Patient-controlled analgesia with nitrous oxide in cancer pain.

We tested a new nitrous oxide (N2O) delivery system to explore its usefulness in patient-controlled analgesia. Six patients with uncontrolled cancer-related pain were studied. Patients could give themselves inhalations of a fixed 50%/50% mixture of N2O and oxygen via mouthpiece or face mask. This therapy supplemented other available modalities, principally long-acting oral morphine. We found this strategy to be environmentally safe, well accepted by patients and staff, and effective in relieving pain. Ambient concentrations of N2O were measured and suggested that environmental exposure to caregivers was minimal and safe. No problems were encountered with family and staff acceptance of this modality. We suggest that this method may be a useful addition to pain control measures in cancer patients, and merits further study.