The pharmacokinetics of propofol were studied in 12 healthy Chinese children, aged 4-12 yr, undergoing circumcision under inhalation anaesthesia. All patients received a single i.v. bolus dose of propofol 2.5 mg kg-1 and blood concentrations of propofol over the subsequent 24 h were measured using high pressure liquid chromatography with fluorimetric detection. Data were consistent with a three-compartment model with a mean (SEM) elimination half-life of 209 (29) min and total body clearance of 40.4 (3.6) ml min-1 kg-1. The mean (SEM) apparent volume of distribution at steady state was 5.0 (2.7) litre kg-1 and volume of the central compartment was 0.6 (0.1) litre kg-1. The mean (SEM) ratio of k12:k21 was 1.4 (0.2), suggesting that, after injection of a single bolus dose in children, propofol is distributed rapidly to the shallow compartment. The mean ratio of k31:k10 suggests that lipophilicity constrains return of the drug to the central compartment.

Sixty-four patients undergoing oesophageal surgery were randomly allocated to receive either a continuous lumbar epidural infusion of morphine or fentanyl, or, intramuscular morphine for postoperative analgesia. There was no statistical difference in analgesic requirements between the patients who underwent a thoracotomy for their procedure (n = 50) and those who did not (n = 14), as assessed by the total dose of opioid administered, visual analogue scale (VAS) and pain score (PS) comparison. However, by these criteria, epidural morphine infusion provided the most satisfactory analgesia (P < 0.05). Despite the variable quality of analgesia achieved with the three regimens, the postoperative lung function tests were similar for all groups, and we conclude that routine lung function tests are not an appropriate method of comparing analgesic efficacy. Prophylactic administration of loratadine to 15% of our patients was not shown to be effective in diminishing the incidence of pruritus.

We studied 30 children undergoing circumcision randomly allocated to receive either thiopentone 4 mg.kg-I , propofol2.5 mg.kg-I or midazolam 0.5 mg.kg-I (n=JO) IV over 30 seconds at induction of anaesthesia. Blood pressure and pulse rate during the first 15 minutes of induction were recorded by a Finapres 2300e and a Cardiocap CM-J04, and changes from preinduction baseline compared between the three induction agents and the two recording instruments. Postoperatively, blood levels of the induction agents were measured and recovery from anaesthesia was assessed by clinical criteria, mood and sedation scores and psychomotor performance. The Cardiocap data revealed no statistically significant haemodynamic differences between the three induction agents. Finapres data demonstrated that propofol caused a greater decrease in mean arterial pressure when compared to thiopentone at one minute (P=0.01) and the MAP remained significantly lower than midazolam at five minutes (P= 0.02), illustrating an advantage of continuous over intermittent non-invasive blood pressure monitoring. The midazolam group took longer to identify themselves compared to both the propofol (P= 0.005) and the thiopentone groups (P=0.02), but there was no difference in the groups in time to eye-opening. Psychomotor performance on awakening was significantly worse in the midazolam group compared to the propofol (P< 0.03) and thiopentone groups (P< 0.02). Most children had recovered to 80% of their best, practised, unmedicated, preoperative performance four hours after awakening, irrespective of the induction agent administered. Drug blood levels correlated weakly with both methods of psychomotor assessment (r ~ 0.6). Of the three induction agents, thiopentone caused the least haemodynamic perturbation on induction, and anaesthesia induced with midazolam caused the greatest psychomotor impairment on awakening. Within one hour patients in all drug groups were equally awake, co-operative and co-ordinated.

When comparative auscultation of the chest wall is used by physical therapists to assess the adequacy of pulmonary ventilation, patient posture and regional differences in breath sound intensity can influence clinical interpretation.

We have studied simultaneously the pharmacokinetics of flumazenil and midazolam in 12 healthy Chinese children, aged 5-9 yr, undergoing circumcision. Two hours before operation each patient received midazolam 0.5 mg kg-1 orally for premedication and 0.5 mg kg-1 i.v. during induction. Six minutes after cessation of anaesthesia, a bolus of flumazenil 10 micrograms kg-1 was given i.v., followed by an infusion of flumazenil at 5 micrograms kg-1 min-1 which was maintained until the child could identify himself. Midazolam data were consistent with a three-compartment model with a mean (SD) elimination half-life of 107 (30) min, total body clearance of 15.4 (3.2) ml min-1 kg-1 and apparent volume of distribution at steady state of 1.9 (0.6) litre kg-1. Flumazenil data were best interpreted by a monoexponential function, with a mean terminal elimination half-life of 35.3 (13.8) min, a total plasma clearance of 20.6 (6.9) ml min-1 kg-1 and apparent volume of distribution at steady state of 1.0 (0.2) litre kg-1. No unchanged midazolam was detected in the 24-h urine sample, but 5.8-13.8% of the flumazenil dose was recovered unchanged. At the time of self identification, 4.5 (1.4) min after flumazenil administration, the mean plasma concentrations of midazolam and flumazenil were 163.1 (43.7) and 29.9 (16.1) ng ml-1, respectively.

This laboratory-based bench study was undertaken to evaluate the accuracy and equilibration characteristics of air and saline respectively as CO2 equilibrating media in the silicone balloon of a gastric tonometer and to compare two methods of measuring air Pco2. Two gastric tonometers were suspended in a bath containing 0.9% saline maintained at 37°C. Certified calibration gases at three different CO2 concentrations were bubbled into the bath. When the bath Pco2 measurement was stable the tonometers were primed with 5 ml of air and 2.5 ml normal saline respectively and allowed to equilibrate for 30 and 90 minutes. Following equilibration, samples were aspirated and analysed in duplicate in a blood gas analyser. Bias and precision were calculated from the measured and expected Pco2 values. A consistent negative bias (21–23%) was seen with air at all three CO2 concentrations at 30 and 90 minutes with a coefficient of variation between 2.7 and 3.3%. Imprecise data were obtained with saline at different levels of CO2. A similar experimental set-up was used to compare air Pco2 measurement by a blood gas analyser and an infra-red analyser (Tonocap). Similar bias was obtained with the blood gas analyser with respect to air Pco2 measurement as in experiment 1. The infra-red analyser measurement was highly precise with negligible bias. Air appears to be a better CO2 equilibration medium during bench testing of tonometry producing a systematic negative offset and requiring a uniform correction factor of 1.25. This correction factor is independent of equilibration time and equilibrating CO2 concentration. The use of the infra-red analyser eliminates any bias in the measurement of air Pco2 and obviates the need for a correction factor.

This randomised double-blind study compares the onset, quality and duration of analgesia in two groups of children (n = 30), aged between two and twelve years undergoing circumcision. Under concurrent general anaesthesia, the children received caudal anaesthesia employing either lignocaine 2% with adrenaline 1:200,000 plus normal saline 0.01 mllkg, or lignocaine 2% with adrenaline 1:200,000 plus fentanyl 1.0 microgramlkg. The results show no statistical or clinical difference in the onset, duration, quality of pain relief, or side-effects between the two solutions.

We have compared the incidence of preoperative and postoperative oxygen desaturation in 20 elderly patients undergoing dynamic hip screw insertion for fractured neck of femur, allocated randomly to two groups to receive subarachnoid anaesthesia (SA, n = 10) or a general anaesthetic (GA, n = 10). Oximetry data were recorded during the preoperative night and the first 48 hours after surgery using Satmaster. 1\1 Data associated with zero amplitude signal were automatically invalidated by the software and decreases in Sp02 which were preceded by contemporaneous changes in signal amplitude which conformed to a previously described template were assumed to be artefactual and were discarded from final data analysis. Data demonstrated a wide interpatient variability. However, those patients who desaturated preoperatively continued to do so in the postoperative period. The differences between the preoperative and postoperative oximetry profiles were examined for each patient and demonstrated a significantly longer time spent with Sp02 <90% in the GA group compared with the SA group, in all the recorded time periods, except on the day of surgery. The SA group showed an improvement in oxygen saturation postoperatively when compared to the preoperative night, spending less time with an Sp02 <85%. We conclude that the subarachnoid anaesthetic technique was associated with a lower incidence of postoperative oximetry desaturation when compared with general anaesthetic for these elderly patients undergoing repair of fractured neck of femur.