Effect of Daytime Variation on Postoperative Hyperalgesia Induced by Opioids

Study Overview
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Brief Summary
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To explore the effect of daytime variation on postoperative hyperalgesia induced by opioids. Patients receiving endoscopy surgery under general anesthesia during 08:00-12:00(morning group, n=30) and 14:00-18:00(afternoon group, n=30) using remifentanil for anesthesia maintenance were respectively included. Postoperative hyperalgesia at PACU and 24 hours after surgery were assessed through mechanical pain measurement. Comparative analysis of postoperative hyperalgesia levels, pain and analgesic requirements between morning group and afternoon group were performed.

Official Title
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Effect of Daytime Variation on Postoperative Hyperalgesia Induced by Opioids

Conditions
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Postoperative Hyperalgesia

Intervention / Treatment
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* Drug: Remifentanil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists classification I-II Abdominal endoscopy surgery Estimated surgery duration 1-2h Right handedness Voluntarily receive postoperative intravenous controlled analgesia Exclusion Criteria: Heavy smoking or alcohol dependence Puerpera or lactation women History of chronic pain Analgesic use within one month before surgery Allergy to opioids Can not follow with the study procedure

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Morning group<br>Surgery performed during 08:00 to 12:00 | Drug: Remifentanil<br>* Remifentanil was used for maintenance of anesthesia.<br>|
| Afternoon group<br>Surgery performed during 14:00 to 18:00 | Drug: Remifentanil<br>* Remifentanil was used for maintenance of anesthesia.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative hyperalgesia when discharged from postanesthesia care unit | The ratio of pressure pain threshold when discharged from PACU compare to before surgery | from the 30 minutes before the surgery until to the time when discharged from postanesthesia care unit, assessed up to about 2 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative hyperalgesia at 24 hours after surgery | The ratio of pressure pain threshold at 24 hours after surgery compare to before surgery | from the 30 minutes before the surgery until to 24 hours after surgery | 
| Postoperative pain intensity | Pain intensity was assessed by numerical rating scale (0-10, 0 represents painless; 10 represents intolerable pain) | from the time when the surgery was completed until to 24 hours after surgery | 
| Postoperative analgesic requirements | Analgesic requirements was assessed by recording the volume of patient controlled analgesia pump | from the time when the surgery was completed until to 24 hours after surgery | 
| Plasma concentration of remifentanil and sufentanil | Determined by Elisa test | from 30 minutes before the surgery until to the time after stop infusion of remifentanil, assessed up to about 2 hours | 
| Activity of plasma nonspecific esterase | Determined by laboratory detection | from 30 minutes before the surgery until to the time after stop infusion of remifentanil, , assessed up to about 2 hours |