The aim of the study is to observe if any correlation between Body mass index and VAS values exists in patients who has gone under abdominal surgery.

Group I : Patients with BMI<30 Group II: Patients with BMI between 30 and 34.9 Group III: Patients with BMI between 35 and 39.9 Group IV: Patients with BMI between 40 and 49.9 Group V : Patients with BMI >50

After the end of surgery patients will be extubated and in the recovery room morphine PCA (patient-controlled analgesia) treatment will be started according to their adjusted body weight. When VAS values over 4,10 mg/kg Paracetamol IV will be used as an escape treatment. VAS values and Delivery and Demand of the PCA and additional need for analgesics will be recorded in the first 48 hours.

Inclusion Criteria:

• patients undergoing abdominal surgery and who will be given PCA treatment for postoperative pain.

Exclusion Criteria:

• patients younger than 18 years old, patients with uncompensated diabetes or related polyneuropathy, patients receiving antidepressants or have a diagnosis of depression