Hemostatics are medications used to induce hemostasis, which is a physiological process that results in clot formation to prevent or stop a hemorrhage.
Primary hemostasis first starts when platelets are activated and aggregate to form a platelet plug at the site of an injured blood vessel.
Next, secondary hemostasis starts with the coagulation cascade, when clotting factors become consecutively activated to ultimately activate prothrombin into thrombin.
The activated thrombin then cleaves fibrinogen into fibrin, which binds with other fibrin proteins to form a fibrin mesh that reinforces the platelet plug.
Now, when the tissue has healed, the endothelial cells produce an enzyme called tissue plasminogen activator, or tPA, which in turn converts plasminogen into its active form plasmin.
Plasmin then acts as a protease by cutting fibrin into smaller pieces, called fibrinolysis, and ultimately dissolving the clot.
Now, the most commonly used hemostatics include antifibrinolytics, such as aminocaproic acid and tranexamic acid, and vitamin K analogues like phytonadione, which can be administered orally, intravenously, intramuscularly, or subcutaneously; as well as topical hemostatic agents, such as gelatin, microfibrillar collagen, bovine thrombin, and human fibrin sealant, which are applied topically.
Let’s first focus on antifibrinolytics, which work by inhibiting the conversion of plasminogen to plasmin, which ultimately prevents fibrinolysis.
Now, aminocaproic acid is primarily used as prophylaxis to prevent bleeding after cardiac surgeries, like coronary artery bypass surgery, or CABG, as well as to prevent bleeding in clients with cirrhosis, in which the liver is unable to synthesize clotting factors, and to prevent recurrence of subarachnoid hemorrhage.
Some side effects of aminocaproic acid include malaise and muscle weakness, bradycardia, hypotension, as well as injection site reactions.
Less commonly, aminocaproic acid can cause gastrointestinal side effects like abdominal cramps, nausea, and diarrhea.
Finally, prolonged use of aminocaproic acid may lead to myopathy with rhabdomyolysis, which may ultimately result in acute renal failure.
As far as contraindications go, aminocaproic acid is contraindicated in clients who experience disseminated intravascular coagulation, or DIC; this is a state of widespread clot formation in the body associated with platelet consumption and thrombocytopenia, making the client more prone to severe hemorrhage.
Caution should also be taken in clients with cardiac, renal and hepatic diseases, as well as during pregnancy, as its effects on the fetus are not well known.
Alright, the next antifibrinolytic is tranexamic acid, which can be used to stop or prevent bleeding in clients with hemophilia, as well as in clients with menorrhagia, or heavy menstrual bleeding.
Now, side effects of tranexamic acid include headache, seizures, impaired color vision, as well as abdominal pain, nausea, diarrhea.
On rare occasions, it can result in excessive clotting, which increases the risk of deep vein thrombosis and pulmonary embolism.
For these reasons, tranexamic acid is contraindicated in clients who already have impaired color vision and a history of thromboembolism, as well as active intravascular clotting.
Next, we have vitamin K analogues, such as phytonadione, which is used by the liver as cofactor for the synthesis and activation of certain clotting factors.
Phytonadione is typically administered to clients with vitamin K deficiency, which makes them more susceptible to bleeding.
Specifically, phytonadione is given shortly after birth intramuscularly as prophylaxis to prevent hemorrhagic disease of the newborn.
Vitamin K analogues can cause side effects like dyspnea, chest tightness, and injection site reaction. When given intravenously or intramuscularly, phytonadione has a boxed warning for severe anaphylaxis that can result in shock.
