Episode 19: (Why) does DIC cause shock?

For this installment of “intern questions” Hannah wondered “Does DIC causes shock”? This question was prompted by an interaction she had when admitting a patient with a diagnosis of shock. When reviewing the possible etiologies, she and a medical student realized that disseminated intravascular coagulation (DIC) may cause some component of shock. Because DIC may be a manifestation of other underlying processes in the body that can lead to shock (most notably sepsis) it is difficult teasing the two out experimentally.

But, we tried!

What is DIC?

DIC is a consumptive coagulopathy in which massive systemic activation of the clotting system results in both diffuse clotting and in consumption of clotting factors, creating the risk of hemorrhage. It is a manifestation of underlying systemic dysfunction with a variety of etiologies including sepsis, metastatic cancer, trauma, pancreatitis, and amniotic fluid embolus.

One way to begin answering whether DIC can cause shock is to ask “does aseptic DIC cause shock?” A series of experiments in the 1940s and 1950s attempted to answer the first question by inducing DIC in dogs and observing the physiology. Preliminary studies found that just injecting trypsin intravenously resulted in fatal circulatory collapse in rats and rabbits. Postmortem exams in these animals identified diffuse clotting in the cardiac, pulmonary, liver, and kidney circulation.

Which case first?

These early studies suggested that causes of DIC not traditionally thought of as causing shock in isolation are associated with hypotension. But it still could be the case that shock is leading to DIC, not the reverse. Additional experiments are required.

To determine whether DIC was a direct cause of shock, multiple groups administered heparin prior to the agent which led to DIC/shock. The idea was to see whether this prevented the shock by preventing the consumptive coagulopathy. In one study, DIC two known provokers of DIC were injected into dogs: amniotic fluid or incompatible blood transfusions. Some does received heparinized and some did not. In both experimental models of DIC, the dogs who had been pretreated with heparin experienced a lesser fall in blood pressure: in the incompatible transfusion group, 84mmHg versus 45 mmHg; in the amniotic fluid group 92 mmHg versus 7 mmHg.

Despite these findings, it is important to note that anticoagulation with heparin is not recommended in most cases of DIC. There is some very low quality evidence for heparin but the International Society for Thrombosis and Hemostasis only recommends its use in patients with low bleeding risk with a thrombotic predominant presentation.

What form of shock?

So it appears that causes of DIC that don’t typically lead to hypotension are associated with shock. Furthermore, heparin mitigates the hypotension. The next question becomes: what form of shock is DIC causing? More studies examined a large group of patients and animals with right heart catheterization during the development of DIC. Researchers observed a rise in pulmonary artery pressure and concluded this was a consequence of microthrombi (as opposed to left heart failure). Why did they conclude this? They noted that cardiac output recovered significantly after administration of an alpha-1 antagonist (phenoxybenzamine), which can act as a pulmonary vasodilator potentially mobilizing clots in the pulmonary vasculature.

So it appears that DIC leads to an “obstructive shock”.

Take Home Points

  1. Disseminated intravascular coagulation may be an independent cause of hypotension.
  2. The mechanism of hypotension in this situation is likely obstructive due to pulmonary vasculature microthrombi.


Click here to obtain AMA PRA Category 1 Credits™ (1.00 hours), Non-Physician Attendance (1.00 hours), or ABIM MOC Part 2 (1.00 hours).

Listen to the episode

Credits & Citation

◾️Episode written by Hannah Abrams
◾️Show notes written by Tony Breu and Hannah Abrams
◾️Audio edited by Clair Morgan of nodderly.com

Abrams HR, Breu AC, Cooper AZ. Why (does) DIC cause shock? The Curious Clinicians Podcast. February 7, 2021. https://curiousclinicians.com/2021/02/17/episode-19-why-does-dic-cause-shock

Image credit: https://en.wikipedia.org/wiki/Disseminated_intravascular_coagulation

Published by Tony Breu

Tony Breu, MD is an internist/hospitalist who loves asking ‘why’?

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