Murine Model

INTRODUCTION

Patients who undergo splenectomy (SPLN) have an estimated 10%-35% risk of venous thromboembolic events; however, the underlying mechanism and strategy for prevention have yet to be identified. The goals of this study were to 1) investigate platelet aggregation after SPLN, 2) examine if aspirin administration could mitigate this effect, and 3) determine if concomitant hemorrhage would affect post-SPLN platelet function and response to aspirin.

METHODS

Murine models of operative SPLN and submandibular bleed (SMB) were utilized. Mice were randomized to eight groups as follows: untouched, SPLN, sham (laparotomy only), SMB, SPLN + SMB, SPLN + aspirin (ASA), SMB + ASA, and SPLN + SMB + ASA. Aspirin (50 mg/kg) was administered on postoperative days (PODs) one and two via oral gavage. Mice were euthanized on POD 3, platelet counts were obtained, and blood samples were analyzed via rotational thromboelastometry and impedance aggregometry with adenosine diphosphate (ADP) and arachidonic acid (AA) as agonists.

RESULTS

By POD 3, SPLN mice displayed a significant thrombocytosis compared to untouched, SMB, and sham SPLN mice. Clotting time and clot formation time were significantly decreased in SPLN and SPLN + SMB cohorts compared to untouched and sham controls with elevated mean clot firmness. SPLN mice also displayed a significant increase in ADP- and AA-mediated platelet aggregability compared to untouched controls, SMB, and SPLN + SMB. ASA significantly decreased platelet aggregation via both ADP and AA signaling in SPLN and SPLN + SMB cohorts without affecting viscoelastic coagulation testing.

CONCLUSIONS

Platelet hyperaggregability after SPLN is mediated by both ADP and AA signaling. Early aspirin administration may prevent increased platelet aggregation exacerbated after polytrauma.

Etiologies of Extreme Thrombocytosis: A Contemporary Series

OBJECTIVE

To describe the multifactorial etiologies of extreme thrombocytosis (EXT) in different care settings and the frequency of finding an occult malignancy.

PATIENTS AND METHODS

We conducted a retrospective chart review at Mayo Clinic from January 1, 2011, through December 31, 2016. Adult patients who had at least 2 readings of platelet counts greater than 1000×10⁹/L within 30 days of each other were included. We determined the causes of EXT on the basis of preset definitions of precipitating factors and identified the dominant causes on the basis of the trend of platelet counts.

RESULTS

A total of 44,490 patients had thrombocytosis, and 305 patients (0.7%) had EXT. In 242 patients (79.3%), EXT was multifactorial. Surgical complications (54.1%) and hematologic malignancies (27.9%) were the 2 most dominant causes. Thirty-eight patients (12.5%) had new diagnoses of malignancies, mostly myeloproliferative neoplasms. In inpatients, surgical complications (71.9%), concurrent/previous splenectomy (50.5%), and infections (44.9%) were the most common causes, whereas hematologic malignancies (56.9%), iron deficiency (36.7%), and previous splenectomy (28.4%) were the most common causes in outpatients. Hematologic malignancy was 3.4 times more likely to be the cause of EXT in outpatients than in inpatients (56.9% vs 16.8%), and a new diagnosis of hematologic malignancy was 1.9 times more likely to be made in outpatients (15.6% vs 8.2%). Eighty-four percent of patients had resolution of EXT within 30 days. One patient died during the period of EXT. Nonsurgical patients with hematologic malignancies had the most prolonged period of EXT.

CONCLUSION

Extreme thrombocytosis is a multifactorial hematologic condition, and its etiology differs substantially between inpatients and outpatients. Occult hematologic malignancies are uncommon in EXT when other major causes are present.

Assessment of procoagulant potential in patients with reactive thrombocytosis and its association with platelet count

OBJECTIVE

We aimed to determine hemostatic changes and characterize the procoagulant potential among patients with reactive thrombocytosis (RT).

METHODS

Sixty patients with RT (median platelet count 718 × 10⁹ /L) and 20 healthy persons were tested for complete blood count, C-reactive protein, von Willebrand factor (VWF), factor VIII and fibrinogen, and thrombin generation. Platelet studies, including light transmission aggregometry and Cone and Plate(let) Analyzer, were also conducted. Reticulated platelets and platelet P-selectin expression were measured using flow cytometry.

RESULTS

Compared to patients with mild thrombocytosis (platelet count 500-700 × 10⁹ /L; n = 27), those with moderate-to-severe thrombocytosis (platelet count >700 × 10⁹ /L; n = 33) had significantly higher fibrinogen, factor VIII, and VWF antigen and activity levels; higher endogenous thrombin potential, peak thrombin generation and velocity index levels, and shorter time-to-peak thrombin level. VWF antigen and activity, fibrinogen, and factor VIII were positively associated with platelet count, whereas VWF activity/antigen ratio was inversely correlated. In a multivariate analysis of RT and control participants, only platelet count predicted endogenous thrombin potential with a positive-linear correlation. No patients developed acquired von Willebrand syndrome.

CONCLUSIONS

As determined by thrombin generation, RT was associated with in vitro prothrombotic tendency, which correlated with platelet count. This may explain the increased thromboembolic risk previously reported in patients with RT.

Thrombocytosis in splenic trauma: In-hospital course and association with venous thromboembolism

INTRODUCTION

Thrombocytosis is common following elective splenectomy and major trauma. However, little is known about the in-hospital course of platelet count (PC) and incidence of thrombocytosis after splenic trauma. Extreme thrombocytosis (PC>1000×10⁹) is associated with increased risk of venous thromboembolism (VTE) in primary thrombocytosis leading to the use of acetylsalicylic acid (ASA) for risk reduction, but the need for this agent in splenic trauma is undefined.

METHODS

Retrospective cohort study of all patients with splenic trauma between April 1, 2010 and March 31, 2014. The in-hospital course of PC was assessed based on splenic injury management type. The association of management type with thrombocytosis was evaluated using a multivariable logistic regression model adjusting for potential confounders. The association of thrombocytosis, extreme thrombocytosis, and ASA use for the outcome of VTE was explored.

RESULTS

156 patients were eligible, PC initially increased in all patients with the highest peak after total splenectomy. The incidence of thrombocytosis was 41.0% (64/156). Thrombocytosis was more likely following splenectomy compared with spleen preserving strategies independent of length of stay, injury grade, ISS, age and transfusion (OR 7.58, 95% CI: 2.26-25.45). Splenectomy was associated with extreme thrombocytosis (OR 10.39, 95% CI: 3.59-30.07).

CONCLUSIONS

Thrombocytosis in splenic trauma is more likely after splenectomy than with spleen preserving strategies. Splenectomy is associated with extreme thrombocytosis. There was insufficient data in our study to determine the use of ASA as primary prevention of VTE after splenic trauma.

Splenectomy is associated with a higher risk for venous thromboembolism: A prospective cohort study

BACKGROUND

Thrombocytosis following splenectomy is a common occurrence. Whether this thrombocytosis leads to a higher risk for venous thromboembolism (VTE) remains unclear. This investigation aimed to determine if splenectomy increases the risk for VTE.

METHODS

This was a prospective study conducted in the SICU between 1/2011 and 11/2013 investigating the VTE risk in patients undergoing a splenectomy compared with those undergoing any other abdominal procedure.

RESULTS

In total 2503 patients were admitted to the SICU: 37 (2%) after a splenectomy and 638 (26%) after any other abdominal surgery. Splenectomy patients had a higher incidence of VTE compared to patients undergoing any other abdominal procedure (29.7% vs. 12.1%, p < 0.01). After adjustment, splenectomy was associated with a higher adjusted risk for VTE compared to the no-splenectomy group (AOR [95% CI]: 2.6 [1.2, 5.9], p = 0.02). Reactive thrombocytosis did not predict the development of VTE.

CONCLUSION

Splenectomy increases the risk for VTE, however reactive thrombocytosis is not associated with this higher incidence. Further investigations are required to characterize the pathophysiologic mechanisms of VTE development following splenectomy.