Blood
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
Almost all stages of the coagulation process require the presence of calcium ions (Ca++) and adequate levels of plasma calcium are essential for normal clotting to occur. Clotting factor deficiencies and low levels of other substances, such as vitamin K, can also increase the time it takes for blood to coagulate. For example, most cases (about 80%) of the genetic bleeding disorder haemophilia result because the liver is not able von to produce enough clotting factor VIII (anti-haemophilic factor). Similarly, the most common hereditary clotting disorder, Von Willebrand’s disease, is the result of a deficiency of the plasma protein von Willebrand factor which helps to stabilise the bond between thrombocytes and collagen (see above). Finally, vitamin K is essential for the formation of a number of clotting factors including factor II (prothrombin) and factor X. The anticoagulant drug warfarin inhibits the amount of vitamin K available to the liver and prevents the production of these and other factors. This lengthens clotting time and is useful for the management of those likely to develop blood clots (see Chapter 7). One of the great misconceptions about warfarin is that it somehow ‘thins’ the blood when it actually interferes with the production of clotting factors (e.g. prothrombin). Dietary deficiency of vitamin K can also lead to lengthening of clotting time which is why it is very important to eat delicious green vegetables such as broccoli and spinach.
Percutaneous transluminal coronary intervention: History, techniques, indications and complications
Ever D. Grech in Practical Interventional Cardiology, 2017
The incidence of abrupt closure/acute occlusion and subacute closure (<24 hours) has declined106 from 3% in the PTCA era to 0.3% in the current era of intra-coronary stents and effective dual anti-platelet therapy. The mechanism of abrupt closure includes coronary dissection, thrombosis and vasospasm. Less frequently, air embolisation and vessel-to-vessel distal embolisation can occur. Patients will often become hemodynamically unstable and must first be resuscitated and stabilised, with intubation and mechanical ventilation and mechanical circulatory support if needed. Activated clotting time (ACT) should be therapeutic. Intra-coronary stenting has become the cornerstone of management of abrupt or threatened closure due to dissection; thrombectomy may occasionally be useful when thrombus formation is prominent.
Laboratory Instrumentation, Reagents, Methods, and Patient Sample as Variables in Coagulation
Harold R. Schumacher, William A. Rock, Sanford A. Stass in Handbook of Hematologic Pathology, 2019
During the first half of this century, laboratory assessment of the coagulative properties of blood consisted largely of the evaluation of patient bleeding times, whole-blood clotting time, and later the prothrombin time (PT) as well as the activated partial thromboplastin time (APTT). During this time period, the methods employed were labor intensive and the technicians utilized visual end points of clot formation in an attempt to describe the coagulation process. Needless to say, results varied between laboratories and between technicians. The first breakthrough in standardizing the detection of the coagulation end point came in the 1950s and 1960s, when BBL, a division of the Becton and Dickinson Company automated the manual wire loop method of determining the critical clotting end point with the development of the fibrometer. This instrument, still found in many laboratories today, utilizes an electromechanical technique to detect formation of the first fibrin strand and hence establish an objective end point for clot formation.
Bothrops snakebites in the Amazon: recovery from hemostatic disorders after Brazilian antivenom therapy
Published in Clinical Toxicology, 2020
Sâmella Silva de Oliveira, Eliane Campos Alves, Alessandra dos Santos Santos, Elizandra Freitas Nascimento, João Pedro Tavares Pereira, Iran Mendonça da Silva, Jacqueline Sachett, Hiochelson Najibe dos Santos Ibiapina, Lybia Kássia Santos Sarraf, Jorge Carlos Contreras Bernal, Luciana Aparecida Freitas de Sousa, Mônica Colombini, Hedylamar Oliveira Marques, Marcus Vinicius Guimarães de Lacerda, Ana Maria Moura-da-Silva, Hui Wen Fan, Luiz Carlos de Lima Ferreira, Ida Sigueko Sano Martins, Wuelton Marcelo Monteiro
Patients’ blood samples were collected at T0, T12, T24, T48 and on discharge. Clotting time was determined by the 20 min whole blood clotting test [23–25]. Blood was defined as unclottable when no clot was formed within 20 min and clottable when a solid or partial clot was formed within 20 min. Platelet counts and mean platelet volume (MPV) were carried out on samples containing potassium EDTA as the anticoagulant. Two percent v/v Bothrops-Lachesis antivenom was added to the samples to neutralize Bothrops venom present in the sample, and counts were determined in an automated cell counter (Sysmex Corp., Kobe, Japan). Thrombocytopenia was defined by a platelet count below 150 × 109/L. Low and high MPV were defined when values were below 7.4 fL and above 10.4 fL, respectively.
Comparative toxicological characterization of venoms of Cerastes cerastes and Macrovipera mauritanica from Morocco and neutralization by monospecific antivenoms
Published in Toxin Reviews, 2020
Bouchra Makran, Laila Fahmi, Lotfi Boussada, Naoual Oukkache, Fatima Chgoury, Hakima Benomar, Noreddine Ghalim, Mustapha Lkhider
The coagulant activity of both venoms and their respective fractions was evaluated by two methods based on the coagulation of human plasma:The minimum coagulant dose (MCD) of both viper venoms and their purified fractions was considered as the amount of enzyme capable of coagulating the plasma in 60 s (Theakston and Reid 1983). It was determined using 0.2 mL of citrated human plasma placed at 37 °C, mixed with various concentrations of 10–200 µg of C. cerastes venom and their fractions and 100–1000 µg of M. mauritanica venom and their fractions. The mixture was diluted in 0.1 mL of distilled water. The clotting time was visually characterized by the appearance of fibrin networks or the immediate formation of a clot.The clotting activity was also carried out on a microtiter plate with 96 wells using 150 µL of citrated human plasma mixed with 50 µL of various concentrations of venoms (10–120 µg) and their fractions diluted in 50 μL of distilled water. After 30 min incubation at 37 °C, the reaction was assessed by an ELISA reader at a wavelength of 405 nm. The absorbance values of the control wells (plasma diluted in distilled water) were subtracted from the results of the reaction (Menaldo et al.2012).
“Bad things come in small packages”: predicting venom-induced coagulopathy in Bothrops atrox bites using snake ontogenetic parameters
Published in Clinical Toxicology, 2020
Jorge Carlos Contreras Bernal, Pedro Ferreira Bisneto, João Pedro Tavares Pereira, Hiochelson Najibe dos Santos Ibiapina, Lybia Kássia Santos Sarraff, Cláudio Monteiro-Júnior, Handerson da Silva Pereira, Bruno Santos, Valeria Mourão de Moura, Sâmella Silva de Oliveira, Marcus Lacerda, Vanderson Sampaio, Igor Luis Kaefer, José María Gutiérrez, Paulo Sérgio Bernarde, Hui Wen Fan, Jacqueline Sachett, Ana Maria Moura da Silva, Wuelton Marcelo Monteiro
In this study, one patient died. A 91 year-old male was bitten in the right hand and the right foot. Immediately after the bite the patient reported an intense acute pain in the bitten sites. Eleven hours after the snakebite, patient was hospitalized presenting intense pain in the right foot and edema extending to the whole limb. Eight vials (80 mL) of Bothrops antivenom were administered. He presented with acute renal injury. Patient’s health status deteriorated and 48 hours from admission he was diagnosed with compartment syndrome and was submitted to an extensive fasciotomy in the right leg. Secondary bacterial infection was diagnosed and clindamycin was started. After two days, the patient died of septic shock. Abnormalities in clotting time or platelet counts and bleeding were not observed during hospitalization. The snake brought by the patient was an adult female.
Related Knowledge Centers
- Activated Clotting Time
- Anticoagulant
- Coagulation
- Partial Thromboplastin Time
- Thrombin Time
- Capillary
- Blood
- Prothrombin Time
- Reptilase Time
- Disseminated Intravascular Coagulation