British journal of anaesthesia
-
We have examined the in vitro sensitivities of A, B and C fibres in rabbit vagus nerves to local anaesthetic block with a range of local anaesthetic drugs. The nerves were maintained at 37 degrees C and pH 7.4 using an electrolyte solution equilibrated with 5% carbon dioxide. A fibres were the most, and C fibres the least, sensitive to block at low frequency stimulation (0.0167 Hz). ⋯ With stimulation at high frequencies (20 and 40 Hz), C fibres were more sensitive to use-dependent block than A fibres; this effect was more marked with drugs containing an amide than an ester linkage. Molecular size and lipid solubility may inter-react to govern the ability to produce use dependent block. Agents which contain an amide linking group, have a high pKa and are of low lipid solubility, may be used to produce differential C fibre block.
-
Comparative Study Clinical Trial Controlled Clinical Trial
Comparison of the neuromuscular block induced by mivacurium, suxamethonium or atracurium during nitrous oxide-fentanyl anaesthesia.
We compared the neuromuscular and cardiovascular changes following administration of mivacurium 0.15, 0.20 and 0.25 mg kg-1, suxamethonium 1.0 mg kg-1 or atracurium 0.5 mg kg-1 i.v. in 41 (ASA physical status I or II) patients during nitrous oxide-fentanyl anaesthesia. Mean onset times for total ablation of twitch response for mivacurium 0.15, 0.20 and 0.25 mg kg-1, were 2.5, 2.4 and 2.7 min, respectively, similar to that for atracurium (2.5 min), but longer than for suxamethonium (1.1 min) (P less than 0.05). ⋯ Following neostigmine 0.045 mg kg-1, mean times for twitch tension to recover from 10% to 90% of control were similar for mivacurium (9.7 min) and atracurium (10.5 min). Transient decreases in mean arterial pressure (greater than 20%) were observed in seven of 15 patients who received the two higher doses of mivacurium.
-
Randomized Controlled Trial Clinical Trial
Postoperative analgesia with extradural clonidine.
The analgesic effect of extradural clonidine was evaluated in a double-blind study. In the recovery room, following orthopaedic or perineal surgery 20 ASA I and II patients were allocated randomly to two groups. The extradural clonidine (EC) group received clonidine 2 micrograms kg-1 in isotonic saline solution 15 micrograms ml-1. ⋯ In the EC group, the mean (SD) maximum pain relief was 68.2 (24.1)% of the initial VAS score, but it was only 14.7 (25.2)% in the ES group. The mean duration of analgesia, before injection of morphine, was significantly longer in the EC group (210 (87) min) compared with the ES group (45 (27) min) (P less than 0.001). Drowsiness and moderate hypotension were observed in the EC group.
-
To quantify the neuromuscular blocking effect of vecuronium on the diaphragm and the adductor pollicis, single twitch stimuli were applied to the phrenic nerves at the neck and the ulnar nerve at the wrist in anaesthetized patients. The evoked responses were measured simultaneously by recording the transdiaphragmatic pressure with a differential pressure transducer and the adductor pollicis strength with a force displacement transducer. ⋯ The mean (SD) doses required to depress adductor pollicis and diaphragm responses to 50% (ED50) were 30 (9) micrograms kg-1 and 37 (12) micrograms kg-1, respectively. Corresponding values for 95% depression of the twitch response (ED95) were 48 (13) micrograms kg-1 and 67 (23) micrograms kg-1 (P less than 0.02), indicating that the diaphragm required approximately 40% more vecuronium for subtotal abolition of the single twitch response.