Color Doppler to confirm epidural catheter positioning in parturient, would it help?

Labor pain is ranked as one of the most severe type of pain that women experience during their lifetime. Epidural analgesia is the gold standard technique used to decrease labor pain while providing a favorable maternal and fetal safety profile.1The reported incidence reports of failure of epidural analgesia reached between 13% and 32% depending on the definition of failure adopted done by researchers.2,3 In obstetric population a retrospective study where 75% of patients received epidural analgesia. Results showed an overall failure of 12% while in the same study 6.4% of patients witnessed failure after a preceding time of adequate analgesia.4To decrease the rate of failure, different confirmatory methods have been proposed as epidural stimulation tests5,6, injection of contrast dye7, detecting epidural space waveform pressures8 and ultrasonography.9Specific objectives:The primary outcome is to calculate the sensitivity and specificity of using color Doppler with pulsed wave Doppler to accurately detect the position of epidural catheter in BMI < 35 versus BMI > 35 (morbid obese) parturients in labor.Secondary outcome is to detect the percentage of failure of epidural analgesia defined as inadequate analgesia despite adequate dosing at any time during or after initial epidural placement.