VENTILATORY RESPONSE TO HYPOXIA IN HUMANS - INFLUENCES OF SUBANESTHETIC DESFLURANE

Background: At low dose, the halogenated anesthetic agents halothane, isoflurane, and enflurane depress the ventilatory response to isocapni c hypoxia in humans. In the the influence of subanesthetic desflurane (0.1 minimum alveolar concentration [MAC]) on the isocapnic hypoxic ve ntilatory response was assessed in healthy volunteers during normocapn ia and hypercapnia. Methods: A single hypoxic ventilatory response was obtained at each of 4 target end-tidal partial pressure of oxygen con centrations: 75, 53, 44, and 38 mmHg, before and during 0.1 MAC desflu rane administration. Fourteen subjects were tested at a normal end-tid al partial pressure of carbon dioxide (43 mmHg), with 9 subjects teste d at an end-tidal carbon dioxide concentration of 49 mmHg (hypercapnia ). The hypoxic sensitivity (S) was computed as the slope of the linear regression of inspired minute ventilation (V-I) on (100 - SpO2), Valu es are mean +/- SE. Results: Sensitivity was unaffected by desflurane during normocapnia (control: S = 0.45 +/- 0.07 1 . min(-1) . %(-1) vs. 0.1 MAC desflurane: S = 0.43 +/- 0.09 1 . min(-1) . %(-1)). With hype rcapnia S decreased by 30% during desflurane inhalation (control: S = 0.74 +/- 0.09 1 . min(-1) . %(-1) vs. 0.1 MAC desflurane: S = 0.53 +/- 0.06 1 . min(-1) . %(-1); P < 0.05). Conclusions: On the basis of the data, subanesthetic desflurane has no detectable effect on the normoc apnic hypoxic ventilatory response sensitivity. However, the carbon di oxide-induced augmentation of the hypoxic response was reduced. This i ndicates that subanesthetic desflurane affects the chemoreceptors at t he carotid bodies.