[Basic algorithm for Point-of-Care based hemotherapy: perioperative treatment of coagulopathic patients]

[Update on point-of-care-based coagulation treatment : Systems, reagents, device-specific treatment algorithms]

Viscoelastic test (VET) procedures suitable for point-of-care (POC) testing are in widespread clinical use. Due to the expanded range of available devices and in particular due to the development of new test approaches and methods, the authors believe that an update of the current treatment algorithms is necessary. The aim of this article is to provide an overview of the currently available VET devices and the associated reagents. In addition, two treatment algorithms for the VET devices most commonly used in German-speaking countries are presented.

Liver failure-future challenges and remaining questions

This review compiles the current state of controversial aspects of liver failure and outlines future challenges. The definition of acute liver failure (ALF) is widely accepted and implies no previous liver injury whereas the term "acute-on-chronic liver failure" remains contested. We will promote a concept, in which we differentiate three types of liver failure: ALF, acute-on-chronic liver failure (AOCLF) and acute-on-liver-cirrhosis (AOCi). The mechanistical insights into the coagulation system in patients with hepatic insufficiency have increased fundamentally in the past 10 years. Therefore, we follow now the concept of the so-called rebalanced hemostasis. This lower-level equilibrium arises from the fact that most coagulation factors and inhibitors are synthesized within the liver. We will demonstrate the advantage of viscoelastic test methods, which can assess the coagulation situation in patients with liver insufficiency much more precisely than conventional global coagulation tests. The therapeutic option of emergency liver transplantation (ELT) has significantly improved the prognosis of patients with ALF. However, limiting factors such as shortage of organs increase more and more the need for reliable prognostic markers. Due to a better understanding of the regenerative process during ALF new survival markers and prognostic tools have been emerging on the horizon in the last decade. Therefore, we will describe the current state of research in this field.

Detection of hypofibrinogenemia during cardiac surgery: a comparison of resonance-based thrombelastography with the traditional Clauss method

: Bleeding after cardiac surgery is associated with significant morbidity and mortality. Hypofibrinogenemia is a crucial factor for bleeding in this setting and may be rapidly detected using point-of-care viscoelastic tests (POC-VET). However, the correlation of POC-VET with conventional coagulation assays is still unclear. The current study aimed to correlate resonance-based POC-VET assays (Haemonetics TEG 6s) with the traditional nonrapid Clauss method. Another aim was to identify a cut-off value for the detection of hypofibrinogenemia (fibrinogen plasma level below 150 mg/dl) focusing on the maximum amplitude of the TEG 6s citrated functional fibrinogen (CFF) assay. Adult patients undergoing cardiac surgery were screened for inclusion in this single-centre retrospective cohort study. Inclusion criteria were the availability of a TEG assay and timely corresponding laboratory results. Calculation of a CFF-maximum amplitude (CFF-MA) cut-off value was performed using receiver operating curve analysis in the baseline cohort and validated in the control cohort. The best correlation with the Clauss method was observed for the CFF-MA (r = 0.77; P < 0.0001) compared with the citrate kaolin maximum amplitude assay (r = 0.57; P < 0.0001) and the citrate kaolin heparinase maximum amplitude assay (r = 0.67; P < 0.0001). A cut-off value of 19.9 mm for the CFF-MA was calculated [area under the curve 0.87 (95% confidence interval: 0.82-0.92; P < 0.0001)]. This cut-off value had a sensitivity of 81.8% and a specificity of 71.1% for identification of hypofibrinogenemia in the control cohort. The resonance-based thrombelastography analyser can identify hypofibrinogenemia. Future clinical studies should investigate whether cut-off value guided coagulation therapy with POC-VET may improve patient outcomes in patients who suffer from bleeding complications.

Platelet Function Disturbance During Veno-Venous ECMO in ARDS Patients Assessed by Multiple Electrode Aggregometry-A Prospective, Observational Cohort Study

Extracorporeal (veno-venous) membrane oxygenation (vvECMO) has been shown to have negative effects on platelet number and function. This study aimed to gain more information about the impact of vvECMO on platelet function assessed by multiple electrode aggregometry (MEA). Twenty patients with the indication for vvECMO were included. Platelet function was analyzed using MEA (Multiplate^®) before (T-1), 6 h (T0), one (T1), two (T2), three (T3), and seven (T4) days after the beginning of vvECMO. Median aggregational measurements were already below the normal reference range before vvECMO initiation. Platelet aggregation was significantly reduced 6 h after vvECMO initiation compared to T-1 and spontaneously recovered with a significant increase at T2. Platelet count dropped significantly between T-1 and T0 and continuously decreased between T0 and T4. At T4, ADP-induced platelet aggregation showed an inverse correlation with the paO2 in the oxygenator. Platelet function should be assessed by MEA before the initiation of extracorporeal circulation. Although ECMO therapy led to a further decrease in platelet aggregation after 6 h, all measurements had recovered to baseline on day two. This implies that MEA as a whole blood method might not adequately reflect the changes in platelet function in the later stages of extracorporeal circulation.

Rotational Thromboelastometry for Assessing Bleeding Complications and Factor XIII Deficiency in Cardiac Surgery Patients

We aimed to detect alterations and deficits in hemostasis during cardiac surgery with cardiopulmonary bypass (CPB) using point-of-care-supported coagulation analysis (rotational thromboelastometry, impedance aggregometry), in addition to single factor assays for the measurement of fibrinogen (FI) and factor XIII (FXIII) levels. Forty-one patients scheduled for elective cardiac surgery with CPB were enrolled in this observational study. Perioperative measurement (pre-, postheparin, 30-minutes before the end of bypass, 1-hourpostoperatively) of standard laboratory variables, additional rotational thromboelastometry (ROTEM; International GmbH, Munich, Germany), Multiplate analysis (Roche, Switzerland), and an assay of FXIII activity were performed as well as the collection of epidemiological data and blood loss. The FI and FXIII levels as well as the measured ROTEM and Multiplate parameters correlated weakly with the blood loss. Clotting time and maximum clot firmness (MCF) of the intrinsically activated ROTEM showed a good correlation (r_CT-INTEM = 0.378; P < .05, r_MCF-INTEM = 0.305; P < .05) with postoperative drainage loss, suggesting a dependence of blood loss on the initial intrinsic activity. Additionally, perioperative FI or FIBTEM levels and the FXIII levels correlated with each other. Intrinsically activated ROTEM showed a good correlation with postoperative drainage loss, thus suggesting a dependence of blood loss on the initial intrinsic activity and therefore facilitating clinicians to assess postoperative bleeding complications. Based on the FI level or the MCF_FIBTEM measured by ROTEM, it may also be possible to assess the FXIII concentration. Especially in chronically ill and massive bleeding cardiac surgery patients with significantly decreased FXIII levels, the knowledge of FXIII deficiency may help clinicians to treat coagulation disorders more adequately.

[Hemoglobin-oriented and coagulation factor-based algorithm : Effect on transfusion needs and standardized mortality rate in massively transfused trauma patients]

BACKGROUND

Bleeding and trauma-induced coagulopathy (TIC) are major contributors to death related to trauma in the first 24 h and the major preventable contributors. Early surgical therapy and aggressive correction of TIC are key steps to prevent death in patients suffering from hemorrhage. Therefore, a standard operating procedure (SOP) using a hemoglobin (Hb)-oriented and coagulation factor-based algorithm for early correction of TIC was introduced in this level 1 trauma center. This SOP uses the correlation of the Hb values measured in the trauma bay and standard coagulation tests as the basis for various aggressive coagulation therapies.

OBJECTIVE

The aim was to investigate the effectiveness of the SOP in trauma patients requiring massive transfusions. The main objective was the effect on the transfusion requirements and the standardized mortality ratio (SMR), the ratio of observed deaths to expected/predicted deaths, in the cohort of massively transfused trauma patients after introduction of the SOP compared with a historical cohort.

METHOD

A retrospective, single center study was carried out at a supraregional trauma center between 2005 and 2014. After introduction of the Hb-oriented, coagulation factor-based SOP for correction of TIC in 2011 a before/after comparison of all trauma patients requiring massive transfusions during trauma bay resuscitation and intensive care unit (ICU) admission was carried out. Main outcome parameters were the transfusion requirement and the SMR. The historical cohort of massively transfused trauma patients before introduction of the SOP (group 1) was compared with the cohort after introduction of the SOP (group 2). Furthermore, the two cohorts were compared regarding injury severity, expected death calculated with the revised injury severity classification (RISC), hemostatic results on trauma bay and ICU admission, clotting therapy and outcome.

RESULTS

Of the 952 patients investigated 86 (9%) required massive transfusion (45 in group 1 and 41 in group 2). Both groups were comparable regarding injury severity but showed slight differences in hemostatic results on trauma bay admission, with a trend to worse results in group 2. Differences were recorded for platelet count on trauma bay admission with significantly lower values in group 2. The RISC predicted a significant difference in the mortality rate (46.5% group 1 and 65.3% group 2) but no significant differences in the observed mortality (44.4% group 1 and 47% group 2) were recorded. The SMR decreased from 0.95 in group 1 to 0.72 in group 2, meaning that in group 1 from 21 predicated trauma deaths 20 occurred and in group 2 from 27 predicated trauma deaths 19 occurred. This difference is not statistically significant (p = 0.16) due to the small sample size but is clinically relevant. A significant reduction in the requirement of red blood cell transfusions (22.8 ± 8.1 units vs 17.6 ± 7.6 units) was achieved (p = 0.003). Significant differences between the groups were observed regarding frequency and quantity of the coagulation-promoting drugs. Compared with group 1 the SOP used in group 2 achieved significantly better hemostatic results on ICU admission for fibrinogen and Quick's value and a clear trend to better results for international normalized ratio (INR) and PTT.

CONCLUSION

The SOP based on coagulation factor values and standardized clotting therapy showed a clear trend to reduction of the SMR in massively transfused trauma patients. On the other hand the SOP achieved a significant reduction in the transfusion requirements and a significant improvement in the hemostatic results in the most severely injured patients. This can be interpreted as an effective use of coagulation factors in the early hospital treatment of trauma patients with ongoing bleeding.

[Impact of acute normovolemic hemodilution on primary hemostasis]

BACKGROUND

Acute normovolemic hemodilution (ANH) is performed with the intention to reduce the requirement for allogeneic blood transfusions. After preoperative withdrawal of whole blood, corresponding amounts of crystalloids and/or colloids are infused to maintain normovolemia. The main benefit of ANH is the availability of whole blood containing red blood cells, clotting factors and platelets for reinfusion after removal during the dilution process. Until retransfusion whole blood components are stored at the patient's bedside in the operating theatre.

AIM

It was the aim of the present investigation to analyze potential changes in ex vivo induced platelet aggregation in stored blood components.

MATERIAL AND METHODS

After obtaining approval 15 patients undergoing complex cardiac surgery were enrolled into this prospective observational study. Acute normovolemic hemodilution (ANH) was routinely performed in this collective based on institutional standards. Besides analyses of pH and plasma concentrations of ionized calcium and hemoglobin, hematological analyses included aggregometric measurements using multiple electrode aggregometry (MEA, Multiplate®, Roche, Grenzach, Germany). Ex vivo platelet aggregation was induced using arachidonic acid (ASPI test), as well as thrombin receptor activating peptide (TRAP test) and adenosine diphosphate (ADP test). Laboratory analyses were performed before beginning ANH (baseline), as well as immediately (T1), 30 min (T2), 60 min (T3), 90 min (T4), 120 min (T5), 150 min (T6) and 180 min (T7) after beginning of storage. The areas under the aggregation curves (AUC) in the MEA were defined as primary (ASPI test) and secondary endpoints (ADP test, TRAP test).

RESULTS

As compared to baseline, arachidonic acid induced platelet aggregation was significantly reduced at T1 [77 U (68/94 U) vs. 53 U (25/86 U), p = 0.003] and each consecutive measuring point. As compared to T1 (begin of storage), arachidonic acid induced platelet aggregation was significantly reduced at T4 [26 U (14/54 U); p = 0.002], T5 [30 U (21/36 U); p = 0.007], T6 [25 U (17/40 U); p = 0.004] and T7 [28 U (17/39 U); p < 0.001]. The extent of ex vivo induced platelet aggregation in the TRAP test and ADP test remained unchanged during the study period. The pH as well as the concentrations of ionized calcium and hemoglobin remained unchanged in the blood component during storage.

CONCLUSION

The results of the present study indicate that disturbances of platelet aggregation may occur during storage of whole blood components prepared for the purpose of ANH. Further investigations are needed to analyze whether the observed phenomena are of hemostatic relevance.