Biomedical subjects

Alastair A Hutchison

Publications and source records attributed to Alastair A Hutchison.

4 recordsLinked to original sources

PubMed2006

Serum caffeine concentrations in preterm neonates.

Caffeine therapy reduces apnea of prematurity, promotes successful extubation from invasive positive-pressure ventilation, and decreases the incidence of bronchopulmonary dysplasia. The recommended dosing for caffeine is a loading dose of 20 mg/kg followed by a 5 mg/kg/d maintenance dose. However, controversy exists about the optimal dosing regimen and data on serum caffeine concentrations in extremely immature infants are scant. We determined serum caffeine concentrations approximately 7 days after starting therapy with a 20 or 25 mg/kg loading dose and a 6 mg/kg/d maintenance dose in 154 infants with a mean gestational age of 29 weeks. The 25th to 75th percentile range for the serum caffeine concentrations with the two dosing regimens was equivalent, approximately 18 to 23 mg/L. Within the first 14 postnatal days, the serum caffeine concentrations were not dependent on postmenstrual age, weight, or postnatal age, and were in a range that is safe and therapeutic. This latter observation remained valid over the ranges of clinical and laboratory assessments of renal and hepatic functions that are usually found in practice. Routine measurement of steady-state serum caffeine concentrations in infants 24 to 35 weeks gestational age is not required in the absence of ongoing apnea/hypopnea or signs compatible with toxicity.

Apnea↗

PubMed2002

Laryngeal muscle activities with cerebral hypoxia-ischemia in newborn lambs.

This study tested the hypotheses that (1) acute cerebral hypoxia-ischemia changes laryngeal adductor, laryngeal abductor, and diaphragmatic activities, resulting in central apnea with laryngeal closure; and (2) these laryngeal muscle activities act to maintain absolute lung volume. The respiratory pattern was determined in three asphyxiated, awake preterm lambs after cesarean section birth and in 12 awake, term lambs, with normal lung function, after induction of acute cerebral hypoxia-ischemia by occlusion of the brachiocephalic artery. Electrocorticogram activity, flow, volume, electromyograms of laryngeal abductor and adductor muscles and diaphragm, and, in the term lambs, trans-upper airway pressure and carotid blood flow were recorded. With either preterm birth asphyxia or induced acute cerebral hypoxia-ischemia, minute ventilation initially increased, and then hypopnea occurred. During the hypopnea, laryngeal adductor activity was prominent, accompanied by an increased upper airway pressure and a maintained/raised absolute lung volume. Thus, when acute hypoxia-ischemia limited to the upper body is induced in lambs with normal lung function, expiratory laryngeal adduction with closure of the upper airway occurs and likely functions to aid autoresuscitation.

Animals↗

PubMed2002

Maternal smoking and partial exchange transfusion for neonatal polycythemia.

The aim of this study was to determine if maternal smoking was associated with an increased need for partial exchange transfusion for symptomatic polycythemia in term neonates. The study population consisted of 8,961 term neonates, of whom 28.7% were categorized as babies born to mothers who smoked. The incidence of partial exchange transfusion was determined in neonates whose mothers smoked and in neonates of nonsmokers. Partial exchange transfusion was performed in 41 neonates of mothers who smoked (1.59%; n = 2,572) versus 41 neonates of nonsmokers (0.64%; n = 6,389) ( p = 0.000). In babies requiring a partial exchange transfusion birth weights were 2,908 +/- 659 g (smokers) versus 3,474 +/- 770 g, (nonsmokers) ( p <0.001) and the babies born to mothers who smoked were 9 times more likely to be small-for-gestational age (SGA) and 5 times less likely to be large-for-gestational age (LGA). Term neonates of mothers who smoke during pregnancy require a partial exchange transfusion for neonatal polycythemia approximately two and a half times as often as neonates of mothers who do not smoke.

Case-Control Studies↗

PubMed2002

Cerebral cortical respiratory-related evoked potentials elicited by inspiratory occlusion in lambs.

Respiratory-related evoked potentials (RREP) elicited by inspiratory mechanical loads have been recorded in humans. Early RREP peaks were hypothesized to be generated by activation of neurons in the somatosensory cortex. An animal model was developed to test this hypothesis in chronically instrumented, awake, spontaneously breathing lambs. Electrocorticogram (ECoG) was recorded bilaterally with ball electrodes on the dural surface over the somatosensory region. Inspiratory occlusions were presented through a face mask or endotracheal tube as interruptions of inspiration. Occlusion-elicited evoked potentials were obtained by computer-signal averaging the ECoG activity. A short-latency positive peak was observed bilaterally in the averaged occlusion-elicited evoked potentials in all animals breathing with the facemask and 5 of 8 lambs with the endotracheal tube. Postmortem identification of the electrode location demonstrated that the ECoG was recorded in the caudal-lateral portion of the somatosensory cortex. These results demonstrate that inspiratory occlusion elicits an evoked potential in the somatosensory cortical region of awake, spontaneously breathing lambs. The lamb cortical RREP is similar to human RREP.

Air Pressure↗