Effects of low-dose dopamine infusion on cardiovascular and renal functions, cerebral blood flow, and plasma catecholamine levels in sick preterm neonates.

Effects of 2 and 4 micrograms/kg/min dopamine infusion on cardiovascular and renal functions, cerebral blood flow (CBF) and plasma catecholamine levels were studied in sick preterm neonates during the first four days of life. Preterm infants were found to have an enhanced responsiveness to the pressor effects of dopamine during this period. Comparison of the renal effects of 2 and 4 micrograms/kg/min dopamine in 61 preterm infants indicate that 2 micrograms/kg/min dopamine induces maximum diuresis and natriuresis during the first day of life provided that systemic blood pressure is within the predicted normal range. Although administration of 4 micrograms/kg/min dopamine induces further increases in blood pressure and glomerular filtration rate, urine output and sodium excretion remain similar to that on 2 micrograms/kg/min of the drug. These findings demonstrate that the direct tubular effects of dopamine play an important role in the diuretic and natriuretic action of the drug in the one-day old preterm infant. In five preterm neonates, changes in CBF transiently paralleled the dopamine-induced alterations in systemic blood pressure indicating that autoregulation of CBF is impaired but not completely ineffective in the one-day old preterm infant. In eight term neonates, increases in blood pressure had no effect on CBF. Measurements of plasma dopamine and norepinephrine levels in 14 preterm neonates and five children suggest that decreased metabolism of dopamine may contribute to the enhanced pressor responsiveness to dopamine in sick preterm infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrospinal fluid and plasma beta-endorphin-like immunoreactivity in full-term neonates and in preterm neonates with and without apnea of prematurity.

Beta-endorphin-like immunoreactivity (B-ELI) was measured in cerebrospinal fluid (CSF) and plasma from infants of postnatal age 24 h to 70 days. Three groups were examined: 17 were of postconceptual age greater than or equal to 37 weeks, 16 were postconceptual age less than or equal to 35 weeks without apnea and 10 were of postconceptual age less than or equal to 35 weeks with apnea. All infants were clinically stable. Two-way analysis of variance between groups showed no difference in the concentration of B-ELI in CSF or plasma, or in the CSF/plasma B-ELI ratio. Concentrations of B-ELI in plasma were significantly higher in infants of postnatal age 1-3 weeks and greater than or equal to 4 weeks, than in infants of postnatal age less than 1 week. We conclude that, in nonstressed infants, there is no relationship between the concentration of B-ELI in CSF or plasma and a concurrent diagnosis of apnea of prematurity. Our data indicate that a significant developmental increase occurs in the plasma concentration of B-ELI after the first week of life.

Cytogenetic studies on peripheral blood cultures of neonates treated in an intensive unit.

The possible causes of an increased rate of structural chromosomal aberrations and sister chromatid exchange in peripheral blood cultures of mechanically ventilated newborns in an intensive care unit were investigated. No cytogenetic abnormalities were found in low-birth-weight babies affected by hypoxia and acidosis during their first week of life. The rate of chromosome breakage and sister chromatid exchange was increased in blood cultures of neonates continuously ventilated with 70-80 vol% oxygen for a long period of time. The incidence and degree of chromosomal damage, although showing wide individual variations, was related to the duration of oxygen treatment. In addition to high oxygen tension, other environmental factors of intensive care therapy like antibiotic and chemotherapeutic agents may be responsible for the mutagenic effect. The results indicate once again the importance of continuous pO2-monitoring of ventilated newborns.

Lymphocyte subpopulations in peripheral blood of small-for-gestational age and appropriate-for-gestational age preterm neonates.

The lymphocyte subpopulations were investigated in peripheral blood of small-for-gestational age (SGA) and appropriate-for-gestational age (AGA) preterm newborns. In SGA newborns the number and percentage of T lymphocytes were reduced. Among the T lymphocytes, the number and percentage of T helper cells were significantly decreased. The cytotoxic/suppressor T cells were also reduced, but to a lesser extent.

Bacterial colonization of newborn infants in an intensive care unit.

Bacterial screening of external ear, umbilical and gastric fluid samples from infants at admission to the intensive care unit yielded opportunistic pathogens in 22% and 12% in the years 1980 and 1982, respectively. As a result of improved hygienic measures and more rational use of antibiotics, bacterial colonization of infants staying longer than 3 days decreased from 56% to 19%. Antibiotic treatment is not indicated if opportunistic pathogens except Streptococcus agalactiae (group B), are cultured from infants without clinical symptoms.

Alterations in creatinine clearance during respiratory distress syndrome.

Some renal parameters have been studied in newborns with respiratory distress syndrome (RDS). During the first 24 h, the serum creatinine level of the severe cases of RDS are significantly increased, decreasing gradually with improvement of the RDS and reaching normal values within 10 days. Blood urea nitrogen remained unchanged. In the milder cases of RDS, the serum creatinine also showed a slighter increase, which became normal within 4 days after birth. During the acute phase of RDS, there is a reversible impairment in the renal function, which correlates with the degree of hypoxia, hypercapnia and acidosis determined by the primary disease.

Reversibility and interaction with hepatic regeneration of toluene induced liver injury.

Acute and subacute toluene poisoning was induced in CFY rats. Routine histological, enzyme histochemical and electron microscopic investigations revealed that following discontinuation of exposure, the hepatic changes indicating an enhanced load on the detoxicating function (increased SDH activity, increase of mitochondria and smooth endoplasmic reticulum, decrease in Best carmine staining and PAS positivity) as well as degeneration (dilation of endoplasmic reticulum, accumulation positivity) as well as degeneration (dilation of endoplasmic reticulum, accumulation of autophagous vacuoles) show a rapid regression. The toxic effect of toluene and the functional load on the liver is thus reversible. In another series, toluene exposure was combined with partial hepatectomy. It has been established by routine histological, enzyme histochemical and electron microscopic techniques as well as by quantitative light and electron microscopic methods that the two interventions show a peculiar interaction: hepatic regeneration following partial hepatectomy inhibited the effect of toluene. On the other hand, the rate of regeneration was not influenced by toluene.