Does postoperative delirium limit the use of patient-controlled analgesia in older surgical patients?

Abstract

BACKGROUNDPostoperative pain Is an independent predictor of postoperative delirium. Whether postoperative delirium limits patient-controlled analgesia (PCA) use has not been determined.

Methods: The authors conducted a nested cohort study in older patients undergoing noncardiac surgery and used PCA for postoperative analgesia. Delirium was measured by using the Confusion Assessment Method. The authors computed a structural equation model to determine the effects of pain and opioid consumption on delirium status and the effect of delirium on opioid use.

Results: Of 335 patients, 108 (32.2%) developed delirium on postoperative day (POD) 1, and 120 (35.8%) on POD 2. Postoperative delirium did not limit the use of PCA. Patients with postoperative delirium used more PCA in a 24-h period (POD 2) compared to those without delirium (mean dose of hydromorphone +/- SE adjusted for covariates was 2.24 +/- 0.71 mg vs. 1.25 +/- 0.67 mg, P = 0.02). Despite more opioid use, patients with delirium reported higher Visual Analogue Scale scores than those without delirium (POD 1: mean visual analog scale +/- SE at rest 4.2 +/- 0.23 vs. 3.3 +/- 0.22, P = 0.0051; POD 2: 3.3 +/- 0.23 vs. 2.5 +/- 0.19, P = 0.004). Path coefficients from structural equation model revealed that pain and opioid use affect delirium status, but delirium does not affect subsequent opioid dose.

Conclusions: Postoperative delirium did not limit PCA use. Despite more opioid use, visual analog scale scores were higher in patients with delirium. Future studies on delirium should consider the role of pain and pain management as potential etiologic factors.

Figure 1. Illustrative model of relationships between postoperative opioid use and delirium status

This figure depicts our heuristic model for the association between postoperative delirium and opioid use. In this model, we described that delirium status was represented by the four criteria used to measure the presence of delirium. Our hypotheses were 1) rest pain on postoperative day one affected delirium status on day one, 2) opioid dose on day one affected delirium status on day one, and 3) delirium status on day one did not affect opioid dose on day two.

Figure 2

Shown are the VAS pain scores plotted as mean ± SEM for patients with and without postoperative delirium in the pre- and post-operative periods VAS – visual analog scale * indicates P<0.05