Association Of μ-opioid Receptor Gene Polymorphism (A118G) With Variations In Sufentanil Consumption For Analgesia After Abdominal Surgery

ObjectiveTo observe the impact ofμ-opioid receptor gene polymorphism(A118G)on postoperative patient control analgesia with sufentanil.To provide insight into the mechanisms involved in the interindividual differences and predict the response toμOR manipulation and allow opioid analgesic regimens to be tailored to individuals' genetic makeups.MethodsOne hundred and twenty-four Chinese male patients undergoing abdominal surgeries in the first hospital of China Medical University were included in the study. The exclusion criteria included a history of allergy to sufentanile,alcohol or substance abuse,use of psychotropic medications,morbid obesity,chronic pain and a poor grasp of the use of a PCA device.The patients were classified according to the American Society of Anesthesiologists(ASA)physical statusⅠorⅡ.None of the patients used analgesics pre-operatively.General endotracheal anaesthesia was induced using 4ug/kg fentanyl,2mg/kg propofol 0.1mg/kg vecuronium.Anaesthesia was maintained using 1.3MAC isoflurane or seveflurane.Blood samples(2ml)were collected from participants and were stored in EDTA tube in -20℃refrigerator.Just before the closure of peritoneal,0.04 ug/kg of sufentanil was given intravenously and PCA was used.The neuromuscular blockade was reversed,and the patient was extubated at the end of surgery.Until they became alert enough to use the PCA pump,patients were asked whether they needed pain medication every 10-15 min in the post-anaesthesia care unit. The sufentanil solution provided in the PCA pump contained 100 ml of normal saline and 200 mg of sufentanil.The pump was set to deliver a0.04ug/kg bolus of sufentanil solution with a lockout time of 10 min and a maximum dose of 24ug within one-hour period without a background infusion.When the maximum permitted dose of sufentanil was reached and the patient still complained of significant post-operative pain[NRS＞50]for 30 min,dolatin was prescribed for rescue pain control,and the patient was later excluded from the study.Overdosage was avoided by limiting the total dose administered within a given period of time.The amount of PCA-delivered sufentanil was recorded at 3,6,24 and 48 h after the operation.PCA was started immediately the patients were sufficiently alert to use it in the post-anaesthesia care unit,and was discontinued 48 h after the operation.Pain at rest was assessed using a 100mm NRS with a range of 0-100,with 'no pain' as zero and 'worst possible pain' as ten.The purpose of the study,NRS questionnaires and usage of the PCA device were explained during an interview with the patient the day before surgery.The NRS scores for pain were taken on the morning of surgery before the operation(as baseline).Pain was measured as resting pain.Pain scores were recorded at 30-min intervals in the postanaesthesia care unit and then re-assessed at 3,6,24and 48 h after the completion of the operation.Patients rated their nausea on a four-point scale(0,no nausea;1,mild nausea;2,moderate nausea;3,severe nausea).Vomiting was assessed as events occurring in the first 24 h.Sedation was assessed using the Ramsey sedation score(0, awake;6,unresponsive to strong,painful stimuli).The patients were monitored closely to prevent sufentanil overdose.The respiratory rate(RR)and levels of consciousness were assessed at regular intervals.Adverse effects of sufentanil were recorded. Screening for single nucleotide polymorphisms of the genes encoding MORs.Whole blood samples were employed for DNA isolation using the TianGen RelaxGene DNA extract box.We used two primers to amplify part of exon 1 of the OPRM1 gene containing the forward primer(5'-GGTCAACTTGTCCCACTTAGATCGC-3')with a single nucleotide substitution(underlined in sequence),which creates a restriction site for the enzyme BstUI when the Gl18 allele is present and reverse primer (5'-AATCACATACATGACCAGGAAGTTT-3').Polymerase chain reaction was performed on 100 ng genomic DNA isolated from blood samples in a total volume of 25 B1 at a final concentration of 10ram Tris-HC1,50mm KC1,1.5mmMgC12,100/zm each dNTP,and 0.025 U/B1 E-Taq polymerase(Eurogentec,Li6ge,Belgium)in the presence of 7.5 pmol of primers.Denaturation was 3 min at 94~C,followed by 38 cycles of amplification with denaturation for 30 s at 94℃,annealing for 1 min at 62℃, and extension for 1 min at 72℃,with a final extension for 10 min.A 8-μl polymerase chain reaction sample was analyzed on a 2%agarose gel.Amplified OPRM1 products were digested with the restriction enzyme BstUI(New England Biolabs,Beverly,MA) according to the recommendation of the manufacturer.Each sample was analyzed on a 2%agarose gel,stained with ethidium bromide,and visualized by an ultraviolet transilluminator.The value are reported as mean±SD.Differences in body,weight,height,age, and consumed morphine from the PCA device between the different genotypes were tested using analysis of variance for one factor(one-way ANOVA)for each variant (AA,AG,GG).The Kruskal-Wallis test was used to compare the side-effects from sufentanil.P＜0.05 was considered to be statistically significant.Results一,The blood samples were sequenced for genotypes:wild-type A118 homozygous (AA 66.1%),mutant heterozygous(AG 30.6%)and mutant G118 homozygous(GG 3.2%).There were no statistically significant differences(P＞0.05)with regard to age, weight,height,ASA,duration of operation,consumption of fentanyl and preoperation MMS score.二,Compared with group AA,sufentanil consumption in group AG at 3h,6h postoperatively increases significantly(P value is 0.002,0.001respectively).Compared with group AA,sufentanil consumption in group GG at 6h,24h postoperatively increases significantly(P value is 0.020,0.022respectively).Compared with group AG, sufentanil consumption in group GG at 24h postoperatively increases significantly(P = 0.022).三,There were no statistically significant differences(P＞0.05)with regard to NRS among groups.And The Ramsey score does not differ significantly at 6h,24h postoperatively.There were no statistically significant differences(P＞0.05)with regard to nausa,vomiting and respiratory depression.Conclusion1.μ-opioid receptor gene polymorphism(A118G)decrease the effect of postoperative patient control analgesia with sufentanil and increase the sufentanil consumption during the early postoperative period2.μ-opioid receptor gene polymorphism(A118G)does not increase the sideeffects of sufentanil PCA though it decreases its analgesic effect during the carly postoperative period.