Marshall Goldstein

The Apgar score revisited: Influence of gestational age

We tested the hypothesis that Apgar scores are in part related to the newborn infants 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 infants 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.

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

ObjectivesTo test the hypothesis that, in newborn piglets, the presence of a tension pneumothorax modifies the cardiovascular responses to hypoxia/hypercarbia. DesignProspective laboratory study. SettingPerinatal cardiovascular research laboratory at a university school of medicine. SubjectsSeven newborn piglets. InterventionsWe 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 ResultsBrain 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. ConclusionsTension 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. (Crit Care Med 1994; 22:1453–1460)

Cerebral Cortical Blood Flow and Oxygen Metabolism in Normocythemic Hyperviscous Newborn Piglets

ABSTRACT: 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 cyroprecipitate, 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.

Effects of chronic fetal hyperinsulinemia on plasma arachidonic acid and prostaglandin concentrations

In adult diabetic subjects and infants of diabetic mothers, hyperglycemia has been associated with increased intravascular thromboxane and decreased prostacyclin production. Because of the association between states of altered insulin concentration and prostaglandin metabolism, we hypothesized that chronic experimentally induced fetal hyperinsulinemia results in perturbations in fetal arachidonic acid and prostaglandin metabolism. Arachidonic acid, thromboxane B2 (the stable breakdown product of thromboxane A2), and 6-keto-prostaglandin F1 alpha (the stable breakdown product of prostacyclin) were determined in the arterial blood of chronically catheterized fetal sheep after 9 to 12 days of continuous insulin (15 U.day-1, n = 7) or placebo (n = 5) infusion. Fetal insulin infusion resulted in fetal hypoglycemia and a reduction in fetal arterial plasma arachidonic acid concentration (p less than 0.01). In addition, the concentration of thromboxane B2 relative to 6-keto-prostaglandin F1 alpha was significantly reduced in the insulin-treated group compared with the placebo-treated group (p less than 0.03). We conclude that fetal hyperinsulinemia in sheep produces perturbations in prostaglandin metabolism with reductions in the plasma arachidonic acid concentration and in the plasma concentration of thromboxane A2 relative to prostacyclin. The hyperinsulinemic-hypoglycemic state in the fetus influences the relative proportion of the vasoconstricting to the vasodilating prostaglandins, thereby potentially modulating fetal vasomotor tone.

Prolonged hyperinsulinemia reduces plasma fatty acid levels in the major lipid groups in fetal sheep

The offspring of women with poorly controlled diabetes have increased total body fat. Experimental fetal hyperinsulinemia has previously been associated with increased fat accumulation in rhesus monkey fetuses and increased lipid content and lipogenesis in rat fetuses. We hypothesized that prolonged fetal hyperinsulinemia would alter plasma total fatty acids and the individual fatty acids in each major lipid group. Fatty acids determined by gas-liquid chromatography were measured in the arterial blood of 12 chronically catheterized fetal sheep after 10 to 12 days of insulin (n = 7) or placebo (n = 5) infusion. Plasma concentrations of insulin were 412 +/- 63 microU/ml and 9 +/- 3 microU/ml (mean +/- SE) in the insulin- and placebo-treated fetal sheep, respectively. Prolonged fetal hyperinsulinemia was associated with lower circulating total fatty acid levels in each lipid class except cholesterol esters. Although the precursor of arachidonic acid, 18:2 (linoleic acid), was not decreased in any lipid class, insulin infusion was associated with reduced arachidonic acid in each lipid class. We conclude that prolonged fetal hyperinsulinemia decreases circulating total fatty acid and the individual fatty acids in each of the major lipid classes, except for the cholesterol esters. We speculate that these reductions in circulating fatty acids represent an insulin-mediated increase in tissue deposition.

1360 THE APGAR SCORE REVISITED: DEVELOPMENTAL PATTERNS IN “OPTIMAL” NEWBORNS

The five objective criteria used in the Apgar score to assess the newborn include four signs (tone, reflex irritability, color, respiratory drive) that depend upon developmental maturity. The immature infant, with typically flaccid muscle tone is penalized by the Apgar method for developmental immaturity. We hypothesized that in nonasphyxiated fetuses, Apgar scores should correlate directly with gestational age (lower scores with decreasing maturity). 62 parturients (gestation: 23-42 weeks) were prospectively enrolled. By objective documentation of pregnancy history, labor complications, fetal heart rate tracings, cord blood pH & BE, their fetuses were judged as normal at the time of delivery. Direct relationship between Apgar scores and gestational age following a linear regression (y=.34x-4.8 at 1′, r=0.82; y=.28x-1.6 at 5′, r=0.77) was observed. Analysis of the total score into components reveals heart rate to be least influenced by maturity. Respiratory effort and muscle tone increase with increasing maturity. Skin color improves with development at the 5′ score. Reflex irritability trends upward but with more variability at 1′ than 5′. These data suggest that 1) the standard Apgar score may not be appropriate for the assessment of fetal well-being in premature infants, 2) scores thought representative of asphyxia in more mature newborns may not represent asphyxia in immature infants, and 3) these normative data are useful in the assessment of fetal status at various levels of maturity.