Are We Exposing Neonates To More Blood Products Than Necessary During Open-Heart Surgery Hospitalizations?
Susan Nicolson, James DiNardo, Lindsey Loveland Baptist, Viviane Nasr
Original article
Bohuta L, Charette K, Chan T, Joffe D, Koth A, Greene CL, Mauchley D, McMullan DM. Encouraging results of blood conservation in neonatal open-heart surgery. J Thorac Cardiovasc Surg. 2023 Jul 29:S0022-5223(23)00637-2. doi: 10.1016/j.jtcvs.2023.07.032. Epub ahead of print. PMID: 37517580.
Blood product transfusion is a life-saving therapy with known risks and potential complications. Historically, blood transfusion was considered an unavoidable component of open-heart surgery. With recognition that responsible blood management is essential for continued improvement in clinical outcomes, blood conservation has been successfully applied in adult cardiac surgery. Blood conservation has lagged in pediatric practice. As recently as 2018, data from The Society of Thoracic Surgeons showed that median blood transfusion rates during open-heart surgery were >99.5% among infants and 100% among neonates.1 Recent case reports and small series have shown that transfusion-free neonatal and infant open-heart surgery is possible, yet rarely achieved even by experienced blood conservation teams.2
A multi-disciplinary blood conservation program was established at Seattle Children’s Hospital Heart Center in May 2021 to optimize patients’ blood management.3 The authors report the retrospective review of their initial experience and early outcomes in 99 neonates who received either usual blood management or blood conservation management between May 2021 and February 2023. Understanding which neonates might be suitable candidates for blood conservation evolved during the study. Initially, blood conservation was attempted by a limited number of team members in larger neonates with higher baseline hematocrits undergoing less complex surgical procedures. By the end of the study period blood conservation was undertaken by all team members in the vast majority of neonates with exclusion criteria almost exclusively limited to: 1. weight < 2.5 kg, 2. pre-operative hematocrit < 35% and 3. hemodynamic instability (hypotension, desaturation, or arrhythmia) in the prebypass period. The evolution of the approach to blood management during the study period is depicted in Figure 1.
The unique elements of blood conservation by the Seattle team included:
1. Re-configuration of the bypass circuit to require only 136 ml of a balanced crystalloid solution as the pump prime volume to minimize hemodilution
2. TXA was run throughout the procedure at 5 mg/kg/hour after a bolus of 50 mg/kg
3. Autologous priming of the arterial and venous limbs of the bypass circuit
4. Cardioplegia 20 ml/kg
5. Hematocrit on bypass targeted at 24%, which was the threshold for transfusion of RBCs during bypass
6. Cardiac index was targeted at 2.4L/m2/minute with a mean arterial blood pressure goal of 33-35 mm Hg while on bypass
7. Both conventional and modified ultrafiltration were performed
8. Post-bypass and post-operative hematocrit values of 21% and 27% were used as thresholds for transfusion of RBCs in hemodynamically stable bi-ventricular and single ventricle patients respectively
9. Bleeding was assessed clinically, and blood products were not administered when hemostasis was “appropriate”, regardless of lab values
10. Neonates who left the OR without transfusion of RBCs received a single dose of IV iron on POD#1 and were started on oral iron when enteral feeds were re-started
Patients in the two groups were similar in age at surgery, preoperative weight, STAT category, bypass and aortic cross clamp times.
Of the 99 neonates, blood conservation was attempted in 56 and not in 43. Twenty two of the 56 neonates (39%) left the OR without any transfusion. The majority (5 out of 8) of the neonates who left the OR with no transfusion, but subsequently received RBCs, were transfused in the first 24 hours after surgery. Thirty six out of the 56 left the operating room without transfusion of any non-RBC blood products (FFP, platelets, cryoprecipitate). None of the neonates in the blood conservation arm received prothrombin complex or recombinant factor VIIa, or required re-exploration for bleeding. Fourteen neonates (25%), including a neonates who underwent the Norwood operation, achieved a transfusion-free hospitalization, notably higher than previously reported.3
Blood conservation was not associated with higher serum lactate levels during bypass or in the first 24 hours after surgery. Early postoperative electroencephalograms showed no seizure activity among the transfusion-free neonates. Postoperative mechanical ventilation time and postoperative ICU length of stay were shorter in the neonates in the blood conservation arm.
This study has the limitations inherent to retrospective studies, coupled with a relatively small sample size of convenience in a single center, which may limit generalizability of the results. Specifically, the CPB flow rates and target MAPs used in this protocol are below the target thresholds employed in other institutions. In addition, the description that “Short-term decreases in Hct to a value <24% were tolerated if other markers of oxygen delivery remained within range and Hct could be returned to > 24% with ultrafiltration in <3 minutes” leaves the reader wondering what other markers of oxygen delivery were utilized (DO2 on CPB, NIRS values), what threshold values elicited intervention, and what were the specifics of the subsequent interventions. We do not know, for instance, if liberal vasopressor administration was utilized to facilitate retrograde autologous priming and to maintain MAP on CPB. For many institutions, the interventions necessary to replicate this protocol may prove to be an impediment to its adoption.
In spite of study design deficiencies, the data adds another example whereby blood transfusion can be minimized or completely avoided in neonates undergoing open-heart surgery. Early clinical outcomes are favorable but long-term follow-up and continued efforts to limit or eliminate blood exposure during hospitalizations for neonatal cardiac surgery are needed to prove both safety and reproducibility.
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References
1. Kartha VM, Jacobs JP, Vener DF, et al. National Benchmarks for Proportions of Patients Receiving Blood Transfusions During Pediatric and Congenital Heart Surgery: An Analysis of the STS Congenital Heart Surgery Database. Ann Thorac Surg 2018;106(4):1197-1203. (In eng). DOI: 10.1016/j.athoracsur.2018.04.088.
2. Boettcher W, Schulz A, Sinzobahamvya N, et al. Coagulation Profile of Neonates Undergoing Arterial Switch Surgery With Crystalloid Priming of the Cardiopulmonary Bypass Circuit. Journal of cardiothoracic and vascular anesthesia 2022;36(6):1598-1605. (In eng). DOI: 10.1053/j.jvca.2021.08.006.
3. Bohuta L, Charette K, Chan T, et al. Encouraging results of blood conservation in neonatal open-heart surgery. The Journal of thoracic and cardiovascular surgery 2023 (In eng). DOI: 10.1016/j.jtcvs.2023.07.032.