Labetalol does not alter the placental and fetal blood flow or maternal prostanoids in pre-eclampsia

Pre-gestational diabetes: Maternal body mass index and gestational weight gain are associated with augmented umbilical venous flow, fetal liver perfusion, and thus birthweight

OBJECTIVES

To assess how maternal body mass index and gestational weight gain are related to on fetal venous liver flow and birthweight in pregnancies with pre-gestational diabetes mellitus.

METHODS

In a longitudinal observational study, 49 women with pre-gestational diabetes mellitus were included for monthly assessments (gestational weeks 24-36). According to the Institute Of Medicine criteria, body mass index was categorized to underweight, normal, overweight, and obese, while gestational weight gain was classified as insufficient, appropriate or excessive. Fetal size, portal flow, umbilical venous flow and distribution to the fetal liver or ductus venosus were determined using ultrasound techniques. The impact of fetal venous liver perfusion on birthweight and how body mass index and gestational weight gain modified this effect, was compared with a reference population (n = 160).

RESULTS

The positive association between umbilical flow to liver and birthweight was more pronounced in pregnancies with pre-gestational diabetes mellitus than in the reference population. Overweight and excessive gestational weight gain were associated with higher birthweights in women with pre-gestational diabetes mellitus, but not in the reference population. Fetuses of overweight women with pre-gestational diabetes mellitus had higher umbilical (p = 0.02) and total venous liver flows (p = 0.02), and a lower portal flow fraction (p = 0.04) than in the reference population. In pre-gestational diabetes mellitus pregnancies with excessive gestational weight gain, the umbilical flow to liver was higher than in those with appropriate weight gain (p = 0.02).

CONCLUSIONS

The results support the hypothesis that umbilical flow to the fetal liver is a key determinant for fetal growth and birthweight modifiable by maternal factors. Maternal pre-gestational diabetes mellitus seems to augment this influence as shown with body mass index and gestational weight gain.

Neonatal haemodynamic effects following foetal exposure to labetalol in hypertensive disorders of pregnancy

OBJECTIVE

Hypertensive disorders of pregnancy (HDP) affect foetal outcome. Labetalol is frequently used to lower maternal blood pressure and prolong pregnancy. Conflicting evidence exists for specific neonatal side effects described after maternal labetalol treatment. Our aim was to investigate neonatal effects of foetal exposure to labetalol on cerebral oxygenation and extraction.

METHODS

In a prospective observational study, clinical characteristics, vital parameters and cerebral oxygen delivery and extraction were collected during the first 24 h of life in labetalol-exposed preterm neonates and compared with two control groups.

RESULTS

Twenty-two infants with a mean gestational age of 28.9 weeks, born from labetalol-treated mothers with HDP were included and matched with 22 infants with non-labetalol-treated mothers with HDP and 22 infants without maternal HDP. No significant differences between groups were found neither in heart rate, blood pressure and inotropic support, nor in mean regional cerebral oxygen saturation and fractional tissue oxygen extraction.

CONCLUSION

Foetal labetalol exposure associated effects on preterm heart rate, blood pressure, cerebral oxygenation and extraction are not demonstrated. Maternal disease severity seems to play a more important role in neonatal cerebral haemodynamics. Maternal labetalol treatment has no clinically important short term side effects in the preterm neonate.

Direct Vasodilators and Sympatholytic Agents

Direct vasodilators and sympatholytic agents were some of the first antihypertensive medications discovered and utilized in the past century. However, side effect profiles and the advent of newer antihypertensive drug classes have reduced the use of these agents in recent decades. Outcome data and large randomized trials supporting the efficacy of these medications are limited; however, in general the blood pressure-lowering effect of these agents has repeatedly been shown to be comparable to other more contemporary drug classes. Nevertheless, a landmark hypertension trial found a negative outcome with a doxazosin-based regimen compared to a chlorthalidone-based regimen, leading to the removal of α-1 adrenergic receptor blockers as first-line monotherapy from the hypertension guidelines. In contemporary practice, direct vasodilators and sympatholytic agents, particularly hydralazine and clonidine, are often utilized in refractory hypertension. Hydralazine and minoxidil may also be useful alternatives for patients with renal dysfunction, and both hydralazine and methyldopa are considered first line for the treatment of hypertension in pregnancy. Hydralazine has also found widespread use for the treatment of systolic heart failure in combination with isosorbide dinitrate (ISDN). The data to support use of this combination in African Americans with heart failure are particularly robust. Hydralazine with ISDN may also serve as an alternative for patients with an intolerance to angiotensin antagonists. Given these niche indications, vasodilators and sympatholytics are still useful in clinical practice; therefore, it is prudent to understand the existing data regarding efficacy and the safe use of these medications.

Prevention of peri-induction hypertension in preeclamptic patients: a focused review

Many medications have been used to prevent the hypertensive response to the induction of general anesthesia and laryngoscopy in preeclamptic patients, with varying results. In this focused review, we summarize the available data and pharmacologic profiles of these drugs. Several different drug classes may be used safely; however, magnesium bolus, lidocaine, calcium channel antagonists other than nicardipine, and hydralazine are not recommended. Further research is warranted into the hemodynamic impact of varying the induction drug dose or combining different classes of drugs.

Do Commonly Used Oral Antihypertensives Alter Fetal or Neonatal Heart Rate Characteristics? A Systematic Review

OBJECTIVE

To examine fetal (FHR) and neonatal heart rate patterns following use of common oral antihypertensives in pregnancy.

METHODS

A systematic review of randomized controlled trials (RCTs), observational studies (N >/= 6 women), and animal studies. Data were abstracted (two reviewers) to determine relative risk (RR) (or risk difference (RD) for low event rates) and 95% CI.

RESULTS

Eighteen RCTs (1858 women), one controlled observational study (N = 22), and seven case series (N = 117) were reviewed. Most hypertension was pregnancy-induced (N = 14 studies). The FHR was assessed by cardiotocogram (CTG) (N = 17 studies (visual interpretation); 1 study (computerized CTG), or umbilical artery velocimetry (N = 4). Four studies examined neonatal heart rate. In placebo-controlled RCTs (N = 192 women), adverse FHR effects did not differ between groups [9/101 (drugs) vs. 7/91 (placebo); RD 0.02, 95% CI (- 0.06, 0.11); chi2 = 1.02]. In six drug vs. drug RCTs (295 women), adverse FHR effects did not differ between groups [29/144 (methyldopa) vs. 42/151 (other drugs); RR 0.72, 95% CI (0.49, 1.07); chi2 = 0.69]. In one labetalol vs. placebo trial, neonatal bradycardia did not differ between groups [4/70 (labetalol) vs. 4/74 (placebo); OR 1.06, 95% CI (0.26, 4.39)], while in three drug vs. drug RCTs, neonatal bradycardia was not observed (0/24 vs. 0/26).

CONCLUSIONS

Available data are inadequate to conclude whether oral methyldopa, labetalol, nifedipine, or hydralazine adversely affect fetal or neonatal heart rate and pattern. Until definitive data are available, FHR changes cannot be reliably attributed to drug effect, but may be due to progression of the underlying maternal or placental disease.

Antihypertensive therapy during pregnancy

Hypertensive disorders in pregnancy are a leading cause of maternal and perinatal morbidity and mortality. Overall, hypertension complicates approximately 10% of pregnancies. The incidence is higher in patients with predisposing factors including nulliparity, multiple gestation, preexisting hypertension or diabetes, a previous pregnancy complicated by preeclampsia-eclampsia, familial history of preeclampsia, hydrops fetalis and rapidly growing hydatidiform moles.

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.

Effects of antihypertensive drugs on the unborn child: what is known, and how should this influence prescribing?

This review discusses the use of antihypertensive drugs in acute and long term treatment of hypertensive disorders of pregnancy, including their placental transfer and adverse effects on the fetus. All antihypertensive agents cross the placental barrier and are present in varying concentrations in the fetal circulation, with varying resultant effects on fetal metabolism. Antihypertensive drugs that are lipid soluble will pass through the placental barrier with ease whereas the most polar will not. Placental transfer diminishes under conditions that decrease the surface area or increase the thickness of the placenta. Highly protein-bound drugs form complexes which impair placental transfer while unbound drugs cross the placenta easily. The ionised drug form is highly charged and cannot cross lipid membranes while the un-ionised form can easily cross the placenta. A decrease in placental blood flow can slow down the transfer of lipid soluble drugs to the fetus. Close monitoring of the fetal and maternal condition is necessary for the rest of the pregnancy after antihypertensive therapy is commenced. Methyldopa is the initial drug of choice for long term oral antihypertensive therapy in pregnancy. Neither short term nor long term use of methyldopa is associated with adverse effects. In the short term (<6 weeks) beta-receptor antagonists are effective and well tolerated provided there are no signs of intrauterine growth impairment. ACE (angiotensin converting enzyme) inhibitors are contraindicated in the second and third trimesters of pregnancy because they are teratogenic. Intravenous dihydralazine is widely used for rapid reductions of severely elevated blood pressure. The use of nifedipine concurrently with MgSO4 must be approached with caution because the combination is associated with severe hypotension, neuromuscular blockade and cardiac depression. In the last decade, knowledge of antihypertensive drugs used in pregnancy has improved and new drugs, e.g. calcium antagonists, which have been shown to have great potential for use in pregnancy, have been introduced. Safety for the fetus with newer drugs has not yet been adequately evaluated. Currently, well established and cost effective drugs such as methyldopa (long term use) and intravenous dihydralazine (rapid reduction) are the agents of choice to treat hypertensive disorders of pregnancy.

Preanaesthetic management of the obstetric patient

The obstetric patient presents unique challenges to the anaesthesiologist. The physiologic changes in the mother during pregnancy and the anaesthetic implications of these changes, associated with the pathophysiologic conditions frequently superimposed on the pregnancy, distinguish the parturient from the other patients about to undergo anaesthesia and surgery. Furthermore, the obstetric patient may be in acute pain from labour and frequently needs urgent surgical intervention because of sudden changes in the condition of the mother or the fetus.

Controlling the hemodynamic response to laryngoscopy and endotracheal intubation

The hemodynamic response to the stress of laryngoscopy and endotracheal intubation does not present a problem for most patients. However, patients with cardiovascular or cerebral disease may be at increased risk of morbidity and mortality from the tachycardia and hypertension resulting from this stress. These hemodynamic effects gained notice after the introduction and use of muscle relaxants, such as curare and succinylcholine, for endotracheal intubation at the time of anesthesia induction. A variety of anesthetic techniques and drugs are available to control the hemodynamic response to laryngoscopy and intubation. The method or drug of choice depends on many factors, including the urgency and length of surgery, choice of anesthetic technique, route of administration, medical condition of the patient, and individual preference. The possible solutions number as many as the medications and techniques available and depend on the individual patient and anesthesia care provider. This paper reviews these medications and techniques to guide the clinician in choosing the best methods.

Use of glucagon to treat neonatal low-output congestive heart failure after maternal labetalol therapy

Labetalol is used to treat hypertensive crisis in women with preeclampsia. Glucagon was used as a nonselective beta-adrenergic agonist to treat a preterm infant with symptomatic beta-blockade caused by maternal labetalol therapy.

The effects of dihydralazine, labetalol and magnesium sulphate on the isolated, perfused human placental cotyledon

OBJECTIVE

To assess the effects of dihydralazine, labetalol and magnesium sulphate on the vascular tone in the isolated, perfused human placental cotyledon.

METHODS

In vitro perfusion of the fetal compartment of isolated, human placental cotyledons.

RESULTS

None of the drugs affected basal vascular tone. The thromboxane A2-mimic U46619 and endothelin-1 induced a concentration-dependent increment in perfusion pressure, while 5-hydroxytryptamine induced a variable increase, and norepinephrine induced a small, transient increase in perfusion pressure. After preconstriction with U46619, magnesium sulphate (1.5 x 10(-3) to 6 x 10(-3) mol/l) induced a decrease in perfusion pressure, while dihydralazine (10(-6) to 10(-4) mol/l) or labetalol (10(-7) to 10(-4) mol/l) enhanced the perfusion pressure. These effects of dihydralazine and labetalol were unaffected by treatment with indomethacin 10(-6) mol/l, but could be reversed by addition of magnesium sulphate 6 x 10(-3) mol/l. Labetalol 10(-6) to 10(-4) mol/l also caused an increase in the perfusion pressure induced by endothelin-1, but showed no effects after preconstriction with 5-hydroxytryptamine. Pretreatment with labetalol 10(-4) mol/l inhibited the transient increase in perfusion pressure induced by norepinephrine 3 x 10(-5) mol/l.

CONCLUSIONS

The present data demonstrated that the commonly used vasodilating agents labetalol and dihydralazine do not produce vasodilatation in the human perfused cotyledon after vasoconstriction induced by agents of suggested importance for maintenance of fetal placental vascular tone, and that high concentrations of these drugs may even enhance vasoconstriction induced by thromboxane and endothelin-1 in this area. Magnesium sulphate may show the potential to reverse such unwanted effects of dihydralazine and labetalol.

Pregnancy in women on haemodialysis and peritoneal dialysis

Pregnancy in women with renal insufficiency and end-stage renal disease, while uncommon, is definitely possible, and such women should not assume they are infertile. Contraception should be prescribed for those who do not want to conceive. For the woman who is dialysed during pregnancy, the risks can be minimized by aggressive blood pressure control and prompt diagnosis and treatment of bleeding episodes; however, no degree of vigilance can guarantee that a woman will not suffer any of the severe complications that have been described in pregnant dialysis patients. Intensive dialysis should be undertaken to maintain chemistries that are as nearly normal as possible, and premature labour should be treated with indomethacin. Our current state of knowledge suggests that the success rate of pregnancy in dialysis patients is no better than 52%. It remains to be seen whether CAPD and erythropoietin improve the currently poor outcome. While transplantation offers the best chance of child bearing for women with end-stage renal disease, transplantation is not always possible. Thus we no longer discourage women on dialysis from becoming pregnant as long as they understand that the likelihood of success is small and that serious risks are involved, and as long as they are willing to follow the time-consuming regimen we think it is necessary for their safety. We hope that, in time, increased experience with pregnant dialysis patients will lead to more successful outcomes and that the possibility of parenthood will be added to the improved quality of life in these women.

Labetalol in hypertension during the third trimester of pregnancy: its antihypertensive effect and pharmacokinetic-dynamic analysis

The hypotensive effect, kinetics, and concentration-response relationship of labetalol, alpha beta- and alpha 1-adrenoceptor blocking drug, were studied in seven women with a moderate-to-severe hypertension (averaged diastolic blood pressure [DBP] of 100 to 120 mm Hg measured during a 1- to 2-day hospitalization period) during the third trimester of pregnancy who received the oral twice-daily doses of 150 to 450 mg. These dosages were individually selected by attaining a therapeutic goal of DBP < or = 100 mm Hg or systolic blood pressure (SBP)/DBP reduction of > 30/15 mm Hg, as compared with the pretreatment value, at any time during the 12-hour dosing interval for a 3- to 5-day dosage escalation period. Labetalol concentrations in plasma were measured by a high-performance liquid chromatography with fluorescence detection, and the plasma drug concentration-response relationship was analyzed by a sigmoidal Emax model. Labetalol decreased significantly (P < 0.05 to 0.01) the pretreatment SBP/DBP (166.3 +/- 5.2/110.3 +/- 3.0 mm Hg, mean +/- SEM) without any recognizable side-effects during the twice-daily dosing period in the mothers. Peaked concentrations occurred at 1 hour postdose in all patients. The elimination half-lives ranged from 4.3 to 6.9 hours, and the apparent oral clearance from 31.9 to 73.3 mL/min/kg. The pharmacodynamic parameters (Emax and EC50) analyzed by the Emax model revealed a 3- to 5-fold interindividual variability. The gestational ages at delivery ranged from 34 to 37 weeks, and the birth weights were < 2000 g in 6 of the 7 neonates. Four neonates developed respiratory distress syndrome after delivery, and one infant died of pulmonary hypoplasia 3 months later. The results indicate that 1) labetalol orally administered in a twice-daily regimen as done in this study is an effective antihypertensive drug in women with hypertension during late pregnancy, and 2) interindividual variability in the kinetic factor (e.g., oral clearance) as well as that in the pharmacodynamic factor (e.g., EC50) appear to be related to the overall variability in the hypotensive responsiveness to the drug. However, whether labetalol and/or hypertension per se would have been related to the fetal outcome remains unanswered from the present study.

Effect of labetalol infusion on uterine and fetal hemodynamics and fetal cardiac function

The effect of intravenously-administered labetalol (1 mg/kg) on uterine and fetal hemodynamics and fetal cardiac function was studied in 13 women with pregnancy-induced hypertension. Maternal mean blood pressure had decreased significantly by the end of the labetalol infusion and 30 min later. The pulsatility indices reflecting peripheral vascular resistance did not change in the main uterine, placental arcuate, umbilical, and fetal middle cerebral and renal arteries, nor did the parameters reflecting fetal cardiac function. A subgroup of seven patients with a more pronounced decrease in maternal blood pressure and three cases with original signs of fetal asphyxia did not react hemodynamically in a different manner from the group as a whole with respect to the circulatory effects of labetalol. These findings obtained by Doppler and colour Doppler methods in as comprehensive manner as possible seem to demonstrate a wide tolerance of maternal and fetal hemodynamics to the moderate decrease in maternal blood pressure achieved by labetalol infusion under short-term conditions in cases of pregnancy-induced hypertension.

Labetalol therapy in pregnancy induced hypertension: the effects on fetoplacental circulation and fetal outcome

We prospectively studied the effects of oral labetalol therapy in patients with moderate to severe pregnancy induced hypertension (PIH). The outcome variables were blood pressure control, effect on umbilical artery flow velocity waveforms (UAFVW) and fetal outcome. Forty-two patients were recruited, all had moderate to severe PIH. The mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) on entry were 154 +/- 7 mmHg and 104 +/- 5 mmHg, respectively. All had significant proteinuria. After 1 week on labetalol therapy, 85% of patients had their blood pressure controlled. The reduction in both SBP and DBP was statistically significant. There were no significant changes in UAFVW, Resistance Index (RI), uric acid or platelets. The mean fetal age on entry was 246 +/- 10 days while gestation at delivery was 258 +/- 17 days. The mean birth weight was 2712 +/- 609 g. No perinatal mortality occurred in this study. Labetalol is an effective drug in controlling blood pressure and does not adversely affect the UAFVW. No neonatal problems were attributed directly to the drug. Fetal outcome was satisfactory despite the 12 fetuses that were growth-retarded. Labetalol allows safe prolongation of pregnancies complicated by PIH.

Effects of labetalol on uterine blood flow and cardiovascular hemodynamics in the hypertensive gravid baboon

OBJECTIVE

The purpose of this study was to investigate the effects of labetalol on uterine blood flow and cardiovascular parameters in acutely instrumented, hypertensive gravid baboons.

STUDY DESIGN

During the latter half of pregnancy six gravid baboons were acutely instrumented, with ultrasonic flow probes placed on ipsilateral, external iliac, and uterine arteries and a flow-directed pulmonary artery catheter in the pulmonary artery. After a stable arterial pressure baseline was obtained, norepinephrine was infused to increase mean arterial pressure by at least 20%. A 20-minute hypertensive steady state was obtained. Labetalol at 0.5 and 1.0 mg/kg was randomly infused, followed by a 2.0 mg/kg dose, each over 1 minute. A 20-minute recovery period followed every labetalol infusion, allowing the hypertensive steady state to reestablish. External iliac and uterine blood flow measurements were continuously recorded during the baseline and experimental trials. Mean arterial blood pressure, heart rate, pulmonary artery and capillary wedge pressure, central venous pressure, and cardiac output were obtained at 5, 10, and 15 minutes during each steady state and after each labetalol infusion.

RESULTS

Labetalol at all dosages significantly reduced the mean arterial pressure and the systemic vascular resistance at 1.0 and 2.0 mg/kg. External iliac blood flow was not consistently significantly reduced; however, uterine blood flow was significantly reduced after the 1.0 and 2.0 mg/kg labetalol dosages (p < 0.05). Although uterine vascular resistance tended to increase after the 1.0 and 2.0 mg/kg doses, statistical significance was not achieved.

CONCLUSION

Low-dose labetalol (0.5 mg/kg) significantly reduces the pharmacologic hypertensive gravid baboon's mean arterial blood pressure without adversely affecting uterine blood flow.

Neonatal adaptation in hypertensive pregnancy--a study of labetalol vs hydralazine treatment

Twenty mothers with moderate to severe preeclampsia were allocated to labetalol (Trandate) or hydralazine (Apresolin) antihypertensive treatment. Arterial blood gas analysis was performed at delivery from the clamped cord. Neonatal blood pressure, heart rate and axillary temperature were registered 0.5, 2, 6, 12, 24, 36, 48 hours and 3, 4 and 7 days after birth. Respiratory rate was registered at the same intervals until 36 hours after birth. Blood glucose levels were measured 2, 6, 12 and 24 hours after birth. Peripheral blood flow in the calf was measured at 24 hours of age. Gestational age did not differ between the two groups; 36 (27-40) in the labetalol, and 35 (29-37) weeks in the hydralazine group (median and range). Median cord pH was lower, and the number of infants with a cord pH < 7.20 was higher in the hydralazine group. Blood glucose levels were lower in the labetalol group at 6 hours of age (p < 0.05). No other differences were found between the two groups. The conclusion is that no clinical signs of adrenergic blockade have been found at 24 hours of age, and no negative effect of labetalol on the neonatal adaptation compared to hydralazine antihypertensive treatment was found.

Ephedrine and phenylephrine for avoiding maternal hypotension due to spinal anaesthesia for caesarean section

The effects of i.v. vasopressors on Doppler velocimetry of the maternal uterine and placental arcuate arteries and the fetal umbilical, renal and middle cerebral arteries were studied during spinal anaesthesia in 19 healthy parturients undergoing elective caesarean section. Fetal myocardial function was investigated at the same time by M-mode echocardiography. The patients were randomized into two groups, to be given either ephedrine or phenylephrine as a prophylactic infusion supplemented with minor boluses if systolic arterial pressure decreased by more than 10 mmHg from the control value. Both the vasopressors restored maternal arterial pressure effectively. The ephedrine group showed no significant differences in any of the Doppler velocimetry recordings relative to the baseline values, but during the phenylephrine infusion the blood flow velocity waveform indices for the uterine and placental arcuate arteries increased significantly and vascular resistance decreased significantly in the fetal renal arteries. Healthy fetuses seem to tolerate these changes in uteroplacental circulation well, however, since the Apgar scores for the newborns and the acid-base values in the umbilical cord were within the normal range in both groups. The results suggest that some caution is required when selecting the specific vasopressor agent, the dosage and the mode of administration for the treatment of maternal hypotension secondary to spinal anaesthesia for caesarean section.

The effect of pregnancy on renal function: physiology and pathophysiology

Marked changes in renal function occur with pregnancy. We present a summary of these changes in this review and give insight into possible mechanisms if they are known. Controversies exist regarding the therapy of pregnancy-induced hypertension and asymptomatic and recurrent bacteriuria. The current views on these topics are given. Specific renal diseases are summarized, including transplantation, and optimum management strategies and maternal and fetal prognosis during pregnancy are given.

Changes in adrenoceptors and monoamine metabolism in neonatal and adult rat brain after postnatal exposure to the antihypertensive labetalol

1. The purpose of the present study was to investigate the acute (single injection), direct (chronic treatment) and the long-lasting effects after exposure to the alpha 1/beta-adrenoceptor antagonist labetalol during rat brain development on adrenoceptors and monoamine metabolism. 2. In 10-day-old rat pups, subcutaneously administered labetalol (10 mg kg-1) passed the blood-brain barrier, reaching a level of 2.1 micrograms g-1 tissue in the brain 90 min after injection. 3. Chronic labetalol treatment (10 mg kg-1, s.c., twice daily) during the first 10 days of life significantly increased alpha 1-adrenoceptor binding in the hypothalamus (+39%), but not in the occipital cortex. 4. This chronic postnatal labetalol treatment did not result in long-lasting changes in alpha 1- and beta-receptors measured on day 60. 5. A single labetalol injection (10 mg kg-1, s.c.) on postnatal day 10 significantly increased noradrenaline (NA) metabolism in all brain regions tested (+25 to 105%), but had no effects on 5-hydroxytryptamine (5-HT) or dopamine metabolism. 6. Chronic labetalol treatment between postnatal (PN) days 1 and 10 also increased NA metabolism on PN 10 (3-methoxy-4-hydroxyphenylglycol (MHPG)/NA, +20 to 100%), suggesting that tolerance to the acute effect of labetalol did not occur. A slight increase in 5-HT metabolism (20%) was induced by the chronic labetalol treatment in the hippocampus and meso-limbic system. 7. In general, long-lasting effects on NA metabolism could not be detected on day 60 more than one month after the treatment. However, 5-HT metabolism was significantly increased in all four brain regions measured (+20 to 70%). 8. We conclude that chronic labetalol exposure during early postnatal rat brain development does not cause long-lasting changes in beta-receptor number or NA metabolism, but appears to be critical for the rate of 5-HT metabolism in later life.

Prevention and treatment of pregnancy-associated hypertension: what have we learned in the last 10 years?

High blood pressure (BP) complicates approximately 10% of all pregnancies. Hypertension in pregnancy falls into four categories: (1) preeclampsia-eclampsia, (2) chronic hypertension of whatever cause, (3) preeclampsia-eclampsia superimposed to chronic hypertension or renal disease, and (4) transient or late hypertension (gestational hypertension). Preeclampsia, the association of hypertension, proteinuria, and edema, accounts for more than 50% of all the hypertensive disorders of pregnancy and is a major cause of fetal and maternal morbidity and mortality. Unfortunately, distinguishing between preeclampsia and other causes of hypertension on clinical grounds can be difficult because of the lack of specific tests for differential diagnosis. Increased vascular resistance has been claimed as the primary cause of preeclampsia; however, a variable hemodynamic profile with relatively high cardiac outputs, normal filling pressures, and inappropriately high systemic vascular resistances is now reported by most investigators. Imbalance between vasodilator and vasoconstrictor eicosanoids may account for platelet activation and increased responsiveness to pressor peptides. Altered prostacyclin (PGI2) to thromboxane A2 (TxA2) ratio in maternal uteroplacental vascular bed may favor local platelet activation and vasoconstriction contributing to placental insufficiency and fetal distress. Alternatively, recent evidence seems to suggest that fetal umbilical placental circulation may be the site of the primary vascular injury. Whether low-dose aspirin prevents preeclampsia because it inhibits the excessive maternal TxA2 or whether the partial inhibition of fetal TxA2 is also of therapeutic value remains to be established. Treatment of severe hypertension in pregnancy is probably important to prevent cardiac failure or cerebrovascular accidents in the mother. The need for pharmacological therapy of mild to moderate hypertension is still debated, since no formal studies are available to clarify whether pharmacological treatment in such instances effectively reduces maternal or fetal risk. For the treatment of preeclampsia, hydralazine and nifedipine may be used when delivery is not applicable. Labetalol and diazoxide are effective for hypertensive emergencies. Life-threatening hypertension that does not respond to more conventional therapy is an indication for the use of sodium nitroprusside. For chronic hypertension, alpha-methyldopa remains the treatment of choice; if ineffective, hydralazine or beta-blockers are suitable. Effectiveness and safety of other molecules remain elusive.

Maternal and fetal haemodynamics in hypertensive pregnancies during maternal treatment with intravenous hydralazine or labetalol

Intravenous treatment with 10 mg of hydralazine or 100 mg of labetalol was randomly allocated to 30 hypertensive pregnant women. Umbilical artery flow velocity waveforms were recorded using a pulsed Doppler duplex scanner (ATL Mk V) and umbilical artery pulsatility index (PI) and fetal heart rate (FHR) were derived from these recordings. Maternal blood pressure decreased significantly after both drugs. Maternal pulse rate increased after hydralazine but did not change significantly after labetalol. FHR did not change significantly after hydralazine but decreased after labetalol. PI decreased after hydralazine and increased after labetalol--most fetuses showed little change but a few in each group showed large changes in PI, as did two of five additional patients studied. We attributed the decrease in PI in some fetuses after hydralazine to vasodilation, and the increase in PI in some fetuses after labetalol to vasoconstriction in the fetoplacental circulation, suggesting that fetal beta-blockade may occur after maternal treatment with labetalol.

Postpartum amaurosis

Blindness is a rare but dramatic complication of pregnancy and delivery. We present the case of a patient who developed toxemia at the time of delivery that with ineffective treatment resulted in cortical blindness without seizure activity. The pathogenesis as well as the diagnostic workup and treatment of this unusual complication are discussed.

Doppler findings in the fetal and uteroplacental circulation: a promising guide to clinical decisions

The combination of real time and Doppler ultrasonic methods has opened up new possibilities for the study of fetal and uterine haemodynamics in humans particularly for the umbilical, uterine and fetal cerebral arteries. A pathological finding in blood velocity waveforms seems to be an early and consistent alteration which precedes other markers of chronic fetal distress. The challenges are to differentiate between fetal and uteroplacental aetiologies of chronic fetal asphyxia and to search for effective treatment of early fetal distress. Recent data on the practical value of haemodynamic studies in different perinatal complications is presented in this review.

Half-life of maternal labetalol in a premature infant

Intra-uterine heart arrhythmia, postpartal respiratory insufficiency, bradycardia and hypoglycaemia were observed in a premature infant (37 weeks gestational age) delivered by a caesarian section. The mother had been treated with adequate doses of labetalol because of pregnancy-induced hypertension and her plasma concentration was found to be 89 micrograms/l one day after delivery. The half-life of labetalol in the plasma of the infant was found to be approximately 24 h, i.e. substantially longer than in normal adults. The half-life of labetalol in newborn premature infants may be prolonged as compared to normal adults. More studies are required regarding the pharmacokinetics of this agent in premature infants and newborn babies.

Acute hypertensive crisis in pregnancy

Severe pre-eclampsia is a state of acute afterload increase where compensation may be total by use of the Frank-Starling mechanism and/or increased adrenergic drive, or may be uncompensated in a patient with limited or exhausted preload reserve. As such, we are presented with a diverse group of patients and antihypertensive therapy ideally should be individualized. In reality we are dealing with a complex situation because of the presence of the fetus raising concerns about direct effects on the fetus as well as on uteroplacental blood flow. This limits our choice of agents to those with extensive use in pregnancy except in complicated or resistant cases. For these reasons, hydralazine is the antihypertensive agent of choice for treatment of acute hypertensive emergencies in pregnancy. In the complicated case other agents such as sodium nitroprusside or nitroglycerin may be more appropriate and, in these cases, hemodynamic monitoring should be performed to allow not only greater safety, but also to tailor therapy to the individual hemodynamic profile.

Labetalol. A reappraisal of its pharmacology, pharmacokinetics and therapeutic use in hypertension and ischaemic heart disease

Since labetalol was first reviewed in the Journal (1978), its scope of therapeutic use has expanded and become better defined. Labetalol is an adrenoceptor blocking drug with combined alpha- and beta-blocking properties. These result in a more favourable haemodynamic profile for labetalol compared with 'pure' beta-blockers or pure alpha-blockers, but also contribute to a wider range, but not an overall increased incidence, of adverse effects. The drug is effective and well-tolerated in patients with all grades of hypertension, but is of particular value in special subgroups such as Black patients, the elderly and patients with renal hypertension. While comparative studies are not extensive, available data show that the drug reduces blood pressure to a similar extent, and in a similar proportion of patients, as 'pure' beta-blockers such as propranolol, pure alpha-blockers such as prazosin, calcium antagonists (nifedipine, verapamil), and centrally acting drugs (clonidine and methyldopa). Labetalol is very effective in hypertensive pregnant women and in hypertensive crises, where it provides good control of blood pressure without serious adverse effects, and where few therapeutic options exist. Few controlled studies have investigated the use of labetalol in deliberate induction of hypotension or prevention of hypertension during anaesthesia, and also in patients with ischaemic heart disease. However, available evidence suggests a role for labetalol in these indications and further studies should aid in clarification of its efficacy in these areas. Thus, with its broad scope of therapeutic use in hypertension labetalol remains an important therapeutic option, and the drug may well find an additional place in the treatment of myocardial ischaemia if further evidence confirms encouraging preliminary findings.

Pregnancy in organ transplant recipients

Pregnancy in women who are renal transplant recipients carries risks of hypertension and worsening of renal function for the mother and risks of prematurity, growth retardation, and infection in the infant. The risks for mother and child are greater if the transplant recipient has moderate renal insufficiency or hypertension prior to conception; even in patients with moderate renal insufficiency, birth of a viable infant is the rule. Pregnancy should not be discouraged in renal transplant recipients, but both mother and fetus should be carefully followed through the pregnancy and neonatal period. The restoration of fertility should be included as a benefit of transplant in discussions with young women deciding between dialysis and transplant for treatment of renal failure.

The use of labetalol for attenuation of the hypertensive response to endotracheal intubation in preeclampsia

Twenty-five women with preeclampsia who were scheduled to undergo cesarean section under general anesthesia were randomly assigned to either a labetalol pretreatment group (n = 15) or a control group (n = 10) who did not receive any antihypertensive therapy before the induction of anesthesia. Patients in the labetalol group received 20 mg of labetalol intravenously followed by 10 mg increments up to a total dose of 1 mg/kg, which resulted in moderate reductions in the maternal mean arterial pressure and heart rate with attenuation of the hypertensive and tachycardiac responses to laryngoscopy and endotracheal intubation. In the labetalol group there was no excessive reduction in the mean arterial pressure with the use of isoflurane and the usual amount of blood loss that occurred during cesarean section. The neonatal Apgar scores and umbilical arterial and venous pH and blood gas values were similar in the two groups. Side effects such as hypotension, bradycardia, and hypoglycemia were not seen in the neonates in the labetalol treatment group.

Comparison of antihypertensive efficacy and perinatal safety of labetalol and methyldopa in the treatment of hypertension in pregnancy: a randomized controlled trial

Labetalol was compared with methyldopa in a randomized controlled trial involving 176 pregnant women with mild to moderate hypertension. Diastolic blood pressure below 86 mmHg was obtained in a similar proportion of women given labetalol or methyldopa. Intrauterine death occurred in four women treated with methyldopa, and the one neonatal death on day 1 occurred in the labetalol group. The average birthweight and the proportion of preterm or small-for-gestational-age babies were similar in both groups. Heart rate, blood pressure, blood glucose, respiratory rate, and Silverman score of the babies did not differ between the two treatment groups, whether the comparison was made for all the infants, or only for those that were preterm or small-for-gestational-age. These data indicate that maternal beta-blockade with labetalol is as safe as methyldopa for the fetus and the newborn.

Fetal aortic blood flow and echocardiographic findings in human pregnancy

Relationships between human fetal aortic blood flow parameters and the corresponding echocardiographic findings were investigated in 51 normal, 26 hypertensive and 18 diabetic late pregnancies. In the normal pregnancies the time-averaged mean and peak velocities and the waveform indexes of the flow in the fetal aorta were not dependent on the cardiac size nor on the fractional shortening of the myocardium. Total blood flow in the aorta correlated well with heart size and left ventricular output. Hypertensive cases had, as a group, lower aortic velocities and higher waveform indexes than normal and diabetic pregnancies, and the difference from normal was particularly great if the fetus was growth-retarded. Myocardial contractility in these fetuses remained good in spite of these peripheric hemodynamic alterations, but the relative size of the right ventricle was increased. The diabetic cases had smaller blood flow volume in fetal aorta than in the normal cases. In contrast with normal pregnancies the myocardial fractional shortening of these fetuses decreased if the pulsatility of the aortic blood flow increased or the total blood flow in the aorta was high. These findings point to a decreased functional capacity of the fetal heart in a diabetic pregnancy, in particular in the late weeks of gestation.