The influence of variations in blood flow on pulsed doppler ultrasonic heating of the cerebral cortex of the neonatal pig.

Pulsed Doppler ultrasound examination of the fetal cerebral circulation may cause potentially harmful temperature elevations in brain tissue immediately beneath the insonated segment of the skull. This study measured the effect of variations in cerebral blood flow on ultrasonic heating of the cerebral cortex of anaesthetised, neonatal pigs. Wide and narrow ultrasound beams were used. Pulsed ultrasound exposures were delivered in 90 s bursts at 5.8 micros pulse length, pulse repetition frequency 8 kHz and centre frequency 3.5 MHz. Studies were performed with the target at the focus of a fixed, stationary beam of 0.3 cm -6 dB beam width (narrow beam) and I(spta) 1.4 W/cm(2) (n = 11), or with the target in the near field of a fixed, stationary beam of 1.6 cm -6 dB beam width (wide beam) and I(spta) 3.6 W/cm(2)(n = 5). The 90 s ultrasound exposures were performed under three different conditions of ambient cerebral blood flow: baseline (during normocarbic, normoxic conditions), increased (during hypercarbic, hypoxic conditions) and absent (postmortem). Cerebral blood flow was measured using the radiolabelled microsphere technique. In the narrow beam studies, cerebral blood flow during baseline was 34 +/- 4 ml/min/100 g, rising to 109 +/- 32 ml/min/100 g during the increased phase (p < 0.001); in the wide beam studies baseline flows were 29 +/- 9 ml/min/100 g, whereas flows in the increased phase were 128 +/- 32 ml/min/100 g (p < 0.001). There was no difference in the heating curves for normal, increased and absent cerebral blood flow for exposure to the narrow beam, when mean temperature increases of 1.5 degrees C at 90 s were recorded in each case (p > 0.21, power > 0.8). However, the heating curves for the wide beam were significantly different for the three rates of blood flow with mean temperature increases of 1.9 degrees C (normal flow), 1.7 degrees C (increased flow) and 2.4 degrees C (no flow) recorded at 90 s (p < 0.05).

Quiet resting is not necessary prior to routine antenatal blood pressure measurement.

A premeasurement period of 5 minutes quiet resting is recommended prior to measuring blood pressure. The aim of this study was to determine the effect of this period of rest on the level of blood pressure in pregnant women. One hundred pregnant women had their blood pressure measured on a single visit using a QuietTrak ambulatory blood pressure monitor, used to remove human observer bias. Group 1 (n = 50) had blood pressure measured as soon as possible on entering the clinic room and again after 5 minutes rest. Group 2 were rested for 5 minutes on entry to the clinic room prior to the first blood pressure measurement and had the second measurement taken after a further 5 minutes rest. Results were compared in the 2 groups using ANOVA. In Group 1, the initial, mean systolic blood pressure was 116.6 versus 115.5 mmHg taken after 5 minutes quiet rest (p = 0.66). The corresponding diastolic values were 66.2 versus 64.1 (p = 0.40). In Group 2, the initial mean systolic blood pressure was 116.2 versus 115.6 taken after 5 minutes quiet rest (p = 0.85). The corresponding diastolic values were 68.5 versus 65.6 (p = 0.34). Blood pressure was as likely to rise as to fall after a period of quiet rest. It is not necessary to have pregnant women quietly resting during routine visits before having blood pressure measured.

Endometrial balloon ablation under local analgesia and intravenous sedation.

We report a series of women (n = 16) with menorrhagia undergoing endometrial balloon ablation under local analgesia with light sedation. Ten women had significant, coexistent medical problems. The median duration of the procedure was 8.6 minutes (range 8.47-9.5 minutes). Postoperative assessment included pain scores assessed by linear analogue scale; requirement for opiate analgesia; length of postoperative stay and patient satisfaction with the procedure. The minimum postoperative follow-up was 6 months. The procedure was well-tolerated and in 80% of cases either no postoperative analgesia or simple analgesia only was required. Two women were admitted overnight, 1 for social reasons and the other for pain control. Three women ages 44, 54 and 55 years were amenorrhoeic at 6 months; 8 women were still menstruating but satisfied with the outcome and 5 women are seeking further treatment for menorrhagia. While the longer-term efficacy of the procedure remains to be established these results indicate that endometrial balloon ablation under local analgesia and light sedation, a simple and acceptable technique, may be a suitable alternative to more difficult procedures such as rollerball ablation. This is most likely to be the case in appropriately selected women who are willing to accept a reduction in menstrual flow rather than amenorrhoea as the treatment outcome. The main disadvantage of balloon ablation is the cost of the disposable balloons and the need for a dedicated electrosurgical unit.

Which Korotkoff sound should be used for the diastolic blood pressure in pregnancy?

There is a gathering momentum favouring the adoption of the 5th Korotkoff sound to identify diastolic blood pressure in pregnancy. Our objective was to measure interobserver reliability for indirect blood pressure measurement in pregnancy for systolic and diastolic measurements and to calculate the difference in diastolic pressure measured by the 4th and 5th Korotkoff sounds. To minimize bias we used trained but previously inexperienced observers with proven, normal auditory acuity. The observers were paired in 4 teams and performed a series of 334 blinded, simultaneous observations of systolic and diastolic blood pressure measurements taken from pregnant women between 12-41 weeks' gestation. Reliability was measured by intraclass correlation coefficient for paired measures and kappa for the detection or nondetection of 4th (K4) and 5th (K5) Korotkoff sounds. K4 was undetected in 36% of observations and K5 was undetected in 2% of observations. Reliability for detection or nondetection of Korotkoff sounds was fair for K4 (kappa 0.36) and moderate for K5 (kappa 0.58). Reliability was good between observers for systolic, K4 and K5 diastolic measurements (intraclass correlation > or = 0.80). The mean difference between the diastolic pressure measured by K4 and K5 was 15 mmHg for all measurements and 8 mmHg for the top quartile of measurements (p <0.001). We found K5 to be more often and more reliably detected than K4. If units adopt K5 in preference to K4, consideration will need to be given to lowering treatment thresholds for women with borderline or mild hypertension.

Blood pressure measurement in pregnancy--a survey of methods used in teaching hospitals in South Australia.

A voluntary, anonymous 10-point multiple choice questionnaire was used to assess variability in methods used to measure blood pressure in pregnancy in 5 South Australian teaching hospitals. Medical and midwifery staff working in maternity units attached to teaching hospitals in South Australia were asked to complete a survey of their current practice related to the measurement of blood pressure in pregnant women; 213 replies were received from 440 surveyed (48% response rate). There was a lack of standardization of practice for: positioning of the patient, use of the 4th or 5th Korotkoff sound for diastolic blood pressure, cuff selection, rounding of the measurement, selection of the left or right arm, and period of premeasurement resting. Systematic errors averaging 10-15 mmHg can be expected in measurement of blood pressure in pregnancy due to failure of standardization of method. There is a need for standardization of method which is not being met by present methods of staff training in teaching hospitals.

Assessment and management of female urinary incontinence--a survey of current practice.

A survey of conference delegates attending the Urogynaecology Day at the 1997 Annual Scientific Meeting of the Royal Australasian College of Surgeons indicated that practitioners are inconsistent in their approach to the use of preoperative urodynamics evaluation for women with stress incontinence and disagree about the significance of the low pressure urethra.

Ultrasonic heating of the brain of the fetal sheep in utero.

The fetal sheep was used as a model to determine the extent of ultrasound-induced heating of brain tissue in procedures involving pulsed Doppler examination of fetal intracranial arteries. Temperature measurements were recorded in late-gestation fetuses insonated in utero. The centre frequency was 3.5 MHz and a pulse repetition rate of 6 to 10 kHz produced a power output of 0.6 or 2 W. The brain was insonated in the near field of a focussed beam where the -6-dB beam width was 1.7 cm for the 0.6-W transducers and 1.2 cm for the 2-W transducers. Mean (standard error) maximal temperature increases of 3.0 degrees C (0.3) and 12.5 degrees C (1.3), respectively, were recorded in dead fetuses. The mean values obtained in normally perfused living fetuses were lower by 43% and 30%, respectively, showing that vascular perfusion substantially limited ultrasonic heating in sheep fetal brain tissue. There were no changes in blood flow to the heated brain tissue as measured using radiolabelled microspheres.

Community-based learning in obstetrics for undergraduate medical students.

Medical students on their obstetrics and gynaecology attachment were randomly assigned to attend hospital (n = 24) or general practice (n = 18) obstetric clinics once weekly for 4 weeks. The students completed self-assessment questionnaires at the beginning and end of the attachment. There was a significant improvement in the level of knowledge and skills required for antenatal care, care in labour and postnatal care by the end of the attachment, with no difference between hospital or general practice groups. There was a significant increase in the level of interest in the future practice of obstetrics only in the general practice group. However, this difference could be explained by the greater number of students in the general practice group who were by chance in the 'no or don't know' category at the start of their attachment. We conclude that general practice based clinical teaching of obstetrics can be a suitable alternative to hospital-based clinical teaching for undergraduate medical students.

Pulsed ultrasound and electrocortical activity in fetal sheep.

The aim of this study was to determine if low intensity ultrasound affects electrocortical activity in chronically instrumented fetal sheep. A 3.5-MHz transducer was attached to each fetal skull (n = 9) and activated periodically to emit pulses of 5.8 microseconds duration at a repetition rate of 2 kHz generating a power output of 60 mW. The power supply was activated in 30-s bursts every 180 s but random electronic switching energized the transducer with 50% of bursts. On average, 175 bursts of ultrasound were delivered to the fetus over 19.5 h. Blinded analysis of continuous recordings of electrocortical activity showed it to be unaffected by the ultrasound exposures. Therefore, it is unlikely that ultrasonic examination of human fetuses will affect normal cyclical electrocortical activity.

Reference ranges and ultrasonographic exposure conditions for pulsed Doppler sonographic studies of the fetal internal carotid artery.

We describe the 5th to 95th percentiles for the resistive index from the fetal internal carotid artery and measurements of (1) scanning time and (2) axial distance between transducer face and the fetal skull during pulsed Doppler examinations. Cerebral resistance peaks at 30 weeks' gestation and declines thereafter. The median duration of pulsed Doppler exposure was 31 seconds (range, 4-80 seconds), and the median transducer-skull distance was 2.2 cm (range, 1.3-6.2 cm). Our data provide reference ranges covering the entire period of fetal viability and help define ultrasonographic exposure conditions during pulsed Doppler examinations of fetal intracranial vessels.

Antihypertensive drug effects on placental flow velocity waveforms in pregnant women with severe hypertension.

Doppler studies of the uterine and umbilical arteries were performed in 24 acutely hypertensive pregnant women. Women were divided into 2 groups: Group 1 (diastolic blood pressure (DBP) > 110 mm Hg) received placebo (n = 6) or 10 mg oral nifedipine (n = 9); Group 2 (DBP > or = 110 mm Hg) received 10 mg oral nifedipine (n = 5) or 10 mg intravenous hydralazine (n = 4). Treatment allocations were random within groups and the investigator and patient were blind to the treatments. Baseline flow velocity waveforms (FVW) and posttreatment FVW's at 30, 60 and 120 minutes were recorded. There was no significant difference between baseline and posttreatment FVW indices within or between groups. Placebo was as effective as nifedipine in lowering blood pressure over 2 hours of study. There were no significant adverse effects of treatment.

Abnormal internal carotid and umbilical artery Doppler in the small for gestational age fetus predicts an adverse outcome.

Doppler studies of the internal carotid and umbilical arteries were performed in 29 women admitted to the antenatal ward with a diagnosis of being small for gestational age. The primary aim of the study was to determine whether an abnormal internal carotid waveform was associated with a poor perinatal outcome defined as: fetal distress, acidosis at birth or perinatal death. A poor perinatal outcome occurred in 18 pregnancies including six perinatal deaths. There was a highly significant association between an abnormal internal carotid waveform and a poor outcome and this was particularly so at a gestational age of < or = 34 weeks where the sensitivity, specificity and predictive values were all 100%. No baby with a normal internal carotid waveform had a poor outcome. Abnormal umbilical waveforms tended to occur earlier in pregnancy than abnormal internal carotid waveforms and were also predictive of an adverse perinatal outcome. Whether this information should be used clinically is not clear as abnormal umbilical artery and internal carotid waveforms were sometimes present for weeks before delivery occurred for fetal reasons.

Intractable postpartum haemorrhage managed by angiographic embolization: case report and review.

A case of intractable postpartum haemorrhage successfully managed by angiographic embolization is presented. The literature concerning angiographic embolization and internal iliac artery ligation is reviewed. Angiographic embolization is a superior method to internal iliac artery ligation in appropriately selected cases of obstetric haemorrhage, and may also be used successfully in cases where internal iliac ligation and/or hysterectomy has failed to control pelvic haemorrhage. Angiographic embolization is a potentially life- and fertility-saving procedure.