The use of remifentanil for intubation in paediatric patients during sevoflurane anaesthesia guided by Bispectral Index (BIS) monitoring

We studied the intubating conditions, haemodynamic and endocrine changes following tracheal intubation during sevoflurane anaesthesia guided by Bispectral Index (BIS) monitoring in 40 children who received either remifentanil 1 microg.kg-1 (group R) or saline 1 ml.kg-1 (group S). Acceptable intubating conditions were found in all patients in group R (n = 20), compared to only 12 patients in group S (p = 0.002). There were no intergroup differences in heart rate, systolic blood pressure and plasma concentrations of epinephrine and norepinephrine at any time point and changes in haemodynamic variables throughout the study period were moderate. Titration of sevoflurane delivery to a target BIS of 35 +/- 5 led to almost equal end-tidal sevoflurane concentrations in either group and remifentanil did not affect the BIS. There were no side-effects in either group that required intervention. Intubating conditions during sevoflurane anaesthesia in children were found to be improved by a single bolus dose of remifentanil 1 microg.kg-1.     

Mechanisms contributing to the vaso-active effects of prilocaine in human skin

We investigated the roles of the endothelial nitric oxide and cyclo-oxygenase pathways in mediating the vasoactivity of prilocaine in the skin. We injected prilocaine 1% intradermally into forearm skin of 10 healthy, male subjects. Nitric oxide synthesis was inhibited at a second site by co-injecting prilocaine with l-NAME 1%. We then repeated the injections while blocking the cyclo-oxygenase pathway with aspirin (4 x 600 mg). We measured blood flow responses to the injections using laser Doppler imaging. We found that, after the traumatic effects of injection had subsided, l-NAME reduced the vascular response to prilocaine by a third (p = 0.012), indicating an influence specifically on the drug response. Aspirin had no effect on the response (p = 0.588). We conclude that the vasoactive effects of prilocaine in human skin are mediated partly through the release of endothelial nitric oxide and, although other mechanisms might also be involved, the cyclo-oxygenase pathway does not appear to play a role.     

Adrenocortical function in critically ill patients 24 h after a single dose of etomidate

We compared the effects of single doses of etomidate and thiopentone on adrenocortical function in a randomised controlled clinical trial involving 35 critically ill patients who needed a general anaesthetic. Just before induction of anaesthesia, a baseline blood cortisol sample was taken. Twenty-four hours later we performed a short adrenocorticotrophic hormone stimulation test. No patient had a low cortisol level (< 160 nmol.l-1) at any time during the study. Baseline, pre-ACTH and post-ACTH cortisol levels were similar in the two groups. However, significantly more patients in the etomidate group had an ACTH-stimulated cortisol increment < 200 nmol.l-1. The clinical significance of these findings is not clear, but we conclude that single doses of etomidate may interfere with cortisol synthesis for at least 24 h in the critically ill.     

Anaesthesia and intra-ocular pressure in young children

This study compares the effects of three anaesthetic techniques on intra-ocular pressure (IOP) in infants and children: spontaneous ventilation using nitrous oxide with halothane (group 1) or isoflurane (group 2) and controlled ventilation with atracurium (group 3). The IOP remained constant in groups 1 and 2 until the administration of suxamethonium when it rose significantly; this rise was maintained during tracheal intubation. In group 3 IOP increased on administering atracurium and a further increase was seen during tracheal intubation. Diagnostic intra-ocular pressure measurements should be made during spontaneous breathing prior to tracheal intubation. The IOP was not directly affected by arterial blood pressure or by expired CO2 tension.     

Alfentanil supplemented anaesthesia for short procedures

Thirty-nine unpremedicated patients who presented for cystoscopy were given either alfentanil or saline in a random double-blind fashion immediately before anaesthesia with etomidate, nitrous oxide and enflurane. Alfentanil significantly reduced myoclonus associated with etomidate. During anaesthesia, patients who received alfentanil had smaller minute volumes, lower respiratory frequencies, and smaller increases in heart rate. The incidence of apnoea was not significantly increased. After operation, patients who received alfentanil were prescribed significantly more analgesia, possibly because of their reduced uptake of volatile anaesthetic agent. It is concluded that supplementation with alfentanil improves the quality of anaesthesia induced with etomidate.     

Comparison of etomidate and propofol for anaesthesia in microlaryngeal surgery

Propofol and etomidate were compared as hypnotics in total intravenous anaesthesia for microlaryngeal surgery combined with jet ventilation. Two groups of 15 patients were studied. In group 1, propofol 2.0 mg/kg was used for induction. For maintenance a continuous infusion of 12 mg/kg/hour was used for the first 10 minutes, followed by 9 mg/kg/hour for the next 10 minutes and 6 mg/kg/hour thereafter. In group 2, the induction dose of etomidate was 0.3 mg/kg followed by continuous infusion of 1.8 mg/kg/hour for 10 minutes, 1.5 mg/kg/hour for the next 10 minutes and 1.0 mg/kg/hour thereafter. Alfentanil was given for analgesia and suxamethonium for muscle relaxation. The propofol group showed better surgical conditions, more stable anaesthesia and better recovery according to the Steward score. Recovery times to opening eyes on command were comparable for both groups.     

Intra-operative patient-controlled sedation

Patient-controlled sedation using propofol is described in 23 ASA 1 patients undergoing surgical extraction of third molars. Cardiovascular and respiratory stability was maintained and sedation was no deeper than full eyelid closure with prompt response to verbal command. Amnesia for the extractions was common (70%), but there was no significant amnesia for recovery room events. Intra-operative patient cooperation was good, postoperative patient satisfaction high and all patients stated they liked the self-administration and would use the same technique again. Propofol dose was correlated with both procedure length (r = 0.587; p = 0.003) and surgical difficulty (rs = 0.550; p = 0.010).     

Propofol and alfentanil infusion

In 42 patients undergoing major surgery, anaesthesia was induced by intravenous alfentanil 10 micrograms/kg together with methohexitone 1.5 mg/kg or propofol 2 mg/kg. An infusion of six times these doses per hour was then started; the rate was varied subsequently as indicated by the monitoring of arterial blood pressure, heart rate, EEG and frontalis electromyogram. The mean duration of infusion was 76.7 minutes for propofol and 74.5 minutes for methohexitone and the infusion was stopped about 10 minutes before the end of surgery in each group. The induction dose differed, but the total dose requirement for the two drugs was similar. In every case, anaesthesia was satisfactory. Methohexitone caused a significant rise in mean pulse rate throughout anaesthesia (p less than 0.05, paired t-test). There was no change in mean pulse rate during propofol infusion. The dose of alfentanil used provided excellent control of autonomic reflexes, with negligible respiratory depression. Naloxone was not required. Propofol provided better anaesthesia than methohexitone, with fewer side effects (p less than 0.05, Chi squared test), easier control of the level of narcosis and faster recovery (p less than 0.001, t-test after log transformation).     

A prospective study of liver function in infants and children exposed to daily isoflurane for several weeks

Eleven infants and children presenting for daily radiotherapy for a period of at least 2 weeks were anaesthetised with isoflurane in 33% oxygen and nitrous oxide. They were unpremedicated and given no other agents to supplement anaesthesia. The average number of exposures was 24 (SD 11; range 10-39) and the total anaesthetic time per exposure varied between 15 and 30 minutes. Liver function was assessed by determining serum total bilirubin, aspartate amino transferase, gamma glutamyl transferase and alkaline phosphatase before the start of treatment and at 5-daily intervals thereafter. There was no measurable change in any of these determinants of liver function. All children accepted daily induction of anaesthesia with isoflurane. Induction, maintenance and recovery from anaesthesia were uncomplicated.     

Ketamine as analgesic for total intravenous anaesthesia with propofol

A prospective study of 18 patients who underwent noncardiac surgery was performed to study the use of ketamine as an analgesic during total intravenous anaesthesia with propofol. A comparison was made with the combination propofol/fentanyl. The propofol/ketamine combination resulted in haemodynamically stable anaesthesia without the need for additional analgesics. Postoperative behaviour was normal in all patients and none of the patients reported dreaming during or after the operation. Propofol seems to be effective in eliminating side effects of a subanaesthetic dose of ketamine in humans. We recommend the propofol/ketamine combination for total intravenous anaesthesia for surgery when stable haemodynamics are required.