Low hemoglobin levels are associated with increased hospital length of stay (LOS) in children with congenital cyanotic heart disease undergoing surgical intervention. Nevertheless, the low hemoglobin levels had no effect on length of intubation or in-hospital mortality.
“Although much has been reported in the literature for cardiac and noncardiac surgery in adults regarding transfusion triggers for red blood cells, very little has been reported for pediatric cardiac surgery patients, especially those with cyanotic lesions,” said Jennie Y. Ngai, MD, assistant professor of anesthesiology, perioperative care and pain medicine at NYU Langone Medical Center, in New York City.
“Clinicians have always tried to maintain a higher hemoglobin level in cyanotic cardiac patients. In our study, we aimed to find a hemoglobin level where complications and hospital length of stay might increase.”
As Dr. Ngai explained, cyanotic lesions constitute 30% of all congenital heart disease cases. Although red blood cell transfusion commonly plays an integral role in the management of adults with the disease, perioperative transfusion strategies and optimal hemoglobin concentrations have not been well described in children.
Furthermore, previous studies attempting to define a transfusion threshold in pediatric patients undergoing cardiac surgery have either omitted those with cyanotic disease or included only a narrow spectrum of lesions in their analysis. The investigators hypothesized that decreased hemoglobin concentrations in these children would be associated with increased rates of adverse perioperative events.
Higher Hemoglobin Lowers Hospital LOS
To help answer some of these questions, Dr. Ngai and her colleagues reviewed data on 153 children with cyanotic congenital heart disease who underwent a total of 199 surgical procedures at the institution between June 2013 and September 2015. Multivariate regression analyses were performed to determine the effects of various patient and surgical factors on hospital LOS, intubation time and in-hospital mortality.
As Dr. Ngai reported at the 2017 annual meeting of the American Society of Cardiovascular Anesthesiologists (abstract SCA85), high hemoglobin levels were found to be associated with shorter hospital LOS (P<0.001), as was increasing weight (P=0.015). Regression tree analysis demonstrated that, in children weighing at least 4.8 kg, those with a hemoglobin level of at least 6.4 mg/dL had a sixfold decrease in hospital LOS (11 days) compared with their counterparts with a hemoglobin level less than 6.4 mg/dL (63 days).
“However, even with the variation in hemoglobin levels, there was no difference in in-hospital mortality,” Dr. Ngai told Anesthesiology News. “This implies that perhaps cyanotic cardiac patients can withstand a lower hemoglobin level better than originally thought.”
The results also raised questions with respect to the benefits of transfusion and the importance of its timing in this fragile patient population. “The body naturally produces more red cells in response to cyanosis,” Dr. Ngai said. “So given that transfusion of red cells carries some risk and may not be immediately beneficial, is it better to try to withhold transfusion until the hemoglobin reaches a certain level?
“Yet even though our study showed no difference in hospital mortality with lower hemoglobin levels, I wouldn’t necessarily recommend that clinicians allow these patients to drop down that low,” she said. “I think more studies need to be performed before we make any major changes in our practice.”
To that end, the researchers plan to continue their research efforts on the topic, hopefully in a prospective manner. “Some of the low hemoglobin levels we found were from bleeding, so complications may have been related to surgery rather than low hemoglobin levels,” she added. “Also, the length of time of the low hemoglobin was not accounted for.”
As Andrew Matisoff, MD, told Anesthesiology News, the results of the study—combined with other recent research—may have changed clinicians’ perspectives on transfusion targets. “For years, pediatric anesthesiologists have practiced under the assumption that patients with cyanotic heart disease require higher hemoglobin levels to improve oxygen delivery, often transfusing to levels as high as 12 mg/dL,” said Dr. Matisoff, who is assistant professor of cardiac anesthesia at Children’s National Health System, in Washington, D.C.
“This study by Dr. Ngai correlates with other recent studies demonstrating that perhaps we have been overshooting on our hemoglobin levels. Clinicians can safely lower our transfusion targets in patients with cyanotic congenital heart disease without increasing mortality.”