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Haste, no waste Bringing point-of-care coagulation to the OR

December 2001
Karen Titus

A simple transfusion algorithm often holds sway during cardiac surgery: Throw the blood bank at the patient.

Simple, yes. But also costly, inefficient, and potentially dangerous.

The dilemma is a familiar one. Abnormal bleeding is common in patients undergoing cardiopulmonary bypass, but pinpointing the cause is tricky—inadequate surgical hemostasis and irregularities in the coagulation system can all play a role. Compounding the problem, laboratory data are not always available in time to help determine treatment.

"Since we don’t know the cause of the bleeding, we give them everything, hoping that we’ll cover all the bases," says Gregory Nuttall, MD, associate professor of anesthesiology at Mayo Clinic.

"Is that right?" he asks. "No. But that’s what’s done."

Until now. Dr. Nuttall and his colleagues at Mayo are hoping to change the tried-but-not-always-true method of indiscriminate transfusions to treat excessive bleeding, in which patients receive simultaneous infusions of protamine, platelet concentrates, fresh frozen plasma, and even cryoprecipitate, alone or in combination.

The would-be savior is point-of-care coagulation testing. By year’s end Mayo planned to roll out such testing in cardiac surgery settings, using the CoaguChek Pro DM (Roche Diagnostics). Dr. Nuttall spoke about those plans, and about clinical use of POC testing in hemostasis, in an interview with CAP TODAY and in a talk he gave at the American Association for Clinical Chemistry’s annual meeting this summer.

As an end-user in the point-of-care world, Dr. Nuttall has one abiding interest: speed. "In the operating room, we have to make decisions within the time span of five to 10 minutes," he says. He also recognizes POC testing can be more convenient than conventional lab tests. And, like many laboratorians, he’s pleased with the small sample volumes required by POC testing.

He also echoes the reservations voiced by many laboratory professionals when he notes that POC testing can be more expensive than lab-based tests, at least on a simple cost-per-test basis. He sounds like a weary soldier from the regulatory front lines when he talks about training the users and maintaining their proficiency. As for billing—does this sound familiar?: "Reporting and billing are another big problem. It’s onerous. We’re still working that out at our institution."

When it comes to determining the best uses for POC testing, however, Dr. Nuttall freely admits his own bias. "I recognize there’s a lot of use for point-of-care testing outside the operating room, but the OR is what I’m interested in," he says.

In that setting, he says, two patient populations tend to benefit from POC testing. One group consists of those for whom standard tests are not available or are unusable. "Frequently, because the amount of anticoagulation we give is so high, the standard tests don’t work." The activated clotting time and the ecarin clotting time fall into this category. Patients with rapidly changing coagulation status are the other big beneficiaries of POC coagulation testing, especially those undergoing surgeries associated with large blood loss.

The broader implications are readily apparent. More than half the blood transfusions given in the United States occur in the OR or in the intensive care unit. Anywhere from 60 to 75 percent of heart surgery patients receive transfusions, says Dr. Nuttall, noting that these patients account for 10 to 20 percent of the red cells that are transfused in the United States each year, and for up to 50 percent of transfused platelets. "Somewhere between $5 billion and $7 billion is spent doing this each year," he says. Likewise, among coronary artery bypass graft patients, "47 percent of platelet transfusions are estimated to be inappropriate, almost a third of fresh frozen plasma that’s given is thought to be inappropriate, and about 15 percent of the red cells are inappropriate."

Certainly there’s plenty of room for improvement. Dr. Nuttall cites one study that looked at 18 institutions—in some places, nearly 100 percent of patients who underwent cardiac surgery received a transfusion; at another institution, the figure was less than 20 percent. That range is consistent with what Dr. Nuttall says he and his colleagues see when they visit other hospitals around the country. "Our suspicion is that a lot of these institutions aren’t using point-of-care testing to try to guide their transfusion therapy," he says.

It’s not for lack of advice. Of the many guidelines and consensus conferences that have addressed blood use issues, "Practically every one of them says we should go ahead and do coagulation testing to try to determine who should get blood."

With looming shortages and rising blood prices, hospitals soon may not have a choice.

At Mayo, the decision to move forward was a natural one. "We’ve had a lot of interest in minimizing blood loss in cardiac surgery, since these patients are such high users of transfusion," says Paula J. Santrach, MD, co-director of hospital clinical laboratories at Mayo and a member of the CAP Point-of-Care Testing Committee. "We’ve done studies on pharmaceutical agents, we’ve looked at various techniques in transfusion and blood salvage and blood donation, so it kind of evolved to looking at testing."

They were influenced, in part, by a study done by George Despotis, MD (Despotis GJ, et al. Transfusion. 1994;34:290-296), which looked prospectively at 66 cardiopulmonary bypass patients with microvascular bleeding. The patients were randomly assigned to one of two groups. In the standard therapy group, the use of lab-based data and the decision to transfuse blood components were at the physician’s discretion—"which basically means do whatever you want to do," says Dr. Nuttall. In the other group, patients were treated according to an algorithm based on POC coagulation testing data available within four minutes.

The algorithm was stratified, starting with a platelet count and followed by a PT and APTT. Using the algorithm, physicians were able to reduce FFP transfusions from a mean of 2.4 to 0.4 units; platelets were reduced from a mean of 6.4 to 1.6 units; and red cells, from 4.1 to 1.9 units.

It gets better. Despite receiving less blood in the operating room, patients did better—they bled less—in the ICU. "This is a prospective, randomized study that says, Maybe less is more," Dr. Nuttall says. "And using coagulation tests actually produces better care, and maybe saves money at the same time."

The study also noted another trend: fewer revisits to the OR. "If you have to go back to the operating room because you’re bleeding excessively, that increases your mortality, your morbidity, and massively increases your costs," Dr. Nuttall says.

Since cardiac surgery practices can vary significantly from one institution to the next, Mayo decided to conduct its own randomized trial. The results of this pilot study were published this spring in Anesthesiology (Nuttall GA, et al. 2001;94:773-781).

The researchers assigned 92 heart surgery patients with excessive, microvascular bleeding to either a standard therapy group (51 patients) or POC testing algorithm group (41 patients). The results were no less impressive. By instituting the algorithm in the OR, they saw a drop in the percentage of patients who were given platelets, FFP, and cryoprecipitate, alone or in combination, from more than 90 percent to approximately 30 percent. The rest of the patients either received no blood or were given only one type of non-red- blood-cell blood product. The gain was real, Dr. Nuttall says. "We didn’t have one of those things where you just shifted the place of transfusion; we didn’t bump it into the ICU."

Most important, in Dr. Nuttall’s view, is this: "We actually affected the overall hospital transfusion rate. We gave less blood, and these people bled less afterwards. We gave them more specific therapy, and we reduced the number of patients who had to go back for an operation."

Give less, spend less, provide better care—what’s to argue with?

On the surface, very little. But the usual POC hoops still need to be jumped through, and no one is about to crown POC testing as the king of diagnostics. Indeed, Dr. Nuttall quickly admits—doubtless to the chagrin of POC test manufacturers—that "these aren’t the best tests in the world. They’re not perfect." But without missing a beat he adds, "What we’re interested in is what works and what’s safe. And in general, these tests are pretty darn good."

Hospitals need to tread cautiously, however.

One of the biggest challenges is to reconcile POC data with laboratory data. "The results you get off the POC devices do not compare with the lab," Dr. Santrach says. "There’s definitely a bias, and you just have to accept that fact."

And find a way to work around it. Determining the cutoff point that defines bleeders and nonbleeders was a big part of Mayo’s pilot study. "You can’t just use the upper limit of normal, because it’s relatively common for cardiac patients to have abnormal PTs and APTTs," Dr. Santrach explains.

Adds Dr. Nuttall: "You have to redefine normal."

A good place to start might be one-and-a-half times the upper limit of normal, Dr. Santrach suggests. "But then you have to validate that, and make sure you’re at the right level. And every institution has to do this for themselves."

That information then has to travel beyond the laboratory. Dr. Santrach and her colleagues are making sure all anesthesiologists at their institution receive the POC algorithm; educating the surgeons will be another challenge. "But I think the most important thing is that people outside of cardiac surgery have to understand they cannot use this algorithm," she says. "It doesn’t apply to their patients. They have to figure out their own trigger."

Then there’s the evergreen matter of training personnel and maintaining QC. In fact, Dr. Nuttall reports that his institution decided to forgo—for now, anyway—use of a POC protamine titration instrument largely because the training and QC burdens don’t appear to offset the test’s gains.

With the new cardiac surgery POC testing algorithm, the personnel issues promise to be easier. "We’re going to use our autotransfusion team, which is already in the OR," Dr. Santrach says. This group already performs other POC coagulation tests, and they’re familiar with preanalytical issues. Another bonus: The group is small. "Fourteen people will be doing this test—that’s part of the reason we picked this group," Dr. Santrach says. "They’ll have enough activity to stay proficient, and there’s a limited number of people to do competency assessment on."

Will it be worth the effort? Dr. Santrach thinks so, though she can also understand why people may not want to bother. "It’s a challenge to make this work, no doubt about it.

"But I have a randomized clinical trial that shows these tests can do a good job," she continues. "These devices have a clinical utility regardless of what their CV performance is, or how they match in the lab. If you pick the right patient population, it’s very useful."

But other possibilities for coagulation POC testing abound. They run the gamut from the relatively rare cases of heparin-induced thrombocytopenia to major blood-loss surgeries. "That’s predominately four groups of people," says Dr. Nuttall. "People who are having heart surgery; liver transplant surgery or liver surgery because of liver dysfunction; big, big orthopedic surgeries, like multilevel back surgery; and maybe cancer. That’s where the big money is going to be in point-of-care testing."

For now, however, Mayo is sticking to cardiac surgery. "The short-term goal is challenging enough," says Dr. Santrach.

Karen Titus is CAP TODAY contributing editor and co-managing editor.