Anaesthesia in parturients with heart disease: a five year review in an Australian tertiary hospital

At the Royal Women's Hospital, Queensland, between 1993 and 1997 there were 56 vaginal and 22 caesarean deliveries involving 68 women with heart disease. Over half of those women required anaesthetic input, in particular, the women who had the most serious cardiac compromise. There were two maternal deaths, four unbooked and five booked admissions to intensive or coronary care unit.

Population pharmacokinetics of magnesium in preeclampsia

OBJECTIVE

The purpose of this study was to determine the population pharmacokinetics of magnesium from sparse observational data in patients with preeclampsia.

STUDY DESIGN

Serum magnesium concentrations (1-11 per patient) were obtained retrospectively from the records of 116 patients with preeclampsia who had a loading dose of magnesium sulfate (16 or 20 mmol), followed by a maintenance dose (1 mmol/h) over an average of 28 hours. Population clearance, volume of distribution, and the baseline magnesium concentration were estimated using the NONMEM program.

RESULTS

The following population typical values, together with the interpatient variability (expressed as coefficient of variation) were obtained with the use of a 1-compartment model: systemic clearance, 4.28 L/h (37.3%); volume of distribution, 32.3 L (32.1%); baseline concentration, 0.811 mmol/L (18.5%). The average half-life was 5.2 hours. Clonus was not obtunded in 4 patients whose serum magnesium concentrations were similar to the average concentration of 1.7 mmol/L. The variability remaining unexplained after the population model was fitted to the data was 6.5% to 10.8%.

CONCLUSION

This study extended knowledge of the pharmacokinetic disposition of magnesium in preeclampsia. The results are potentially useful for the calculation of loading and maintenance doses, particularly when the relationship between serum concentration and effect in preeclampsia is clarified.

Cough stress rib fractures in two obstetric patients: case report and pathophysiology

The clinical presentation of fractured ribs and physiology of cough in two obstetric patients are described to explain why a rib fracture, not a pneumothorax, occurred on coughing in these patients. At total lung capacity the outward expansion of the lower thorax (flare) during a cough is limited. The costal angles are widened at term pregnancy, and flare may then be almost impossible at total lung capacity. The insertional action of the diaphragm is virtually nil. A direct expiratory action of abdominal muscles predominates over their indirect inspiratory action. The lower ribs are pulled down by the cough and may even fracture from the enormous intrapleural cough pressures which are generated before the glottis opens.

Mendelson syndrome in the labour ward

A case history is reported to caution against the recommendation that a nonparticulate diet be permitted in labour unless participants are not candidates for regional analgesia. A woman was admitted to Intensive Care with Mendelson syndrome. She had been given a meal in early labour, delivered vaginally with epidural analgesia then aspirated stomach contents. Oral intake during labour may continue to be a risk factor for pulmonary aspiration.

A review of anatomical and immunological links between epidural morphine and herpes simplex labialis in obstetric patients

The anatomical basis for facial itch after epidural morphone is outlined. CNS nuclear events which reactivate latent herpes simplex and immune inhibition resulting in maternal mouth vesicles or neonatal infections are described. Morphine is hypothesized to affect these processes and facial itch is only a marker, not a trigger of this trigeminal opioid activity.

Herpes simplex labialis after epidural or parenteral morphine: a randomized prospective trial in an Australian obstetric population

A prospective randomized controlled trial was conducted in women undergoing emergency and elective caesarean section to determine whether epidural morphine predisposes to postoperative herpes simplex labialis and whether the risk is increased or decreased by previous oral herpes or pruritus. Following cannulation of the epidural space, analgesia for labour and/or caesarean section was induced in two groups of similar age, parity, preoperative status and anaesthetic. According to tables of random numbers, 386 were allocated to receive parenteral morphine and 425 to receive epidural morphine. Postoperative herpes labialis was diagnosed by laboratory culture and microscopy. Patients who received epidural morphine were 11.5 times (95% CI 2.6-49.4) more likely than the parenteral morphine group to suffer herpes labialis. A past history of oral herpes increased the risk of herpes labialis by 8.6 times (95% CI 3.3-22.0). When the influence of past herpes infection and route of morphine were taken into account, no separate association between pruritus and herpes simplex labialis could be demonstrated.

Quality assessment in personal anaesthetic practice

Continuing education can improve anaesthetic practice if it is relevant to an individual's work and complications. A practice profile delineates the significance of untoward events. A personal audit of consecutive anaesthetics and associated complications is presented as a first step to checking one's competence over the course of years.