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Incidence of acute lung injury in dogs receiving transfusions | VETgirl Veterinary CE Podcasts

In this VETgirl online veterinary CE podcast, we review TRALI (again, as it’s super important!). Have you ever heard of TRALI? The acronym stands for transfusion-related acute lung injury, and is a type of acute lung injury (ALI) recognized in human patients receiving transfusions. In people, this syndrome occurs either immediately after transfusion (TRALI) or within 6-72 hours of transfusion (delayed TRALI). It is characterized by an acute onset of clinical signs, hypoxemia and bilateral lung infiltrates in the absence of heart disease, and no ALI before the transfusion. TRALI can affect between 5-25% of human ICU patients receiving transfusions, and can be life-threatening. In veterinary patients, the condition is termed VetALI and is characterized by similar criteria, including:

  • An acute onset of < 72 hours of tachypnea and labored breathing at rest
  • Known risk factors such as inflammation, infection, sepsis, systemic inflammatory response syndrome (SIRS), severe trauma, multiple transfusions, smoke inhalation, near drowning, or aspiration of stomach contents
  • Pulmonary capillary leak as evidenced by bilateral and diffuse infiltrates on thoracic radiographs or CT, proteinaceous fluid within the conducting airways, or  increased extravascular lung water
  • Inefficient gas exchange as evidenced by hypoxemia without positive end-expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) plus known FiO2 as evidenced by the PaO2:FiO2  ratio ≤ 300, increased Alveolar-arterial gradient (A-a gradient), venous admixture indicative of a non-cardiac shunt, or increased dead-space ventilation
  • Diffuse pulmonary inflammation as evidenced by transtracheal wash or bronchoalveolar lavage fluid with neutrophilia or biomarkers of inflammation, or evidence of inflammation on positron emission tomography1

Since this syndrome isn’t well-recognized in veterinary patients, Thomovsky et al wanted to evaluate this in a study called “Incidence of acute lung injury in dogs receiving transfusions.” This study, which was originally done at University of Wisconsin – Madison, wanted to document that TRALI exists in our canine patients, with an incidence similar to that in human medicine. So they looked prospectively at 54 dogs that received either blood or plasma transfusions while hospitalized, and had 3-view thoracic radiographs performed before their transfusion. All patients also had an arterial blood gas performed prior to transfusion if possible, or pulse oximetry. Radiographs and ABG/SpO2 after transfusion and PaO2:FiO2  ratios were calculated.

They diagnosed dogs with TRALI if they had post-transfusion radiographic pulmonary infiltrates (without evidence of heart failure on radiographs or echocardiography) and a low PaO2:FiO2  ratio (<300 mm Hg). Observing these patients prospectively, the authors initially enrolled 66 dogs into this study, with 12 excluded due to death, euthanasia, discharge or incomplete records. 54 dogs remained and were included in the study. Patients were a mean age of 7.4 years, with 27 spayed females and 27 males (26 castrated, 1 intact) in the study. They received blood products for a variety of reasons, the most common of which were IMHA (16 dogs), post-op anemia (8 dogs) and perioperative splenectomy with or without hemoabdomen (8 dogs).

Most dogs (44/54, 81.5%) received pRBCs, 16 received FFP, and 2 received whole blood. 8 dogs received multiple transfusions of multiple blood products. None of the patients had signs of acute hemolytic transfusion reactions. Overall, two dogs fulfilled the criteria for VetALI, with PaO2:FiO2  ratio < 300 mm Hg after transfusion and radiographs consistent with ALI. One was a dog with pancreatitis, the other had undergone lung lobectomy. Neither had dyspnea or tachypnea. Both patients received FFP transfusions (with a range of 13-22 ml/kg being administered).

The incidence of VetALI in this study was 2/54, or 3.7%, which is significantly less than that reported in human medicine. A control population of ill dogs that did not receive transfusions was examined in a previous study and there was no significant difference in the incidence of VetALI in these two populations.2

So, what can we take away from VETgirl podcast?

This study suggests that 2/54 dogs receiving transfusions had VetALI, which is a similar incidence (3.7%) to ill dogs not receiving transfusions. While the authors can’t definitively say that these dogs had true transfusion-related ALI, neither had hypoxemia or pulmonary infiltrates prior to transfusion. Interestingly, both dogs that developed VetALI (suspected TRALI) received FFP. Plasma-containing products are the most likely to induce TRALI in human patients, and platelets may also be implicated. Possible mechanisms of TRALI in human patients include an antibody-mediated reaction or interaction between biologic mediators in the transfused blood and the lung. One of the patients with VetALI (the one with pancreatitis) was euthanized three days after transfusion due to worsening respiratory effort and rate. The other dog survived to discharge.

This is the first veterinary study looking at the incidence of suspected TRALI in clinical canine patients; kudos to the authors! While the authors ideally wanted at least 60 cases to achieve a statistical power, that wasn’t possible due to the dogs excluded from the study. However, the results are still significant in terms of the clinical importance of reporting and recognizing these cases. It would be nice to see a follow up prospective study with a control population of critically ill dogs that are at risk for developing ALI.

In conclusion, this study suggests that TRALI does occur in dogs receiving transfusions, although the incidence was not as high as in human patients. Knowing the criteria for VetALI and recognizing the risk factors may be important for your critically ill patients!

References:

  1. Thomovsky EJ, Bach J. Incidence of acute lung injury in dogs receiving transfusions. J Am Vet Med Assoc 2014;244:170-174. (Appendix 1: Modified definition of VetALI).
  2. Parent C, King L, Walker L, et al. Clinical and clinicopathologic findings in dogs with acute respiratory distress syndrome: 19 cases (1985-1993). JAVMA 1996;208:1419-1427.

Abbreviations:
A-a gradient: Alveolar-arterial gradient
ABG: arterial blood gas
ALI: acute lung injury
CPAP: continuous positive airway pressure
FFP: fresh frozen plasma
IMHA: immune-mediated hemolytic anemia
P:F ratio: PaO2:FiO2
PEEP: positive end-expiratory pressure
pRBCs: packed red blood cells
SIRS: systemic inflammatory response syndrome
SpO2: pulse oximetry
TRALI: transfusion-related acute lung injury

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