A Comparative Study of Three Concentrations of Intravenous Nalbuphine Combined with Hydromorphone for Post-Cesarean Delivery Analgesia

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A Comparative Study of Three Concentrations of Intravenous Nalbuphine Combined with Hydromorphone for Post-Cesarean Delivery Analgesia

Cesarean section (CS) is associated with significant postoperative pain, primarily categorized into somatic pain (incisional pain) and visceral pain (uterine cramping pain). Effective pain management is critical to reduce complications such as delayed breastfeeding, postpartum depression, and immune dysfunction. Hydromorphone, a potent μ-opioid receptor agonist, is widely used for somatic pain but lacks efficacy against visceral pain. Nalbuphine, a κ-opioid receptor agonist and μ-opioid receptor antagonist, offers complementary benefits by targeting visceral pain while mitigating μ-opioid-related side effects. This study aimed to identify the optimal concentration of nalbuphine combined with a fixed hydromorphone dose (0.05 mg/mL) for post-CS intravenous patient-controlled analgesia (PCA).

Study Design and Methodology

A prospective, randomized, double-blind trial enrolled 114 healthy parturients undergoing elective CS under epidural anesthesia. Participants were stratified into three groups (38 per group) via Excel-generated randomization:

  • Group LN: Hydromorphone 0.05 mg/mL + nalbuphine 0.5 mg/mL
  • Group MN: Hydromorphone 0.05 mg/mL + nalbuphine 0.7 mg/mL
  • Group HN: Hydromorphone 0.05 mg/mL + nalbuphine 0.9 mg/mL

PCA pumps were programmed with a 2 mL/h basal infusion, 2 mL bolus doses, a 10-minute lockout interval, and a 14 mL/hour maximum limit. Postoperative assessments included visual analog scale (VAS) scores for incisional pain (at rest and during movement) and uterine cramping pain (at rest, after breastfeeding, and during oxytocin infusion). Secondary outcomes included PCA demand/delivery metrics, cumulative hydromorphone-nalbuphine consumption, Ramsay Sedation Scale (RSS) scores, side effects (nausea, vomiting, urinary retention), and patient satisfaction.

Key Findings

Analgesic Efficacy

  1. Incisional Pain Management:
    All groups demonstrated comparable VAS scores for incisional pain at rest (VAS-I-R) and during mobilization (VAS-I-M) across all time points (4–48 hours post-CS). Hydromorphone 0.05 mg/mL provided consistent somatic analgesia regardless of nalbuphine concentration.

  2. Uterine Cramping Pain:

    • Early Postoperative Phase (0–12 hours):
      VAS scores for uterine cramping pain at rest (VAS-U-R) and after breastfeeding (VAS-U-F) were significantly lower in Group HN (nalbuphine 0.9 mg/mL) compared to Group LN (nalbuphine 0.5 mg/mL) (e.g., at 4 hours: VAS-U-R 1.9 vs. 3.0; VAS-U-F 2.9 vs. 3.4; P < 0.01). Group MN (nalbuphine 0.7 mg/mL) showed intermediate efficacy, with no significant difference from Group HN.
    • Oxytocin-Induced Pain:
      During oxytocin infusions (postpartum days 1–3), Group LN reported higher VAS-U-O scores than MN and HN (e.g., day 1: 4.8 vs. 3.5 vs. 3.3; P < 0.01).

  3. PCA Utilization:

    • Group LN required more PCA bolus demands (21 ± 16) and higher cumulative doses (129 ± 25 mL) over 48 hours compared to MN (15 ± 10 demands; 120 ± 16 mL; P < 0.05) and HN (13 ± 9 demands; 117 ± 13 mL; P < 0.01).
    • The PCA delivery/demand ratio was lowest in LN (0.75 ± 0.11) vs. MN (0.81 ± 0.22) and HN (0.83 ± 0.11; P < 0.01), indicating poorer analgesia in the low-concentration group.

Sedation and Side Effects

  • Ramsay Sedation Scores:
    Group HN exhibited higher sedation at 8 and 12 hours post-CS (RSS 2.56 ± 0.50 and 2.42 ± 0.50) compared to LN (2.08 ± 0.27 and 2.08 ± 0.27; P < 0.01) and MN (2.18 ± 0.39 and 2.13 ± 0.34; P < 0.01).
  • Adverse Events:
    • Urinary retention occurred more frequently in HN (11.1%) vs. LN (5.3%) and MN (5.3%; P < 0.05).
    • Time to first flatus was prolonged in HN (48 ± 6 hours) vs. LN (43 ± 8 hours) and MN (40 ± 14 hours; P < 0.01).
    • Vomiting rates were similar across groups (2.6–5.6%; P = 0.335).

Patient Satisfaction

Satisfaction scores were highest in Group MN (4.6 ± 0.7) compared to LN (3.9 ± 0.7; P < 0.001) and HN (4.4 ± 0.7; P < 0.01), reflecting optimal balance between analgesia and side effects.

Clinical Implications

The study highlights that combining hydromorphone 0.05 mg/mL with nalbuphine 0.7 mg/mL (Group MN) achieves effective dual analgesia for incisional and uterine cramping pain while minimizing sedation and urinary complications. Higher nalbuphine concentrations (0.9 mg/mL) improve visceral pain control but increase sedation and gastrointestinal side effects, reducing maternal comfort. Conversely, lower concentrations (0.5 mg/mL) inadequately address uterine cramping, necessitating higher opioid consumption.

Limitations and Future Directions

The study did not evaluate prolactin levels or lactation initiation, which are critical for postpartum recovery. Larger trials are needed to confirm these findings and explore interactions between nalbuphine and breastfeeding outcomes. Additionally, individualized dosing based on pain severity and patient-specific factors warrants investigation.

Conclusion

For post-CS intravenous PCA, hydromorphone 0.05 mg/mL combined with nalbuphine 0.7 mg/mL represents the optimal regimen, balancing analgesia, patient satisfaction, and tolerability. This approach addresses the dual nature of post-CS pain while aligning with clinical safety priorities.

doi.org/10.1097/CM9.0000000000000678

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