Pectoral nerves I block is associated with a significant motor blockade with no dermatomal sensory changes: a prospective volunteer randomized-controlled double-blind study

• Published in: Canadian journal of anesthesia Vol. 65; no. 7; pp. 806 - 812
• Main Authors: Desroches, Jean, Belliveau, Marc, Bilodeau, Carole, Landry, Michel, Roy, Maxim, Beaulieu, Pierre
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-07-2018; Springer Nature B.V
• Subjects: Anesthesiology; Breast cancer; Cardiology; Critical Care Medicine; Double-blind studies; Hypotheses; Intensive; Medicine; Medicine & Public Health; Pain Medicine; Pediatrics; Pneumology/Respiratory System; Reports of Original Investigations; Studies; Surgery
• ISSN: 0832-610X; 1496-8975
• DOI: 10.1007/s12630-018-1122-2

Purpose
The pectoral nerves
(
PECS) I block, first described in 2011 for surgery involving the pectoralis muscle, has principally been used for breast cancer surgery. No formal evaluation of its differential motor- and sensory-blocking abilities has been reported. We hypothesize that the PECS I block will produce a motor block of the pectoralis muscles with diminished upper limb adduction strength as measured with a handheld dynamometer.
Methods
We conducted a PECS I block in a randomized placebo-controlled trial in six healthy subjects who received 0.4 mL·kg
−1
of 0.9% saline (placebo) on one side and bupivacaine (0.25% with 1:400 000 epinephrine) on the other. We measured both upper limb adduction strength with a dynamometer and sensory skin levels over the thorax.
Results
The mean (standard deviation [SD]) adductor strength evaluated before the block was 119.4 (20.7) Newtons (N). After the PECS I block with bupivacaine, the mean (SD) strength of 54.2 (16.3) N was compared with 116.0 (30.4) N in the placebo group (difference in means 61.8 N; 95% confidence interval [CI], 27.8 to 95.8 N;
P
 = 0.005), showing a 54.6% (95% CI, 43.6 to 65.6%) reduction in adductor strength. There was no difference in dermatomal skin sensory testing between the placebo and bupivacaine sides.
Conclusions
This study shows that a PECS I block produces motor blockade as shown by reduced upper limb adductor strength without any overlying dermatomal sensory loss.
Trial registration
www.clinicaltrials.gov
(NCT03040167) 2 February 2017.