The pharmacological prevention of pre-eclampsia

Pathophysiology and Medical Management of Systemic Hypertension in Pregnancy

Hypertension in pregnancy includes a group of distinct disorders that require special consideration in both prevention and pharmacologic treatment. In recent years, there have been few advances regarding the pathophysiology and prevention of preeclampsia or in the recommendations for first-line drug therapy for its hypertensive complications. Similarly, the recommendations for pharmacologic treatment of women with chronic hypertension antedating pregnancy have changed little primarily because first-line medications have the advantage of having had more extensive research experience. Recent clinical trials have demonstrated the efficacy and safety of various second-line drugs for the hypertensive disorders of pregnancy; whether these therapies can eventually replace the standard recommended medications will require more extensive long-term investigation.

The herbal medicine Toki-shakuyaku-san improves the hypertension and intrauterine growth retardation in preeclampsia rats induced by Nomega-nitro-L-arginine methyl ester

The chronic inhibition of nitric oxide (NO) synthesis with Nomega-nitro-L-arginine methyl ester (L-NAME) induces a preeclampsia-like syndrome including hypertension and intrauterine growth retardation (IUGR) in pregnant rats. We tested the traditional herbal medicine Toki-shakuyaku-san (TS) for beneficial effects in this model. L-NAME was infused subcutaneously into pregnant rats from day 14 of gestation. TS (1 g/kg, 2 g/kg) was administered by gavage from day 14 to 20. Systolic blood pressure was measured on day 19. On day 20, rats were sacrificed and serum NO levels, placental weight, fetal body weight, fetal cerebrum weight and the thickness of the cerebral cortex were analyzed. TS (1 g/kg, 2 g/kg) inhibited L-NAME-induced hypertension. The decrease in fetal body weight, cerebrum weight and thickness of the cerebral cortex was abrogated by TS (2 g/kg). The effect of TS on blood pressure was found only in the rats that were both pregnant and infused with L-NAME. L-arginine, at the amount equivalent to that contained in TS, showed no effect. Further, the change in serum NO levels induced by TS was only marginal. TS thus improved the hypertension and IUGR in preeclampsia rats induced by L-NAME in a NO-independent manner. These data suggested that TS may be beneficial for the treatment and prevention of preeclampsia.

Hemodynamic responses of broiler pulmonary vasculature to intravenously infused serotonin

Serotonin is a potent pulmonary vasoconstrictor actively accumulated by mammalian platelets and avian thrombocytes and released into the plasma during platelet or thrombocyte aggregation. Serotonin has been implicated in the mechanisms responsible for pulmonary hypertension in several human and animal studies. However, the role of serotonin in pulmonary hypertension syndrome (PHS, ascites) in broilers previously had not been evaluated. In the present study we evaluated the pulmonary hemodynamic responses of broilers to intravenous infusions of serotonin dissolved in 2.5% (wt/vol) mannitol solution (carrier vehicle). Carrier vehicle infusion alone had no influence on any of the hemodynamic variables. Serotonin infusion triggered rapid increases in pulmonary arterial pressure to approximately 50% above pre-infusion baseline values, accompanied by decreases in mean systemic arterial pressure and cardiac output. The peak pulmonary arterial pressure response occurred within approximately 70 s after the start of serotonin infusion and remained elevated above baseline values over the course of a 10-min infusion period. Pulmonary arterial pressure and cardiac output returned to pre-infusion baseline values upon cessation of serotonin infusion, whereas mean systemic arterial pressure returned toward pre-infusion base-line values. Pulmonary hypertensive responses were associated with increased pulmonary vascular resistance (pulmonary vasoconstriction). The peak pulmonary arterial pressure attainable was inadequate to propel the normal cardiac output through the elevated pulmonary vascular resistance. Consequently, the impeded venous return to the left ventricle caused dependent reductions in stroke volume, cardiac output, and mean systemic arterial pressure. Reductions in cardiac output were associated with reductions in stroke volume but not heart rate. Any factor that reduces the pulmonary vascular capacity or increases the pulmonary vascular resistance theoretically can increase the incidence of PHS. The present study provides direct evidence that serotonin can trigger pulmonary vasoconstriction and pulmonary hypertension in broilers.

Salicylate and cocaine: interactive toxicity during chicken mid-embryogenesis

Increased free radical production, due to ischemia and reperfusion, has been postulated as a cause of cocaine's (COC) developmental toxicity. Salicylate reacts with hydroxyl free radicals (*OH) to form stable, quantifiable reaction products, which can be measured with high-pressure liquid chromatography (HPLC). To determine if chicken embryos' brains and hearts were exposed to increased *OH concentrations after injection of COC, an injection of a nontoxic dose of sodium salicylate (NaSAL, 100 mg/kg egg, or 5 mg/egg), followed by 5 injections of COC (13.5 mg/kg or 0.675 mg/egg, every 1.5 h), was administered to eggs containing embryos on the 12th day of embryogenesis (E12). In addition to finding increased *OH concentrations in E12 embryonic hearts and brains, we observed that the developmental toxicity of COC, manifest as vascular disruption (hemorrhage) and lethality, was enhanced by NaSAL injection. These results confirm and extend results of similar experiments performed upon older embryos (E18), and indicate that increased &z.rad;OH concentration in embryonic tissues after COC exposure and toxic interactions of COC and NaSAL can also occur at an earlier stage of development. The results are discussed in light of possible exposure of human fetuses to both COC and salicylates, since COC-abusing pregnant women can be misdiagnosed with pre-eclampsia and aspirin is used to treat this syndrome.

Prevention of pre-eclampsia: status and perspectives 2000

Because pre-eclampsia is a relatively common complication of pregnancy and forms a major cause of maternal, fetal, and neonatal morbidity and mortality, attempts at prevention are justified, but hampered by the fact that as yet no reliable and acceptable screening tests for women at risk are available. Analysis of the many interventions advocated to prevent or delay the onset of pre-eclampsia reveals that dietary calcium supplementation and prophylactic low-dose aspirin treatment have shown promise of efficacy in small randomized, placebo-controlled trials, but the results of large, multicenter trials are generally disappointing. The disappointing results obtained in large, multicenter trials may in part be explained by the lack of strict criteria for inclusion, late initiation of treatment, use of ill-defined end points, different timing of aspirin ingestion, and low patient compliance. Recent evidence that supplementation with vitamins C and E could prevent pre-eclampsia awaits confirmation. Future clinical trials on prevention of pre-eclampsia should be based on results of basic research.

Barbados Low Dose Aspirin Study in Pregnancy (BLASP): a randomised trial for the prevention of pre-eclampsia and its complications

OBJECTIVE

To determine whether prophylactic, low dose controlled-release aspirin improves outcome for pregnant women and their babies in Barbados.

DESIGN

Randomised placebo-controlled trial.

SETTING

The Queen Elizabeth Hospital, Barbados.

POPULATION

All women attending antenatal clinics between 12 and 32 weeks of gestation were eligible, if without specific contraindications to aspirin and unlikely to deliver immediately.

METHODS

Randomisation was computer-generated in the antenatal clinic; 1822 women were allocated to receive 75 mg controlled-release aspirin and 1825 matching placebo.

MAIN OUTCOME MEASURES

Proteinuric pre-eclampsia, other pregnancy-induced hypertension, pregnancy duration, birthweight, stillbirths and neonatal deaths, major neonatal events.

RESULTS

All but three women from each group were followed up successfully. Forty-four percent were primigravid, and 8% had previous obstetric complications. There were no significant differences between the allocated treatment groups in the incidence of proteinuric pre-eclampsia (40 [2.2%] of those allocated aspirin, compared with 46 [2.5%] allocated placebo), of preterm delivery (255 [14.0%] vs 270 [14.8%]), of birthweight < 1500 g (32 [1.7%] vs 33 [1.8%]) or of stillbirth and neonatal death (44 [2.4%] vs 38 [2.1%]). Aspirin was not associated with excess risk of maternal or fetal bleeding.

CONCLUSIONS

The results of this study in Barbados do not support the routine use of low dose aspirin for prevention of pre-eclampsia or its complications, confirming results of previous large trials in other settings.

Randomised controlled trial of ketanserin and aspirin in prevention of pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with extensive endothelial-cell damage and platelet activation, resulting in lower production of vasodilator prostaglandins and increased release of the vasoconstrictors thromboxane A2 and serotonin. Damage to endothelial-cell serotonin-1 receptors leaves vasoconstriction and platelet aggregation mediated by serotonin-2 receptors unopposed. We investigated the role of ketanserin, a selective serotonin-2-receptor antagonist, in lowering the rate of pre-eclampsia among pregnant women with mild to moderate hypertension.

METHODS

We recruited 138 pregnant women into a double-blind, randomised, placebo-controlled trial. They had diastolic blood pressure persistently more than 80 mm Hg before 20 weeks' gestation. 69 women received ketanserin and 69 received placebo. Both groups also received aspirin. Patients were initially given two tablets daily, increased to four tablets daily in diastolic blood pressure was more than 90 mm Hg. Primary outcomes were the development of pre-eclampsia and severe hypertension, and perinatal mortality.

FINDINGS

There were significantly fewer cases of pre-eclampsia (two vs 13; relative risk 0.15 [95% CI 0.04-0.66], p = 0.006) and severe hypertension (six vs 17; p = 0.02) in the ketanserin than in the placebo group. There was also a trend towards less perinatal mortality (one vs six deaths) but this was not significant (p = 0.28). Rates of abruptio placentae and pre-eclampsia before 34 weeks' gestation were lower in the ketanserin group, and mean birthweight was significantly higher.

INTERPRETATION

We found an association between the addition of ketanserin to aspirin and a decrease in the number of cases of pre-eclampsia and severe hypertension, as well as improved pregnancy outcome among patients with mild to moderate midtrimester hypertension.

Endothelial dysfunction in preeclampsia. Part I: Primary prevention. Therapeutic perspectives

Endothelial dysfunction is the final common pathway in the pathogenesis of preeclampsia. Future therapeutic modalities aimed at preventing or treating preeclampsia should either reduce the extent of (or even prevent) endothelial cell dysfunction (primary prevention) or should reduce the consequences of endothelial cell dysfunction (secondary and tertiary prevention). Relevant potential and promising directions for further research will be discussed. Part I of this review concerns the primary prevention of preeclampsia. The etiology of preeclampsia is still unknown. The 4 hypotheses that are the most popular currently are the placental ischemia hypothesis, the immune maladaptation/spiral artery-decidual ¿toxin' hypothesis, the VLDL (very low density lipoproteins)/TxPA (toxicity preventing activity) hypothesis, and the genetic hypothesis. For the near future only the disturbed VLDL/TxPA balance and the imbalance between free radicals and scavengers appear to be amenable for clinical research purposes.