Brief Title: Intranasal Dexmedetomidine for Prevention of Intrapartum Fever This study aims to evaluate the effect of intranasal dexmedetomidine (Dex) administered before neuraxial labor analgesia on the incidence of intrapartum fever in women undergoing vaginal delivery.

This prospective, randomized, double-blind, placebo-controlled trial will enroll 446 parturients scheduled for vaginal delivery with neuraxial labor analgesia at Chengdu Jinjiang Maternal and Child Health Hospital from 2026 to 2027. Participants will be randomly assigned in a 1:1 ratio to receive either intranasal Dex (50 μg) or an equal volume of normal saline before the initiation of labor analgesia.

Primary Outcome Measure:

Incidence of intrapartum fever (temperature ≥ 38.0℃) from initiation of labor analgesia to 2 hours postpartum

Secondary Outcome Measures:

Temperature-related outcomes: Incidence of fever at thresholds of ≥ 37.5℃ and ≥ 38.5℃; hourly temperature trends assessed by continuous wireless axillary monitoring Analgesic effect: NRS pain scores before labor analgesia and at 30 minutes, 1 hour, and 3 hours after analgesia Sedative effect: Ramsay Sedation Scale scores at the same time points Maternal safety: Incidence of bradycardia (heart rate < 60 bpm), hypotension (systolic blood pressure < 90 mmHg or < 20% of baseline), nausea, vomiting, oversedation (Ramsay ≥ 4), and respiratory depression (SpO₂ < 90%) Labor characteristics: Duration of first, second, and third stages of labor, total labor duration, and duration of labor analgesia Delivery outcomes: Mode of delivery (spontaneous vaginal delivery or cesarean section) and total consumption of local anesthetics Neonatal outcomes: Apgar scores at 1, 5, and 10 minutes, and NICU admission rate We hypothesize that intranasal Dex administered before labor analgesia will significantly reduce the incidence of intrapartum fever compared to placebo. This study is expected to provide a novel, non-invasive, and effective strategy for preventing epidural-related maternal fever, thereby improving maternal safety and perinatal outcomes in women undergoing vaginal delivery.

Background: Labor analgesia-related intrapartum fever (LRIF), defined as maternal temperature ≥ 38.0°C following labor analgesia, occurs in 15-25% of parturients and is associated with adverse maternal and neonatal outcomes. Dexmedetomidine (Dex) possesses anti-inflammatory properties, and intranasal administration offers rapid onset, high bioavailability, and non-invasiveness. However, its effect on LRIF has not been evaluated in high-quality prospective studies.

Study Design: This is a prospective, randomized, double-blind, placebo-controlled, single-center trial conducted at Chengdu Jinjiang Maternal and Child Health Hospital (2026-2027).

Intervention: Participants are randomized 1:1 to receive intranasal dexmedetomidine (50 μg, 25 μg per nostril) or intranasal normal saline (equal volume) immediately before labor analgesia. Labor analgesia follows a standardized combined spinal-epidural protocol with patient-controlled epidural analgesia.

Randomization and Blinding: A computer-generated random sequence with block size of 4 is used. Allocation is concealed in sequentially numbered, opaque, sealed envelopes. Double-blinding is implemented: participants, outcome assessors, data managers, and statisticians are blinded to group allocation. The attending anesthesiologist is unblinded but does not participate in any follow-up or outcome assessment.

Data Collection: Temperature is monitored continuously using wireless axillary sensors from analgesia initiation to 2 hours postpartum, ensuring capture of hourly temperature trends and fever events. Pain scores (NRS) and sedation levels (Ramsay Sedation Scale) are assessed at predefined time points: before analgesia, and at 30 min, 1 h, and 3 h after analgesia initiation. Data are extracted from electronic health records and case report forms, with double data entry and source data verification for primary outcome events.

Statistical Analysis: The primary analysis follows the modified intention-to-treat principle. The primary outcome (incidence of LRIF) will be analyzed using chi-square test, with risk ratio and 95% CI reported. Continuous variables will be compared using t-tests or rank-sum tests as appropriate. Logistic regression will be performed to adjust for potential confounders. A two-sided P-value < 0.05 is considered statistically significant.

Ethics: The study has been approved by the Ethics Committee of Chengdu Jinjiang Maternal and Child Health Hospital (Approval No. 202509). Written informed consent will be obtained from all participants.

Inclusion Criteria:

• ASA physical status II or III
• Age ≥ 18 years
• Singleton pregnancy, cephalic presentation
• No contraindications to neuraxial anesthesia and voluntarily requesting labor analgesia

Exclusion Criteria:

• Maternal temperature ≥ 37.3°C before labor analgesia
• Allergy to α2-adrenergic receptor agonists
• Severe pregnancy complications or systemic diseases
• Use of analgesics, nonsteroidal anti-inflammatory drugs, or other medications that may affect body temperature within one week prior to enrollment
• Heart rate < 60 bpm or systolic blood pressure < 90 mmHg before labor analgesia
• Severe rhinitis or nasal deformity
• Premature rupture of membranes

Participants, outcome assessors, data managers, and statisticians are blinded to group allocation. The attending anesthesiologist is unblinded but does not participate in any follow-up or outcome assessment.