Assessment of Hemostasis

2017 ◽  
Author(s):  
Phillip M. Kemp Bohan ◽  
Martin A Schreiber
Keyword(s):  
Laboratory Tests ◽  
Blood Clot ◽  
Preoperative Evaluation ◽  
Test Results ◽  
Biological Mechanisms ◽  
Hemostatic System ◽  
Coagulation Tests ◽  
Treatment Plans ◽  
Timely Fashion ◽  
Key Words Coagulation

Hemostasis is the collection of biological mechanisms responsible for bleeding cessation following surgical procedures or trauma. Congenital and acquired disorders affecting any element of the hemostatic system can result in a spectrum of bleeding pathologies ranging from inability to form stable blood clot to the pathologic propagation of blood clot outside the area of injury. Assessing the hemostatic system in an accurate and timely fashion is critical for detection of these disorders. This review briefly covers the mechanisms of primary and secondary hemostasis before comprehensively exploring the approach to preoperative evaluation of hemostasis, the strengths and weaknesses of commonly used laboratory tests of coagulation, the interpretation of test results, and the management of patients found to have abnormal hemostatic systems. Figures detail the mechanisms of hemostasis and the important features of viscoelastic testing. Tables explain the parameters frequently measured in viscoelastic testing and propose potential treatment plans based on test findings.   Key words: coagulation; conventional coagulation tests; hemostasis; thromboelastography; thromboelastometry 

Assessment of Hemostasis

2017 ◽  
Author(s):  
Phillip M. Kemp Bohan ◽  
Martin A Schreiber
Keyword(s):  
Laboratory Tests ◽  
Blood Clot ◽  
Preoperative Evaluation ◽  
Test Results ◽  
Biological Mechanisms ◽  
Hemostatic System ◽  
Coagulation Tests ◽  
Treatment Plans ◽  
Timely Fashion ◽  
Key Words Coagulation

Hemostasis is the collection of biological mechanisms responsible for bleeding cessation following surgical procedures or trauma. Congenital and acquired disorders affecting any element of the hemostatic system can result in a spectrum of bleeding pathologies ranging from inability to form stable blood clot to the pathologic propagation of blood clot outside the area of injury. Assessing the hemostatic system in an accurate and timely fashion is critical for detection of these disorders. This review briefly covers the mechanisms of primary and secondary hemostasis before comprehensively exploring the approach to preoperative evaluation of hemostasis, the strengths and weaknesses of commonly used laboratory tests of coagulation, the interpretation of test results, and the management of patients found to have abnormal hemostatic systems. Figures detail the mechanisms of hemostasis and the important features of viscoelastic testing. Tables explain the parameters frequently measured in viscoelastic testing and propose potential treatment plans based on test findings.   Key words: coagulation; conventional coagulation tests; hemostasis; thromboelastography; thromboelastometry 

Comparison of Thrombelastography with Common Coagulation Tests

1981 ◽  
Vol 46 (04) ◽  
pp. 752-756 ◽  
Author(s):  
L Zuckerman ◽  
E Cohen ◽  
J P Vagher ◽  
E Woodward ◽  
J A Caprini
Keyword(s):  
Laboratory Tests ◽  
Clinical Utility ◽  
Blood Clotting ◽  
Strong Relationship ◽  
Relative Strength ◽  
Additional Information ◽  
Patients With Cancer ◽  
Two Samples ◽  
Coagulation Tests ◽  
Common Laboratory

SummaryThrombelastography, although proven as a useful research tool has not been evaluated for its clinical utility against common coagulation laboratory tests. In this study we compare the thrombelastographic measurements with six common tests (the hematocrit, platelet count, fibrinogen, prothrombin time, activated thromboplastin time and fibrin split products). For such comparisons, two samples of subjects were selected, 141 normal volunteers and 121 patients with cancer. The data was subjected to various statistical techniques such as correlation, ANOVA, canonical and discriminant analysis to measure the extent of the correlations between the two sets of variables and their relative strength to detect blood clotting abnormalities. The results indicate that, although there is a strong relationship between the thrombelastographic variables and these common laboratory tests, the thrombelastographic variables contain additional information on the hemostatic process.

Predicting abnormal laboratory blood test results in the intensive care unit using novel features based on information theory and historical conditional probability (Preprint)

2021 ◽  
Author(s):  
Camilo E. Valderrama ◽  
Daniel J. Niven ◽  
Henry T. Stelfox ◽  
Joon Lee
Keyword(s):  
Machine Learning ◽  
Intensive Care ◽  
Conditional Probability ◽  
Blood Test ◽  
Laboratory Tests ◽  
Conditional Entropy ◽  
Admission Diagnosis ◽  
Test Results ◽  
Abnormal Laboratory ◽  
Blood Tests

BACKGROUND Redundancy in laboratory blood tests is common in intensive care units (ICU), affecting patients' health and increasing healthcare expenses. Medical communities have made recommendations to order laboratory tests more judiciously. Wise selection can rely on modern data-driven approaches that have been shown to help identify redundant laboratory blood tests in ICUs. However, most of these works have been developed for highly selected clinical conditions such as gastrointestinal bleeding. Moreover, features based on conditional entropy and conditional probability distribution have not been used to inform the need for performing a new test. OBJECTIVE We aimed to address the limitations of previous works by adapting conditional entropy and conditional probability to extract features to predict abnormal laboratory blood test results. METHODS We used an ICU dataset collected across Alberta, Canada which included 55,689 ICU admissions from 48,672 patients with different diagnoses. We investigated conditional entropy and conditional probability-based features by comparing the performances of two machine learning approaches to predict normal and abnormal results for 18 blood laboratory tests. Approach 1 used patients' vitals, age, sex, admission diagnosis, and other laboratory blood test results as features. Approach 2 used the same features plus the new conditional entropy and conditional probability-based features. RESULTS Across the 18 blood laboratory tests, both Approach 1 and Approach 2 achieved a median F1-score, AUC, precision-recall AUC, and Gmean above 80%. We found that the inclusion of the new features statistically significantly improved the capacity to predict abnormal laboratory blood test results in between ten and fifteen laboratory blood tests depending on the machine learning model. CONCLUSIONS Our novel approach with promising prediction results can help reduce over-testing in ICUs, as well as risks for patients and healthcare systems. CLINICALTRIAL N/A

Preoperative evaluation of coagulation status in neuromodulation patients

2021 ◽  
pp. 1-7
Author(s):  
Amir Hadanny ◽  
Zachary T. Olmsted ◽  
Anthony M. Marchese ◽  
Kyle Kroll ◽  
Christopher Figueroa ◽  
...  
Keyword(s):  
Laboratory Tests ◽  
Preoperative Evaluation ◽  
Preoperative Assessment ◽  
New Anticoagulants ◽  
Laboratory Values ◽  
Normal Ranges ◽  
Hematological Analysis ◽  
Coagulation Status ◽  
Pump Implantation ◽  
Deep Brain

OBJECTIVE The incidence of hemorrhage in patients who undergo deep brain stimulation (DBS) and spinal cord stimulation (SCS) is between 0.5% and 2.5%. Coagulation status is one of the factors that can predispose patients to the development of these complications. As a routine part of preoperative assessment, the authors obtain prothrombin time (PT), partial thromboplastin time (PTT), and platelet count. However, insurers often cover only PT/PTT laboratory tests if the patient is receiving warfarin/heparin. The authors aimed to examine their experience with abnormal coagulation parameters in patients who underwent neuromodulation. METHODS Patients who underwent neuromodulation (SCS, DBS, or intrathecal pump implantation) over a 9-year period and had preoperative laboratory values available were included. The authors determined abnormal values on the basis of a clinical protocol utilized at their practice, which combined the normal ranges of the laboratory tests and clinical relevance. This protocol had cutoff values of 12 seconds and 39 seconds for PT and PTT, respectively, and < 120,000 platelets/μl. The authors identified risk factors for these abnormalities and described interventions. RESULTS Of the 1767 patients who met the inclusion criteria, 136 had abnormal preoperative laboratory values. Five of these 136 patients had values that were misclassified as abnormal because they were within the normal ranges at the outside facility where they were tested. Fifty-one patients had laboratory values outside the ranges of our protocol, but the surgeons reviewed and approved these patients without further intervention. Of the remaining 80 patients, 8 had known coagulopathies and 24 were receiving warfarin/heparin. The remaining 48 patients were receiving other anticoagulant/antiplatelet medications. These included apixaban/rivaroxaban/dabigatran anticoagulants (n = 22; mean ± SD PT 13.7 ± 2.5 seconds) and aspirin/clopidogrel/other antiplatelet medications (n = 26; mean ± SD PT 14.4 ± 5.8 seconds). Eight new coagulopathies were identified and further investigated with hematological analysis. CONCLUSIONS New anticoagulants and antiplatelet medications are not monitored with PT/PTT, but they affect coagulation status and laboratory values. Although platelet function tests aid in a subset of medications, it is more difficult to assess the coagulation status of patients receiving novel anticoagulants. PT/PTT may provide value preoperatively.

scholarly journals Utilisation of laboratory test results for patient management by clinicians at two large referral hospitals in Zambia

2020 ◽  
Author(s):  
Sabe Mwape ◽  
Victor Daka ◽  
Scott Matafwali ◽  
Kapambwe Mwape ◽  
Jay Sikalima ◽  
...  
Keyword(s):  
Teaching Hospital ◽  
Laboratory Tests ◽  
Patient Management ◽  
Medical Laboratory ◽  
Test Results ◽  
Cross Sectional ◽  
Childrens Hospital ◽  
Laboratory Test Results ◽  
Laboratory Results ◽  
Referral Hospitals

Background Medical laboratory diagnosis is a critical component of patient management in the healthcare setup. Despite the availability of laboratory tests, clinicians may not utilise them to make clinical decisions. We investigated utilsation of laboratory tests for patient management among clinicians at Ndola Teaching Hospital (NTH) and Arthur Davison Childrens Hospital (ADCH), two large referral hospitals in the Copperbelt Province, Ndola, Zambia. Method We conducted a descriptive cross-sectional study among clinicians. The study deployed self-administered questionnaires to evaluate clinician utilisation, querying and confidence in laboratory results. Additional data on demographics and possible laboratory improvements were also obtained. Data were entered in Microsoft excel and exported to SPSS version 16 for statistical analysis. Results Of the 80 clinicians interviewed, 96.2% (77) reported using laboratory tests and their results in patient management. 77.5% (62) of the clinicians indicated they always used laboratory results to influence their patient management decisions. Of the selected laboratory tests, clinicians were more confident in using haemoglobin test results (91.2%). There was no statistically significant association between the clinicians gender or qualification and use of test results in patient management. Conclusion Our findings show that despite the majority querying laboratory results, most of the clinicians use laboratory results for patient management. There is need for interactions between the laboratory and clinical area to assure clinician confidence in laboratory results. Key words: utilisation, clinicians, laboratory tests, Ndola Teaching Hospital, Arthur Davison Childrens Hospital

Study of the effect of test parameters on the assessment of steel resistance to carbon dioxide corrosion

2021 ◽  
Vol 87 (12) ◽  
pp. 36-41
Author(s):  
A. S. Fedorov ◽  
E. L. Alekseeva ◽  
A. A. Alkhimenko ◽  
N. O. Shaposhnikov ◽  
M. A. Kovalev
Keyword(s):  
Carbon Dioxide ◽  
Laboratory Tests ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Sample Surface ◽  
Test Results ◽  
Carbon Dioxide Corrosion ◽  
Gas Industry ◽  
Test Parameters ◽  
Repeatability And Reproducibility

Carbon dioxide (CO2) corrosion is one of the most dangerous types of destruction of metal products in the oil and gas industry. The field steel pipelines and tubing run the highest risk. Laboratory tests are carried out to assess the resistance of steels to carbon dioxide corrosion. However, unified requirements for certain test parameters are currently absent in the regulatory documentation. We present the results of studying the effect of the parameters of laboratory tests on the assessment of the resistance of steels to CO2 corrosion. It is shown that change in the parameters of CO2 concentration, chemical composition of the water/brine system, the buffer properties and pH, the roughness of the sample surface, etc., even in the framework of the same laboratory technique, can lead in different test results. The main contribution to the repeatability and reproducibility of test results is made by the concentration of CO2, pH of the water/brine system, and surface roughness of the samples. The results obtained can be used in developing recommendations for the choice of test parameters to ensure a satisfactory convergence of the results gained in different laboratories, as well as in elaborating of a unified method for assessing the resistance of steels to carbon dioxide corrosion.

scholarly journals A brief compendium of water entry results derived from laboratory tests of various types of wall assemblies

2019 ◽  
Vol 282 ◽  
pp. 02050
Author(s):  
Michael A. Lacasse ◽  
Nathan Van Den Bossche ◽  
Stephanie Van Linden ◽  
Travis V. Moore
Keyword(s):  
Numerical Simulation ◽  
Performance Evaluation ◽  
Laboratory Tests ◽  
Moisture Transfer ◽  
Control Design ◽  
Water Entry ◽  
Building Envelope ◽  
Test Results ◽  
Different Types ◽  
Wood Frame

There is an increase in the use of hygrothermal models to complete the performance evaluation of walls assemblies, either in respect to design of new assembles or the retrofit of existing wall assemblies. To this end there are guides available in which is provided information on moisture loads to wall assemblies. This includes, for example, Criteria for Moisture-Control Design Analysis in Buildings given in ASHRAE 160, Assessment of moisture transfer by numerical simulation provided in EN 15026, and NRC’s “Guidelines for Design for Durability of the Building Envelope”. The designer of a new assembly or evaluator of an existing wall is tasked with having to determine what moisture loads to apply to the wall and where to apply this load within the assembly. Typically there is little or no information that is readily available regarding moisture loads to walls and thus the suggested hourly moisture load, as given in ASHRAE 160, is 1% by weight of the total driving rain load to the wall (i.e. kg/m2-hr). In this paper, a brief compendium of water entry test results derived from laboratory tests of various types of wall assemblies is provided from which estimates of moisture loads to different types of wall can be developed. Water entry test results are given of wood frame walls typically used in housing, but also metal-glass curtain walls and other commercial wall assemblies, where possible, in terms of driving loads to the wall.

Multivariate interpretation of laboratory tests used in monitoring patients

1990 ◽  
Vol 36 (5) ◽  
pp. 748-751 ◽  
Author(s):  
H B Slotnick ◽  
P Etzell
Keyword(s):  
Small Groups ◽  
False Positive ◽  
Laboratory Tests ◽  
False Negative ◽  
Test Results ◽  
Laboratory Findings ◽  
Bonferroni Inequality ◽  
The Impact

Abstract This study demonstrates an approach to the problem of minimizing false-negative and false-positive laboratory findings. In this approach, we consider the fact that results of laboratory tests are correlated, utilize within-person test results to interpret current results, and minimize the impact of multivariate conservatism by examining test results in small groups. The procedure requires panels of tests to be divided into related subpanels, testing each subpanel independently, and using the Bonferroni inequality to determine whether any of the observed values for a given subpanel is "out-of-range." The procedure is demonstrated, and its limitations are observed and discussed.

scholarly journals Analytical Model for Predicting the UCS from P-Wave Velocity, Density, and Porosity on Saturated Limestone

2019 ◽  
Vol 9 (23) ◽  
pp. 5265 ◽  
Author(s):  
González ◽  
Saldaña ◽  
Arzúa
Keyword(s):  
Wave Velocity ◽  
Predictive Models ◽  
Laboratory Tests ◽  
Ultrasonic Pulse ◽  
P Wave ◽  
Test Results ◽  
Regression Analyses ◽  
P Wave Velocity ◽  
Dry Conditions ◽  
Engineering Projects

Rock mechanics and rock engineering projects require determining, among other parameters, the uniaxial compressive strength (UCS) of rock. For such a purpose, it is not uncommon to perform ultrasonic pulse laboratory tests. Many researchers have found experimental relationships between strength and P-wave velocity, but these relationships are based mainly on dry conditions and without considering any other physical or chemical characteristics of the studied rock. Specifically, for limestone, there are 11 correlations reported in the literature, eight of which are simple and the remaining three are multiple, and, among the latter, only two of them consider the saturation. In order to evaluate the combined effect of P-wave velocity, density, and porosity on the UCS of saturated limestone, simple and multiple regression analyses were carried out on the test results of 13 saturated limestone specimens to determine the parameters of both previously mentioned predictive models. The results showed that density is not correlated with strength.

An Impact Cutting Test for Tire Tread Stocks

1936 ◽  
Vol 9 (3) ◽  
pp. 520-530
Author(s):  
J. H. Dillon
Keyword(s):  
Laboratory Tests ◽  
Testing Machine ◽  
Test Results ◽  
Road Test ◽  
Cutting Resistance ◽  
Cutting Test ◽  
Impact Device ◽  
Impact Cutting ◽  
The Impact

Abstract The impact cutting device described in this paper is recommended for testing the cutting resistance of tread stocks because of its simplicity and the accuracy with which its results agree with road test results. The fact that the device was designed on semi-quantitative theoretical grounds gives some additional confidence in its results. It is possible that other cutting devices, designed with no regard to theory whatsoever, might operate as well as the impact device. However, it is felt that, since most laboratory tests on rubber stocks are necessarily largely empirical, it is well to attempt to design a testing machine which will operate in the ranges of the variables found in service.

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