Respiratory depression after morphine in the elderly. A comparison with younger subjects.

The effects of intravenous morphine (10 mg/70 kg) on the ventilatory response to CO2 were studied in two groups of subjects, young (18-29 years) and old (66-85 years), prior to elective surgery. In both groups morphine caused a significant depression of respiration as judged by a reduction in the slope of the CO2 response curve, a reduction in the calculated ventilation at an end tidal CO2 tension of 7.3 kPa, a rise in resting end tidal CO2 and a rise in the CO2 threshold. There were no significant differences between the two groups in the changes produced by the drug, suggesting that acute respiratory depression after a single intravenous injection of morphine is similar in old and young people.