Variables of patient-controlled analgesia. 1. Bolus size.

The efficacy of a range of demand doses of morphine for patient-controlled analgesia was studied. Patients who self-administered the smallest dose (0.5 mg) were frequently unable to achieve good pain control; patients who received the largest dose (2 mg) had a high incidence of ventilatory depression. A dose of 1 mg was the best increment under the conditions of this study but the relationship between increment and lockout interval requires consideration.