Depression of respiration by alkalosis and opioid interaction in man was studied in a double blind experiment utilizing changes in the ventilatory response to carbon dioxide. In each of two weekly sessions, control responses were determined before and after infusion of a liter of fluid which consisted of either saline solution as a placebo or 3.3 mEq/kg sodium bicarbonate. The bicarbonate infusion shifted the ventilatory response curve 6.2 torr to the right of, but parallel to, the ventilatory response curve after the saline placebo. Following each infusion, cumulative oxymorphone dose response curves were obtained during isohypercapnia by observing the change in ventilation with each incremental intravenous dose. The two logarithmic dose response curves were parallel. The total dose of 57 μg/kg oxymorphone shifted ventilatory response curves 19 and 16.3 torr to the right of the control response curves after bicarbonate and saline infusions, respectively. These shifts were not significantly different. Similarly, cumulative effects of naloxone given after oxymorphone were studied. A total of 57 μg/kg naloxone reversed 78 and 75% of the oxymorphone depression in the two instances (significant reversal but insignificantly different comparing the results after the two different infusions). Respiratory depression produced by alkalosis and oxymorphone was thus additive. Naloxone effectively antagonized only the component of depression induced by oxymorphone, and modest changes in pH did not alter its action.
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine