Intraperitoneal local anesthetics have predominant local analgesic effect: a randomized, double-blind study

Area of Science:

• Anesthesiology
• Pharmacology
• Surgical Pain Management

Background:

• The mechanism of analgesia from intraperitoneal local anesthetics (IP LAs) is debated, with unclear local versus central effects.
• This study investigated whether IP LAs are superior to continuous intravenous (IV) infusion for postoperative pain management.

Purpose of the Study:

• To test the hypothesis that intraperitoneal local anesthetic administration is superior to continuous IV infusion for pain management following abdominal hysterectomy.
• To compare postoperative morphine consumption, pain intensity, recovery parameters, and lidocaine concentrations between different administration routes.

Main Methods:

• A double-blind, randomized clinical trial involving 60 patients undergoing abdominal hysterectomy.
• Patients were assigned to three groups: continuous IV lidocaine with intermittent IP saline, intermittent IP lidocaine with continuous IV saline, or placebo (saline for both routes).
• Primary outcome was morphine consumption from 0 to 24 hours post-surgery; secondary outcomes included pain intensity, recovery metrics, and plasma lidocaine levels.

Main Results:

• Group IP (intraperitoneal lidocaine) showed significantly lower morphine consumption (mean difference -22.6 mg) compared to group IV (IV lidocaine) (P < 0.01).
• No significant difference in morphine consumption was observed between group IV and the placebo group.
• Plasma lidocaine concentrations were lower in group IP than group IV, with no signs of systemic toxicity. Pain intensity and recovery parameters were similar across groups.

Conclusions:

• Lower supplemental morphine requirements in the IP group suggest local anesthetics exert predominant effects via local intraperitoneal receptors or anti-inflammatory actions.
• Findings indicate that the analgesic effects of intraperitoneal local anesthetics are not solely mediated by central mechanisms.
• The study supports the efficacy of intraperitoneal administration for enhanced pain control and potentially reduced systemic drug exposure.