British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Central nervous and cardiovascular effects of i.v. infusions of ropivacaine, bupivacaine and placebo in volunteers.
We have compared the incidence of CNS symptoms and changes in echocardiography and electrophysiology during i.v. infusions of ropivacaine, bupivacaine and placebo. Acute tolerance of i.v. infusion of 10 mg min-1 was studied in a crossover, randomized, double-blind study in 12 volunteers previously acquainted with the CNS effects of lignocaine. The maximum tolerated dose for CNS symptoms was higher after ropivacaine in nine of 12 subjects and higher after bupivacaine in three subjects. ⋯ A threshold for CNS toxicity was apparent at a mean free plasma concentration of approximately 0.6 mg litre-1 for ropivacaine and 0.3 mg litre-1 for bupivacaine. Bupivacaine increased QRS width during sinus rhythm compared with placebo (P < 0.001) and ropivacaine (P < 0.01). Bupivacaine reduced both left ventricular systolic and diastolic function compared with placebo (P < 0.05 and P < 0.01, respectively), while ropivacaine reduced only systolic function (P < 0.01).
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Randomized Controlled Trial Clinical Trial
Effect of lignocaine and pH on propofol-induced pain.
Propofol has the disadvantage of pain on injection. A higher partition of propofol in the aqueous phase of the preparation causes a higher incidence of pain on injection while addition of 1% lignocaine to propofol reduces pain. The low concentration of this local anaesthetic and the rapid pain relief observed indicates that mechanisms other than local anaesthesia are involved, that is change in pH. ⋯ The concentration of propofol in the aqueous phase was lower when 1% Diprivan was mixed with 1% lignocaine (0.376 g litre-1) or HCl (0.392 g litre-1) compared with 1% Diprivan and saline (0.476 g litre-1) mixed in the same proportion. Thus pH changes may modify propofol-induced pain on injection by a mechanism different from the effect of the local anaesthetic on the vascular endothelium. Our findings may explain why lignocaine mixed with propofol causes less pain than injection of lignocaine followed by propofol.
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Randomized Controlled Trial Clinical Trial
Cardiovascular effects of an intubating dose of rocuronium 0.6 mg kg-1 in anaesthetized patients, paralysed with vecuronium.
We have studied, in adult patients, ASA I-II, the cardiovascular effects of an intubating dose of rocuronium 0.6 mg kg-1. After induction, patients were paralysed with vecuronium and the trachea intubated. Heart rate (HR) and non-invasive mean arterial pressure (MAP) were measured every 1 min. ⋯ Mean MAP decreased in both groups within 10 min to a similar extent after rocuronium and saline, that is from 74.9 to 72.1 mm Hg and from 74.7 to 72.2 mm Hg, respectively (both P < 0.001). There were no differences in MAP at any time between the rocuronium and saline groups. We conclude that an intubating dose of rocuronium, in the absence of haemodynamic effects related to paralysis itself, resulted in a limited increase in HR without change in MAP, probably because of its weak vagolytic activity.
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Clinical Trial Controlled Clinical Trial
Extradural pain relief in labour: bupivacaine sparing by extradural fentanyl is dose dependent.
The minimum local analgesic concentration (MLAC) of bupivacaine in labour is defined as the effective concentration in 50% of subjects (EC50). We have used the technique of double-blinded sequential allocation to quantify the bupivacaine sparing effect of the addition of four different doses of extradural fentanyl in 223 labouring women. There were five groups: (1) plain bupivacaine (control); (2) bupivacaine with fentanyl 1 microgram ml-1; (3) bupivacaine with fentanyl 2 micrograms ml-1; (4) bupivacaine with fentanyl 3 micrograms ml-1; and (5) bupivacaine with fentanyl 4 micrograms ml-1. ⋯ We observed a reduction in MLAC of 18%, 31% (P = 0.03%), 55% (P < 0.0001) and 72% (P < 0.0001) with fentanyl 1, 2, 3 and 4 micrograms ml-1, respectively, demonstrating a significant negative linear trend (P < 0.0001) with increasing fentanyl dose. The incidence of pruritus was increased significantly with fentanyl 4 micrograms ml-1 (P = 0.0015). Because of this, fentanyl 3 micrograms ml-1 may be the optimal dose when the aim is bupivacaine sparing extradural analgesia during labour.
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Comparative Study Clinical Trial Controlled Clinical Trial
Combined spinal-extradural anaesthesia for preterm and term caesarean section: is there a difference in local anaesthetic requirements?
In a non-blinded observational study, we have tested the null hypothesis that there is no difference in local anaesthetic requirements for subarachnoid anaesthesia between women presenting for Caesarean section at term or preterm (38-42 and 28-35 weeks' gestation, respectively). Using a combined spinal-extradural technique, 2.25 ml of 0.5% hyperbaric bupivacaine was given, in the sitting position, to 50 women presenting for Caesarean section. ⋯ All women in the term group developed adequate anaesthesia with the subarachnoid dose alone. Onset of anaesthesia was slower in the preterm group (median 15 vs 5 min) with a lower incidence of hypotension (P = 0.0005).