Effects of low-dose dopamine therapy in the oliguric patient with preeclampsia

Fluid management in pre-eclampsia

Intravenous fluid given to women with pre-eclampsia may be a necessary form of treatment; however, intravenous fluid therapy can also cause iatrogenic pulmonary oedema. The indications for the use of intravenous fluids, the titration of the amount of fluid given and the use of invasive monitoring have not been subject to adequate examination in randomised studies. Clinical experience, combined with available evidence and a reasoned approach are the basis for a suggested management algorithm.

Critical care management of severe pre-eclampsia

Severe pre-eclampsia is a common disorder in developing countries but still remains a significant problem in developed societies. The management of severe pre-eclampsia in developing countries is frequently hampered by lack of adequate facilities; paradoxically those countries with sufficient resources have a lower incidence of the disease and consequently lack experience in the treatment of severe pre-eclampsia. The management of these patients is further compromised because obstetricians generally lack the necessary knowledge and skills in critical care and conversely critical care specialists may lack appreciation and knowledge of pregnancy physiology and pathophysiology. Patients with severe pre-eclampsia therefore present an interdisciplinary challenge to obstetricians and physicians, who need to be familiar with pregnancy physiology and the current concepts in the pathogenesis and pathophysiology of severe pre-eclampsia. Patients who develop multisystem disease are most appropriately managed by an experienced obstetrician in an obstetric intensive care unit with a physician in consultation.

Common problems in critically ill obstetric patients, with an emphasis on pharmacotherapy

Pharmacological treatment of critically ill obstetric patients can be especially challenging due to the complexity of caring for 2 patients, with a paucity of research to support practice. This review will provide practitioners with primary recommendations for management of the critical illnesses most commonly encountered in pregnancy and will discuss the scientific and clinical merit of these recommendations.

The vasodilatory effects of hydralazine, nicardipine, nitroglycerin, and fenoldopam in the human umbilical artery

We studied the effects of hydralazine, nicardipine, nitroglycerin, and fenoldopam (a dopamine D1-agonist) on isolated human umbilical arteries (HUA) from patients classified as normotensive and with pregnancy-induced hypertension (PIH). Umbilical artery rings were contracted with the thromboxane A(2) analog (U46619; 10(-8) M) and then exposed to cumulative concentrations of fenoldopam, hydralazine, nicardipine, and nitroglycerin. Second, rings were preexposed to prazosin (10(-5) M), phenoxybenzamine (10(-5) M), or none, and the constriction responses to increasing doses of fenoldopam or dopamine were recorded. Nitroglycerin, hydralazine, and nicardipine produced concentration-dependent relaxation of U46619-preconstricted HUA segments from normotensive and PIH patients. Fenoldopam and dopamine induced umbilical artery constriction in both normal and PIH rings at concentrations > or = 10(-5) M and > or = 10(-3) M, respectively. Phenoxybenzamine, but not prazosin, pretreatment irreversibly abolished fenoldopam-induced contraction. In this in vitro study, nitroglycerin was the most potent vasodilator of the HUA constricted with U46619, followed by nicardipine and hydralazine. However, fenoldopam constricted HUA rings only at supratherapeutic concentrations. No significant differences of vascular responses to fenoldopam (P = 0.3534), nitroglycerin (P = 0.7416), nicardipine (P = 0.0615), and hydralazine (P = 0.5514) between rings from normotensive or hypertensive pregnant patients were shown.

Pregnancy complicated with Bartter's syndrome: a case report

Bartter's syndrome is a rare renal disorder, and since there are few case reports of Bartter's syndrome complicating pregnancy are few, the changes of electrolytes and hormonal metabolism during pregnancy are unknown. We describe and discuss the course of pregnancy complicated with Bartter's syndrome.

Care of the critically ill parturient: oliguria and renal failure

The incidence of acute renal failure in pregnancy has decreased. This decrease is less marked in developing countries in which resources are more scarce. The clinical diagnosis of acute renal failure is crude due to the variability of clinical signs and the late occurrence of basic biochemical abnormalities. Obstetric and gynaecological diseases are found among the traditional pre-renal, intra-renal and post-renal causes of acute renal failure. The cornerstone of management is the identification of high-risk cases and the prevention of acute renal failure by maintaining intravascular volume. The evidence for the efficacy of other prophylactic medical interventions, such as the use of loop diuretics, mannitol, low-dose dopamine and others, is poor. Management of established acute renal failure includes restoration of intravascular volume, treatment of any reversible causes, especially pregnancy complications such as pre-eclampsia, strict fluid balance and correction of any electrolyte abnormality or metabolic acidosis. Dialysis is a supportive measure until the kidneys recover.

Low-dose "renal" dopamine

Low dose renal dopamine continues to be infused in patients at risk for renal dysfunction or as a therapy after acute renal failure has been established. This article reviews the impact of acute renal failure on patients and reviews the history and use of dopamine therapy for patients. A discussion of the rationale, positive and equivocal evidence, side effects, and possible clinical indications for low-dose renal dopamine therapy is included.

Fluid management in pre-eclampsia

We review the evidence base for fluid management in pre-eclampsia. Current understanding of the relevant pathophysiology and the possible impact of styles of fluid management on maternal and fetal outcome are presented. There is little evidence upon which to base the management of fluid balance in pre-eclampsia. Reports are conflicting and no large prospective outcome studies of fluid management have been performed. Volume expansion does not appear to reduce the incidence of fetal distress. Pulmonary oedema and oliguria receive particular attention. There is no evidence of long-term renal damage in pre-eclampsia, but there are strong suggestions that pulmonary oedema is linked to fluid administration. Monitoring is discussed and some principles of management are suggested

Low dose dopamine in postpartum pre-eclamptic women with oliguria: a double-blind, placebo controlled, randomised trial

OBJECTIVE

To assess the effect of low dose dopamine on the urine output in postpartum pre-eclamptic or eclamptic women with oliguria.

DESIGN

A double blind, randomised controlled study.

SETTING

The high care area of the labour ward in a teaching hospital.

SAMPLE

Forty postpartum pre-eclamptic women with oliguria, defined as < 30 mL/hour, who have not responded to a 300 mL crystalloid fluid challenge.

INTERVENTION

Dopamine was infused at a rate of 1 to 5 microg/kg per minute, or sterile water was given as placebo in the same dilution.

MAIN OUTCOME MEASURE

Urine output, blood pressure and pulse was measured for six hours before and for six hours after the intervention.

RESULTS

Women who received dopamine (344 mL over 6 hours) showed a clinically and statistically significant (P = 0.0014, Mann-Whitney U test) higher median urine output compared with those receiving placebo (135 mL over 6 hours) for the duration of therapy. The respective 95% confidence intervals were 212.3 to 712.7 mL compared with 73.8 to 244.7 mL. No differences in blood pressure or pulse were found between the two groups.

CONCLUSIONS

The use of low dose dopamine in a labour setting improved urine output in postpartum pre-eclamptic women with oliguria who had not responded to a single fluid challenge without a detrimental effect on the blood pressure or pulse.

Use of the pulmonary artery catheter in severe preeclampsia: a review

The use of a balloon-tipped, flow-directed pulmonary artery catheter in critically ill and surgical patients has become commonplace in the United States since its introduction into clinical medicine in 1970. The capability of acquiring continuous hemodynamic and, more recently, oxygen transport data, has led to an enhanced understanding of pathophysiologic processes in disease states and to an improved ability to guide therapeutic decision making. The purpose of this paper is to review experience with the pulmonary artery catheter in subsets of women with severe preeclampsia.

Is renal dose dopamine protective or therapeutic? Yes

In conclusion, dopamine has the unique ability, compared with other catecholamines, to improve renal blood flow, glomerular filtration rate, sodium excretion, and creatinine clearance, independent of its cardiac effects. In addition, low-dose dopamine can decrease renal and systemic vascular resistance, suppress aldosterone secretion, and interact with atrial natriuretic factor. Because of these clinically significant properties, dopamine has been used successfully to improve and treat acute oliguric renal failure in a variety of clinical situations as just described. In addition, there were no adverse or toxic cardiac effects, such as tachyarrhythmias or hypertension, detected with low-dose dopamine in studies reviewed for this publication. By increasing renal and mesenteric vasodilation, dopamine has been shown to be beneficial in preserving renal function in cardiac surgery, vascular surgery, liver transplantation, contrast-induced nephropathy, hypertension, and pediatric patients. A therapeutic renal effect has been observed in patients with hepatorenal syndrome or severe ovarian hyperstimulation syndrome, in patients requiring vasopressors and IABP, and in selected cases of acute oliguric renal failure and shock. Furthermore, the combination of low-dose dopamine with furosemide or prostaglandin results in enhanced renal effects. Further investigation is necessary to evaluate the important and specific therapeutic role of low-dose dopamine through prospective, randomized, double-blind studies. Until those data are available, the plethora of clinical evidence supporting the ability of low-dose dopamine to augment renal function continues to grow. For those who are skeptical, we offer the following suggestion: "The obscure we see eventually, the obvious takes a little longer"--E.R. Murrow.

Is renal dose dopamine protective or therapeutic? No

This article argues that dopamine infused in low doses has not been shown to avert the onset of or ameliorate the course of acute renal failure in critically ill patients. The inotropic and diuretic effects of dopamine are discussed, and its adverse effects are described. An attempt is made to offer an evidence-based role for low-dose dopamine, namely as a diuretic in ventilated, euvolemic patients, resistant to conventional diuretic therapy.

The oxygen consumption/oxygen delivery curve in severe preeclampsia: evidence for a fixed oxygen extraction state

OBJECTIVE

Increased total body oxygen consumption requirements are usually met by increased oxygen delivery and increased oxygen extraction. In certain conditions (e.g., adult respiratory distress syndrome) the ability to increase oxygen extraction is lost, and any increase in oxygen consumption depends on increased oxygen delivery. The objective of this study was to investigate the oxygen delivery/oxygen consumption relationship in severe preeclampsia.

STUDY DESIGN

Thirty-two patients with severe preeclampsia (blood pressure > 160/110 mm Hg; 3 to 4+ proteinuria) were monitored with a pulmonary artery catheter. Baseline oxygen consumption and delivery in a group without volume expansion or pharmacologic vasodilatation were compared with those in a group who had received a magnesium sulfate infusion.

RESULTS

Oxygen consumption, oxygen delivery, arterial-venous-oxygen difference, and the oxygen extraction ratio were low when compared to that for normal 32 to 38 week pregnancy. The oxygen extraction ratio, defined as the ratio of oxygen consumption to oxygen delivery, was abnormally low for pregnancy, especially considering the low oxygen delivery levels in these patients. Oxygen consumption was dependent on oxygen delivery over the entire range of values seen.

CONCLUSIONS

Severe preeclampsia is associated with an abnormality of tissue oxygen extraction, as evidenced by a low and unresponsive oxygen extraction ratio. Oxygen consumption increases proportionately with increases in oxygen delivery without reaching an oxygen delivery-independent state. Even at high oxygen delivery levels the oxygen consumption in preeclamptic patients is still abnormally low for pregnancy.