Journal of Applied Physiology, Vol 72, Issue 2 410-415, Copyright © 1992 by American Physiological Society
Metabolic and cardiorespiratory effects of doxapram and theophylline in sleeping newborn piglets
A. Cote, P. W. Blanchard and B. Meehan
Jeremy Rill Clinical and Research Centre for Sudden Infant Death Syndrome and Apnea, Department of Pediatrics, Montreal Children's Hospital-Research Institute, McGill University, Montreal, Quebec, Canada.
To evaluate the contribution of a change in metabolic rate to ventilatory
changes after the administration of respiratory stimulants, we studied the
effect of two respiratory stimulants, doxapram and theophylline, on
ventilation and metabolic rate during sleep in piglets. Metabolic rate (O2
consumption and CO2 production) was measured in a metabolic chamber, and
alveolar ventilation (VA) was derived from arterial PCO2 and CO2
production. We studied the animals during a baseline period and for 2 h
after the administration of theophylline or doxapram. With doxapram, there
was no change in VA, metabolic rate, or arterial PCO2. In contrast, with
theophylline, VA increased [20 +/- 14% (SD), P less than 0.003] as a result
of both an increased metabolic rate and hyperventilation. Doxapram,
however, increased mean blood pressure (from 67 +/- 11 to 75 +/- 13 mmHg, P
less than 0.005), whereas theophylline did not result in blood pressure
changes. In summary, during quiet sleep, doxapram, unlike theophylline,
does not stimulate either respiration or metabolic rate. We speculate that
the previous reports of increased ventilation after the administration of
doxapram are due to the general stimulation of activity in the awake state,
an effect not seen during sleep.
