British journal of anaesthesia
-
Randomized Controlled Trial Comparative Study Clinical Trial
End-tidal concentrations of halothane and isoflurane during induction of anaesthesia in young and elderly patients.
Twenty-two young (18-32 yr) and 22 healthy elderly (60-80 yr) patients received either halothane or isoflurane for maintenance of anaesthesia during controlled ventilation. End-tidal fractional concentrations (FE) of the agents were measured for 20 min after their introduction into inspired gas and the increase in end-tidal concentrations of the two agents was compared during induction of anaesthesia using the ratios of FE to the inspired fraction (FI). ⋯ This suggests slower induction of anaesthesia in the elderly if equipotent concentrations of isoflurane are used; the clinical significance of this difference is probably small. Mean FE:FI ratios for halothane in elderly patients were similar to those in the young throughout induction of anaesthesia.
-
Clinical Trial Controlled Clinical Trial
Midazolam acts synergistically with fentanyl for induction of anaesthesia.
The induction dose-response of midazolam was compared with the dose-response of its combination with fentanyl and with that of fentanyl alone in three groups of 60 unpremedicated, ASA physical status I or II women undergoing minor gynaecological surgery. The end-point of induction of anaesthesia was inability to open eyes upon command. ⋯ Twenty-five percent of the ED50 of fentanyl was required in combination with 23% of the ED50 for midazolam to achieve the ED50 of the combination. This degree of synergism may explain mutual potentiation between opioids and benzodiazepines reported previously.
-
We have measured plasma concentrations of local anaesthetics, and the substance fraction of methaemoglobin (MetHb), in infants less than 3 months of age, after application of a lignocaine-prilocaine cream (EMLA). A total of EMLA 2 g was applied over four different skin areas, totalling 16 cm2, for 4 h before anaesthesia for a minor surgical procedure. Sampling was carried out before and 4, 8 and 12 h after application. ⋯ It showed a good inverse correlation with the maximum MetHb values after application of EMLA. Although the MetHb concentrations in the infants younger than 3 months were small, the enzyme capacity may be overloaded when EMLA is administered at the same time as other MetHb-inducing agents. It is concluded that the use of EMLA should be restricted in this age group.
-
Randomized Controlled Trial Clinical Trial
Modification by fentanyl and alfentanil of the intraocular pressure response to suxamethonium and tracheal intubation.
We have measured in a double-blind study the changes in intraocular pressure (IOP) in 40 consecutive patients (pretreated with fentanyl or alfentanil) who received suxamethonium and tracheal intubation. Although IOP increased significantly following administration of suxamethonium, mean IOP in both groups remained significantly less than control values (P less than 0.002). ⋯ There were no significant differences in mean IOP between the fentanyl and alfentanil groups. Both opioids reduced, but did not abolish the haemodynamic responses to tracheal intubation.
-
We have studied the pharmacokinetics of ketamine administered rectally in a dose of 10 mg kg-1 to five children aged 6-9 yr and mean weight 28.80 (SD 6.55) kg. An acceptable level of anaesthesia was not obtained in any patient. Despite this, the degree of analgesia obtained was good and no child required further administration of analgesics during the postoperative period. ⋯ The absorption of ketamine was found to be relatively fast, with a median peak concentration of 160 ng ml-1 (range 96-250 ng ml-1) at 0.75 h (range 0.50-1.00 h) after administration. The plasma concentrations of norketamine were greater than those of the parent drug, with a maximum of 510 ng ml-1 (range 450-810 ng ml-1) at 0.81 h (range 0.50-1.00 h) after administration. The medians of the half-lives of ketamine and norketamine were 3.15 h and 2.56 h, respectively (range 1.57-4.95 h and 1.47-5.30 h, respectively).