Relationship between preoperative pain sensitivity and stress response and analgesic drug consumption during operation

Objective To observe the relationships between preoperative pain sensitivity and stress response and analgesic drug consumption during operation. Methods Pain sensitivity in seventy-seven patients undergoing selective laparotomy was measured at 1 d before the operation, and the total intravenous anesthesia was carried out during the operation. The pain threshold, pain tolerance threshold and operation time were observed and recorded, and the propofol dosage from induction to 4 min after intubation and from skin incision to exploration were observed. The remifentanil dosage within 4 min after intubation, within 4 min after skin incision, within 4 min after exploration and during operation and the changes of mean arterial pressure and heart rate at different time were recorded, then the relationships between the pain threshold and pain tolerance threshold and the indexes mentioned above were analyzed by Pearson Correlation Analysis. Results The mean pain threshold of patients was (1.6 ± 0.6) mA, and the pain tolerance threshold was (3.7 ± 1.0) mA in this group, with (78.6 ± 12.3) min of mean operation time. The correlation analysis showed that the pain tolerance threshold was negatively related to the propofol dosage from induction to 4 min after intubation and from skin incision to exploration and the remifentanil consumption within 4 min after intubation, within 4 min after skin incision, within 4 min of exploration and during operation, with no relationships to the pain threshold. The MAP and HR values at intubation, skin incision, exploration, intraoperative 30 min and at the end of operation were negatively related to pain tolerance threshold, with no relationships to the pain threshold. Conclusion The preoperative pain tolerance threshold shows negative correlations to stress response and analgesic drug consumption during operation, not to pain threshold. Key words: Pain sensitivity; Pain threshold; Stress response; Analgesia; Propofol