[Muscle weakness and tolerance of low doses of rocuronium in healthy awake volunteers breathing spontaneously].
OBJECTIVE
To study muscle weakness caused by low doses of rocuronium and rocuronium intolerance in healthy volunteers, with the general aim of producing brief skeletal-muscle relaxation that would have potential applications in clinical situations.


METHODS
After receiving authorization from the clinical research ethics committee of our hospital, we set out to study the effects on subjective and objective muscle strength of injecting 3 doses of rocuronium (0.1 mg x kg(-1), 0.05 mg x kg(-2), and 0.075 mg x kg(-1)) in healthy volunteers, each dose on a different day. Objective muscle strength was measured using a hand dynamometer. We also recorded the development of expected adverse effects (diplopia, dysarthria, and dysphagia).


RESULTS
Five volunteers (all authors) were studied. In the first subject, the dose of 0.1 mg x kg(-1) of rocuronium was unsatisfactory because it was too strong, causing extreme skeletal-muscle weakness and discomfort due to diplopia, dysarthria, and dysphagia. The dose of 0.05 mg x kg(-1) was well tolerated but caused no subjective feeling of weakness or any effect measurable on dynamometry. These doses were not administered to the other subjects. In the 4 remaining volunteers, the dose of 0.075 mg x kg(-1) caused a brief feeling of muscle weakness that was considered to be acceptable, though the findings were compromised by 2 technically defective baseline dynamometry readings. The volunteers also reported brief, mild discomfort, principally due to dysphagia.


CONCLUSIONS
Doses of 0.075 mg x kg(-1) of rocuronium in healthy awake subjects breathing spontaneously are acceptably tolerated and cause brief muscle weakness that may be of use in situations that require skeletal muscle relaxation at specific moments.
Gerónimo Pardo
M
M
Servicio de Anestesiología, Reanimación y Terapéutica del Dolor, Complejo Hospitalario Universitario de Albacete. sergepu@hotmail.com
Martínez González
E
E
García Blasco
O
O
Losa Palacios
S
S
Gallach Sanchís
D
D
D000328:Adult; D000732:Androstanols / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D004172:Diplopia / Q000139:chemically induced / Q000523:psychology; D004305:Dose-Response Relationship, Drug; D004401:Dysarthria / Q000139:chemically induced / Q000523:psychology; D018737:Hand Strength; D006801:Humans; D008297:Male; D018908:Muscle Weakness / Q000139:chemically induced* / Q000523:psychology; D003473:Neuromuscular Nondepolarizing Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D010342:Patient Acceptance of Health Care; D012119:Respiration; D000077123:Rocuronium; D014851:Wakefulness; D055815:Young Adult
D000732:Androstanols; D003473:Neuromuscular Nondepolarizing Agents; D000077123:Rocuronium