Deep vein thrombosis (DVT) prophylaxis is crucial in hospitalized patients. Still, the choice of therapy depends heavily on individual patient factors such as renal function, bleeding risk, mobility, and underlying conditions. In this post, we’ll explore real-world scenarios highlighting the common pitfalls of DVT prophylaxis. For the record, we are specifically talking about adult medical patients. Orthopedic and non-orthopedic surgical patients have a bit different guidelines.

1st scenario:

A 60-year-old gentleman with a PMH of hypertension and type 2 diabetes was admitted with community-acquired pneumonia and acute hypoxic respiratory failure, lab data showed normal kidney function and normal platelet count, and the patient was started on Heparin 5000 units SQ TID.

Comments: Low-molecular-weight heparins (LMWH), such as enoxaparin or dalteparin, are the preferred anticoagulants for preventing deep vein thrombosis (DVT) based on evidence from randomized trials showing their superiority. UFH is reserved for situations where LMWH is unsuitable, such as in dialysis-dependent patients, those with acute kidney injury (AKI), or when LMWH is unavailable. I included AKI here because of its dynamic nature, where rapidly changing kidney function leads to fluctuating creatinine clearance. Once kidney function stabilizes, switching back to LMWH is appropriate! So this patient should’ve been started on a LMW heparin. If the patient is allergic to heparin and heparin derivatives Fondaparinux or DOAC can be alternatively used, more on that soon!

Scenario 2:

A 21-year-old healthy gentleman presented with intractable nausea and vomiting, UDS was positive for cannabis, he was admitted for symptom control, labs were unremarkable, and Enoxaparin 40 mg daily was ordered.

Comment: Patients who are fully ambulatory and expected to have a short hospital stay are considered low-risk and typically do not require DVT prophylaxis. This patient met these criteria and was therefore deemed low risk for developing thromboembolic disease, so DVT prophylaxis was not needed in this case.

DVT prophylaxis is recommended for patients at moderate or high risk. While several scoring systems can help assess risk, my approach is straightforward: if a patient is not fully ambulatory and their hospital stay is expected to be longer than 24 hours, I provide DVT prophylaxis.

Scenario 3:

A 72-year-old lady, who’s on HD three times a week, was admitted with intractable nausea and vomiting, her labs showed Hemoglobin of 7.3 and plt count of 250k, the patient was started on IV fluid and placed on intermittent pneumatic compression for DVT prophylaxis.

Comment: When DVT prophylaxis is indicated, the sole use of mechanical DVT prophylaxis in the absence of contraindications to chemical methods is inappropriate. Mechanical methods—such as intermittent pneumatic compression (IPC), graduated compression stockings (GCS), and venous foot pumps—are primarily indicated for patients who have a high risk of bleeding or in whom anticoagulation is contraindicated. This patient should have been started on chemical DVT prophylaxis, specifically unfractionated heparin, as low molecular weight heparins are typically avoided in dialysis patients.

Adding a mechanical method to chemical DVT prophylaxis is acceptable, especially in patients at high risk for DVT. High-risk patients include those with a history of previous thromboembolic disease, cancer, and stroke.

Scenario 4:

A 55-year-old gentleman with a history of pancreatic cancer presented with intractable vomiting and diarrhea, his labs showed evidence of AKI with a calculated creatinine clearance of 29 ml/min, CBC showed plt count of 32k, and the patient was placed on intermittent pneumatic compression.

Comment: The patient is at high risk for thromboembolic disease due to his underlying pancreatic cancer, a chemical DVT prophylaxis is the most appropriate but he has a critical thrombocytopenia, and that’s why he was probably placed on a mechanical method instead of chemical prophylaxis! Generally, a platelet count of ≥50,000/μL is considered safe for anticoagulation. However, because of the patient’s high risk for DVT from his underlying cancer, the potential benefit of DVT prevention may outweigh the bleeding risk. In such high-risk cases, a lower platelet threshold can sometimes be acceptable; anticoagulation may be considered with a platelet count >30,000/μL, and in select cases, even >20,000/μL. In this situation, it would be wise to consult the patient’s oncologist to weigh the benefits and risks of chemical prophylaxis and to determine the most appropriate anticoagulant.

The patient has acute kidney injury with a creatinine clearance of less than 30 ml/min, Technically Enoxaparin or Dateparin can be used at reduced renal doses, but as we mentioned earlier, AKI is a dynamic with continuously changing creatinine clearance due to rapidly changing kidney function. Unfractionated heparin would be the most appropriate chemical prophylaxis, we can switch back to LMW heparin once kidney function is stabilized!

Scenario 5:

A 45-year-old morbidly obese man (BMI 42) with a history of coronary artery disease (CAD) and recent percutaneous coronary intervention (PCI), currently on dual antiplatelet therapy (DAPT), was admitted with acute sigmoid diverticulitis. His labs were unremarkable, and his provider did not prescribe chemical DVT prophylaxis, assuming DAPT would suffice.

Comment: Although DAPT reduces the risk of arterial thrombosis, it does not offer adequate protection against venous thromboembolism (VTE). Therefore, chemical DVT prophylaxis is still recommended for this patient. Low molecular weight heparin (LMWH) would be a suitable choice, but special attention must be given to dosing in morbidly obese patients, as standard doses may be inadequate.

Dosing Recommendations for Patients with BMI ≥40 kg/m²:
Patients with a BMI >40 kg/m² require higher doses of DVT prophylaxis due to pharmacokinetic changes in obesity. Standard doses may lead to subtherapeutic anticoagulation levels, necessitating adjusted dosing as follows:

• Enoxaparin:
  • Standard dose: 40 mg subcutaneously (SQ) once daily.
  • If creatinine clearance (CrCl) is <30 mL/min, reduce to 30 mg SQ daily.
  • In patients with BMI ≥40, increase to 40 mg SQ twice daily or consider weight-based dosing at 0.5 mg/kg once daily.
• Dalteparin:
  • Standard dose: 5000 units SQ daily.
  • For patients with BMI ≥40, increase to 7500 units SQ daily.
  • Avoid dalteparin in patients with CrCl <30 mL/min due to accumulation risk.
• Unfractionated Heparin (UFH):
  • Standard dose: 5000 units SQ twice or three times daily (TID).
  • Evidence suggests TID dosing does not significantly improve DVT prevention over BID dosing and is associated with an increased bleeding risk.
  • For patients with BMI ≥40, increase to 5000-7500 units TID, with no renal dose adjustment required.

Scenario 6:

A 55-year-old diabetic woman was admitted for pain control due to intractable back pain from a herniated disk. Her chart lists an allergy to heparin, so you asked her about the nature of the allergy. She couldn’t recall specific details but mentioned that it might have been related to a low platelet count she had in the past. Her current lab results show a platelet count of 250,000/µL and normal kidney function.

Comment:

In cases of reported heparin allergy, it’s essential to consider the possibility of a prior episode of heparin-induced thrombocytopenia (HIT), even if the exact details are unclear. Unless HIT can be definitively ruled out, it’s best to avoid both heparin and low-molecular-weight heparin (LMWH) due to the risk of exacerbating HIT. Suitable anticoagulation options in this case include fondaparinux or a direct oral anticoagulant (DOAC).

Unlike heparin, fondaparinux is structurally distinct and doesn’t carry the same HIT risk. The prophylactic dose is 2.5 mg subcutaneously once daily, which is effective even for morbidly obese patients. However, fondaparinux is contraindicated in patients weighing less than 50 kg and those with a creatinine clearance below 30 ml/min. It’s also best avoided when the platelet count is below 50,000/µL.

Alternatively, oral rivaroxaban 10 mg once daily or apixaban 2.5 mg twice daily can be used. Apixaban is a safer option if the creatinine clearance is less than 15 ml/min and in acute kidney injury (AKI).

F/U: The next day, the patient asked you how long she would need to continue the blood thinner.

VТЕ prophylaxis should ideally continue until the patient is fully ambulatory or discharged from the hospital.

Scenario 7:

A 75-year-old diabetic and hypertensive lady presented with a left-sided weakness started 30 minutes before ED arrival, the patient was evaluated in the ED and deemed a candidate for thrombolytic therapy, brain MRI was done the next morning and showed an ischemic stroke in the right MCA territory with punctate hemorrhage in the ischemic tissue, lab data was unremarkable, the stroke coordinator asked the caring provider on day 2, why the patient isn’t started on a chemical DVT prophylaxis and he indicated it’s contraindicated because of the punctate hemorrhages.

Comment: Stroke patients are at high risk for DVT and prophylaxis must be provided, in cases where thrombolytic therapy is given chemical prophylaxis should be started 24 hours after administering the thrombolytic therapy. Punctate hemorrhages seen in ischemic strokes are not considered a hemorrhagic transformation, they occur as a result of ischemic damage to blood vessels, making them more prone to minor leakage, and they are not contraindications for anticoagulation. This patient can be safely started on a LMW heparin.

How about patients with brain tumors? Brain tumors whether primary or metastatic are not absolute contraindications for chemical DVT prophylaxis, these patients are at increased risk of thromboembolic diseases, and the decision must be individualized based on their intracranial bleeding risk and overall general bleeding risk. Consulting with the patient’s neurosurgeon or oncologist is the easiest and best way to make such a decision! The same applies to spinal tumors. If you can’t reach the patient’s oncologist/neurosurgeon, place the patient on mechanical prophylaxis until you can.

How about intracranial hemorrhage? Mechanical DVT prophylaxis must be started on admission, and we add chemical prophylaxis for most patients one to four days after ΙCΗ stability is documented and confirmed by the caring neurosurgeon! An exception would be patients evaluated for urgent surgery for whom chemical prophylaxis may be temporarily withheld. I always call neurosurgery and ask them if it is safe to start a chemical prophylaxis.

Scenario 8:

A 35-year-old male with a 5-year history of ulcerative colitis, previously managed with corticosteroids and mesalamine, presents with a 3-day history of worsening abdominal pain and frequent bloody diarrhea (10 episodes/day). CBC showed HGB of 9 gm/dl and platelet count of 200k, He was diagnosed with a UC flare and started on IV corticosteroids and IV fluids. The patient was placed on mechanical DVT prophylaxis due to his bloody diarrhea.

Comment: Bloody stool in ulcerative colitis (UC) or Crohn’s disease is not an absolute contraindication for deep vein thrombosis (DVT) prophylaxis. Inflammatory bowel disease (IBD) patients are at a significantly increased risk of venous thromboembolism (VTE), especially during flare-ups, due to both inflammation and immobilization. A chemical DVT prophylaxis unless the bleeding is overt leading to critical anemia.

Scenario 9:

A 42-year-old gentleman with a history of alcoholic liver cirrhosis presented with abdominal pain and distention, his labs showed a platelet count of 55k, HGB of 8.2, and INR of 2.4, BUN/Cr of 9/0.6, the caring provider ordered Enoxaparin 40 mg SQ daily for DVT prophylaxis, the pharmacist called back asked if we want to continue with Enoxaparin as his INR was 2.4 and platelet count of 55k.

Comment: In chronic liver disease and cirrhosis, an elevated INR does not accurately reflect the patient’s coagulation status. The liver synthesizes both procoagulant and anticoagulant factors, and liver dysfunction decreases both. As a result, an elevated INR in these patients does not necessarily indicate a true bleeding risk or coagulopathy. The platelet count is above 50k which is considered safe as we discussed earlier, therefore a chemical DVT prophylaxis is indicated, and LMW heparin should be ordered given his intact kidney function.

To wrap up:

• Fully ambulatory patients with a short anticipated hospital stay are considered low risk and generally do not require DVT prophylaxis. This group typically includes young, healthy individuals. For patients who do not meet these criteria, DVT prophylaxis is recommended, provided there are no contraindications.
• LMW heparin agents are superior to unfractionated heparin and should be used except in dialysis-dependent patients where unfractionated heparin should be used. In AKI, unfractionated heparin is preferred given the dynamic nature of AKI and the continuously changing creatinine clearance.
• For patients with a history of HIT, fondaparinux and DOAC can be used. In advanced renal impairment and dialysis patients, Apixaban can be alternatively used.
• Patients with a BMI >40 kg/m² require higher doses of DVT prophylaxis due to pharmacokinetic changes in obesity.
• Punctate hemorrhages can be seen in ischemic strokes and are not considered a hemorrhagic transformation and they are not considered a contraindication for anticoagulation.
• Brain tumors whether primary or metastatic are not absolute contraindications for chemical DVT prophylaxis, the decision must be individualized based on their intracranial bleeding risk and overall general bleeding risk. Consulting with the patient’s neurosurgeon or oncologist is the easiest and best way to make such a decision!
• For intracranial hemorrhage, chemical prophylaxis should be considered one to four days after ΙCΗ stability is documented and confirmed by the caring neurosurgeon!
• Bloody stool in ulcerative colitis (UC) or Crohn’s disease, hemoptysis due to lung abscess or PE, epistaxis, microscopic hematuria, and menstrual bleeding are not considered contraindications for anticoagulation.
• In chronic liver disease and cirrhosis, an elevated INR does not accurately reflect the patient’s coagulation status and isn’t considered a contraindication for anticoagulation.