Association Of IL-1B And IL-1RN Gene Polymorphism With Fentanyl Intravenous Analgesic Effect

Background and ObjectiveFentanyl is a synthetic opioid analgesic with potent and rapid analgesic effect, which is commonly used in clinical postoperative intravenous analgesic. Interleukin-1 beta (IL-1β) and its endogenous IL-1 receptor antagonist (IL-1ra) play an important role in inflammatory response and in pain modulation. In the early of surgery, pain is caused by nerve injury, latter is caused by inflammatory reaction, which will last for 121β48 h. As a pro-inflammatory cytokine, IL-1βhas been shown to induce inflammatory reactions in the surgical site, and plays a majoy role in increasing hyperalgesia. Opioids, such as fentanyl, can reduce the generation of IL-1βand reduce pain. It has recently been shown that gene polymorphisms of the IL-1βand/or IL-lra may account for variation in the production of these cytokines, which may account for difference in pain sensitivity and postoperative analgesic requirement, we conducted this study to observe the impact of IL-1βand IL-lra gene polymorphism on fentanyl effect for intravenous analgesia. The present study provides an important foundation and theoretical evidence for individualization of medication in the pain treatment. Materials and Methods1. Patient ProfileTotal two hundred and twenty-four subjects, aged 20-50 yr, within±20% of ideal body weight, and having an American Society of Anesthesiologists (ASA) physical status of I orⅡ, Han nationality, Henan province, scheduled for selective abdominal total hysterectomy or myomectomy with general anesthesia were enrolled in this study. Exclusion criteria included the following:known history of alcohol or drug abuse, diabetes mellitus, significant cardiovascular disease, hepatic or renal dysfunction, psychiatric disease, chronic analgesic use, pregnancy or nursing. Subjects who have consumed drugs known to inhibit or induce the expression of IL-1βor IL-1ra in two weeks were also excluded. The study design was approved by Institutional Ethics Committee of Zhengzhou University. The subjects were divided into three or five groups according to the genotypes.2. Anesthetic Procedure and Postoperative Pain AssessmentPatients were not given premedication. When they went into operating room, blood pressure, electrocardiography and pulse oximetry were monitored. Then an intravenous cannula was inserted into a forearm vein by which a standardized general anesthesia technique was used for all patients. Midazolam, remifentanil and propofol was injected intravenously as general anesthesia induced drug. Neuromuscular block drug was administered intravenously with atracurium. When musle relaxed, patients were intubated, and mechanical ventilation was adjusted to maintain end-tidal CO2 between 35 and 40 mmHg. To maintain muscle relaxation, atracurium was administered in repeated boluses. Remifentanil and propofol were infused intravenously to maintain anesthesia during operation. Neuromuscular blockade was reversed by neostigmine and atropine at the end of the surgery. Patients were extubated if they awake and breathe spontaneously adequate tidal volume. Patients were assessed the immediate postoperative pain by a handheld slide rule-type visual analog scale (VAS) with values from 0 (no pain) to 10 mm (unbearable pain) when they were conscious and able to talk. Fentanyl,20 ug/5 min, was given intravenously for>3. For VAS score≤3, patients received fentanyl immediately by patient-controlled intravenous analgesia (PCIA) administered intravenously.PCIA with fentanyl was provided for adequate analgesia postoperatively as soon as the patient's VAS score exceeded 3. The analgesic solution in the PCA pump (6300 CADD-Legacy, USA), was made up by fentanyl,1 mg, and droperidol,5 mg, in 100 ml saline. The program of the PCIA pump was set as cotext infusion rate 0.5 ml/h, lockout time 5 min,2 ml bolus of fentanyl solution per time, and maximal fentanyl infusion limit rate 145μg/h. The fentanyl dose delivered could be recorded by the pump automatically.3. Assessment of fentanyl analgesic effectPostoperative pain was assessed by the VAS at rest during PCIA in the ward. VAS score≤3 was defined as satisfactory analgesia. Some patients were excluded from the analysis when an alternative analgesic was chosen to establish pain control with VAS score> 3, even under the maximum limit dose of fentanyl. The data for the VAS, fentanyl consumption and occurrence of any adverse effects in the first and second 24h after operatiion were recorded.4. Genotyping for IL-1B and IL-1RNGenomic DNA was extracted from whole blood samples which had been taken by a conventional phenol-chloroform method. Purified genomic DNA was stored at-70℃until use. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used for genotyping IL-1B-511C>T. Polymerase chain reaction (PCR) followed by electophoresis on a 2% agarose gel stained with 0.1% ethidium bromide. The results for each genotype were confirmed in randomly selected individuals by direct sequence analysis.5. Statistical analysisSPSS 13.0 software was used for statistical analyses. Data for numerical variables were reported as mean±S.D. Statistical analysis of the genotype distribution and allele frequency of the IL-1ra and IL-1βgenes polymorphism was carried out byχ2-tests and Pearson correlation coefficients.The chi-square test was used to verify Hardy-Weinberg equilibrium. IL-1β, IL-1ra and their combinations, were analyzed by ANOVA, and nonparametric Wilcoxon and Kruskal-Wallis tests. Data for fentanyl dose delivered via PCIA were analysed for the groups by one-way ANOVA with post-hoc analysis. The incidences of any adverse effects were analyzed using Chi-square test or Fisher exact test. The level of significance was determined as P<0.05.Results1. General informationIn total,224 women were included. The VAS score immediately after surgery was 5.6±1.7. At 24 h after surgery, it was 2.2±0.9. The fentanyl consumption was 349.6±203.4μg and 189.3±108.1μg in the postoperative first and second 24 h, respectively. The incidence of postoperative nausea and vomiting was 25.8%. The incidences of pruritus and mild sedation in our study were 0.45% and 1.8%, respectively.2. Distribution of IL-1B-511C>T and IL-1RN alleleThe overall frequency of IL-1B-511T allele in gynecologic patients was 48.4%. The allele frequency was in Hardy-Weinberg equilibrium (P>0.05), which indicates that the patient pool was likely representative of the population being studied. The allelic frequency of IL-1B-511T was similar to that reported in the Chinese Han Population (48.8%), Japanese (41.4%) (P>0.05). IL-1RN alleles detected in patients with gynecological surgery wereⅠ,Ⅱ,ⅢandⅣ.Each genotype frequency of IL-1RNⅠ/Ⅰ,IL-1RNⅠ/Ⅱ, IL-1RNⅡ/Ⅱ, IL-1RNⅠ/Ⅲand IL-1RNⅠ/Ⅲis 93.8%, 2.7%,1.8%,1.3% and0.4%。3. Association of IL-1B-511C>T polymorphism with fentanyl analgesic effectPatients were divided into three genotypes, CC, CT and TT, according to the genotype of IL-1B-511C>T. There were no significant differences in general information among the three genotype groups (P>0.05). No statistical differences in postoperative VAS pain scores and fentanyl consumption at 24 h were detected across genotypes (P>0.05). There was no significant difference in incidences of adverse events among the different genotype groups (P>0.05), either.4. Association of IL-1RN polymorphism with fentanyl analgesic effectPatients were divided into five genotypes,ⅠⅠ,ⅠⅡ,ⅡⅡ,ⅠⅢandⅠⅣ, according to the genotype of IL-1RN. There were no significant differences in general information among the four genotype groups (P>0.05). No statistical differences in postoperative VAS pain scores and fentanyl consumption at 24 h were detected across genotypes (P>0.05). There was no significant difference in incidences of adverse events among the different genotype groups (P>0.05), either.Conclusions1. The frequency of IL-1B-511T allele in gynecologic patients is 48.4%. Frequency of IL-1RN allele variation in gynecologic surgery patients is 4%.2. IL-1B-511C>T and IL-1RN VNRT polymorphisms are not associated with fentanyl analgesic effect. It is not a genetic marker that can affect the fentanyl analgesic effect in gynecologic patients.3. There is no significant relation between adverse effects of fentanyl and IL-1B-511 C> T or IL-1RN VNRT polymorphysms.