Hemodynamic effects of positive end-expiratory pressure during partial liquid ventilation in newborn lambs.

Background/purpose: The aim of this study was to compare the effect of positive end-expiratory pressure (PEEP) application on hemodynamics, lung mechanics, and oxygenation in the intact newborn lung during conventional ventilation (CV) and partial liquid ventilation (PLV) at functional residual capacity (FRC). CV or PLV modes of ventilation do not affect hemodynamics nor the optimum PEEP for oxygenation.

Methods: Seven newborn lambs (1 to 3 days old) were instrumented to measure pulmonary hemodynamics and airway mechanics.

Gastroschisis and Hirschsprung's disease: a rare combination.

The authors report on a neonate with gastroschisis repaired at birth who later had abdominal distension, emesis, feeding intolerance, and an abnormal stooling pattern. Total colon and partial small bowel aganglionosis (TCAS), or Hirschsprung's disease, was diagnosed subsequently. This is the first report of this combination of gastrointestinal anomalies.

Form and function of fetal and neonatal pulmonary arterial bifurcations.

Bifurcation is a basic form of vascular connection. It is composed of a parent vessel of diameter d(0), and two daughter vessels, d(1) and d(2), where d(0) > d(1) >/= d(2). Optimal values for the bifurcation area ratio, beta = (d(1)(2) + d(2)(2))/d(0)(2), and the junction exponent, x, in d(0)(x) = d(1)(x) + d(2)(x), are postulated to be universal in nature.

Effects of correction of hypocalcemia on cardiac function in the newborn lamb.

The effect of correction of hypocalcemia on cardiac function in the neonate is unclear. Therefore, we evaluated changes in hemodynamic variables and cardiac contractility in a hypocalcemic neonatal lamb model. Baseline serum ionized hypocalcemia was induced via chelation with intravenous EGTA.

Role of nitric oxide in cardiovascular responses to endotoxemia in neonatal lambs.

To determine whether systemic cardiovascular responses to gram-negative endotoxemia are mediated by nitric oxide, we evaluated time-dependent changes in contractility and hemodynamics in a neonatal sheep model subjected to nitric oxide synthesis inhibition with L-Name (Nomega-nitro-L-arginine methyl ester). Four groups were studied: control (C), endotoxin (E), endotoxin L-Name where the nitric oxide synthase inhibitor was given prior to endotoxin (ELN), and a control L-Name group pretreated with L-Name (CLN). The contractility, measured as end-systolic elastance (Ees), increased transiently in the E group and then returned to baseline.

Changes in endothelial cell and smooth muscle cell integrin expression during closure of the ductus arteriosus: an immunohistochemical comparison of the fetal, preterm newborn, and full-term newborn rhesus monkey ductus.

Anatomical closure of the ductus arteriosus requires normally quiescent luminal endothelial cells and medial smooth muscle cells to migrate into the subendothelial space forming intimal mounds that eventually coalesce and occlude the vessel's lumen. The migration of endothelial cells and smooth muscle cells requires the presence of integrin receptors that interact with the surrounding matrix. We used immunohistochemical staining to examine the repertoires of integrins expressed by endothelial cells and smooth muscle cells during postnatal closure of the ductus arteriosus in full-term and preterm rhesus monkeys.

Role of arterial design on pulse wave reflection in a fractal pulmonary network.

A novel interpretation of pulmonary arterial input impedance was evaluated for the lung as a fractal vascular network. We hypothesized that local sources of reflection introduce trends of global reflection into the input impedance spectra. These trends are related to the network topology, geometry, and design according to Rb = Rdx, where Rb is the branching ratio, Rd is the diameter ratio, and x is the fractal dimension quantifying design.

Intracranial pressure and cerebral perfusion pressure in clinically normal equine neonates.

Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were determined in 8 clinically normal neonatal foals. After the foals oriented themselves and nursed the mares, they were sedated as necessary, and local anesthesia was provided for making the skin incisions. Using a technique similar to that used in human beings, an indwelling subdural catheter was placed to measure ICP.

Irreversibility of birth-related changes in the pulmonary circulation.

We hypothesized that establishing conditions of hypoxia and fluid filling of the airways in lungs of newborns would reproduce the high levels of pulmonary vascular resistance (PVR) observed in the fetal state. We assessed the hemodynamics of the left pulmonary circulation of 1- to 3-day-old lambs during a variety of airway states while attempting to reestablish fetal conditions. Eleven animals were studied during both normoxemia and hypoxemia in a baseline airway state with a positive end-expiratory pressure (PEEP) of 4 cm H2O, and in experimental airway states, of atelectasis, and fluid filling to 15 and 30 mL/kg and with PEEP of 12 cm H2O.

Risk factors for bacteriuria in men.

Objective: To identify risk factors for bacteriuria in a selected group of institutionalized men.

Methods: A total of 99 men, mean age seventy-one years, range forty-eight to one hundred four years, living in a nursing home were evaluated for diagnoses of benign prostatic hyperplasia (BPH) and diabetes mellitus (DM), symptoms of bladder outlet obstruction, and postvoid residual urine volume (PVR). At the time of evaluation urine cultures were performed for all subjects.

Prenatal exposure to epidermal growth factor attenuates respiratory distress syndrome in rhesus infants.

Treatment of nonhuman primate fetuses with epidermal growth factor (EGF) results in histologic and biochemical maturation of their lungs. To determine whether these effects improve lung function postnatally, we studied premature rhesus infants delivered at 78% of gestation after in utero treatment with EGF (n = 5) or placebo (n = 5). Indices of lung function during the 4 d of postnatal care included fractional concentration of inspired oxygen, peak inspiratory pressure, ventilator rate, mean airway pressure, arterial to alveolar oxygen tension ratio, and ventilation index.

Brain injury and protective effects of hypothermia using triphenyltetrazolium chloride in neonatal rat.

Colorless 2,3,5-triphenyltetrazolium chloride (TTC) is reduced by enzymes in functioning mitochondria to a red-colored compound, and has been used to differentiate areas of viable tissue from areas of infarction in adult animals. TTC was used to study the central nervous system protective effects of hypothermia on the neonatal rat exposed to hypoxia and ischemia. The effect of hypothermia on survival and weight gain was also determined.

Intratracheal administration of pulmonary vasodilator agents.

We compared intravenous and intratracheal administration of histamine (0.4 and 1.6 micrograms/kg, respectively) and nitroglycerin (5.

The influence of pulsatile perfusion on the vascular properties of the newborn lamb lung.

It is not known how the mode of flow alters the resistance properties of the newborn pulmonary circulation. Therefore, we compared the pressure responses of the perfused left pulmonary circulation of 16 newborn lambs with step changes in either pulsatile or steady flow. The slope of the pressure-flow curve differed significantly according to mode of perfusion.

Hypoxic pulmonary hypertension: changes in platelet size and number.

Circulating platelets have been implicated in the hypoxic pulmonary pressor response. This study was undertaken to assess the effects of acute hypoxia-induced pulmonary hypertension on platelet volume and number across the pulmonary circulation in anesthetized newborn lambs. Seven animals were instrumented for measurement of pulmonary vascular resistance.

Age-dependent effects of sodium nitroprusside and dopamine in lambs.

Vasodilators and cardiotonic agents are frequently used in hypoxemic newborn infants with persistent pulmonary hypertension. We studied the effects of sodium nitroprusside and dopamine on hypoxia-induced pulmonary hypertension in seven newborn (0-3 d) and seven young (10-14 d) lambs under chloralose anesthesia. Pulmonary blood flow, pulmonary arterial pressure, systemic arterial pressure, and left atrial pressure were measured during the experimental states of hypoxia, hypoxia plus nitroprusside, and hypoxia plus both nitroprusside and dopamine.

Hemodynamic responses to angiotensin II in the newborn lamb.

Angiotensin II is known to increase both pulmonary and systemic arteriolar tone in adult animals. Its influence on these vascular beds shortly after birth is less well understood. Therefore, we studied the effects of infusions of angiotensin II (0.

Bilateral renal dysplasia with nephron hypoplasia in a foal.

Bilateral renal dysplasia and nephron hypoplasia was diagnosed in a Quarter Horse foal with clinical signs of lethargy, convulsions, and diarrhea. Laboratory evaluation revealed anemia, hypoproteinemia, leukopenia, hyponatremia, hypochloremia, and hyposmolality. The foal also had high concentrations of serum creatinine, BUN, and phosphorus.

Effect of blood sampling site on measurements of bilirubin-albumin binding.

Significant arterio-venous concentration gradients in metabolites such as lactate could result in sampling site differences in bilirubin binding measurements. Therefore, total bilirubin and apparent unbound bilirubin concentrations were determined on paired capillary and arterial serum samples from ten neonates with hyaline membrane disease. There were no significant arterial versus capillary differences in bilirubin binding in these infants.

Neuropathologic documentation of prenatal brain damage.

Neuropathologic evidence of prenatal brain damage, chiefly in cerebral white matter, was found in 25% of infants who died at 7 days of age or less, with a total of ten preterm (16%) and 12 term (48%) infants among the 89 subjects studied. Few clinical features distinguished infants with prenatal injury from those without such injuries. Apgar scores were low, seizures were rare, and acute intracranial hemorrhage occurred equally often in both groups.

Effect of pulmonary hypertension on lung compliance in newborn lambs.

We studied the effects of increased pulmonary arterial pressure and vascular resistance on lung compliance in 12 anesthetized newborn lambs. Lung compliance was unaffected by large changes in pulmonary artery pressure and pulmonary vascular resistance (80% increase) that were induced by either hypoxia or acidosis. We conclude that contraction of the pulmonary vascular smooth muscle in normal newborn lambs does not affect the stiffness of the lung in the parenchymal regions undergoing volume change during ventilation.