Central hemodynamic assessment of normal term pregnancy

The effects of pregnancy on the cardiovascular response to acute systemic isocapnic hypoxia in conscious sheep

OBJECTIVE

This study tested the hypothesis that pregnancy affects the cardiovascular responses to hypoxia by altering the outputs of the peripheral components of the stress system and independent of changes in P(a)CO(2).

DESIGN

Comparison of cardiovascular and endocrine responses to acute isocapnic hypoxia between pregnant and non-pregnant ewes.

SETTING

Experimental laboratory.

SAMPLE

Fifteen pregnant (118 days of gestation; term is ca. 145 days) and 8 non-pregnant sheep.

METHODS

Chronically instrumented pregnant and non-pregnant ewes were subjected to 1 hour normoxia, 1 hour of acute systemic isocapnic hypoxia and 1 hour recovery.

MAIN OUTCOME MEASURES

Arterial blood pressure, heart rate, femoral blood flow and femoral vascular conductance were recorded continuously throughout and arterial blood samples were taken during normoxia, hypoxia and recovery for the measurement of blood gas, metabolic and endocrine status.

RESULTS

Basal blood pressure and blood glucose and lactate concentrations were lower in pregnant animals (P < 0.05). In contrast, basal cardiovascular variables and plasma concentrations of noradrenaline, adrenaline, neuropeptide Y, adrenocorticotropic hormone (ACTH) and cortisol were similar in pregnant and non-pregnant ewes. During hypoxia similar reductions in P(a)O(2) occurred in pregnant and non-pregnant animals, without alterations in P(a)CO(2) or pH(a). In non-pregnant ewes, acute hypoxia induced a transient increase in arterial pressure and sustained tachycardia without significant changes in femoral haemodynamics. Pregnancy attenuated the cardiovascular response, significantly diminishing the magnitude of the increment in heart rate throughout the hypoxic challenge (P < 0.001). However, hypoxia did not induce significant changes in blood metabolites or in plasma concentrations of any stress hormone measured in either pregnant or non-pregnant animals.

CONCLUSION

Pregnancy not only affects basal but also stimulated cardiovascular function in the mother. The diminished chronotropic response to hypoxia in pregnancy is mediated via mechanisms independent of changes in P(a)CO(2) or in plasma concentrations of hormones or metabolites associated with activation of the stress system.

Perianesthesia care following obstetric emergencies at risk for multisystem organ dysfunction

Perianesthesia care provided to obstetric patients is on the rise due to current obstetric practice habits, changes in the maternal population, and the increased desire for scheduled childbirth. Both scheduled and emergent cesarean deliveries create risk, yet the use of general anesthesia increases maternal morbidity and mortality significantly. Obstetric emergencies make up the majority of emergent cesarean deliveries. Detrimental events during pregnancy and childbirth may be categorized into hemorrhagic, septic, or anaphylactic shock. Excessive loss of circulating volume with subsequent loss in oxygenation creates an environment for multisystem organ dysfunction syndrome (MODS). Both MODS and pregnancy are hyperdynamic and hypermetabolic states. Close monitoring is needed to differentiate pregnancy for the progression of organ dysfunction. Caring for pregnant women with the intent that pregnancy is a normal, physiologic state can lead to complacency and the risk of misdiagnosis. The purpose of this article is to review current obstetric emergencies that place the obstetric population at risk for MODS and offer management options to perianesthesia providers.

Physiology of normal pregnancy

The pregnant patient in the intensive care unit (ICU) poses many challenges. Physicians and nurses need to understand the basic concepts of maternal physiology and fetal physiology. The physicians must care for the mother and consider the potential adverse effects that diagnostic and therapeutic interventions might have on the fetus. This article focuses primarily on the normal pregnant state with appropriate references to how pregnancy may affect the patient in specific circumstances relating to the ICU. The physiologic adaptation of the major organs to the pregnant state should be familiar to ICU physicians.

Pathophysiology of pre-eclampsia: update on the role of nitric oxide

Women with chronic hypertension and pregnancy-induced hypertension are at substantial risk for developing pre-eclampsia/eclampsia, a disease with high fetomaternal morbidity and mortality. However, the etiology of this disease is still unknown. In this article, recent concepts on the pathophysiology of pre-eclampsia, with special attention to the role of nitric oxide, are reviewed.

Pregnancy and lactation

Pregnancy results in physiologic changes in almost all organ systems in the body mediated mainly by female sex hormones. Physiologic changes of pregnancy influence the dental management of women during pregnancy. Understanding these normal changes is essential for providing quality care for pregnant women. This review article briefly discusses the cardiovascular, respiratory, gastrointestinal, urogenital, endocrine, and oral physiologic changes that occur during normal gestation. A summary of current scientific knowledge of ionizing radiation is presented. Information about the compatibility, complications, and excretion of the common drugs during pregnancy is provided. Drugs and their usage during breast-feeding are also discussed. Guidelines for the management of a pregnant patient in the dental office are summarized.

Plasma volume and blood pressure regulation in hypertensive pregnancy

BACKGROUND

Pre-eclampsia is a multisystem disorder, peculiar to and frequent in human pregnancy. It remains a leading cause of maternal and neonatal morbidity and mortality. Hemodynamic disturbances are the most prominent features of the syndrome.

PURPOSE

To provide an overview of plasma volume regulation and blood pressure control mechanisms outside pregnancy, and of the changes in normal pregnancies and in pregnancies complicated by hypertensive disorders. Furthermore, to discuss the rationale of several hemodynamic interventions.

RESULTS

In normal pregnancy, large cardiovascular changes take place. A generalized fall in vascular tone by systemic vasorelaxation causes increased blood volume, heart rate and cardiac output. In the preclinical phase, differences have been observed between normal and hypertensive pregnancies in the function of the autonomic nervous system, cardiac output and plasma volume, the volume remaining at the non-pregnant level. In the clinical phase of pre-eclampsia the typical case picture is one of a vasoconstrictive state with low plasma volume and cardiac output, high blood pressure and systemic vascular resistance in combination with signs of organ damage [proteinuria, hemolysis elevated liver enzymes low platelets (HELLP) syndrome]. Hemodynamic management is necessary in severe disease to prevent maternal complications. Management primarily focuses on pharmacological treatment of blood pressure. Clinicians make educated choices from a limited array of available drugs: beta-receptor antagonists, nifedipine, dihydralazine, methyldopa or ketanserine. Other drugs have restricted use in pregnancy. Management of low circulating volume with plasma expanders remains a subject of controversy.

Cardiac disease in pregnancy

This article reviews the complications, management and prognosis of cardiac disease in pregnancy.

Multiorgan dysfunction in the perinatal patient

MODS is a rare but potentially lethal complication of pregnancy. Pregnancy induces physiologic changes in all major maternal organ systems that mimic early changes seen in SIRS and MODS. When a potentially life-threatening event occurs, such as hemorrhage,sepsis, or severe preeclampsia, the perinatal nurse must monitor subtle changes in maternal and fetal status and intervene to optimize maternal status.

Thyrotoxicosis and heart failure that complicate pregnancy

OBJECTIVE

When untreated, Graves' thyrotoxicosis has profound cardiovascular effects, although it rarely causes heart failure in otherwise healthy patients. Preliminary observations suggest that pregnant women are the exception. To further elucidate this association, we studied both immediate and long-term outcomes in women who had thyrotoxicosis and heart failure during pregnancy.

STUDY DESIGN

We reviewed clinical outcomes of pregnant women with Graves' disease and heart failure at our institution from 1974 through 2001. Women with other underlying heart disease were excluded. A standardized antithyroid regimen and serial echocardiography and/or chest radiography were performed.

RESULTS

The 13 women with thyrotoxicosis and heart failure were either noncompliant with antithyroid therapy or had no medical care during pregnancy. Six women had heart failure before fetal viability; decompensation was precipitated by hemorrhage, sepsis, or both. The other 7 women were in the last trimester when heart failure developed; in 4 women, the heart failure was precipitated by severe preeclampsia-eclampsia and in 2 women was precipitated by sepsis. Overall, 11 of 13 women had an underlying obstetric event. In follow-up of 11 women from 2 to 25 years, resolution of cardiomyopathy was confirmed after successful treatment of thyrotoxicosis.

CONCLUSION

Normal pregnancy mimics and amplifies some of the hyperdynamic cardiovascular changes that are caused by thyrotoxicosis. When they occur simultaneously, there is usually a compensated high-output state. In some women, however, common pregnancy complications that include hemorrhage with associated anemia, sepsis, and severe preeclampsia-eclampsia will precipitate heart failure. The immediate treatment of heart failure and the correction of precipitating pregnancy factors usually results in good outcome. Long-term follow-up confirmed that thyrotoxic cardiac dysfunction is reversible with successful antithyroid therapy.

Resultados perinatológicos del servicio de Cardiopatía y Embarazo del Hospital Ginecobstétrico "Ramón González Coro" en el bienio 2000-2001, Habana

OBJETIVOS: establecer las bases para el tratamiento y atención de la mujer portadora de cardiopatía en edad fértil, caracterizando al grupo de gestantes atendidas en servicio. MÉTODOS: realizó un estudio descriptivo y las mujeres fueran clasificadas según cardiopatía y grado de afectación funcional en relación con los resultados, se decribiendo las complicaciones durante el embarazo, parto y puerperio y los resultados perinatales. Variables analizadas: tipo de cardiopatía y clasificación funcional de las mismas, complicaciones obstétricas y/o cardiovasculares, edad gestacional al parto, modo de nacimiento, peso y puntaje de Apgar en el recién nacido y mortalidad materna y del recién nacido. RESULTADOS: encontramos 129 valvulopatías adquiridas, 79 congénitas, 18 casos de trastornos del ritmo. Lesiones más frecuentes valvulopatías mitrales (92) y comunicaciones interauriculares (31). 21 pacientes presentaron empeoramiento funcional durante el embarazo. Aparecieron complicaciones cardiovasculares en 19 pacientes y obstétricas en 142. 14 requirieron ingreso en Servicios de Terapia Intensiva y tres fallecieron. CONCLUSIONES: Se confirmó la asociación entre clasificación funcional y complicaciones cardiovasculares durante el embarazo, parto y puerperio. Las complicaciones obstétricas se comportan igual que en las gestaciones de pacientes sanas y más de la mitad de los partos fueron eutócicos.

Pre-eclampsia: fluids, drugs, and anesthetic management

Severe pre-eclampsia is a complex disease, which taxes the expertise of even the most experienced obstetric anesthesiologist. The treatment should focus on stabilization of blood pressure, optimization of fluid status, and prevention of convulsions. Neuraxial blocks for labor and delivery offer many benefits to the mother and her infant. For cesarean section, there is unequivocal evidence of superiority of neuraxial anesthesia over general anesthesia. If general anesthesia is needed, careful preanesthetic preparation and meticulous airway management is essential. The successful and safe peripartum management of the pre-eclamptic patient and her infant is a team effort among the anesthesiologist, obstetrician, and neonatologist.

Critical care obstetrics and gynecology

The critical care aspects of obstetrics and pregnancy are varied and demand that critical care practitioners have a thorough knowledge of fetal and maternal changes in physiology as pregnancy progresses. Pregnancy can affect every organ system; and organ-specific conditions as well as syndromes that span multiple organ systems were described. Care of the critically ill, pregnant patient requires a true multidisciplinary approach for optimal outcomes. A review of the current concepts and suggestions for therapy were presented.

Anesthesia for nonobstetric surgery in the pregnant patient

Each year over 75,000 pregnant women in the United States undergo nonobstetric surgery. The operations include those directly related to pregnancy, such as cerclage, those indirectly related to pregnancy, such as ovarian cystectomy, and those unrelated to gestation, such as appendectomy. When a pregnant woman presents for surgery, it is a stressful event for everyone involved. Issues about the surgical problem itself often seem secondary to maternal (and physician) concerns about the effect of surgery and anesthesia on the developing fetus, or the potential to trigger preterm labor. This article reviews the physiologic and anatomic changes that affect anesthetic care during pregnancy. The author also reviews the effects of anesthetic drugs and perioperative events on the fetus and on the pregnancy outcome. The relatively small number of published series are reviewed as well as the controversial recommendations regarding fetal and maternal monitoring during surgery.

Circadian rhythm of ANP, aldosterone and PRA in normotensive IUGR

OBJECTIVE

Atrial natriuretic peptide (ANP) increases are reported during normal pregnancy, but the relation to arterial pressure and the renin-angiotensin system is debatable. We assessed whether normotensive pregnancies with intrauterine growth retardation (IUGR) present an alteration of maternal ANP levels.

DESIGN

A total of 11 pregnant women with IUGR, in the absence of any other maternal or fetal pathology, entered the study during the third trimester. They were compared with 12 healthy pregnant women of similar age and characteristics. We monitored all subjects for blood pressure (BP), ANP, aldosterone and plasma renin activity (PRA), under the same conditions for 24 h. All subjects were submitted to the same regimen of life; with homogeneous dark : light periods, salt intake and meal times.

METHODS

BP was monitored at 20 min intervals for 24 h and blood tests performed at six time points during the 24 h. EDTA plasma samples were immediately centrifuged. Hormone assays were performed by radioimmunoassay. Koch's nonparametric two-way analysis of variance (ANOVA) was used to compare the hormone time-dependent profiles in the two groups. Circadian rhythms were assessed by cosinor analysis.

RESULTS

The IUGR group was characterized by higher ANP values compared to normal pregnancy, (205 +/- 24 versus 146 +/- 21 pg/ml: P < 0.05) but not significant differences were shown for PRA, aldosterone and BP circadian rhythms.

CONCLUSIONS

This study shows higher ANP values in human pregnancy complicated by IUGR, with presence of normal BP, aldosterone and PRA profiles.

Effects of pregnancy on specific diseases

Of the numerous physiological changes associated with pregnancy that may have effects on various diseases, the marked increase in blood volume probably exerts the most pronounced effect. This increase may affect the serum level of many medications, as well as affecting various laboratory tests. Other important changes occur in the renal and hepatic system, which in turn may affect the clearance and metabolism of certain drugs and medications. Moreover, the response to and treatment of various diseases during pregnancy may be affected by the "attitude" of the health care providers who are often reluctant to perform certain diagnostic tests and procedures on the pregnant woman.

Low dose combined spinal-epidural anaesthesia for caesarean section in a patient with peripartum cardiomyopathy

A patient with peripartum cardiomyopathy was scheduled for elective caesarean section after stabilization on medical therapy. Wer performed a combined spinal epidural using one ml 0.5% hyperbaric bupivacaine (5 mg) with 0.3 mg diamorphine for the spinal. The epidural was topped up with 10 mL bupivacaine 0.5%. Significant haemodynamic changes consisted of reduction in heart rate and hypotension after the spinal, and tachycardia after delivery. The benefits and risks of this approach are discussed.

Systemic hemodynamic changes in mansonic schistosomiasis with portal hypertension treated by azygoportal disconnection and splenectomy

OBJECTIVE

The aim of this study was to assess systemic hemodynamic changes in patients with Manson's schistosomiasis and portal hypertension during azygoportal disconnection and splenectomy.

METHODS

Sixteen patients with portal hypertension secondary to hepatosplenic schistosomiasis with indication for surgery were studied prospectively. All underwent invasive hemodynamic monitoring with pulmonary artery catheter. The first systemic hemodynamic assessment was performed preoperatively. In the intraoperative period new hemodynamic data were collected as follows: a) after laparotomy; b) 15-30 min after splenic artery ligature; c) 15-30 min after splenectomy; and d) after ligation of the collateral circulation.

RESULTS

The results indicated preoperatively that the patients presented with an increased cardiac index (4.40 +/- 0.94 L/min/m2) together with a reduction in the systemic vascular resistance index (1692.25 +/- 434.91 dyne.s/cm5.m2). The stroke index (53.74 +/- 10.40 ml/beat/m2) and both left (5.71 +/- 1.50 kg.m/m2) and right heart work indexes (1.12 +/- 0.74 kg.m/m2) were also elevated. The mean pulmonary artery pressure was increased (17.81 +/- 9.00 mm Hg) and the pulmonary vascular resistance index decreased (164.31 +/- 138.69 dyne.s/cm5.m2). From the moment that the splenic artery was ligated until the end of the procedure, the cardiac index (3.45 +/- 0.90 L/min/m2) was reduced and the systemic vascular resistance index (2059.50 +/- 590.05 dyne.s/cm5.m5) increased. The systolic index (44.25 +/- 11.01 ml/beat/m2) and the left ventricle work index (4.33 +/- 1.29 kg.m/m2) also reduced. The mean pulmonary artery pressure (19.18 +/- 9.21 mm Hg) and the right ventricle work index (0.94 +/- 0.62 mm Hg) remained elevated after the surgical procedure.

CONCLUSIONS

The data allowed us to conclude that hepatosplenic schistosomiasis induces a hyperdynamic circulatory state that was corrected after splenectomy and azygoportal disconnection, remaining a mild pulmonary hypertension. Therefore, these changes are correlated with the portosystemic collateral circulation, especially as a consequence of splanchnic hyperflow.

Maternal oxygen transport variables during the third trimester of normal pregnancy

OBJECTIVE

The aim of this study was to measure and calculate oxygen transport variables in uncomplicated term pregnancies.

STUDY DESIGN

Ten normotensive primiparous women between 36 and 38 weeks' gestation underwent pulmonary and radial arterial catheterization as part of a larger study. Seven women had studies repeated at approximately 12 weeks post partum. Measurements were made with patients in the left lateral recumbent position after a 30-minute stabilization period. Cardiac output was measured with the thermodilution technique. Blood samples were obtained simultaneously from the pulmonary and radial arteries and analyzed in duplicate for oxygen content with a blood gas analyzer.

RESULTS

The oxygen contents of both arterial and mixed venous blood are significantly lower (P <.05) in the third trimester of pregnancy (15.96 and 11.97 mL/dL, respectively) than in the postpartum period (18.00 and 13.54 mL/dL). The fall in oxygen content during pregnancy prevents any significant increase in oxygen delivery in the third trimester (867. 59 mL/min) relative to the postpartum period (806.50 mL/min, P not significant).

CONCLUSION

This is the first report of directly measured oxygen transport variables in healthy pregnant women.

Outcome of pregnancy in women with congenital heart disease

Improvements in diagnosis and surgical technique for correction have led to an increasing number of women with congenital heart disease reaching the child-bearing age. Pregnancy places considerable strain on the heart and circulation and necessitates marked cardiorespiratory adaptation. Today, with the exception of the Eisenmenger syndrome, there is no increased mortality associated with pregnancy in congenital heart disease. In contrast, there is still considerable morbidity, due to congestive heart failure, thromboembolic complications and disturbances of rhythm. Fetal outcome is complicated by a high rate of spontaneous abortions (20-25%), retardation of fetal growth, and premature delivery (almost 100% in cyanotic mothers). Based on an extensive review of the literature, we discuss the specific risks in pregnancy depending on the hemodynamic situations produced by different heart defects. We also discuss the risks and advantages of different regimens for anticoagulation. Counselling concerning contraception is frequently inadequate. The most important problems are thromboembolic complications with the use of hormonal contraception, and hyper- and dysmenorrhea in those using intrauterine devices. Finally, the genetic risks must be considered, differentiating between single gene defects and the sex of the parents suffering from congenital heart diseases.

Pulmonary edema in obstetric patients is rapidly resolved except in the presence of infection or of nitroglycerin tocolysis after open fetal surgery

OBJECTIVES

This study was designed to determine the etiology, course, and severity of pulmonary edema in obstetric patients in a tertiary care center.

STUDY DESIGN

A retrospective study was carried out on 16,810 deliveries from University of California, San Francisco, 1985-1995. Diagnosis and severity of lung injury were defined by a 4-point system that was based on the chest radiograph, oxygenation, positive end-expiratory pressure, and lung compliance. Resolution of pulmonary edema was defined by improvement in the chest radiograph and hypoxemia (ratio of arterial oxygen tension to inspired oxygen concentration) scores or by extubation.

RESULTS

Pulmonary edema developed in 86 patients, or 0.5% of all obstetric cases. It usually showed extensive air space consolidation on the chest radiograph and arterial hypoxemia. Although 43% of the patients had severe pulmonary dysfunction, the average time to resolution of pulmonary edema was 2.4 days. Only 45% of patients required admission to the intensive care unit and only 15% required intubation and positive-pressure ventilation. Patients with infection (mean of 7.2 days) or fetal surgery (mean of 3.8 days) had the most severe, protracted course.

CONCLUSION

Although obstetric pulmonary edema is associated with extensive radiographic infiltrates and severe hypoxemia, resolution occurs rapidly in most patients, limiting the need for intensive care support.

The sequential effects of estrogen administration and hypertension on cardiac function in ewes

OBJECTIVE

Our objective was to study the effect of estrogen administration and moderate hypertension on left ventricular size, pump function, and contractility in chronically instrumented ewes.

STUDY DESIGN

Ewes were either given 0.06 mg/kg 17beta-estradiol intramuscularly (n = 8) or were made hypertensive (n = 6) by inflation of an occluder around the aorta and were studied weekly. After 3 weeks each ewe received the opposite treatment.

RESULTS

Estrogen administration caused an increase in left ventricular chamber size at a given pressure, fractional shortening (21.9% +/- 2.9% to 28.5% +/- 3.7%), and stroke volume (1.4 +/- 0.3 mL/kg to 1.6 +/- 0.3 mL/kg). Subsequent hypertension further increased left ventricular size at a given pressure but decreased fractional shortening (20.0% +/- 4.4%) and stroke volume (1.3 +/- 0.3 mL/kg). With hypertension first, there was no left ventricular enlargement, even with subsequent estrogen administration, and there were no changes in left ventricular pump function. End-systolic pressure and stress-dimension relationships did not change with either treatment. The end-systolic wall stress-fractional shortening relationship was likewise unchanged, suggesting that neither treatment changed contractility.

CONCLUSIONS

The left ventricle previously exposed to hypertension does not remodel when exposed to estrogen, and cardiac pump function decreases when the estrogen enlarged heart is faced with moderate, subacute hypertension.

Enhanced Galphaq signaling: a common pathway mediates cardiac hypertrophy and apoptotic heart failure

Receptor-mediated Gq signaling promotes hypertrophic growth of cultured neonatal rat cardiac myocytes and is postulated to transduce in vivo cardiac pressure overload hypertrophy. Although initially compensatory, hypertrophy can proceed by unknown mechanisms to cardiac failure. We used adenoviral infection and transgenic overexpression of the alpha subunit of Gq to autonomously activate Gq signaling in cardiomyocytes. In cultured cardiac myocytes, overexpression of wild-type Galphaq resulted in hypertrophic growth. Strikingly, expression of a constitutively activated mutant of Galphaq, which further increased Gq signaling, produced initial hypertrophy, which rapidly progressed to apoptotic cardiomyocyte death. This paradigm was recapitulated during pregnancy in Galphaq overexpressing mice and in transgenic mice expressing high levels of wild-type Galphaq. The consequence of cardiomyocyte apoptosis was a transition from compensated hypertrophy to a rapidly progressive and lethal cardiomyopathy. Progression from hypertrophy to apoptosis in vitro and in vivo was coincident with activation of p38 and Jun kinases. These data suggest a mechanism in which moderate levels of Gq signaling stimulate cardiac hypertrophy whereas high level Gq activation results in cardiomyocyte apoptosis. The identification of a single biochemical stimulus regulating cardiomyocyte growth and death suggests a plausible mechanism for the progression of compensated hypertrophy to decompensated heart failure.

Enhanced vascular reactivity during inhibition of nitric oxide synthesis in pregnant rats

Pregnancy-induced hypertension has been suggested to be mediated by several mechanisms, including reduced nitric oxide (NO) synthesis. In this study, the effects of chronic treatment with the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) on blood pressure and the underlying changes in vascular reactivity were investigated in virgin and late-pregnancy Sprague-Dawley rats. The systolic blood pressure was 120+/-2, 124+/-5, 116+/-4, and 171+/-5 mm Hg in untreated virgin, virgin treated with L-NAME, untreated pregnant, and pregnant treated with L-NAME rats, respectively. The rats were killed, and the thoracic aorta was cut into strips for measurement of active stress in response to alpha1-adrenergic stimulation with phenylephrine and membrane depolarization by high KCl. In pregnant rats, the maximal active stress to phenylephrine (0.31+/-0.03 x 10(4) N/m2) and the high-KCl-induced active stress (0.55+/-0.09 x 10(4) N/m2) were smaller than those in virgin rats. By contrast, in the L-NAME-treated pregnant rats, the maximal phenylephrine-induced active stress (0.76+/-0.1 x 10(4) N/m2) was greater than that in virgin rats (0.52+/-0.1 x 10(4) N/m2), whereas the high-KCl-induced active stress (1.08+/-0.14 x 10(4) N/m2) was indistinguishable from that in virgin rats (1.03+/-0.14 x 10(4) N/m2). Treatment with L-NAME did not affect the phenylephrine-releasable Ca2+ stores in pregnant rats and had minimal effect on active stress in virgin rats. Thus, reduction of NO synthesis during late pregnancy is associated with a significant increase in blood pressure and vascular responsiveness to alpha-adrenergic stimulation, which can possibly be explained in part by enhanced Ca2+ entry from extracellular space. However, other mechanisms such as increased myofilament force sensitivity to Ca2+ and/or activation of a completely Ca2+-independent mechanism cannot be excluded.

Combined spinal epidural anaesthesia in a primigravida with valvular heart disease

PURPOSE

This is the first report describing combined spinal epidural anaesthesia for labour and unexpected Caesarean section in a patient with mitral and aortic stenosis and insufficiency.

CLINICAL FEATURES

The patient was a 30-yr-old GIPO with a history of rheumatic fever. She had moderate stenosis and insufficiency of the mitral and aortic valves. Combined spinal epidural anaesthesia was used throughout labour and subsequent Caesarean section. The patient remained haemodynamically stable throughout the procedure.

CONCLUSION

Carefully planned regional anaesthesia was safely used for labour and operative delivery in this parturient with mitral and aortic valvular disease.

Peripartum cardiomyopathy: a comprehensive review

The objective of this article is to review the etiology, diagnosis, treatment, prognosis, and natural history of peripartum cardiomyopathy. The English language medical literature was accessed though MEDLINE from 1966 to the present; additional sources were obtained by cross-referencing. Because of the limited number of studies and patients, metaanalysis could not be performed; however, the existing data regarding the etiology, diagnosis, treatment, and prognosis of peripartum cardiomyopathy are presented. Approximately 1000 U.S. women will have peripartum cardiomyopathy this year, and for many it will be fatal. The etiology of this disease remains uncertain, but current evidence suggests myocarditis of viral, autoimmune, or idiopathic origin. The utility of immunosuppressive therapy remains ambiguous; however, other advances in medical therapy for dilated cardiomyopathy and cardiac transplantation have significantly improved quality of life and survival for patients. As the initial patient contact, obstetricians and family practitioners must recognize this malady early and rapidly institute the proper medical therapy directed toward the congestive state.

Systemic hemodynamics and regional blood flow during chronic nitric oxide synthesis inhibition in pregnant rats

Pregnancy-induced hypertension in women is associated with severe vasoconstriction and reductions in organ blood flow and cardiac output. Recent studies have indicated that nitric oxide (NO) synthesis inhibition during mid to late gestation in pregnant rats results in severe hypertension and proteinuria. The purpose of this study was to determine the systemic hemodynamic and regional blood flow alterations associated with chronic NO synthesis inhibition in the pregnant rat. The study was conducted in four groups of rats: virgin rats (n=6), pregnant rats (n=10), virgin rats treated with L-NAME (n=6), and pregnant rats treated with L-NAME (n=11). Rats were treated with L-NAME in drinking water at a dose of 1 mg/d for a week starting from day 13 of gestation in pregnant rats or an equivalent time for virgins. Mean arterial pressure (MAP), cardiac output, total peripheral resistance (TPR), and regional flows were measured by tracing radiolabeled microspheres in conscious rats. Pregnant rats that were given L-NAME showed significantly higher MAP (137+/-6 versus 96+/-2 mm Hg), higher TPR (5.08+/-0.58 versus 2.90+/-0.44 mm Hg/mL/min/100 g), and lower cardiac output (87.4+/-8.4 versus 113.3+/-11.1 mL/min) than pregnant controls. Chronic NO synthesis inhibition decreased the renal blood flow in pregnant rats at a significantly greater magnitude than in virgin rats. Significant reductions in regional blood flow to the heart, lungs, liver, diaphragm, and skeletal muscles were also observed in pregnant rats treated with L-NAME. The results of this study indicate that NO may play a role in mediating the alterations in systemic hemodynamics and regional blood flow in late pregnant rats.

Pregnancy and heart disease: a review

About one per cent of all pregnancies are affected by maternal heart disease, which may have significant influence on the maternal and foetal outcome. In this context rheumatic heart disease is declining and congenital heart disease is becoming the dominant category. Our experience of pregnancy in the new groups of patients created by paediatric heart surgery is scant and a continuous update is required.

Modeling obstetric cardiovascular physiology on a full-scale patient simulator

To our knowledge, this is the first attempt at adapting an existing cardiovascular model to simulate the hemodynamics of a particular patient population. Despite attempts to define the physiologic alterations in advance, we discovered there were critical parameters not completely defined in the literature. These were discovered through the iterative process of testing, comparing resulting vital signs with targets, and literature review. A list of the parameters that should be sought for future modeling efforts is provided (Table 3), but this list is by no means exhaustive. As further work is performed in this area, additional independent and essential parameters will be identified (pressure characteristics of valvular anomalies, for example). To define a physiology that is less well described in the literature, empirical alterations and best-guess estimates of parameter changes will be required with significantly more iterations. Finally, we have described only modeling of cardiovascular physiology, modeling the respiratory system will require a similar process.

Cardio-respiratory physiological adaptation of pregnancy

Significant physiological adaptations during pregnancy contribute to its successful outcome. These occur early in the pregnancy and continue throughout gestation, with complete reversal after delivery. Many changes that are normal during pregnancy are pathological should they occur in the nonpregnant woman. Adequate understanding of these normal changes is essential in the assessment of all pregnancies and in the management of those with complications. This article reviews the cardiovascular and pulmonary changes that occur during a normal gestation.

Adult respiratory distress syndrome in pregnancy: report of three cases and review of the literature

Adult respiratory distress syndrome (ARDS) is rarely encountered in association with pregnancy, but with the decline in other causes of maternal death, is an increasingly important cause of mortality in obstetric patients. ARDS may result from a variety of different types of pulmonary injury; uniquely obstetric causes include preeclampsia, amnionitis-endometritis, obstetric hemorrhage, and tocolytic therapy. Crucial management issues include support of maternal oxygenation and cardiac output, myriad interactions between the pulmonary process and its treatment, with maternal and fetal physiology, and decision making regarding delivery. Our review of the literature suggests that, for the patient requiring antepartum intubation for ARDS, except at a very early gestational age or when pyelonephritis or varicella pneumonia is a cause of respiratory compromise, delivery will likely be required for maternal and/or fetal indications, and an early decision for delivery may be beneficial. Postpartum management is similar to treatment of the nonpregnant patient with ARDS, with aggressive attention to potential surgically correctable causes for infection. Maternal mortality rates are affected little by duration of intubation, and therefore prolonged mechanical ventilation is justified and appropriate for mothers with ARDS.

Effects of physiologic load of pregnancy on left ventricular contractility and remodeling

Left ventricular (LV) adaptation to the hemodynamic load of pregnancy has been studied with load-sensitive ejection-phase indexes, but the results of these studies are conflicting. The aim of this study was to examine the effects of the hemodynamic load of pregnancy on the contractile state of the left ventricle by using load-adjusted indexes of contractility. Thirty-four healthy women were prospectively studied by serial echo and Doppler examinations at six periods during pregnancy and after delivery. LV volume increased 10.5%, paralleling the change in stroke volume. End-systolic stress, an index of myocardial afterload, decreased 28.8% because of a decrease in end-systolic pressure and an increase in LV thickness/diameter ratio. Despite the increase in preload and the decrease in afterload, ejection phase indexes did not change during or after pregnancy. Although remaining within the normal range, the afterload-adjusted velocity of circumferential fiber shortening, an index of contractility that is relatively insensitive to preload, transiently decreased by 1.75 SDs during gestation, returning to non-pregnant values 2 to 4 weeks postpartum. Thus the increase in hemodynamic load that characterizes normal pregnancy is associated with preservation of global pump function. The transient decrease in contractile state may represent an adaptation phase of the contractile elements of the myocardium to the rapid changes in loading conditions observed during the first trimester of pregnancy.

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.