The Effect of Ultrasound Real-time Guidance Technique on the Effectiveness and Safety of Labor Analgesia

The primary outcome is a binary composite endpoint: "satisfactory" (Grades I-II) versus "unsatisfactory" (Grades III-IV). Grading followed a hierarchical rule (IV > III > II > I): if more than one grade applied, the highest (worst) was assigned.

Grade I (best): vaginal delivery (spontaneous or instrumental) with analgesic onset ≤ 20 min, mean VAS ≤ 40 mm, no catheter or protocol adjustment, and modified Bromage score < 2.

Grade II (good): vaginal delivery not meeting Grade I criteria but with onset ≤ 30 min, mean VAS ≤ 60 mm, and no Grade IV-listed complications.

Grade III (poor): cesarean delivery, or onset > 30 min, or mean VAS > 60 mm.

Grade IV (worst): serious analgesia-related complications (unintended dural puncture with the epidural needle, Bromage score ≥ 2, persistent neurological injury, local anesthetic toxicity, or severe hypotension requiring intervention).

Time from initial drug administration to the first documented Visual Analogue Scale (VAS) score ≤ 30 mm. VAS scale: 0 = no pain, 100 mm = worst possible pain.

Time-weighted mean pain VAS score from analgesia start to delivery, derived from area under the curve (AUC) calculation. VAS scale: 0 = no pain, 100 mm = worst possible pain.

Number of PCA bolus demands during labor analgesia.

Per-minute local anesthetic consumption during labor analgesia.

Sensory blockade level assessed by loss of cold sensation using an alcohol swab, recorded at 30 min after the loading dose and at the highest level.

Defined as a ≥ 2-dermatome difference in sensory blockade level between the left and right sides.

S2 sensory blockade categorized as bilateral, unilateral, or none.

Physician interventions including analgesic regimen adjustments, epidural catheter repositioning, and re-puncture.

Motor blockade assessed by the modified Bromage score: 0 = full flexion of knees and ankles, 1 = partial flexion of knees with full flexion of ankles, 2 = inability to flex knees with partial flexion of ankles, 3 = inability to flex knees and ankles.

Incidence of lower limb numbness (defined as loss of cold sensation by alcohol swab test), urinary retention (defined as inability to void spontaneously within 8 h postpartum requiring catheterization), nausea and vomiting, and postpartum headache.

Rate of cesarean delivery and indications for cesarean delivery (non-reassuring fetal heart rate, arrest of descent, maternal indications, other).

Time-weighted mean uterine contraction frequency, derived from area under the curve (AUC) calculation from analgesia to delivery. Unit of measure: contractions per 10 minutes

Time-weighted mean single uterine contraction duration, derived from area under the curve (AUC) calculation from analgesia to delivery. Unit of measure: seconds.

Defined as a single contraction lasting > 2 min.

Defined as > 5 contractions per 10 min.

Duration of the first, second, third, and total stages of labor.

Maternal body temperature before analgesia and at delivery.

NICHD (National Institute of Child Health and Human Development) Fetal Heart Tracing Classification: Category I (normal), Category II (indeterminate), Category III (abnormal). A higher category indicates a less reassuring fetal status.

Proportion of parturients whose NICHD category worsened from baseline during labor analgesia.

Time-weighted mean fetal heart rate from analgesia to delivery, derived from area under the curve (AUC) calculation.

Types of fetal heart rate decelerations (early, late, variable).

Fetal heart rate variability categorized as absent, minimal, moderate, or marked.

Apgar scores assessed at 1, 5, and 10 minutes after birth. The Apgar score ranges from 0 to 10, with higher scores indicating better condition. The proportion of neonates with Apgar < 7 at 1 minute is also reported.

Post-delivery hs-CRP level in venous blood, adjusted for pre-delivery baseline value using analysis of covariance (ANCOVA). Unit of measure: mg/L.

Post-delivery IL-6 level in venous blood, adjusted for pre-delivery baseline value using analysis of covariance (ANCOVA). Unit of measure: pg/mL.

Post-delivery cortisol level in venous blood, adjusted for pre-delivery baseline value using analysis of covariance (ANCOVA). Unit of measure: nmol/L.