Usefulness of Standard Plasma Coagulation Tests in the Management of Perioperative Coagulopathic Bleeding: Is There Any Evidence?
Reprinted with permission from David Slater, M.D., Community Regional Medical Center Lab Medical Director. Dr. Slater wrote this Laboratory Update article for the Community Medical Centers Physicians’ Edition newsletter, January 2016.
This study in the British Journal of Anaesthesia (vol 114 (2): 217–24 ) closely examined the utility of standard coagulation assays (PT and PTT) to predict abnormal bleeding. These are among the most commonly ordered tests in acute care hospitals, and this is an every-day question faced by clinicians in those hospitals – so this is important information.
You may remember that traditional coagulation tests (notably, PT/INR) were not designed to predict coagulopathic bleeding risk from surgery or a procedure. A long INR often responds poorly to plasma transfusion in part because the INR of thawed plasma may be up to 1.4. Only a substantially prolonged INR (generally, at least 2.0) signifies risk for factor depletion (<30%) significant enough to cause coagulopathy. The relationship between % factor activity and INR is not linear. Transfusion of coagulation factors will shorten a markedly prolonged INR e.g., an INR of 5) much more than a mildly prolonged INR e.g., an INR of 1.7).
The Article includes this Summary:
“Standard laboratory coagulation tests (SLTs) such as prothrombin time/INR or partial thromboplastin time are frequently used to assess coagulopathy and to guide haemostatic interventions. However, this has been challenged by numerous reports, including the current European guidelines for perioperative bleeding management, which question the utility and reliability of SLTs in this setting. Furthermore, the arbitrary definition of coagulopathy (i.e. SLTs are prolonged by more than 1.5- fold) has been questioned.
The present study aims to review the evidence for the usefulness of SLTs to assess coagulopathy and to guide bleeding management in the perioperative and massive bleeding setting. Medline was searched for investigations using results of SLTs as a means to determine coagulopathy or to guide bleeding management, and the outcomes (i.e. blood loss, transfusion requirements, mortality) were reported. A total of 11 guidelines for management of massive bleeding or perioperative bleeding and 64 studies investigating the usefulness of SLTs in this setting were identified and were included for final data synthesis.
Referenced evidence for the usefulness of SLTs was found in only three prospective trials, investigating a total of 108 patients (wherein microvascular bleeding was a rare finding). Furthermore, no data from randomized controlled trials support the use of SLTs. In contrast, numerous investigations have challenged the reliability of SLTs to assess coagulopathy or guide bleeding management. There is actually no sound evidence from well-designed studies that confirm the usefulness of SLTs for diagnosis of coagulopathy or to guide haemostatic therapy.”
Of interest to those who order transfusions at CRMC is that the authors advocate ROTEM (or the similar TEG instrument) in preference to SLTs to achieve a stronger predictive value for procedural bleeding propensity and to guide plasma and cryoprecipitate transfusion decisions. CRMC’s trauma and cardiac services do make extensive use of this technology, and are encouraged to continue to use it to guide coagulation factor (plasma, cryoprecipitate) and platelet transfusion decisions.
For all our readers, the message is to not regard with too much reverence, the relationship between INR and bleeding propensity, nor to over-aggressively transfuse plasma or defer needed care on the basis of a modestly long INR. Yes you can find older guidelines based on “we got a bunch of white haired guys in a room (no, not our esteemed Dr. Dominic – some other guys) and this is what they say” approaches – but the evidence just isn’t there.
Practically speaking, all US hospitals still refer to standard coagulation tests in their transfusion guidelines – no one has jettisoned these tests completely for the purposes of ordering plasma – though European guidelines are getting there. But in recent years, widespread recognition of their limitations – along with increasing recognition of the risks of transfused plasma (immune modulation, infectious and respiratory consequences, fluid overload, allergic reactions) – has lead most hospitals and expert guidance to “dial up” the INR levels at which plasma transfusions should be considered in various scenarios. Community has done the same, though not as aggressively as some other facilities. Readers are advised to be familiar with our guidelines (which are embedded in the transfusion set as plasma is ordered for anything other than a massive transfusion).
The authoritative American Association of Blood Banks (AABB) reached this conclusion in 2012 after rigorous review of the evidence:
“…80 randomized controlled trials have investigated frozen plasma with no consistent evidence of significant benefit for prophylactic and therapeutic use across a range of indications evaluated…”
And “…While many physicians transfuse plasma based on coagulation testing (e.g., prothrombin time and international normalized ratio), data from the available clinical studies did not allow outcomes of plasma transfusion to be correlated with differences in the degree of coagulopathy (based on this testing)…” (Ann Intern Med 2012; 157:49-58)
Here’s a high level snapshot of how CMC facilities use plasma compared to other US hospitals. Our use is compared to identically MSDRG-coded care at dozens of other hospitals (there are over 5 million transfusions in the benchmark data base, from within past 2 years). The charts display units transfused over and above the mean of the benchmark data set, for same mix of care (as closely as that can be compared among different facilities at an MSDRG level) – designated “opportunity” units. Note: While the focus of this article is on plasma, other components are well represented in our opportunity pies.
Author: David Slater, M.D.