Coagulation testing in the perioperative period

Preoperative investigation practices for elective surgical patients: clinical audit

BACKGROUND

The findings of pre-operative investigations help to identify risk factors that may affect the course of surgery or post-operative recovery by contributing to informed consent conversations between the surgical team and the patient, as well as guiding surgical and anesthetic planning. Certainly, preoperative tests are valuable when they offer additional information beyond what can be gathered from a patient's history and physical examination alone. Preoperative testing practices differ significantly among hospitals, and even within the same hospital, clinicians may have varying approaches to requesting tests. This study aimed to investigate preoperative testing practices and compare them with the latest guidelines from the National Institute for Health and Care Excellence (NICE).

METHODS

This three-month institutionally based study was carried out at the Debre Tabor Comprehensive Specialized Hospital from May 1 to July 30, 2023, including individuals aged 16 years and older who were not pregnant and had undergone elective surgery in the gynecological, orthopedic, and general units. Data on the sociodemographic characteristics, the existence of comorbidities, the invasiveness of surgery, and the tests taken into consideration by the guideline were gathered using a self-administered questionnaire. After rigorously analyzing and revising the results of preoperative investigation approaches, we compared them to the standard of recommendations. Moreover, the data was analyzed and graphically presented using Microsoft Excel 2013.

RESULTS

During the data collection period, 247 elective patients underwent general, orthopedic, and gynecological operations. The majority of patients, 107 (43.32%), were between the ages of 16 and 40 and had an American Society of Anesthesiologists (ASA) class one (92.71%). 350 investigations were requested in total. Of these, 71 (20.28%) tests were ordered without a justified reason or in contravention of NICE recommendations.

CONCLUSIONS

In our hospital's surgical clinical practice, unnecessary preoperative testing is still common, especially when it comes to organ function tests, electrocardiograms (ECGs), and complete blood counts (FBCs). When deciding whether preoperative studies are required, it is critical to consider aspects including a complete patient history, a physical examination, and the invasiveness of the surgery.

Consensus of the Brazilian association of hematology, hemotherapy and cellular therapy on patient blood management: Preoperative Clinical and Laboratory Assessment of the Patient

The preoperative clinical and laboratory evaluations of the patient is an essential step to ensure the safety and success of any surgical procedure. This assessment aims to identify any underlying medical conditions and risk factors and determine suitability for surgery. With this step, the medical team can adapt the care plan to meet each patient's specific needs, increasing the chances of a successful procedure. Good clinical assessment and comprehensive laboratory testing, when integrated into a Patient Blood Management approach, are invaluable in promoting safety of care, reducing transfusion risks, improving surgical outcomes, and optimizing resource utilization. This approach not only elevates the quality of care, but is also aligned with evidence-based practice and patient-centered principles, making it an essential component of the perioperative process.

Formulation, Characterization, and Optimization of a Topical Gel Containing Tranexamic Acid to Prevent Superficial Bleeding: In Vivo and In Vitro Evaluations

Objectives

Tranexamic acid (TXA) is used systemically to stop bleeding, but it can lead to thromboembolism. Trials have revealed the efficacy of topical TXA on local hemorrhages. However, there is a need for an efficient delivery system that can keep the drug at the site of action.

Materials and Methods

To develop a gel containing TXA (3%) optimized in terms of viscosity and dispersibility, the central composite design based on two factors-three levels [carbopol 940 and hydroxypropyl methylcellulose (HPMC), 1-1.5% and 1-2%, respectively] was applied. The spreadability and viscosity were assessed using glass slide and rheometer, respectively. To confirm the compatibility of TXA with the gel, fourier transform-infrared (FTIR) spectroscopy was performed. Drug content uniformity was analyzed by a spectroscopy method. An ex vivo mice model using Franz cells was applied to evaluate the permeation of TXA through the skin. To investigate the effect of topical TXA gel on bleeding time, IVY human method was performed.

Results

HPMC/carbopol 940 (1:1, w/w) gel showed the highest quality in terms of viscosity and dispersibility (3.982 ± 17.6 and 6.052 ± 3.562, respectively). FTIR absorption spectrum showed that all the TXA index peaks appeared without displacement. The complete-encapsulated TXA content was uniformly dispersed throughout the gel. In vitro TXA cumulative release reached 90% in 4 h. The bleeding time determined in vivo for TXA gel was significantly lower than that for TXA solution and control.

Conclusion

The results confirm the importance of further studies on this formulation as a potential medication to stop acute superficial bleeding.

Viscoelastometry to Manage Bleeding in Liver Disease

A state of "re-balanced haemostasis" describes complex coagulation changes that arise in patients with liver disease. Changes include alterations in procoagulant and anticoagulant proteins, platelets and von Willebrand factor, as well as the fibrinolytic system. Various circumstances including infection, trauma, or surgery may disrupt this balance and predispose an individual to bleeding or thrombosis. The prothrombin time, international normalised ratio, and activated partial thromboplastin time are conventional coagulation screening tests that are routinely employed by clinicians to investigate unexplained bleeding, monitor anticoagulation, and inform preoperative assessments of bleeding risk. These standard coagulation tests assess quantitative defects in procoagulant clotting factors and are insensitive to levels of natural anticoagulants, which together with procoagulant factors, are often perturbed in liver disease. Therefore, the prolongation of clotting times measured by these tests often does not reflect the multifaceted alterations of haemostasis in these patients. Viscoelastic testing (VET) provides a more encompassing assessment of clotting function by recording real-time viscoelastic changes in whole blood and includes parameters that provide information on coagulation factor function, platelet contribution to clot formation, as well as fibrinolysis. To date, VET has been employed to predict and inform transfusion support in obstetric, trauma, and cardiac surgical fields, and its use in patients undergoing liver transplantation is well established. The ability of VET to accurately predict bleeding risk and precisely guide transfusion algorithms for patients with liver disease undergoing other invasive procedures or experiencing bleeding complications has been the topic of research over the last decade. This review is a critical summary of this data and provides a detailed snapshot of the position of VET as a clinical tool in patients with liver disease.

Plasma Fibrinogen as a Predictor of Perioperative-Blood-Component Transfusion in Major-Nontraumatic-Orthopedic-Surgery Patients: A Cohort Study

There is a trend towards increased perioperative bleeding in patients with plasma fibrinogen levels < 200 mg/dL^-1. This study aimed to assess whether there is an association between preoperative fibrinogen levels and perioperative blood-product transfusion up to 48 h after major orthopedic surgery. This cohort study included 195 patients who underwent primary or revision hip arthroplasty for nontraumatic etiologies. Plasma fibrinogen, blood count, coagulation tests, and platelet count were measured preoperatively. A plasma fibrinogen level of 200 mg/dL^-1 was the cutoff value used to predict blood transfusion. The mean (SD) plasma fibrinogen level was 325 (83) mg/dL^-1. Only thirteen patients had levels < 200 mg/dL^-1, and only one of them received a blood transfusion, with an absolute risk of 7.69% (1/13; 95%CI: 1.37-33.31%). Preoperative plasma fibrinogen levels were not associated with the need for blood transfusion (p = 0.745). The sensitivity and the positive predictive value of plasma fibrinogen < 200 mg/dL^-1 as a predictor of blood transfusion were 4.17% (95%CI: 0.11-21.12%) and 7.69% (95%CI: 1.12-37.99%), respectively. Test accuracy was 82.05% (95%CI: 75.93-87.17%), but positive and negative likelihood ratios were poor. Therefore, preoperative plasma fibrinogen level in hip-arthroplasty patients was not associated with the need for blood-product transfusion.

Challenges in the Diagnosis and Management of Non-Severe Hemophilia

(1) Background: Mild and moderate hemophilia, synonymous with non-severe hemophilia (NSH), are of constant interest for the clinicians. Bleeding occurs usually after trauma, injury, surgery, or inhibitor development, sometimes leading to a shift of the clinical phenotype from mild to severe, even with life-threatening and unexpected outcomes. (2) Methods: We performed a retrospective observational study conducted on 112 persons with congenital coagulopathies, 26 of them with NSH, admitted to our clinic in the period 2000 to 2022. For the diagnosis, we used laboratory studies (complete blood cell count, coagulation assays, biochemistry, thromboelastography, genetic tests) and imaging investigations (X-ray, ultrasound, CT, MRI). We selected four cases confronted with pitfalls of diagnosis and evolution in order to illustrate the sometimes provocative field of NSH. (3) Results: Confronted with challenging cases with under-, missed or delayed diagnosis and severe consequences, we aimed at presenting four such selected cases with mild or moderate hemophilia, real pitfalls in our clinical activity. (4) Conclusions: In the field of NSH, if not timely recognized, tending sometimes to remain ignored by caregivers and patients themselves, we can be confronted with challenging diagnostic situations and life-threatening bleeds.

Recombinant Destabilase from Hirudo medicinalis Is Able to Dissolve Human Blood Clots In Vitro

Leeches are amazing animals that can be classified as conditionally poisonous animals since the salivary cocktail they produce is injected directly into the victim, and its components have strictly defined biological purposes, such as preventing blood clot formation. Thrombolytic drugs are mainly aimed at treating newly formed blood clots. Aged clots are stabilized by a large number of isopeptide bonds that prevent the action of thrombolytics. These bonds are destroyed by destabilase, an enzyme of the leech’s salivary glands. Here, we conducted a pilot study to evaluate the feasibility and effectiveness of the use of destabilase in relation to blood clots formed during real pathological processes. We evaluated the isopeptidase activity of destabilase during the formation of a stabilized fibrin clot. We showed that destabilase does not affect the internal and external coagulation cascades. We calculated the dose–response curve and tested the ability of destabilase to destroy isopeptide bonds in natural blood clots. The effect of aged and fresh clots dissolving ability after treatment with destabilase coincided with the morphological characteristics of clots during surgery. Thus, recombinant destabilase can be considered as a potential drug for the treatment of aged clots, which are difficult to treat with known thrombolytics.

A single-institution retrospective study of causes of prolonged prothrombin time and activated partial thromboplastin time in the outpatient setting

INTRODUCTION

An algorithmic approach, termed the prolonged clot time profile (PROCT), consisting of initial screening with prothrombin time (PT) and activated partial thromboplastin time (aPTT), reflexive mixing studies if indicated, and follow-up assays depending on initial testing results, offers an efficient approach to delineate the etiology of a prolonged PT/aPTT. Herein, we present the outcomes of the PROCT in the outpatient setting.

METHODS

In this retrospective study, we reviewed medical records of consecutive outpatients who had prolonged PT and/or aPTT noted in the routine coagulation laboratory and who had PROCT ordered in our institutional Special Coagulation Laboratory between 2010 and 2017.

RESULTS

One hundred and six patients, median age 55 years (IQR 30-67), met our study criteria. Twenty-nine patients had normal PT/aPTT, while 77 had persistent abnormalities and underwent reflexive testing. A prolonged PT, aPTT, or PT and aPTT was noted in 27 (35%), 27 (35%), and 23 (30%) respectively. Forty-nine (64%) had an acquired condition, 17 (22%) had a congenital condition, 7 (9%) had unclear etiology, and 4 (5%) were the result of laboratory artifact. The most common known cause of an isolated prolonged PT in our study was vitamin K deficiency in 8 (10%), the most common cause of an isolated prolonged aPTT was lupus anticoagulant in 4 (5%), and the most common cause of prolonged PT and aPTT was liver disease in 11 (14%).

CONCLUSION

Prolonged PT/aPTT have a wide range of causes, including artifactual prolongation or abnormalities in secondary hemostasis due to both inherited and acquired conditions.

Pathogen reduction of whole blood: Supplementing fibrinogen partly corrects clot formation in a massive transfusion model

BACKGROUND

The use of whole blood (WB) to treat trauma patients is becoming more common. Similar to the treatment of individual components, pathogen inactivation (PI) technologies are available to treat WB. The impact of PI on WB function is not well understood. This study investigated the impact of PI of WB with riboflavin/ultraviolet (UV) light on its hemostatic function by modeling transfusion scenarios for trauma patients and assessing transfusion efficacy by rotational thromboelastometry (ROTEM). As fibrinogen is affected by PI of WB, the effect of fibrinogen supplementation commonly used in trauma patients was also analyzed in this model.

STUDY DESIGN AND METHODS

Trauma transfusion scenarios were simulated by mixing untreated WB or WB treated with the Mirasol PI technology (riboflavin/UV) in different ratios with hemodiluted blood, and the thromboelasticity was monitored by ROTEM. The impact of supplementation with the fibrinogen concentrate RiaSTAP was investigated in this model.

RESULTS

Pathogen-inactivated WB (PI-WB) showed decreased activity in the hemostatic profile compared to the untreated control. Hemodiluted blood at a hematocrit (hct) of 20%, which was reconstituted with PI-WB or untreated WB, exhibited increased alpha values, maximum clot firmness, and clot formation time. Simulating transfusion scenarios by blood replacement with PI-WB resulted in a significant difference in ROTEM parameters between reconstituted PI-treated and -untreated WB (p ≥ .05). The effect of PI treatment waned when PI-WB was enriched with fibrinogen.

CONCLUSION

ROTEM investigations suggest that PI treatment has a negative impact on WB clot formation unless fibrinogen supplementation is used.

Coagulation Profile as a Significant Risk Factor for Short-Term Complications and Mortality after Anterior Cervical Discectomy and Fusion

BACKGROUND

Cervical degenerative disc disease is the most common indication for anterior cervical discectomy and fusion. Given the possible complications, patients are stratified before anterior cervical discectomy and fusion by preoperative risk factors to optimize treatment. One preoperative factor is a patient's coagulation profile.

METHODS

The American College of Surgeons-National Surgical Quality Improvement Database was used to identify patient preoperative coagulation profile and postoperative complications. By generating binary logistic regression models, each of the 4 abnormal coagulation categories (bleeding disorder, low platelet count, high partial thromboplastin time, and high international normalized ratio [INR]) were analyzed for their independent impact on increased risk for complications compared with the control cohort.

RESULTS

A total of 61,977 patients were assessed. The most common abnormal coagulation was abnormal platelet count (n = 2149). The most common postoperative outcome was an extended length of hospital stay among patients with an abnormal coagulation profile relative to the control cohort. After multivariate analysis, patients with an abnormal INR (odds ratio, 2.2 [1.3-3.8]; P = 0.003) or abnormal platelet count (odds ratio, 1.5 [1.2-2.1]; P = 0.003) had a higher chance of having an extended length of hospital stay relative to patients having a normal coagulation profile. Having an abnormal INR was found to be associated with an increased risk for having "Any complication."

CONCLUSIONS

Our results show significant differences in the incidence rates of a multitude of complications among the 5 groups based on univariate analysis. Patients with any abnormal coagulation disorder had increased rates of developing any complication or having an extended length of hospital stay.

Technology Advancements in Blood Coagulation Measurements for Point-of-Care Diagnostic Testing

In recent years, blood coagulation monitoring has become crucial to diagnosing causes of hemorrhages, developing anticoagulant drugs, assessing bleeding risk in extensive surgery procedures and dialysis, and investigating the efficacy of hemostatic therapies. In this regard, advanced technologies such as microfluidics, fluorescent microscopy, electrochemical sensing, photoacoustic detection, and micro/nano electromechanical systems (MEMS/NEMS) have been employed to develop highly accurate, robust, and cost-effective point of care (POC) devices. These devices measure electrochemical, optical, and mechanical parameters of clotting blood. Which can be correlated to light transmission/scattering, electrical impedance, and viscoelastic properties. In this regard, this paper discusses the working principles of blood coagulation monitoring, physical and sensing parameters in different technologies. In addition, we discussed the recent progress in developing nanomaterials for blood coagulation detection and treatments which opens up new area of controlling and monitoring of coagulation at the same time in the future. Moreover, commercial products, future trends/challenges in blood coagulation monitoring including novel anticoagulant therapies, multiplexed sensing platforms, and the application of artificial intelligence in diagnosis and monitoring have been included.

Methanolic root extract of Codonopsis clematidea prevents hypoxia induced procoagulant state by inhibition of GPIb receptor regulated Lyn kinase activation

BACKGROUND

The prevalence of procoagulant state under prolonged hypoxic exposures and the complications and lack of specificity associated with use of existing anti-thrombotic agents have necessitated the search for safer and natural therapeutics. Codonopsis, a widely studied medicinal herb, has been reported to decrease whole blood viscosity but the bioactive ingredients involved, and their mechanism of action therein however remain to be investigated.

PURPOSE

The present study aimed at evaluating the efficacy of C. clematidea root extract and mechanism of action of its bioactive constituent flavonoid, Kaempferol, in ameliorating hypobaric hypoxia induced procoagulant state.

METHODS

Fingerprinting analysis of methanolic extract of C. clematidea root was performed by RP-HPLC. In vitro toxicity study was conducted using HUVEC cell line and in vivo acute and sub-acute toxicity were done according to OECD guidelines (section-4, number-420 and 407 respectively). Adult male Sprague-Dawley rats weighing 230-250 g were exposed to global hypoxia simulating an altitude of 7600 m (282 mmHg), in animal decompression chamber for 3, 7, 14 and 21 days for in vivo studies. Dose optimisation of the extract was done by quantification of Thromboxane A2 in the serum of hypoxic rats. C. clematidea root extract was also evaluated for its in vitro and in vivo antioxidant properties. Procoagulant changes were studied by biochemical plasma coagulation assays and expression analysis of the signalling molecules of the platelet activation cascade like vWF, platelet activation marker CD41, GpIb-IX-V (CD42), Lyn kinase, p-PI3K, p-ERK and p-PLCγ were conducted to investigate C. clematidea mediated signalling mechanisms.

RESULTS

Methanolic extract of C. clematidea root showed improved antioxidant status and improvement in bleeding time and in vitro coagulation assays like pT, aPTT, INR. Decreased concentrations of D-Dimers along with that of platelet activation marker CD41 and serum concentration of Thromboxane A2 were observed in C. clematidea root extract supplemented hypoxic animals. Phosphorylation of Lyn kinase, was reduced despite increase in concentration of activating ligand vWF.

CONCLUSION

C. clematidea root extract was effective in preventing hypoxia induced platelet activation and resultant procoagulant state by inhibiting Lyn kinase, a serine threonine kinase effector of vWF signalling cascade.

Current transfusion practices of anesthesiologists in a major city in South India

BACKGROUND AND AIMS

Allogenic blood transfusion is a double edged sword with a delicate balance between benefits and risks. There is heavy use of blood products in the perioperative setting mostly initiated by anesthesiologists. Limited research has been done in evaluating the transfusion practices of anesthesiologists especially in Indian setting. We conducted a survey among the anesthesiologists in our city to assess their blood transfusion practices, to evaluate the level of adherence to principles of Patient Blood Management and to look for innovative strategies to improve the perioperative transfusions.

METHODS

A validated questionnaire with four sets of questions was distributed among the practitioners in the Indian Society of Anaesthesiologists city branch and the responses were collected and analysed. The first and second parts were structured to assess the current blood transfusion practices. The third part evaluated the keenness of participants in further updating their practices as per the recommended protocols of patient blood management. The last part assessed how the participants would act in a given clinical scenario. Statistical analysis was done using Statistical Package for the Social Sciences version 21. Results are expressed in numbers and percentages.

RESULTS

Moderate preoperative anemia was acceptable to majority of the responders. There was a high demand for continuing medical education in transfusion medicine and for formulating Indian guidelines for perioperative transfusion. The clinical scenarios demonstrated the restrictive transfusion strategy of the majority of our anesthesiologists. The lack of institutional protocols and blood transfusion committees was also seen.

CONCLUSION

The restrictive strategy of our practitioners was an encouraging finding. There is lack of uniformity in patient blood management services. Regular educational interventions are needed to update the clinicians. Formulation and implementation of institutional protocols for perioperative blood transfusion is mandatory.

Effectiveness and safety of tranexamic acid in total joint arthroplasty

Total joint arthroplasty is associated with significant blood loss, that could result in the need of blood transfusions. Several techniques are being utilised to limit the volume of blood loss, in order to avoid transfusion. In this review, we look at blood loss in total joint arthroplasty and the perioperative strategies to limit the loss of blood. With the use of tranexamic acid gaining popularity, we analyse the published literature on its use in patients undergoing total joint arthroplasty. We have found that published studies favour using tranexamic acid in total joint arthroplasty as a safe and effective method of reducing blood loss.

Routine Preoperative Coagulation Tests in Children Undergoing Elective Surgery or Invasive Procedures: Are They Still Necessary?

Introduction:

Preoperative coagulation screening tests in pediatric patients was once routine clinical practice globally and still used as standard practice in some countries before surgical procedures to assess of perioperative bleeding risk.

Objective:

The study aimed to evaluate unselected routine preoperative coagulation testing in children undergoing elective or invasive surgery to predict abnormal perioperative bleeding. The study also aimed to provide a rational approach of determining bleeding and family history of coagulation disorders as a predictive risk for bleeding.

Methods:

This retrospective study conducted between 2014 and 2015 (1 year) on normal healthy children aged under 15 years admitted to the hospitals for elective mild to intermediate surgery or invasive procedures. We reviewed and collected the details of the clinical history, previous surgery, trauma, family history, detail of anti-thrombotic medication and coagulation tests performed (prothrombin time (PT), the activated partial prothrombin time (APTT), and international normalized ratio (INR)) at the time of admission.

Results:

Among 2078 cases, 1940 cases had normal coagulation tests (93.4%), 77 cases had abnormal coagulation results (3.7%), and 61 patients underwent surgery without preoperative coagulation screening (2.9%). In 15 of 77 patients, coagulation tests were normal on repeat testing. A total of 52 were confirmed to have abnormal screening testing. Among these 52 cases, 45 had normal factors assay; where seven patients had abnormal factors assay. Postoperative bleeding occurred only in three cases (0.14%), two cases due to surgical procedures with normal preoperative testing and one due to hemophilia A which was detected postoperatively as no preoperative testing was performed.

Conclusions:

Routine coagulation screening before surgery or invasive procedures to predict perioperative bleeding in unselected patients is not recommended. Our study emphasizes that selective preoperative testing is more appropriate. Selective criteria for consideration of the latter includes physical examination, type of surgery, family and bleeding history, and concomitant use of antiplatelet and anti-thrombotic therapy.

Experimental effect of different dilutions of blood with human plasma protein fraction and large dose factor one on blood coagulation and chemistry in vitro

Background and Aims:

Human plasma protein fraction 5% (PPF5%) is an albumin-based colloid used to expand the plasma volume during volume deficiency. The current basic medical experimental study assessed in vitro coagulation of PPF5% solution and its effects on blood coagulation and chemistry.

Methods:

The study involved 20 volunteers, and each volunteer donated 20–50 ml of fresh blood. Three dilutions of blood with PPF5% dilutions were prepared (30, 50, and 70%). The fibrinogen dose required to correct coagulation in the 50% diluted samples was assessed (two doses used). The thromboelastogram (TEG) measured the haemostatic parameters (fibrinogen level, initiation of coagulation [R time], kinetics [K], acceleration of coagulation [α angle], maximum amplitude [MA] and coagulation index [CI]), and the ABL gas analyser measured the blood chemistry changes.

Results:

All dilutions showed significant TEG and blood chemistry changes when compared to controls. The two doses of fibrinogen corrected the clot formation speed with no significant difference in speed between the two doses. Acidosis measured by the strong ion gap (SID) and pH were significant for all dilutions when compared with the baseline. The 30% dilution remained within the lower normal acceptable value while 50% dilution was beyond the critical normal values.

Conclusion:

In vitro PPF5% to replace blood loss up to 50% dilution did not have significant coagulation and blood chemistry effects while coagulopathy should be expected in extreme dilutions (70%). Fibrinogen in a dose equivalent to 4 gm/70 kg adult improved clot strength at 50% dilution.

Enzymatic and chemical synthesis of new anticoagulant peptides

In this study we report the enzymatic synthesis of N-α-[Carbobenzyloxy]-Tyr-Gln-Gln (Z-YQQ), a new anticoagulant tripeptide. It was obtained using phytoproteases from the stems and petioles of Asclepias curassavica L. as catalyst in an aqueous-organic biphasic system formed by 50% (v/v) ethyl acetate and 0.1 M Tris-HCl buffer pH 8. The resulting peptide was compared with the analogous peptide Tyr-Gln-Gln (YQQ) produced by solid-phase chemical synthesis. The in vitro anticoagulant activity of the aforementioned peptides was determined using Wiener Lab Test (Wiener, Argentina). The toxicological activity of the peptides was also determined. The enzymatically synthesized Z-YQQ peptide acted on the extrinsic pathway of the coagulation cascade, delaying the conversion time of prothrombin to thrombin and fibrinogen to fibrin by 136 and 50%, respectively, with respect to the controls. The chemically synthesized YQQ peptide acted specifically on the intrinsic pathway of the coagulation cascade, affecting factors VIII, IX, XI, and XII from such cascade, and increasing the coagulation time by 105% with respect to the control. The results suggest that two new anticoagulant peptides (Z-YQQ and YQQ) can be useful for safe pharmaceutical applications. Nevertheless, some aspects related to peptide production should be optimized. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1093-1101, 2018.

Design and Utility of a Point-of-Care Microfluidic Platform to Assess Hematocrit and Blood Coagulation

Purpose—

To develop a small volume whole blood analyzer capable of measuring the hematocrit and coagulation kinetics of whole blood.

Methods and Results—

A co-planar microfluidic chamber designed to facilitate self-driven capillary action across an internal electrical chip was developed and used to measure the electric parameters of whole human blood that had been anticoagulated or allowed to clot. To promote blood clotting, select chip surfaces were coated with a prothrombin time (PT) reagent containing lipidated tissue factor (TF), which activates the extrinsic pathway of coagulation to promote thrombin generation and fibrin formation. Whole human blood was added to the microfluidic device, and voltage changes within the platform were measured and interpreted using basic resistor-capacitor (RC) circuit and fluid dynamics theory. Upon wetting of the sensing zone, a circuit between two co-planar electrodes within the sensing zone was closed to generate a rapid voltage drop from baseline. The voltage then rose due to sedimentation of red blood cells (RBC) in the sensing zone. For anticoagulated blood samples, the time for the voltage to return to baseline was dependent on hematocrit. In the presence of coagulation, the initiation of fibrin formation in the presence of the PT reagent prevented the return of voltage to baseline due to the reduced packing of RBCs in the sensing zone.

Conclusions—

The technology presented in this study has potential for monitoring the hematocrit and coagulation parameters of patient samples using a small volume of whole blood, suggesting it may hold clinical utility as a point-of-care test.

Reducing the use of inappropriate coagulation testing in emergency general surgical patients

Background and aims

Indiscriminate coagulation testing in emergency general surgical patients can lead to inappropriate delay in surgery, cause unnecessary concern and is associated with significant cost. The British Committee for Standards in Haematology recommends against coagulation testing to predict peri-operative bleeding risk in unselected patients. Our aim was to assess the appropriateness of coagulation tests performed in emergency general surgical patients and evaluate the effect of a series of educational interventions on clinical practice.

Methods and results

Appropriate indications for performing coagulation testing included a positive bleeding history, the presence of liver disease/cholestasis, sepsis or use of anticoagulants. Initial data on 142 patients were collected over 2 weeks of receiving. Following analysis, indications for appropriate coagulation testing were highlighted and data were collected on a further 190 patients. Comparing the audit cycles, we observed a decrease in the proportion of patients who underwent routine testing (49.3% vs 32.6%; p = 0.002) and inappropriate testing (67% of tests vs 34% of tests; p < 0.001). Despite being highlighted, there was no evidence of improved documentation of bleeding histories on admission.

Conclusions

This observational study suggests that simple educational messages can reduce the inappropriate use of coagulation screening tests in general surgical emergencies. This seems to result from clarification of the appropriate surgical indications for coagulation testing in this group.

Value of Routine Preoperative Tests for Coagulation Before Elective Cranial Surgery. Results of an Institutional Audit and a Nationwide Survey of Neurosurgical Centers in Pakistan

BACKGROUND

Routine preoperative blood testing has become a dogma. The general practice is to order preoperative workup as a knee-jerk response rather than individualize it for each patient. The fact that the bleeding brain tends to swell, which coupled with limited options for proximal control, packing, and overall hemostasis, leads to an overemphasis on the preoperative coagulation profile.

MATERIAL AND METHODS

This is a retrospective review of the medical records of patients admitted at Aga Khan University Hospital from January 2010 to December 2015 for an elective craniotomy. The hospital registry was used to identify files for review. Data were collected on a predefined proforma. A nationwide survey was performed, and 30 neurosurgery centers were contacted across Pakistan to confirm the practice of preoperative workup.

RESULTS

The survey revealed that all centers had a similar practice of preoperative workup. This included complete blood count, serum electrolytes, and coagulation profile, including prothrombin time, activated partial thromboplastin time (aPTT), and international normalized ratio (INR). A total of 1800 files were reviewed. Nine (0.5%) patients were found to have deranged clotting profile without any predictive history of clotting derangement; 56% were male and 44% were female. Median age was 32 years with an interquartile range of 27 years. Median aPTT was (40.8 with 20.8 IQR). Median INR was (1.59 with 0.48 IQR). Median blood loss was (400 with 50 IQR). No significant association between coagulation profile (aPTT, INR) and blood loss was found (P = 0.85, r = -0.07).

CONCLUSIONS

We conclude that patients without a history of coagulopathy and normal physical examination do not require routine coagulation screening before elective craniotomy.

Characterization of a novel selective factor Xa inhibitor, DJT06001, which reduces thrombus formation with low risk of bleeding

Factor Xa (FXa) is a serine protease that plays key roles in linking the intrinsic and extrinsic coagulation pathways to the final common pathway. DJT06001 is an oral, highly specific and direct FXa inhibitor for the prevention and treatment of thromboembolic diseases. We characterized the compound in vitro and studied its in vivo activity in rat thrombosis models, as well as bleeding risk and Pharmacokinetics and Pharmacodynamics (PK/PD) relationship. DJT06001 inhibited free FXa with an inhibitory constant (Ki) of 0.99 nM, and exhibited >10000-fold selectivity for FXa than for other related serine proteases. DJT06001 concentration-dependently inhibited FXa activity in the prothrombinase complex with an IC₅₀ of 2.53 nM. The concentrations for DJT06001 to double the prothrombin time (PT) and activated partial thromboplastin time (APTT) were 0.74 and 0.57 μM, respectively. Importantly, DJT06001 did not impair platelet aggregation induced by ADP, platelet activating factor (PAF) and collagen. Furthermore, DJT06001 inhibited thrombus formation in rat thrombosis models in a dose dependent manner. And in rat tail bleeding risk test, it caused less bleeding than rivaroxaban at doses that achieve the same antithrombotic effect. PK/PD studies further demonstrated that there was a good correlation between the plasma concentrations of DJT06001and its inhibition of plasma FXa activity and prolongation of PT. In conclusion, DJT06001 was shown to be a potent and specific FXa inhibitor with excellent PK/PD profiles and it could be developed as a new anticoagulant for the management of thromboembolic diseases.

Comparison of two pediatric cases requiring the use of bivalirudin during cardiopulmonary bypass

Introduction:

Comparison of two pediatric cases at our institution that utilized bivalirudin for anticoagulation on cardiopulmonary bypass (CPB); a bilateral lung transplant (BLT) and a ventricular assist device (VAD) implantation.

Methods:

The same bivalirudin protocol was utilized in both cases with an initial bolus of 1 mg/kg administered by the anesthesia team, a 50 mg bolus in the pump prime at the time of the initial patient bolus and an initial infusion rate of 2.5 mg/kg/h, with titration as needed during CPB to maintain kaolin-activated clotting time (K-ACT) values >400 s.

Results:

The BLT experienced high K-ACT levels (>720 s) for the majority of the case despite decreasing the bivalirudin infusion rate to 0.5 mg/kg/h. The VAD implantation case required the bivalirudin infusion rate to be increased to 5.0 mg/kg/h throughout the case due to low K-ACTs.

Conclusion:

The literature strongly supports a specific infusion rate1–7 (2.5 mg/kg/h) for bivalirudin anticoagulation during extracorporeal circulation. Clinicians must consider the loss of clotting factors and the administration of blood products while adjusting the bivalirudin infusion during bypass. We have now elected to maintain an infusion rate of ≥0.5 mg/kg/h for bivalirudin anticoagulation at our center, based on institutional experience, though consideration for a higher infusion rate for an added margin of safety should be considered. It is imperative to have a well-developed protocol for the management of these cardiopulmonary bypass patients and we offer our one-page timeline of events to help guide other pediatric centers looking to use bivalirudin anticoagulation.

Strategies for Intravenous Fluid Resuscitation in Trauma Patients

Intravenous fluid management of trauma patients is fraught with complex decisions that are often complicated by coagulopathy and blood loss. This review discusses the fluid management in trauma patients from the perspective of the developing world. In addition, the article describes an approach to specific circumstances in trauma fluid decision-making and provides recommendations for the resource-limited environment.

Perioperative Approach to Anticoagulants and Hematologic Disorders

Hematologic disorders and patients on anticoagulants or at risk for venous thromboembolism encompass a broad array of diagnoses, which can potentially complicate perioperative planning and management. This article addresses both bleeding and clotting concerns as well as special hematologic issues.