Casati et al. Anesth 1999 90(4):1047-52

Reviewed by: R. Prasad, MD

Conclusions:
Ropivacaine 0.75% was best (vs. 0.5%, 1%, and mepiv 2%) - onset similar to mepiv, with longer duration of analgesia.

Comments:

• Blocks seem overkill (complete loss of LE fnct) for hallux valgus repair
• Block technique different than UNC, where most of us do single injections/block
• Didn't show any differences btwn ropiv 0.75% and 1% ... why not recommend 1%? Theoretical concern re: neurotoxicity?
• Interesting that drug amount (vs. concentration) more important, at least for sensory duration.

Block technique

• Nerve stimulator, to <0.5 mA.
• FNB
• anterior approach, lateral to artery
• looked for vastus medialis, intermedius, and lateralis twitches
• 30mg rop or 60mg mepiv at each twitch
• SNB
• Labat approach
• looked for foot flexion, foot dorsiflexion, biceps femoris
• 45mg rop or 100mg mepiv at each twitch
• If at least 2 twitches could not be elicited for each block, pt removed from study

Power
Study was designed for 90% power to detect a 2hr difference in POP relief between 0.75% and other rop concentrations.
Needed 55-84 pts per group

Results:

• 88% hallux valgus repairs, 4% ankle, 8% toe surgeries.
• 5 anxious pts who needed sedation during block were excluded.
• For all pts, at least 2 twitches/block found. No failed blocks.
• Block...
• Adequacy, tourniquet pain, pt satisfaction - equivalent all groups.
• Onset (sensory, motor) - all other groups faster than ropiv 0.5%; no other signif differences.
• Resolution. Motor - ropiv (all []s equal) lasted longer than mepiv. Sensory (analgesia - first pain med reqd) - 1% & 0.75% lasted about 2hrs longer than 0.5%.
• POD #1, dysesthesias reported 5-8% ropiv groups vs. 1% mepiv. All resolved completely by 1wk after discharge.