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Biomedical subjects

D C Shannon

Publications and source records attributed to D C Shannon.

At least 109 records · Page 6Linked to original sources
PubMed1977

The role of the QT interval in the sudden infant death syndrome.

To evaluate the role of QT interval prolongation in the genesis of the sudden infant death syndrome (SIDS), the post-resuscitation electrocardiograms of 21 aborted SIDS infants were reviewed. The infants had been found apneic, cyanotic, limp and unresponsive during sleep and required vigorous physical stimulation and mouth-to-mouth resuscitation. Three subsequently experienced repeat similar episodes from which they could not be resuscitated. Extensive studies eliminated all "known" etiologies for death. The QT intervals of these infants were compared to age and sex matched normal infants as well as to established normal values in the literature; in both the aborted and the subsequent actual SIDS infants, the QT intervals were not significantly different from those of the normal population. Thus, we conclude that QT intervals prolongation does not play a major role in the genesis of the aborted SIDS.

Electrocardiography↗
PubMed1977

Evaluation of neonatal intracranial hemorrhage by computerized tomography.

Computerized tomographic (CT) brain scan was performed on 28 infants with unexplained cardiorespiratory and neurologic deterioration and bloody lumbar cerebrospinal spinal fluid. Fourteen of 20 with intraventricular hemorrhage (IVH) died; the six infants with lesser degrees of IVH survived. Significant subarachnoid hemorrhage (SAH) was demonstrable in three infants and three had negative scans despite bloody CSF. We have found that CT scans provide useful information about the size and extent of neonatal IVH and distinguished it from SAH. It also confirms the diagnosis of post-hemorrhagic hydrocephalus in these infants. Continued use of the CT scan will help us to understand the natural history and the effects of neonatal intracranial hemorrhage among the survivors of intensive care.

Cerebral Hemorrhage↗
PubMed1977

Infantile lobar hyperinflation: expectant treatment.

Arterial blood gases and regional lung function, measured with a 133xenon technique, were used to evalute the physiological defects and follow the natural history of 16 infants with lobar hyperinflation ("emphysema"). Hypoxemia was due to V/Q inequality at rest. Worsening of hypoxemia (mean Pao2 delta--26 mm Hg) with crying was due to shunting as a consequence of cessation of ventilation in the involved lobe. Surgery was necessary in three patients. Two deaths were caused by bronchopulmonary dysplasia after respiratory distress syndrome (RDS). In 12 of 14 infants, lung function was normal between the ages of 5 days and 1 year. Pediatrics, 59:1012-1018, 1977, LOBAR EMPHYSEMA, BLOOD GASES, REGIONAL LUNG FUNCTION.

Blood Gas Analysis↗
PubMed1977

Pulmonary edema associated with croup and epiglottitis.

Two children, ages 9 and 2 1/2 years, with clinical diagnoses of laryngotracheitis (croup) and epiglottis, respectively, developed florid pulmonary edema without evidence of cardiac enlargement. Both children responded to vigorous therapy, which included endotracheal intubation, mechanical ventilation with high oxygen concentrations and positive end expiratory pressure, diuretics, and support of the intravascular volume with colloid infusions. Swan-Ganz catheterization was performed in the child with epiglottitis to elucidate any hemodynamic malfunction. Pulmonary artery occluded pressure was found to be normal. We postulate that pulmonary edema may be the result of any of three major physiologic alterations: alveolar hypoxia, increased alveolar-capillary transmural pressure gradient, and a catechol-mediated shift of blood volume from the systemic to the pulmonary circulation. These alterations acting in concert would increase the volume of blood presented to the pulmonary capillaries, the pore size in those capillaries, and the hydrostatic pressure gradient promoting transduation. Failure of pulmonary lymphatics to effectively clear this fluid would result in pulmonary edema. Although pulmonary edema associated with acute upper airway obstruction is unusual, physicians should be altered to its possible appearance and the need for early and vigorous therapeutic measures.

Airway Obstruction↗
PubMed1977

Pediatricians' attitudes affecting decision-making in defective newborns.

A questionnaire designed to identify the factors that influence the resolution of ethical dilemmas was returned by 230 (57% of the total) Massachusetts pediatricians. The decision to recommend surgery for an infant with Down's syndrome with duodenal atresia when the parents had refused surgery was influenced by religious affiliation (P less than .01), religious activity (P less than .04), and sex (P=.05). Of those favoring surgery, 40.2% would pursue a court order. The decision to recommend surgery for an infant with severe meningomyelocele when the parents' position was not stated was influenced by age (P less than .01), religious activity (P less than .02), and specialization (P less than .008). When the parents' wishes were expressed, the majority of the pediatricians modified their decision in accord with these wishes. In response to general ethical questions, 79.6% of all pediatricians thought that parents should have the right to withold consent for surgery. Equal numbers thought that psychosocial reasons justified witholding lifesaving procedures. Among a variety of factors, they thought that willingness of the parents to care for the child would influence the decision to take heroic measures. There were 90.4% who thought that ethics should be part of medical education; 55.7% indicated this need throughout their careers.

Adult↗
PubMed1976

Asthma in children.

Explore the source record for details and available documents.

Adrenal Cortex Hormones↗
PubMed1976

Central hypoventilation during quiet sleep in two infants.

Expired ventilation (VE), tidal volume (VT), frequency (f), and alveolar PCO2 (PACO2) were examined in six normal infants at 41 to 52 weeks post-conceptional age and in two infants who were apneic at birth. Their response to breathing 5% carbon dioxide in air and to 100% oxygen in quiet sleep were compared to those in rapid eye movement (REM) sleep. VE in normal infants was 259 ml/kg/min in REM and 200.2 ml/kg/min in quiet sleep with the difference being due to decreased carbon dioxide production and to decreased dead space. VE increased 34.4 ml/kg/min/mm Hg of PCO2 elevation with 5% carbon dioxide breathing during REM and was not significantly different during quiet sleep. During oxygen breathing VE fell by 32.7% at 30 seconds before increasing again. In the affected infants, VE and PACO2 during REM at 1 and 4 months were normal. At 1 month, during quiet sleep, each infant became apneic and PACO2 rose 9 and 8 mm Hg/min respectively. At this time mechanical ventilation was begun. At 4 months, during quiet sleep, VE was 0.064 and 0.063 ml/kg/min at PACO2 of 66 mm Hg in each infant. The change was due entirely to a decrease in VT to 2.3 and 2.5 ml/kg. At this time 5% carbon dioxide breathing given during normal ventilation in REM produced an abrupt fall in VT to 2.0 and 2.2 ml/kg with no change in frequency. Oxygen breathing during REM at one month had no effect but at 4 months produced apnea requiring mechanical ventilation after one minute. The findings suggest that the ventilatory response to carbon dioxide is (1) important in initiation of extrauterine ventilation and (2) in sustaining ventilation particularly in quiet sleep. It is not necessary in sustaining ventilation awake or in REM sleep and it represents a balance between the stimulatory and depressant effects of carbon dioxide on the central nervous system.

Apnea↗
PubMed1976

Chemoreceptor function and sleep state in apnea.

Resting ventilation and ventilatory responses to 100% oxygen and to 5% carbon dioxide in air were measured in REM and non-REM sleep in post-neonatal infants. Normal controls were compared to infants with prolonged apnea and to siblings of sudden infant death victims. No significant differences in ventilatory responses were found between the groups. We conclude that apnea may occur in infants whose central and peripheral chemoreceptor activity is normal while they are breathing.

Apnea↗
PubMed1975

Percutaneous catheterization of the radial artery in the critically ill neonate.

Percutaneous catheterization of the radial artery appears to be a simple and safe alternative to catheterization of the umbilical artery for monitoring critically ill neonates. This avoids the serious and potentially fatal complications associated with use of the umbilical arterial catheter, and it is also applicable to monitoring of neonates in whom the umbilical artery is no longer patent. We observed no serious sequelae in cannulation of the radial artery and think that the technique should be used more widely.

Arm↗
PubMed1975

The afferent vagus and regulation of breathing in response to inhaled CO2 in awake newborn lambs.

Changes in steady state minute ventilation, tidal volume and frequency were determined in unanesthetized lambs before and after bilateral cervical vagotomy while breathing 3, 6, and 9% CO2 in 20% O2 balance N2. The slope of delta VE/delta PaCO2 fell from 0.068 to 0.033 while frequency response depended on intact vagi. Electrical stimulation of the cut proximal vagus (after bilateral vagotomy) restored CO2 responsiveness to control values. From these observations, it may be concluded that the afferent vagus is involved in the control of ventilation during hypercapnia and helps to modulate ventilatory frequency by inhibiting tidal volume.

Animals↗
PubMed1975

The pediatric pneumogram: a new method for detecting and quantitating apnea in infants.

A clinically useful diagnostic method has been developed for detecting and quantitating periods of apnea in pediatric patients. This procedure, called the pediatric pneumogram, permits the continuous recording on magnetic tape, for periods of up to 13 hours, of the respiratory pattern of infants utilizing an impedance technique. This test has been employed successfully in a variety of infants to evaluate respiratory activity and has permitted the objective documentation of apneic and cyanotic episodes, as well as an assessment of the eff ectiveness of therapy.

Apnea↗
PubMed1975

Studies on the pathophysiology of encephalopathy in Reye's syndrome; Hyperammonemia in Reye's syndrome.

The initial acid-base status of eight survivors of Reye's syndrome was characterized by acute respiratory alkalosis (Pco2=32 mm Hg; Hco3-=22.0 mEq/liter) while that of eight children who died was associated with metabolic acidosis as well (HCO3-=10.0 mEg/liter). Arterial-internal jugular venous ammonia concentration differences on day 1 (299 mg/100 ml) and day 2 (90 mg/100 ml) reflected cerebral uptake of ammonia while those on days 3 and 4 (-43 and -55 mg/100 ml) demonstrated cerebral release. Arterial blood hyperammonemia can be detoxified safely in the brain as long as the levels do not exceed approximately 300mug/100 ml. Beyond that level lactic acidosis is observed, particularly in cerebral venous drainage. Arterial blood hyperammonemia was also related to the extent of alveolar hyperventilation. These findings are very similar to those seen in experimental hyperammonemia and support the concept that neurotoxicity in children with Reye's syndrome is at least partly due to impaired oxidative metabolism secondary to hyperammonemia.

Acid-Base Imbalance↗
PubMed1975

Prevention of apnea and bradycardia in low-birthweight infants.

The efficacy of theophylline in preventing severe apnea was evaluated in 17 low-birthweight infants (mean weight, 1,400 gm). Apnea was detected and accurately quantified by 13-hour pneumogram recordings and correlated with serum theophylline levels. Nursing observations coupled with on-line alarm systems detected only 39% of severe apneic episodes as compared to the pneumogram recording technique. Theophylline in six hourly oral doses(1.5 to 4.0 mg/kg) yielded two-hour serum concentrations of 6.6 to 11.0 mug/ml which completely controlled apneic spells exceeding 20 seconds in duration and markedly reduced 10- 19-second apneic episodes and any resultant bradycardia. At these serum levels, toxicity was not observed. Therapy with theophylline should be instituted at a dose of 2 to 3 mg/kg every six hours and the optimum therapeutic dose should be individualized as determined by objective quantitation of apnea and serum theophylline concentration.

Apnea↗
PubMed1975

Edema of the pulmonary interstitium in infants and children.

Ten infants and children with respiratory failure, receiving standard maintenance water requirements, were treated on 13 occasions with intravenously given furosemide (1 to 2 mg/kg) because of continued impairment of oxygenation despite conventional therapy. Pulmonary auscultation and radiographs were normal or typical of the primary diagnosis. After a five-fold increase in urine output the mean Po2 rose from 61 mm Hg at a mean FiO2 of 0.7 to 140 mm Hg at an FiO2 of 0.65. The Pco2 decreased from 46 to 38 mm Hg. Interstitial pulmonary edema in these patients can be related to both their lung disease and impaired water tolerance during ventilatory therapy.

Adolescent↗