Bruce G. Nickerson

Association between prenatal cocaine exposure and sudden infant death syndrome

REFERENCES 1. Acute asthma [Editorial]. Lancet 1986;t:13l-2. 2. Geelhoed GC, Landau LI, Le Sou~f PN. Predictive value of oxygen saturation in emergency evatuaton of asthmatic children. Br Med J 1988;295:297-8. 3. Godfrey S, KamburoffPL, Nairn JR. Spirometry, lung volume and airway resistance in normal children aged 5 to 18 years. Br J Dis Chest 1970;64:15-24. 4. Centor RM, Yarbrough B, Wood JP. Inability to predict relapse in acute asthma. N Engl J Mcd 1984;310:577-80. 5. Rose CC, Murphy JG, Schwartz JS. Performance of an index predicting the response of patients with acute bronchial asthma to intensive emergency department treatment. N Engl J Med 1984;310:573-7. 6. Kelsen SG, Kelsen DP, Fleegler BF, Jones RC, Rodman T. Emergency room assessment and treatment of patients with acute asthma. Am J Med 1978;64:622-8. 7. Roca J, Ramis LI, Rodriguez-Rolsin R, Ballester E, Montserrat JM, Wagner PD. Serial relationships between ventilationperfusion inequality and spirometry in acute severe asthma requiring hospitalization. Am Rev Respir Dis 1988; 137:1055-61.

Oral theophylline and diuretics improve pulmonary mechanics in infants with bronchopulmonary dysplasia

We studied the effects of orally administered theophylline and diuretics (chlorothiazide and spironolactone) on pulmonary mechanics in 16 infants with bronchopulmonary dysplasia. Their gestational age (mean +/- SD) was 28.5 +/- 3.4 weeks, and postnatal age at the time of study 19.5 +/- 10.7 weeks. The infants were randomized to two groups. Group 1 received successively placebo, theophylline, and theophylline plus diuretics; Group 2 received theophylline, placebo, and placebo plus diuretics on successive 4-day periods. Pulmonary function was measured before beginning the study (baseline) and at the end of each 4-day period. No significant changes in pulmonary function were noted after treatment with placebo. After treatment with theophylline, dynamic compliance (Cdyn) increased from baseline (mean +/- SD) 0.075 +/- 0.017 to 0.091 +/- 0.028 mL/cm H2O/cm (P less than 0.01), airway resistance (Raw) decreased from 67.19 +/- 36.71 to 41.44 +/- 22.50 cm H2O/L/sec (P less than 0.001), maximal expiratory flow at functional residual capacity (VmaxFRC) increased from 0.261 +/- 0.240 to 0.357 +/- 0.299 thoracic gas volume (TGV)/sec (P less than 0.01), and time constant decreased from 0.312 +/- 0.224 to 0.275 +/- 0.247 sec (P less than 0.02). After treatment with combined placebo and diuretics, Cdyn increased to 0.103 +/- 0.023 mL/cm H2O/cm (P less than 0.05), Raw decreased to 31.76 +/- 24.90 cm H2O/L/sec (P less than 0.001), VmaxFRC increased to 0.638 +/- 0.595 TGV/sec (P less than 0.02), and time constant decreased to 0.180 +/- 0.141 sec (P less than 0.05). After treatment with combined theophylline and diuretics, Cdyn increased to 0.118 +/- 0.017 mL/cm H2O/cm (P less than 0.001), Raw decreased to 35.98 +/- 25.85 cm H2O/L/sec (P less than 0.02), VmaxFRC increased to 0.479 +/- 0.377 TGV/sec (P less than 0.02), and time constant decreased to 0.180 +/- 0.137 sec (P less than 0.01). We conclude that theophylline and diuretics have additive effects on the improvement of pulmonary function in infants with bronchopulmonary dysplasia.

Continuous transcutaneous oxygen and carbon dioxide monitoring in the pediatric ICU.

The transcutaneous partial pressures of carbon dioxide (PtcCO2) and oxygen (PtcO2) were measured with heated electrodes in 18 hemodynamically stable pediatric ICU patients and these data were compared to simultaneously measured arterial oxygen and carbon dioxide tensions. There was a significant degree of correlation (p < 0.001) between the skin surface CO2 and O2 and their corresponding arterial tensions. These data defined values for PtcCO2 and PtcO2 indices in the pediatric patient without cardiovascular complications as PtcCO2 index = 1.6 ± 0.2 and the PtcO2 index = 0.84 ± 0.18 (PtcCO2 index = PtcCO2/PaCO2 and PtcO2 index = PtcO2/PaO2). The authors found the monitoring of skin surface gases a reliable technique to monitor arterial gas tension in hemodynamically stable patients.

Improving pulmonary function does not decrease oxygen consumption in infants with bronchopulmonary dysplasia

To determine whether the high oxygen consumption VO2 in infants with bronchopulmonary dysplasia (BPD) is caused by increased mechanical power of breathing, and if improvement of pulmonary mechanics would reduce mechanical power of breathing and VO2 we gave 16 infants with oxygen-dependent BPD at 19.5 +/- 10.7 (mean +/- SD) weeks of age placebo, theophylline, and orally administered diuretics or theophylline plus diuretics. Pulmonary mechanics, mechanical power of breathing, and VO2 were measured at the beginning and end of each study period. In the placebo group, all infants had elevated VO2 (7.4 +/- 1.4 mL/kg/min) and carbon dioxide production (6.6 +/- 1.2 mL/kg/min), increased airway resistance (59 +/- 30 cm H2O/L/sec), decreased dynamic compliance (0.073 +/- 0.024 mL/cm H2O/cm), increase respiratory rate (52 +/- 11), and increased mechanical power of breathing (2.22 +/- 1.05 kg.cm/kg/min). Treatment with theophylline, diuretics, and theophylline plus diuretics resulted in a significant improvement in pulmonary mechanics and mechanical power of breathing, but not in VO2. These results suggest that the increased VO2 in infants with BPD is not secondary to increased mechanical power of breathing.

Inadequate erythroid response to hypoxia in cystic fibrosis.

An increase in hemoglobin concentration characterizes the normal compensatory response to chronic tissue hypoxia. We observed no such increase in 42 chronically hypoxic patients with cystic fibrosis, in whom the mean concentration was 12.6 gm/dl; one third of the patients were anemic. Compared with patients with cyanotic heart disease, patients with cystic fibrosis did not have a compensatory increase in P50 or 2,3-diphosphoglycerate. Despite anemia, erythropoietin levels in patients with cystic fibrosis were not significantly different from normal control values. The growth of colony-forming units-erythroid in patients with cystic fibrosis was similar to that in control subjects, and there was no inhibition of growth with the addition of autologous serum. Erythropoietin sensitivity, determined by measuring the CFUe dose response curve, was normal in both patients and controls. Results of iron studies were consistent with iron deficiency in the majority of patients. Impaired absorption of iron was observed in six of 13 iron-deficient patients with cystic fibrosis. An inverse correlation between erythrocyte sedimentation rate and peak serum iron was obtained during the iron absorption study. Eight patients who underwent a therapeutic trial of iron demonstrated a 1.8 gm/dl rise in hemoglobin concentration. Two patients with previously documented iron malabsorption responded to parenteral iron therapy after failure to respond to oral supplementation. These studies demonstrate that patients with cystic fibrosis not only have an impaired erythroid response to hypoxia, but are frequently anemic. Their inadequate erythroid response to hypoxia results in part from disturbances in erythropoietin regulation and iron availability.