Association of Body Mass Index and Serum Markers of Tissue Damage with Postoperative Pain. The Role of Lactate Dehydrogenase for Postoperative Pain Prediction

Objectives. i) To analyze the association of body mass index (BMI) and some serum tissue damage markers with postoperative pain. ii) To establish a biochemical marker cutoff point able to predict moderate to severe postoperative pain. Design. Cross-sectional study. Subjects. Ninety-six adult male patients from Southern Spain (55 +/- 13 years old) who underwent an inguinal hernioplasty. Methods. Postoperative pain (eight hours after surgery) was assessed through a visual analog scale (VAS). Moderate to severe pain was defined as a VAS > 50 mm. BMI was calculated and medication, alcohol consumption, and smoking habit registered. Eight hours after surgery, some serum markers such as fibrinogen, lactate dehydrogenase (LDH), C-reactive protein, cortisol, creatine kinase, glutamic-pyruvic, glutamic oxaloacetic, and gamma-glutamyltransferase transaminases were determined by standard procedures. Results. After adjusting for potential confounders, BMI was not associated with postoperative pain (P> 0.05). Serum fibrinogen was associated with greater postoperative pain (beta= 0.333, P< 0.05). Serum LDH concentration was strongly associated with greater postoperative pain (beta= 0.606, P< 0.001). Alcohol consumption was associated with higher postoperative pain (beta= 0.212, P< 0.05). No associations were observed regarding age, tobacco consumption, and the rest of serum markers studied. Serum LDH concentration was able to discriminate between presence/absence of moderate to severe postoperative pain (receiver operating characteristic area under the curve = 0.655, P <= 0.01). An LDH concentration >204 IU/L was associated with a three-times increased odds ratio of moderate to severe postoperative pain. Conclusions. Contrary to expectations, greater BMI was not associated with higher postoperative pain. Notwithstanding, the assessment of serum LDH might provide useful information to predict moderate to severe postoperative pain.