David B. Cotton

Hemodynamic profile of severe pregnancy-induced hypertension

Cases of severe pregnancy-induced hypertension or eclampsia were studied in forty-five women by catheterization of the right side of the heart to define the presenting hemodynamic profile associated with this disorder. These women could not be easily categorized into one specific hemodynamic pattern. Most patients had high-normal to elevated systemic vascular resistance indices (mean 2726 +/- 120 dynes.sec.cm-5.m2). The mean cardiac index was 4.14 +/- 0.13 L.min-1.m2. The severity of hypertension was largely attributable to a disproportionate rise in the systolic component (mean 193 +/- 3 mm Hg) compared with diastolic blood pressure (mean 110 +/- 3 mm Hg). Women with eclampsia had significantly lower arterial blood pressure and systemic vascular resistance indices when compared with those of the rest of the study group. Analysis of Starling curves indicated that all patients had normal or hyperdynamic left ventricular function. A modest correlation was observed between central venous pressure and pulmonary capillary wedge pressure (r = 0.59). This disparity most likely results from the maintenance of normal to high cardiac output in the presence of an increased left ventricular afterload. The majority of patients with severe pregnancy-induced hypertension do have normal to high cardiac indices and pulmonary capillary wedge pressures accompanied by normal or hyperdynamic left ventricular function. This is true despite the presence of severe hypertension.

Clinical indications for pulmonary artery catheterization in the patient with severe preeclampsia

The obstetric literature reflects an increased interest in invasive hemodynamic monitoring during the past decade. While much of this interest has focused on research applications, the patient with severe preeclampsia may benefit clinically from pulmonary artery catheterization under several circumstances. These conditions include severe hypertension unresponsive to conventional antihypertensive therapy, pulmonary edema, persistent oliguria unresponsive to fluid challenge, and in induction of conduction anesthesia in select patients. Theoretical and clinical evidence to support this contention is presented.

Squamous and trophoblastic cells in the maternal pulmonary circulation identified by invasive hemodynamic monitoring during the peripartum period

The antemortem diagnosis of amniotic fluid embolism has traditionally relied on the identification of amniotic fluid debris in the maternal circulation by central venous or pulmonary arterial catheterization. Pulmonary artery blood specimens from 14 term pregnant women with severe pregnancy-induced hypertension suggest that squamous or trophoblastic cells may be normally present in the maternal pulmonary circulation during the peripartum period and that their presence is not pathognomonic of clinically significant amniotic fluid embolism.

Doppler assessment of the fetal and uteroplacental circulation during nifedipine therapy for preterm labor

To investigate the effects of nifedipine on the human fetal circulation, 11 fetuses whose mothers were treated with nifedipine for treatment of preterm labor were studied. Maximum velocity waveforms were obtained in the middle cerebral artery ( n = 8), renal artery ( n = 6), ductus arteriosus ( n = 8), and umbilical artery ( n = 10). Transvalvular maximal velocity waveforms were obtained across the aortic ( n = 11) and pulmonary ( n = 7) valves. Maternal uterine arteries also were studied ( n = 7). Doppler data were collected before and 5 hours after nifedipine therapy. Patients received an oral loading dose of 30 mg of nifedipine followed by a second oral dose of 20 mg 4 hours later. No significant difference in the flow velocity waveforms was found in the vessels studied 5 hours after the initial dose. These results suggest that short-term nifedipine therapy does not influence either fetal or uteroplacental circulation as evaluated with the Doppler technique.

Septic shock during pregnancy

A multiinstitutional review of 10 pregnancies complicated by septic shock was undertaken to identify the clinical characteristics and hemodynamic alterations associated with this condition. Prolonged rupture of membranes with the subsequent development of chorioamnionitis or postpartum endometritis were risk factors that commonly preceded the diagnosis of septic shock. The majority of septic shock cases occurred during the puerperium. There were two maternal deaths in this selected series. Associated complications included pulmonary edema, adult respiratory distress syndrome, disseminated intravascular coagulation, pulmonary emboli, and cardiac arrest. The primary hemodynamic derangements were reduced systemic vascular resistance with depressed myocardial function. The mean initial systemic vascular resistance index in eight surviving women was 885 ± 253 dyne · sec/cm 5 · m 2 . Despite an overall presenting cardiac index of 4.20 ± 2.01 L/min/m 2 , five patients (50%) had evidence of myocardial depression based on analysis of their left ventricular function curves. Mean arterial pressure, systemic vascular resistance, and left ventricular stroke work index all showed significant improvement after therapy. A hemodynamic algorithm based on volume therapy, inotropic agents, and peripheral vasoconstrictors is offered. This therapeutic approach is designed to optimize cardiac performance and maintenance of organ perfusion in the critically ill patient with septic hypotension during pregnancy.

Cardiovascular alterations in severe pregnancy-induced hypertension: Relationship of central venous pressure to pulmonary capillary wedge pressure

The relationship between central venous pressure and pulmonary capillary wedge pressure was studied in 18 patients with severe pregnancy-induced hypertension. Although statistically a linear relationship for the group as a whole could be identified, analysis on a case-by-case basis revealed different results. In 10 patients, a linear correlation between central venous pressure and pulmonary capillary wedge pressure was observed. However, accurate prediction of pulmonary capillary wedge pressure from central venous pressure was not possible even in this group because of large interindividual variations. In seven patients no correlation between central venous pressure and pulmonary capillary wedge pressure could be identified. In the last patient a curvilinear relationship existed between central venous pressure and pulmonary capillary wedge pressure. Additionally, in five cases of pulmonary edema, a negative gradient of colloid osmotic pressure to pulmonary capillary wedge pressure gradient was observed. Our data suggest that central venous pressure is not a clinically reliable predictor of pulmonary capillary wedge pressure.

Effects of maternal aerobic fitness on cardiorespiratory responses to exercise.

We hypothesized that aerobically fit women who continued to exercise throughout pregnancy would have enhanced cardiorespiratory responses to exercise. Physically active (N = 10) and sedentary (N = 6) subjects were compared during steady-state (15 min) semi-recumbent cycle exercise performed at a given heart rate (HR; 140 b.min-1) twice during pregnancy (25 wk, 36 wk) and 12 wk postpartum. Indirect calorimetry was used to measure volumes and fractional concentrations of expired gases. Cardiac output was estimated via CO2 rebreathing. Data were analyzed with repeated measures ANOVA. Caloric expenditure during exercise was significantly (P < 0.001) greater in the physically active (7.2 kcal.min-1) compared with sedentary (4.7 kcal.min-1) subjects. Alveolar ventilation and cardiac output responses to exercise were proportionally greater (P < 0.001) in the aerobically fit subjects. Ventilatory equivalents for O2 and physiological dead space/tidal volume ratios were significantly (P < 0.01) lower in the physically active subjects during exercise. In contrast, ratings of perceived exertion during exercise did not differ between subject groups. It appears that a physically active womans enhanced cardiorespiratory responses to acute exercise are maintained during pregnancy if she continues her aerobic fitness program throughout gestation.

Noninvasive maternal stroke volume and cardiac output determinations by pulsed Doppler echocardiography

Sixteen obstetric patients with pulmonary artery catheters were studied by two-dimensional and pulsed Doppler echocardiography to compare prospectively pulsed Doppler-and thermodilution-derived estimations of left ventricular stroke volume and cardiac output. Systolic aortic flow velocity waveforms were obtained by pulsed Doppler ultrasound from the apical five-chamber echocardiographic window. Aortic diameters were obtained by two-dimensional echocardiography from the left parasternal long axis view. The mean (+/- SEM) aortic diameter averaged 2.1 +/- 0.1 cm, with a mean calculated aortic valve area of 3.6 +/- 0.2 cm2. The mean aortic flow velocity integral was 21.8 +/- 0.8 cm. This information was used to calculate aortic stroke volume and cardiac output. Thermodilution- and Doppler-derived estimations for maternal stroke volume (r = 0.86) and cardiac output (r = 0.94) were significantly correlated when aortic diameter measurements based on a leading vessel edge method were used. Our findings verify the accuracy of an important noninvasive technique for quantitating maternal stroke volume and cardiac output by pulsed Doppler echocardiography. This methodology should provide an alternative approach to invasive monitoring in the study of normal and abnormal maternal circulatory hemodynamics.

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

Central hemodynamic and renal responses to low-dose dopamine (1 to 5 micrograms/kg/min) infusion were studied in six oliguric (less than 0.5 ml/kg/hr) patients with severe preeclampsia. Hemodynamic parameters were measured and renal function tests were done before and during therapy. There was a significant rise in urine output from a mean (+/- SD) of 21 +/- 10 to 43 +/- 23 ml/hr, accompanied by a rise in cardiac output from 6.8 +/- 1.8 to 8.0 +/- 2.3 L/min (p less than or equal to 0.05). There were no significant changes in blood pressure, central venous pressure, or pulmonary capillary wedge pressure. The fractional excretion of sodium, negative free water clearance, and osmolar clearance tended to rise during dopamine therapy. No adverse maternal or fetal effects occurred. We conclude that low-dose dopamine produces a significant increase in urine production with resolution of oliguria in severe preeclampsia.

Unknown uterine scar and trial of labor.

A review of 393 patients undergoing trial of labor after one or more previous cesarean sections was performed. Three hundred patients had an unknown uterine scar, 88 patients had a documented low cervical transverse incision, and five patients had a prior low vertical incision. The rate of vaginal delivery and maternal and fetal morbidity was no different in those patients with an unknown prior uterine incision compared with those having a known prior low cervical transverse incision. In 66 of the patients with a documented low cervical transverse incision, the original operative record was reviewed in regard to single-layer closure of the uterine incision versus double-layer closure or imbricating technique. No patient with a double-layer uterine closure had a subsequent dehiscence, whereas three patients with a prior single-layer closure exhibited scar separation. These data suggest that neither an unknown scar nor a single-layer uterine closure places the mother or fetus at greater risk.