Point-of-care haemostasis and coagulation monitoring in cardiac surgery at IRCCS Policlinico San Donato

Minimal invasive extracorporeal circulation preserves coagulation integrity

INTRODUCTION

Coagulopathy after cardiac surgery is a serious multifactorial complication that results in postoperative bleeding requiring transfusion of red blood cells and procoagulant products. Use of cardiopulmonary bypass represents the major contributing factor affecting coagulation. We sought to prospectively investigate the effect of contemporary minimal invasive extracorporeal circulation (MiECC) on coagulation parameters using point-of-care (POC) rotational thromboelastometry and the relation to postoperative bleeding.

METHODS

Patients undergoing elective cardiac surgery on MiECC were prospectively recruited. Anticoagulation strategy was based on individualized heparin management and heparin level-guided protamine titration. Rotational thromboelastometry testing was performed before induction of anesthesia and after aortic cross-clamp release. A strict POC-guided transfusion protocol was implemented. The primary endpoint was the assessment of viscoelastic properties of the coagulating blood at the end of surgery compared to preoperative values and the relation to postoperative bleeding and 24-hour transfusion requirements.

RESULTS

Fifty patients were included in the study with a significant proportion having complex surgery. Thirteen patients (26%) required blood transfusion (mean rate: 0.5 ± 1 units per patient), 5/50 (10%) received coagulation factors while no patient received fresh frozen plasma, platelets or fibrinogen. Thromboelastometry analysis showed that the major derangement was CT EXTEM > 100 seconds in 28/50 (56%) and A10 EXTEM < 40 mm in one (2%) patient without clinical significance. Platelet function was preserved throughout surgery. A10-FIBTEM was found predictive of postoperative bleeding at 12 hours.

CONCLUSIONS

MiECC preserves clot quality throughout surgery acting in both key determinants of clot strength; fibrinogen and platelets. This is clinically translated into minimal postoperative bleeding and restricted use of blood products and coagulation factors.

Clinical and pathophysiologic aspects of ECMO-associated hemorrhagic complications

Extracorporeal membrane oxygenation (ECMO) is increasingly used to treat severe cases of acute respiratory or cardiac failure. Hemorrhagic complications represent one of the most common complications during ECMO, and can be life threatening. The purpose of this study was to elucidate pathophysiological mechanisms of ECMO-associated hemorrhagic complications and their impact on standard and viscoelastic coagulation tests. The study cohort included 27 patients treated with VV-ECMO or VA-ECMO. Hemostasis was evaluated using standard coagulation tests and viscoelastic parameters investigated with rotational thromboelastometry. Anticoagulation and hemorrhagic complications were analyzed for up to seven days depending on ECMO duration. Hemorrhagic complications developed in 16 (59%) patients. There were 102 discrete hemorrhagic episodes among 116 24-hour-intervals, of which 27% were considered to be clinically significant. The highest number of ECMO-associated hemorrhages occurred on the 2^nd and 3^rd day of treatment. Respiratory tract bleeding was the most common hemorrhagic complication, occurring in 62% of the 24-hour intervals. All 24-hours-intervals were divided into two groups: “with bleeding” and “without bleeding”. The probability of hemorrhage was significantly associated with abnormalities of four parameters: increased international normalized ratio (INR, sensitivity 71%, specificity 94%), increased prothrombin time (PT, sensitivity 90%, specificity 72%), decreased intrinsic pathway maximal clot firmness (MCFin, sensitivity 76%, specificity 89%), and increased extrinsic pathway clot formation time (CFTex, sensitivity 77%, specificity 87%). In conclusions, early ECMO-associated hemorrhagic complications are related to one traditional and two novel viscoelastic coagulation abnormalities: PT/INR elevation, reduced maximum clot firmness due to intrinsic pathway dysfunction (MCFin), and prolonged clot formation time due to extrinsic pathway dysfunction (CFTex). When managing hemostasis during ECMO, derangements in PT/INR, MCFin and CFT_ex should be focused on.

Multiple Electrode Aggregometry After Cardiopulmonary Bypass to Assess Platelet (Dys)-Function and Transfusion Threshold: A Concordance Study

OBJECTIVE

Cardiac surgery patients have a high risk of postoperative bleeding. Historically, the platelet count has been one of the main parameters used to establish the need for platelet transfusions, and the recent introduction of point-of-care tests for platelet function has allowed clinicians to rationalize platelet transfusion needs by assessing the platelet (dys-)function of the patient. For the present study, the authors evaluated how the introduction of one of these systems-the adenosine diphosphate (ADP) test, performed using a Multiplate electrode analyzer (Roche Diagnostics, Basel, Switzerland)-into their clinical practice had modified their platelet transfusion practice. The relationship between the platelet count and the functional evaluation of platelet aggregation (via the ADP test) also was examined.

DESIGN

This was a retrospective, single-center, observational study.

SETTING

Cardiac surgery department of a tertiary care center in North-east Italy.

PARTICIPANTS

Cardiac surgery patients requiring cardiac bypass in 2017 and 2019.

INTERVENTIONS

The primary outcome was to compare platelet transfusion practice before and after the implementation of a platelet function test (the ADP test) into the institution's transfusion algorithm, which replaced the platelet count as the trigger. Secondary outcomes were assessing whether the incorporation of the ADP test into their transfusion algorithm brought about a reduction in the frequency of platelet transfusions compared with previous rates (when only platelets counts were used); assessing patient blood loss in the first 12 postoperative hours; and ascertaining the percentage of patients requiring surgical reexplorations.

MEASUREMENTS AND MAIN RESULTS

The study comprised 110 patients undergoing cardiac surgery from the platelet count period (2017) and 110 patients from the ADP test period (2019). Agreement between platelet counts versus ADP tests in determining the need for platelet transfusion was moderate (κ = 0.483; 95% confidence interval [CI] 0.239-0.728), and the general linear regression relationship between platelet counts and the ADP test (Akaike information criterion = 2536; p < 0.001) was determined. Since the introduction of ADP testing, a highly significant reduction in platelet transfusions has occurred: 41.82% (platelet count period) versus 13.64% (ADP test period) (p < 0.001); average blood loss in the 12 hours postsurgery also was less in the ADP test period (p < 0.001) at 300 mL (95% CI 150-730) compared with 440 mL in the platelet count period (95% CI 135-900). Furthermore, a decreasing trend was observed in the number of patients requiring reexploration to optimize hemostasis in the first 12 hours postsurgery (6.36% v 2.73%); however, this trend did not achieve statistical significance (p = 0.195).

CONCLUSION

The application of new Multiplate analyzer technologies, like the ADP test, have the potential to reduce platelet transfusion rates in cardiac surgery patients compared with the use of platelet counts alone; this point-of-care test may constitute an important strategy to help spare the use of allogeneic blood products. Additional studies are needed to confirm this trend and establish the best cutoff values to apply.

Perspectives On Blood-Based Point-Of-Care Diagnostics

Background

Point of Care (POC) diagnostics are an essential component of modern medicine and are employed in a variety of clinical disciplines to improve patient outcomes and provider efficiency. Despite these benefits, there are aspects of POC testing which may still hold room for improvement. In the present study, a group of healthcare professionals familiar with different facets of blood-based POC testing provided their perspectives on the benefits and challenges of POC testing within their respective fields.

Materials and methods

The study was conducted from April to June 2019, in Colorado, United States of America. Five healthcare professionals, each working in a distinct field (anesthesiology, nursing, emergency medicine, trauma surgery, and POC management) were interviewed. Results from each of the interviews were transcribed as qualitative perspectives on POC diagnostics.

Discussion

The general consensus among participants in this study is that POC testing is tremendously beneficial, providing rapid test results, increased access to diagnostics, and improvements in hospital efficiency. However, significant challenges remain in blood-based POC diagnostics, particularly in maintaining sample quality, due to the fact that devices used for sample acquisition and handling are not designed for POC. This raises the possibility for interferents like hemolysis to occur, which may alter diagnostic results. Errors in POC diagnostics, whether due to sample, operator, or instrument error, may cause providers to lose confidence in the test. This lack of confidence can lead to duplicate testing and delayed patient diagnoses.

Conclusion

The perspectives presented in this study suggest there is a significant need for improvement in the pre-analytical phase of POC testing, and that current practice employs specimen collection technology not designed for POC. Therefore, one hypothesis is that the introduction of a collection device designed specifically for POC could reduce pre-analytical errors, standardize sample quality, improve efficiency, and further benefit patient care.