Factors affecting acute pain perception and analgesics consumption in patients undergoing bariatric surgery

Previous studies performed in non-obese patients undergoing elective surgery have revealed that psychological factors may affect postoperative analgesic requirements. The aim of this observational prospective study was to investigate the extent to which psychopathological dimensions, including anxiety, depression and alexithymia, may influence postoperative pain intensity and analgesics consumption using patient-controlled analgesia (PCA) in patients undergoing bariatric surgery.

120 patients, aged 18-60years, with an ASA physical status I-II, undergoing gastric bypass were enrolled. Anxiety and depression Hamilton scales, and Toronto Alexithymia scale, were administered to patients on the day before surgery. General anesthesia was standardized. After awakening, a PCA pump with intravenous tramadol was immediately made available for a 36-hour postoperative analgesia. Visual analog scale at rest (VASr) and after coughing (VASi), and effective PCA requests number were postoperatively recorded. Pearson's correlations, Anova analyses and multiple linear regression were used for statistical purpose.

Positive correlations were found between anxiety, depression, alexithymia and all pain indicators (p<0.01). Analyses of variance showed that anxious (p<0.001), depressed (p<0.001) and alexithymic (p<0.05) patients had high pain indicators. VASr and VASi were predicted by anxiety and depression (p<0.05), but not by alexithymia; effective PCA requests number was predicted by anxiety, depression and alexithymia (p<0.001).

Obese patients with high depression, anxiety and alexithymia levels rated their pain as more intense and required a larger amount of tramadol. Pain perception intensity was predicted by anxiety and depression but not by alexithymia, whereas analgesics consumption was predicted by all the investigated psychopathological dimensions.