Tag Archives: haematology

A smaller dose of tPA in PE

A prospective open label randomised controlled trial from China compared two doses of r-tPA for massive or submassive PE. 50 mg / 2hr was as efficacious as 100 mg / 2hr but had fewer bleeding complications. Bleeding was much more common in patients under 65 kg, suggesting perhaps there should be dose per kg instead of a nice round number?

Efficacy and safety of low dose recombinant tissue-type plasminogen activator for the treatment of acute pulmonary thromboembolism: a randomized, multicenter, controlled trial.
Chest. 2010 Feb;137(2):254-62

Alternative to warfarin after VTE

In a randomised noninferiority trial the oral direct thrombin inhibitor dabigatran was compared with warfarin in patients with venous thromboembolic disease (VTE) after acute treatment with parenteral anticoagulation. Recurrent VTE and major bleeding rates were similar in the two groups. Dabigatran has the advantage of not requiring blood monitoring.

Dabigatran versus Warfarin in the Treatment of Acute Venous Thromboembolism
N Engl J Med. 2009 Dec 10;361(24):2342-52

Thrombophilia screening

A young patient presents with pulmonary embolism. Should you send blood to the lab for a thrombophilia screen? What if she is pregnant? How about a patient with an upper limb DVT, or a child with a stroke?

The answers, in order, are: not necessarily; possibly – trials are ongoing; it depends; and ‘not indicated’. At least according to the The British Committee for Standards in Haematology (BCSH) in their 2009 document ‘Clinical guidelines for testing for heritable thrombophilia’

The document highlights the lack of evidence that the results of thrombophilia screening influence type or duration of management, or predict likelihood of recurrence in unselected patients with symptomatic venous thrombosis. Furthermore, the results of thrombophilia tests are frequently misinterpreted. Many more situations and conditions are covered in the full document.

‘Clinical guidelines for testing for heritable thrombophilia’

Other The British Committee for Standards in Haematology guidelines

Plasma:red cell transfusion ratio in trauma

In major trauma patients who require blood transfusion, fresh frozen plasma (FFP) to packed red blood cell (RBC) ratios of up to 1:1 have been associated with reduced mortality in retrospective studies, which may be in part due to survival bias (some patients die before they can be given as much FFP as the survivors).

To eliminate this bias, Australian researchers reviewed 331 trauma patients receiving at least 5 units of red cells in the first 4 hours, with a median Injury Severity Score of 36. When deaths in the first 24 hours were excluded, FFP:RBC ratio had no association with mortality. They conclude that prospective randomised controlled trials are needed.

Fresh frozen plasma (FFP) use during massive blood transfusion in trauma resuscitation
Injury. 2010 Jan;41(1):35-9

Blood product ratios and survival bias

Haemostatic resuscitation of trauma patients, using high ratios of fresh frozen plasma (FFP) to packed red cells (PRBC), is growing in popularity as a result of military experience. Few data support the practice in civilian trauma. It is possible that some of the demonstrated mortality benefit is a result of survival bias: it takes time to obtain FFP, by which time severely injured patients may be dead. Therefore, those that receive large ratios of FFP:PRBC must have survived long enough to receive it. In other words FFP doesn’t lead to survival, but survival leads to FFP. Some evidence in favour of this explanation is provided on a study of 134 patients in the Journal of Trauma. Reanalysing data to correct for survival bias made an apparently significant survival benefit from high FFP:PRBC ratios go away. An interesting paper, although unlikely to dissuade us from paying attention to coagulopathy in trauma. I suspect the debate on optimal blood product resuscitation will be around for a while.

The Relationship of Blood Product Ratio to Mortality: Survival Benefit or Survival Bias?
J Trauma. 2009 Feb;66(2):358-62

Transfusion and ARDS

Blood transfusion in trauma is a risk factor for acute respiratory distress syndrome (ARDS). An analysis of 14070 patients in a trauma database showed that 521 (4.6%) developed ARDS. Logisitc regression analysis demonstrated that, independent of injury type, injury severity, or pneumonia, (1) early PRBCs transfusion of more than 5 units during the first 24 h of hospital admission predicted ARDS and (2) each unit of PRBCs transfused early after admission increased the risk of ARDS by 6%.

Early packed red blood cell transfusion and acute respiratory distress syndrome after trauma.
Anesthesiology. 2009 Feb;110(2):351-60