Hypothermia Causing Coagulopathy

[dchz]

Trauma triad of death: hypothermia, acidosis, and coagulopathy....

A lot of people are convinced that hypothermia CAUSES coagulopathy... many citing something to do with factors in secondary hemostasis not working, others saying something about platelet dysfunction. I've been on pubmed for the last 2 hours on this topic, but nothing really convincing so far....

For the sake of expanding my knowledge, I would like someone to post some good evidence that mild hypothermia, let's say for our sake of argument 36-34 Celsius, causes coagulopathy....

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[urge]

Trauma triad of death: hypothermia, acidosis, and coagulopathy....

A lot of people are convinced that hypothermia CAUSES coagulopathy... many citing something to do with factors in secondary hemostasis not working, others saying something about platelet dysfunction. I've been on pubmed for the last 2 hours on this topic, but nothing really convincing so far....

For the sake of expanding my knowledge, I would like someone to post some good evidence that mild hypothermia, let's say for our sake of argument 36-34 Celsius, causes coagulopathy....

I have thought it is nonsense since residency but many years later it is still being taught.

The effects of hypothermia on coagulation have been studied mostly in vitro. Very mild hypothermia (down to 35°C) has no effect on any part of the coagulation cascade. Temperatures below 35°C can in some cases (but not in all patients, see below) induce mild platelet dysfunction and sometimes a mild decrease in platelet count. When temperatures drop below 33°C other steps in the coagulation cascade, such as the synthesis and kinetics of clotting enzymes and plasminogen activator inhibitors, can also be affected [2-8]. Recently, Ruzicka and coworkers performed a study in which they precisely measured thromboelastography in healthy subjects at a temperature range starting at 38°C all the way down to 12°C [9]. They reported that decreasing temperatures led to a progressive delay in the initiation of thrombus formation, as well as a decrease in the speed of clot creation and growth. However, significant effects of hypothermia on this parameter began only at 30°C, progressing rapidly below this temperature but reaching statistical significance only at 24°C [9].

Conclusion
Although mild to moderate hypothermia has some effect on the coagulation system the clinical risk of bleeding associated with cooling appears to be very low. This will, however, increase significantly if the patient has moderate-to-severe acidosis. No effects of hypothermia on coagulation occur in any patient as long as temperature is ≥35°C, and patients at very high bleeding risk can safely be cooled to this temperature.

Hypothermia and coagulation

 

[coffeebythelake]

Trauma triad of death: hypothermia, acidosis, and coagulopathy....

A lot of people are convinced that hypothermia CAUSES coagulopathy... many citing something to do with factors in secondary hemostasis not working, others saying something about platelet dysfunction. I've been on pubmed for the last 2 hours on this topic, but nothing really convincing so far....

For the sake of expanding my knowledge, I would like someone to post some good evidence that mild hypothermia, let's say for our sake of argument 36-34 Celsius, causes coagulopathy....

i think it is taught that 35 degrees causes platelet dysfunction, around 32 degrees causes coagulation factor dysfunction
don't have a reference for this though.

 

[Buslenak]

Hi there! Unfortunately I cannot warm my patients because of lack of right equipment. So hypothermia is an acute issue for me and I've been thinking about that a lot. In my opinion usually trauma patients die from hypoxia (sever hypovolemia, anemia, hypoxemia, etc.). Coagulopathy just increases bleeding leading to hypovolemia. Acidosis just follows by hypoxia. What do you think about this investigation: Changes in coagulation during therapeutic hypothermia in cardiac arrest patients?

 

[T-burglar]

I think most of the experiments were done in vitro. Which is far from ideal.

My clinical impression is that in cases of major blood trauma like MTP, CPB, and especially DHCA, Coagulopathy can be tenacious even when all factors and platelets have been well restored and the only thing still going on is hypothermia.

I don’t know if hypothermia by itself, in the abence of blood trauma, causes a major coagulopathy.

 

[DM27]

From my experience and reading there is essentially no well established relationship between clinically evident coagulopathy/bleeding and the mild hypothermia temperature range you described.

 

[drmwvr]

I'm thinking of open, ruptured AAA's that are coagulopathic for reasons other than their being sub-35 degrees on admission to the unit. The question is a good one, but at the end of the day, are you not going to aggressively warm?

 

[vector2]

The in vitro studies aren't really that convincing regarding mild hypothermia's effect on platelets and factors, but that doesn't disprove any conclusions about hypothermia and overall blood loss from in vivo studies. From open anesthesia:

Increase in Blood Loss/Transfusions
EBL increased 500 cc with 1.6C drop [Schmied H et al. Lancet 347: 289, 1996, n = 60], 186 cc with 0.5C [Widman J et al. Anesth Analg 95: 1757, 2002, n = 46], and 140 cc with 0.4C drop [Winkler M et al. Anesth Analg 91: 978, 2000, n = 150]



I didn't look at the individual studies to see how well controlled they were or the confounding factors, but it does give me pause that three different authors in two different decades found similar conclusions regarding mild hypothermia increasing EBL in hip arthroplasty.

 

[dchz]

The in vitro studies aren't really that convincing regarding mild hypothermia's effect on platelets and factors, but that doesn't disprove any conclusions about hypothermia and overall blood loss from in vivo studies. From open anesthesia:

Increase in Blood Loss/Transfusions
EBL increased 500 cc with 1.6C drop [Schmied H et al. Lancet 347: 289, 1996, n = 60], 186 cc with 0.5C [Widman J et al. Anesth Analg 95: 1757, 2002, n = 46], and 140 cc with 0.4C drop [Winkler M et al. Anesth Analg 91: 978, 2000, n = 150]



I didn't look at the individual studies to see how well controlled they were or the confounding factors, but it does give me pause that three different authors in two different decades found similar conclusions regarding mild hypothermia increasing EBL in hip arthroplasty.

Haha it's funny you quotes this study. This was the actual paper that made me look into this. The authors main source about the 500ccs is a different study WITH HIS OWN NAME on it... He is literally quoting himself here.... I guess the BS doesn't smell if he wraps in enough layers by writing more papers quoting himself. I also looked up the other cited sources in that paper. Nothing credible on the topic.

Does it give you less pause if I told you the 3 diff authors are from the same group and quotes each other in their papers?

Edit: I was only referring to the Schmied article, let me read the others and get back to you.

 

[dchz]

but at the end of the day, are you not going to aggressively warm?

Loaded question; what is "aggressive" warming?

The short answer is no. I'm more of a passive warming guy.

The long answer is: if it's a thyroidectomy and I've got a pair hugger on and the pts temp drifts to 35. I'm gonna warm the pt (most likely I'll turn on the bair hugger before the case starts, so it's really a prevention of being cold).
But if it's a CABG with the pt whole body prepped with an underbody warmer and the pt is bleeding post CPB and the temp is 35. I'm gonna go search for other reasons that the pt is bleeding and not screaming for people to change the room temp to dry sauna.

But I think we both agree that the effect on coagulation is worth exploring.

 

[dhb]

I've got a pair hugger

Is that strictly for men?

#metoo

 

[dchz]

BAIR HUGGER* it's a convection warming cover in the colonies.

 

[drmwvr]

Loaded question; what is "aggressive" warming?
The short answer is no. I'm more of a passive warming guy.

The only reason I turn up the heat in the heart room is to keep my Raynaud's from declaring itself. That said, I suppose I'd call aggressive warming for really cold patients more post operative efforts like "clam shell" full length bair huggers and fluid warmers post op. The devil is in the definition I guess...

 

[deleted162650]

#metoo

They really shoulda known better than to name their anti-sexual harassment organization the “pound me too” movement.