Respirology/ ICU

Why is LDH elevated in Pleural Fluid from Diuretics: Mechanism

It is common teaching to be judicious when interpreting the thoracentesis results of patients receiving diuretic therapy. It is stated, their pleural LDH will often be elevated and result in them being misclassified as exudative effusions when they are in fact transudative.

WHY?

Currently, the mechanism is not entirely clear, but proposed mechanisms include:

  • Lactate dehydrogenase (LDH) is an intracellular protein responsible for catalysing the conversion of lactate to pyruvic acid. It tends to leak during cellular injury or lysis.
  • Thus, any patient with repeated or bloody thoracentesis, the LDH may be elevated secondary to RBC lysis (blood) or local trauma from the thoracentesis; repeated attempts augmenting that damage.
  • LDH is primarily created by the liver, and in patients with CHF, hepatic congestion/ release upon diuresis may play a role in its elevation in pleural fluid.
  • Diuretics move water via diffusion; from the extravascular (pleural space) to the blood, leading to an increase in the protein and LDH concentration in the pleural cavity.

REFERENCES

  • Bielsa, J.M. Porcel, J. Castellote, et al. Solving the Light’s criteria misclassification rate of cardiac and hepatic transudates. Respirology, 17 (2012), pp. 721-726
  • Mitrouska I, Bouros D. The Trans-Exudative Pleural Effusion. CHEST, Volume 122, Issue 5, 1503 – 1505
  • Broaddus, V. Diuresis and transudative effusions—changing the rules of the game. The American Journal of Medicine, Volume 110 , Issue 9 , 732 – 735
Get Medical Pearls directly to your inbox every week!
Weekly posts with high yield medical knowledge, directly to your mailbox!
Dr. C Humphreys

Internal Medicine

Share
Published by
Dr. C Humphreys

Recent Posts

Trapped Lung vs. Lung Entrapment

Though often used synonymously; Trapped Lung and Lung Entrapment technically describe separate entities along the…

5 months ago

Cause of Pericardial Effusion in Pulmonary Hypertension: Pathogenesis

It is not clearly understood why patients with pulmonary hypertension (PH) develop pericardial effusions. However,…

6 months ago

Difference between Mycophenolate Mofetil vs. Mycophenolate Sodium

The two drugs are not interchangeable nor dose equivalents. Mycophenolate mofetil (Cellcept) is a semi…

7 months ago

What is an “Anephric” Creatinine Rise?

Serum Creatinine can be a deceptive surrogate during an acute kidney injury. It may lag…

1 year ago

Macrophage activation syndrome vs. Hemophagocytic lymphohistiocytosis

Macrophage activation syndrome (MAS) is a life-threatening complication of rheumatic diseases (i.e SLE, Juvenile idiopathic…

2 years ago

When does a Tracheostomy mature?

After creation of a percutaneous tracheotomy site for prolonged ventilation, one of the immediate complications…

2 years ago

This website uses cookies.