Ropivacaine spinal anesthesia in neonates: a dose range finding study.

Area of Science:

• Pediatric Anesthesiology
• Pharmacodynamics
• Regional Anesthesia

Background:

• Determining the minimum local anesthetic dose (MLAD) for spinal anesthesia in neonates is crucial for safe and effective pain management.
• Understanding the dose-response curve, including the ED95, is essential for optimizing anesthetic protocols in this vulnerable population.

Purpose of the Study:

• To determine the median effective local anesthetic dose (MLAD) of ropivacaine for spinal anesthesia in neonates.
• To establish the dose-response curve, including the ED95, for ropivacaine spinal anesthesia.
• To describe the duration of motor block following ropivacaine spinal anesthesia in neonates.

Main Methods:

• A sequential up-down allocation method was used to determine the MLAD of ropivacaine in 50 neonates undergoing inguinal hernia repair.
• An expanded dose-ranging study followed, with dose escalation to target the ED50-95 range.
• Probit and logit analyses were employed to determine the ED50 and ED95, and to compare results with the Dixon-Massey method.

Main Results:

• The MLAD (95% CI) for ropivacaine spinal anesthesia was determined to be 0.51 (0.38-0.64) mg/kg.
• Logistic regression confirmed the MLAD, with an ED50 of 0.50 (0.39-0.63) mg/kg and an estimated ED95 of 1.08 (0.70-1.67) mg/kg.
• The mean duration of motor blockade was 60.0 minutes (51.5-68.5 min), which exceeded surgical duration in successful cases.

Conclusions:

• Ropivacaine is an effective agent for spinal anesthesia in neonates, with a recommended dose of 1.08 mg/kg.
• The duration of motor block with ropivacaine in neonates is shorter and more variable compared to equivalent agents.