[Bedside thrombelastography. Cost reduction in cardiac surgery]

Thromboelastography During Rewarming for Management of Pediatric Cardiac Surgery Patients

BACKGROUND

Thromboelastography (TEG) predicts bleeding in pediatric patients undergoing cardiac surgery. We hypothesize that TEG parameters at rewarming correlate with post-protamine values and that rewarming TEG is associated with surrogate endpoints for postoperative bleeding in pediatric patients undergoing complex cardiac surgery.

METHODS

In a retrospective study of pediatric (≤18yrs) patients (N=703) undergoing complex cardiac surgery procedures, TEG obtained during rewarming and following protamine administration were compared using linear regression. A composite endpoint of extended blood product transfusion or surgical re-exploration for bleeding was utilized as a surrogate for post-operative bleeding.

RESULTS

By multivariable analysis, longer cardiopulmonary bypass time and lower TEG maximal amplitude (MA) during rewarming were independently associated with risk of composite endpoint in the operating room or intensive care unit (p<0.05). Among patients with MA<45mm during rewarming, those who received platelet transfusion compared to those who did not in the operating room were less likely to reach composite endpoint within the subsequent 24 hours (8%vs.32% respectively; p<0.01). Good correlation was observed between TEG parameters at rewarming vs. after protamine administration (Pearson r≥0.7). The relationship between platelet transfusion volume (ml/kg) and percent change in MA was determined using linear regression and a platelet transfusion calculator was generated.

CONCLUSIONS

Lower MA during rewarming is associated with increased risk of perioperative bleeding. In patients with rewarming MA<45mm, intraoperative platelet transfusion may reduce the risk of subsequent bleeding. Individualized platelet transfusion therapy based on rewarming TEG may reduce the risk of bleeding while minimizing unnecessary platelet transfusion.

Sample transport by pneumatic tube system alters results of multiple electrode aggregometry but not rotational thromboelastometry

Pneumatic tube systems (PTS) present a convenient way for blood sample transport in medical facilities. Associated preanalytical interference in various tests is largely unknown. Implementing point-of-care coagulation management at our institution, we investigated multiple electrode aggregometry (MEA) and rotational thromboelastometry (ROTEM) after PTS transportation. Whole blood samples from patients undergoing general or trauma surgery were analysed by MEA after collection (baseline, '0 × PTS') and sent on a predefined PTS track (n = 12). MEA was repeated after samples travelled the track 4 ('4 × PTS'), 8 ('8 × PTS') and 12 times ('12 × PTS') and compared with stationary controls analysed at the same time. Samples for ROTEM (n = 6) were analysed after collection and travelling the track 12 times. An acceleration detector recorded g-forces on the PTS track. At '0 × PTS' no significant differences in MEA results were detected. Values were significantly lower for transported samples compared with controls ('4 × PTS' to '12 × PTS', p < 0.001). Furthermore, MEA results of PTS samples were significantly decreased for '4 × PTS' to '12 × PTS' compared to baseline (p < 0.001). Except for the clotting time in EXTEM PTS transport did not significantly alter results for investigated ROTEM parameters, compared with baseline and stationary controls. Acceleration detector readout revealed alternating g-forces between -6.3 and +5.9 during transport. PTS transport caused invalid results in MEA while only one ROTEM parameter was found to be affected in this study. Variable acceleration during transport provides a potential reason for platelet activation. The authors recommend sample transport by hand or the device to be placed patient-side when MEA is performed.

Drug-induced blood consumption: the impact of adverse drug reactions on demand for blood components in German departments of internal medicine

Therapy for adverse drug reactions (ADRs) often results in the application of blood components. This study aims to assess the demand for blood components and the resulting economic burden (hospital perspective) in German hospitals induced by ADRs leading to admissions to departments of internal medicine. In this prospective study, ADRs leading to hospitalization were surveyed in four regional pharmacovigilance centres in Germany during the years 2000-2007. ADRs assessed as 'possible', 'likely' or 'very likely' were included. Market prices for blood components and hospitalization data were determined by desktop research. A probabilistic sensitivity analysis was performed. A total of 6099 patients were admitted to internal medicine departments because of an outpatient ADR of whom 1165 patients (19.1%; mean age, 73.0 ± 13.0 years) required treatment with blood components owing to major bleeding events. Overall consumption was 4185 erythrocyte concentrates (EC), 426 fresh frozen plasma (FFP) and 48 thrombocyte (TC) units. On the basis of statistical hospital data, we estimated a nationwide demand of approximately 132,020 EC, 13,440 FFP and 1515 TC units, resulting in total costs of €12.66 million per year for all German hospitals. Some 19.2% of all ADR cases were assessed as preventable. Theoretically, a nationwide decreased demand for blood components and a savings potential of €2.43 million per year could be achieved by preventing ADRs in Germany. Blood components are used in one-fifth (mainly gastrointestinal bleeding) of all ADRs, leading to hospitalizations in internal medicine departments. Both blood demand and hospital procurement costs can be significantly lowered by preventing ADRs.

Coagulation abnormalities in the trauma patient: the role of point-of-care thromboelastography

Current recommendations for resuscitation of the critically injured patient are limited by a lack of point-of-care (POC) assessment of coagulation status. Accordingly, the potential exists for indiscriminant blood component administration. Furthermore, although thromboembolic events have been described shortly after injury, the time sequence of post-injury coagulation changes is unknown. Our current understanding of hemostasis has shifted from a classic view, in which coagulation was considered a chain of catalytic enzyme reactions, to the cell-based model (CBM), representing the interplay between the cellular and plasma components of clot formation. Thromboelastography (TEG), a time-sensitive dynamic assay of the viscoelastic properties of blood, closely parallels the CBM, permitting timely, goal-directed restoration of hemostasis via POC monitoring of coagulation status. TEG-based therapy allows for goal-directed blood product administration in trauma, with potential avoidance of the complications resulting from overzealous component administration, as well as the ability to monitor post-injury coagulation status and thromboprophylaxis. This overview addresses coagulation status and thromboprophylaxis management in the trauma patient and the emerging role of POC TEG.

Alternative procedures for reducing allogeneic blood transfusion in elective orthopedic surgery

Perioperative blood loss is a major problem in elective orthopedic surgery. Allogeneic transfusion is the standard treatment for perioperative blood loss resulting in low postoperative hemoglobin, but it has a number of well-recognized risks, complications, and costs. Alternatives to allogeneic blood transfusion include preoperative autologous donation and intraoperative salvage with postoperative autotransfusion. Orthopedic surgeons are often unaware of the different pre- and intraoperative possibilities of reducing blood loss and leave the management of coagulation and use of blood products completely to the anesthesiologists. The goal of this review is to compare alternatives to allogeneic blood transfusion from an orthopedic and anesthesia point of view focusing on estimated costs and acceptance by both parties.

Impact of platelet count on results obtained from multiple electrode platelet aggregometry (Multiplate)

OBJECTIVES

Use of potent antiplatelet drugs requires evaluation of platelet function. While platelet function in elective cases is usually assessed in a central laboratory environment, there is also an urgent need for rapid perioperative point-of-care assessment. Recently, multiple electrode platelet aggregometry has been developed and assumed to measure platelet function independent from platelet count. We tested the hypothesis that results of multiple electrode platelet aggregometry are affected by platelet count, in particular if platelet count is below normal range.

METHODS

Whole blood samples from 20 healthy volunteers were prepared containing platelet concentrations of 50,000, 100,000, 150,000, 200,000, and 250,000 microl(-1) while maintaining hematocrit. Platelet aggregation was induced by collagen, thrombin receptor activating peptide 6 (TRAP-6), adenosine-diphoshate (ADP), and arachidonic acid, respectively, and aggregation was measured by multiple electrode platelet aggregometry (Multiplate).

RESULTS

Results of multiple electrode platelet aggregometry significantly decreased in blood samples with platelet count below normal range. Compared to results measured in blood samples with platelet count within normal range, aggregometry results decreased by 18.4 % (p<0.001) and 37.2 % (p<0.001) in blood samples with a platelet count of 100.000 and 50.000 microl(-1), respectively. On the other hand, large interindividual variation has been observed and some blood samples showed normal results even with platelet counts of 50.000 microl(-1).

CONCLUSION

The results obtained with Multiplate. Analyzer are influenced by platelet function as well as platelet count thus displaying the overall platelet aggregability within the blood sample rather than platelet function alone.