Magnesium sulphate for prevention of eclampsia: are intramuscular and intravenous regimens equivalent? A population pharmacokinetic study

OBJECTIVE

To compare magnesium sulphate concentrations achieved by intramuscular and intravenous regimens used for the prevention of eclampsia.

SETTING

Low-resource obstetric hospitals in Nagpur and Vellore, India.

POPULATION

Pregnant women at risk for eclampsia due to hypertensive disease.

METHODS

A pharmacokinetic study was performed as part of a randomised trial that enrolled 300 women comparing intramuscular and intravenous maintenance regimens of magnesium dosing. Data from 258 enrolled women were analysed in the pharmacokinetic study. A single sample was drawn per woman with the expectation of using samples in a pooled data analysis.

MAIN OUTCOME MEASURES

Pharmacokinetic parameters of magnesium distribution and clearance.

RESULTS

Magnesium clearance was estimated to be 48.1 dl/hour, volume of distribution to be 156 dl and intramuscular bioavailability to be 86.2%. The intramuscular regimen produced higher initial serum concentrations, consistent with a substantially larger loading dose. At steady state, magnesium concentrations in the intramuscular and intravenous groups were comparable. With either regimen, a substantial number of women would be expected to have serum concentrations lower than those generally held to be therapeutic.

CONCLUSIONS

Clinical implications were that a larger loading dose for the intravenous regimen should be considered; where feasible, individualised dosing of magnesium sulphate would reduce the variability in serum concentrations and might result in more women with clinically effective magnesium concentrations; and lower dose magnesium sulphate regimens should be considered with caution.

The normal preterm foetal heart rate pattern

A longitudinal study was carried out on 38 women with low risk pregnancies. These women had cardiotocography at 27-28 wk initially, at fortnightly intervals thereafter until 36 wk and at weekly intervals thereafter until delivery. All cardiotocographs were analyzed by one investigator who was not aware of the individual clinical situation. Of the 232 cardiotocographs, 12 (0.5%) of poor quality were excluded from analyses. The mean base-line heart rate decreased from 142.5 (SD 6.03) beats per min at 27-30 wk to 138.2 (SD 7.4) at term. Analysis of variance for repeated measures showed that the decrease in foetal heart rate with gestation was statistically significant (P < 0.001). The number of accelerations increased with gestation (P = 0.002). There were no significant changes in variability and decelerations with increasing gestation.

Growth pattern of the Indian fetus

OBJECTIVES

To determine the pattern of intrauterine growth and the gestation at birth of Indian fetuses.

METHOD

One hundred twenty consecutive women who had reliable menstrual histories, low-risk pregnancies and who were booked for delivery at the Christian Medical College Hospital, Vellore, before 20 weeks' gestation were recruited to the study. Ultrasound fetal biometry was carried out at 4-weekly intervals from 20 weeks and at weekly intervals after 36 weeks until delivery.

RESULTS

Growth patterns of fetal biparietal diameter and femur length were comparable to those reported in Western populations. However there was a lag in growth of abdominal circumference (AC) after 28 weeks in comparison with that reported in Western populations. The median gestation at delivery following spontaneous labor was 39 weeks. No association was observed between rate of growth of AC and gestation at birth.

CONCLUSION

Slowing of growth of the fetal AC after 28 weeks and a shorter length of gestation result in the birth of smaller babies in this ethnic group. The implications of these findings are discussed.

Inter- and intra-observer variation in the amniotic fluid index

OBJECTIVE

To measure inter- and intra-observer reliability in the amniotic fluid index (AFI).

METHODS

To measure inter-observer reliability, three observers measured the AFI at random in 32 patients without knowing each other's results. To determine intra-observer reliability, each investigator made repeated measurements on ten other patients. Patients at 26-41 weeks' gestation who were referred for an antenatal ultrasound examination were asked to participate. Intra-observer reliability and inter-observer reliability were expressed as intra-class correlation coefficients. Inter-observer agreement was also expressed as the kappa statistic after dichotomizing the AFI (less than 8 cm, 8 cm or more).

RESULTS

The intra-class correlation coefficient for intra-observer reliability exceeded 0.8, and for inter-observer reliability it was 0.67 (95% confidence interval [CI] 0.52-0.79), with an overall kappa of 0.44 (95% CI 0.22-0.65). The percentage disagreement between pairs of observers reached 22-28%.

CONCLUSION

Measurements of AFI have good intra-observer and moderate inter-observer agreement. In clinical use, an AFI level near a cutoff value should be interpreted with caution.

Colposcopy in women with a normal Papanicolaou smear

BACKGROUND

Colposcopy is usually done when the Papanicolaou smear is abnormal so that the necessity for cone biopsy is reduced. However, there is often a strong clinical suspicion of cervical neoplasia even though the smear is normal and this problem of the false negative Papanicolaou smear has not, we feel, been adequately addressed. We, therefore, examined the usefulness of colposcopy in detecting cervical neoplasia in women in whom the Papanicolaou smear was normal.

METHODS

A cross-sectional design was used which included 80 patients in whom cervical neoplasia was suspected and who had undergone colposcopy in one gynaecology unit at the Christian Medical College Hospital, Vellore. The Papanicolaou smear result of these patients was then related to their diagnosis on colposcopy.

RESULTS

The Papanicolaou smears were normal in 56 patients and abnormal in 24. In the normal Papanicolaou smear group there were 18 women with grade I cervical intra-epithelial neoplasia and 3 with grade II lesions. In the abnormal smear group there were 8 women with grade I cervical intra-epithelial neoplasia, 9 with grade II cervical intra-epithelial neoplasia and 1 had microinvasive carcinoma. Patients with abnormal Papanicolaou smears had a relative risk of 7.8 (95% CI 2.4 to 25.8) of having a lesion more advanced than grade I cervical intra-epithelial neoplasia compared with those in whom cervical neoplasia was only suspected clinically.

CONCLUSION

When the clinician suspects cervical neoplasia but the Papanicolaou smear is negative, colposcopy reveals at least grade II cervical intra-epithelial neoplasia in 5% of patients. Such patients, therefore, need to be followed up closely or else have a colposcopy and directed biopsy.

Management of patients with mildly dysplastic cervical smears

The management of patients with mild dysplasia on cervical smears remains controversial. Recent studies have shown that many harbor high grade squamous intraepithelial lesions (HSIL) and human papillomavirus (HPV) and warrant further evaluation rather than follow-up. This prospective study dealt with the evaluation of patients with mild dysplastic smears using colposcopy and directed biopsies with view to identifying HSIL/HPV and treating them. Among 100 cases studied, 61% revealed HSIL/HPV; of them, 10% had high grades. Hence, patients with mildly dysplastic lesions should be evaluated further and managed with histopathologic examination of the biopsy specimen. This protocol may be cost effective for evaluating women with mildly dysplastic smears in a referral center, though it may not be so when compared to a policy of treating the infection, repeating the smears and performing colposcopy and biopsy on all those with persistent abnormality.