What are typical dosage schedules for intravenous PCA-administered opioids?

What are typical dosage schedules for intravenous PCA-administered opioids?

Sample adult dosage schedules for commonly used opi-oid analgesics are noted in Table 72.1. Such schedules are only guidelines and require individual titration from patient to patient. In the elderly, or the patient with severe pulmonary or renal disease, basal rates may need to be eliminated, bolus doses may need to be decreased, and/or lock-out intervals may need to be lengthened. Conversely, in young, healthy patients, or in those tolerant to opioids, the bolus dose and basal rate might need to be increased or the lock-out interval may need to be shortened.

The choice of opioid used depends on many factors including the practitioner’s familiarity with the drug, cost, and availability. Certain clinical situations may dictate the use of one opioid over another. For example, morphine, due to its propensity to release histamine, may not be the first-line drug of choice in the asthmatic patient. Meperidine should not be used routinely in the postoperative period because of its ability to cause tachycardia and because its primary metabolite, normeperidine, lowers the seizure threshold.

Debate exists over the benefits of using a constant, basal rate infusion with PCA. Opponents of its use note the fact that the use of a basal rate defeats the idea behind PCA, that patients only request medication when they need it, while proponents of its use believe that it improves analgesia. In a study involving post-cesarean section patients (Sinatra et al., 1989) the use of a basal rate improved analgesia, but also increased the incidence of nausea. Another study in gynecologic patients (Parker et al., 1992) failed to show any advantage to the use of basal rates. Although it may seem counter-intuitive, the use of a basal infusion has never shown to increase a patient’s ability to sleep in the post-operative period.