Accuracy of Non-Invasive Hemoglobin (nHgb) Monitoring in an AIS Population Quality, Safety and Value (QSVI)

Abstract

Background: Needle phobia and fear of blood draws is very common in children and adolescents.

Local Problem: Noninvasive hemoglobin (nHgb) monitoring in children was first introduced in the Intensive Care Unit (ICU) setting. However, it has never been utilized in an Adolescent idiopathic Scoliosis surgical patient population.

Specific Aims: The purpose of this project was to identify the correlation between nHgb monitoring and (invasive Hgb (iHgb)) values, obtained from a blood draw. The goal was to determine a nHgb threshold. Post-surgical AIS patients with a nHgb level above the threshold would no longer require a blood draw, thus minimizing resource utilization, blood draw related anxiety, and pain during the postoperative period.

Intervention: nHgb and iHgb values were obtained within 60 minutes of each other at three separate time points (preoperative, in Post-Anesthesia Care Unit (PACU), and POD 1 at 0700).  iHgb and nHgb values were recorded.

Measures and Analysis: The results were retrospectively reviewed and analyzed. Paired t tests were utilized to compare mean (n/i)Hgb values. Pearson correlation coefficients were calculated at all three time points. ROC analysis was performed on the postoperative values to determine a threshold. The threshold became the new trigger for a blood draw post-operatively.

Results: We enrolled 60 consecutive patients undergoing posterior spine fusion/instrumentation (PSFI) for AIS. Average EBL was 415cc, and 189 cc was returned via cell saver. 2/60 (3.3%) patients required an allogenic blood transfusion peri-operatively. There was a moderate positive correlation at all three time points (0.4, 0.59, 0.6) (p= 0.005, <0.001, <0.001). At all three timepoints, the mean nHgb value was 1-2 g/dL higher than the mean iHgb value, and this was statistically significant.

At 0700 on POD1, a patient with a nHgb value of ≥10.8 g/dL had an iHgb value of >9.0 g/dL with 87% sensitivity.

66 additional AIS patients underwent PSFI since implementing the nHgb threshold of 10.8g/dL. Only 10/66 (15%) of those AIS surgical patients had a nHgb <10.8 g/dL requiring a venipuncture during their post-operative recovery. The average post-op serum Hgb (10 patients) was 9.75 g/dL (8.3-12.8) g/dL.

Summary: nHgb monitoring was found to correlated with iHgb in pediatric AIS patients undergoing PSFI. Surgeons could consider screening AIS patients post-operatively with nHgb monitoring and only order iHgb measurement if the nHgb value is <10.8 g/dL. 6 months after instituting this nHgb threshold, 85% (56/66) of our post-surgical AIS patients had NO blood draw following surgery.