Association between preoperative hemoglobin levels after iron supplementation and perioperative blood transfusion requirements in children undergoing scoliosis surgery.

At a single Canadian institution, all children undergoing posterior spinal fusion surgery routinely present to a preoperative patient blood management clinic where they are prescribed iron supplementation. This takes varying forms depending on the patient.

Patients were excluded if no blood count was available or if they had been transfused within 72 hours of surgery.


The primary endpoint was association between preoperative Hb level and perioperative exposure to red cells in patients treated with iron supplementation. Secondary endpoints were to:

  1. Define a threshold Hb that results in significantly reduced probability of red cell transfusion
  2. Examine details of supplemental iron prescription



  • 382 patients were included:
    • Median age 15
    • 291 (76.2%) were female
    • 263 (68.8%) had idiopathic scoliosis


  • Median elemental iron dose was 4.15mg/kg/day. Median duration of therapy 50 days.
  • Female patients had significantly lower ferritin and haemoglobin compared to male patients
  • Multivariate analysis for predictors of intraoperative RBC transfusion was performed. Strong associations were found with:
    • Non-idiopathic aetiology OR 4.179
    • Cobb angle (OR 1.025)
    • Number of vertebrae fused OR 1.169


  • In addition, patients with Hb >140 g/L or Hb 130-140 g/L were less likely to bleed than those with Hb 120-130 g/L or <120 g/L
  • There was no association seen between the dose or the duration of iron and the need for RBC transfusion.


The study describes a Canadian population group similar to the Australasian centres carrying out spine surgery.

The majority of the patient population was female with reduced Hb & ferritin compared to males. This should be consistent with Australasian centres given the prevalence of idiopathic scoliosis in adolescent females.

In this study it was shown that a preoperative Hb >130 g/L reduces perioperative RBC transfusion.

There may be benefit in introducing supplemental iron for these patients in an attempt to achieve a preoperative Hb of >130 g/L.

The optimal iron supplementation strategy was unclear.


Reviewed by Dr. J. Houghton