肝素鈉
肝素鈉是一種注射用**抗凝血劑**，在獸醫學中主要用於治療血栓栓塞性疾病，以及具爭議性的瀰漫性血管內凝血（DIC）。 主要臨床應用包括： - **血栓預防**：有強烈證據支持其可用於降低高危險病患發生大血管血栓的機率。 - **DIC 管理**：歷史上用於治療 DIC，但目前的共識建議，若 DIC 病患同時伴隨發炎反應，應避免使用。 - **馬匹醫學**：用於預防蹄葉炎、治療 DIC，以及作為腹腔灌洗液以預防術後腸道沾黏。 > **臨床要點**：與低分子量肝素（LMWH）相比，未分級肝素（UFH）的藥代動力學特徵變異性極大。UFH 需要密集監測 aPTT 或抗 Xa 因子活性，以確保療效並避免災難性出血。
作用機制: Heparin acts as an indirect anticoagulant by binding to and potentiating the activity of **Antithrombin III (ATIII)**. - **Low Concentrations**: The Heparin-ATIII complex rapidly inactivates **Factor Xa**, preventing the conversion of prothrombin to thrombin. - **High Concentrations**: The complex inactivates **Thrombin (Factor IIa)**, blocking the conversion of fibrinogen to fibrin, and also inactivates factors **IX, XI, and XII**. - **Fibrin Stabilization**: By inhibiting the activation of **Factor XIII**, heparin prevents the formation of stable fibrin clots. *Note*: Heparin does **not** lyse existing clots (it is not a thrombolytic); rather, it prevents the expansion of existing thrombi and the formation of new ones. It also increases the release of **lipoprotein lipase**, boosting the clearance of circulating lipids.
各物種劑量
- Adjunctive treatment of DIC · 75 Units/kg SC three times daily OR 5-10 Units/kg/hour by continuous IV infusion OR 50-100 Units/kg SC q6h · SC/IV · Variable · Doses extrapolated from general small animal guidelines in monograph.
- Feline arterial thromboembolism · 250-300 Units/kg SC q8h · SC/IV · q8h · First dose is administered IV to cats showing signs of shock.
- Maintenance therapy for arterial thromboembolic disease · 250-300 Units/kg SC every 8 hours · SC · q8h · Initial in-hospital therapy
- Prevention of complications associated with hypercoagulable states · Initially 150 Units/kg SC. Then 125 Units/kg q12h for 6 doses and then decreased to 100 Units/kg SC every 12 hours. · SC · q12h
- Adjunctive treatment of DIC · 80-100 Units/kg IV q4-6h (may be added to fluids and given as a slow drip). Low grade DIC may be treated with 25-40 Units/kg SC 2-3 times a day. · IV/SC · q4-6h or 2-3x daily
- Adjunctive therapy in endotoxic shock · 40 Units/kg IV or SC 2-3 times a day · IV/SC · q8-12h · May prevent the development of microthrombi.
- Adjunctive therapy in the prevention of laminitis · 25-100 Units/kg subcutaneously 3 times daily · SC · q8h · Higher doses used when a thrombotic event is underway.
- Prevention of abdominal adhesions · 30,000-50,000 Units heparin in 10 L of lavage fluid (warm LRS) administered intraperitoneally · Intraperitoneal · At 12, 18, 36, and 48 hours post-surgery · 48 hours · Administered via a 32 french fenestrated trocar catheter.
給藥途徑
禁忌症
- Known hypersensitivity to heparin
- Severe thrombocytopenia
- Uncontrollable bleeding (not caused by DIC)
- Intramuscular (IM) administration (causes hematomas)
- Actively bleeding DIC patients with severe factor depletion
不良反應
- Hemorrhage (most common)
- Thrombocytopenia
- Hypersensitivity reactions (derived from bovine/porcine tissue)
- Anemia in horses (due to erythrocyte agglutination)
- Injection site pain and hematoma (especially if given IM)
- Vasospastic reactions
- Osteoporosis (with long-term use)
- Rebound hyperlipidemia
- Hyperkalemia
- Alopecia
藥物相互作用
- Aspirin · May increase the risk for hemorrhage
- Dextran · May increase the risk for hemorrhage
- NSAIDs · May increase the risk for hemorrhage
- Warfarin · May increase the risk for hemorrhage
- Antihistamines · May partially counteract heparin's anticoagulant effects
- Nitroglycerin (IV) · May partially counteract heparin's anticoagulant effects
- Propylene Glycol · May partially counteract heparin's anticoagulant effects
- Digoxin · May partially counteract heparin's anticoagulant effects
- Tetracyclines · May partially counteract heparin's anticoagulant effects
監測
- Activated partial thromboplastin time (aPTT) - most often recommended
- Whole blood clotting time (WBCT)
- Partial thromboplastin time (PTT)
- Activated clotting time (ACT)
- Thromboelastography (TEG)
- Platelet counts
- Packed cell volume (PCV) / Hematocrit
- Occult blood in stool and urine
- Clinical signs of bleeding or efficacy
過量
Overdosage of heparin is directly associated with **severe bleeding**. Clinical signs preceding frank hemorrhage include: - Hematuria - Tarry stools (melena) - Petechiae and ecchymoses (bruising) **Reversal**: **Protamine sulfate** can be administered to reverse heparin's anticoagulant effects. It binds to heparin to form a stable, inactive complex.
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