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

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Amy L. McIntosh
Chris McLeod


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.

Article Details

How to Cite
McIntosh, A. L., & McLeod, C. (2023). Accuracy of Non-Invasive Hemoglobin (nHgb) Monitoring in an AIS Population: Quality, Safety and Value (QSVI). Journal of the Pediatric Orthopaedic Society of North America, 5(2).
Author Biography

Amy L. McIntosh

Amy McIntosh is a Professor of Orthopedic Surgery and the medical director of patient safety at Texas Scottish Rite Hospital (TSRH) for Children in Dallas, TX. She has been married to her husband, Rich, for 25 years. She has 2 children Quincy (boy: 13 years) and Campbell (girl: 10 years).

She was born and raised in the Upper Peninsula of Michigan. She graduated from Gladstone High School in 1992. She received her Bachelor of Science degree (Summa Cum Laude) in Sports Medicine from Central Michigan University in 1996. She then matriculated to Michigan State University College of Human Medicine and graduated with honors and AOA induction in 2001.

She completed her orthopedic surgery residency at the Mayo Clinic in 2006, followed by her fellowship in pediatric orthopedic surgery and scoliosis at TSRH in 2007.

She then returned to the Mayo Clinic for 7 years as a staff orthopedic surgeon. In 2014, she transitioned her practice back to TSRH, where she currently remains in practice.


Awards include: 

2001 Medical Student of the Year - MSU-KCMS

2005 OREF Zimmer Resident Leadership Forum - American Orthopaedic Association

2013 Mayo Clinic Coventry Award Winning Paper

2013 AAP Section on Orthopedics: Young Investigators Award: Clinical Science

2013 Mayo Clinic Continuing Medical Education Outstanding Course Director of the Year

2014 Minnesota Orthopedic Society: Best Clinical Research Award

2014 Mid-America Orthopaedic Association E.W. Johnson, Jr. Award

2015 POSNA/APPOS Traveling Fellowship

2016 POSNA/ Peter Armstrong Best QVSI Award

2017 POSNA / Medtronic Spine Research Grant

2018 Texas Hospital Association Bill Aston Quality Improvement Award

2019 Women Who STEAM Award

2020 SRS OREF Spine Grant

2021 POSNA QVSI Grant