To the Editor I read with interest the recent article by Goobie et al1 and the accompanying Editorial by Higgins et al.2 While I support the concept of preoperative optimization (including hematocrit where appropriate), I could not agree more with the significant limitations of the study that were highlighted in the Editorial. While I acknowledge that the independent association between low hematocrit and mortality cannot be refuted on statistical grounds, to not have included underlying surgical diagnosis as a confounding variable appears to represent a significant methodological flaw. I note that most infants underwent a “general surgical” procedure that may have ranged in severity from elective inguinal hernia repair to emergent laparotomy for fulminant necrotizing enterocolitis. On closer inspection of the cohort of 93 infants who died in the hospital, we find that 63% weighed less than 2 kg, 69% were preterm, 82% of procedures were emergent, and 51% underwent an intraoperative transfusion. These figures suggest a much greater severity of illness owing to underlying diagnosis in infants who died than survivors, which may be (1) cause for low hematocrit and (2) an independent risk factor for mortality. High mortality3 is a feature of necrotizing enterocolitis, a diagnosis that is likely to have been present in a good number of nonsurvivors given the population demographics and clinical features. As emphasized in the Editorial, American Society of Anesthesiologists classification of 3 to 5, preoperative mechanical ventilation, and preoperative inotrope support all had odds ratios for mortality higher than the odds ratios for low hematocrit, and all were statistically significant on multivariate analysis. To ignore surgical pathology and select anemia alone as a focus for increased mortality risk would seem inappropriate and a significant oversimplication.
Hall NJ. Association of Preoperative Anemia With Postoperative Mortality in Neonates. JAMA Pediatr. 2017;171(2):196. doi:10.1001/jamapediatrics.2016.2962