QUANTITATIVE STUDIES OF THE HUMAN NEONATAL CIRCULATION.: IV. OBSERVATIONS ON THE NEWBORN INFANT'S PERIPHERAL CIRCULATION AND PLASMA EXPANSION DURING MODERATE HYPOVOLEMIA

Delayed cord clamping in very preterm infants reduces the incidence of intraventricular hemorrhage and late-onset sepsis: a randomized, controlled trial

OBJECTIVE

This study compared the effects of immediate (ICC) and delayed (DCC) cord clamping on very low birth weight (VLBW) infants on 2 primary variables: bronchopulmonary dysplasia (BPD) and suspected necrotizing enterocolitis (SNEC). Other outcome variables were late-onset sepsis (LOS) and intraventricular hemorrhage (IVH).

STUDY DESIGN

This was a randomized, controlled unmasked trial in which women in labor with singleton fetuses <32 weeks' gestation were randomly assigned to ICC (cord clamped at 5-10 seconds) or DCC (30-45 seconds) groups. Women were excluded for the following reasons: their obstetrician refused to participate, major congenital anomalies, multiple gestations, intent to withhold care, severe maternal illnesses, placenta abruption or previa, or rapid delivery after admission.

RESULTS

Seventy-two mother/infant pairs were randomized. Infants in the ICC and DCC groups weighed 1151 and 1175 g, and mean gestational ages were 28.2 and 28.3 weeks, respectively. Analyses revealed no difference in maternal and infant demographic, clinical, and safety variables. There were no differences in the incidence of our primary outcomes (BPD and suspected NEC). However, significant differences were found between the ICC and DCC groups in the rates of IVH and LOS. Two of the 23 male infants in the DCC group had IVH versus 8 of the 19 in the ICC group. No cases of sepsis occurred in the 23 boys in the DCC group, whereas 6 of the 19 boys in the ICC group had confirmed sepsis. There was a trend toward higher initial hematocrit in the infants in the DCC group.

CONCLUSIONS

Delayed cord clamping seems to protect VLBW infants from IVH and LOS, especially for male infants.

Short-term effects of blood transfusion on blood volume and resting peripheral blood flow in preterm infants

The effects of blood transfusion on cardiac output and blood pressure are variable, but resting peripheral blood flow (RPBF) may be a sensitive indicator of changes in blood volume. The purpose of this investigation was to study the effects of red cell transfusion on blood volume (Evans blue), blood pressure, RPBF in the leg (strain-gauge plethysmography) and blood viscosity (cone-plate viscometer) in preterm infants during the first week after birth. Fourteen infants with mean +/- SD birth weight of 1658 +/- 429 g, gestational age 33 +/- 3 weeks and postnatal age 64 +/- 40 h received 18 +/- 4 ml/kg of packed red cells (red cells 11 +/- 2 ml/kg, plasma 7 +/- 1 ml/kg) because their hematocrit was less than 0.45 l/1. Mean blood volume before transfusion was 88 +/- 15 ml/kg. The increase in blood volume (9 +/- 4 ml/kg) measured 4 to 6 h after transfusion was smaller than the transfused volume (18 +/- 4 ml/kg), due to a shift of plasma to the extravascular space. The plasma shift increased with increasing pretransfusion blood volume (r = 0.70; p = 0.007). Red cell transfusion caused an increase in RPBF by 25% (p < 0.01), whereas systolic blood pressure (BP) increased by only 12%. Peripheral resistance (R = BP/RPBF) decreased by 9% (p < 0.01). Blood viscosity (eta) increased by 21% (p < 0.001) and vascular hindrance (R/eta) decreased by 24% (p < 0.001), indicating vasodilatation of limb arteries. The increase in RPBF and the decrease in hindrance were particularly pronounced in infants with high pretransfusion blood volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamics after hemorrhage during acute ethanol intoxication in newborn piglets

Hemodynamic alterations after hemorrhage were investigated using the microsphere technique in nitrous oxide-anesthetized 2-day-old piglets after acute ethanol intoxication (1.4 g/kg). After hemorrhage (20 ml/kg), mean arterial blood pressure decreased by 34% (p less than 0.01), cardiac output decreased by 58% (p less than 0.01), and systemic vascular resistance increased by 87% (p less than 0.01). In nonintoxicated piglets subjected to hemorrhage, mean arterial blood pressure decreased 17% (p less than 0.01) while alterations in cardiac output and systemic vascular resistance were not significant. Intoxicated piglets had delayed heart rate increases of 11% (p less than 0.01) while heart rate in nonintoxicated piglets increased 27% (p less than 0.01) immediately after hemorrhage. After hemorrhage, arterial perfusion to the liver, kidneys, gastrointestinal organs, and carcass was decreased in intoxicated piglets but only gastrointestinal and carcass perfusion were reduced in nonintoxicated piglets. In summary, acute ethanol intoxication significantly impaired the newborn piglet's cardiovascular response to moderate hypovolemia and delayed the onset of a compensatory tachycardia response. Such cardiovascular impairments may be extremely detrimental to neonates.

Forehead skin blood flow in normal neonates during active and quiet sleep, measured with a diode laser Doppler instrument

Changes in forehead skin blood flow during active and quiet sleep were determined in 16 healthy neonates using a recently developed semi-conductor laser Doppler flow meter with-out light conducting fibres. Measurements were carried out at a postnatal age varying from 5 hours to 7 days. The two sleep states could be distinguished in 17 recordings. The mean skin blood flow values during active sleep were significantly higher (p less than 0.01) than those during quiet sleep, the mean increase being 28.1%. The variability of the flow signal, expressed as the coefficient of variation, changed significantly from 23.1% during active sleep to 18.2% during quiet sleep.

Sympathoadrenal activity and peripheral blood flow after birth: comparison in infants delivered vaginally and by cesarean section

The possible influence of sympathoadrenal activity on peripheral blood flow was studied. Limb blood flow was measured with venous occlusion plethysmography at 30 minutes, 2 hours, and 24 hours after birth in 24 healthy, full-term infants, of whom 14 were delivered by elective cesarean section. Mean arterial pressure was simultaneously measured noninvasively, and peripheral vascular resistance calculated. Umbilical artery blood at birth and peripheral venous blood at 2 and 24 hours were analyzed for concentrations of catecholamines and hematocrit. The limb blood flow was significantly lower at 30 minutes in the vaginally delivered infants compared with those delivered by cesarean section. There was a gradual increase in limb blood flow over the 24 hours in those delivered vaginally, whereas in the section group only small changes were observed. The peripheral vascular resistance was higher both at 30 minutes and at 2 hours in those delivered vaginally, which corresponded to the higher catecholamine concentrations at birth and at 2 hours in this group. Two hours after birth there was a significant correlation between noradrenaline levels and peripheral vascular resistance. The results indicate that the sympathoadrenal system influences peripheral circulation at birth and is important in the circulatory adaptation of the newborn infant.

Peripheral circulation in the newborn: interaction of peripheral blood flow, blood pressure, blood volume, and blood viscosity

Peripheral blood flow and systolic blood pressure (strain-gauge plethysmograph), blood volume (Evans blue) and whole blood viscosity (cone-plate viscometer) have been measured in 66 premature and full-term infants 6 to 144h of age. Blood flow and blood volume were moderately decreased in the infants with respiratory distress. Highly significant (P less than 0.001) correlations were found between blood flow and blood volume (r = 0.77), blood pressure and blood volume (r = 0.50), peripheral resistance and blood volume (r = -0.44), blood flow and blood pressure (r = 0.50), blood flow and peripheral resistance (r = -0.67), peripheral resistance and blood viscosity (r = 0.45), and blood viscosity and haematocrit (r = 0.86). There was no correlation between peripheral blood flow and blood viscosity. However, at given blood volume, peripheral blood flow decreased with increasing blood viscosity. These results indicate that in newborn infants peripheral blood flow, blood pressure and peripheral resistance are influenced by blood volume, but also depend on blood viscosity.

Diminished limb blood flow in infants with transposition of the great vessels: An adaptation to chronic hypoxia?

Calf blood flow was measured by venous occlusion plethysmography using a mercury in rubber strain gauge in infants with transposition of the great vessels. (TGV), and in comparable infants free from cardiopulmonary disease. Resting calf blood flow in the infants with TGV was 3.6 +/- 0.8 ml/100 ml/min, while in the control group flow was 6.8 +/- 2.3 ml/100 ml/min, a highly significant difference. We postulate that newborns with TGV decrease their resting calf flow in response to chronic hypoxia.

Cardiorespiratory response to feeding in newborn infants

Milk feeds were given through indwelling nasogastric tubes to 14 infants with respiratory distress. Similar cardiorespiratory disturbances were observed when the infants were fed (5 ml/kg per feed) human milk, cow's mild, or distilled water. Pao2 fell after a feed but recovered to the prefeed value at 30 minutes, at which time Paco2 had fallen and the respiratory rate had increased. No changes in pH, heart rate, or blood pressure were observed. Portal sinus pressures rose after feeding in association with an increase in central venous pressure. In contrast, when the ill infants were fed human milk at a volume of 2-5 ml/kg per feed no consistent changes in any of the measurements were found. These studies suggested that the cardiorespiratory effects were related to volume displacement resulting from feeds being introduced into the stomach. The relation of the increase in central venous pressure and the magnitude and direction of shunting in infants with the respiratory distress syndrome is uncertain. Adverse effects may be avoided by giving smaller, and therefore even more frequent, feeds.

Blood volume and blood pressure in infants with respiratory distress

Mean aortic blood pressure volume were measured in true premature infants with respiratory distress syndrome. Seven infants had Type I RDS (hyaline membrane disease) and ten had transient tachypnea of the newborn (Type II RDS). Blood volume in the infants with Type I RDS was significantly lower than in the infants with Type II RDS. The difference was due to a low red cell volume. Mean aortic blood pressure was within the range of normal in all infants and therefore did not reflect the low blood volume of infants with Type I RDS. Normal mean aortic blood pressure does not indicate normal blood volume or normal circulation in infants with RDS.