Preoperative Pain Sensitivity: A Feasible Way To Predict Patients' Responses During Intubation And Skin Incision

Introduction Recent studies have shown that pain sensitivity(pain threshold and pain tolerance)which varies widely from individual to individual,can predict postoperative pain and analgesic consumption after surgery.However,until recently,the correlation between preoperative pain sensitivity and analgesic consumption during anesthesia has not been investigated.Objective The goal of this research was to evaluate whether preoperative electricity pain sensitivity testing is predictive of patients' responses during anesthetic intubation and skin incision.Methods Sixty-five women(ASAⅠ-Ⅱ)aged 20～65,undergoing elective abdominal surgery requiring at least a 10-cm-long skin incision were studied. We measured the pain threshold and tolerance to electrical stimulation of the skin(foot)preoperatively.A State-Trait Anxiety Inventory was used to assess patients' anxiety before surgeries.No sedatives or analgesic drugs were given prior to anesthesia induction.General anesthesia was induced with intravenous fentanyl(3μg/kg,injected for 30s)and a TCI of propofol set at 4μg/ml for tracheal intubation.Heart rate(HR)and mean arterial pressure(MAP)were recorded before induction and fentanyl injection,and before and 3 min after tracheal intubation.After intubation,fentanyl was given every 30min,and the effect site concentration of propofol was adjusted according to the change of haemodynamics in order to maintain appropriate sedative depth(BIS 40-50).Mean arterial pressure(MAP)and heart rate(HR)were recorded 3min before and after intubation and skin incision.Results Changes of MAP and HR before and after intubation significantly related with preoperative pain tolerance(r_map=—0.901,r_hr=—0.83, P＜0.05);In contrast to pain tolerance,pain threshold was not correlated with the changes of MAP and HR.Besides intubation,there was a marked correlation between changes of MAP and HR before and after skin incision and pain tolerance(r_map=—0.85,r_hr=—0.82,P＜0.05);however pain threshold was not correlated with the changes of MAP and HR.Patients' anxiety did not relate with pain threshold and tolerance(P＞0.05)either.Conclusion It is wildly accepted that excessive use of analgesia would not only lead to a lot of complications,such as acute opioid tolerance,urinary retention and so on,but also result in postoperative chronic pain.Our research indicated that it may be a quick and easy way to avoid abusing analgesia and postsurgical pain by assessment of preoperative pain sensitivity.The reason why patients' mental status before surgery was not correlated with pain threshold and tolerance may due to the patients not sufficiently knowing their diseases.In a word,we have concluded that preoperative electricity pain assessment may be a predictor of analgesic consumption during intubation and skin incision.And in the future,we should also pay more attention to patients' mental status.