Biomedical subjects
Publications and source records attributed to B Siassi.
VVLBW infants pose a challenge in the management of their hemodynamic changes. Data are just accumulating regarding the hemodynamic variables in this very special group. We have described several newly developed methods of monitoring hemodynamic variables in infants less than 1000 gm. In the coming decade, some of these methods may become more refined and routine.
The aortic root dimension and aortic valve excursion of 43 normal fetuses were recorded with M-mode echocardiography and the measured dimensions correlated with noncardiac measurements (biparietal diameter, head circumference, abdominal circumference, and femur length) and cardiac measurements (diastolic biventricular inner dimension, diastolic left ventricular internal dimension, and mitral valve excursion). The correlation coefficients for the aortic root dimension ranged between 0.87 and 0.95, while those for the aortic valve excursion ranged between 0.78 and 0.87. Regression analysis demonstrated that the best fit of the data was a linear model from which the 5% and 95% confidence limits were computed for individual predictions of aortic root dimension and aortic valve excursion from noncardiac and cardiac measurements.
Aortic root diameter measurements were obtained during the first week of life by M-mode echocardiography using leading edge methodology during early diastole in 172 preterm and 228 term neonates. At least 40 newborns were included in each 500-g birth-weight subgroup from 750 to 4750 g. The aortic root diameter increased linearly from 0.63 +/- 0.04 cm in newborns with birth weights of 750-1249 g to 1.06 +/- 0.06 cm in newborns of 4250-4750 g.
Decreased cardiac output is a common presumption in left ventricular myocardial dysfunction in neonates, but because of a lack of reliable noninvasive techniques, data on cardiac output are missing. We measured cardiac output by pulsed Doppler echocardiography in 22 newborn infants with left ventricular myocardial dysfunction diagnosed by M-mode echocardiography. Eleven neonates had severe perinatal asphyxia, seven had tachypnea, two hypoglycemia, and one septic shock; one had no symptoms. Right ventricular function was abnormal in 13 of the 22 infants. Hypotension was found in eight; cardiac output and stroke volume were low in 20. The abnormalities were more pronounced in infants with asphyxia. Six such infants were given dopamine (4 to 10 micrograms/kg/min). Within 1 hour, arterial blood pressure, cardiac output, stroke volume, and heart rate increased sharply, with normalization of the myocardial contractility; the other echocardiographic abnormalities normalized over 24 to 48 hours. Pulsed Doppler echocardiography is an advance in the detection and evaluation of therapy for left ventricular myocardial dysfunction in the neonate.
The purpose of our study was to quantitate left ventricular outflow obstruction in the infant of the diabetic mother (IDM) through estimation of cardiac output by pulsed Doppler ultrasound. We evaluated 42 IDMs (White class B, C, or D) and compared them with two control groups, one similar in birth weight and the other similar in gestational age. Ventricular septal hypertrophy was found in 18 (43%) of 42 of the IDMs, but in none of the control infants. Morbidity increased with advancing septal thickness. None had hyaline membrane disease. Twenty-nine IDMs were asymptomatic, 11 of whom had septal hypertrophy. Thirteen IDMs developed congestive heart failure, seven of whom had septal hypertrophy. Cardiac output per kilogram diminished linearly with increasing septal thickness (r = -0.78, P less than 0.001) secondary to reduced stroke volumes at comparable heart rates. The IDMs had higher left atrial/aortic ratios and greater right ventricular systolic time intervals than the control infants. We conclude that cardiac output is significantly reduced in IDMs with septal hypertrophy. This reduction is secondary to reduced stroke volume and is directly related to the degree of septal hypertrophy.
Eighty-two normal fetuses were scanned from 18 to 41 weeks of gestation. The following M-mode measurements were correlated with the abdominal circumference: diastolic biventricular outer (r = 0.951) and inner (r = 0.948) dimensions; diastolic right (r = 0.942) and left (r = 0.925) internal dimensions; tricuspid (r = 0.916) and mitral (r = 0.900) valve opening excursions; and right (r = 0.774), left (r = 0.731), and interventricular septal (r = 0.753) wall thickness. Polynomial regression demonstrated that linear regression best described the data from which the mean and 5 per cent and 95 per cent confidence limits for predicted M-mode measurements were computed for the abdominal circumference between 12 and 35 cm.
Noninvasive monitoring of cardiac output can greatly facilitate the clinical assessment and management of neonates with cardiovascular compromise. To assess normal values of cardiac output in neonates, mean blood flow velocity was measured in the ascending aorta from a suprasternal approach using a range-gated, pulsed Doppler velocity meter, and aortic root diameter was determined from an M-mode echocardiogram. These techniques were combined, and cardiac output was evaluated in 59 healthy premature and 62 term newborn infants during the first week of life. Birth weights ranged from 780 g to 4,740 g and gestational age from 27 to 42 weeks. Cardiac output values increased linearly with advancing birth weight (r = +.94, P less than 0.001) and gestational age (r = +.95, P less than .001). Mean cardiac output values (+/- SD) per kilogram of body weight were 249 +/- 34 mL/min/kg and decreased with advancing birth weight: less than 1,500 g = 265 +/- 32 mL/min/kg; 1,500 to 2,500 g = 253 +/- 34 mL/min/kg; and greater than 2,500 g = 241 +/- 33 mL/min/kg. For clinical use, 325 mL/min/kg and 200 mL/min/kg can be used as upper and lower limits of normal, respectively. Doppler cardiac output estimates compared favorably with studies using invasive techniques.
Heart rate, blood pressure, transcutaneous gases, and catecholamine changes following intravenous injection of pancuronium were evaluated in seven ill newborn infants (birth weight: 1,280 to 4,500 g; gestational age, 29 to 42 weeks). Each infant was monitored continuously for 30 minutes before and 50 minutes after infusion of the paralyzing agent. There were no significant changes in transcutaneous gases, whereas significant increases in heart rate; systolic, diastolic, and mean blood pressures; and blood norepinephrine and epinephrine levels were found. The increase in heart rate lasted for 30 minutes, and the increase in blood pressure persisted for 50 minutes after administration of the drug. Because of the potential relationship between increased blood pressure and intraventricular hemorrhage and myocardial dysfunction, heart rate and blood pressure must be monitored during infusion of pancuronium in distressed newborns. These data suggest that pancuronium stimulates sympathetic activity in distressed newborns.
Phototherapy is known to increase peripheral blood flow in neonates, but information on the associated cardiovascular effects is not available. Using pulsed Doppler echocardiography we evaluated cardiac output and stroke volume in 12 preterm and 13 term neonates during and after phototherapy. We concomitantly measured arterial limb blood flow by strain gauge plethysmography and skin blood flow by photoplethysmography. Cardiac output decreased by 6% due to reduced stroke volume during phototherapy, whereas total limb blood flow and skin blood flow increased by 38% and 41%, respectively. Peripheral blood flow increments tended to be higher in the preterm than in the term infants. The reduced stroke volume during phototherapy may be an expression of reduced activity of the newborn during phototherapy. For healthy neonates the reduction in cardiac output is minimal, but for sick infants with reduced cardiac output, this reduction may further aggravate the decrease in tissue perfusion.
M-mode echocardiographic examination of the right and left ventricles was performed on 82 normal fetuses between 18 and 41 weeks of gestation. The diameter of the right and left ventricles correlated with the biparietal diameter. The right/left ratio of the ventricular diameters remained constant (1:1) throughout gestation. Fractional shortening and mean circumferential shortening of both ventricles were independent of gestational age. The data presented in this paper will allow the clinician to evaluate abnormal fetal conditions that might affect cardiovascular structure and/or function.
A technique that makes use of real-time-directed M-mode echocardiography is described in which the fetal heart is evaluated for suspected cardiac arrhythmias. Simultaneous M-mode recording of aortic, mitral, or tricuspid valvular leaflet excursion and/or atrioventricular wall motion defines timing relationships between atrial and ventricular systole. With the use of the techniques described in this report, normal as well as abnormal atrioventricular contractions can be quantitated and cardiac arrhythmias accurately defined.
The incidence of clinically detectable patient ductus arteriosus (PDA) in a group of preterm infants whose birth weights were less than 2,000 g was compared with that of a similar group of infants whose mothers received antenatal glucocorticoids. A PDA was diagnosed on the basis of a typical heart murmur, increased precordial activity, and bounding peripheral pulses beyond the third day of life. Whereas 14 (44%) of 32 infants who were not exposed to antenatal glucocorticoids showed evidence of a PDA, only one (6.5% of 15 infants whose mothers received antenatal glucocorticoids had similar findings. The incidence of ruptured membranes (greater than 72 hours), the number of infants who were small for gestational age, and clinical management of the infants in the two groups were similar.
Neonatal heart rate (HR) and arterial blood pressure (BP) were recorded continuously for the 1st hour of life in term newborn infants of normotensive (control group) and pre-eclamptic (study group) primiparous mothers. Infants were matched for gestational age, birth weight, method of delivery, and Apgar scores. In infants of pre-eclamptic mothers, the HR was significantly lower for the 1st 50 min of life, and their mean arterial blood pressure (MAP) was significantly higher during the 1st 20 min of life.
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Experience is presented of paediatric cardiology in a well-equipped and staffed centre during a six-year period in a developing country. Despite the success of the programme in offering first class medical investigation and surgical care to a large number of children, it is estimated that only about 2% of the existing cases in the country were operated upon. The main problems were the large numbers of cases, creating long waiting lists, and the lack of adequately trained paramedical personnel. Although paediatric cardiology in other developing countries is by no means a first priority, thousands of children suffering from heart disease should not be ignored. It appears that establishing similar centres for the care of children with heart disease in those countries is necessary; that they would contribute to patient care and medical education, would uncover the magnitude of the problem and would open ways to its future solution. The possibility of utilization of the facilities in the Western countries must also be considered.
The authors evaluated transcutaneous PCO2 (PtcCO2) and PO2 (PtcO2) electrodes in 25 infants. Their diagnosis were severe hyaline membrane disease (HMD) (18), aspiration syndrome (3), severe hydrops, (3) persistent fetal circulation (6), and the others, congenital pneumonia, congenital plural effusion, pulmonary hemorrhage. In most all, the cardiovascular system was compromised, i.e., PDA with congestive heart failure and shock. PtcO2 electrode was heated to 43.5 degrees C while PtcCO2 electrode was not heated. Simultaneous arterial blood pressure (ABP), pH, arterial blood gases were obtained with the transcutaneous gas measurements. The data were analyzed first dividing all the paired arterial and transcutaneous gas tensions into those with and without cardiovascular drugs (dopamine, isoproterenol), and second, the paired values were divided into those taken (a) during severe acidosis (pH less than 7.25), (b) hypotension (less than 2 SD) of normal, and (c) hypotension and acidosis. These data show: (1) the unheated PtcCO2 and heated PtcO2 accurately correlated with the simultaneous arterial measurements: (2) PtcCO2 reflects tissue PCO2; (3) drugs affect both the PtcCO2 and PtcO2; (4) elevated PtcCO2 dissociating from the simultaneous PaCO2 in neonates with cardiovascular compromise results from decreased tissue perfusion. These data suggest that transcutaneous gas sensors perform dual functions; first, as gas monitors in patients without cardiovascular alterations, and second, in patients with cardiovascular compromise, PtcCO2 reflected tissue perfusion and PtcCO2 monitored oxygen delivery to the tissues.
Fetal and neonatal biophysical and biochemical changes were studied in four preterm infants who developed cardiogenic shock as a result of severe perinatal asphyxia. Fetal distress was documented by the presence of severe late and variable decelerations associated with decreased fetal heart rate variability. Severity of fetal acidosis was decumented by scalp and umbilical cord blood pH. Apgar scores at 1, 5, and 10 minutes were all equal to or less than 5. Although the clinical findings shortly after birth resembled respiratory distress syndrome, it was possible to make a primary diagnosis of cardiac failure with the recognition of cardiomegaly, hepatomegaly, electrocardiographic changes of myocardial hypoxia, decreased myocardial contractility, elevated central venous pressure, and severe lactic acidosis. The treatment of heart failure, including use of inotropic agents, resulted in rapid improvement in the clinical condition, with reversal of the abnormal findings within 24 to 36 hours. Concomitant with this improvement, the increase in arterial blood pressure was paralleled by increase in peripheral (toe) temperature.