Pediatric research
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Positive end expiratory pressure (PEEP) is an accepted treatment for children with acute respiratory failure secondary to restrictive lung diseases. Using a simple technique based on open circuit nitrogen washout, we determined the functional residual capacity (FRC) in 25 ventilated children (age 3 wk-10 y) with acute respiratory failure secondary to restrictive lung disease (pulmonary edema, bilateral pneumonia). FRC measured at a physiologic level of PEEP (2-4 cm H2O) was 45.0 +/- 3.6% (mean +/- SEM; range 12-80%) lower than normal predicted values. ⋯ FRC normalized at PEEP levels of 6-18 cm H2O (mean = 11.6), which was up to 200% above the clinically chosen PEEP level. In six children without lung disease who were ventilated at a PEEP level of 2-4 cm H2O, the FRC was within normal range in two, but significantly higher (by 45%) in the other four. We conclude that FRC in ventilated children with acute restrictive lung disease is significantly lower than normal and the clinically chosen PEEP fails to normalize the FRC in most of the cases.
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A model of hypothermic circulatory arrest has been developed in the newborn dog. Ten puppies were anesthetized with halothane, paralyzed, and artificially ventilated with 70% nitrous oxide 30% oxygen to arterial oxygen pressure greater than 8.0 kPa (60 mm Hg), arterial carbon dioxide pressure of 4.4-5.6 kPa (33-42 mm Hg), and arterial pH of 7.35-7.42. Animals were surface cooled to 20 degrees C, after which cardiac arrest was produced with i.v. ⋯ Thereafter, lactate decreased in the 1-h arrested dogs but increased progressively in the other groups. Mean arterial blood pressure returned to baseline (73 mm Hg) by 15 min postarrest, remained stable in the 1-h dogs, but fell at 3 h to 62 and 34 mm Hg in the 1.5- and 2.0-h groups, respectively. No neuropathologic alterations were seen in puppies arrested for 1 h, whereas all puppies arrested for 1.5 or 2 h had varying degrees of cerebral cortical and hippocampal damage.(ABSTRACT TRUNCATED AT 250 WORDS)
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Extracorporeal membrane oxygenation (ECMO) supplies respiratory support to term or near-term infants with respiratory failure. Although infants requiring this therapy may have already sustained significant hypoxia and/or ischemia predisposing them to neurologic injury, the high incidence of neuroimaging abnormalities in the ECMO population raises concerns about the additional neurologic risk associated with the ECMO procedure itself. Our study was undertaken to evaluate the effects of ECMO on the normal neonatal cerebral circulation. ⋯ Neither cerebral blood flow (baseline, 60.2 +/- 23.6; 30 min, 56.1 +/- 18.1; 120 min 56.1 +/- 12.9 mL/100 g/min) nor oxygen metabolism (cerebral oxygen consumption: baseline, 4.48 +/- 1.48; 30 min, 3.86 +/- 1.53; 120 min, 4.10 +/- 1.32 mL/100 g/min and oxygen extraction: baseline, 0.52 +/- 0.09; 30 min, 0.47 +/- 0.14; 120 min, 0.46 +/- 0.14 mL/100 g/min) changed after the initiation of ECMO. Regional and left/right blood flow differences were not noted. These findings suggest that in healthy newborn lambs, initiation of ECMO does not alter cerebral blood flow or oxygen metabolism.
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Carbon dioxide-induced changes in near infrared spectrophotometry recordings were compared with changes in cerebral blood flow estimated by 133Xenon clearance (global cerebral blood flow (infinity)) at serial measurements in 24 mechanically ventilated preterm infants (mean gestational age 30.2 wk). In all infants, three measurements were taken at different arterial carbon dioxide tension levels (mean 4.4 kPa, range 2.1-7.8) obtained by adjustment of the ventilator settings. Mean arterial blood pressure changed spontaneously, whereas arterial oxygen tension was kept within normal range. ⋯ This observation, however, may have been artifactual due to cross-talk between the oxidized cytochrome aa3 and the oxygenated Hb signals, as these signals were closely interrelated in the present experimental design. We suggest that near infrared spectrophotometry may be used for estimation of the cerebral blood volume index/cerebral blood flow-CO2 reactivity within a wide range of arterial carbon dioxide tension. Knowledge of the light path length would put this estimation on a quantitative basis.
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Comparative Study
Evaporative cooling as an adjunct to ice bag use after resuscitation from heat-induced arrest in a primate model.
Heat stroke and other hyperthermia-related crises are serious clinical problems in childhood and adolescence. Rapid cooling is required to reduce morbidity and mortality. A variety of effective cooling methods exist, and some may interfere with monitoring and resuscitation or are not readily available. ⋯ After cardiac arrest and during and after CPR, rectal temperature had declined from a lethal level of 42.2 degrees C to a safe level of 38.5 degrees C within 45 +/- 6 (38-53) min in group I, and within 28 +/- 4 (23-32) min in group II (p less than 0.05). Epidural and esophageal temperatures declined more rapidly than rectal temperature. For critical hyperthermia, we recommend immediate application of ice bags, cold water wetting (sponging), fanning, and head cooling combined when invasive blood cooling (the most effective method) is not immediately available.