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Summary Sixty ASA 1 and 2 children aged between 2 and 16 years who required tracheal intubation as part of anaesthesia for elective surgery were studied. We evaluated intubating conditions, haemodynamic responses and duration of apnoea following propofol 4 mg.kg−1 combined with either remifentanil 1.25 μg.kg−1 (group R), or suxamethonium 1 mg.kg−1 (group S). Tracheal intubation was graded as excellent, good or poor according to ease of laryngoscopy, vocal cord position, coughing, and jaw relaxation and limb movement. Thirty of group S and 28 of group R children were successfully intubated on the first attempt. Overall, intubation conditions were excellent or good in 26/30 (87%) patients in group S and 20/30 (67%) in group R (p

Postoperative analgesia in patients who receive regular oral opioids pre-operatively is frequently suboptimal. To improve management we introduced a regimen using subcutaneous diamorphine infusions with incremental doses. Infusion doses were calculated as half the daily pre-operative dose of oral morphine with the increments as one-sixth of the infusion dose. Results were recorded on the first two postoperative days before (n = 13) and after (n = 23) commencing the new regimen. The percentage of patients reporting severe pain at rest and on movement were significantly reduced by the new regimen (54% and 69% vs. 13% and 40%, respectively) since the opioid dose as a percentage of the pre-operative dose was significantly higher (160% vs. 352%). There were no instances of excessive sedation or slow respiratory rate in any patient. The use of the regimen has resulted in greater doses of opioids being administered with fewer patients in severe pain without significant complications.

A multi-sensor fusion system for monitoring and control of depth of anaesthesia in the operating theatre is described. Two types of anaesthesia measures are considered, the first being based on auditory evoked responses, while the second measure is based on cardiovascular system signals. The first measure is based on analysis of the signal using wavelets and a neuro-fuzzy system, while the second measure is based on analysis of the measurements using a rule-based fuzzy logic system. The two measures are combined to give a final level of depth of anaesthesia using another rule-based fuzzy logic system. The depth of anaesthesia level is fed back to a target controlled infusion system (TCI) to control the infusion of the drug propofol for maintaining a constant level of depth of anaesthesia.

The predictive performance of a 'Diprifusor' target controlled infusion system for propofol was examined in 46 patients undergoing major surgery, divided into three age groups (18-40, 41-55 and 56-80 years). Measured arterial propofol concentrations were compared with values calculated (predicted) by the target controlled infusion system. Performance indices (median performance error and median absolute performance error) were similar in the three age groups, with study medians of 16.2% and 24.1%, respectively. Mean values for 'divergence' and 'wobble' were -7.6%.h-1 and 21.9%, respectively. Measured concentrations tended to be higher than calculated concentrations, particularly following induction or an increase in target concentration. The mean (SD) propofol target concentration of 3.5 (0.7) micrograms.ml-1 during maintenance was lower in older patients, compared with higher target concentrations of 4.2 (0.6) and 4.3 (0.7) micrograms.ml-1 in the two younger age groups, respectively. The control of depth of anaesthesia was good in all patients and the predictive performance of the 'Diprifusor' target controlled infusion system was considered acceptable for clinical purposes.

Depth of anaesthesia is hard to define and not readily measurable. Recently, attention has turned to evoked potentials (EPs) rather than the electroencephalogram (EEG) and they have been validated as a good measure of depth of anaesthesia. However, the amplitudes of the EPs vary from tenths of a microvolt to a few microvolts (/spl mu/V), and are embedded in the spontaneous EEG waveform whose amplitude is typically 10 to 30 /spl mu/V. An intelligent signal processing methodology for evoked potentials in anaesthesia monitoring and control is proposed in the paper. A model-based algorithm based upon autoregressive with exogenous input (ARX) models is used to improve the signal-to-noise ratio. Quantitative feature extraction is implemented to extract the factors describing the changes in amplitudes and latencies of the mid-latency auditory evoked response. In this way, three principal factors are obtained and then merged together using qualitative fuzzy logic to create a reliable index for monitoring depth of anaesthesia.

Changes in-intra-ocular pressure during spontaneous ventilation with a laryngeal mask were compared with controlled ventilation using a tracheal tube in 40 patients undergoing intra-ocular surgery under general anaesthesia. Intra-ocular pressure was measured before induction, after establishing the airway, at the end of the operation and after removal of the airway device. Anaesthesia was induced with propofol and maintained with enflurane and nitrous oxide in oxygen. Mean end-tidal carbon dioxide tension was significantly higher during spontaneous ventilation than during controlled ventilation 5 min after establishing the airway (5.7 versus 4.5) and at the end of surgery (6.1 versus 4.2) (p < 0.001). Despite this, intra-ocular pressures were lower than baseline and similar in the two groups throughout anaesthesia. At the end of surgery, intra-ocular pressure (mmHg) was 11.2 and 8.6 during spontaneous or controlled ventilation respectively. One min after removal of the device, mean intra-ocular pressure (mmHg) in the tracheal tube group (16.0) was slightly higher than baseline (15.3) and was significantly higher than the laryngeal mask group (10.9) (p < 0.01). Spontaneous ventilation with a laryngeal mask is an acceptable alternative to controlled ventilation with tracheal intubation in elective intra-ocular surgery.

Summary A new system for sampling from arterial cannulae has been designed which avoids the need to aspirate flushing solution before taking a sample and limits blood loss. The new system was compared with a standard sampling system and direct arterial sampling using in vitro models. A series of haemoglobin concentrations wen- prepared and sampled using the three sampling methods. There were no clinically significant differences in the values obtained with the different sampling techniques.

Summary A double-blind trial of the effect of droperidol on the incidence of nausea and vomiting in patients using patient-controlled analgesia was carried out in 60 healthy women undergoing abdominal hysterectomy. After a standard anaesthetic including droperidol 2.5 mg as a prophylactic antiemetic, patients were randomly allocated to receive postoperative patient-controlled analgesia with either morphine alone (2mg.ml−1) or morphine (2mg.ml−1) with droperidol (0.2 mg.ml−1) added to the syringe. Verbal scores and visual analogue scores for nausea, vomiting, pain and sedation were made at 4, 12 and 24 h postoperatively, and any requirement for intramuscular prochlorperazine noted. There was no difference between the groups at any time in the amount of morphine consumed or in pain scores. At 12 h, patients receiving droperidol experienced significantly less nausea, and over the first 24 h, 31% required prochlorperazine compared with 59.3% of patients not receiving droperidol. The number of patients with sedation at 24 h was significantly greater in the droperidol group. We conclude that the addition of droperidol to morphine both reduces nausea and the need for further antiemetic treatment.

The value of using a combined infusion of morphine with a variable dose of ketamine for postoperative analgesia following upper abdominal surgery was assessed in a double-blind randomised study of 40 elderly patients. Four groups of 10 patients received an infusion of morphine at 1 mg.h-1, either alone, or combined with ketamine at a rate of 5, 10 or 20 mg.h-1. The addition of ketamine to a continuous infusion of morphine did not significantly improve either analgesia or postoperative lung function. Increasing the dose of ketamine resulted in an increased incidence of postoperative dreaming (p < 0.01).

The Ohmeda 9000 syringe pump was developed in response to the need for an infusion apparatus to administer intravenous anaesthetic agents. It incorporates a bolus facility for the rapid, controlled delivery of loading infusions, or incremental dosing over a background maintenance infusion, and may be interfaced with a controller for computer-driven infusions. The Ohmeda 9000 pump has undergone bench testing and detailed evaluation in clinical practice using a variety of syringe sizes and makes. It is capable of accurate delivery over a range of infusion rates provided the recommended manufacturers' syringes are used with the appropriate pump setting. The pump was easy to use and reliable in clinical research and routine clinical practice. It should find its niche as the first genuinely 'anaesthetist-friendly' infusion pump.

There are few data in the literature that describe the use of remifentanil when administered as a component of an inhalation or total i.v. anaesthetic (TIVA) technique. We studied 251 male and female patients, aged 18-75 years, ASA I-II, undergoing inguinal hernia repair, arthroscopic knee surgery or varicose vein surgery of at least 30 min duration without premedication. Patients were randomized to receive a remifentanil loading dose of 1.0 microgram kg-1 followed by a continuous infusion of 0.5 microgram kg-1 min-1 in combination with isoflurane (end-tidal concentration 0.6%), (Group I, n = 115) or propofol (initial infusion rate 9 mg kg-1 h-1 reduced to 6 mg kg-1 h-1 after 10 min), (Group P, n = 118). The remifentanil infusion rate was reduced by 50%, 5 min after tracheal intubation. Intraoperative stresses were treated with a remifentanil bolus (1 microgram kg-1) followed by an increase in the remifentanil infusion rate. At the insertion of the last suture, the remifentanil infusion and concomitant anaesthetic were switched off simultaneously. Times to spontaneous respiration, adequate respiration and tracheal extubation were significantly shorter in group I compared with group P (6.4 min vs 7.6 min, P < 0.01; 7.6 min vs 9.3, P < 0.003; 7.8 min vs 9.5 min, P < 0.015). Overall mean systolic blood pressures during surgery were greater in group P compared with group I (P < 0.05) but the absolute differences were clinically insignificant (4-5 mm Hg).