Predictors Of Postoperative Pain Research Articles

Chronic pelvic pain: An underrecognised perioperative consideration

Chronic pelvic pain (CPP) is a prevalent disorder amongst women. The physiology of CPP is attributed to various neurophysiological mechanisms and endometriosis, adenomyosis, chronic infection and functional disorders such as irritable bowel syndrome or interstitial cystitis are all diseases which fall under the umbrella term of CPP. CPP and its associated multitude of causes can affect perioperative care through several mechanisms. Patients with CPP may be more likely to experience significant pain in the perioperative setting and preoperative pain can be a predictor of post-operative pain. Thus, optimisation of CPP prior to the perioperative period is an important consideration. Currently limited and conflicting evidence exists regarding the peri-operative pharmacological analgesia. The various aetiologies of CPP and patient medical history result in the inability to generalise one analgesic regime. Areas of further research includes neuromodulation techniques, genomic and proteomic biomarker studies and the applicability of artificial intelligence.

Predictors of postoperative pain six months after breast surgery

Breast cancer, with a high prevalence and survival rate, leads to long-term complications. A major sequel is acute or chronic postoperative pain, and we investigated the possible relationship with clinical and psychological variables. Patients undergoing breast surgery filled out the loneliness (ULS-8) and depression (HADS) questionnaires. Patients rated their pain intensity with the Numerical Rating Scale (0–10, NRS) two days, seven days, and six months after surgery. Of 124 patients, the mean age was 45.86 years old, and the pain scores on the second and seventh postoperative days were 5.33 and 3.57, respectively. Sixth-month pain was significantly correlated with the acute scores with a mean of 3.27; and in the multivariate analysis, it was significantly associated with preoperative pain (p-value = 0.007), self-reported loneliness (p-value = 0.010), and adjuvant radiotherapy (p-value = 0.004). In conclusion, loneliness may be a risk factor for postoperative pain in breast surgery.

Risk factors for moderate-to-severe postoperative pain after percutaneous nephrolithotomy: a retrospective cohort study

Percutaneous nephrolithotomy (PCNL) is a minimally invasive procedure for removing renal calculi, while a large number of patients experience acute moderate-to-severe pain despite the analgesia provided. This study aimed to explore the risk factors for postoperative pain after PCNL, which may provide a novel perspective to refine the enhanced recovery after surgery (ERAS) program and to improve clinical outcomes. The clinical data of 331 patients who underwent PCNL in our hospital from September 2020 to February 2021 were retrospectively analyzed. The pain intensity was assessed every 4 h until 24 h post-surgery. According to the visual analog scale (VAS) score, patients were divided into two groups: mild or no pain group (VAS score, 0–3) and moderate-to-severe pain group (VAS score, 4–10). The pre-, peri-, and post-operative data were collected and analyzed. The indicators with statistically significant differences were selected, and multivariate logistic regression analysis was employed to determine the risk factors for postoperative pain after PCNL. Among 331 patients, 221 patients had moderate-to-severe pain and the incidence rate was 66.77%. Multivariate logistic regression analysis showed that the independent risk factors for moderate-to-severe pain after PCNL were the diameter of the renal calculus (odds ratio (OR) = 6.23, 95% confidence interval (CI) 2.50–15.56, P = 0.001), the number of renal calculi (OR = 15.892, 95% CI 7.721–32.711, P < 0.01), the presence of residual calculi (OR = 1.780, 95% CI 0.897–3.533, P = 0.01), and operation time (OR = 1.033, 95% CI 1.020–1.046, P < 0.01). The diameter of the renal calculus, the number of renal calculi, the presence of residual calculi, and operation time were significant predictors of postoperative pain after PCNL.

Polymorphisms of the KCNS1, COMT and OPRM1 genes and development of postoperative pain in patients with osteoarthritis who underwent total knee or hip replacement

Postoperative pain (POP) is a serious complication that reduces the result of total knee (TKA) or hip arthroplasty (THA) in patients with osteoarthritis (OA). The search for predictors of postoperative pain is an actual problem.The aim of the study – to assessing relationship the polymorphisms of the KCNS1, COMT and OPRM1 genes and the development of POP in OA patients who underwent TKA or THA.Material and methods. The study group consisted of 95 patients with OA knee or hip (64.6% of women, 65.4±9.0 years) who underwent TKA (47.8%) or THA (52.2%). The presence of POP was determined when pain in the area of surgical intervention ≥40 mm (100 mm visual analog scale, VAS) persisted or appeared 3 and 6 months after surgery. All patients underwent genotyping of polymorphisms of the genes KCNS1 (rs734784), COMT (rs6269, rs4633) and OPRM1 (rs1799971) by polymerase chain reaction in real time using original sequence-specific primers and samples labeled with various fluorescent labels. Registration and interpretation of the obtained results were carried out on the DT-96 amplifier (DNA-Technology LLC, Russia).Results. POP was observed in 32.6% of patients who underwent TKA or THA. The frequency of POP after TKA and THA was 30.2% and 34.0% (p=0.882). Statistical analysis revealed no differences in the frequencies of the genotypes of the studied genes (p&gt;0,05). The presence of a homozygous genotype of the GG polymorphism of the KCNS1 gene (rs734784) was associated with the presence of POP in accordance with the recessive genetic model (GG vs AA+AG; odds ratio (OR) – 3.96 [95% confidence interval (CI): 1.51; 10.37]; p=0.005). The presence of the mutant allele T (TT+CT) in the genotype of the COMT polymorphism (rs4633) reduced the risk of POP compared to the carrier of the CC genotype (OR=0.32 [95% CI: 0.12; 0.83]; p=0.02) in accordance with the dominant genetic model. There was no significant correlation between the development of POP and the carrier of different genotypes and alleles of the COMT (rs6269) and OPRM1 (rs1799971) genes.Conclusions. There is a statistically significant association the polymorphism of the KCNS1 (rs734784) and COMT (rs4633) genes and the development of chronic POP in patients who underwent TKA or THA. Further studies of the genetic predisposition to POP are required on more clinical material.

Are Psychosocial Factors Predictors of Pain and Functional Outcomes After Knee Arthroplasty at 6 and 12 Months After Surgery? A Systematic Review

Background: To perform a systematic review of the literature to investigate the influence of psychosocial factors on pain and functional outcomes after knee arthroplasty from 6 months after surgery. Methods: Studies were included if they were prospective cohort observational studies. The subjects had to be middle aged or aged (mean age: 45 years) and have undergone total or unilateral knee arthroplasty. Studies should have recorded the influence of different psychosocial factors and the surgery outcomes had to be evaluated according to pain and/or function variables regardless of the tools used to measure them. In addition, outcome measures had to be recorded in the medium term (6 months) or the long term (12 months). Two reviewers assessed independently the MEDLINE, PsycINFO, and CINAHL databases to select observational studies. Results: Twenty-two studies with a total of 7156 patients (5349 females) were included in this review and the mean age was 67.92 years. Twenty-two studies included in this review showed a good average methodological quality (mean ± SD: 7.22 ± 0.92) on the Newcastle—Ottawa Scale for cohort studies. Conclusion: The evidence suggests that catastrophizing, kinesiophobia, anxiety, self-efficacy, and mental health are predictors of postoperative functional outcomes at 6 and 12 months after surgery. There is conflicting evidence on whether or not catastrophizing, anxiety, and depression are predictors of postoperative pain at 6 and 12 months after surgery.

Predictors of postoperative pain using PROMIS pain interference two-years following knee surgery

IntroductionThe purpose of this study was to identify preoperative factors associated with worse PROMIS Pain Interference (PI) two years following knee surgery. MethodsParticipants completed surveys preoperatively and two years postoperatively. Data collected included demographics, medical history, and multiple patient-reported outcomes measures, including PROMIS PI. ResultsAfter controlling for confounders, lower income, smoking, worse PROMIS Anxiety, worse Numeric Pain Score body pain, and worse Marx Activity Rating Scale were independent predictors for worse PROMIS PI two years after surgery. ConclusionWorse PROMIS PI two years after elective knee surgery is associated with multiple socio-demographic patient identifiers.

Chronic Breast Pain Prior to Breast Cancer Surgery Is Associated with Worse Acute Postoperative Pain Outcomes.

Acute postoperative pain is associated with adverse short and long-term outcomes among women undergoing surgery for breast cancer. Previous studies identified preexisting pain as a predictor of postoperative pain, but rarely accounted for pain location or chronicity. This study leveraged a multinational pain registry, PAIN OUT, to: (1) characterize patient subgroups based on preexisting chronic breast pain status and (2) determine the association of preexisting chronic pain with acute postoperative pain-related patient-reported outcomes and opioid consumption following breast cancer surgery. The primary outcome was a composite score comprising the mean of pain intensity and pain interference items from the International Pain Outcomes Questionnaire. The secondary outcome was opioid consumption in the recovery room and ward. Among 1889 patients, we characterized three subgroups: no preexisting chronic pain (n = 1600); chronic preexisting pain elsewhere (n = 128) and; chronic preexisting pain in the breast with/without pain elsewhere (n = 161). Controlling for covariates, women with preexisting chronic breast pain experienced more severe acute postoperative pain and pain interference (β = 1.0, 95% CI = 0.7-1.3, p < 0.001), and required higher doses of opioids postoperatively (β = 2.7, 95% CI = 0.6–4.8, p = 0.013). Preexisting chronic breast pain may be an important risk factor for poor pain-related postoperative outcomes. Targeted intervention of this subgroup may improve recovery.

The Predictors of Postoperative Pain Among Children Based on the Theory of Unpleasant Symptoms: A Descriptive-Correlational Study

PurposePostoperative pain (POP) is a common outcome of surgical interventions among children. Identifying POP contributing factors can help identify children who are at risk for POP and facilitate POP management. The aim of the study was to determine the predictors of POP based on the Theory of Unpleasant Symptoms. Design and methodsThis descriptive-correlational study was conducted in 2018–2019 on 153 children purposively recruited. Data were collected using a personal characteristics questionnaire, the Coping Strategies Questionnaire, the Child Pain Anxiety Symptoms Scale, and a Visual Analogue Scale for Pain. The SPSS software (v. 21.0) was used for data analysis. ResultsTwelve participants were excluded and final data analysis was done on the data obtained from 141 participants. Most of participants were male (65.2%), underwent abdominal surgery (53.2%), and experienced POP (86.5%). Their age mean was 8.58±2.23. Linear regression analysis revealed that the physiological factors of heart rate, preoperative pain, and surgery duration as well as the psychological factors of anxiety and coping strategies were significant predictors of POP among children. All these factors collectively explained 34% of the total variance of POP. Situational factors (such as age, gender, and ethnicity) had no significant effects on POP. ConclusionsHeart rate, preoperative pain, surgery duration, anxiety and coping as predictive factors of POP can be considered when designing effective POP management strategies. Practice implicationsThe findings provide a better understanding about the predictors of POP and can be used to develop pain management among children.

Correlation between patient health questionnaire-2 and postoperative pain in laparoscopic cholecystectomy.

BackgroundPostoperative pain is affected by preoperative depression. If the risk of postoperative pain associated with depression can be predicted preoperatively, anesthesiologists and/or surgeons can better manage it with personalized care. The objective of this study was to determine the efficacy of Patient Health Questionnaire-2 (PHQ-2) depression screening tool as a predictor of postoperative pain.MethodsA total of 50 patients scheduled for elective laparoscopic cholecystectomy with an American Society of Anesthesiologists physical status 1 or 2 were enrolled. They answered the PHQ-2, which consists of two questions, under the supervision of a researcher on the day before the surgery. The numerical rating scale (NRS) scores were assessed at post-anesthesia care unit (PACU), at 24, and 48 postoperative hours, and the amount of intravenous patient-controlled analgesia (IV-PCA) administered was documented at 24, 48, and 72 postoperative hours. At 72 h, the IV-PCA device was removed and the final dosage was recorded.ResultsThe NRS score in PACU was not significantly associated with the PHQ-2 score (correlation coefficients: 0.13 [P = 0.367]). However, the use of analgesics after surgery was higher in patients with PHQ-2 score of 3 or more (correlation coefficients: 0.33 [P = 0.018]).ConclusionsWe observed a correlation between the PHQ-2 score and postoperative pain. Therefore, PHQ-2 could be useful as a screening test for preoperative depression. Particularly, when 3 points were used as the cut-off score, the PHQ-2 score was associated with the dosage of analgesics, and the analgesic demand could be expected to be high with higher PHQ-2 scores.

Predictors of Post-operative Pain and Opioid Consumption in Patients Undergoing Liver Surgery.

Post-operative pain management is a critical component of perioperative care. Patients at risk of poorly controlled post-operative pain may benefit from early measures to optimize pain management. We sought to identify risk factors for post-operative pain and opioid consumption in patients undergoing liver resection. This is a multi-institutional prospective nested cohort study of patients undergoing open liver resection. Opioid consumption and pain scores were collected following surgery. To estimate the effects of patient factors on opioid consumption (oral morphine equivalents-OME) and on pain scores (NRS-11), we used generalized linear models and multivariable linear regression model, respectively. One hundred and fifty-three patients who underwent open liver resection between 2013 and 2016 were included in the study. The mean patient age was 62.2years, and 43.3% were female. Younger patients were significantly more likely to use more opioids in the early post-operative period (16.7 OME/10years, p < 0.001). Patient factors that were significantly associated with increased NRS-11 pain scores also included younger patient age (difference in pain score of 0.3/10years with cough and 0.2/10years at rest, p < 0.01 for both) as well as a history of analgesic use (difference in pain score of 0.9 with cough and 0.6 at rest, p < 0.01 and p = 0.07, respectively). Younger patients and those with a history of analgesic use are more likely to report higher post-operative pain and require higher doses of opioids. Early identification of these patients, and measures to better manage their pain, may contribute to optimal perioperative care.

Excessive remifentanil during total intravenous anesthesia is associated with increased risk of pain after robotic thyroid surgery.

The widespread use of remifentanil during total intravenous anesthesia (TIVA) has raised concerns about the risk of postoperative remifentanil-associated pain. Although a recent meta-analysis suggests that remifentanil-associated pain is unlikely to occur in patients with TIVA because of the protective effect of co-administered propofol, the evidence is not conclusive. We retrospectively assessed 635 patients who received robotic thyroid surgery under TIVA to evaluate the risk of remifentanil-associated pain. Postoperative pain was evaluated using 11-point numeric rating scale (NRS). Time dependent Cox proportional hazards regression analysis was used to determine the risk factors of treatment-requiring pain (NRS > 4) during the first 48 postoperative hours. Postoperative pain rapidly decreased, and treatment-requiring pain remained in 12.8% (81 out of 635) of patients at 48 hours postoperatively. After adjusting for the time-dependent analgesic consumption, intraoperative use of remifentanil > 0.2 mcg/kg/min was a positive predictor of postoperative pain with a hazard ratio of 1.296 (95% C.I., 1.014–1.656, P = 0.039) during 48 hours after surgery. In conclusion, excessive use of remifentanil during TIVA was associated with increased risk of pain after robotic thyroid surgery. Prospective trials are required to confirm these results and determine whether decreasing remifentanil consumption below the threshold can reduce postoperative pain.

Predictors of postoperative pain in total hip and knee arthroplasty

Introduction Total knee (TKA) and hip (THA) arthroplasties are associated with moderate to severe postoperative pain (POP). However, there is a marked inter-individual variation that may result from different factors. Its identification becomes crucial to attenuate POP in two of the most common surgical procedures worldwide. The objective of this study is to identify predictors of POP associated with THA and TKA. Material and methods Prospective cohort study in patients undergoing TKA and THA between September and December 2014. Data was collected through two questionnaires. Preoperative questionnaire was carried out 24 h before surgery, describing the following variables: body mass index (BMI), type of arthroplasty, chronic pain, diagnosis of depression, ASA score and sociocultural evaluation. The postoperative questionnaire evaluated POP, using the Brief Pain Inventory. We assessed the relationship between POP and the aforementioned variables. Multiple linear regression was performed to determine predictors of POP. Resultats Ninety-five patients included. Fifty-eight underwent TKA and 37 THA. Women had higher average (4.84 ± 1.59) and maximum (6.97 ± 2.19) pain scores (P 35, depression and chronic pain as predictors of the intensity of POP. Discussion POP after THA and TKA adversely affects the functional recovery, increases hospital stay and the incidence of chronic pain. Differences in pain perception after THA and TKA appear to be related to several factors although the literature remains controversial. Conclusion The identification of these factors will allow the establishment of customized perioperative schemes of pain control, reducing morbidity and increasing satisfaction of patients undergoing hip and knee replacement surgery.

SCN11A variants may influence postoperative pain sensitivity after gynecological surgery in Chinese Han female patients.

Nav1.9, encoded by sodium voltage-gated channel alpha subunit 11 (SCN11A), is one of the main sodium channels involved in pain transmission. Dysfunction of Nav1.9 alters pain sensitivity, resulting in insensitivity to pain or familial episodic pain. Our purpose was to explore the effects of SCN11A single-nucleotide polymorphisms (SNPs) on postoperative pain sensitivity in Chinese Han female patients after gynecological surgery.Here, we combined the methods of tag SNPs and candidate SNPs. The associations between eleven SCN11A SNPs and basic pain sensitivity in female healthy volunteers were analyzed using the Plink software. The SNPs associated with basic pain sensitivity were termed positive SCN11A SNPs. The effect of these positive SNPs on postoperative pain sensitivity was explored in patients undergoing elective gynecological laparoscopic surgery and receiving postoperative patient-controlled analgesia (PCA). We assessed pain intensity using the numeric pain rating scale (NRS) and recorded PCA consumption.Our results suggested that 5 SNPs (rs33985936, rs13080116, rs11720988, rs11709492, and rs11720013) in 11 tag and candidate SNPs were associated with basic pain sensitivity (P < .05). No evident association was found between the 5 positive SNPs and NRS (P > .05). However, among these positive SNPs, the minor alleles of rs33985936 and rs13080116 were significantly associated with increased PCA consumption (P < .01).To our knowledge, this is the first study to report that SCN11A SNPs affect postoperative pain sensitivity in Chinese Han women after gynecological surgery. The SNP rs33985936 and rs13080116 may serve as novel predictors for postoperative pain.

Predictors of Postoperative Pain and Narcotic Use After Primary Arthroscopic Rotator Cuff Repair

Predictors of Postoperative Pain and Narcotic Use After Primary Arthroscopic Rotator Cuff Repair

Influence of depression, catastrophizing, anxiety, and resilience on postoperative pain at the first day after otolaryngological surgery: A prospective single center cohort observational study.

The aim was to assess the association between objectified preoperative psychological factors and postoperative pain at the first day after otolaryngological surgery in accordance with other predictors of postoperative pain. Eighty-two (82) patients (59% male, median age 56 years) were included between January and May 2015. The psychological assessment the day before surgery included the Patient Health Questionnaire (PHQ-9), pain catastrophizing scale (PCS), State-Trait Operation Anxiety (STOA) inventory, and the resilience scale (RS-13). On first postoperative day, patients were rated their pain using the questionnaires of the German-wide project Quality Improvement in Postoperative Pain Treatment (QUIPS) including a numeric rating scale (NRS, 0-10) for determination of patient's maximal pain. QUIPS allowed standardized assessment of patients' characteristics, pain parameters, and outcome. The influence of preoperative and postoperative parameters on patients' maximal postoperative pain was estimated by univariate and multivariate statistical analysis. The mean maximal pain was 3.2 ± 2.9. In univariate analysis, higher PHQ-9 score more than 4 (P = 0.010), higher STOA trait anxiety (P = 0.044), and higher STOA total score (P = 0.043) were associated to more postoperative pain. In multivariate analysis higher PHQ-9 score remained an independent predictor for severe pain (beta = 0.302; 95% confidence interval [CI]: 0.054-0.473; P = 0.014). When all parameters were included into multivariate analysis, 2 of all somatic, psychological, and treatment factors were associated with severe maximal pain: more depression (PHQ-9; beta = 0.256; 95% CI: 0.042-0.404; P = 0.017), and use of opioids in the recovery room (beta = 0.371; 95% CI: 0.108-0.481; P = 0.002). Otolaryngological surgery covers the spectrum from low to severe postoperative pain and is therefore a good model for pain management studies. A set of somatic and psychological parameters seems to allow the identification of patients with higher risk for more postoperative pain. This should help to individualize and improve the perioperative pain management.

Genotypic Analysis of SCN9A for Prediction of Postoperative Pain in Female Patients Undergoing Gynecological Laparoscopic Surgery

Background: The SCN9A gene product is a critical component in human pain perception. Recent studies found that single-nucleotide polymorphisms (SNPs) in this gene contributed to the risk and severity of common pain phenotypes. Objectives: In this study, we aimed to assess the use of SCN9A SNP screening for predicting postoperative pain. Study Design: A retrospective assessment of patients who underwent gynecological laparoscopic surgery. Setting: Department of anesthesiology, a teaching hospital, in a medical college, major metropolitan city, China. Methods: Twenty-nine candidate and tag SCN9A SNPs were analyzed in this study. Four hundred twenty-one patients who underwent gynecological laparoscopic surgery and refused postoperative patient controlled analgesia (PCA) were recruited and completed the study protocol. An additional 578 patients who voluntarily received PCA treatment were included for verification. Postoperative pain intensity was evaluated in all patients using numerical rating scale (NRS), and for patients receiving PCA analgesic requirements were also recorded. Outcomes Assessment: The outcome was assessment of postoperative pain NRS and PCA analgesic requirements. Results: Ten different SCN9A SNPs exhibited significant associations with postoperative pain intensity, the incidence of severe postoperative pain, and postoperative PCA requirement. Of the candidate SCN9A SNPs, there was a statistically significant correlation between SNP rs6746030 and higher maximum NRS scores during the postoperative follow-up of non-PCA patients (P &lt; 0.05). Furthermore, there was a significant association between the tag SNP rs4286289 and both increased postoperative maximum NRS scores (P &lt; 0.05) and higher incidences of severe postoperative pain (P &lt; 0.05) in non-PCA patients. Meanwhile, in PCA patients, rs4286289 exhibited the strongest association (P = 0.001) with increased requirements for postoperative analgesics, which indirectly strengthened the significant association between this SNP and higher postoperative pain. Limitations: The limitations of this study include that it is an assessment of only Chinese women scheduled for gynecological laparoscopic surgery. Conclusion: The current study provides evidence that postoperative pain was affected by SCN9A variability in gynecological patients. Notably, our results provide the first indication that SCN9A SNP rs4286289 can be used as a predictor for hypersensitivity to postoperative pain. Key words: SCN9A, single-nucleotide polymorphisms, genotypic analysis, postoperative pain, female patients, gynecological laparoscopic surgery, genetic markers for pain, predictors of postoperative pain

Predictors of Post-Operative Pain and Narcotic Use after Primary Arthroscopic Rotator Cuff Repair

Primary arthroscopic rotator cuff repair has been shown to provide good pain relief and post-operative outcomes. However, studies investigating patient specific risk factors that may predict post-operative pain or narcotic use are lacking. The purpose of the current study is to further define these risk factors for increased pain and/or narcotic usage in the early post-operative period. We hypothesized that patients in all studied groups would have similar post-operative pain and narcotic use.

Preventive effect of ilioinguinal nerve block on postoperative pain after cesarean section.

Background:Cesarean section is a major operation that can be the predictor of postoperative pain and discomfort and, therefore, providing the effective postoperative analgesia is an important factor to facilitate sooner movement of the patient, better care of infants. The aim of this study was to determine the preventive effect of ilioinguinal nerve block on pain after cesarean section.Materials and Methods:In a randomized clinical trial study, 80 female candidates for cesarean section under general anesthesia were selected and divided into two groups. In the first group, ilioinguinal nerve was blocked and in the control group, ilioinguinal nerve block was not done. Finally, postoperative pain was compared between the two groups.Results:The mean pain intensity at 6 and 24 h after operation had no significant difference between two groups but in the rest of the times, it was different between two groups. Furthermore, in sitting position, except for 6 h, the pain intensity at the rest of the time had a significant difference between two groups. The pain intensity in 12 h after operation had a significant difference while in 24 h after operation; there was no difference between two groups. Doing repeated measures, ANOVA also indicated that the process of changes in the pain intensity in three positions of rest, sitting and walking had no significant difference up to 24 h after operation (P < 0.001).Conclusion:Control of pain after cesarean as one of the most common factors for abdominal surgery will lead to decrease the staying of the patient in hospital, reduce morbidity and lower use of narcotics and analgesics after surgery.

Factors that affect intravenous patient-controlled analgesia for postoperative pain following orthognathic surgery for mandibular prognathism.

The predictors of postoperative pain and analgesic consumption were previously found to include preoperative pain, anxiety, age, type of surgery, and genotype, but remaining unclear was whether intraoperative factors could predict postoperative pain. In the present study, we investigated the time-course of fentanyl consumption using intravenous patient-controlled analgesia records from patients who underwent orthognathic surgery for mandibular prognathism and analyzed the influence of anesthesia methods and surgical methods together with sex on the time course. A significant difference in the time course of fentanyl administration was found (P<0.001). No significant difference in the time course of fentanyl administration was found between males and females (P = 0.653), with no interaction between time course and sex (P = 0.567). No significant difference in the time course of fentanyl administration was found among anesthesia methods, such as fentanyl induction followed by fentanyl maintenance, fentanyl induction followed by remifentanil maintenance, and remifentanil induction followed by remifentanil maintenance (P = 0.512), but an interaction between time course and anesthesia method was observed (P = 0.004). A significant difference in the time course of fentanyl administration was found between surgical methods, such as bilateral mandibular sagittal split ramus osteotomy (BSSRO) and BSSRO combined with Le Fort I osteotomy (bimaxillary; P = 0.008), with no interaction between time course and surgical method (P = 0.535). Total postoperative 24 h consumption associated with the bimaxillary procedure was significantly higher than with BSSRO (P = 0.008). The present results indicate that administration patterns and total 24 h consumption were different among the three groups of anesthesia methods and between the two groups of surgical methods, respectively. Although more research on patient-controlled analgesia patterns and consumption is necessary, the present study will contribute to adequately relieving individual patients from postoperative pain.

The Utility of Single Nucleotide DNA Variations as Predictors of Postoperative Pain

Objectives: Genetic variation is an important contributor to postsurgical pain and thereby analgesia requirements. A description of the potential predictive power of genetic variants in pain should instruct improvements in pain management postoperatively. We set out to examine whether a set of genetic variants in pain related genes would show any association with actual pain outcomes in a typical surgical population. Methods: A candidate gene study was carried out in 135 surgical patients with 12 DNA variants (single nucleotide polymorphisms or ‘SNPs’) in known or putative pain pathway genes to detect associations with postoperative pain measured by a verbal rating score (VRS) and patient-controlled analgesia (PCA) usage rate. Standard PCR based molecular biology approaches were used. Results: At 20-24h after surgery, patients with the 1032G/1032G variant pair for the A1032G variant of the potassium channel KCNJ6 gene had a slightly higher median VRS than those with 1032A/1032A or 1032A/1032G pairs (p=0.04; dominant genetic model). This small difference was most apparent in the orthopaedic surgery patients where the 1032G/1032G pair associated with VRS (median(interquartile range)) of 5(4-6) vs. 3(0.5-4) in 1032A/1032A or 1032A/1032G groups. For PCA, patients with 3435C/3435C or 3435C/3435T pairs for ATPdependent efflux pump gene ABCB1 variant C3435T used PCA at a considerably higher rate of 0.89(0.07-1.66) mg.h -1 compared with just 0.11 (0-0.52) mg.h -1 for the 3435T/3435T pair (p=0.03; dominant model). A significantly higher usage rate was also detected for opioid receptor OPRM1 variant IVS2-691 with usage of 0.77(0.01-1.56) mg.h-1 for the IVS2C/IVS2C or IVS2C/IVS2G group vs. 0.24(0-1.26) mg.h-1 in the IVS2G/IVS2G group (p=0.04; recessive model). Conclusion: While this study has identified some significant statistical associations the potential utility of the studied DNA variants in prediction of postoperative pain and patient-controlled opioid analgesia requirements appears to be quite limited at present.