European Journal of Anaesthesiology



Original Article

Increasing the injection volume by dilution improves the onset of motor blockade, but not sensory blockade of ropivacaine for brachial plexus block


H. Krenn a1c1, E. Deusch a1a2, B. Balogh a3a4, H. Jellinek a1, W. Oczenski a1, E. Plainer-Zöchling a1 and R. D. Fitzgerald a1a5
a1 Department of Anaesthesia and Critical Care, City Hospital, Lainz, Vienna, Austria
a2 Department of Anaesthesia and Critical Care, General Hospital, Vienna, Austria
a3 Ludwig Boltzmann Institute for Quality Assurance in Plastic and Reconstructive Surgery, Innsbruck, Austria
a4 Department of Plastic and Reconstructive Surgery, City Hospital, Lainz, Vienna, Austria
a5 Ludwig Boltzmann Institute for Economy in Anaesthesia and Critical Care, City Hospital, Lainz, Vienna, Austria

Article author query
krenn h   [PubMed][Google Scholar] 
deusch e   [PubMed][Google Scholar] 
balogh b   [PubMed][Google Scholar] 
jellinek h   [PubMed][Google Scholar] 
oczenski w   [PubMed][Google Scholar] 
plainer-zochling e   [PubMed][Google Scholar] 
fitzgerald rd   [PubMed][Google Scholar] 

Summary

Background and objective: Ropivacaine used for axillary plexus block provides effective motor and sensory blockade. Varying clinical dosage recommendations exist. Increasing the dosage by increasing the concentration showed no improvement in onset. We compared the behaviour of a constant dose of ropivacaine 150 mg diluted in a 30, 40 or 60 mL injection volume for axillary (brachial) plexus block.

Methods: A prospective, randomized, observer-blinded study on patients undergoing elective hand surgery was conducted in a community hospital. Three groups of patients with a constant dose of ropivacaine 150 mg, diluted in 30, 40 or 60 mL NaCl 0.9%, for axillary plexus blockade were compared for onset times of motor and sensory block onset by assessing muscle strength, two-point discrimination and constant-touch sensation.

Results: Increasing the injection volume of ropivacaine 150 mg to 60 mL led to a faster onset of motor block, but not of sensory block, in axillary plexus block, compared with 30 or 40 mL volumes of injection.

Conclusions: The data show that the onset of motor, but not of sensory block, is accelerated by increasing the injection volume to 60 mL using ropivacaine 150 mg for axillary plexus block. This may be useful for a more rapid determination of whether the brachial plexus block is effective. However, when performing surgery in the area of the block, sensory block onset seems more important.

(Accepted January 2002)


Key Words: ANAESTHESIA CONDUCTION, anaesthesia, local; SPINAL NERVES, brachial plexus; ANAESTHETICS, LOCAL, ropivacaine.

Correspondence:
c1 Correspondence to: Herbert Krenn, Department of Anaesthesia and Critical Care, City Hospital, Lainz, Wolkersbergenstrasse 1, A-1130 Vienna, Austria. E-mail: herbert.krenn@chello.at; Tel: +43 1 80110 2701; Fax: +43 1 80110 2696