Effect of Integrated Value of Preoperative Hemoglobin Level and Oxygen Saturation on Postoperative Outcomes of Tetralogy of Fallot Repair

Background: Preoperative Hb × SpO2 level compare with age adjusted hemoglobin level can better evaluate anemia of TOF patients. This study aimed to compare postoperative outcomes of TOF repair between patients with high and low integrated value of preoperative hemoglobin and oxygen saturation than age adjusted hemoglobin.

Methods: This comparative cross-sectional study was conducted at the Department of Pediatric Cardiac Surgery of the National Heart Foundation Hospital and Research Institute, for a period from July, 2022 to April, 2024. The study included 101 admitted patients undergoing TOF repair then they were divided into two groups: In group A, 52 patients with Hb × SpO2 ≥ aaHb while in group B 49 patients with Hb x SpO2 ≤ aaHb. Data were collected in separate case-record form and analyzed by SPSS 27.0. The statistical analysis was done with unpaired t-test for parametric quantitative data and Mann Whitney test for non-parametric quantitative data and Chi-square test was used for qualitative data. The ‘p’ value of <0.05 was considered as statistically significant.

Results: In this study, the mean (± SD) age of the patients in group A was 6.12±4.18 years and group B was 4.85±3.55 years. The difference was statistically not significant (p=0.104). In group A male 31% and female 21%, in group B male 35% and female 14%, but the difference was statistically not significant. Mean (±SD) BSA (m2) were 0.72±0.29 vs 0.62±0.25; (p=0.076) in group A and B respectively, but the difference was statistically not significant. Significant differences observed in mean (± SD) preoperative Hb (gm/dl) 17.9 ± 2.98 gm/dl vs 13.2 ± 1.78mg/dl; p < 0.001, mean (± SD) Hb × SpO2 14.52 ± 1.79 vs 10.5 ± 1.42; p < 0.001 and mean (± SD) hematocrit value 43.8 ± 9.72 vs 38.2 ± 6.24; p < 0.001 between group A & B. More Patients in group B exhibited > 20 ionotropic score than in group A with proportion of 10(20.4%) vs 5(9.6%). The mean (± SD) ionotropic score was 11.0±5.2 in group A and 13.9±7.7 in group B;(p=0.028). Besides this, group B patients had longer duration of ionotropic support (3.56±1.11 days vs 4.80±1.97 days; p <0.001), sepsis 4 (7.7%) vs 12(24.49%); p=0.021, longer ventilation time (15.3±20.6 hours vs 37.4±68.0 hours, p=0.027), longer ICU stay (5.79±4.17 days vs 7.98±5.35 days; p= 0.023) and longer hospital stays (8.73±4.82 days vs 10.9±5.75 days; p=0.035) than group A patients. Group A patients had a significantly higher pleural drainage (ml) amount (661.2±849.9 vs 317.6±328.1, p=.009) and amount (ml) of transfusion (829.4±961.5 vs 430.0±384.1; p=0.008) than group B patients.

Conclusion: TOF repair with Hb × SpO2 ≤ aaHb had a poor postoperative outcome in terms of inotrope use, sepsis, mechanical ventilation time, ICU stay and hospital stay. Conversely patients with Hb × SpO2 ≥ aaHb had more vulnerability of post-operative bleeding and transfusion requirement. Preoperative Hb × SpO2 can be potential tools for prediction of postoperative outcomes of TOF repair.

Keywords: Integrated Value, Preoperative Hemoglobin Level, Oxygen Saturation, Tetralogy of Fallot Repair.