June 2017—As an alternative to point-of-care testing, Wayne Chandler, MD, and colleagues developed and implemented a rapid emergency hemorrhage panel, or EHP, for trauma patients (Chandler WL, et al. Transfusion. 2010;50:2547–2552). The panel tests are prothrombin time, hematocrit, fibrinogen, and platelet count. “By limiting EHPs to patients that were actively bleeding, EHPs accounted for only 8 of 243 coagulation samples per day,” he and colleagues wrote in their 2010 article.
In an interview with CAP TODAY, Dr. Chandler, division chief of laboratory medicine, Department of Laboratories, Seattle Children’s Hospital, said he and his team implemented the panel at Harborview Medical Center about 15 years ago. Now it’s also in place at the University of Washington Medical Center and Seattle Children’s Hospital. They wrote the article in 2010 because people were encouraging them to tell others about the EHP. “So it wasn’t really a new thing. It was more that you kind of had to think a bit outside the box on how you were going to approach doing this testing because, classically, the laboratory in a sense is accuracy above everything, even if it takes forever.”
The clinicians typically get the EHP results about 20 minutes after the patient’s blood is drawn, “with 15 minutes of that being in-lab time,” Dr. Chandler says. “They announce that we have an emergency hemorrhage panel and then essentially the sample moves directly back. It’s rapidly spun down for two minutes. One sample goes to the cell counter and the other sample goes to the coag analyzer.” The tests are run and the results reported immediately.
“We basically worked with the trauma surgeons and the ED surgeons years ago to say, ‘Okay, if you are doing this testing, then we’ll take the sample you give us and we will run it instantly and whatever number we get, we’ll simply give it back to you.’” Part of what they did in the 2010 study is identify how frequently that tactic might lead to a problem, because if it’s a platelet count, he says, the laboratory staff “will look for flags on the instrument and they will make slides and review them for clumping—and do all these things to make a modest alteration in the count.”
The surgeons, however, just wanted to know whether the platelet count was above or below 100,000 per mL, which Dr. Chandler says was “the hard cutoff” for transfusion. “If we got a low value like below 100,000, we would always check for a clot, but if it was above that threshold, even if it might have been higher than that, [the physicians] didn’t care. They knew it was at least that high so that told them everything they needed to know.”
As was reported in the 2010 article, sometimes the assay has to be modified a bit. “I won’t go into the painful details of it, but the way the fibrinogen assay was set up, if the result was below 150 mg/dL, then the instrument would repeat it and then it would do another dilution and it would repeat that,” Dr. Chandler says. “And it could take you a half hour to get a low fibrinogen off the instrument because of all those checks it was doing.” To speed things up, they modified the fibrinogen assay so that it gave them results down to 50 mg/dL. “The doctors said that was fine. If they knew it was below 50, that was clearly more than they needed to decide whether they were going to transfuse the patient.”
Dr. Chandler says they studied it over the years and estimated that the laboratory was providing an erroneously low fibrinogen level about one in 2,000 times. The doctors said that was acceptable “because if you give them nothing, then they just treat the patient with everything.”
Dr. Chandler says he and colleagues did not include partial thromboplastin time in their EHP because it’s not as useful as PT. They studied that many years ago with the trauma center where they basically measured all of the coagulation factors and then asked which assay gave the best indication of a trauma patient’s overall coagulation factor level. The answer was prothrombin (Yuan S, et al. Thrombosis Res. 2007;120:29–37).
As for why PT won out, Dr. Chandler explained that the PTT is sensitive to high levels of factor VIII, which aren’t infrequent in trauma patients and “tend to mask other deficiencies in the PTT. It’s also sensitive to things like lupus inhibitors, which aren’t that common in trauma patients but there are more things that can interfere with the PTT than the prothrombin time, and so we didn’t do both.” A patient with hemophilia in trauma could be missed perhaps, but he says that hasn’t been an issue.
What impact has the panel had on outcomes? Dr. Chandler says the emergency hemorrhage panel “made for far more targeted therapy and the impression was reduced transfusion volume.
“But that was tricky to study,” he adds, “because you somehow had to match the patients over time and things change over time on how they even do the trauma resuscitation. So we never really studied outcome other than [the clinicians] were very happy because they were getting results where they weren’t getting them in the past.”
To set up all of the coagulation testing as point of care, Dr. Chandler says, some measure of the red cell count would be needed. “So you could do that with a hemoglobinometer or something. Some places will do a point-of-care prothrombin time. There are a number of instruments that people use for warfarin monitoring and they work okay as an estimate of prothrombin time in a trauma setting as well.”
Some institutions perform point-of-care testing using the TEG (thromboelastography) or ROTEM (rotational thromboelastometry). Dr. Chandler says he thinks it’s “quite reasonable” to use these to rapidly evaluate trauma patients: “You are not looking for a very precise measure of platelet count or fibrinogen or clotting time. You are looking for a gross estimation of whether the patient is severely depleted.”
“Point-of-care testing for trauma patients can work well,” Dr. Chandler concludes. “You have to have people available to do that 24 hours a day and some places are fully capable of doing that—Memorial Hermann did it in Houston—but in other places it may be a struggle.”
Karen Lusky is a writer in Brentwood, Tenn. The CAP course “Your Turn: Management of the Bleeding Patient” is cosponsored by the American Association of Blood Banks.