Factors Associated With Suboptimal Interscalene Brachial Plexus Block for Arthroscopy

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Study participants were premedicated with 7.5 mg oral midazolam in the morning prior to their surgery.
Study participants were premedicated with 7.5 mg oral midazolam in the morning prior to their surgery.

Factors including male gender and high body mass index were found to be independent risk factors for suboptimal interscalene brachial plexus block in patients undergoing elective shoulder arthroscopy, according to a study published in Anaesthesiology Intensive Therapy.

A total of 109 patients (American Society of Anesthesiologists grades of I to III) who underwent elective shoulder arthroscopy were randomly selected and enrolled in the observational trial. Study participants were premedicated with 7.5 mg oral midazolam in the morning prior to their surgery and were randomly assigned to receive an ultrasound-guided interscalene brachial plexus block (n=37; 20 mL of 0.5% ropivacaine), peripheral nerve stimulation-confirmation interscalene brachial plexus block (n=34), or ultrasound-guided, peripheral nerve stimulation-confirmed interscalene brachial plexus block (dual guidance; n=38).

The mean time of sensory and motor block terminations was comparable in the 3 groups. Patients who required general anesthesia after the block had a 1.3-point higher body mass index score vs patients with complete ultrasound-guided interscalene brachial plexus block (26.84±3.7 kg/m2 vs 25.54±3.43 kg/m2, respectively; P =.0483). A negative correlation was observed between patients' age and the requirement to convert to general anesthesia (P =.0733). Men vs women were more likely to require conversion to general anesthesia (80% vs 20%, respectively) and less likely to experience a failed regional block (37.76% vs 62.24%, respectively; P =.0463).

The small cohort, observational nature of the study, and lack of a placebo group represent the main limitations of the study.

“[The use of ultrasound] visualization during interscalene brachial plexus block performance leads to the disappearance of the [observed] correlations, which makes [ultrasound] visualization especially useful in patients with uncommon anthropometry.”

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Reference

Stasiowski MJ, Chabierska E, Marciniak R, et al. Risk factors of occurrence of failed interscalene brachial plexus blocks for shoulder arthroscopy using 20 mL 0,5% ropivacaine: a randomised trial [published online September 17, 2018]. Anaesthesiol Intensive Ther. doi: 10.5603/AIT.a2018.0030

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