Define the term “Transfusion Associated Lung Injury (TRALI)”. Briefly outline its pathophysiology and clinical features.
TRALI is defined as:
a) occurrence of acute respiratory distress during or within 6 hrs of transfusion
b) presence of arterial desaturation on a pulse oximeter
c) absence of other causes of acute lung injury
The clinical features include: dyspnoea, fever, hypotension or hypertension, and documented hypoxemia
The pathophysiology of TRALI is due to the presence of leukoagglutinins in the donor plasma, which promotes neutrophil aggregation and sequestration in the pulmonary vasculature. It is now recognized that there is a broader spectrum of TRALI than purely leukoagglutinin mediated.
The Australian Red Cross has a nice summary of this issue.
A more thorough treatment is available from UpToDate.
According to the NHLBI, TRALI is diagnosed by the following criteria:
- Onset of symptoms within 6 hours of transfusion
- Bilateral chest infiltrates on CXR
- No other causes for acute lung injury (by the old ARDS definition)
- No pre-existing acute lung injury
- Absence of risk factors for other causes of ALI within the same time period
The clinical fatures are hypoxia, dyspnoea, fever, pulmonary oedema or pink frothy secretions from the ETT, hypotension and cyanosis.
The pathophysiology is well outlined in the below-linked article.
In short, neutrophils are sequestered in the lung parenchyma and are primed by endothelial cytokine release to repsond to trivial stimuli. The priming and sequestration seems to be due to endothelial cell activation. All of this is already happening before the trasnfusion. Then, the transfused blood is administered and it brings with it certain cytokine factors, or it results in the generation of inflammatry cytokines - either way, the increased pro-inflammatory stimulus causes all these sequestered neutrophils to activate and attack. The lung parenchyma is an innocent bystander in this.
Thus, the risk factors fro TRALI seem to be conditions with existing high levels of endothelial activation, such as:
- Critical illness of any sort
- Chronic alcoholism
- Shock states
- High ventilator pressures
- Positive fluid balance
Toy, Pearl, et al. "Transfusion-related acute lung injury: definition and review."Critical care medicine 33.4 (2005): 721-726.
Bux, Jürgen, and Ulrich JH Sachs. "The pathogenesis of transfusion‐related acute lung injury (TRALI)." British journal of haematology 136.6 (2007): 788-799.