Nerve stimulation at 0.15 Hz when compared to 0.1 Hz speeds the onset of action of cisatracurium and rocuronium.
BACKGROUND
Onset time of specific non-depolarizing muscle relaxants (NDMR), as reported in the literature, varies widely. To test the suggestion of a consensus panel (Copenhagen Consensus Conference 1996) that onset time in muscle relaxant studies depends on stimulation frequency, even in the low frequency range, we examined the onset time of cisatracurium and rocuronium by parallel ulnar nerve stimulation in both upper extremities at 0.1 Hz and 0.15 Hz.


METHODS
Thirty patients (ASA class I and II) were included. Onset of action following the administration of 2xED90 of cisatracurium (0.092 mg x kg(-1)) or rocuronium (0.74 mg x kg(-1)) was measured by quantifying the evoked response of the adductor pollicis muscles using mechanomyography. Single twitch stimulations were applied simultaneously to the ulnar nerves of both forearms using a 0.1 Hz and 0.15 Hz stimulation frequency, respectively.


RESULTS
Both relaxants showed a significantly (P<0.01) shorter onset time with 0.15 Hz compared to 0.1 Hz stimulation (cisatracurium: 186+/-50 s vs. 233+/-59 s, rocuronium: 73+/-14 s vs. 99+/-23 s; x+/-SD).


CONCLUSIONS
Onset time of NDMR depends on the stimulation frequency, even in the low frequency range. When comparing onset studies, the reader must also compare the stimulation rates used by the investigators. We recommend the use of 0.1 Hz single twitch nerve stimulation frequency as the standard for studies of onset profile of NDMR.
Eikermann
M
M
Abteilung für Anästhesiologie und Intensivmedizin, Universität GH Essen, Germany.
Peters
J
J
D000293:Adolescent; D000328:Adult; D000732:Androstanols / Q000494:pharmacology*; D001279:Atracurium / Q000031:analogs & derivatives* / Q000494:pharmacology; D004558:Electric Stimulation; D006801:Humans; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D000077123:Rocuronium; D014459:Ulnar Nerve / Q000502:physiology
D000732:Androstanols; D009466:Neuromuscular Blocking Agents; D001279:Atracurium; C101584:cisatracurium; D000077123:Rocuronium