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 (β = 0.333, P < 0.05). Serum LDH concentration was strongly associated with greater postoperative pain (β = 0.606, P < 0.001). Alcohol consumption was associated with higher postoperative pain (β = 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.