Meta Analysis
Deep Vein Thrombosis and Its Prevention in Critically Ill Adults
This review may be edited
Posted By: A Delaney
Posted Date: 8/8/2002
Title: Deep Vein Thrombosis and Its Prevention in Critically Ill Adults
Authors: John Attia, MD, PhD; Joel G. Ray, MD; Deborah J. Cook, MD, MSc; James Douketis, MD
Reference: Arch Intern Med. 2001;161:1268-1279
Link: Click here for a direct link to the paper. A password may be required for access to fulltext.
Abstract: Background: Our objective was to systematically review the incidence of deep vein thrombosis (DVT) and the efficacy of thromboprophylaxis in critically ill adults, including patients admitted to intensive care units and following trauma, neurosurgery, or spinal cord injury.
Methods: Two authors independently searched MEDLINE, EMBASE, abstract databases, and the Cochrane database. Data were extracted independently in triplicate.
Results: Ten percent to 30% of medical and surgical intensive care unit patients develop DVT within the first week of intensive care unit admission. The use of subcutaneous low-dose heparin reduced the rate by 50% compared with no prophylaxis. Approximately 60% of trauma patients developed DVT within the first 2 weeks of admission. Use of unfractionated heparin appears to decrease the incidence of DVT by only 20%, whereas low-molecular-weight heparin decreases the incidence by a further 30%. The estimated prevalence of DVT in neurosurgical patients not given prophylaxis is 22% to 35%. Mechanical prophylaxis is efficacious, with a pooled odds ratio in 5 randomized trials of 0.28. Use of low-molecular-weight heparin has been investigated as an adjunct to mechanical prophylaxis with a pooled odds ratio of 0.59 compared with graduated compression stockings alone. The incidence of DVT without prophylaxis in acute spinal cord injury patients is likely in excess of 50% to 80%. Studies of prophylaxis in these patients are too sparse to come to any definitive conclusion.
Conclusions: Critically ill patients commonly develop DVT, with rates that vary from 22% to almost 80%, depending on patient characteristics. Methods of prophylaxis proven in one group do not necessarily generalize to other critically ill patient groups. More potent prophylactic regimens other than unfractionated or low-molecular-weight heparins alone may be needed with higher-risk groups.
Are the Results Valid?
1. Did the overview address a focused clinical question?
It addresses 2 main questions. What is the incidence of deep venous thrombosis (DVT) in critically ill patients, and how effective is prophylaxis for DVT in intensive care patients admitted with a number of conditions.
2. Were the criteria used to select articles for inclusion appropriate?
The list of criteria applied to determine inclusion is published.
3. Is it unlikely that important, relevant studies were missed?
The search terms appear to be appropriate and comprehensive however there were some minor limitations to the search. It was limited to English language and stops at August 1998. Authors, other experts in the field and representatives from pharmacutical companies were not contacted. Overall it is unlikely that important relevant studies were missed however, it would be prudent to update the search before clinical recommendations are issued.
4. Was the validity of the included studies appraised?
Yes. The validity of the included trials was determined by their design, sample size, population studied and how DVT was diagnosed.
5. Were assessments of studies reproducible?
Yes, Data was extracted independently by three authors and disagreement was resolved by consensus.
6. Were the results similar from study to study?
The variable nature of the studies included and the assessment of outcome, makes the determination of this difficult. Tests for heterogeneity were done where possible.
What are the Results?
1. What are the overall results of the overview?
The results varied in the differing populations. Because of the variable methods of patient selection and different ways in which DVT was diagnosed, it is very difficult to come to an overall result.
  • The results from the general medical/surgical group are too inconsistent to draw conclusions from.
  • The results from the trauma group show an incidence of DVT when diagnosed by screening patients with venography, of approximately 60% when no prophylaxis was used. This was reduced by the use of fixed dose unfractionated heparin (LDH)and by fixed dose low molecular weight heparin (LMWH). When the data for LDH and LMWH are combined and compared to mechanical devices there is a reduction in DVT in the anticoagulant arm with an OR of 0.46, giving a relative risk of 0.68 or a RRR of 32%.
  • In neurosurgical patients, the incidence of DVT when no prophylaxis was used was 22%. There was only one study that compared unfractionated heparin to placebo and it reduced the incidence of DVT from 34% to 6%. There were 5 studies that compared mechanical means of prophylaxis to no prophylaxis. These showed a benefit to the use of mechanical prophylaxis with an odds ratio of 0.28 (CI from 0.17-0.46). This gives a relative risk of 0.43 and a RRR of 57%. When LMWH in combination with mechanical devices was compared to mechanical devices alone the results from 3 trials showed a benefit from the combined therapy with an odds ratio of 0.59 (CI 0.4-0.85), with a relative risk of 0.74 and a RRR 26%. There was more bleeding in the groups of patients given anticoagulants from 3.2% compared to 1.2% when anticoagulants were not used.
  • For acute spinal injury patients the incidence of DVT was high at 81% when screened for with venography. The trials comparing the various methods of prophylaxis discussed here are too variable to draw general conclusions from.
  • 2. How precise were the results?
    Due to the variable nature of the trials and how outcome was assessed the precision of the results is hard to determine.
    Will the Results Help Me In Caring For My Patients?
    1. Can the results be applied to my patient care
    DVT would appear to be a common problem in many groups of patients in ICU. The means to prevent it are also generally available. There is nothing apparent in this paper that would prevent the results being applicable to a wide range of intensive care patients.
    2. Were all clinically important outcomes considered?
    There is scant data on the occurance of clinically significant bleeding (especially intracranial haemorrhage) in the neurosurgical and trauma patients. The incidence of HITTS is not mentioned.
    3. Are the benefits worth the harms and costs?
    From this paper it is very hard to tell whether the benefits are worth the harms and costs. The conclusions that could be drawn would be that DVT is a very common problem for patients in the ICU, and that both anticoagulants and mechanical means of prophylaxis probably both reduce the incidence of DVT. The ideal regime could not be determined from the data available at the time this research was done. The method used for any given patient would then have to depend upon the relative risk of DVT, balanced against the risk of bleeding and the effect of that bleeding for the particular patient.
    An evidence-based recommendation, which is the building block for an evidence-based guideline, that summarizes this topic can be found in the EBR section.

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