Influence of 0.1 minimum alveolar concentration of sevoflurane, desflurane and isoflurane on dynamic ventilatory response to hypercapnia in humans |
| |
Authors: | van den Elsen M; Sarton E; Teppema L; Berkenbosch A; Dahan A |
| |
Institution: | Departments of Anesthesiology and Physiology, Leiden University Medical Centre, Leiden, The Netherlands |
| |
Abstract: | To assess the effects and site of action of a sub-anaesthetic concentration
of isoflurane, desflurane and sevoflurane (0.1 minimum alveolar
concentration (MAC)) on respiratory control, we measured the ventilatory
response to square wave changes in PE1CO2 against a background of normoxia.
Using the computer steered "end-tidal forcing system", 2 min of steady
state ventilation were followed by a step increase in PE1CO2 (1-1.5 kPa).
This level was maintained for 8 min, followed by a step decrease to the
original value for another 8 min. Each hypercapnic response was separated
into a fast, peripheral component and a slow, central component,
characterized by a time constant, carbon dioxide sensitivity, time delay
and off-set. We studied 25 healthy volunteers; they performed 2-3 studies
without and 2- 3 studies during inhalation of the anaesthetic agent. Level
of sedation was scored using a subjective seven-point scale from 0 (= alert
and awake) to 6 (unrousable). In the isoflurane (16 subjects, 33 control,
37 drug studies) and sevoflurane (15 subjects, 40 control, 41 drug studies)
studies, peripheral carbon dioxide sensitivity was reduced by approximately
45% and approximately 27% (ANOVA, P < 0.05 vs control), respectively,
without affecting central carbon dioxide sensitivity or apnoeic threshold.
In the desflurane study (16 subjects, 36 control, 37 drug studies), no
significant effect was observed for any of the variables measured. A
significant relation was observed between sedation score and change from
control in central carbon dioxide sensitivities in the isoflurane and
desflurane studies and in the change in the ratio peripheral carbon dioxide
sensitivity over total carbon dioxide sensitivity in the sevoflurane
studies. At the highest level of sedation observed (score 3-arousal state
comparable with "light sleep"--in three subjects) these latter variables
differed significantly from those in the other observed sedation levels
(scores 1 and 2-a state of drowsiness). We conclude that 0.1 MAC of
isoflurane and sevoflurane depressed the peripheral chemoreflex loop,
without affecting the central chemoreflex loop. Desflurane at the same MAC
showed no effect on peripheral and central carbon dioxide sensitivity. When
the level of sedation was considered, our data suggested that at levels of
sedation comparable with sleep, a depressive effect of all three
anaesthetics was observed on the central chemoreflex loop.
|
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|