Predictive factors of severe postoperative pain in the postanesthesia care unit

I.v. morphine titration (IMT) is widely used in the postanesthesia care unit to achieve pain relief. Numerous factors contribute to variability in postoperative pain or morphine consumption. We analyzed prospectively the pre- and intraoperative predictive factors of severe postoperative pain defined as a dose of IMT >0.15 mg/kg or a failure of IMT.

We assessed the role of preoperative information about pain, medical treatments, and intraoperative events and their role on postoperative pain. After IMT, patients were divided into two groups: severe pain (SP) and nonsevere pain. Data are expressed as mean +/- SD.

Three hundred forty-two patients were included in the study: 200 (58%) in the nonsevere pain group and 142 (42%) in the SP group. Using a univariate analysis, there was no significant difference between groups related to medical or surgical history except for more frequent preoperative treatments in the SP group (P < 0.05). Duration of the surgical procedure and anesthesia were longer in the SP group (P < 0.001). The dose of sufentanil and visual analog scale scores before and at the end of IMT were higher in the SP group (P < 0.001). Using a multivariate analysis, a high dose of intraoperative opioid (sufentanil dose >0.6 microg/kg) (Odds ratio = 2.68, P < 0.001), a general anesthetic procedure (Odd ratio = 3.96, P = 0.03), and the use of preoperative analgesic drugs (Odds ratio = 1.91, P < 0.01) were independent factors associated with severe postoperative pain.

A higher intraoperative dose of sufentanil, general anesthesia, and preoperative treatment with analgesics were significantly associated with severe postoperative pain.