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

Abstract

CAN J ANESTH 55: 2 www.cja-jca.org Februar y, 2008 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 (R 2 = 0.45; P < 0.0001). Path analysis showed a direct pathway from preoperative IES scores to lockout interval demands (β = 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.

L’analgésie contrôlée avec patience: vers une meilleure compréhension des comportements d’auto-administration des analgésiques

“…Available evidence from over half a dozen chronic pain studies does suggest that opioid self-administration patterns are quite different for animals with chronic arthritic 15 or neuropathic 16 pain, as compared to control rats, suggesting a distinction between the analgesic and reinforcing effects of opioids. There are virtually no published laboratory studies on analgesic self-administration 17 shows how a more focused approach addresses some of the questions raised by Katz et al 6 regarding the impact of various psychological conditions that affect analgesic self-administration behaviour. Briefly, Shaham and Stewart reported that, in rats who learn to selfadminister heroin, rats who are stressed with mild foot shock, as compared to normal controls, self-administer more heroin and lever press many more times for each subsequent injection (i.e., heroin appears to be more reinforcing in the stressed animal).…”

“…6 décrivent des indicateurs psychométriques qui semblent prédire une fréquence plus élevée de demandes d'ACP de morphine à la suite d'une chirurgie gynécologique. Des analyses secondaires d'une étude clinique antéri-eure ont examiné les associations entre les demandes d'ACP « interdites » cumulatives durant 48 h et la douleur, et entre la consommation de morphine et de nombreux indicateurs psychométriques préopératoires d'affect négatif, comme par exemple l'anxiété et les comportements d'évitement, ou les pensées intrusives concernant la chirurgie prévue.…”

“…4 Despite its apparent simplicity, the PCA paradigm has stimulated extensive inquiry in the form of over 2,700 publications, 1,100 clinical trials, and 250 review articles addressing analgesic pharmacology, medical device technology, and most importantly, the treatment and behaviour of persons in pain. In this issue of the Journal, Katz et al 6 describe psychometric indicators which appear to predict a higher frequency of PCA demands for morphine following gynecological surgery. Secondary analyses from a previous clinical trial 7 examined associations between 48 hr cumulative "locked out" PCA demands and pain, and morphine consumption and several preoperative psychometric indicators of negative affect, such as anxiety and avoidant behaviours, or intrusive thoughts regarding anticipated surgery.…”

“…Secondary analyses from a previous clinical trial 7 examined associations between 48 hr cumulative "locked out" PCA demands and pain, and morphine consumption and several preoperative psychometric indicators of negative affect, such as anxiety and avoidant behaviours, or intrusive thoughts regarding anticipated surgery. 6 Based on evidence that intrusive thoughts (e.g., pain anticipation) impact upon psychological distress and subsequent analgesic demands, Katz et al 6 used path analysis 8 to demonstrate that avoidant behaviours/intrusive thoughts about upcoming surgery were positively correlated with PCA lockout demands. 6 These findings are consistent with, and expand upon, previous study results, such as those from Jamison et al, 9 which suggested significant correlations between PCA dose/demand ratio and preoperative measures of emotional distress.…”

“…6 Based on evidence that intrusive thoughts (e.g., pain anticipation) impact upon psychological distress and subsequent analgesic demands, Katz et al 6 used path analysis 8 to demonstrate that avoidant behaviours/intrusive thoughts about upcoming surgery were positively correlated with PCA lockout demands. 6 These findings are consistent with, and expand upon, previous study results, such as those from Jamison et al, 9 which suggested significant correlations between PCA dose/demand ratio and preoperative measures of emotional distress. Although PCA demands are obviously linked to pain intensity and analgesic consumption, understanding other determinants of PCA lockout demands might explain some of the complexities of pain behaviour.…”