Critical Care Medical Patients

The Risk

The incidence of deep vein thrombosis (DVT) in patients in the intensive care unit (ICU) ranges from 25% to 32%.^1–3 Most of these patients have several risk factors for venous thromboembolism (VTE)^4,5 and approximately 5% develop DVT prior to admission to the ICU.^6–9

The patients pose a special challenge for VTE prophylaxis^8,10,11 because they often have multisystem disease that renders routine methods of prevention problematic. For example, thrombocytopenia, renal insufficiency, or active bleeding (often gastrointestinal) may preclude the use of pharmacologic prophylaxis. Thus, it is paradoxical that this group of patients may not be able to safely or effectively use some of the standard prophylaxis measures.

Prophylactic Methods and Recommendations

General Considerations

A randomized double-blind placebo controlled study in critically ill high-risk patients demonstrated that low-dose unfractionated heparin (LDUH) is effective in reducing asymptomatic DVT from 29% in the control group to 13% in the heparin group (risk ratio [RR] 0.37; 95% confidence interval [CI] 0.28-0.5). ²

In another study involving 223 patients mechanically ventilated for acute decompensated chronic obstructive pulmonary disease, low-molecular-weight heparin (LMWH) reduced the incidence of DVT from 28% in the control group to 15.5% in the LMWH group (RR 0.55; 95% CI 0.3-0.99) without any difference in adverse effects. ³

A meta-analysis of 2 randomized-controlled trials (RCTs)^12,13 in a total of 562 patients with trauma comparing intermittent pneumatic compression (IPC) with LMWH has not shown any significant difference in VTE between the 2 methods for prophylaxis. ¹⁴

A recent large multicenter RCT compared dalteparin (5000 IU plus a second placebo injection daily) with LDUH (5000 IU twice daily) in 3746 critically ill medical and surgical patients for the duration of their stay in ICU. ¹⁵ There was no significant difference in the rate of proximal DVT detected by ultrasound (5.1% vs 5.8%), but there was a lower incidence of PE in the dalteparin group (1.3% vs 2.3%; RR 0.28; 95% CI 0.17-0.47). There was no significant difference in the rate of bleeding between the groups. Prophylactic doses of dalteparin did not appear to accumulate in patients with renal dysfunction.

Recommendations

The LMWH (dalteparin as per label) is recommended (level of evidence: high). For patients with contraindications to pharmacologic prophylaxis, the use of graduated elastic compression stockings with IPC is an alternative (level of evidence: low). In the absence of contraindications, we suggest combined mechanical plus pharmacologic prophylaxis (level of evidence: low). For patients with contraindications to prophylaxis, surveillance with duplex scanning is indicated (level of evidence: low).