Noninvasive assessment of the maternal cerebral circulation by transcranial Doppler ultrasound during angiotensin II infusion

Longitudinal changes of ocular blood flow using laser speckle flowgraphy during normal pregnancy

PURPOSE

Innovative laser speckle flowgraphy (LSFG) enables noninvasive evaluation of retinal microcirculation and the usefulness has been reported in the field of ophthalmology. LSFG has allowed us to measure the real time changes of retinal blood flow without pupillary dilatations and contrast media. Herein, we investigated the change of retinal blood flow in normal pregnant women during gestation using LSFG.

METHODS

A prospective cohort study was conducted in 53 pregnant women who visited our institution between January, 2013 and July, 2014. Finally, a total of 41 participants without any obstetric complications were available for evaluation. Retinal blood flow was measured with LSFG in a total of 4 times during pregnancy (T1. 11-13 weeks, T2. 19-21 weeks, T3. 28-30 weeks, T4. 34-36 weeks) and mean blur rate (MBR), blowout score (BOS), flow acceleration index (FAI), and resistive index (RI) are analyzed from these measurements. Relations between LSFG parameters and mean arterial blood pressure (MAP) are determined throughout pregnancy.

RESULTS

MBR showed no significant changes throughout pregnancy. BOS showed a tendency to increase in the 3rd trimester. FAI values showed a slight increase from the 1st to 2nd trimester while a significant decrease was noted in the 3rd trimester. RI exhibited no changes between the 1st and 2nd trimesters, values decreased significantly after the 3rd trimester. MAP was positively correlated with BOS, and negatively correlated with FAI and RI.

CONCLUSION

The present study clearly demonstrated that profiles of LSFG parameters demonstrated a decrease of resistance in retinal blood vessels. These changes in indices provide a highly sensitive reflection of physiological changes in vascular resistance due to pregnancy. Thus, LSFG may be useful, as a non-invasive, diagnostic tool to detect pregnancy related disorders such as preeclampsia.

Cerebral Hemodynamics in Preeclampsia: Cerebral Perfusion and the Rationale for an Alternative to Magnesium Sulfate

Preeclampsia and eclampsia continue to be major causes of maternal death. Currently, approximately 18% of U.S. maternal deaths are attributed to hypertensive disorders and eclampsia, and several hundred women die from eclampsia and its complications every year. In the United States, preeclamptic women have received magnesium sulfate as a seizure prophylaxis agent for 3 decades, and this practice is becoming more widely accepted internationally. In addition to a recognized failure rate, there are financial, logistic, and safety concerns associated with the universal administration of magnesium sulfate. Many institutions in the developing world lack the necessary equipment and expertise to administer the medication, and many preeclamptic patients thus do not receive magnesium sulfate before their first seizure. As effective as it has been in reducing mortality from eclampsia, magnesium sulfate is also associated with appreciable morbidity and mortality from administration errors and magnesium toxicity. The availability of an easily administered, cheap, safe, and orally administered alternative to magnesium sulfate would be welcomed in the developing world and would provide an extremely useful alternative therapy to the current standard of care. Recent advances in the understanding of the pathophysiology of preeclampsia and eclampsia, primarily related to cerebral perfusion and blood flow, could allow us to reduce the seizure rate in treated preeclamptic women even further than what is currently reported. This article deals with the rationale behind the use of labetalol as an alternative to magnesium sulfate for the prevention of eclampsia.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to recall that hypertensive diseases of pregnancy contribute a significant portion of today's maternal mortality, explain that methods of preventing eclampsia are not applicable worldwide, and state that understanding of the pathophysiology of preeclampsia/eclampsia may assist in developing safe and effective medications that can be used universally.

Preeclampsia is associated with global cerebral hemodynamic changes

OBJECTIVE

To compare blood flow-velocity parameters in the anterior and posterior cerebral arteries between normotensive and preeclamptic pregnant women.

METHODS

Transcranial Doppler ultrasound was used to measure peak, end-diastolic, and mean velocities in the anterior cerebral artery (ACA) and posterior cerebral artery (PCA) of 22 normotensive and 12 preeclamptic women in the third trimester. All measurements were performed with the subject in the left lateral position. Blood pressure and heart rate were recorded with each Doppler measurement. The mean pulsatility index (PI), resistance index (RI), and cerebral perfusion pressure for each artery was averaged and compared. Statistical significance was set at P <.05.

RESULTS

Preeclamptic women had higher cerebral perfusion pressure in both ACA and PCA (64.7 +/- 5.9 and 78.1 +/- 7.6 compared with 42.4 +/- 2.6 and 54.1 +/- 4.1 mmHg, P <.05), lower PI (0.83 +/- 0.05 and 0.71 +/- 0.04 compared with 0.96 +/- 0.04 and 0.84 +/- 0.02, P <.05), and lower RI (0.55 +/- 0.02 and 0.49 +/- 0.02 compared with 0.60 +/- 0.02 and 0.55 +/- 0.01, P <.05) than normotensive pregnant women.

CONCLUSION

Preeclamptic patients have globally elevated cerebral perfusion pressure and lower resistance in the cerebral circulation than normotensive pregnant women.

Cerebrovascular hemodynamics in chronic hypertensive pregnant women who later develop superimposed preeclampsia

OBJECTIVE

We have previously shown that normotensive pregnant women who later develop preeclampsia demonstrate lower baseline pulsatility index (PI) and resistance index (RI) but normal vasodilatory responses to stimulation tests. In the current study, we tested the hypothesis that women with chronic hypertension who later developed superimposed preeclampsia behave similarly.

METHODS

Transcranial Doppler ultrasound was performed on 17 women with chronic hypertension during the second trimester of pregnancy to measure middle cerebral artery (MCA) velocities. Superimposed preeclampsia developed in seven patients (SUPER group) while the rest did not develop preeclampsia (CHT group). Measurements were performed in the left lateral position at baseline on room air, during 5% CO2 inhalation, and during a 2-minute isometric handgrip test. Blood pressure, heart rate, O2 saturation, and end-tidal PCO2 were recorded with each Doppler measurement. Mean PI, RI, and cerebral perfusion pressure (CPP) at each time were compared using two-way repeated measures analysis of variance. Statistical significance was set at P < .05.

RESULTS

The women who developed superimposed preeclampsia did this an average of 8.7 +/- 1.3 weeks after the study. MCA PI and RI were lower, and CPP higher, in the SUPER group compared to the CHT group (0.64, 0.46, and 80.7 vs 0.74, 0.51, and 63.6, respectively; P < .05). Both maneuvers caused reduction in MCA PI and RI in both groups, whereas CPP increased only in the SUPER group.

CONCLUSIONS

These findings suggest that women destined to develop preeclampsia have cerebral hemodynamic changes that predate the development of overt preeclampsia.

Cerebrovascular Hemodynamics in Pregnant Women With Mild Chronic Hypertension

OBJECTIVE

To evaluate and compare the cerebrovascular autoregulation in pregnant normotensive and mild chronic hypertensive patients without preeclampsia.

METHODS

Transcranial Doppler ultrasound was used to measure peak, end-diastolic, and mean velocities in the middle cerebral arteries of 34 normotensive and 17 mild chronic hypertensive women in the third trimester of pregnancy. Measurements were performed in the left lateral position at baseline, during 5% CO(2) inhalation, and during an isometric handgrip test. Mean pulsatility index, resistance index, and cerebral perfusion pressure at each time were compared using 2-way repeated measures analysis of variance. Using an alpha error of 5%, the statistical power to identify differences in middle cerebral artery indices in response to the two maneuvers was at least 90% and 50% in comparison between the two groups. Significance was P <.05.

RESULTS

Pregnant women with mild chronic hypertension had higher baseline mean blood pressure but similar pulsatility index (0.73 versus 0.75), resistance index (0.50 versus 0.50), and cerebral perfusion pressure (59.9 versus 61.8 mm Hg) compared with normotensive pregnant women. Both maneuvers caused a significant reduction in pulsatility index and resistance index and higher cerebral perfusion pressure. No significant differences were noted in the response to either 5% CO(2) inhalation or isometric handgrip test between the two groups.

CONCLUSION

Pregnant women with mild chronic hypertension show normal cerebral vasomotor reactivity to CO(2) breathing and isometric handgrip. This suggests that the abnormal cerebrovascular autoregulation in preeclampsia is not directly linked to the elevated blood pressure but rather is determined by a separate pathophysiologic pathway.

LEVEL OF EVIDENCE

II-2

The effect of isosorbide dinitrate, a donor of nitric oxide, on maternal cerebral blood flow in gestational hypertension and preeclampsia

OBJECTIVE

The purpose of this study was to investigate the effect of a nitric oxide donor on cerebral perfusion pressure and other blood flow index values in the maternal middle cerebral and basilar arteries.

STUDY DESIGN

Sublingual tablets of 5-mg isosorbide dinitrate were administered to 19 hypertensive pregnant patients. Doppler velocimetry of the middle cerebral and basilar arteries was obtained with a transcranial Doppler with the use of the transtemporal and suboccipital approach.

RESULTS

The mean (+/-SEM) flow velocity in the middle cerebral artery significantly decreased from a baseline of 65.9 +/- 3.1 cm/s to 55.2 +/- 2.2 and 52.0 +/- 2.1 cm/s at 10 and 20 minutes (P <.0001). Resistance area product insignificantly increased from a baseline of 2.0 +/- 0.1 before isosorbide dinitrate to 2.19 +/- 0.11 at 20 minutes. No significant changes were observed in the resistance and pulsatility indices in the middle cerebral artery. The cerebral perfusion pressure did not change significantly after isosorbide dinitrate (84.5 +/- 7.3, 80.8 +/- 6.6, and 78.5 +/- 5.0 mm Hg at 0, 10, and 20 minutes, respectively) nor did the cerebral blood flow index.

CONCLUSION

The results obtained demonstrate that cerebral perfusion pressure is unaltered by isosorbide dinitrate, despite significant changes in maternal blood pressure and in blood flow velocities in the middle cerebral artery.

Assessment of cerebral hemodynamics during roll over test in healthy pregnant women and those with pre-eclampsia

OBJECTIVE

To compare cerebral autoregulatory responses obtained during roll over tests in healthy pregnant women and those with pre-eclampsia in order to assess the middle cerebral artery velocity changes in relation to the roll over test in normotensive and pre-eclamptic women.

PARTICIPANTS

Twenty-two healthy pregnant women and 26 with pre-eclampsia underwent transcranial Doppler measurements of the middle cerebral artery.

METHODS

Systolic, mean and diastolic blood flow velocities and mean arterial blood pressures were recorded in the left lateral position and five minutes after turning to the supine position. Absolute values of mean blood flow velocities, mean arterial blood pressure values and calculated cerebral blood flow indices as well as cerebrovascular resistance area products were compared at different positions among the groups.

RESULTS

Mean arterial blood pressure increased in both groups while turning from the left lateral to the supine position. In women with pre-eclampsia both mean arterial blood pressure and absolute values of mean blood flow velocity values were higher in both positions, compared with healthy pregnant women. In both groups, changing the position resulted in a decrease of absolute values of mean blood flow velocities. Calculated cerebral blood flow indices did not change, while cerebrovascular resistance area products increased significantly in the groups during roll over testing. In women with pre-eclampsia, the increase of cerebrovascular resistance area products was more pronounced as compared with healthy pregnant women.

CONCLUSIONS

In women with pre-eclampsia roll over test results in an increase of the mean arterial blood pressure, which is accompanied by a decreased mean blood flow velocity in the middle cerebral artery. Further studies are needed to clarify the pathophysiological background of cerebral haemodynamic changes in pre-eclampsia.

The maternal cerebral circulation in pre-eclampsia: investigations using Laplace transform analysis of Doppler waveforms

OBJECTIVE

To compare the maternal cerebral circulation in pre-eclampsia and normal pregnancy using an alternative method of Doppler waveform analysis called the Laplace transform analysis, which provides haemodynamic data additional to standard Doppler indices.

DESIGN

A prospective cross-sectional study.

SETTING

Department of Obstetrics and Gynaecology, Nottingham University Hospital.

SAMPLE

The study involved 17 women in the third trimester of a normal pregnancy, 11 with pregnancy-induced hypertension and 26 with pre-eclampsia.

METHODS

Doppler recordings were obtained from the internal and external carotid and middle cerebral arteries, with the measurements in hypertensive women being carried out before any treatment was given. The waveforms were then subjected to Laplace transform analysis which provides information on vessel wall stiffness and upstream and downstream flow conditions.

MAIN OUTCOME MEASURES

The determination of the Laplace transform analysis parameters, including alpha, the natural frequency of oscillation and real pole, and pulsatility index.

RESULTS

Laplace transform analysis demonstrated a significant increase in vessel wall stiffness in all the arteries in hypertensive pregnancies, but this was more marked in pre-eclampsia. The data were also consistent with, but do not prove, increased downstream resistance in the middle cerebral artery in women with pre-eclampsia but not in those with pregnancy-induced hypertension.

CONCLUSIONS

The Laplace transform analysis of Doppler waveforms yields important physiological information concerning the cerebral circulation in pre-eclampsia, not detected using conventional Doppler indices. The results suggest that both pre-eclampsia and pregnancy-induced hypertension are associated with increased cerebral arterial wall stiffness and that, in addition, there may be cerebral vasoconstriction in pre-eclampsia.

Antepartum middle mean cerebral blood flow velocity correlation with maternal hemodynamics

OBJECTIVE

To determine the correlation between simultaneous assessment of maternal middle cerebral blood flow velocity with the other maternal hemodynamic factors of cardiac output and mean arterial pressure.

STUDY DESIGN

Eight normotensive patients were assessed. Maternal cerebral blood flow velocity was assessed using transcranial Doppler. Cardiac output was assessed noninvasively using the thoracic electrical bioimpedance technique over four cycles. Transcranial assessment of cerebral blood flow velocity was done over four cycles. Statistical analysis was then done using the Pearson correlation coefficient and linear regression analysis with stepwise regression. A p-value of < 0.05 was considered significant.

RESULTS

The value of the hemodynamic parameters were cardiac output 8.6 +/- 2.6 L/min, mean arterial pressure 82 +/- 9.7 mm Hg, and mean maternal cerebral blood flow velocity 59.6 +/- 11 cm/s. The pulsatility index was 0.85 +/- 0.15. The mean blood pressure could only explain 42% of the variation in systolic maternal cerebral blood flow velocity and 32% of the variation in mean maternal cerebral blood flow velocity. The mean middle cerebral blood flow velocity did not correlate with cardiac output.

CONCLUSIONS

Middle cerebral artery velocity correlates moderately with mean arterial pressure but not with cardiac output. The control of mean arterial pressure cannot be used as the only indicator of appropriate reduction in cerebral blood flow velocity.

Effects of blood pressure on orbital and middle cerebral artery resistances in healthy pregnant women and women with preeclampsia

OBJECTIVE

The object of the study was to test the hypothesis that preeclampsia leads to an abnormal vascular response to increasing blood pressure in cerebral vessels by analyzing the relationship between mean arterial pressure and resistance index in the central retinal, ophthalmic, and middle cerebral arteries in women with normal pregnancies and women with preeclampsia.

STUDY DESIGN

Transcranial and color flow Doppler ultrasonographic studies were used to determine systolic, diastolic, and mean velocities and the resistance indexes in the central retinal, ophthalmic, and middle cerebral arteries in 24 women with normal pregnancies and 18 women with preeclampsia. In each group the relationship between the mean arterial pressure and the resistance index was determined for each artery by means of linear regression analysis. The Pearson correlation coefficients for each mean arterial pressure versus resistance index relationship were compared between the groups. In a separate analysis middle cerebral artery data obtained from 79 women with preeclampsia (with and without headache) were compared with data from the normal pregnancy group and analyzed in terms of the relationship between mean arterial pressure and resistance index.

RESULTS

The resistance index in women with normal pregnancies decreased with increasing mean arterial pressure in all 3 vessels studied (ophthalmic artery r = -0.33, central retinal artery r = -0. 43, middle cerebral artery r = -0.30). In the women with preeclampsia, however, as mean arterial pressure increased the resistance index increased in the orbital vessels and decreased in the middle cerebral artery (ophthalmic artery r = 0.54, central retinal artery r = 0.65, middle cerebral artery r = -0.25). The correlation coefficients in the women with preeclampsia were significantly different from those in the women with normal pregnancies for the ophthalmic and central retinal arteries (P =. 001) but not for the middle cerebral artery (P =.8). Within-group analysis in the patients with normal pregnancies showed no differences between the correlation coefficients of the studied vessels. In the women with preeclampsia the ophthalmic artery (P =. 02) and the central retinal artery (P =.005) were significantly different from the middle cerebral artery but not from each other. Women with preeclampsia who had headache had a different correlation coefficient for the middle cerebral artery than did those without headache (r = -0.34 versus r = 0.23; P <.001). The correlation coefficient for the middle cerebral artery for women with preeclampsia without headache was not significantly different from the central retinal artery and ophthalmic artery correlation coefficients in the general preeclampsia group.

CONCLUSIONS

Women with preeclampsia demonstrate a different relationship between blood pressure and resistance index in the ophthalmic and central retinal arteries than do women with normal pregnancies. In the middle cerebral artery, however, preeclampsia does not appear to affect the resistance index response to increasing mean arterial pressure in women with headache. In women with preeclampsia without headache the relationship seen in the ophthalmic artery and central retinal artery is preserved in the middle cerebral artery. This may indicate a failure in the autoregulatory capacity of the middle cerebral artery in the presence of headache. Alternatively, the resistance index response in the ophthalmic artery and central retinal artery may represent small-caliber vessel vasospasm that is not present in the middle cerebral artery in women with preeclampsia who have headache.

Changes in maternal middle cerebral artery blood flow velocity associated with general anesthesia in severe preeclampsia

In women with severe preeclampsia, significant increases in mean arterial pressures (MAP) are common after rapid induction of general anesthesia (GA) and tracheal intubation. The objectives of this prospective study were to assess the effects of the rapid induction-intubation technique on middle cerebral artery (MCA) flow velocity in severe preeclampsia and to examine the correlation between mean MCA flow velocity (Vm) and MAP. Eight women with severe preeclampsia (study group) and six normotensive women at term (control group) scheduled to undergo cesarean section under GA were studied. Before induction, patients in the study group received i.v. labetalol in divided doses to lower diastolic pressures to <100 mm Hg. Anesthesia was induced with pentothal 4-5 mg/kg, followed by succinylcholine 1.5 mg/kg to facilitate tracheal intubation. A transcranial Doppler was used to measure Vm. Both Vm and MAP were recorded before induction and every minute for 6 min after intubation. In the study group, after the administration of labetalol, MAP decreased from 129 +/- 9 to 113 +/- 9 mm Hg (P < 0.05), and Vm decreased from 59 +/- 11 to 54 +/- 10 cm/s (P < 0.05). After intubation, MAP increased from 113 +/- 9 to 134 +/- 5 mm Hg (P < 0.001), and Vm increased from 54 +/- 10 to 70 +/- 10 cm/s (P < 0.001). In the control group, while MAP increased significantly from 89 +/- 6 to 96 +/- 4 mm Hg (P < 0.05) after intubation, the concurrent increase in Vm from 49 +/- 5 to 54 +/- 7 cm/s was not significant. There was a significant positive pooled correlation between Vm and MAP (r = 0.5, P < 0.0006) in the study group but not in the control group (r = 0.24). After induction and intubation, both Vm and MAP values were significantly increased in the study group patients at all observation points compared with the control group patients. The findings indicate that Vm increases significantly after rapid-sequence induction of GA and tracheal intubation in women with severe preeclampsia, and there seems to be a direct relationship between MAP and Vm.

IMPLICATIONS

In women with severe preeclampsia, rapid-sequence induction of general anesthesia and tracheal intubation can cause severe hypertension. Our results indicate that the increase in blood pressure is associated with a significant increase in maternal cerebral blood flow velocity and that there is a significant correlation between these two variables.

Prevention of eclampsia

Eclampsia continues to be a major cause of maternal morbidity and mortality rates, especially in underdeveloped nations. Our data indicate that eclampsia may represent the end stage of at least two very different pathophysiological pathways: one in which cerebral perfusion is low because of vasospasm and another in which cerebral perfusion is increased because of abnormal autoregulation and a failure of the normal protective mechanisms. Magnesium sulfate has been extensively used in the management and prevention of eclamptic seizures in the United States and has been recently shown to be superior to both diphenylhydantoin and diazepam. We have shown that magnesium sulfate is a potent vasorelaxant and that its action may depend on improving cerebral perfusion. Nimodipine, a calcium channel blocker with selective cerebrovascular effect, is currently under investigation in severe preeclampsia. The data show that it is as effective as magnesium sulfate in preventing eclampsia, with less maternal and fetal side effects. Magnesium sulfate and nimodipine have opposite effects on the estimated cerebral perfusion pressure as determined with the Doppler ultrasound. We speculate that the estimated cerebral perfusion pressure may be used to determine the type of cerebrovascular abnormality and the most appropriate treatment in each individual patient with preeclampsia.

Persistent cerebrovascular changes in postpartum preeclamptic women: a Doppler evaluation

OBJECTIVE

Our goal was to evaluate the cerebral vasculature in postpartum normotensive and preeclamptic women.

STUDY DESIGN

Nineteen previously preeclamptic women and 19 matched normotensive controls were studied at 6 weeks, and 8 preeclamptic women and 28 normotensive controls were studied at 12 weeks post partum. Systolic, diastolic, and mean velocities, as well as resistance and pulsatility indexes, of the middle cerebral, ophthalmic, and central retinal arteries were recorded. Data are presented as median and range. Statistical significance was set at p < 0.05.

RESULTS

There were no differences in maternal age, parity, heart rate, mean arterial pressure, and proteinuria between the two groups at 6 and 12 weeks post partum. At 6 weeks post partum the preeclamptic group had higher ophthalmic artery diastolic velocity (9.0 cm/sec, 3.1 to 22.3, vs 5.4 cm/sec, 3.0 to 20.1; p = 0.008), ophthalmic artery mean velocity (6.0 cm/sec, 8.8 to 34.8, vs 12.5 cm/sec, 6.8 to 35.4; p = 0.03), and central retinal artery systolic velocity (10.0 cm/sec, 7.6 to 28.0, vs 8.4 cm/sec, 5.2 to 18.3; p = 0.02). The ophthalmic artery resistance index (0.72, 0.43 to 0.88, vs 0.79, 0.66 to 0.90; p = 0.03) and ophthalmic artery pulsatility index (1.56, 0.94 to 2.82, vs 2.03, vs 1.13 to 3.10; p = 0.04) were lower in the preeclamptic group. At 12 weeks post partum the preeclamptic group had elevated ophthalmic artery mean velocity (14.5 cm/sec, 7.9 to 20.2, vs 10.9 cm/sec, 5.5 to 15.4 p = 0.01), central retinal artery systolic velocity (11.1 cm/sec, 6.8 to 15.9, vs 8.5, 5.1 to 15.3; p = 0.02), and central retinal artery diastolic velocity (3.9 cm/sec, 1.2 to 5.2, vs 3.0, 1.4 to 5.8; p < 0.05).

CONCLUSION

In the postpartum period preeclamptic women show persistently elevated central retinal artery systolic velocity, which suggests distal vasoconstriction.

Maternal middle cerebral artery velocimetry in normal pregnancy and postpartum

OBJECTIVE

To study changes throughout gestation and the puerperium of middle cerebral artery flow velocity waveforms obtained by transcranial Doppler ultrasound.

DESIGN

Prospective, observational study.

SETTING

John Radcliffe Maternity Hospital, Oxford, UK.

PARTICIPANTS AND METHODS

Middle cerebral artery velocities were measured by transcranial Doppler ultrasound in 25 nonpregnant women, 22 women longitudinally followed throughout pregnancy and 21 women serially studied from delivery until the late puerperium.

MAIN OUTCOME MEASURES

Transcranial Doppler changes in pregnancy and the puerperium.

RESULTS

The transcranial Doppler ultrasound measurements showed good reproducibility. Signals from one middle cerebral artery could not be obtained in 4.6% of the examinations, but otherwise readings were similar on both sides. Women in the second half of pregnancy had lower middle cerebral artery mean velocities than nonpregnant women. Velocities decreased with advancing gestation but increased in the immediate puerperium to levels comparable to those found in nonpregnant women.

CONCLUSIONS

Transcranial Doppler ultrasound is a noninvasive technique suitable for studying maternal cerebral haemodynamics in pregnancy and postpartum. Middle cerebral artery mean velocity decreased with advancing gestation and increased to nonpregnant values in the immediate puerperium. These physiological changes need to be considered when comparing data with measurements taken in abnormal pregnancy states.

The effect of nifedipine and methyldopa on maternal cerebral circulation

OBJECTIVE

To study how the treatment of severe gestational hypertension affects maternal middle cerebral artery velocimetry.

DESIGN

Prospective, clinical, descriptive study.

SETTING

John Radcliffe Maternity Hospital, Oxford, England.

PARTICIPANTS

Pregnant and puerperal women who required acute or chronic antihypertensive treatment with nifedipine (n = 46) or methyldopa (n = 26), respectively.

METHODS

Transcranial Doppler ultrasound examinations of maternal middle cerebral arteries were performed before and 45 min after nifedipine; and before and 48 hours after the onset of methyldopa therapy. Blood pressure and heart rate were also recorded.

MAIN OUTCOME MEASURES

Clinical and transcranial Doppler changes induced by the antihypertensive medication.

RESULTS

Blood pressure and middle cerebral artery velocities decreased significantly following both short- and long-acting antihypertensive therapy. Nifedipine-induced changes were more pronounced and uniform than those found after methyldopa (16.7% and 6.4% decrease in middle cerebral artery mean velocity, respectively). The middle cerebral artery mean velocity decrease was independent of changes in the blood pressure or heart rate.

CONCLUSIONS

Maternal cerebral haemodynamics are influenced by antihypertensive treatment. The reduction of middle cerebral artery flow velocities following administration of nifedipine and methyldopa may suggest that cerebral vasodilatation is occurring, which is consistent with the concept that cerebral vasospasm is present in women with pre-eclampsia. The cerebral vasodilatation could result from a direct effect of the medication on the arteries in question.

Randomised study assessing the effect of phenytoin and magnesium sulphate on maternal cerebral circulation in eclampsia using transcranial Doppler ultrasound

OBJECTIVE

To assess maternal middle cerebral artery flow velocity patterns as measured by transcranial Doppler ultrasound (TCD) in eclampsia and to investigate the effect of the anticonvulsants magnesium sulphate (MgSO4) and phenytoin on cerebral circulation.

DESIGN

Prospective randomised study.

SETTING

High care obstetric unit, King Edward VIII Hospital, Durban, South Africa.

PARTICIPANTS

Twenty-four eclamptic patients: 13 received MgSO4 and 11 phenytoin.

INTERVENTION

Middle cerebral artery flow velocity waveforms were measured using 2 MHz pulsed Doppler ultrasound via the transtemporal approach in eclamptic patients, before and 15 minutes after the loading dose of anticonvulsant.

RESULTS

Magnesium sulphate significantly reduced the pulsatility index (P = 0.002) and mean flow velocity (P = 0.02) in the middle cerebral artery, whereas phenytoin failed to produce any statistically significant effect. However, differences between groups were not statistically significant. Systolic and diastolic blood pressures were reduced in both the MgSO4 and phenytoin groups.

CONCLUSION

These findings provide firm evidence that MgSO4 relieves cerebral vasospasm, compared with phenytoin, and may therefore be the better drug for the prevention of eclamptic convulsion.