What is Heparin
Heparin blocks clotting factors to stop new clots from forming and existing ones from growing. It is given parenterally because it is not absorbed from the gut.
Generic Name
- heparin
Brand Names
Hepalean, Heparin Lock Flush, Hep-Lock, Hep-Pak, Liquaemin, Calciparine, Innohep, Normiflo, Clexane, Fragmin, Klexane.
Drug Classification of Heparin
Therapeutic Class: anticoagulants Pharmacologic Class: antithrombotics
Indications and Therapeutic Effects
Heparin prevents and treats clots across several conditions: deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation, heart attack (with other drugs to stop further cardiac clots), and stroke. It also prevents clots during and after certain surgeries and inside the dialysis machine during kidney dialysis.
Mechanism of Action
Heparin binds antithrombin III and amplifies its activity. Antithrombin III is a potent inhibitor of several clotting factors, including thrombin and factor Xa, both central to clot formation. The conformational change heparin produces lets antithrombin III inactivate those factors far more effectively, which prevents new clots and stops existing ones from enlarging. The exact effect varies with the heparin type, the dose, and the patient, but every form works through this antithrombin III pathway.
Precautions and Contraindications
Bleeding is the central precaution: risk rises in patients with bleeding disorders, ulcers, or recent surgery, so monitor and adjust the dose as needed. Ulcer disease can worsen and bleed dangerously. Heparin clears through the liver and kidneys, so hepatic or renal impairment may need a lower dose or closer monitoring. It is generally considered safe in pregnancy and breastfeeding, but weigh the risks with the provider. Older patients may be more sensitive and need dose adjustment or closer monitoring.
Heparin is contraindicated with hypersensitivity to it, with active bleeding (including bleeding disorders and recent surgery), and with severe thrombocytopenia, since it can drop the platelet count further. Use caution in uncontrolled hypertension.
Drug Interactions
Drug-Drug. Aspirin and other NSAIDs (ibuprofen, naproxen) raise bleeding risk. Other anticoagulants and antiplatelets such as warfarin and clopidogrel also raise bleeding risk and can be especially dangerous in some conditions. Thrombolytics (streptokinase, alteplase) raise bleeding risk. Heparin can raise digoxin levels into a dangerous range. Certain antibiotics, such as tetracyclines, can reduce heparin's effectiveness.
Drug-Natural Products. Garlic, ginkgo biloba, vitamin E, and omega-3 fatty acids (fish oil) all increase bleeding risk.
Drug-Food. Vitamin K-rich foods such as leafy greens promote clotting and can reduce heparin's effect. Alcohol thins the blood and adds bleeding risk. Grapefruit can interfere with drug breakdown and raise heparin levels and bleeding risk.
Adverse Effects
Common effects: bruising or bleeding at the injection site, mild allergic reactions (rash, itching, hives), nausea or vomiting, and hair loss. The serious ones to catch are thrombocytopenia (low platelets, more bleeding), hemorrhage (especially if the dose runs high), and osteoporosis from long-term use.
Administration Considerations
Available Forms
- Solution for injection: 10 units/mL, 100 units/mL, 1000 units/mL, 5000 units/mL, 7500 units/mL, 10,000 units/mL, 20,000 units/mL, 40,000 units/mL.
- Pre-mixed solution: 1000 units/500 mL, 2000 units/1000 mL, 12,500 units/250 mL, 25,000 units in 250 and 500 mL.
Dosage for Neonates
Therapeutic Anticoagulation
- IV (Neonates and Infants <1 yr)
- Continuous infusion, Loading dose 75 units/kg, followed by 28 units/kg/hr, adjust to maintain aPTT of 60 – 85 sec.
Cardiovascular Surgery
- Intra-arterial (Neonates & Infants)
- 100 – 150 units/kg via an artery prior to cardiac catheterization.
Arterial Line Patency
- Intra-arterial (Neonates)
- 0.5 – 2 units/mL.
Dosage for Children
Therapeutic Anticoagulation
- IV (Children >1 yr)
- Intermittent bolus, 50 – 100 units/kg, followed by 50 – 100 units/kg q 4 hr.
- Continuous infusion, Loading dose 75 units/kg, followed by 20 units/kg/hr, adjust to maintain aPTT of 60 – 85 sec.
Cardiovascular Surgery
- Intra-arterial (Children)
- 100 – 150 units/kg via an artery prior to cardiac catheterization.
Line Flushing
- IV (Children)
- 10 – 100 units/mL (10 units/mL for infants <10 kg, 100 units/mL for all others) solution to fill heparin lock set to needle hub; replace after each use.
Total Parenteral Nutrition
- IV (Children)
- 0.5 – 1 units/mL (final solution concentration) to maintain line patency.
Dosage for Adults
Therapeutic Anticoagulation
- IV (Adults)
- Intermittent bolus, 10,000 units, followed by 5000 – 10,000 units q 4 – 6 hr.
- Continuous infusion, 5000 units (35 – 70 units/kg), followed by 20,000 – 40,000 units infused over 24 hr (approx. 1000 units/hr or 15 – 18 units/kg/hr).
- Subcut (Adults)
- 5000 units IV, followed by initial subcut dose of 10,000–20,000 units, then 8000 – 10,000 units q 8 hr or 15,000 – 20,000 units q 12 hr.
Prophylaxis of Thromboembolism
- Subcut (Adults)
- 5000 units q 8 – 12 hr (may be started 2 hr prior to surgery).
Cardiovascular Surgery
- IV (Adults)
- At least 150 units/kg (300 units/kg if procedure <60 min; 400 units/kg if >60 min).
Line Flushing
- IV (Adults)
- 10 – 100 units/mL (10 units/mL for infants <10 kg, 100 units/mL for all others) solution to fill heparin lock set to needle hub; replace after each use.
Total Parenteral Nutrition
- IV (Adults)
- 0.5 – 1 units/mL (final solution concentration) to maintain line patency.
Pharmacokinetics
Heparin is not orally bioavailable and cannot be absorbed from the GI tract, so it is given subcut or IV. Subcut absorption is slow and incomplete, with peak plasma concentrations within 4 hours and bioavailability of 30% to 70%; IV gives rapid, complete absorption with peak within minutes. Once absorbed it binds plasma proteins such as antithrombin III, with a volume of distribution of about 0.07 L/kg, so it stays largely in the plasma compartment, though it can accumulate in the liver, spleen, and lungs and cross the placenta into fetal circulation. Heparin is not metabolized by the liver; it clears mainly by renal excretion with a half-life of 1 to 2 hours and is eliminated within 8 to 12 hours, with roughly 30% excreted unchanged in the urine. Clearance is directly proportional to renal function, so impaired kidneys raise bleeding risk and may need a reduced dose.
Nursing Considerations for Heparin
Nursing Assessment
Review the medical history first: current medications, allergies, and conditions like bleeding disorders or liver or kidney disease. Take a full set of vitals (heart rate, blood pressure, respiratory rate, oxygen saturation) and a physical. Draw baseline coagulation studies, prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count, as the reference for both therapeutic effect and adverse effects.
Assess bleeding risk directly: prior bleeding episodes, recent surgery or trauma, and a physical that inspects skin and mucous membranes. Watch for bleeding gums, nosebleeds, unusual bruising, black tarry stools, hematuria, a fall in hematocrit or BP, and guaiac-positive stools. Screen for drug interactions, especially NSAIDs and antiplatelet agents.
Monitor for hypersensitivity (chills, fever, urticaria). The most common reaction is a delayed-type hypersensitivity reaction (DTHR), a type IV reaction with itchy eczema and plaques at injection sites that seldom progress to maculopapular exanthema; rare but life-threatening reactions include skin necrosis from heparin-induced thrombocytopenia.
Monitor platelet count every 2–3 days throughout therapy. Heparin may cause a mild thrombocytopenia that appears on the 4th day and resolves despite continued therapy. Heparin-induced thrombocytopenia (HIT), the severe immune form that requires stopping the drug, may develop around the 8th day, can drop the platelet count as low as 5000/mm3, and raises resistance to heparin. HIT affects roughly 3% to 5% of patients on heparin; current practice is to score bleeding-versus-clotting risk with the 4T scale, and a 4T score of 4 or more should prompt stopping all heparin, including line flushes, and switching to a nonheparin anticoagulant such as argatroban (Heparin Induced Thrombocytopenia, StatPearls). Also monitor for hyperkalemia and rises in AST and ALT: heparin can elevate serum potassium by reducing the number and affinity of adrenal angiotensin II receptors, suppressing aldosterone reversibly and enhancing sodium excretion.
For toxicity, protamine sulfate is the antidote, dosed at about 1 to 1.5 mg of protamine per 100 units of heparin to be neutralized (Heparin, StatPearls). Because the half-life is short, a small overdose can often be managed by simply withholding the drug.
Nursing Diagnosis
- Ineffective tissue perfusion related to decreased delivery of oxygen and nutrients to the tissues
- Risk for injury related to bleeding tendencies
- Risk for bleeding related to heparin therapy, as evidenced by elevated aPTT, prolonged PT, and low platelet count
- Risk for impaired skin integrity related to ecchymosis, petechiae, or hematoma formation
- Risk for infection related to repeated venipunctures for coagulation monitoring
- Noncompliance related to lack of understanding about the medication
Heparin Nursing Interventions
Examine every heparin sodium injection vial to confirm the correct vial before administration; fatal hemorrhages have occurred in pediatric patients when injection vials were confused with flush vials. Have a second practitioner independently check the original order, dose calculation, and infusion pump settings, since the dose depends on weight and history and the pump must deliver the right amount at the right rate. Review the patient's recent (emergency department, operating room) and current medication records before giving any heparin or LMW heparin product, because unintended use of two heparin products (unfractionated plus LMW) has caused serious harm or death.
Inform everyone caring for the patient about the anticoagulant therapy. Apply pressure to venipunctures and injection sites to prevent bleeding or hematoma, and avoid IM injections of other drugs. When transitioning off heparin, start oral anticoagulant therapy 4 – 5 days before discontinuing it, so the oral agent reaches full effect while heparin still covers the patient and the clot risk stays low during the overlap.
Intravenous Administration
Subcut. Administer deep into subcut tissue. Alternate sites between the arm and the left and right abdominal wall above the iliac crest. Inject the entire length of the needle at a 45°- or 90°-angle into a skin fold held between thumb and forefinger; hold the fold throughout. Do not aspirate or massage. Rotate sites frequently. Do not give IM because of hematoma risk. The solution should be clear; do not inject solution containing particulate matter.
IV Push. Diluent: give the loading dose undiluted. Concentration: varies with the vial used. Rate: administer over at least 1 min; the loading dose is given before continuous infusion.
Continuous Infusion. Diluent: dilute 25,000 units of heparin in 250 – 500 mL of 0.9% NaCl or D5W. Premixed infusions are already diluted and ready to use. Admixed solutions are stable for 24 hr at room temperature or refrigerated; premixed infusion is stable for 30 days once the overwrap is removed. Concentration: 50 – 100 units/mL. Rate: adjust to maintain therapeutic aPTT and use an infusion pump for accuracy.
Flush. To prevent clot formation in intermittent infusion (heparin lock) sets, inject dilute heparin solution of 10 – 100 units/0.5 – 1 mL after each medication injection or every 8 – 12 hr. To prevent incompatibility, flush the lock set with sterile water or 0.9% NaCl before and after the medication.
Y-Site Compatibility acetaminophen, acetylcysteine, acyclovir, alemtuzumab, alfentanil, allopurinol, amifostine, aminocaproic acid, aminophylline, amphotericin B lipid complex, amphotericin B liposome, anidulafungin, argatroban, ascorbic acid, atropine, azathioprine, azithromycin, aztreonam, benztropine, bivalirudin, bleomycin, bumetanide, buprenorphine, butorphanol, calcium chloride, calcium gluconate, cangrelor, carboplatin, carmustine, cefazolin, cefotaxime, cefotetan, cefoxitin, ceftaroline, ceftazidime, ceftriaxone, cefuroxime, chloramphenicol, cisplatin, cladribine, clindamycin, cyanocobalamin, cyclosporine, cytarabine, dactinomycin, daptomycin, dexamethasone, dexmedetomidine, digoxin, docetaxel, dopamine, doxacurium, doxapram, doxorubicin liposome, enalaprilat, ephedrine, epinephrine, epoetin alfa, eptifibatide, ertapenem, estrogens, conjugated, etoposide, etoposide phosphate, famotidine, fenoldopam, fentanyl, fluconazole, fludarabine, fluorouracil, folic acid, foscarnet, fosphenytoin, ganciclovir, gemcitabine, glycopyrrolate, granisetron, hydrocortisone, hydromorphone, ifosfamide, imipenem/cilastatin, indomethacin, irinotecan, isoproterenol, ketorolac, leucovorin, lidocaine, linezolid, lorazepam, magnesium sulfate, mannitol, mechlorethamine, melphalan, meropenem, mesna, metaraminol, methotrexate, methoxamine, methyldopate, methylergonovine, metoclopramide, metoprolol, metronidazole, micafungin, midazolam, milrinone, mitomycin, morphine, moxifloxacin, multiple vitamins, nafcillin, nalbuphine, naloxone, neostigmine, nitroglycerin, nitroprusside, norepinephrine, octreotide, ondansetron, oxacillin, oxaliplatin, oxytocin, paclitaxel, palonosetron, pamidronate, pancuronium, pemetrexed, penicillin G, pentobarbital, phenobarbital, phentolamine, phenylephrine, phytonadione, piperacillin/tazobactam, potassium acetate, potassium chloride, procainamide, prochlorperazine, promazine, propofol, propranolol, pyridostigmine, pyridoxine, ranitidine, remifentanil, rituximab, rocuronium, sargramostim, scopolamine, sodium acetate, sodium bicarbonate, streptokinase, succinylcholine, sufentanil, tacrolimus, theophylline, thiamine, thiopental, thiotepa, tigecycline, tirofiban, tolazoline, tranexamic acid, trastuzumab, trimethaphan, vasopressin, vecuronium, verapamil, vinblastine, vincristine, voriconazole, warfarin, zidovudine, zoledronic acid.
Y-Site Incompatibility alteplase, amiodarone, amsacrine, caspofungin, ciprofloxacin, dantrolene, daunorubicin hydrochloride, diazepam, diazoxide, doxycycline, epirubicin, filgrastim, haloperidol, hydroxyzine, idarubicin, ketamine, levofloxacin, mitoxantrone, mycophenolate, palifermin, papaverine, pentamidine, phenytoin, protamine, quinupristin/dalfopristin, reteplase, tobramycin.
Additive Compatibility Do not mix heparin in solution with other medications when given for anticoagulation, even compatible ones, because changes in the heparin infusion rate would also affect the admixture.
Patient Education and Teaching
Teach the patient to report any unusual bleeding or bruising (nosebleeds, bleeding gums, easy bruising) to the physician immediately, and to recognize these same signs as possible drug interactions. They should not take products containing aspirin or NSAIDs while on heparin, and should be cautious with natural products that raise bleeding risk. Caution them to avoid IM injections and injury-prone activities and to use a soft toothbrush and electric razor during therapy.
Tell them to go easy on vitamin K-rich foods (spinach, kale, collard greens, broccoli, brussels sprouts, cabbage, asparagus, some vegetable oils), which can counter heparin's effect, and to avoid alcohol and grapefruit or grapefruit juice, both of which raise bleeding risk. Have them tell every healthcare professional about their medication regimen before any treatment or surgery. Patients on anticoagulant therapy should carry an identification card at all times and make sure family and close contacts know about the medication.
Evaluation and Desired Outcomes
The main outcome is prevention or resolution of clots, confirmed by imaging such as ultrasound or by blood tests. Look for reduced symptoms (pain, swelling, redness), minimized complications such as bleeding or bruising, improved quality of life, and patent IV catheters. The lab target is a partial thromboplastin time (PTT) of 1.5 – 2.5 times the control without signs of hemorrhage.
Frequently Asked Questions
Why is heparin called a high-alert medication? The pharmacology is straightforward, but dosing errors and vial mix-ups cause the real harm. Fatal hemorrhages have occurred when concentrated injection vials were confused with dilute flush vials, which is why independent double checks of the order, dose, and pump settings are standard.
Which lab guides IV heparin therapy? The activated partial thromboplastin time (aPTT), kept at roughly 1.5 to 2.5 times the control. You also track platelet count every 2 to 3 days to catch heparin-induced thrombocytopenia and monitor for any sign of bleeding.
What is the antidote for heparin? Protamine sulfate, dosed at about 1 to 1.5 mg per 100 units of heparin (Heparin, StatPearls). Because heparin's half-life is short, a minor overdose can often be handled by simply holding the drug.
What is heparin-induced thrombocytopenia (HIT)? HIT is an immune reaction that drops the platelet count and paradoxically raises clotting risk, affecting about 3% to 5% of patients on heparin. A 4T score of 4 or more should prompt stopping all heparin, including flushes, and starting a nonheparin anticoagulant such as argatroban (Heparin Induced Thrombocytopenia, StatPearls).
Why is heparin given by injection instead of by mouth? It is not absorbed from the gastrointestinal tract, so it has to be given subcut or IV. IV gives a near-immediate effect; subcut absorption is slower and incomplete.
Why avoid IM injections while a patient is on heparin? Intramuscular injections can cause painful hematomas because the blood is anticoagulated. Apply pressure to venipuncture and injection sites, and use a soft toothbrush and electric razor to limit bleeding.