Korean J Anesthesiol.  2012 May;62(5):468-473. 10.4097/kjae.2012.62.5.468.

At therapeutic concentration bupivacaine causes neuromuscular blockade and enhances rocuronium-induced blockade

• Lee JH
• Lee SI
• Lee SC
• Choi SR
• Rhee WJ

• KMID: 2243827
• DOI: http://doi.org/10.4097/kjae.2012.62.5.468

Abstract

BACKGROUND
Partially paralyzed patients may be placed in the risk of pharyngeal dysfunction. Bupivacaine acts as acetylcholine receptor ion channel blocker and may synergistically interact with rocuronium to augment NM blockade. Thus, this study aims to elucidate whether or not, at a therapeutic concentration, bupivacaine by itself may cause NM blockade and reduce an effective concentration of rocuronium.
METHODS
Twenty-two left phrenic nerve-hemidiaphragms (Male SD rats, 150-250 g) were hung in Krebs solution. Three consecutive ST, 0.1 Hz and one TT, 50 Hz for 1.9 s were obtained before drug application and at each new drug concentration. A concentration of bupivacaine in Krebs solution (n = 5) was cumulatively increased by way of 0.01, 0.1, 1, (1, 2, 3, 4, 5, 6, 7) x 10 microM. In a Krebs solution, pre-treated with bupivacaine 0 (n = 5), 0.1 (n = 5), 1.0 (n = 5), 10 (n = 2) microM, and then concentrations of rocuronium were cumulatively increased by way of 1, 3, 5, 7, 9, 12, 14, 16, 18, 20 microM. EC for each experiment were determined by a probit. The EC50's of rocuronium were compared using a Student's t-test with Bonferroni's correction. Differences were considered significant when P < 0.05.
RESULTS
The potency of bupivacaine for normalized TF was 11.4 (+/- 1.1) microM. Below 30 microM of bupivacaine, the single twitch potentiation sustained despite the development of tetanic fade and partial inhibition of PTT. Bupivacaine significantly facilitated the NM blockade induced by rocuronium.
CONCLUSIONS
Clinicians should be aware that bupivacaine by itself at its therapeutic concentration inhibit NM conduction and enhances rocuronium-induced muscle relaxation.

Keyword

Bupivacaine; Neuromuscular blockade; Rocuronium

MeSH Terms

Acetylcholine
Androstanols
Animals
Bupivacaine
Humans
Ion Channels
Isotonic Solutions
Muscle Relaxation
Neuromuscular Blockade
Rats
Refractory Period, Electrophysiological
Acetylcholine
Androstanols
Bupivacaine
Ion Channels
Isotonic Solutions