Original scientific paper

Comparison of minimum effective volume of local anesthetic for ultrasound guided supraclavicular block (MEAV95) in elderly and middle aged patients

JADRANKA PAVIČIĆ ŠARIĆ orcid.org/0000-0003-4124-8056 ; Department of Anesthesiology and Intensive Care University Hospital Merkur, Zajčeva 19, 10000 Zagreb, Croatia
VINKO VIDJAK ; Department of Diagnostic and Interventional Radiology University Hospital Merkur, Zagreb, Croatia
JELENA ZENKO ; Department of Anesthesiology and Intensive Care University Hospital Merkur, Zagreb, Croatia
MATEA BOGDANOVIĆ DVORŠČAK ; Department of Anesthesiology and Intensive Care University Hospital Merkur, Zagreb, Croatia
VANJA VONČINA ; Department of Anesthesiology and Intensive Care University Hospital Merkur, Zagreb, Croatia
NATAŠA PAKLAR ; Department of Anesthesiology and Intensive Care University Hospital Merkur, Zagreb, Croatia

Abstract

Backgrund and purpose: The aim of this study was to determine the
minimum effective volume of local anesthetic (LA) required to produce an
efficient supraclavicular block in 95% of patients (MEAV95) using an ultrasound (US)-guided technique in an elderly (>65 y) and a middle aged
group (<45 y) of patients. Furthermore, we aimed to calculate potency ratio of LA between the groups. We assumed a reduced MEAV95 in elderly group.

Matherials and Methods: Fourty-four patients (N=22 per group) undergoing upper limb surgery received a US-guided supraclavicular block.
The study method is a previously validated step-up/step-down sequential
model where the volume of LA for each following patient is determined
according to the outcome of the previous block. The starting volume was 30 mL; in the case of block failure, the volume was increased by 5 ml. After successful block, the volume was reduced by 5 mL. MEAV95 was calculated using probit transformation and logistic regression. Potency ratio of LA is calculated using Fieller’s method.

Results and Conclusions: The calculated minimum effective anesthetic
volume in 95% of patients was 16.49 mL (95% CI, 12.23–20.75
mL) in elderly and 44.52 mL (95% CI, 19.05–69.99 mL) in middle aged
group (95% CI, 0.7–55.3 mL, P=0.044). A potency ratio of LA between
middle aged and elderly is 2.69 (95% CI 2.13 to 3.44). The minimum
volume requirement for effective US-guided supraclavicular block in 95%
of elderly patients was significantly reduced. A potency ratio of 2.69 indicates almost three times stronger LA potency in the elderly.

Keywords

Hrčak ID:

142924

URI

https://hrcak.srce.hr/142924

Publication date:

10.6.2015.

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