D-Dimers

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I wonder if someone might help shed some light here. Post-op day 4, abdo abcess drainage patient who went from room air to tachypneic 30-40 and 100% FiO2 over a couple of hours. I did a D-dimer as I suspected a possible PE. Came back 6000. Doc said it would be elevated since the patient is 4 days post-op, and you need a result of 10 000 for it to indicate PE.

Then a few days later, 3 day post-op cystectomy, same symptoms as patient above, D-dimer 3120, but ultrasound showed PE.

I don't understand! Please help! Many thanks in advance.

Specializes in ACNP-BC, Adult Critical Care, Cardiology.
How many days post-op would I expect to see an elevated D-dimer in the absence of liver diseases?

There have been various studies that have addressed this. Most of the studies have shown that d dimer is elevated for at least a month post-op with the duration of elevation varying depending on the type of surgery done.

A study done in General Surgery (intra-abdominal and retroperitoneal/liver) showed that d dimer is elevated for 25 days in intra-abdominal surgery and 38 days after retroperitoneal and liver surgery. See: Kinetics of D-dimer after general ... [blood Coagul Fibrinolysis. 2009] - PubMed - NCBI

In Orthopedic Surgery, d dimers were found to be elevated for 30 days after Total Knee Replacement. See: Course of D-dimer concentrations after total knee replacement surgery: effect of allogeneic and unwashed drainage blood transfusion - MU[]OZ - 2006 - Transfusion Alternatives in Transfusion Medicine - Wiley Online Library.

Since this is an ICU forum, realize that in our patient population, there is limited utility of d dimers because our patients have other conditions that cause an elevated d dimer, thus, the predictive value of this test in ruling out a clot is not extensively used by critical care providers.

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Thank you, Juan de la Cruz, for taking the time to answer my questions and for citing those sources. I'm afraid my continued learning is going down the tubes working in a small, peripheral hospital where there are no docs on at night. I appreciate your input!

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I would say by their presentation yes they absolutely should have been scanned. The NP and other nurse mentioning vq scan both made solid points. Pt is post op with shortness of breath and tachycardia..... Could be PE, atelectasis, pna, sepsis Remember that assessment is always used before lab readings and the scan is just allowing you to a picture of whats going on.

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Yes!

With an elevated ddimer all you have is an inconclusive or low specificity result (50% Sp for ddimer). This means the test is good to rule out embolic disease but not to rule it in.

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correct.

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I agree, prep8611, and I wasn't using the d-dimer to try to diagnose PE, but without a doc available, it is typical for us to do labs following the physical assessment. That way, if we do need to call the doc, he/she has all the stats.

I wonder if, in an ICU setting, the d-dimer is at all necessary then, particularly following surgery or trauma or in the presence of liver disease?

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That's what I was saying before, the d diner may be ordered but we rarely use it. D dimer will also be very elevated in CA patients who tend to have medical icu admissions.

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Specializes in ACNP-BC, Adult Critical Care, Cardiology.
I wonder if, in an ICU setting, the d-dimer is at all necessary then, particularly following surgery or trauma or in the presence of liver disease?

Yes, it has very limited utility in our setting as ICU providers and nurses. There's a multitude of other reasons that can elevate D-dimer in ICU patients other than what you mentioned...MI, cancer, inflammatory conditions, and even infections can cause it to to be elevated.

The test is used in out-patient settings and ED's in conjunction with physical presentation that is concerning for a VTE or PE in patients with no other reason to have an elevated D-dimer. If the D-dimer is normal, there won't be a need to scan. If it's elevated, you can either scan or proceed to treat based on a high suspicion for PE if scanning is not feasible.

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.
I wonder if someone might help shed some light here. Post-op day 4, abdo abcess drainage patient who went from room air to tachypneic 30-40 and 100% FiO2 over a couple of hours. I did a D-dimer as I suspected a possible PE. Came back 6000. Doc said it would be elevated since the patient is 4 days post-op, and you need a result of 10 000 for it to indicate PE.

Then a few days later, 3 day post-op cystectomy, same symptoms as patient above, D-dimer 3120, but ultrasound showed PE.

I don't understand! Please help! Many thanks in advance.

I am confused...how did an ultrasound see a Pulmonary emboli?
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Specializes in ACNP-BC, Adult Critical Care, Cardiology.
So in these cases, both patients should have been scanned then!

Well, not necessarily. The contrast Chest CT Scan obviously gave you the diagnosis in both cases. However, what was the initial hesitation to get a CT Scan? Like I mentioned previously, there are patients that we worry about subjecting to IV dye (poor kidney function, dye allergy). In those cases, there are other things that can help with the diagnosis of PE.

One, you can do a Dulpex Ultrasound of the legs and if a DVT is positive, then you will anticoagulate anyway. If there is high suspicion for a PE based on presentation, you can safely deduct that there is a source of a PE from the legs and a PE is likely.

You can also do transthoracic echocardiogram or a 2-D Echo. PE is a clot in the pulmonary arterial circulation. You know that the RV pumps blood to the pulmonary arteries - if there is a significant PE, the RV will show strain on the 2-D Echo due to difficulty pumping blood through the pulmonary circulation. Evidence of R heart strain is a strong diagnostic indicator of a PE.

Another test that was being done more commonly in the past is a V/Q Scan which only gives you PE probabilities and will not detect smaller PE's.

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Specializes in Emergency/Cath Lab.
I am confused...how did an ultrasound see a Pulmonary emboli?

I was also interested in this. Also a D-dimer only >10000 for PE? How does that work.

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Well, not necessarily. The contrast Chest CT Scan obviously gave you the diagnosis in both cases. However, what was the initial hesitation to get a CT Scan? Like I mentioned previously, there are patients that we worry about subjecting to IV dye (poor kidney function, dye allergy). In those cases, there are other things that can help with the diagnosis of PE.

One, you can do a Dulpex Ultrasound of the legs and if a DVT is positive, then you will anticoagulate anyway. If there is high suspicion for a PE based on presentation, you can safely deduct that there is a source of a PE from the legs and a PE is likely.

You can also do transthoracic echocardiogram or a 2-D Echo. PE is a clot in the pulmonary arterial circulation. You know that the RV pumps blood to the pulmonary arteries - if there is a significant PE, the RV will show strain on the 2-D Echo due to difficulty pumping blood through the pulmonary circulation. Evidence of R heart strain is a strong diagnostic indicator of a PE.

Another test that was being done more commonly in the past is a V/Q Scan which only gives you PE probabilities and will not detect smaller PE's.

This guy is very intelligent. What he said ^

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Hesitation to do a scan was lack of docs to read the scan at night, due to absence of docs.

Thank you very much for taking the time to do this teaching! I'm very appreciative.

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