Coagulopathy & Lab Values
February 2, 2011
Q: I am teaching staff and one of my colleagues questioned why a hemorrhagic bleed would be contraindicated. I explained that hypothermia increases the incidence of coagulopathies, however he brought up a good point, if we are treating post arrest, the chance of an MI is there, therefore they will go to the cath lab.... were anticoagulation is started. So what do you do and how can I explain that?
A: Good questions – while true that TH may increase the risk and/or severity of bleeding (i.e., cooling causes coagulopathy) – the extent of this increased risk is small. Therefore it's a question of balancing risks and benefits. If someone has clinically dangerous bleeding (big GI bleed or brain bleed, for example), something that could worsen this would be high risk. If someone is on heparin, Coumadin, or going to the cath lab, without actual clinical bleeding, the risk is small, so its much more comfortable for us to proceed with TH.
It's kind of analogous to the treatment of elevated INR. If someone's INR is found to be very high, you might just give vitamin K if there is no actual bleeding (low risk for bad outcomes). But if an INR is very high AND they are coughing up blood (high risk for bad outcomes), you wouldn't rest with just vitamin K, you would also give FFP and/or other clotting factors.
- Benjamin Abella, MD MPhil
November 29, 2010
Q: How does TH affect lab values?
A: The main effect of TH on lab values is on blood gases. Need to know whether your lab corrects values or not to the body temperature. In other words, most blood gas analyzers warm blood to 37 degrees C before running; some labs report the values @ 37 degrees C, others @ the patient's temp @ time labs were drawn. That is what you need to know to manage the patient clinically.
Can approximate as follows:
for every 1 degree C below 37 degrees C, for PO2, substract 5 mmHg; for PCO2, substract 2 mmHg; for pH, add 0.012.
- Dave Gaieski, MD
December 14, 2009
Q: Thrombocytopenia is considered a contraindication for TH - is there a platelet level you would consider as an absolute contraindication in the absence of bleeding? AND if hypothermia was initiated post arrest , at what platelet count would you consider stopping the protocol and rewarming?
A: The exact risk of bleeding during therapeutic hypothermia (TH) is not known. TH has been used safely with thrombolytics and anticoagulants although this has not been carefully investigated. None of the large studies involving TH for cardiac arrest, stroke, or intracranial hemorrhage have reported large increases in bleeding. At 35 deg C, a mild decrease in platelet counts and qualitative dysfunction of platelets is seen, while at temp < 33 deg C, clotting factors will begin to be affected. That being said we do not have an absolute platelet count as a contraindication in our protocol. The only contraindications we have in terms of bleeding are if there is an intracranial bleed, bleeding due to significant trauma, or clinically relevant bleeding from other sources (GI bleed, dialysis graft bleeding etc). You can also consider prophylactically transfusing platelets (if it is not contraindicated for the patient) for counts < 20K with no bleeding, and < 50K with active bleeding. These are just our protocol recommendations, they have not been validated by scientific studies. I can not give you an absolute platelet count that I would not cool or stop cooling when present as It really depends on whether the patient is actively bleeding as well as many other patient specific factors. The risk of spontaneous bleeding from thrombocytopenia is classically noted at 20K so you may want to use this number, but again we may choose to cool someone with a platelet count below 20K if the specific situation calls for it. Bottom line is that in patients who are coagulopathic, the risk of bleeding should always be weighed against the benefits of cooling on a case by case basis.