Non-invasive investigation of cerebral metabolism in newborn infants by phosphorus nuclear magnetic resonance spectroscopy

Intracellular metabolism in the brains of seven infants, born at 33-40 weeks' gestation and aged 44 h to 17 days, was studied on fourteen occasions by phosphorus nuclear magnetic resonance spectroscopy (31P NMRS). The characteristic spectral peaks of ATP, phosphocreatine (PCr), phosphodiesters, and inorganic orthophosphate (Pi) were always detected, together with a large peak attributed mainly to ribose-5-phosphate. The ratio of PCr to Pi NMRS signals (which are related to concentration) in one infant thought to have a normal brain was 1.7. In three infants who had severe birth asphyxia the PCr/Pi ratio ranged from 0.2 to 1.0 but increased as their clinical condition improved: infusions of mannitol solution caused a rapid increase in the ratio on four occasions in two of these infants. The PCr/Pi ratio was 1.4 in an infant with congenital cerebral atrophy and 0.7 in an infant with meningitis. Grossly abnormal 31P spectra antedated the detection by ultrasound of large porencephalic cysts in two infants. No systematic changes in intracellular pH (calculated from the chemical shift of the Pi resonance) were observed: the mean value for all observations was 7.2 +/- SD 0.1 (n = 14).

Hypoxic-ischemic encephalopathy in the newborn

Many term newborns suffer some degree of perinatal asphyxia, but few become permanently brain damaged as a consequence, The newborns at risk for major neurologic handicaps have evidence of derangement in many organs, depressed cerebral function at birth that continues for days or weeks, and in many cases, convulsions soon after birth. The pathophysiologic mechanism of brain damage in hypoxic-ischemic encephalopathy remains contested, and no specific therapy is clearly beneficial. The immediate treatment of the asphyxiated term newborn requires attention to the derangements in multiple organ systems and the use of anticonvulsants when indicated.

Gastric aspirate lecithin/sphingomyelin ratio and neonatal breathing difficulties

Gastric aspirate lecithin/sphingomyelin (L/S) ratios in newborn infants at risk to develop breathing difficulties were studied. 51.6% of the infants with an immature L/S value developed clinical respiratory distress syndrome (RDS). In the RDS infants, the gastric aspirate L/S value was immature in 94.1%. The gastric aspirate L/S values of the infants with transient tachypnea or perinatal asphyxia did not differ significantly from those of the healthy infants. The severity of RDS correlated inversely to the gastric aspirate L/S value (r = -0.63, p less than 0.001, n = 17). The gastric aspirate L/S value can be used in differential diagnosis between RDS and other neonatal breathing difficulties. It is also a predictor of the severity of the developing RDS.

Simple estimate of creatinine clearance from plasma creatinine in neonates

Thirteen newborn infants, 8 preterm and 5 term, with either mild or serious neonatal asphyxia were studied. From the first 24 hours of life to day 13, glomerular filtration rate (GFR) estimated by creatinine clearance was compared with the values obtained using Schwartz's formula: GFR (ml/min per 1.73 m2) = 0.55 x length (cm)/plasma creatinine (mg/100 ml). Both in term and preterm infants, values of formula-calculated creatinine clearance were slightly higher than values obtained by the classical method; nevertheless the data show significant correlations, respectively r = 0.867 and r = 0.795 (P less than 0.001). This formula provides an adequate estimation of neonatal creatinine clearance (a marker for GFR) directly from plasma creatinine provided that body length is taken into consideration. The necessity for urine collection and the associated problems are thus obviated. The simplicity of Schwartz's formula permits easy monitoring of renal function, especially in neonatal asphyxia in which the risk of developing renal failure is great.

Effects of asphyxia on renal function in the newborn piglet

This investigation was undertaken to determine the nature of acute alterations in renal function following the production of hypoxemia, hypercarbia, and acidosis in newborn piglets 6-96 hr of age. After completion of the surgical procedure piglets were allowed to recover from the effects of anesthesia. When respiratory dead space was increased arterial oxygen tension decreased whereas arterial carbon dioxide tension and hydrogen ion concentration increased. There was little change in glomerular filtration rate. Total renal blood flow decreased and renal vascular resistance increased significantly (504 +/- 78 mm Hg/liter/mm/m2 to 1422 +/- 504). There was no change in distribution of intrarenal blood flow. Sodium excretion and urinary flow rate demonstrated significant parallel increases following the increase in dead space. Plasma renin concentration increased from 67 to 110 ng/ml.

Absence of phosphatidylglycerol (PG) in respiratory distress syndrome in the newborn. Study of the minor surfactant phospholipids in newborns

Phosphatidylglycerol (PG) was absent from lung effluent in 41 infants with respiratory distress syndrome of the newborn (RDS), whereas effluent from healthy control subjects of similar gestational age contained this phospholipid (4.9 +/- 2.4% of lipidphosphorus (P), n = 32). Control infants of 28 weeks of gestation or less with various respiratory disturbances other than RDS also had low PG (0.2 +/- 0.2% of lipid-P, n = 5). In RDS surfactant complex often could be isolated from the airways using differential and density gradient centrifugation. The material thus obtained had prominent phosphatidylinositol (PI) (13.6 +/- 2.8% of lipid-P, n = 6), but no PG. Of those 18 infants who had such surfactant even in the early stages of RDS, 13 were 35 weeks of gestation or more, 3 were offspring of diabetic mothers, and 2 had severe perinatal asphyxia. In healthy control subjects PG sometimes appeared first within an hour of birth, but in RDS PG did not appear until recovery from RDS. In RDS type II (transient tachypnea of the newborn) PG in lung effluent also was abnormally low (1.3 +/- 0.6% of lipid-P, n = 5) and PI was correspondingly prominent (9.7 +/- 3.6% of lipid-P, n = 5), indicating immaturity of surfactant similar to RDS. Surfactant with PG and PI has superior surface-active properties compared to that containing PI, but no PG. Surfactant without PG does not seem to stabilize the alveoli of the newborn as well as does surfactant with PG. The failure of PG appearance following birth therefore may precipitate RDS, especially beyond 35 weeks of gestation.

The acid-base and biochemical characteristics of intrapartum fetal asphyxia

The maternal and fetal acid-base, lactate, and pyruvate characteristics during the course of labor and at delivery were studied in 124 patients delivered of an infant with evidence of metabolic acidosis at delivery. This metabolic acidosis is principally caused by hyperlactatemia resulting from the tissue oxygen debt accompanying fetal asphyxia. Hypoxemia was one mechanism contributing to this fetal asphyxia and tissue oxygen debt. This evidence of fetal asphyxia developed during the last half and principally during the last two hours of the intrapartum period. Acid-base assessment of fetal blood with identification of a metabolic acidosis will provide an accurate objective diagnosis of intrapartum fetal asphyxia.

Changes in tissue glycogen of recovering asphyxiated newborn monkeys

Newborn rhesus monkeys were used to investigate the relation between the duration of total asphyxia and the magnitude of the postasphyctic cerebral glycogen hyper-deposition response. The latter has been observed to occur following episodes of total asphyxia lasting 12.5 min and to be maximal at 12 h into the recovery period. The changes in glycogen contents of other vital organs were also studied. A minimum duration of 9 min of total asphyxia was required for the first elicitation of the cerebral glycogen hyperdeposition response. The magnitude of the response once elicited did not vary whatever the duration of the asphyxia beyond 9 and up to 30 min. During the actual episodes of total asphyxia, the glycogen content of the brain diminished more rapidly and completely than did that of kidney or heart. The hepatic, pulmonary and muscle glycogen contents did not change significantly either during asphyxia or during the recovery period.

Water and electrolyte abnormalities in the human brain after severe intrapartum asphyxia

In a necropsy study of brain water, sodium, and potassium concentrations is newborn infants, abnormalities were found in 10 out of 16 cases who were severely asphyxiated at birth. It is concluded that, although frank cerebral cortical necrosis is not often recognizable in perinatal deaths, early anoxic-ischaemic cerebral damage is frequent after intrapartum asphyxia. Diffuse cerebral swelling was associated with marked electrolyte disturbances and may be regarded as a feature of anoxic-ischaemic encephalopathy in asphyxiated newborn infants.