Pain Evaluation of Venous Cannulation to Predict Postoperative Pain

• The investigators will study all adult (>18 years old) patients going through surgery at the site during a defined period of time. Before induction of anesthesia participants will be asked to assess (in VAS units) the pain intensity associated with peripheral venous cannulation. The maximum level of postoperative pain intensity will be recorded in the post-anesthesia care unit.
• After the endpoint of the study, the patient records will be reviewed, and de-identified relevant data be recorded and analyzed in the Statistical Package for the Social Sciences (SPSS) software.
• Sample size assessment: In a previous study patients scoring ≥ 2.0 on venous cannulation assessed their median pain postoperatively at 5.8 VAS units compared with 2.9 in those scoring < 2.0 - corresponding to a difference in maximum postoperative pain intensity of almost three VAS units. To statistically confirm, with unpaired non-parametric tests, 80 % power (β), and 95% probability (1- α), half of that difference (1.5 VAS units) in pain intensity level between patients scoring above or below 2.0 VAS units, respectively, would require 55 patients in each group subjected to the same kind of surgery. With 4 groups of cases and controls 440 patients would need to be included. As the study is strictly observational, 600 patients will be included to make up for possible missing data.
• Statistics: The Mann-Whitney U- test will be used to compare differences in postoperative pain intensity levels, and the Pearson Chi-square test to compare proportions of patients with moderate or severe postoperative pain, in patients differing in pain scores (above or below 2.0 VAS units) on venous cannulation. Logistic regression analysis will be used to adjust for gender and age and to evaluate the predictive ability of proposed method.

Inclusion criteria

• 18-80 years old
• Scheduled for surgery in Halmstad
• Prepared for surgery in the preoperative ward or ward 71 (day-case or direct admittance)

Exclusion criteria

• Inability to handle the Visual Analog Scale
• Hospitalized already before surgery