The effect of aminophylline on diaphragm blood flow in the piglet.

The effect of aminophylline on diaphragmatic blood flow was investigated in two groups of newborn piglets. Six animals were studied during spontaneous breathing and seven additional animals were paralyzed and ventilated to assess the effect of aminophylline on blood flow to the nonworking diaphragm. Arterial blood gases and pH, cardiac output, and diaphragmatic blood flow were measured before and 20 min after infusion of 20 mg/kg aminophylline. Blood theophylline concentrations averaged 117 mumols/L (21 micrograms/mL) in both groups of animals. Heart rate increased significantly in all animals. Cardiac output increased significantly only in spontaneously breathing animals. Aminophylline had no effect on blood flow to the costal or crural portions of the diaphragm in either the paralyzed or spontaneously breathing animals.

Bronchopulmonary dysplasia. Survival after prolonged mechanical ventilation.

We reviewed the records of 4778 infants who were admitted to the affiliated intensive care nurseries at the University of Washington in Seattle from Jan 1, 1980, through Dec 31, 1983. We evaluated the outcome for patients with bronchopulmonary dysplasia who required mechanical ventilation and supplemental oxygen for at least six months. Eight (53%) of 15 study patients were alive at 3 years of age. Preselected indexes measured during the first six months of life that were not associated with death before 3 years of age included growth measurements, fraction of inspired oxygen at 6 months of age, mean airway pressure, arterial partial pressure of carbon dioxide, and right ventricular hypertrophy. In contrast, recurrent cyanotic episodes requiring intermittent muscle paralysis or long-term sedation therapy to maintain gas exchange occurred in six of seven nonsurvivors and only one of eight survivors. The survivors have reactive airway disease and recurrent lower respiratory tract infections.

Ventilatory failure during loaded breathing: the role of central neural drive.

Minute ventilation (VE), arterial blood gases, diaphragmatic electromyogram (EMG) activity, centroid frequency (Fc) and peak inspiratory airway pressures (Paw) were measured in five unanesthetized tracheostomized infant monkeys during various intensities of inspiratory resistive loaded breathing (IRL) until either 1) ventilatory failure occurred (failed trial) or 2) normocapnia was sustained for 1 h (successful trial). During successful trials VE and arterial PCO2 (PaCO2) were sustained at base-line levels, and an increase in peak integrated diaphragmatic EMG activity and peak inspiratory Paw occurred. In contrast, during ventilatory failure runs, VE decreased and PaCO2 rose compared with their respective base-line values. The fall in VE occurred secondary to a significant decline in breathing frequency. Tidal volume was sustained at base-line levels during all trials (both successful and failed groups). Inspiratory Paw's and peak moving time average EMG were sustained at elevated levels during ventilatory failure runs, suggesting that the respiratory muscles did not fail as pressure generators. Furthermore, the EMG Fc did not change from base line during either successful or failed trials. These data suggest that peripheral muscle fatigue did not occur, although in the absence of a more direct test of muscle performance, i.e., a force-frequency curve, we cannot rule out the possibility that a component of peripheral failure contributed to our results. Ventilatory failure during severe IRL in the infant monkey was most clearly associated with an alteration in the respiratory center timing mechanism, i.e., such failure was a function of a decline in respiratory frequency.

Hyperosmolality induced by propylene glycol. A complication of silver sulfadiazine therapy.

An 8-month-old male infant was treated with topical silver sulfadiazine for a burn and complicating toxic epidermal necrolysis involving 78% of his total body surface area. Transdermal absorption of propylene glycol from the silver sulfadiazine produced hyperosmolality with an increased osmolal gap. A peak propylene glycol concentration of 1,059 mg/dL was documented, and its osmotic effect was that predicted from its concentration. Our data support either zero-order elimination at a rate of 13.5 mg/dL/hr or first-order elimination with a half-life of 16.9 hours. Elevated concentrations of propylene glycol may have contributed to the patient's cardiorespiratory arrest. The osmolal gap may be used as a screen for suspected propylene glycol intoxication in selected clinical settings.

Alteration of membrane electrical activity in rat myocardial cells following selective laser microbeam irradiation.

Laser microirradiation of neonatal rat (1 to 2-day-old) ventricular cells in tissue culture results in overt changes in contractility. The intracellular study of their ongoing electrical activity prior to, during, and after laser microirradiation demonstrates that definite membrane alteration occurs concomitantly with induced contractile responses. Although all ventricular cells are depolarized by laser microirradiation, the ultimate response elicited seems to differ according to the type of myocardial cell impaled. Typical fibrillation potentials were induced mainly in pacemaker cells.

Argon laser microirradiation of mitochondria in rat myocardial cells in tissue culture. VII. fibrillation in ventricle and auricle cells.

Rat myocardial cells in vitro were irradiated in individual mitochondria with an argon ion laser microbeam. The contractile respone termed fibrillation in single and multicellular groups of both ventricle and auricle cells were compared. Specific correlations were made between fibrillation duration, the number of cells in the group, and the number of times the cells had fibrillated. Correlations were also made for the number of laser shots needed to induce fibrillation and the number of cells in the group. Another set of correlations were made between the pre-irradiation beat frequency and the beat frequency following recovery. Several differences and similarities of the above parameters were detected between auricle and ventricle cells. A comparison of the morphology and ultrastructure of auricle and ventricle cells also revealed significant differences.