Effects of phenobarbital on cerebral blood flow velocity after endotracheal suctioning in premature neonates.

OBJECTIVE: To examine the effect of phenobarbital administration on anterior cerebral artery blood flow velocity before and after endotracheal suctioning in premature neonates. DESIGN: Transcutaneous PO(2) (TcPO(2)), heart rate, mean arterial blood pressure (MABP), and Doppler velocimeter blood flow of the left anterior cerebral artery were measured before and immediately after 3 consecutive endotracheal suctioning procedures in premature neonates. Intravenous phenobarbital (20 mg/kg) was administered immediately after the first procedure. SETTING: Neonatal intensive care unit. PATIENTS: Nine neonates with a mean birth weight of 807 g (range, 620-1060 g) and a mean gestational age of 27 weeks (range, 25-30 weeks) were studied at age 8 to 12 hours. RESULTS: Transcutaneous PO(2) decreased in response to endotracheal suctioning at each of the suctioning procedures before and after phenobarbital was given (P<.001). Changes in heart rate were not observed. There were increases in MABP and area under the velocity curve (AUVC) per minute in response to endotracheal suctioning before but not after phenobarbital administration (P=.046). Use of phenobarbital lowered the overall peak systolic blood flow velocity in response to endotracheal suctioning (P =.02, analysis of variance, interactions for the effect of phenobarbital therapy on the response to suctioning). Changes in end-diastolic blood flow velocity were not observed. There were decreases in the differences before and after endotracheal suctioning for MABP at 2 and 4 hours and for AUVC and peak systolic blood flow velocity 4 hours after phenobarbital was given (P =.04). CONCLUSIONS: In very low-birth-weight neonates, endotracheal suctioning is associated with decreases in TcPO(2) and increases in MABP and AUVC. Treatment with phenobarbital attenuates the increases in MABP and AUVC but not the decreases in TcPO(2) after endotracheal suctioning.

Cardiovascular effects of hypoxia/hypercarbia and tension pneumothorax in newborn piglets.

OBJECTIVES: To test the hypothesis that, in newborn piglets, the presence of a tension pneumothorax modifies the cardiovascular responses to hypoxia/hypercarbia. DESIGN: Prospective laboratory study. SETTING: Perinatal cardiovascular research laboratory at a university school of medicine. SUBJECTS: Seven newborn piglets. INTERVENTIONS: We sequentially exposed the piglets to a baseline (control I) measure, hypoxia/hypercarbia, tension pneumothorax with normoxia/normocarbia, and tension pneumothorax with hypoxia/hypercarbia added. MEASUREMENTS AND MAIN RESULTS: Brain and systemic blood pressures and blood flow (radionuclide-microspheres) were measured. Hypoxia/hypercarbia resulted in increased brain perfusion (207 +/- 61% of control, mean +/- SEM, p < .05) and heart perfusion (176 +/- 58% of control, p < .05) and decreased gastrointestinal perfusion (-37 +/- 9% of control, p < .05). Tension pneumothorax with normoxia/normocarbia reduced the cardiac output (-70 +/- 8% of control, p < .05), which was redistributed toward the brain (p < .05) at the expense of the gastrointestinal tract (p < .05). Although this redistribution in cardiac output persisted during tension pneumothorax with hypoxia/hypercarbia added, sustained reductions in cardiac output (-57 +/- 11%, of control, p < .01) were associated with smaller increases in perfusion to brain (55 +/- 54 vs. 207 +/- 61% of control, tension pneumothorax with hypoxia/hypercarbia added, and hypoxia/hypercarbia time periods, respectively, p < .05) and heart (65 +/- 49 vs. 176 +/- 58% of control, tension pneumothorax with hypoxia/hypercarbia added, and hypoxia/hypercarbia time periods, respectively, p < .05) and larger decreases in blood flow to gastrointestinal tract, pancreas, and kidneys (p < .05) than with hypoxia/hypercarbia alone. CONCLUSIONS: Tension pneumothorax-induced reductions in cardiac output limit the hypoxia/hypercarbia-mediated increases in perfusion to brain and heart and accentuate the hypoxia/hypercarbia-related decreases in perfusion to kidneys and splanchnic organs.

Asymmetric growth of the lateral cerebral ventricle in infants with posthemorrhagic ventricular dilation.

Lateral cerebral ventricular volume in 36 preterm infants with or without an intraventricular hemorrhage, and with or without posthemorrhagic hydrocephalus, was measured longitudinally and compared with the ventricular index measurements of the same ventricles. A poor correlation was found (r2 = 0.67). To determine a reason for this poor relationship, we analyzed the volumes of the regions of the ventricles by a segmental volume analysis. The occipital region of the lateral cerebral ventricle enlarged at a much faster rate (1.904 +/- 0.477 ml/day) than either the anterior region (0.546 +/- 0.253 ml/day; p less than 0.01) or the middle region (-0.209 +/- 0.334 ml/day; p less than 0.01) in infants with posthemorrhagic hydrocephalus. The rate of growth of the middle region of the lateral cerebral ventricles was the same for all infants. Linear indexes, such as the ventricular index and the lateral ventricular ratio, do not allow for accurate serial estimates of ventricular size in posthemorrhagic hydrocephalus because of asymmetric growth of the lateral cerebral ventricle. We conclude that sequential volume measurements are more useful than ventricular index measurements to follow ventricular size sequentially in infants with posthemorrhagic hydrocephalus.

Measurement of progressive cerebral ventriculomegaly in infants after grades III and IV intraventricular hemorrhages.

To develop guidelines that might help predict prospectively which infants with severe intraventricular hemorrhage (IVH) would require intervention, we obtained serial cranial sonograms to measure the rate of growth of cerebral ventricular volumes in 48 preterm infants with and without IVH. The infants were divided into three groups: (1) those with no IVH (22 infants), (2) those with IVH with acute ventricular dilation (13 infants), and (3) those with IVH with progressive ventricular dilation requiring intervention (13 infants). The decision to intervene because of progressive ventricular dilation was based on clinical criteria and the subjective assessment of increasing ventricular size on weekly cranial sonograms. The rate of cerebral ventricular volume growth in infants with IVH who needed intervention was greater (4.2 +/- 3.3 ml/day) than that in infants without IVH (0.0 +/- 0.1 ml/day; p less than 0.001) and in infants with IVH and acute ventricular dilation (0.0 +/- 0.2 ml/day; p less than 0.001). Using these data, we generated guidelines for predicting prospectively which infants with IVH and ventricular dilation will need intervention for posthemorrhagic hydrocephalus. The guidelines were then confirmed prospectively in 10 infants.

Subcortical visual function in the newborn.

Early behavioral visual function in infants may not depend upon the geniculocalcarine pathway but may be mediated through more primitive subcortical pathways. This subcortical visual system may exist in early life and be responsible for visual pursuit and perhaps fixation. In some infants with damage to the visual cortex, the subcortical pathway may persist beyond the neonatal period. Three infants with major defects in the visual cortex are reported. These infants displayed persistent preservation of visual pursuit movements without evidence of visual recognition. Limited behavioral expressions of vision in the infant with damage to the visual cortex may not always be an indicator of preserved function of the visual cortex.

Quantification of neonatal cerebral ventricular volume by real-time ultrasonography. Derivation and in vitro confirmation of a mathematical model.

The derivation and in vitro confirmation of a method for the calculation of cerebral ventricular volume determined by cranial ultrasonography is described. The derivation depends on use of the cylindrical coordinate method. Confirmation was performed by construction of ultrasound phantoms from latex balloons embedded in a talc/gelatin matrix. Seventeen phantoms of volumes ranging from 10 to 60 mL were measured. The known volume was then compared to the calculated volume by linear regression analysis. The regression analysis indicated a close correlation between the actual volume of the phantoms and the calculated volume with r = 0.96. Various sources of error in the method are discussed. Our results indicate that the cylindrical coordinate mathematical model when applied to cranial ultrasonography images accurately measures cerebral ventricular volumes.

Quantification of neonatal cerebral ventricular volume by real-time ultrasonography. In vivo validation of the cylindrical coordinate method.

Posthemorrhagic ventricular dilation is a common clinical problem in preterm infants who have incurred an intraventricular hemorrhage. Presently there are no clinically applicable methods to follow quantitatively the progression of ventricular dilation at bedside. We describe the in vivo validation of a method to measure ventricular volume using bedside real-time cranial ultrasonography. Six infants undergoing either serial lumbar punctures or cerebral ventricular reservoir taps for posthemorrhagic hydrocephalus were studied. The cerebrospinal fluid (CSF) volume removed ranged from 5.5 mL to 30 mL. A strong correlation was found (r2 = 0.84) between the volume of CSF removed by reservoir tap and the change in ventricular volume calculated by the ultrasound method, whereas the correlation between the volume of CSF removed at lumbar puncture and the change in ventricular volume calculated by the ultrasound method was not as strong (r2 = 0.70). Limitations and sources of error in the method are discussed. We conclude that this procedure is accurate and offers a quantitative method to follow longitudinally posthemorrhagic progressive ventricular dilation.

Cerebral cortical blood flow and oxygen metabolism in normocythemic hyperviscous newborn piglets.

Our study tests the hypothesis that hyperviscosity independent of arterial O2 content reduces cerebral cortical blood flow, O2 delivery, and O2 uptake. After baseline determinations, ten 2- to 4-day-old awake spontaneously breathing piglets were given an intravenous infusion (5 ml.kg-1, body weight) of concentrated cryoprecipitate, whereas eight controls received normal saline. Cerebral cortical blood flow, arterial and superior sagittal sinus O2 content, whole blood viscosity, hematocrit, blood gases, and plasma fibrinogen concentrations were measured at baseline and 3 h after infusion. No significant changes were observed in the control group. Three hours after the infusion of concentrated cryoprecipitate the experimental group showed an increase in whole blood viscosity, whereas hematocrit and arterial O2 content were unchanged. There was a decrease in cerebral cortical blood flow and cerebral cortical O2 delivery, whereas cerebral cortical O2 uptake was unchanged. We conclude that hyperviscosity independent of arterial O2 content reduces cerebral cortical blood flow and that although O2 delivery was reduced in the newborn piglet cerebral cortical O2 uptake was maintained.

Behavioral responsiveness in preterm infants with intraventricular hemorrhage.

Preterm infants with varying degrees of intraventricular hemorrhage (none, n = 21; grade I to II, n = 22; grade II to IV, n = 24) and a group of full-term infants (n = 21) were compared with regard to behavioral responsiveness and parental reports of the infant's temperament. Behavioral responsiveness was assessed during the presentation of 15 visual, auditory, and tactile stimuli at 3 months of age (corrected age for preterm infants). Summary scores for positive and negative responsiveness, as well as sociability, soothability, and overall activity levels, were derived from behavioral observations by coders who were unaware of the infant's characteristics. The Bates Infant Characteristic Questionnaire was completed by the main care giver and scored on four summary variables: fussy-difficult, unadaptable, dull, and unpredictable. Preterm infants, regardless of the presence or severity of intraventricular hemorrhage, showed less positive responses and less overall activity in response to stimulation. Infants with grade I to II intraventricular hemorrhage were less sociable and more difficult to soothe than full-term control infants. Individual differences in positive, negative, sociability, and soothability were related to the questionnaire scores of fussy-difficult and unadaptability. Both prematurity and degree of intraventricular hemorrhage affect behavioral responsiveness and these individual differences are related to parental reports of the infant's temperament.

The in vivo effect of bilirubin and sulfisoxazole on cerebral oxygen, glucose, and lactate metabolism in newborn piglets.

Bilirubin inhibits in vitro oxidative phosphorylation and glycolysis. This study investigated the in vivo effect of bilirubin on cerebral oxygen, glucose, and lactate uptake in newborn piglets. Seventeen 2- to 4-day-old piglets were divided into three groups and examined as follows: group 1 = control (C); group 2 = control with sulfisoxazole; and group 3 = experimental, given bilirubin with sulfisoxazole. In the experimental group, bilirubin was infused for 4 h. The cerebral bilirubin content in the bilirubin-infused group was 11.0 +/- 1.4 nmol/g of cerebral cortex (mean +/- SEM), consistent with levels found in infants with kernicterus. However, this level of brain bilirubin had no major, acute effects on cerebral uptake of oxygen, glucose, or lactate despite producing lethargy and ataxia which were consistent with bilirubin intoxication. This suggests that mitochondrial changes may not be involved in vivo in acute bilirubin encephalopathy.

The Apgar score revisited: influence of gestational age.

We tested the hypothesis that Apgar scores are in part related to the newborn infant's level of maturity. Seventy-three pregnant women with normal fetuses of gestational age 22 to 42 weeks were studied. Fetal well-being was documented by a prospectively designed recording of pregnancy history, labor complications, and birth outcome, including cord blood pH and base deficit measurements. The 1- and 5-minute Apgar scores were directly related to gestational age. Respiratory efforts, muscle tone, and reflex were the major determinants for a decreasing Apgar score with declining gestational age. We conclude that the 1- and 5-minute Apgar scores are influenced by the infant's level of maturity and that our data may be useful in evaluating the true value of Apgar scores in assessing the fetal and neonatal condition of low birth weight infants.

Bronze baby syndrome. Report of a case.

A newborn female infant suddenly developed a generalized gray-brown discoloration of her skin while receiving phototherapy for hyperbilirubinemia. The discoloration waned over the succeeding weeks. Her serum contained an unknown pigment that had a characteristic absorbance on spectrophotometry. The distinctive findings and some possible causes of the bronze baby syndrome are discussed. The findings are compared to other causes of dusky-hued skin in the neonate. The bronze baby syndrome is usually innocuous but can signal life-threatening disease.