Conformational preferences of a polar biaryl: a phase- and enantiomeric purity-dependent molecular hinge.

The favored (R(S)*,M*) diastereoisomer of 2-aryl-pyridine 1 in the solution state results from intramolecular dipole-dipole interactions. In the crystalline state, intermolecular interactions dominate, and the conformation switches reversibly to (R(S)*,P*). Only racemic 1 exhibits this switching property: enantiomerically pure 1 exists as the (R(S)*,M*) diastereoisomer in both the solution and crystalline state.

Uterine rupture and epidural analgesia during trial of labour.

A case of complete uterine rupture during a trial of labour in which epidural analgesia was used is described. The pain of uterine rupture was not masked by the addition of fentanyl 25 micrograms to bupivacaine 0.25% 6 ml but was relieved by bupivacaine 0.375% 6 ml.

Acid aspiration prophylaxis for emergency Caesarean section.

Over a 3.5 year period, 384 patients requiring emergency Caesarean section under general anaesthesia received at random one of six acid aspiration prophylaxis regimens as soon as the decision was made for surgery. In the first phase of the study, sodium citrate administered orally 0.3 M, 30 ml (group C, n = 120) was compared with metoclopramide 10 mg administered intravenously and sodium citrate (group MC, n = 65). In the second phase, all patients received sodium citrate, and either intravenous administration of ranitidine 50 mg (group RC, n = 50), omeprazole 40 mg (group OC, n = 50), ranitidine 50 mg with metoclopramide 10 mg (group RMC, n = 50) or omeprazole 40 mg with metoclopramide 10 mg (group OMC, n = 49). Gastric contents were aspirated using a 16 FG Salem sump tube and acidity measured with a pH meter. Non-parametric tests were used for comparisons. There was no difference in gastric volume or pH between groups C and MC, or among OC, RC, OMC and RMC. After pooling the data, median (range) gastric volume in groups C and MC (55 (0-360) ml) was greater than in groups OMC and RMC (40 (3-270) ml, p < 0.05). Median (range) pH was lower in groups C and MC (4.97 (0.76-6.99)) than in groups OC, RC, OMC and RMC (5.76 (1.11-7.5), p < 0.001). The proportion of patients with pH < 3.5 and volume > 25 ml in the C and MC groups (43/185) was greater than that in the OC, RC, OMC and RMC groups (18/199, p < 0.001). Ranitidine and omeprazole administered intravenously were equally effective adjuncts to sodium citrate in reducing gastric acidity for emergency Caesarean section. Compared with sodium citrate alone, the addition of either ranitidine, omeprazole or metoclopramide alone did not reduce gastric volume while small reductions in gastric volume were seen with the addition of metoclopramide and either ranitidine or omeprazole.

A very small dose of suxamethonium relieves laryngospasm.

Intravenous suxamethonium, in a dose as small as 0.1 mg.kg-1, has been found to be reliable in the treatment of laryngeal spasm. Three episodes of vocal cord spasm observed during direct laryngoscopy were relieved by this dose of suxamethonium.

Inaccuracy of pulse oximetry in patients with severe tricuspid regurgitation.

The accuracy of pulse oximetry was studied in a group of patients with severe tricuspid regurgitation. Measurements of arterial oxygen saturation from a finger and an ear probe were compared with those from a radial arterial blood sample analysed in vitro. Lower values were obtained using the pulse oximeter; the difference ranged from +2% to -11%. The discrepancies between pulse oximeter and laboratory oximeter readings were greater in this group of patients than in a control group who did not have tricuspid regurgitation. There was, however, no correlation between the magnitude of this discrepancy and either the peak central venous pressure or the venous pulse pressure.

The laryngeal mask airway in children. A fibreoptic assessment of positioning.

Clinical and fibreoptic assessment of the positioning of the laryngeal mask airway was performed in 100 children. Clinical observation indicated a patent airway in 98% and severe airway obstruction in 2% of cases. Perfect positioning, as judged by fibreoptic laryngoscopy, was found in 49% and the epiglottis was within the mask in 49%. Fibreoptic evidence of partial airway obstruction in 17% was not detected clinically.

Effects of nitrous oxide on single breath induction with enflurane.

A single vital capacity breath method of inhalational induction using 4% enflurane in 67% nitrous oxide (group I) or 100% oxygen (group II) was studied in 30 patients. Nitrous oxide accelerated induction time (71 (22 SD) seconds in group I versus 136 (29 SD) in group II, P

Oral ketamine premedication for paediatric cardiac surgery--a comparison with intramuscular morphine (both after oral trimeprazine).

In a single-blind controlled study, forty children with congenital heart disease were premedicated with oral trimeprazine 3 mg/kg and either intramuscular morphine 0.1 mg/kg or oral ketamine 10 mg/kg. Cardiovascular and respiratory effects of premedication and degree of sedation induced were similar in the two groups of patients. Oral ketamine is a safe and effective premedicant in this group of patients.

Comparison of conventional and rapid inhalational induction of anaesthesia with enflurane.

Inhalational induction of anaesthesia using either a conventional method or a vital capacity breath of 4% enflurane in 67% nitrous oxide was compared in 30 adult surgical patients. Induction time was significantly faster in patients who took a vital capacity breath (71, SD 22 versus 132, SD 18 seconds, p less than 0.01). There were no significant differences between groups in respect of systolic blood pressure, heart rate, arterial oxygen saturation or incidences of excitement or coughing. The vital capacity breath method was acceptable to 87% of patients.