The effects on ventilation of ketorolac in comparison with morphine

We have compared the effect on ventilation of ketorolac, an injectable non-steroidal analgesic, with that of morphine in a randomized, double-blind, cross-over study, using two doses of ketorolac (10 and 90 mg i.m.) and one of morphine (10 mg i.m.). The effect on ventilation was measured with a CO2 rebreathing technique. As a measure of the effect we studied the increase in PETCO2 (CO2 shift) that caused a respiratory minute volume (RMV) equal to the RMV in the control period at 8 kPa PETCO2. Ketorolac caused insignificant CO2 shifts of about 0.10 kPa, while morphine caused a significant CO2 shift of 0.86 kPa. We conclude that ketorolac in analgesic and supra-analgesic doses has no effect on the ventilatory response to CO2 under circumstances in which significant effects are seen with morphine.