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Biomedical subjects

E F Donovan

Publications and source records attributed to E F Donovan.

At least 55 records · Page 3Linked to original sources
PubMed1985

Perioperative care of the surgical neonate.

This article provides an overview of perinatal physiology and common pathophysiologic events that are likely to complicate the clinical course of neonates requiring surgical procedures. The special needs and problems of the premature newborn are emphasized. References are provided for a more detailed analysis of the normal and abnormal transition from fetus to newborn.

Adaptation, Physiological↗
PubMed1985

Influence of airway pressure waveform on cardiac output during positive pressure ventilation of healthy newborn dogs.

During positive pressure ventilation, increases in mean airway pressure produced by increases in end expiratory pressure are associated with reductions in cardiac output. Mean airway pressure may be increased not only by increasing end expiratory pressure, but also by increasing the inspiratory pressure or the inspiratory to expiratory time ratio. During positive pressure ventilation of 10 healthy newborn dogs, cardiac output and left ventricular dimensions were measured using radioactive microspheres and echocardiography, respectively. Baseline ventilation was produced using the least inspiratory pressure to maintain normocarbia (rate = 50 min-1, inspiratory to expiratory time ratio = 1:3, end expiratory pressure = 2 cm H2O). The mean airway pressure was increased 3-fold by independently changing the airway pressure waveform through increases in inspiratory pressure, inspiratory to expiratory time ratio, or end expiratory pressure. Despite differences in airway pressure waveform, similar reductions in left ventricular dimension, cardiac output, and stroke volume were seen. We conclude that at a given increased mean airway pressure during positive pressure ventilation, the reduction in cardiac output is independent of the airway pressure waveform.

Animals↗
PubMed1983

Transient respiratory difficulty following cesarian delivery.

57 newborn infants delivered by planned, repeat cesarian section were studied to determine the role of surfactant in transient neonatal respiratory distress. 22.8% of the newborn infants studied had transient tachypnea of the newborn. The mean amniotic fluid lecithin-sphingomyelin ratio (L/S) was 2.8 in normal infants and 2.6 in infants with transient tachypnea. The mean gastric aspirate L/S at the time of delivery was 3.0 in the normal infants and 2.7 in infants with transient tachypnea. There were no statistically significant differences in either amniotic fluid L/S or gastric aspirate L/S. Based on these results we speculate that, despite altered lung mechanics in neonates with transient tachypnea, lung maturity as determined by L/S ratio does not differ from that of normal neonates.

Amniotic Fluid↗
PubMed1982

The role of postnatal age and magnesium on parathyroid hormone responses during "exchange" blood transfusion in the newborn period.

One hundred and eight "exchange" blood transfusions were done on 61 newborn infants. Baseline serum PTH concentrations and the PTH rise in response to citrate-induced hypocalcemia were studied. Baseline PTH values increased with postnatal age, particularly after the first three days of life. The acute response of PTH to citrate-induced hypocalcemia appears within ten minutes following the initiation of exchange transfusion and was shortlived in spite of further decline of serum ionized calcium. The dominant effect of postnatal age over gestational age was demonstrated: postnatally older but gestationally less mature infants exhibited greater responsiveness than postnatally younger, but gestationally more mature, infants. The PTH response during exchange transfusion was blunted in hypomagnesemic infants. Since lower serum magnesium concentrations were also present during the first three days of life, a separate effect of serum magnesium concentrations on parathyroid responsiveness cannot be ruled out in this study.

Age Factors↗
PubMed1981

Conduction velocity and EMG power spectrum changes in fatigue of sustained maximal efforts.

The relationship between the electromyographic (EMG) power spectrum and muscle conduction velocity was investigated during both fatiguing and nonfatiguing contractions of the adductor pollicis muscle. Changes in the EMG power spectrum were measured by Fourier transform analysis and by comparing the power in the high (130-238 Hz) and low (20--40 Hz) frequency bands. Changes in conduction velocity were measured during voluntary activity from changes in the muscle mass action potential evoked by periodic maximal shocks to the nerve. This was varied independently either by maintaining a 60-s fatiguing maximal voluntary contraction involving 30--50% loss of force or by changing muscle temperature in the absence of fatigue. Both procedures resulted in similar changes in the power spectrum. However, the change in conduction velocity required to generate equal changes in the EMG was about 10 times greater in the absence of fatigue than those observed during a 60-s maximum contraction initiated at any initial muscle temperature. This suggests that during fatigue of maximal voluntary contractions, factors other than changes in the wave form of individual muscle fiber action potentials must contribute to the observed shift in the total surface EMG frequency components.

Electromyography↗
PubMed1980

Neonatal hypermagnesemia: effect on parathyroid hormone and calcium homeostasis.

Twenty pre-eclamptic mothers treated with MgSO4 and their newborn infants were studied prospectively to determine the clinical and biochemical effects of hypermagnesemia. Maternal serum magnesium concentration rose to 4.4 mg/dl at delivery and was accompanied by a fall in maternal serum calcium concentration during labor. Neonatal serum Mg concentration remained elevated for the first 72 hours of life (mean at 72 hours = 3.0 mg/dl). Serum Mg concentration was higher in premature infants and in babies with birth asphyxia and/or hypotonia. Serum Ca concentration was higher and serum PTH was lower in hypermagnesemic study infants when compared to a retrospectively selected, matched froup of control infants. We speculate that elevated serum Mg values in these infants result in a shift of Ca from bone to plasma, and that elevated Mg and Ca concentrations further suppress neonatal parathyroid function.

Calcium↗
PubMed1978

Urinary phosphate and cyclic AMP excretion following citrate-induced hypocalcemic stimulation of the neonatal parathyroid glands.

Sixteen neonates, ranging in gestational age from 27 to 41 weeks and in postnatal age from birth to 8 days, were evaluated for their renal response to an endogenous PTH stimulus in 22 separate experiments. The PTH stimulus was generated by the decreased serum ionized Ca that accompanies exchange transfusion with citrated blood. The neonates increased their serum PTH from 95.8 +/- 13.1 to 133.9 +/- 15.4 microliterEq/ml (mean +/- SEM) during the transfusion, while increasing their urinary cAMP from 0.77 +/- 0.11 to 1.45 +/- 0.22 nmol/ml, and their urinary P from 12.9 +/- 2.6 to 30.6 +/- 6.1 mg/dl in the four hours following the exchange transfusion. This response was not related to postnatal or gestational age. We speculate that lack of renal responsiveness to PTH does not play a major role in the pathogenesis of early neonatal hypocalcemia.

Citrates↗
PubMed1975

Idiopathic hyperlipoproteinemia in dogs.

Six dogs with hyperlipoproteinemia of undetermined cause had increased serum concentrations of lower density lipoprotein classes, as detected by lipid measurements and lipoprotein electrophoresis. Five of the dogs were Miniature Schnauzers and 1 was of mixed breeding. Signs of disease included abdominal distress (2 dogs), abdominal distress and seizures (2 dogs), and weizures (1 dog). One dog was clinically normal. Feeding of a low-fat diet resulted in alterations of lipoprotein distribution and serum lipid content. In 2 dogs, intravenous (IV) administration of heparin caused shifing of the lipoprotein electrophoretic pattern, indicating activated lipoprotein lipase. These clinical and laboratory findings suggested a syndrome caused by an inherited defect in lipid metabolism.

Animals↗
PubMed1975

Lipids and lipoproteins in normal dogs and in dogs with secondary hyperlipoproteinemia.

Concentrations of serum cholesterol, triglyceride, and free glycerol were neasured, and serum lipoprotein electrophoresis was performed in normal dogs and in dogs with hypothyroidism, diabetes mellitus, and acute pancreatitis. Twelve privately owned dogs and 20 Basset Hounds from a research colony served as normal subjects. Privately owned had higher serum lipid concentrations than did research dogs. On electrophorisis of normal dog serum, lipoprotein bands were detected at the beta, pre-beta, alpha-2, and alpha-1 positions. Hypercholesterolemia was associated with increased intensity of the alpha-2-lipoprotein band, and hypertriglyceridemia occurred with increased lipoprotein at the origin, or the beta or pre-beta positions. Hypothyroid dogs had normal lipid values and lipoprotein electrophoretic patterns, hypercholesterolemia with increased intensity of the alpha-2-lipoprotein band, or hypercholesterolemia and hypertiglyceridemia with prominent beta-, pre-beta, and alpha-2-lipoprotein electrophoretic patterns were changed to near-normal values after levothyroxine administration. Diabetic dogs had increased serum cholesterol and triglyceride content and a predominance of lower density lipoproteins, as detected by electrophoresis. Insulin therapy caused the lipid concentrations to decrease and the electrophoretic pattern to revert to near normal. Dogs with acute pancreatitis had moderately increased serum lipid content and electrophoretic patterns characterized by increased intensity of the beta-lipoprotein band and by altered migration of alpha-1-lipoproteins.

Animals↗