Synthesis and Biological Evaluation of Novel Thiadiazole Derivatives as Antiplatelet Agents

A novel series of thiadiazole compounds was synthesized through the reaction of thiosemicarbazone intermediates with 2, 3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The antiplatelet activity of the synthesized compounds was evaluated using an aggregation test with adenosine diphosphate (ADP) and arachidonic acid (AA) as platelet aggregation inducers. Among the synthesized analogs, compound 3b exhibited the most potent inhibition of platelet aggregation induced by ADP (half maximal inhibitory concentration [IC50] = 39 ± 11 µM). Molecular docking studies of 3b revealed hydrogen bonds between the nitrogen of the thiadiazole ring and Lys280. The tolyl ring exhibited hydrophobic interactions with Tyr105, similar to the antagonist co-crystallized with P2Y12 (PDB ID: 4NTJ). These compounds have the potential to serve as lead molecules for designing P2Y12 inhibitors.

Pharmacokinetic, pharmacodynamic, and pharmacogenetic assays to monitor clopidogrel therapy

Clopidogrel is the most common and widely used antiplatelet agent for patients with coronary artery disease following confirmation by electrocardiographic studies. The nonresponsiveness of patients to clopidogrel and the possibility of testing for clopidogrel resistance by platelet function assays (PFA) are contentious issues. Light transmission aggregometry (LTA) is considered as the gold standard test among all PFA. In this review, the most commonly used PFA used for monitoring the effect of clopidogrel, LTA, vasodilator-stimulated phosphoprotein assay phosphorylation, rotational thromboelastometry (ROTEM) delta and ROTEM platelet, thromboelastography, PFA-100, VerifyNow P2Y12 assay, Multiplate analyzer, Plateletworks assay and pharmacogenetic studies, are comparatively discussed including their principles of action, advantages, and disadvantages. VerifyNow P2Y12 assay can be accepted as the ideal point of care test out of the discussed assays. However, modified assays are required which could overcome the limitations associated with currently available assays.

[SBA 2020: Regional anesthesia guideline for using anticoagulants update]

The development of protocols to prevent perioperative Venous Thromboembolism (VTE) and the introduction of increasingly potent antithrombotic drugs have resulted in concerns of increased risk of neuraxial bleeding. Since the Brazilian Society of Anesthesiology (SBA) 2014 guideline, new oral anticoagulant drugs were approved by international regulating agencies, and by ANVISA. Societies and organizations that try to approach concerns through guidelines have presented conflicting perioperative management recommendations. As a response to these issues and to the need for a more rational approach, managements were updated in the present narrative revision, and guideline statements made. They were projected to encourage safe and quality patient care, but cannot assure specific results. Like any clinical guide recommendation, they are subject to review as knowledge grows, on specific complications, for example. The objective was to assess safety aspects of regional analgesia and anesthesia in patients using antithrombotic drugs, such as: possible technique-associated complications; spinal hematoma-associated risk factors, prevention strategies, diagnosis and treatment; safe interval for discontinuing and reinitiating medication after regional blockade.

Evaluation of the use of anti-platelet therapy throughout the peri-operative period in patients with femoral neck fracture surgery. A retrospective cohort study

INTRODUCTION

Fracture neck of femur (hip fracture) is a very common problem among old age group. Such elderly patients usually have some comorbidities for which they may use anti-platelet therapy (such as clopidogrel, aspirin, or others) for long duration (chronic use). These anti-platelet medications might make the blood thin and increase bleeding tendency. So, if these elderly people present with fracture neck of femur requiring surgical intervention, they might be at increased risk of bleeding and other complications if the use of these anti-platelet agents was continued throughout the peri-operative period.

OBJECTIVES

This current study aims to find out whether it is safe or not to continue the use of anti-platelet drugs during the peri-operative period in patients with hip fracture surgery. If it is safe and there are no complications, then there is no harm to continue the use of these drugs peri-operatively without any surgical delay. But if it is unsafe and there is increased risk of bleeding or blood transfusion or other complications, then such medications must be stopped peri-operatively. Thus, the medical practice and care will be improved to achieve patient safety.

METHODS

It was a retrospective study which reviewed files and notes of patients who had hip fracture surgery. These patients were divided into 2 groups. First group was on long-term anti-platelet treatment (APTG), and the use of these medicines continued during the peri-operative phase. The second group was not on anti-platelet treatment at all (NAPTG). Then, a comparison was done between both groups in terms of the following parameters during the peri-operative (pre- and post-operative) period: (i) intra-operative blood loss, (ii) operative time in minutes (length of surgery), (iii) pre-operative haemoglobin level, (iv) the need for blood transfusion, (v) haematoma formation, (vi) re-operation for any reason, (vii) post-operative wound infection, and (viii) duration in days to achieve complete wound healing post-operatively. So these measures are good parameters to assess bleeding tendency and bleeding risk. Data was collected, and statistical analysis was done using Pearson's chi-squared test and independent sample t test as appropriate.

RESULTS

325 participants were enrolled in the study. There were 163 patients in the APTG (Anti-Platelet Treatment Group) and 162 patients in the NAPTG (Non-Anti-Platelet Treatment Group). It has been found that there was no statistically significant difference between the APTG and NAPTG in terms of these peri-operative parameters: (i) intra-operative blood loss, (ii) operative time in minutes (length of surgery), (iii) pre-operative haemoglobin level, (iv) the need for blood transfusion, (v) haematoma formation, (vi) re-operation for any reason, (vii) post-operative wound infection, and (viii) duration in days to achieve complete wound healing post-operatively (P > 0.650).

CONCLUSION

It is safe to continue the use of anti-platelet therapy throughout the peri-operative phase in patients with hip fracture surgery. The continuation of such therapy is not associated with increased risk of bleeding or blood transfusion or other complications in patients who had surgical treatment for femoral neck fracture.

Assessment of platelet function after discontinuation of ticagrelor

BACKGROUND

Patients presenting with acute coronary syndromes (ACS) are often treated by percutaneous coronary intervention (PCI) with insertion of coronary artery stents and a majority receive dual antiplatelet therapy (DAPT), usually a combination of a COX-1 inhibitor (aspirin) and a P2Y₁₂ inhibitor (eg ticagrelor). Not seldom the question arises as to when DAPT should be discontinued prior to interventional surgery. This study was done with the primary aim of investigating thrombocyte function immediately prior to and after discontinuation of ticagrelor.

MATERIALS AND METHODS

In this prospective, longitudinal, observational study including 24 patients, venous blood was obtained from patients on day 0, before stopping maintenance dose of 90 mg ticagrelor twice daily, and then on days 1, 3, 5, and 8, after discontinuation. Samples were analyzed using Multiplate^® and VerifyNow^® .

RESULTS

Prior to urgent surgery platelet aggregation >30 aggregation units (Multiplate^® ) and >208 P2Y₁₂ reaction units (VerifyNow^® ) have been shown to correlate with reduced risk of peri- and postoperative bleeding risk. On day 3 after ticagrelor discontinuation, 100% (P = .016) and 67% (P=<.001) of patients had reached these levels on Multiplate^® and VerifyNow^® , respectively. On day 5, the corresponding figures were 100% (P = .016) and 78% (P=<.001).

CONCLUSION

Discontinuation of ticagrelor for 3 days resulted in return of adequate platelet function in all patients on Multiplate^® and in a majority of patients on VerifyNow^® , indicating a lower bleeding risk. A bedside test for platelet function may be considered if time to anticipated surgery is less than 5 days after ticagrelor discontinuation.

Anticoagulation and Spine Surgery

STUDY DESIGN

Literature review.

OBJECTIVE

Preoperative management of therapeutic anticoagulation in spine surgery is critical to minimize risk of thromboembolic events yet prevent postsurgical complications. Limited research is available, and most guidelines are based on drug half-lives. We aim to clarify current guidelines and available evidence for safe practice of spine surgery in this patient population.

METHODS

A literature search in PubMed was done encompassing comprehensive search terms to locate published literature on anticoagulation and spine surgery. Predefined inclusion and exclusion criteria were applied and data extraction was performed.

RESULTS

A total of 17 articles met the final inclusion criteria. Of these, 12 articles were retrospective chart reviews, 3 were prospective observational studies, and 2 were systematic reviews. Current practice suggests holding warfarin until international normalized ratio <1.4, anti-Xa drugs for 48 to 72 hours, 12 to 24 hours for low-molecular-weight heparin, and 4 to 24 hours for heparin, before surgery. Antiplatelet agents can be stopped for 1 to 3 days prior to operation (81-500 mg) but must be stopped for 1 week for doses >1 g/d. For Plavix, 5 to 7 days of discontinuation advised to prevent complications.

CONCLUSIONS

This review provides an overview of main anticoagulation agents seen in preoperative setting for spine patients. Although data is mixed and no true randomized control trials are available, there is growing evidence suggesting the aforementioned guidelines are needed to optimize anticoagulation in setting of spine surgery. Further studies are needed to elucidate risk of complications while operating under therapeutic levels of anticoagulation for a variety of comorbid conditions.

Perioperative management and monitoring of antiplatelet agents: a focused review on aspirin and P2Y12 inhibitors

Platelets play pivotal roles in hemostasis as well as pathological arterial thrombosis. The combination of aspirin and a P2Y₁₂ inhibitor has become the mainstay therapy in the ageing population with cardiovascular conditions, particularly during and after percutaneous coronary intervention. A number of novel P2Y₁₂ inhibitors has become available in the recent years, and they markedly vary in pharmacokinetic and pharmacodynamic properties. Perioperative physicians today face a challenge of preventing hemorrhage due to platelet inhibitors, while minimizing thrombotic risks. There are several point-of-care platelet function tests available in the peri-procedural assessment of residual platelet aggregation. However, these platelet function tests are not standardized in terms of sample processing, agonist type and potency as well as methods of detecting platelet activity. Understanding the differences in pharmacological properties of antiplatelet agents, principles of platelet function tests, and pertinent hemostatic strategies may be useful to anesthesiologists and intensivists who manage perioperative issues associated with antiplatelet agents. The objectives of this review are: 1) to discuss clinical data on aspirin and P2Y₁₂ inhibitors relating to perioperative bleeding, 2) to outline different features of point-of-care platelet function tests, and 3) to discuss therapeutic options for the prevention and treatment of bleeding associated with antiplatelet agents.

Knot Formation at Removal of an Epidural Catheter Placed Against Insertion Resistance Encountered at the Entrance of the Epidural Space

Knotting of an epidural catheter occurs very rarely with an estimated incidence of 0.0015%. We present a case of an epidural catheter knot formed at removal of an epidural catheter following a forceful insertion of the catheter against resistance met at the entrance of the epidural space during threading of the catheter through Tuohy needle placed uneventfully in a 65 year-old male patient undergoing epidural anesthesia. During removal of the epidural catheter, significant resistance was encountered on traction and it was found that approximately 1.5 ㎝ portion of the catheter had been retained within the patient's subcutaneous tissue. Firm traction was employed to withdraw the catheter against the resistance. The catheter was pulled out uneventfully from the patient. A knot estimated to be formed during removal of the catheter was observed at 0.6 ㎝ proximal to the catheter tip. No complications and side effects were noted until the patient's discharge.

Is early hip fracture surgery safe for patients on clopidogrel? Systematic review, meta-analysis and meta-regression

INTRODUCTION

Hip fracture is a common presentation in the elderly population, many of whom will be taking the antiplatelet clopidogrel, which has the potential to increase perioperative bleeding. The aim of this systematic review and meta-analysis was to answer the questions: (1) is early hip fracture surgery for patients on clopidogrel associated with worse postoperative outcomes compared to patients not on clopidogrel? (2) is early versus delayed surgery for these patients associated with worse postoperative outcomes?

METHODS

A systematic search was conducted of MEDLINE, EMBASE, Cinahl and AMED databases. Results from patients undergoing early surgery on clopidogrel were compared to a control group not taking clopidogrel. In addition, patients taking clopidogrel undergoing early and delayed surgery were compared.

RESULTS

For patients taking clopidogrel undergoing early surgery, there was no associated increase in overall mortality (OR 0.89; 95% CI: 0.58-1.38) or 30-day mortality (OR 1.10 95% CI: 0.48-2.54). However, there was an associated increase in blood transfusion (OR 1.41 95% CI: 1.00-1.99). There was an associated decreased length of stay in the early surgery versus delayed surgery group (weighted mean difference -7.09 days (95% CI: -10.14 to -4.04).

DISCUSSION

Early surgery appears safe for patients with hip fracture though there may be a small increase in the rate of blood transfusion. However, larger prospective trials are required to confirm these findings.

Pathophysiology of Cardiopulmonary Bypass

The techniques and equipment of cardiopulmonary bypass (CPB) have evolved over the past 60 years, and numerous numbers of cardiac surgical procedures are conducted around the world using CPB. Despite more widespread applications of percutaneous coronary and valvular interventions, the need for cardiac surgery using CPB remains the standard approach for certain cardiac pathologies because some patients are ineligible for percutaneous procedures, or such procedures are unsuccessful in some. The ageing patient population for cardiac surgery poses a number of clinical challenges, including anemia, decreased cardiopulmonary reserve, chronic antithrombotic therapy, neurocognitive dysfunction, and renal insufficiency. The use of CPB is associated with inductions of systemic inflammatory responses involving both cellular and humoral interactions. Inflammatory pathways are complex and redundant, and thus, the reactions can be profoundly amplified to produce a multiorgan dysfunction that can manifest as capillary leak syndrome, coagulopathy, respiratory failure, myocardial dysfunction, renal insufficiency, and neurocognitive decline. In this review, pathophysiological aspects of CPB are considered from a practical point of view, and preventive strategies for hemodilutional anemia, coagulopathy, inflammation, metabolic derangement, and neurocognitive and renal dysfunction are discussed.

Perioperative management of antiplatelet therapy

Worldwide, cardiovascular events represent the major cause of morbidity and mortality. A key role in the pathogenesis of these events is played by platelets. Interventional procedures, with placement of coronary and vascular stents, often represent the preferred therapeutic strategy. Antiplatelet medications are considered first-line therapy in preventing cardiovascular thrombotic events. A wide array of antiplatelet agents is available, each with different pharmacological properties. When patients on antiplatelet agents present for surgery, the perioperative team must design an optimal strategy to manage antiplatelet medications. Each patient is stratified according to risk of developing a cardiovascular thrombotic event and inherent risk of surgical bleeding. After risk stratification analysis, various therapeutic pathways include continuing or discontinuing all antiplatelet agents or maintaining one antiplatelet agent and discontinuing the other. This review focuses on the pharmacological and pharmacokinetic properties of both older and novel antiplatelet drugs, and reviews current literature and guidelines addressing options for perioperative antiplatelet management.

Is discontinuation of clopidogrel necessary for intracapsular hip fracture surgery? Analysis of 102 hemiarthroplasties

Background

An increasing number of elderly patients are managed with long-term antiplatelet therapy. Such patients often present with hip fracture requiring surgical intervention and may be at increased risk of perioperative bleeding and complications. The aim of this study was to ascertain whether it is necessary to stop clopidogrel preoperatively to avoid postoperative complications following hip hemiarthroplasty surgery in patients with intracapsular hip fracture.

Materials and methods

A retrospective review of 102 patients with intracapsular hip fracture with either perioperative clopidogrel therapy [clopidogrel group (CG)] or no previous clopidogrel exposure [no clopidogrel group (NCG)] who underwent hip hemiarthroplasty surgery was undertaken. Statistical comparison on pre- and postoperative haemoglobin, American Society of Anesthesiologists (ASA) grade, comorbidities, operative time, transfusion requirements, hospital length of stay (LOS), wound infection, haematoma and reoperation rate between the two groups was undertaken. Regression analysis was undertaken to ascertain the risk ratios (RR) of complications and transfusion associated with clopidogrel.

Results

There was no difference with respect to ASA grade, comorbidities (except cardiac comorbidities), pre- and postoperative haemoglobin levels, operation time, age or gender between the two groups. Four and two patients, respectively, required transfusion postoperatively in the CG and NCG (p = 0.37). There was no difference with respect to LOS, wound infection, haematoma or reoperation rate between the two groups postoperatively. The covariate-adjusted RR for complications and transfusion while being on clopidogrel were 0.43 [95 % confidence interval (CI) 0.07–2.60] and 3.96 (95 % CI 0.40–39.68), respectively.

Conclusion

Continuing clopidogrel therapy throughout the perioperative period in patients with intracapsular hip fracture is not associated with an increased risk of complications following hip hemiarthroplasty surgery.