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Biomedical subjects

R H Beekman

Publications and source records attributed to R H Beekman.

121 records · Page 7Linked to original sources
PubMed1985

Acute hemodynamic effects of increasing hemoglobin concentration in children with a right to left ventricular shunt and relative anemia.

The short-term effects of increasing hemoglobin concentration were evaluated at cardiac catheterization in seven children (aged 0.3 to 7.5 years) with a right to left ventricular shunt and relative anemia. Diagnoses were tetralogy of Fallot in six and L-transposition of the great vessels with ventricular septal defect and pulmonary stenosis in one. Before and 20 minutes after isovolumic partial exchange transfusion with 20 ml/kg packed red cells, the following variables were measured: hemoglobin, partial pressure of oxygen (PO2), oxygen consumption, oxygen saturation and pressure in the aorta, superior vena cava and right and left atria. After partial exchange transfusion, hemoglobin increased from 13.7 +/- 0.5 to 16.4 +/- 0.4 g/100 ml (p less than 0.001, mean +/- SEM). Aortic PO2 increased from 55.0 +/- 3.5 to 62.0 +/- 4.1 mm Hg (p less than 0.01) and aortic oxygen saturation increased from 84.3 +/- 2.3 to 90.9 +/- 1.3% (p less than 0.002). Effective pulmonary blood flow increased by 17% from 2.72 +/- 0.10 to 3.17 +/- 0.10 liters/min per m2 (p less than 0.01), and right to left shunt decreased by 59% from 1.44 +/- 0.29 to 0.59 +/- 0.10 liters/min per m2 (p less than 0.01). Systemic oxygen transport increased from 658 +/- 48 to 738 +/- 46 ml/min per m2 (p less than 0.002). After partial exchange transfusion, systemic vascular resistance increased from 15.9 +/- 1.1 to 20.0 +/- 1.4 units (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1984

Vasodilator therapy in children: acute and chronic effects in children with left ventricular dysfunction or mitral regurgitation.

To determine the acute and chronic effects of vasodilator therapy in children, vasodilator therapy was evaluated in 13 children (aged 0.2 to 14.5 years) with severe left ventricular dysfunction or mitral regurgitation. In seven children, nitroprusside increased cardiac index by an average of 33% (P less than .01) and increased stroke index by 29% (P less than .01). In eight children, hydralazine caused a 31% increase in cardiac index (P less than .01) and a 27% increase in stroke index (P less than .02). Ten children received chronic oral vasodilator therapy and were followed for 5.7 +/- 1.4 (SEM) months. Early clinical improvement was observed in every child. Symptoms of heart failure diminished in all, and five children became entirely asymptomatic. A significant (P less than .05) improvement was noted in growth velocity, respiratory rate, heart size, and incidence of gallop rhythm after 1 month of therapy. The duration of the beneficial response to vasodilator therapy varied considerably, however, and significant improvement for the group was not found after 1 month. Four children had sustained clinical improvement for 6 months or longer, but the others experienced recurrent heart failure within 1 to 4 months.

Adolescent↗
PubMed1984

Validity of CO2-rebreathing cardiac output during rest and exercise in young adults.

To validate the CO2-rebreathing method ( Defare 's method) for estimating cardiac output in children and young adults, measurements were compared to thermodilution ( TDCO ) cardiac output in 16 subjects (age 7-19 yr) with congenital heart disease. Data were collected at rest (N = 11) and during 4-min stages of supine bicycle exercise (N = 13). Estimated arterial-venous (-v-a)CO2 content differences related linearly to the measured CO2 content difference (Y = 0. 29X + 2.47, r = 0.65, P less than 0.001). With this (v-a)CO2 difference correction for all patients (N = 16), the correlation between CO2-rebreathing cardiac output and the TDCO was r = 0.87 (SEE = +/- 1.8 l X min-1). The correlation was higher for exercise (r = 0.81) than for rest (r = 0.65). We conclude that the CO2-rebreathing method, with a (v-a)CO2 content difference adjustment, is a simple, noninvasive technique providing estimates of cardiac output in children and young adults with congenital heart disease. Individual estimates should be treated with caution, especially when used for clinical evaluations.

Adolescent↗
PubMed1983

Cardiovascular effects of breathing 95 percent oxygen in children with congenital heart disease.

The hemodynamic effects of breathing 95% oxygen were evaluated in 26 children with congenital heart disease. Aortic, pulmonary arterial, right atrial, and pulmonary arterial wedge pressure, aortic and pulmonary artery oxygen saturation, and blood gas, cardiac index, and heart rate were measured in room air and after each patient had breathed 95% oxygen for 10 (n = 26) and 20 (n = 5) minutes. Measurements were repeated with the patient again breathing room air for 10 (n = 11) and 20 (n = 6) minutes. After 10 minutes of 95% oxygen, arterial partial pressure of oxygen increased from 85 +/- 13 to 420 +/- 89 torr (p less than 0.001). Aortic mean pressure increased from 80 +/- 10 to 83 +/- 10 mm Hg (p less than 0.01), and systemic vascular resistance increased from 20 +/- 7 to 26 +/- 8 U (p less than 0.001). The cardiac index decreased by 21% from 3.96 +/- 0.94 to 3.12 +/- 0.74 liters/min/m2 (p less than 0.001) and the stroke index decreased by 11% (p less than 0.001). A 23% decrease in oxygen consumption (p less than 0.001) was observed, and oxygen transport decreased from 763 +/- 179 to 600 +/- 161 ml O2/min/m2 (p less than 0.001). Cardiac index, stroke index, and systemic vascular resistance did not return to normal until 20 minutes after cessation of oxygen breathing. To determine whether reflex bradycardia is responsible for these oxygen-induced hemodynamic changes, heart rate was kept constant by atrial pacing in a second group of 5 patients. In these children, significant decreases in cardiac index, stroke index, and oxygen consumption, and increases in systemic vascular resistance also occurred with 95% oxygen. Thus, in children with acyanotic congenital heart disease, hyperoxia increases aortic pressure and systemic vascular resistance and decreases cardiac index, stroke index, oxygen consumption, and oxygen transport.

Adolescent↗
PubMed1983

Altered baroreceptor function in children with systolic hypertension after coarctation repair.

To determine whether altered baroreceptor function may contribute to systemic hypertension after coarctation of the aorta (C of A) repair, baroreceptor function was evaluated in 6 children with repaired C of A mild arm systolic hypertension. Data were compared with those from 7 normotensive control children with hemodynamically mild heart disease. Age at C of A repair averaged 9.9 +/- 3.1 years (mean +/- standard deviation [SD]). Arm systolic pressure was 143.8 +/- 2.9 mm Hg in the C of A repair group, compared with 118.3 +/- 9.9 for control subjects (p less than 0.001). At catheterization, steady-state sigmoidal baroreceptor function curves relating mean arterial pressure to R-R interval were derived by increasing and decreasing mean arterial pressure with small injections of phenylephrine and nitroprusside. Compared with control subjects, the baroreceptor function curves of children with repaired C of A (1) are reset about a higher baseline mean arterial pressure (108.8 +/- 6.6 versus 90.3 +/- 8.6 mm Hg, p less than 0.01), (2) have a decreased slope (7.9 +/- 3.7 versus 17.4 +/- 3.6 ms/mm Hg, p less than 0.001), and (3) have a diminished R-R interval range (246.7 +/- 81.5 versus 535.7 +/- 97.2 ms, p less than 0.001). Thus, in children with hypertension after C of A repair, the baroreflex is reset to an elevated mean arterial pressure level and has a diminished sensitivity to changes in arterial pressure.

Adolescent↗
PubMed1982

Hemodynamic effects of hydralazine in infants with a large ventricular septal defect.

To evaluate the effects of acute afterload reduction, hydralazine, 0.2 mg/kg, was administered at cardiac catheterization to seven infants who had a large ventricular septal defect (VSD). The infants were 2.5 - 11 months old (mean 5.1 months). Before and 5, 15, 25 and 35 minutes after hydralazine, aortic, pulmonary capillary wedge, pulmonary artery, right atrial and superior vena caval pressures and saturations, heart rate and oxygen consumption were measured. Hemodynamic effects were noted after 5 minutes but were most pronounced 35 minutes after hydralazine. Prehydralazine baseline data were therefore compared with values 35 minutes after hydralazine. Pulmonary flow did not changes, but systemic flow increased significantly (4.5 +/- 0.2 to 6.7 +/- 0.5 liters/min/m2 [mean +/- SEM], p less than 0.001). The pulmonary-to-systemic flow ratio decreased by 32% (3.4 +/- 0.4 to 2.3 +/- 0.2, p less than 0.001) and the absolute left-to-right shunt decreased by 24% (10.8 +/- 1.3 to 8.2 +/- 1.2 liters/min/m2, p less than 0.01). Hydralazine caused a significant decrease in systemic resistance (13.9 +/- 0.7 to 9.5 +/- 0.7 U, p less than 0.001). Pulmonary resistance, aortic, pulmonary artery and pulmonary capillary wedge pressures, heart rate and oxygen consumption did not change after hydralazine. Right atrial pressure decreased slightly (4.0 +/- 0.6 to 2.4 +/- 0.6 mm Hg, p less than 0.05). In conclusion, hydralazine caused a significant increase in systemic blood flow and a significant decrease in both pulmonary-to-systemic flow ratio and absolute left-to-right shunt in seven infants with a large VSD. These effects appear to be related to the decrease in systemic resistance that occurred with hydralazine. Although limited to the acute setting, these findings suggest that hydralazine may be beneficial in the management of infants with a large VSD.

Blood Pressure↗
PubMed1981

Hemodynamic effects of nitroprusside in infants with a large ventricular septal defect.

To evaluate the effect of acute vasodilator therapy, nitroprusside was administered at cardiac catheterization to five infants (ages 10 days to 6 months) with isolated ventricular septal defect and congestive heart failure. Intravenous nitroprusside was begun at a dose of 0.5 micrograms/kg/min and was increased by increments of 0.5 micrograms/kg. Hemodynamic measurements were made before nitroprusside, after 5 minutes at each dose, and 10 minutes after nitroprusside was discontinued. Baseline data were obtained before nitroprusside administration and compared with data obtained at maximal nitroprusside dose. The pulmonary-to-systemic flow ratio increased from 2.2 +/- 0.2 to 3.4 +/- 0.2 (mean +/- SEM, p less than 0.05) as a consequence of a marked decrease in systemic blood flow (5.3 +/- 0.7 to 3.6 +/- 0.51/min/m(2), p less than 0.05). Pulmonary flow did not change significantly. Mean pulmonary capillary wedge and right atrial pressures decreased by 53% (10.2 +/- 1.4 to 4.8 +/- 1.4 mm Hg [p less than 0.01] and 6.0 +/- 1.4 to 2.8 +/- 1.1 mm Hg [p less than 0.05], respectively). Decreases in mean aortic (63.6 +/- 3.0 to 54.6 +/- 2.1 mm Hg, p less than 0.05) and mean pulmonary artery pressure (41.4 +/- 6.2 to 32.0 +/- 6.7 mm Hg, p less than 0.05) were also observed. An apparently paradoxical increase in systemic resistance occurred (11.7 +/- 1.6 to 15.4 +/- 2.4 U, p less than 0.05. Our data show that nitroprusside causes a marked decrease in systemic blood flow and an increase in the pulmonary-to-systemic flow ratio in infants with a large ventricular septal defect. These findings may be related to the hemodynamic profile of these infants, in whom ventricular function, cardiac output and systemic resistance are normal.

Blood Circulation↗
PubMedDate not supplied

Neonatal cardiac catheterization: A 10-year transition from diagnosis to therapy.

To assess the changing role of cardiac catheterization in the care of the neonate, a retrospective review of all catheterizations between January 1984 to December 1985 (group I) and January 1994 to December 1995 (group II) at C.S. Mott Children's Hospital was performed. Neonatal cardiac catheterization was performed more frequently (p = 0.02) in group I, comprising 14% (110 of 772) of all catheterizations versus 11% (93 of 880) in group II. Access was performed by cutdown in 15 patients (13 venous and 2 arterial), all in group I. In group I, 20 of 110 patients (18%) had balloon atrial septostomies; no other catheter interventions were performed. Interventions were more frequent (p = 0.003) and varied in group II, including 15 septostomies, 17 balloon valvuloplasties (13 pulmonary and 4 aortic), 2 coil embolizations of collaterals, and 1 cardiac biopsy. Despite the higher prevalence and complexity of interventions in group II, fluoroscopy times (median; range: 16 min; 2-55 vs 16 min; 1-107) were similar in both groups (p = not significant) as well as the prevalence of complications. Neonatal cardiac catheterizations are performed less frequently than they were a decade ago at our institution, and therapeutic interventions have become more common. Despite these changes, fluoroscopy time and the rate of complications have not increased.

Cardiac Catheterization↗