Preoperative Pressure Pain Threshold Research Articles

Predicting severe pain after cesarean section: prospective cohort study

BACKGROUND: Severe and unbearable pain after abdominal delivery is recorded in 20% of cases, indicating the limitations of the applied methods of postoperative pain relief and the need for a personalized approach. Tests assessing preoperative pain threshold and anxiety have the greatest sensitivity and specificity as predictors of intense postoperative pain. The informative value of these tests in the Russian obstetric population has not been assessed. OBJECTIVE: This study aimed to determine the optimal method for predicting severe pain after cesarean section (CS). MATERIALS AND METHODS: This prospective cohort study included 212 women who underwent elective CS under spinal anesthesia. The Hospital Anxiety and Depression Scale (HADS) anxiety rating scale, pressure algometry, and cutaneous infiltration anesthesia pain intensity assessment were used as predictors of high-intensity pain. Postoperative pain intensity was assessed using a 10-point Numeric Rating Scale (NRS). The maximum level of pain according to the central pain level at rest (NRSr) and during movement (NRSa) was recorded 24 hour postoperatively. The number of requests for “rescue analgesia” was recorded. The predictive value of the studied methods was determined based on ROC curve analysis. RESULTS: Median (interquartile range) NRSa was 5 [4–5]. Severe pain was recorded in 14% of the patients. The area under the ROC-curve (AUC), reflecting the relationship between severe postoperative pain and pressure-pain threshold, was 0.91±0.03 with 95% confidence interval (CI) of 0.84–0.97 (p 0.001). The relationship between pain intensity during infiltration anesthesia and postoperative pain severity had AUC=0.88 ± 0.04 with 95% CI of 0.81–0.96 (p 0.001). The HADS anxiety score demonstrated the lowest predictive ability (AUC=0.69±0.06; 95% CI, 0.81–0.96; p 0.001). When all three techniques were used together, the AUC was 0.924±0.024 with 95% CI 0.88–0.97 (p=0.001). CONCLUSION: Preoperative pressure-pain threshold and pain severity during infiltration anesthesia are reliable predictors of severe pain after CS. Assessment of preoperative anxiety using HADS has low sensitivity and specificity. However, its use in conjunction with methods for assessing the pain threshold increases the predictive value of the combined model compared with the results of using the methods separately.

Altered central pain processing in patients with degenerative lumbar diseases and its association with low physical activity levels after lumbar spinal surgeries: a retrospective cohort analysis.

To investigate the occurrence of altered central pain modulation in patients with degenerative lumbar diseases (DLDs) and to analyze its association with physical activity (PA) 3years after lumbar decompression and fusion. Preoperative assessments of pressure pain thresholds (PPTs), temporal summation (TS), conditioned pain modulation (CPM) and pain were, respectively, recorded in 304 patients. These patients further underwent International Physical Activity Questionnaire (IPAQ) and both pain-related and psychological assessments 3years post-operation. Preoperatively, the patients had lower PPTs in both local pain and pain-free areas and lower CPM and higher TS in pain-free areas than healthy subjects (P < 0.05). Postoperatively, 53.9% (164/304) patients showed PA below healthy-related thresholds (< 600 MET min/w). Low PA group showed a greater postoperative weight gain and bone loss and a higher postoperative prevalence of both moderate anxiety and marginal depression than high PA group (P < 0.05). All covariates with differences between the high and low PA groups were subjected to multivariate logistic regression, and long preoperative disease duration, low preoperative PPT in pain-free area, high preoperative TS, revision surgery, severe postoperative low back pain and significant postoperative pain catastrophizing thought were independently associated with low postoperative PA (P < 0.05). This study supports the existence of central sensitization (CS) caused by abnormal central pain modulation in DLDs. Pre-existing CS in these patients may be associated with low PA after lumbar surgeries, and this low-activity lifestyle may predispose patients to multiple adverse health outcomes. Preoperative dynamic quantitative sensory testing may provide information for the identification of at-risk patients.

Reliability and validity of the pressure algometer in predicting gynecological surgery pain

Objective The purpose of this study was to determine the reliability and validity of the pressure algometer in predicting gynecological surgery pain. We looked into the predictive value of preoperative pain sensitivity to gynecological pain and the relationship between preoperative pressure pain threshold (PPT), pressure pain tolerance (PTO), and postoperative pain outcomes. Methods Reliability test: We recruited 60 volunteers at Nantong University. For three consecutive days, two examiners measured the pain sensitivity of each participant using a pressure algometer. Its test–retest and intra-rater reliability were assessed using the intraclass correlation coefficient (ICC). Validity test: We selected patients who underwent gynecological surgery in a hospital for the validity test. Before surgery, we assessed the patient’s pain sensitivity to various stimuli. To determine the relationship between preoperative pain sensitivity and postoperative pain, we collected postoperative Numerical Rating Scale (NRS) and sufentanil consumption data. Results The algometer revealed a high test–retest and intra-rater reliability. According to the calculation of Youden’s index, there was a 73.1% chance of patients with moderate to severe postoperative pain having a PTO <6.22 N, and patients with PTO <6.22 N had an 87.5% probability of moderate to severe postoperative pain. Conclusions The pressure algometer has a high degree of accuracy in measuring the PPT and PTO of normal healthy individuals, making it a reliable tool for quantifying pain sensitivity. PTO can be used to predict the occurrence of moderate to severe postoperative pain.

PD34-03 PRE-OPERATIVE CENTRAL SENSITIZATION AND HYPERSENSITIVITY TO PAIN IS ASSOCIATED WITH URETERAL STENT PAIN: FINDINGS FROM THE URINARY STONE DISEASE RESEARCH NETWORK (USDRN)

You have accessJournal of UrologyCME1 Apr 2023PD34-03 PRE-OPERATIVE CENTRAL SENSITIZATION AND HYPERSENSITIVITY TO PAIN IS ASSOCIATED WITH URETERAL STENT PAIN: FINDINGS FROM THE URINARY STONE DISEASE RESEARCH NETWORK (USDRN) Henry Lai, Hongqiu Yang, Jonathan Harper, Alana Desai, Gregory Tasian, Rebecca McCune, Ziya Kirkali, Hussein Al-Khalidi, Charles Scales, and Michele Curatolo Henry LaiHenry Lai More articles by this author , Hongqiu YangHongqiu Yang More articles by this author , Jonathan HarperJonathan Harper More articles by this author , Alana DesaiAlana Desai More articles by this author , Gregory TasianGregory Tasian More articles by this author , Rebecca McCuneRebecca McCune More articles by this author , Ziya KirkaliZiya Kirkali More articles by this author , Hussein Al-KhalidiHussein Al-Khalidi More articles by this author , Charles ScalesCharles Scales More articles by this author , and Michele CuratoloMichele Curatolo More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003327.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: To examine the relationship between pre-operative central sensitization and hypersensitivity to pain, and post-operative stent pain after ureteroscopy (URS) for stones. METHODS: Adult participants enrolled in the USDRN STudy to Enhance uNderstanding of sTent-associated Symptoms (STENTS) underwent quantitative sensory testing (QST) prior to URS and stent placement. Hypersensitivity to mechanical pain was assessed with pressure algometer. Participants rated their pain intensity (0-100) to 2 kg and 4 kg pressure applied to the flank and lower abdominal quadrant on the side of planned stent, and the contralateral forearm (control). Pressure pain thresholds (PPT) were also assessed. Central sensitization was assessed by applying a pinprick stimulator and calculating temporal summation (TS). Post-operative stent pain was assessed using PROMIS questionnaires for pain intensity and pain interference. Data were analyzed using repeated-measures mixed-effects models. RESULTS: Among the 412 participants with QST data, median age was 54 years, 46% were female. Higher pre-operative pain ratings to mechanical pressure to the ipsilateral flank and abdominal areas were associated with higher stent pain intensity on post-operative days 1, 3, 5, 7-9, and 30 days post-stent removal (p<0.05). Lower pre-operative PPT (i.e. higher mechanical hypersensitivity) was associated with higher post-operative pain intensity (p<0.05). Greater degree of central sensitization pre-operatively (higher TS) was associated with higher post-operative pain intensity (p<0.05). Significant correlations existed between pre-operative QST measures at the ipsilateral flank area and post-operative stent pain intensity (Table). Similar correlations were observed for ipsilateral abdominal area but not consistently for the forearm control site (data not shown). CONCLUSIONS: We have identified a physiological risk factor associated with stent pain. Preoperative central sensitization and hypersensitivity to pain were associated with post-operative stent pain. QST is a potential tool to identify patients likely to experience post-URS stent pain, which may facilitate early identification for mitigation, counseling, and management options. Source of Funding: NIH/NIDDK © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e920 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Henry Lai More articles by this author Hongqiu Yang More articles by this author Jonathan Harper More articles by this author Alana Desai More articles by this author Gregory Tasian More articles by this author Rebecca McCune More articles by this author Ziya Kirkali More articles by this author Hussein Al-Khalidi More articles by this author Charles Scales More articles by this author Michele Curatolo More articles by this author Expand All Advertisement PDF downloadLoading ...

What Is My Patient's Pain Phenotype? An Exercise in Transferring Patient Clustering Solutions between Institutions and across Patient Samples

Persistent post-mastectomy pain (PPMP) is a consequence of breast surgery that is variable in duration and severity across patients. The biopsychosocial model of pain acknowledges the impact of psychosocial and biophysical factors to modulate pain outcomes. The Rapid OPPERA Algorithm (ROPA) empirically clusters patients based on their biophysical and psychosocial characteristics and identified 3 clusters of patients based on 4 phenotypic characteristics with different risk of chronic pain. We aimed to understand the translatability of this type of phenotypic-based clustering, developed in patients with TMD, to a cohort undergoing breast cancer surgery, to predict pain severity and functional pain outcomes. Women (N:228, age:55.8±12.4, 87% White) scheduled for breast cancer surgery were prospectively enrolled in a longitudinal observational study. Preoperative pressure pain threshold (PPT) was measured using brief bedside QST, and anxiety, depression, and somatization were assessed using validated questionnaires. At 2-weeks, 3, 6, and 12-months after surgery, participants reported surgical area pain severity and frequency, and the impact of pain on cognitive/emotional and physical functioning. The ROPA clustering algorithm was applied using preoperative scores for anxiety, depression, somatization, and PPT. We determined differences between the identified clusters using general estimating equations linear regressions for longitudinal pain-related outcomes during the first year after surgery. Patients fell into three identified clusters: Adaptive (low psychosocial factors, low PPT; n=61), Pain Sensitive (moderate psychosocial factors, low PPT; n=125), and Global Symptoms (high psychosocial factors, moderate PPT; n=42). The Global Symptoms cluster, compared to other clusters, reported significantly greater pain severity and worse functional pain outcomes (p's<.05). The ROPA clustering algorithm identified a group at higher risk of PPMP, based on 4 preoperative phenotypic measures. Findings suggest that pain phenotyping may extend across patients with different diagnoses and clinical settings, highlighting the importance of personalized medicine, treating the "person type" as much as the diagnosis. Grant support from NIH/NIGMS: K23 GM110540.

Correlation between preoperative pressure pain assessments and anxiety and postoperative pain in impacted lower third molar surgery.

ObjectivesThe aim of this study was to evaluate correlations between anxiety and preoperative pressure pain assessments and postoperative pain and analgesic requirements in impacted lower third molar tooth surgery.Materials and MethodsThis prospective study enrolled 60 patients who underwent impacted lower third molar surgery. The preoperative State-Trait Anxiety Inventory-I (STAI-I), pressure pain threshold, and pressure pain tolerance scores were measured. At 2, 4, 6, 12, and 24 hours, and at 6 days following surgery, the patients scored their pain on the visual analogue scale and recorded their analgesic drug usage. The data were evaluated, and the results were statistically analyzed.ResultsOf the 60 patients, 38 were female. Mean age was 24.62±7.42 years. The study found no relationship between preoperative pressure pain assessments and postoperative pain (P>0.05). There was also no relationship observed between preoperative STAI-I scores and postoperative pain (P>0.05). However, there was a positive correlation between operation time and total medication taken (P<0.05).ConclusionPreoperative pressure pain threshold, pressure pain tolerance, and anxiety level had no significant effects on postoperative pain and analgesic requirements in impacted lower third molar surgery.

Preoperative Pressure Pain Threshold Is Associated With Postoperative Pain in Short-Stay Anorectal Surgery: A Prospective Observational Study.

BACKGROUND:Postoperative pain management is key for patient satisfaction. Pressure pain threshold (PPT) has been studied in some surgical cohorts but has not been studied in relationship to acute postoperative pain in short-stay patients undergoing anorectal surgery. We hypothesized that preoperative finger PPT measurements can identify respective patients with higher postoperative pain. Aiming to understand the relationship with subjective postoperative pain perception, we tested the hypotheses that preoperative PPT is associated with postoperative Visual Analog Scale (VAS) pain scores and correlates with postoperative analgesic consumption in short-stay patients undergoing anorectal surgery.METHODS:We prospectively assessed preoperative PPT in a cohort undergoing anorectal surgery, known as a moderately to severely painful procedure. Linear mixed-effects models were used to assess the relationship with postoperative VAS pain scores at 1 and 3 days as well as 4 weeks postoperatively. Logistic regression was used to study the relationship with additional postoperative analgesic consumption.RESULTS:We studied 128 patients and found that preoperative PPT is significantly associated with postoperative pain (P value for interaction = .025). Logistic regression modeling additionally revealed an association between the preoperative PPT and the need for additional postoperative analgesics, with odds of requiring additional analgesia decreasing by about 10% for each 1-point increase in PPT (odds ratio [OR] = 0.90; 95% confidence interval [CI], 00.81–0.98; P = .012).CONCLUSIONS:Preoperative finger PPT is associated with postoperative pain and might help identify patients who are at risk of developing more severe postoperative pain on anorectal surgery. Especially in ambulatory and short-stay settings, this approach can help to address patients’ high variability in pain sensitivity to facilitate appropriate postoperative analgesia, timely discharge, and prevent readmission.

Pre-operative pressure pain thresholds do not meaningfully explain satisfaction or improvement in pain after knee replacement: a cohort study

Pain sensitization could be a risk factor for poor outcomes after knee replacement surgery (KR) for knee osteoarthritis (KOA). We aimed to evaluate the association between pre-operative central and peripheral pain sensitization measured using a digital pressure algometer and KR outcomes. Consecutive patients with severe KOA listed for KR were recruited. Sociodemographic and symptoms data were collected prior to surgery. Pre-operative pressure pain thresholds (PPTs) were measured using a digital pressure algometer at the index knee and forearm. Patient satisfaction at 6 and 12 months after KR was assessed using a 4-point Likert scale, and dichotomized to satisfied and dissatisfied to KR. Western Ontario and McMaster Universities Index (WOMAC) Pain and function was assessed. The associations between pre-operative PPTs with KR outcomes at 6 and 12 months were evaluated. Of the 243 patients recruited, response rate at 6 and 12 months were 95.5% and 96.7%. The dissatisfaction rates were 8.2% and 5.1% at 6 and 12 months. There was no statistically significant association between pre-operative index knee or forearm PPTs and patient satisfaction. PPTs measured at the knee, but not the forearm, were weakly associated with change in the WOMAC pain score at 12 months, after adjustment for confounding factors. Pre-operative central sensitization, measured by handheld digital algometry, was not statistically significantly associated with satisfaction or change in pain after KR. Pre-operative peripheral sensitization was associated with change in pain symptoms after KR; however, this association was weak and unlikely to be a meaningful predictor of KR outcome in clinical practice.

Influence of centrally mediated symptoms on functional outcomes after carpal tunnel release

Patients with carpal tunnel syndrome (CTS) often show bilaterally increased pain sensitivity and widespread symptoms. We evaluated the influence of centrally mediated symptoms on functional outcomes of carpal tunnel release (CTR). A total of 120 patients with surgically treated CTS were enrolled. Centrally mediated symptoms were preoperatively measured by administering a self-reported central sensitization inventory (CSI) questionnaire and peripheral sensitization was measured by assessing patient’s pressure pain thresholds (PPT) in the forearm. Boston Carpal Tunnel Questionnaires (BCTQ) were assessed preoperatively and postoperatively at 3 and 12 months. CSI scores slightly correlated with symptom duration and moderately correlated with preoperative BCTQ scores, while PPT slightly correlated with the BCTQ scores. At 3 months, BCTQ symptom and function scores moderately correlated with lower PPTs and higher CSI scores. At 12 months, only severe electrophysiological grade was associated with BCTQ function scores. Multivariable analysis revealed that preoperative PPT, CSI, and female gender were associated with BCTQ scores at 3 months; these factors failed to be associated for 12-month outcomes. Centrally mediated symptoms measured by CSI and peripheral sensitization measured by PPTs correlated with symptom severity and duration. They were associated with poorer functional outcomes after CTR up to 3 months. However, they did not show persistent effects in the long term.

Parecoxib increases muscle pain threshold and relieves shoulder pain after gynecologic laparoscopy: a randomized controlled trial.

ObjectivesPostlaparoscopic shoulder pain (PLSP) remains a common problem after laparoscopies. The aim of this study was to investigate the correlation between pressure pain threshold (PPT) of different muscles and PLSP after gynecologic laparoscopy, and to explore the effect of parecoxib, a cyclooxygenase-2 inhibitor, on the changes of PPT.Materials and methodsThe patients were randomly allocated into two groups; group P and group C. In group P, parecoxib 40 mg was intravenously infused at 30 minutes before surgery and 8 and 20 hours after surgery. In group C, normal saline was infused at the corresponding time point. PPT assessment was performed 1 day before surgery and at postoperative 24 hours by using a pressure algometer at bilateral shoulder muscles (levator scapulae and supraspinatus) and forearm (flexor carpi ulnaris). Meanwhile, bilateral shoulder pain was evaluated through visual analog scale score at 24 hours after surgery.ResultsPreoperative PPT level of the shoulder, but not of the forearm, was significantly and negatively correlated with the intensity of ipsilateral PLSP. In group C, PPT levels of shoulder muscles, but not of forearm muscles, decreased after laparoscopy at postoperative 24 hours. The use of parecoxib significantly improved the decline of PPT levels of bilateral shoulder muscles (all P<0.01). Meanwhile, parecoxib reduced the incidence of PLSP (group P: 45% vs group C: 83.3%; odds ratio: 0.164; 95% confidence interval: 0.07–0.382; P<0.001) and the intensity of bilateral shoulder pain (both P<0.01).ConclusionPreoperative PPT levels of shoulder muscles are closely associated with the severity of shoulder pain after gynecologic laparoscopy. PPT levels of shoulder muscles, but not of forearm muscles, significantly decreased after surgery. Parecoxib improved the decrease of PPT and relieved PLSP.

Pain Pressure Thresholds Predict TKA Outcome at 6 Weeks and 6 Months

Introduction:8 – 19% of patients report dissatisfaction post Total Knee Arthroplasty (TKA). The reasons for this are complex and multiple factors have been reported to influence these dissatisfaction rates. A recent meta-analysis has confirmed evidence for central sensitisation to pain in patients with knee osteoarthritis (OA). It also called for future research to identify people with knee OA in whom sensitisation is a dominant feature and for longitudinal research to predict sensitisation post TKA. The clinical response to TKA in the presence of sensitisation has not been studied in detail. The purpose of this study was to evaluate the whether pressure pain thresholds would predict the early outcome of TKA and whether these pain thresholds were related to preoperative pain catastrophizing scales. Our hypothesis was that early post op satisfaction outcomes post TKA would relate to pressure pain thresholds (PPT).Methods:78 knees from 76 subjects were included in the study. Pre-operatively pressure pain threshold measurements were taken at the operative site, contralateral knee and at the deltoid. Multiple psychological and social predictors, including the pain catastrophising scale and the American Society Knee Score (2011), were measured preoperatively. The American Knee Society Score (2011) which includes a validated satisfaction component was used to measure TKA outcomes at 6 weeks, 6 months and 12 months post-operatively.Results:19% of the patients had a poor PPT(<175 kPa); 62% (175-430 kPa) moderate and 19% good (>430 kPa) preoperatively. These pre-operative PPT levels corresponded with satisfaction scores at 6 weeks and 6 months. The mean satisfaction score at 6 months in the poor group was 30.7 and 36.4 in the good group (p<0.0005), a significant difference was also demonstrated at 6 weeks. A significant difference in satisfaction scores was also seen between the moderate (32.9) and good groups at 6 weeks (p<0.02) and 6 months (p<0.003). There was no significant difference in satisfaction scores between the poor and moderate groups at 6 weeks or at 6 months. Patients in the poor PPT group had a mean pain catastrophising scale score of 21, this was significantly different to the good PPT group mean score 11.7 (p= 0.02). No patient in the poor PPT group recorded high satisfaction (36 or higher) at 6 weeks, but 5/15 (33%) recorded satisfaction of 36 or higher at 6 months. In the good PPT 11/15 (73.3%) had a satisfaction score of 36 or higher at 6 months.Conclusions:We have demonstrated that PPT’s correlate to significant differences in satisfaction at both 6 weeks and 6 months post TKA thus confirming our hypothesis. Those patients with poor PPT also scored more poorly on the pain catastrophising scale preoperatively. This patient group failed to attain the high levels of satisfaction seen in the good PPT group at 6 months. Care should be exercised in selecting patients with poor PPT’s and high pain catastrophising scale scores for TKA. This patient group may benefit from altered preoperative workup and postop pain treatment.

A New Real-time Method for Detecting the Effect of Fentanyl Using the Preoperative Pressure Pain Threshold and Narcotrend Index

Individual variability in the effects of opioid analgesics such as fentanyl remains a major challenge for tailored pharmacological treatment including postoperative analgesia. This study aimed to establish a new real-time method for detecting the effects of fentanyl and their individual differences in the preoperative period, using the pressure pain threshold (PPT) and Narcotrend index (NTI) test.Eighty women undergoing elective surgery under general anesthesia were enrolled in this randomized, double-blinded, placebo-controlled study to receive either intravenous fentanyl (Group F) or saline (Group S). Before (T1) and 5 (T2) and 10 min (T3) after intravenous injection, the PPT, NTI, respiratory rate, heart rate, blood pressure, and pulse oxygen saturation were measured. The initial time at which the Narcotrend index showed a decline was also recorded.In total, 40 patients in Group S and 38 patients in Group F were included in the final analysis. At 5 min and 10 min after intravenous fentanyl administration, the analgesic effect was determined by measuring the PPT, which was significantly increased (P < 0.001), and the sedative effect was detected using the NTI, which was significantly decreased (P < 0.001). The distribution of percentage changes of the PPT and NTI showed individual differences. At T2 and T3, the absolute changes in NTI and PPT were positively correlated (r = 0.444 at T2, P = 0.005; r = 0.332 at T3, P = 0.042).Through the PPT and NTI, it was feasible to easily detect the effects of fentanyl and their individual differences in real time before induction of anesthesia in the operation room. This method could potentially be applied to preoperatively determine patients’ sensitivity to fentanyl.

Presurgical assessment of temporal summation of pain predicts the development of chronic postoperative pain 12 months after total knee replacement

Patients with knee osteoarthritis demonstrate decreased pressure pain thresholds (PPTs), facilitated temporal summation (TS) of pain, and decreased conditioned pain modulation (CPM) compared with healthy controls. This study aimed to correlate preoperative PPTs, TS, and CPM with the development of chronic postoperative pain after total knee replacement (TKR) surgery. Knee pain intensity (visual analog scale [VAS]: 0-10), PPTs, TS, and CPM were collected before, 2 months, and 12 months after TKR. Patients were divided into a low-pain (VAS < 3) and a high-pain (VAS ≥ 3) group based on their VAS 12 months after TKR. The high-pain group (N = 17) had higher pain intensities compared with the low-pain group (N = 61) before surgery (P = 0.009) and 12 months after surgery (P < 0.001). The PPTs of the low-pain groups were normalized for all measurement sites comparing presurgery with 12 months postsurgery (P < 0.05, contralateral arm: P = 0.059), which was not the case for the high-pain group. The low-pain group showed a functional inhibitory CPM preoperatively and 12 months postoperatively (P < 0.05), which was not found in the high-pain group. The high-pain group had higher facilitated TS preoperatively and 12 months postoperatively compared with the low-pain group (P < 0.05). Preoperative TS level correlated to 12-month postoperative VAS (R = 0.240, P = 0.037). Patients who developed moderate-to-severe pain had pronociceptive changes compared with patients who developed mild pain postsurgery. Preoperative TS level correlated with the postoperative pain intensity and may be a preoperative mechanistic predictor for the development of chronic postoperative pain in patients with osteoarthritis after TKR.

The association between pre-operative pain sensitisation and chronic pain after knee replacement: an exploratory study

Chronic pain after total knee replacement (TKR) is a prevalent condition, affecting about 20% of patients. The aim of this study was to explore the relationship between pre-operative pain thresholds and chronic pain after TKR. Patients listed for a TKR because of osteoarthritis participated in a Quantitative Sensory Testing (QST) session prior to surgery. Pressure pain thresholds (PPTs) and hot pain thresholds were assessed at the osteoarthritic knee and the forearm. Patients were followed-up at 1-year after TKR, and the severity of pain in the replaced knee was assessed using the WOMAC Pain score. Pre-operative median QST thresholds were compared to thresholds from a normative database collected from 50 people with no knee pain. The relationship between pre-operative pain thresholds and pain severity post TKR were tested using correlations. Fifty-one patients participated in a pre-operative QST session and completed a 1-year WOMAC Pain score. Pre-operatively, patients demonstrated evidence of localised (knee) and widespread (forearm) pain sensitisation in response to pressure stimuli compared to healthy participants. Pre-operative PPTs at the forearm were found to be significantly correlated with 1-year WOMAC Pain scores (r=0.37, P=0.008). This study provides preliminary evidence that pre-operative widespread pain sensitisation, measured using pressure algometry, may be associated with chronic pain after TKR. Further research is needed to explore the predictive value of an assessment of pre-operative widespread pain sensitisation in identifying who is likely to develop chronic pain after TKR.

Influence of Mu-Opioid Receptor Variant on Morphine Use and Self-Rated Pain Following Abdominal Hysterectomy

A common variant in the mu-opioid receptor gene (OPRM1) has been associated with response to opioid analgesia. Our previous data revealed significantly higher amounts of morphine self-administered by patients carrying the 118G allele compared to those with the 118A allele after elective cesarean section. In this study, the association of this genetic variation with pressure pain, postoperative pain scores, and amount of morphine used was investigated in 973 patients undergoing scheduled total hysterectomy under general anesthesia. Preoperative pressure pain threshold and tolerance were also measured for most patients. For pressure pain, OPRM1 genotype was not significantly associated with either pain threshold or pain tolerance. Statistically significant associations were found for postoperative pain and the total amount of morphine used, with the GG group reporting higher pain scores and using the most morphine. When analysis was stratified by ethnic group, differences in weight-adjusted morphine for the 3 genotypic groups were also significant for the Chinese and Asian Indians. These results extend our previous finding on the association of higher self-reported pain and morphine use for acute postoperative pain with OPRM1 118G to patients who had total hysterectomy under general anesthesia. PerspectiveIn a large cohort of patients undergoing hysterectomy, we found large variability in the self-rated pain scores and the amount of morphine required for pain relief. Both are associated with OPRM1 genotypes and preoperative experimental pressure pain threshold. Experimental pressure pain tolerance is also associated with postoperative pain.

A Single-nucleotide Polymorphism in SCN9A May Decrease Postoperative Pain Sensitivity in the General Population

This study aimed to explore the role of a nonsynonymous single-nucleotide polymorphism, 3312G>T, in SCN9A, which was identified in probands with congenital indifference to pain, but which is also present in normal controls, in the prediction of individual baseline pain perception, and postoperative pain sensitivity in the general population. Preoperative pressure pain thresholds and tolerance were measured in 200 patients undergoing pancreatectomy, and the postoperative pain sensitivity and analgesic demand were recorded. These variables were compared according to the SCN9A 3312G>T alleles. Logistic regression analysis was used to test the role of preoperative variables in the prediction of postoperative inadequate analgesia. The 3312Tallele was present in 22 individuals, and the 3312Tallele frequency was 5.5% (22/200). The average patient-controlled analgesia pressing frequency and opioid consumption in 3312G patients was significantly higher than those in 3312T patients (2.70 [SD: 0.84] vs. 2.05 [SD: 0.43], P < 0.001; 100.8 [SD: 40.7] vs. 74.8 [SD: 20.8] ml, P = 0.006). The incidence of inadequate analgesia in 3312G patients was significantly higher than that of patients carrying the 3312Tallele (29.2% vs. 4.5%; P = 0.013). Carrying the 3312Tallele and having a higher pressure pain threshold predicted a lower risk of postoperative inadequate analgesia, with an odds ratio of 0.10 (95% CI: 0.01 to 0.76, P = 0.026) and 0.32 (95% CI: 0.13 to 0.82, P = 0.018), respectively. Patients carrying the SCN9A 3312Tallele presented with lower postoperative pain sensitivity in the presence of a similar surgical pain stimulus, and had a lower likelihood of developing inadequate analgesia than those carrying the 3312Gallele.

Predicting Postoperative Pain by Preoperative Pressure Pain Assessment

The goal of this study was to evaluate whether preoperative pressure pain sensitivity testing is predictive of postoperative surgical pain. Female subjects undergoing lower abdominal gynecologic surgery were studied. A pressure algometer was used preoperatively to determine the pressure pain threshold and tolerance. A visual analog scale (VAS) was used to assess postoperative pain. A State-Trait Anxiety Inventory was used to assess patients' anxiety. Subjects received intravenous patient-controlled analgesia for postoperative pain control. The preoperative pain threshold and tolerance were compared with the postoperative VAS pain score and morphine consumption. Forty women were enrolled. Their preoperative pressure pain threshold and tolerance were 141 +/- 65 kPa and 223 +/- 62 kPa, respectively. The VAS pain score in the postanesthesia care unit and at 24 h postoperatively were 81 +/- 24 and 31 +/- 10, respectively. Highly anxious patients had higher VAS pain scores in the postanesthesia care unit (P < 0.05). Pressure pain tolerance was significantly correlated with the VAS at 24 h postoperatively (P < 0.001, r = -0.52). Pressure pain tolerance after fentanyl administration (mean, 272 +/- 68 kPa) correlated significantly with morphine consumption in the first 24 h postoperatively (P < 0.002, r = -0.48). Assessment of preoperative pressure pain tolerance is significantly correlated with the level of postoperative pain. Pain tolerance assessment after fentanyl was administered and fentanyl sensitivity predicted the dose of analgesics used in the first 24 h after surgery. The algometer is thus a simple, useful tool for predicting postoperative pain and analgesic consumption.

This Month in Anesthesiology

This Month in Anesthesiology