(From the May 2015 Issue of PediatricsOnline)
In a paper published in May 2015 in the journal Pediatric Anesthesia, researchers from Nationwide Children’s Hospital reviewed strategies to minimize blood transfusions and analyzed outcomes data for 209 patients undergoing congenital cardiac surgery with cardiopulmonary bypass.
Two major side effects of CPB that need to be managed by the surgical team are hemodilution and the damage that CPB does to the structural integrity of the platelets, which contributes to increased inflammation. These side effects have typically been managed by transfusing donor blood into the patient during and after surgery.
“We used a systematic approach using techniques and strategies for inflammation reduction and blood conservation, which resulted in a large number of bloodless surgeries,” says Mark Galantowicz, MD, co-director of The Heart Center at Nationwide Children’s and senior author on the recent publication.
Even though the safety of blood transfusions has increased considerably over time, there are still risks and side effects associated with receiving blood products from a donor, including allergic reaction, infection and increased edema and inflammation. Furthermore, the availability of allogeneic blood products is not guaranteed. Although it is generally agreed that the use of blood products should be limited, how to safely achieve this goal for children undergoing cardiac surgery is debated.
The team’s utilization of acute normovolemic hemodilution (ANH), a process in which a percentage of the total blood volume is drawn prior to bypass and returned to the patient after heparin reversal, was associated with a decreased number of transfusions for patients weighing between 6 and 18 kg in this study. ANH was used in 96 percent of patients weighing over 18 kg, and this group had the highest rate of bloodless operations at 81 percent.
“Our practice of ANH is unique in that we minimize crystalloid replacement during phlebotomy and use end-organ perfusion to guide fluid replacement,” Dr. Galantowicz explains. “Additionally, the blood collected in ANH has more intact platelets and fewer inflammatory markers because it does not circulate through the CPB circuit. This strengthens the patient’s ability to heal.”
Forty-four percent of the total cohort did not need blood products throughout their entire hospitalization. While all patients weighing less than 6 kg required a blood transfusion, 60 percent of the patients who weighed more than 6 kg did not.
Notably, those patients who received blood products had lower weight, younger age and higher risk-adjusted congenital heart surgery (RACHS) scores, all of which appear to correlate independently with increases in morbidity and mortality regardless of whether the patient received a blood transfusion.
The results presented in this study are consistent with prior studies referenced in the paper that conclude that accepting lower hematocrit as a transfusion threshold did not lead to worse clinical outcomes and, in some cases, led to better outcomes.
Part of the overall approach the team uses is to limit hemodilution, Dr. Galantowicz explains. By reducing the size of the CPB circuit, a smaller volume of blood is in the circuit at any given time. As an added benefit, miniaturized circuits decrease inflammation that results from the blood cells reacting to the foreign material of the CPB circuit.
“At Nationwide Children’s, we have the option of six different circuit sizes for cardiopulmonary bypass,” says Dr. Galantowicz, who also is professor of Surgery at The Ohio State University College of Medicine. “We are able to more closely match the circuit size to the body weight of the patient.”
To conduct the surgeries with minimal use of blood products, several whole-team strategies, in addition to ANH, are applied before, during and after bypass.
In an editorial in the same issue of Pediatric Anesthesiology, Glyn Williams, MD, professor of Anesthesiology, Perioperative and Pain Medicine at the Stanford University Medical Center, and Chandra Ramamoorthy, MD, professor of Anesthesiology, Perioperative and Pain Medicine at the Stanford University Medical Center, offer commendations to Nationwide Children’s for the blood conservation philosophy and program. However, they criticize how the cerebral and end organ perfusion is monitored and express concerns about potential risks to neurodevelopmental outcomes.
Dr. Galantowicz and his team plan to refine the techniques presented in this study and monitor the outcomes of patients on whom they are used. Additionally, recruitment has begun for prospective studies looking at the neurodevelopmental outcomes in patients undergoing single and double ventricle repairs.
Naguib AN, Winch PD, Tobias JD, Simsic J, Hersey D, Nicol K, Preston T, Gomez D, McConnell P, Galantowicz M. A single-center strategy to minimize blood transfusion in neonates and children undergoing cardiac surgery. Pediatric Anesthesia. 2015 May, 25(5):477-86.
Williams GD, Ramamoorthy C. Editorial comment on paper by Naguib, et al. A single-center strategy to minimize blood transfusion in neonates and children undergoing cardiac surgery. Pediatric Anesthesia. 2015 May, 25(5):442-44.