Locked out and still knocking: predictors of excessive demands for postoperative intravenous patient-controlled analgesia.

BACKGROUND

Psychosocial factors governing the use of postoperative, intravenous patient-controlled analgesia (PCA) have received little attention in spite of the fact that PCA is the most common modality for managing pain after surgery. The motivation behind requests for analgesia during lockout periods is not known. Unrelieved pain and need for pain medication are obvious reasons but other factors may be involved. The aim of the present study was to predict PCA lockout interval demands based on preoperative psychosocial factors.

METHODS

Approximately one week before major abdominal gynecologic surgery, 117 women completed the impact of events scale (IES) measuring intrusive thoughts and avoidant behaviours. Pain was measured by visual analogue scale at three, six, 12, 24 and 48 hr after surgery. Measures of anxiety and negative affect were obtained 24 and 48 hr after surgery. Cumulative morphine consumption and every PCA demand (drug delivered and not delivered) were downloaded from the PCA pump.

RESULTS

Multiple regression analyses revealed that preoperative intrusive thoughts and avoidant behaviours about the upcoming surgery positively predicted PCA lockout interval demands after controlling for postoperative pain, morphine consumption, anxiety, and negative affect (R2 = 0.45; P < 0.0001). Path analysis showed a direct pathway from preoperative IES scores to lockout interval demands (beta = 0.23, P = 0.002) which was not associated with untreated pain, anxiety, or negative affect.

CONCLUSIONS

Excessive demands for postoperative intravenous- PCA morphine during lockout intervals appear to reflect, in part, poor preoperative adaptation to surgery involving intrusive thoughts and avoidant behaviours about the upcoming surgery.