Thromboelastography-guided Intraoperative Platelet Transfusion in Pediatric Heart Surgery.
Emani S, Donahue R, Callender A, Ghebremichael M, Nathan M, Ibla JC, Emani S.Ann Thorac Surg. 2024 Dec;118(6):1271-1278. doi: 10.1016/j.athoracsur.2024.09.003. Epub 2024 Sep 12.PMID: 39277157
Commentary By:
David Preston, DO
Children’s Medical Center, Dallas TX
Take Home Points
- What is already known
Intraoperative viscoelastic testing in pediatric cardiac surgery can assist in targeted blood product transfusion to reduce post-operative bleeding complications.
What this study adds
- A TEG-MA-driven calculator of appropriate platelet transfusion volume enables a patient-specific approach to platelet transfusion after cardiopulmonary bypass.
- A target TEG-MA of at least 45mm in conjunction with a fibrinogen level >190mg/dL was determined to be ideal to minimize risk of post-operative bleeding.
- Incorporating a calculator utilizing viscoelastic testing into an overall transfusion algorithm has the potential for more effective and responsible transfusion practices.
Navigating the balance of hemostasis with appropriate blood product utilization is a critical task for the pediatric cardiac anesthesiologist. The use of viscoelastic testing has allowed a more targeted approach to product transfusion after cardiopulmonary bypass (CPB).1 This study from Boston Children’s Hospital presents the validation of a TEG-MA-guided platelet transfusion calculator to decrease post-operative bleeding complications after CPB.2
Summary of the Study
The authors conducted a single center retrospective analysis of patients 18 years or younger who underwent procedures involving CPB at Boston Children’s Hospital. Notably, patients who received any cryoprecipitate, fresh frozen plasma (FFP), or factor VIIa during the perioperative period were excluded. Thromboelastography maximum amplitude (TEG-MA) data during both the rewarming phase of CPB and on arrival to the ICU were evaluated in conjunction with the volume of platelets administered after CPB. Post-operative bleeding was defined as the administration of any blood products or surgical re-exploration for bleeding within 24 hours. The incidence of any thrombotic events was followed for the duration of the hospitalization. The calculated volume of platelets required to achieve a TEG-MA of at least 45mm and less than 60mm was compared with the actual administrated volume of platelets during the case in order to classify each patient as under-transfused or over-transfused.
A total of 1000 cases over a 22-month period were evaluated. Comparison of calculator-predicted TEG-MA values (based on warming TEG-MA values and platelet transfusion volume) with actual post-operative TEG-MA values revealed a moderate correlation of the TEG-MA calculator with actual post-operative values (Pearson r = 0.7). Plotting post-operative bleeding percentages against post-operative TEG-MA values revealed an optimal TEG-MA of at least 45mm to prevent post-operative bleeding complications. The factors independently associated with post-operative bleeding complications were a TEG-MA < 45mm, an administered platelet volume determined as an undertransfusion (calculated resultant TEG-MA <45mm based on volume of platelets administered), and a fibrinogen level of <190mg/dL. In multivariate analysis, there was no association of a TEG-MA value with post-operative thrombotic complications. The authors acknowledge both the modesty of the association achieved with the platelet calculator as well as the multifactorial nature of post-operative bleeding and thrombotic events complicating this analysis.
What Does This Mean for Our Practice?
Algorithms utilizing viscoelastic testing during CPB to guide post-CPB transfusion practices are common.3,4 However, the development of a calculator to dictate a platelet volume based on a goal viscoelastic parameter adds a new layer of elegance and precision to transfusion practice. The ability to calculate an exact platelet volume necessary to correct coagulopathy and minimize the risk of post-operative bleeding presents an opportunity to spare the neonate or small infant from unnecessary hemodilution from over-transfusion of platelets and minimize their untoward effects.5 Conversely, this approach may also prevent excess blood loss from inadequate correction of coagulopathy secondary to an initial under-transfusion of platelets. However, the precision here does depend heavily on the validity of the TEG-MA value of 45mm determined to be the minimum goal for prevention of post-operative bleeding complications. And even with external validation, this value would only be applicable to those centers utilizing TEG 6s® for viscoelastic testing.
An interesting facet of this study is the exclusion of patients receiving cryoprecipitate and FFP to isolate the effect of platelets on TEG-MA values. While it is necessary to capture the validity of the calculator, it would be helpful to determine if this optimal TEG-MA of 45mm is independent of the relative contribution of platelets or fibrinogen to the maximum amplitude. This question is partially answered in the determination that a fibrinogen level of <190mg/dL was independently associated with bleeding complications. But what about settings in which fibrinogen supplementation contributes to a TEG-MA >45mm, yet platelet dysfunction may still exist? Would this shift the optimal TEG-MA? Hopefully, this study opens the door to continued refining and expansion of such calculators to each component of a viscoelastic test.
It is important to remember that, as our ability to normalize coagulation parameters becomes more elegant and precise, the post-CPB phase remains anything but elegant, requiring balanced resuscitation of ongoing surgical bleeding while correcting coagulopathy. There will always be some degree of mud in the water with regard to achieving perioperative hemostasis in pediatric cardiac surgery, yet this study demonstrates a useful and targeted approach to minimizing exposure to blood products.
References
- Emani S, Sleeper LA, Faraoni D, Mulone M, Diallo F, DiNardo JA, Ibla J, Emani SM. Thromboelastography Is Associated With Surrogates for Bleeding After Pediatric Cardiac Operations. Ann Thorac Surg. 2018 Sep;106(3):799-806. doi: 10.1016/j.athoracsur.2018.04.023. Epub 2018 May 16. PMID: 29753821.
- Emani S, Donahue R, Callender A, Ghebremichael M, Nathan M, Ibla JC, Emani S. Thromboelastography-guided Intraoperative Platelet Transfusion in Pediatric Heart Surgery. Ann Thorac Surg. 2024 Dec;118(6):1271-1278. doi: 10.1016/j.athoracsur.2024.09.003. Epub 2024 Sep 12. PMID: 39277157.
- Faraoni D, Willems A, Romlin BS, Belisle S, Van der Linden P. Development of a specific algorithm to guide haemostatic therapy in children undergoing cardiac surgery: a single-centre retrospective study. Eur J Anaesthesiol. 2015 May;32(5):320-9. doi: 10.1097/EJA.0000000000000179. PMID: 25387300.
- Romlin BS, Wåhlander H, Berggren H, Synnergren M, Baghaei F, Nilsson K, Jeppsson A. Intraoperative thromboelastometry is associated with reduced transfusion prevalence in pediatric cardiac surgery. Anesth Analg. 2011 Jan;112(1):30-6. doi: 10.1213/ANE.0b013e3181fe4674. Epub 2010 Nov 3. PMID: 21048096.
- Van Hout FM, Hogervorst EK, Rosseel PM, van der Bom JG, Bentala M, van Dorp EL, van Geloven N, Brand A, van der Meer NJ, van de Watering LM. Does a Platelet Transfusion Independently Affect Bleeding and Adverse Outcomes in Cardiac Surgery? Anesthesiology. 2017 Mar;126(3):441-449. doi: 10.1097/ALN.0000000000001518. PMID: 28092320.
