Regional Blood Flow Spectral Parameters as Predictors of Epidural-Related Maternal Fever: A Prospective Observational Study

Background: Epidural-related maternal fever (ERMF) is a common phenomenon that appears to be unique to laboring women and presents diagnostic and therapeutic dilemmas for anesthesiologists. It is crucial to identify and predict the occurrence of ERMF at an early stage to improve the outcomes for mothers and infants. This study evaluated the degree of sympathetic blockade induced by epidural labor analgesia (ELA) by quantifying blood flow spectral parameters using Pulsed-wave Doppler (PWD). The aim was to determine the predictive value of these parameters for the onset of ERMF. Methods: A total of 103 women who had vaginal deliveries with ELA were recruited into the study. PWD ultrasound was used to measure peak systolic velocity (PSV, cm/s) and end-diastolic velocity (EDV, cm/s) in the anterior and posterior tibial arteries. Measurements were taken 1 minute before induction of analgesia and at 5-minute intervals for the subsequent 30 minutes. The change of PSV (ΔPSV) and EDV (ΔEDV) at 30 minutes relative to baseline after induction of analgesia was calculated. Participants were categorized into two groups based on their body temperature during labor and delivery: febrile and afebrile. Generalized estimating equations were used to assess differences both between and within groups across multiple time points. The correlation between two variables was analyzed using Spearman's rank correlation coefficient. Receiver operating characteristic (ROC) curves were plotted to ascertain the cut-off values of lower extremity arterial ultrasound flow spectral parameters for predicting ERMF. Results: Of the 103 study participants, 73 were ultimately included for analysis. Thirteen participants (17.8%) in the study developed ERMF. PSV was significantly higher in the febrile group than the non-febrile group at 10 min after ELA (p < 0.05). In contrast, EDV showed a significant difference between the two groups at 15 min after ELA (p < 0.01). Based on linear correlation analysis, there was a positive correlation between PSV and EDV at 30 minutes after analgesia induction and the peak labor temperature (p < 0.05). ROC curve analysis identified a cut-off value of 43.35 and an area under the curve (AUC) of 0.701 for ΔPSV in the anterior tibial artery region (95% confidence interval (CI) 0.525 to 0.878, p = 0.025) and a cut-off value of 29.94 and an AUC of 0.733 for ΔEDV (95% CI 0.590 to 0.877, p = 0.001). The cut-off value for ΔPSV in the region of the posterior tibial artery was 39.96 with an AUC of 0.687 (95% CI 0.514 to 0.860, p = 0.034), and the cut-off value for ΔEDV was 33.10 with an AUC of 0.713 (95% CI 0.558 to 0.869, p = 0.007). Conclusions: Regional blood flow spectral parameters after epidural analgesia induction can predict the occurrence of ERMF by indirectly reflecting the degree of sympathetic activity inhibition. Specifically, the amount of change in peak systolic velocity and end-diastolic velocity relative to baseline parameters 30 min after ELA induction was the most predictive. Clinical Trial Registration: The study has been registered in the Chinese Clinical Trial Registry https://www.chictr.org.cn/ (reference number: ChiCTR2400080507, 31/01/2024).