Factors Affecting Patient-controlled Analgesia Requirements

Rectus sheath block for acute pain management after robot-assisted laparoscopic prostatectomy

BACKGROUND

Robot-assisted laparoscopic prostatectomy (RALP) is a favored surgical approach for treating prostate cancer. However, RALP does not decrease postoperative pain significantly despite its minimal invasiveness. The pain associated with robot-assisted surgery is most severe during the immediate postoperative period. We aimed to demonstrate that preoperative rectus sheath block (RSB) can reduce acute pain after RALP.

METHODS

A prospective non-randomized study with two parallel groups was performed from June 2020 to August 2020. A total of 100 patients undergoing RALP were divided into two groups: the RSB group (n = 50) and the non-RSB group (n = 50). Ultrasound-guided RSB was performed preoperatively only in the RSB group. The primary outcome of the study was the visual analog scale (VAS) pain score during coughing (VAS-C) 1 h after surgery. In addition, the VAS pain score at rest (VAS-R) and the VAS-C were assessed up to 24 h after surgery. The doses of postoperative opioids consumed were also recorded.

RESULTS

The RSB group had a significantly lower VAS-C 1 h after RALP (58 [47-73] vs. 74 [63-83] mm, p = 0.001). In addition, the RSB group had significantly lower VAS-R and VAS-C scores, and postoperative opioid requirement, up to 6 h after surgery compared to the non-RSB group. Moreover, the VAS-R was significantly lower in the RSB group than in the non-RSB group 24 h after surgery.

CONCLUSION

Preoperative RSB significantly improved analgesia during the early period after RALP. The long-term analgesic efficacy of RSB needs further study.

Bilateral Flank Compression Maneuver for Reducing Pain on Coughing after Abdominal Surgery: A Prospective Study

BACKGROUND

Despite the major advances in analgesic techniques, pain relief in coughing after abdominal surgery remains challenging. Cough-related pain causes postoperative respiratory complications by impairing sputum clearance; nevertheless, an effective technique to abolish it is not yet available. We devised the bilateral flank compression (BFC) maneuver, in which the flanks are compressed medially using both hands. We conducted a prospective, single-center, single arm, nonrandomized, open-label, interventional trial, to investigate whether the BFC maneuver relieves cough-related pain after abdominal surgery and examined the efficacy of this maneuver in relation to patient characteristics and surgical factors.

STUDY DESIGN

Participants were patients who underwent gastroenterologic surgery (except for open inguinal hernia repair) at the Department of Surgery, Kyorin University School of Medicine. We evaluated postoperative pain, from postoperative days (PODs) 1 to 7, on coughing, with and without the BFC maneuver, using the Prince Henry pain scale.

RESULTS

We finally analyzed 514 patients. On each of the first 7 PODs, the BFC maneuver significantly relieved cough-related pain, especially on POD1; (the mean pain scores [standard deviation] with and without the BFC maneuver were 0.98 [1.030] vs 1.63 [1.112] points, p < 0.0001). On each POD, more patients were free of cough-related pain with than without the BFC maneuver, with the most marked difference on POD7 (52.0% [208/400] vs 16.8% [67/400], p < 0.0001).

CONCLUSIONS

The BFC maneuver relieves cough-related pain after abdominal surgery and may help prevent of postoperative pulmonary complications.

Early Postoperative Pain After Total Knee Arthroplasty Is Associated With Subsequent Poorer Functional Outcomes and Lower Satisfaction

BACKGROUND

There are few studies investigating the effects of acute postoperative pain on functional outcomes after total knee arthroplasty (TKA). The aims of this study are to identify perioperative factors associated with increased early postoperative pain and investigate the effects of acute postoperative day 1 and 2 pain on outcomes at 6 months and 2 years post-TKA.

METHODS

1041 unilateral TKA patients were included in this retrospective cohort study. Patients were categorized into minor (visual analog scale: VAS <5) and major (VAS ≥5) pain groups based on postoperative day 1/2 VAS scores. Patients were assessed preoperatively, at 6 months and 2 years using Knee Society Knee Score and Function Scores (KSFS), Oxford Knee Score (OKS), SF-36 physical and mental component score (SF-36 PCS), expectation and satisfaction scores. Perioperative variables including age, gender, race, body mass index, American Society of Anesthesiologist status, type of anesthesia, and presence of caregiver were analyzed as predictors of postoperative acute pain. Wilcoxon two-sample test was used to analyze outcomes significantly associated with "major pain." Multiple logistic regression was used to identify predictors of "major pain."

RESULTS

Patients with "minor pain" had significantly better KSFS, Knee Society Knee Score, OKS, and SF-36 PCS scores at 6 months and significantly better KSFS, OKS, SF-36 PCS, and satisfaction at 2 years (P < .05). A significantly higher percentage of patients with "minor pain" met the minimal clinically important difference for SF-36 PCS at 6 months and KSFS at 2 years (P < .05). Women, Indian/Malay race, higher BMI, and use of general over regional anesthesia were independent predictors of getting "major pain" (P < .05).

CONCLUSION

Patients should be counseled about risk factors of postoperative pain to manage preoperative expectations of surgery. Patients should be managed adequately using multimodal pain protocols to improve subsequent functional outcomes while avoiding unnecessary opioid use.

A Prospective Randomized Trial of Surgeon-Administered Intraoperative Transversus Abdominis Plane Block With Bupivacaine Against Liposomal Bupivacaine: The TINGLE Trial

BACKGROUND

Transversus abdominis plane blocks are increasingly used to achieve opioid-sparing analgesia after colorectal surgery. Traditionally, bupivacaine was the long-acting analgesic of choice, but the addition of dexamethasone and/or epinephrine to bupivacaine may extend block duration. Liposomal bupivacaine has also been suggested to achieve an extended analgesia duration of 72 hours but is significantly more expensive.

OBJECTIVE

The purpose of this study was to compare pain control between laparoscopic transversus abdominis plane blocks using liposomal bupivacaine versus bupivacaine with epinephrine and dexamethasone.

DESIGN

This was a parallel-group, single-institution, randomized clinical trial.

SETTINGS

The study was conducted at a single tertiary medical center.

PATIENTS

Consecutive patients between October 2018 to October 2019, ages 18 to 90 years, undergoing minimally invasive colorectal surgery with multimodal analgesia were included.

INTERVENTIONS

Patients were randomly assigned 1:1 to receive a laparoscopic transversus abdominis plane block with liposomal bupivacaine or bupivacaine with epinephrine and dexamethasone.

MAIN OUTCOME MEASURES

The primary outcome was total oral morphine equivalents administered in the first 48 hours postoperatively. Secondary outcomes included pain scores, time to ambulation and solid diet, hospital length of stay, and complications.

RESULTS

A total of 102 patients (50 men) with a median age of 42 years (interquartile range, 29-60 y) consented and were randomly assigned. The primary end point, total oral morphine equivalents administered in the first 48 hours, was not significantly different between the liposomal bupivacaine group (median = 69 mg) and the bupivacaine with epinephrine and dexamethasone group (median = 47 mg; difference in medians = 22 mg, (95% CI, -17 to 49 mg); p = 0.60). There were no significant differences in pain scores, time to ambulation, time to diet tolerance, time to bowel movement, length of stay, overall complications, or readmission rate between groups. There were no treatment-related adverse outcomes.

LIMITATIONS

This study was not placebo controlled or blinded.

CONCLUSIONS

This first randomized trial comparing laparoscopic transversus abdominis plane block with liposomal bupivacaine or bupivacaine with epinephrine and dexamethasone showed that a liposomal bupivacaine block does not provide superior or extended analgesia in the era of standardized multimodal analgesia protocols.See Video Abstract at http://links.lww.com/DCR/B533.

ESTUDIO PROSPECTIVO Y RANDOMIZADO DE BLOQUEO DEL PLANO MUSCULAR TRANSVERSO DEL ABDOMEN REALIZADO POR EL CIRUJANO CON BUPIVACANA VERSUS BUPIVACANA LIPOSOMAL ESTUDIO TINGLE

ANTECEDENTES:El bloqueo anestésico del plano muscular transverso del abdomen se utiliza cada vez más para lograr una analgesia con menos consumo de opioides después de cirugía colorrectal. Tradicionalmente, la Bupivacaína era el analgésico de acción prolongada de elección, pero al agregarse Dexametasona y/o Adrenalina a la Bupivacaína se puede prolongar la duración del bloqueo. También se ha propuesto que la Bupivacaína liposomal logra una duración prolongada de la analgesia de 72 horas, pero es significativamente más cara.OBJETIVO:Comparar el control del dolor entre bloqueo laparoscópico del plano de los transversos del abdomen usando Bupivacaína liposomal versus Bupivacaína con Adrenalina y Dexametasona.DISEÑO:Estudio clínico prospectivo y randomizado de una sola institución en grupos paralelos.AJUSTE:Centro médico terciario único.PACIENTES:Todos aquellos pacientes entre 18 y 90 años sometidos a cirugía colorrectal mínimamente invasiva con analgesia multimodal, entre octubre de 2018 a octubre de 2019 incluidos de manera consecutiva.INTERVENCIONES:Los pacientes fueron seleccionados aleatoriamente 1:1 para recibir un bloqueo laparoscópico del plano de los transversos del abdomen con Bupivacaína liposomal o Bupivacaína con Adrenalina y Dexametasona.PRINCIPALES MEDIDAS DE RESULTADO:El resultado primario fue el total de equivalentes de morfina oral administradas en las primeras 48 horas después de la operación. Los resultados secundarios incluyeron puntuaciones de dolor, inicio de dieta sólida, tiempo de inicio a la deambulación, la estadía hospitalaria y las complicaciones.RESULTADOS:Un total de 102 pacientes (50 hombres) con una mediana de edad de 42 años (IQR 29-60) fueron incluidos aleatoriamente. El criterio de valoración principal, equivalentes de morfina oral total administrada en las primeras 48 horas, no fue significativamente diferente entre el grupo de Bupivacaína liposomal (mediana = 69 mg) y el grupo de Bupivacaína con Adrenalina y Dexametasona (mediana = 47 mg; diferencia en medianas = 22 mg, IC del 95% [-17] - 49 mg, p = 0,60). No hubo diferencias significativas en las puntuaciones de dolor, tiempo de inicio a la deambulación, el tiempo de tolerancia a la dieta sólida, el tiempo hasta el primer evacuado intestinal, la duración de la estadía hospitalaria, las complicaciones generales o la tasa de readmisión entre los grupos. No hubo resultados adversos relacionados con el tratamiento.LIMITACIONES:Este estudio no fue controlado con placebo ni de manera cegada.CONCLUSIONES:Este primer estudio prospectivo y randomizado que comparó el bloqueo del plano de los músculos transversos del abdomen por vía laparoscópica, utilizando Bupivacaína liposomal o Bupivacaína con Adrenalina y Dexametasona, demostró que el bloqueo de Bupivacaína liposomal no proporciona ni mejor analgesia ni un efecto mas prolongado.Consulte Video Resumen en http://links.lww.com/DCR/B533.

The effect of age and gender on acute postoperative pain and function following lumbar spine surgeries

BACKGROUND AND PURPOSE

Understanding the factors contributing to the variability in postoperative pain and function following lumbar spine surgeries (LSS) is necessary to plan inpatient rehabilitation and optimize surgical outcomes. In particular, variability due to age and gender has not been studied. This study's aim was to evaluate the variability in postoperative pain and function, during hospital stay, due to age and gender following LSS.

METHODS

We conducted a retrospective analysis of 585 patients who underwent LSS during their hospital stay. Univariate ANCOVA was performed to study the differences in postoperative pain, and multivariate ANCOVA was performed to study the differences in postoperative function (gait distance, independency combined score, and balance combined score) between age groups (older adults [≥65 years of age] vs. younger adults) and gender.

RESULTS

Younger patients reported statistically, but not clinically, significant higher postoperative pain than older patients (β = 0.652 [95% CI (0.382-0.986)], p < 0.001), and males reported statistically, but not clinically, significant lower postoperative pain than female patients (β = -0.583 [95% CI (-0.825 to -0.252)], p < 0.001) with adjustment of covariates. Male patients walked significantly longer distance than female patients (β = 0.272 [95% CI (0.112-0.432)], p = 0.001) with adjustment of covariates. However, these were clinically insignificant. With adjustment of preoperative diagnosis, type of surgery, severity of illness, and prior level of function, there was no statistically significant difference between age groups in walking distance, and between age and gender groups in independency combined score and balance combined scores.

DISCUSSION

Following LSS, the difference in postoperative pain between age groups and gender are statistically but not clinically significant, suggesting patients require similar effective postoperative pain management regardless of age and gender. The apparent difference in age and gender in postoperative functional outcomes could be due to other factors.

Is There an Impact of Sex on Acute Postthoracotomy Pain? A Retrospective Analysis

BACKGROUND

Current knowledge about sex-related differences states that pain is generally more frequent and intense in women. Because severe postthoracotomy pain is associated with complications, sufficient pain control is essential. Data on sex-related aspects in the context of pain after thoracotomy are scarce. The study attempted to determine whether sex significantly affects pain and pain treatment after thoracotomy.

METHODS

This retrospective study assessed visual analogue scale (VAS) scores and analgesic consumption (opioids and diclofenac) during the first 5 days after surgery and the point in time when analgesics were changed from the intravenous to the oral route in patients who had open lung surgery. The influences of sex, PCEA (patient-controlled epidural analgesia), age, and surgical factors were evaluated with mixed-model analysis.

RESULTS

The study was able to include 344 patients (130 female, 214 male). The VAS scores model did not consider sex as relevant. The opioid model showed a PCEA-time-sex interaction with increasing opioid demand after day 3 that predominantly affected male patients (P < .001). Diclofenac doses where significantly higher in an interaction of female sex and small extent of surgery (P = .007). Posterolateral thoracotomy led to significantly higher VAS scores (P < .001) and higher demand for opioids (P = .007) and diclofenac (P = .012).

CONCLUSIONS

The study concluded that there are no general sex-related differences in pain intensity and analgesic requirement after thoracotomy. Anterolateral thoracotomy was the less painful surgical approach. PCEA had favorable results, although there seemed to a rebound pain phenomenon after epidural catheter removal on postoperative day 3 that mainly affected male patients.

Factors Related to the Consumption of Patient-Controlled Postoperative Analgesics in Korea: A Retrospective Study

BACKGROUND

Pain is the most common symptom among inpatients, and patient-controlled analgesia (PCA) is one of the effective pain management methods for postoperative patients.

AIMS

This study aimed to identify the predictors of analgesic consumption in patients using postoperative PCA.

DESIGN

As part of a descriptive and retrospective study, data were collected from the nursing records of 662 patients who underwent postoperative intravenous PCA for three days after surgery at one medical institution. Stepwise multiple regression analyses were conducted to select significant variables that could predict total analgesic consumption.

RESULTS

The results demonstrated that surgical sites, physical characteristics, donation surgery, and postoperative pain significantly influenced total analgesic consumption (POD 3, R² = 53%, p < .001).

CONCLUSION

The present findings provide valuable information for the effective postoperative administration of intravenous PCA and may contribute to the development of customized patient-centered pain management intervention by nurses through more accurate predictions of analgesic consumption based on individual characteristics, the surgical site, and the type of surgery-especially organ donation surgery. This study could contribute to improving preventive interventions by general nurses as well as pain control nurses by enabling more accurate predictions of patients' pain and consumption of self-controlled analgesic agents based on personal characteristics and surgical characteristics.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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 62.2 years, and 43.3% were female. Younger patients were significantly more likely to use more opioids in the early post-operative period (16.7 OME/10 years, 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 0.3/10 years with cough and 0.2/10 years 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).

CONCLUSION

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.

Randomized Clinical Trial Comparing Laparoscopic Versus Ultrasound-Guided Transversus Abdominis Plane Block in Minimally Invasive Colorectal Surgery

BACKGROUND

Transversus abdominis plane block may improve analgesia after colorectal surgery; however, techniques remain unstandardized and results are conflicting.

OBJECTIVE

The purpose of this study was to compare laparoscopic and ultrasound-guided transversus abdominis plane block with no block in minimally invasive colorectal surgery.

DESIGN

This was a randomized controlled trial.

SETTINGS

The study was conducted at an urban teaching hospital.

PATIENTS

Patients undergoing laparoscopic colorectal surgery were included.

INTERVENTIONS

The intervention included 2:2:1 randomization to laparoscopic, ultrasound-guided, or no transversus abdominis plane block.

MAIN OUTCOME MEASURES

Morphine use in the first 24 hours after surgery was measured.

RESULTS

The study cohort included 107 patients randomly assigned to laparoscopic (n = 41), ultrasound-guided (n = 45), or no transversus abdominis plane block (n = 21). Mean age was 50.4 years (SD ± 18 y), and 50 patients (47%) were men. Laparoscopic transversus abdominis plane block was superior to ultrasound-guided (p = 0.007) and no transversus abdominis plane block (p = 0.007), with median (interquartile range) total morphine used in the first 24 hours postoperatively of 17.6 mg (6.6-33.9 mg), 34.0 mg (16.4-44.4 mg), and 31.6 mg (18.4-44.4 mg). At 48 hours, laparoscopic transversus abdominis plane block remained superior to ultrasound-guided (p = 0.03) and no transversus abdominis plane block (p = 0.007) with median (interquartile range) total morphine used at 48 hours postoperatively of 26.8 mg (15.5-45.8 mg), 44.0 mg (27.6-70.0 mg), and 60.8 mg (34.8-78.8 mg). Mean hospital stay was 5.1 ± 3.1 days without any intergroup differences. Overall complications were similar between groups.

LIMITATIONS

Treatment teams were not blinded and there was operator dependence of techniques and variable timing of the blocks.

CONCLUSIONS

Laparoscopic transversus abdominis plane block is superior to ultrasound-guided and no transversus abdominis plane block in achieving pain control and minimizing opioid use in the first 24 hours after colorectal surgery. A large, multicenter, randomized trial is needed to confirm our findings. See Video Abstract at http://links.lww.com/DCR/A822.

Non-invasive patient-controlled analgesia in the management of acute postoperative pain in the hospital setting

OBJECTIVE

Acute postoperative pain is experienced by the majority of hospitalized patients undergoing surgical procedures, with many reporting inadequate pain relief and/or high levels of dissatisfaction with their pain management. Patient-controlled analgesia (PCA) ensures patient involvement in acute pain control, a key component for implementing a quality management system. This narrative article overviews the clinical evidence for conventional PCA and briefly discusses new, non-invasive PCA systems, namely the sufentanil sublingual tablet system (SSTS) and the fentanyl iontophoretic transdermal system (FITS).

METHODS

A Medline literature search ("patient-controlled analgesia" and "acute postoperative pain") was conducted to 1 April 2017; results from the main clinical trials are discussed. Additional literature was identified from the reference lists of cited publications.

RESULTS

Moderate to low quality evidence supports opioid-based intravenous PCA as an efficacious alternative to non-patient-controlled systemic analgesia for postoperative pain. However, despite the benefits of PCA, conventional intravenous PCA is limited by system-, drug- and human-related issues. The non-invasive SSTS and FITS have demonstrated good efficacy and safety in placebo- and intravenous morphine PCA-controlled trials, and are associated with high patient/healthcare practitioner satisfaction/ease of care ratings and offer early patient mobilization.

CONCLUSIONS

Evidence-based guidelines for acute postoperative pain management support the use of multimodal regimens in many situations. As effective and safe alternatives to conventional PCA, and with the added benefits of being non-invasive, easy to use and allowing early patient mobilization, the newer PCA systems may complement multimodal approaches, or potentially replace certain regimens, in hospitalized patients with acute postoperative pain.

Time-dependent analysis of dosage delivery information for patient-controlled analgesia services

Pain relief always plays the essential part of perioperative care and an important role of medical quality improvement. Patient-controlled analgesia (PCA) is a method that allows a patient to self-administer small boluses of analgesic to relieve the subjective pain. PCA logs from the infusion pump consisted of a lot of text messages which record all events during the therapies. The dosage information can be extracted from PCA logs to provide easily understanding features. The analysis of dosage information with time has great help to figure out the variance of a patient’s pain relief condition. To explore the trend of pain relief requirement, we developed a PCA dosage information generator (PCA DIG) to extract meaningful messages from PCA logs during the first 48 hours of therapies. PCA dosage information including consumption, delivery, infusion rate, and the ratio between demand and delivery is presented with corresponding values in 4 successive time frames. Time-dependent statistical analysis demonstrated the trends of analgesia requirements decreased gradually along with time. These findings are compatible with clinical observations and further provide valuable information about the strategy to customize postoperative pain management.

Assessing the Impact of Renal Function on Trajectory of Intravenous Patient-controlled Analgesic Demands Over Time After Open and Laparoscopic Colorectal Surgery Using Latent Curve Analysis

OBJECTIVES

Intravenous patient-controlled analgesia (IVPCA) is often used to relieve pain after colorectal surgery. This study aimed to model the trajectory of analgesic demand over time after colorectal cancer surgery and explore potentially relevant influential factors using latent curve analysis, focusing on laparoscopic-assisted surgery and renal function.

MATERIALS AND METHODS

Patients receiving colorectal surgery with postoperative IVPCA were randomly divided into 2 equal parts to enable model construction and cross validation. Archived data were retrieved from the IVPCA pump. Latent curve modeling with 2 latent variables that reflected the baseline and slope of IVPCA demand trajectory over time was used and the effects of potentially influential factors on the 2 latent variables were evaluated. Goodness-of-fit indices were used to assess the model fit to both the model construction and validation data sets.

RESULTS

Data were collected from 834 patients, of whom 112 had laparoscopic-assisted surgery. Latent curve analysis revealed that body weight increased the baseline analgesic demand over time, whereas increasing age, female sex, poor renal function, and laparoscopic-assisted surgery decrease it. By contrast, only age and weight exerted significant effects on the slope parameter to modify the trajectory of IVPCA demand. Patients with higher age or less weight tended to have a smoother decreasing trajectory of analgesic demands over time. There was good cross validation, as the parameter estimates derived from the model construction data set fitted well to the validation data set (root mean square error of approximation: 0.05).

CONCLUSION

Laparoscopic-assisted surgery and renal function affected the baseline trajectory of IVPCA demand over time, but had no significant effect on its shape.

Serial Analgesic Consumptions and Predictors of Intravenous Patient-controlled Analgesia with Cluster Analysis

Objectives:

To elucidate the dynamics of analgesic consumption regarding intravenous patient controlled analgesia (IVPCA) during postoperative period is rather complex partly due to between-patient variation and partly due to within-patient variation. A statistical method was proposed to classify serial analgesic consumption into different classifications that were further taken as the multiple outcomes on which to explore the associated predictors.

Methods:

We retrospectively included 3284 patients administrated by IVPCA for 3 days after surgery. A repeated measurement design corresponding to serial analgesic consumption variables defined as six-hour total analgesic consumptions was adopted. After determining the numbers of clusters, serial analgesic consumptions were classified into several homogeneous subgroups. Factors associated with new classifications were identified and quantified with a multinominal logistic regression model.

Results:

Three distinct analgesic classifications were aggregated, including “high”, ”middle” and “low” level of analgesic consumption of IVPCA. The mean analgesic consumptions on 12 successive analgesic consumptions at 6-hour interval of each classification consistently revealed a decreasing trend. As the trends were almost parallel with time, this suggests the time-invariant proportionality of analgesic consumption between the levels of analgesic consumption of IVPCA. Patient’s characteristics, like age, gender, weight, height, and cancer status, were significant factors associated with analgesic classifications. Surgical sites had great impacts on analgesic classifications.

Discussion:

The serial analgesic consumptions were simplified into 3 analgesic consumptions classifications. The identified predictors are useful to recognize patient’s analgesic classifications before using IVPCA. This study explored a new approach to analysing dynamic changes of postoperative analgesic consumptions.

Sex and Gender Differences in Central Nervous System-Related Disorders

There are important sex differences in the brain that seem to arise from biology as well as psychosocial influences. Sex differences in several aspects of human behavior and cognition have been reported. Gonadal sex steroids or genes found on sex chromosomes influence sex differences in neuroanatomy, neurochemistry and neuronal structure, and connectivity. There has been some resistance to accept that sex differences in the human brain exist and have biological relevance; however, a few years ago, it has been recommended by the USA National Institute of Mental Health to incorporate sex as a variable in experimental and clinical neurological and psychiatric studies. We here review the clinical literature on sex differences in pain and neurological and psychiatric diseases, with the aim to further stimulate interest in sexual dimorphisms in the brain and brain diseases, possibly encouraging more research in the field of the implications of sex differences for treating these conditions.

Factors affecting unused remaining volume of intravenous patient-controlled analgesia in patients following laparoscopic gynecologic surgery

PURPOSE

This study was undertaken to evaluate the factors affecting the unused remaining volume of intravenous patient-controlled analgesia (IV PCA) in patients who had undergone laparoscopic gynecologic surgery.

METHODS

We retrospectively collected patient records from pre-existing PCA log sheets from 98 patients. Surgical factors and IV PCA-related data including remaining volume, administration duration, early discontinuation (yes or no), and adverse reactions were recorded. Chi-square test, one-way analysis of variance, and multiple linear regression were applied for data analysis.

RESULTS

The average age of the 98 patients was 40.0 ± 8.24 years. The incidence of postoperative nausea and vomiting (PONV) and early discontinuation were not statistically significant among the different surgical groups (p = .540 and p = .338, respectively). Twenty-eight patients wanted discontinuation of IV PCA and the remaining volume was 33.6 ± 7.8 mL (range 20-55 mL). The significant determinants of remaining volume were whether IV PCA was discontinued due to PONV and duration of surgery (p < .001). The surgical duration was inversely correlated with the remaining volume.

CONCLUSION

Early discontinuation of IV PCA due to PONV is a major contributing factor to wastage of medicine. Prevention and treatment of PONV is needed to encourage patients to maintain PCA use for pain control.

Sex differences in pain: a brief review of clinical and experimental findings

Recent years have witnessed substantially increased research regarding sex differences in pain. The expansive body of literature in this area clearly suggests that men and women differ in their responses to pain, with increased pain sensitivity and risk for clinical pain commonly being observed among women. Also, differences in responsivity to pharmacological and non-pharmacological pain interventions have been observed; however, these effects are not always consistent and appear dependent on treatment type and characteristics of both the pain and the provider. Although the specific aetiological basis underlying these sex differences is unknown, it seems inevitable that multiple biological and psychosocial processes are contributing factors. For instance, emerging evidence suggests that genotype and endogenous opioid functioning play a causal role in these disparities, and considerable literature implicates sex hormones as factors influencing pain sensitivity. However, the specific modulatory effect of sex hormones on pain among men and women requires further exploration. Psychosocial processes such as pain coping and early-life exposure to stress may also explain sex differences in pain, in addition to stereotypical gender roles that may contribute to differences in pain expression. Therefore, this review will provide a brief overview of the extant literature examining sex-related differences in clinical and experimental pain, and highlights several biopsychosocial mechanisms implicated in these male-female differences. The future directions of this field of research are discussed with an emphasis aimed towards further elucidation of mechanisms which may inform future efforts to develop sex-specific treatments.

Pattern discovery from patient controlled analgesia demand behavior

Unlike previous research on patient controlled analgesia, this study explores patient demand behavior over time. We apply clustering methods to disclose demand patterns among patients over the first 24h of analgesic medication after surgery. We consider demographic, biomedical, and surgery-related data in statistical analyses to determine predictors for patient demand behavior, and use stepwise regression and Bayes risk analysis to evaluate the influence of demand pattern on analgesic requirements. We identify three demand patterns from 1655 patient controlled analgesia request log files. Statistical tests show correlations of gender (p=.0022), diastolic blood pressure (p=.025), surgery type (p=.0028), and surgical duration (p<.0095) with demand patterns. Stepwise regression and Bayes risk analysis show demand pattern plays the most important role in analgesic consumption prediction (p=0.E+0). This study suggests analgesia request patterns over time exist among patients, and clustering can disclose demand behavioral patterns.

Postoperative pain associated with orthopedic shoulder and elbow surgery: a prospective study

BACKGROUND

In the last 2 decades, extensive research in postoperative pain management has been undertaken to decrease morbidity. Orthopedic procedures tend to have increased pain compared with other procedures, but further research must be done to manage pain more efficiently. Postoperative pain morbidities and analgesic dependence continue to adversely affect health care.

MATERIALS AND METHODS

The study assessed the pain of 78 elbow and shoulder surgery patients preoperatively and postoperatively using the Short-Form McGill Pain Questionnaire (SF-MPQ). Preoperatively, each patient scored their preoperative pain (PP) and anticipated postoperative pain (APP). Postoperatively, they scored their 3-day (3dpp) and 6-week postoperative pain (6wpp). The pain intensities at these 4 intervals were then compared and analyzed using Pearson coefficients.

RESULTS

APP and PP were strong predictors of postoperative pain. The average APP was higher than the average postoperative pain. The 6wpp was significantly lower than the 3dpp. Sex, chronicity, and type of surgery were not significant factors; however, the group aged 18 to 39 years had a significant correlation with postoperative pain.

CONCLUSION

PP and APP were both independent predictors of increased postoperative pain. PP was also predictive of APP. Although, overall postoperative pain was lower than APP or PP due to pain management techniques, postoperative pain was still significantly higher in patients with increased APP or PP than their counterparts. Therefore, surgeons should factor patient's APP and PP to better manage their patient's postoperative pain to decrease comorbidities.

Reduced postoperative pain in total hip arthroplasty after minimal-invasive anterior approach

PURPOSE

The development of minimal-incision techniques for total hip replacement with preservation of soft tissue is generally associated with faster rehabilitation, reduction of postoperative pain and increased patient comfort. The aim of this study was to compare a minimal-incision anterior approach with a transgluteal lateral technique for hip replacement surgery with respect to postoperative pain, consumption of rescue medication, length of hospital stay and time to reach a defined range of motion.

METHODS

In this retrospective cohort study we investigated 100 patients with a minimal-incision anterior approach (group I) and 100 patients with a transgluteal lateral approach (group II) retrospectively undergoing unilateral hip replacement. The study variables were pain at rest and during physiotherapy, amount of rescue medication, the time to reach a defined flexion and time in hospital.

RESULTS

The patients of group I consumed less rescue medication (19.6 ± 6.9 mg vs. 23.6 ± 11.3 mg;  p = 0.005) and experienced less pain on the day of surgery (1.3 ± 1 vs. 2.3 ± 1.3, p = 0.0001) and the first postoperative day (0.41 ± 0.8 vs. 0.66 ± 1.1, p = 0.036). The time to reach the defined range of motion (6.4 ± 2 days vs. 7.4 ± 2.1 days; p = 0.001) and the length of hospital stay were shorter (10.2 ± 1.9 days vs. 13.4 ± 1.6 days; p = 0.0001) for group I. However, pain during physiotherapy was higher on the third and sixth through ninth days after surgery in comparison to group II (p = 0.001-0.013).

CONCLUSION

The implantation of a hip prosthesis through a minimal-incision anterior approach is successful in reducing postoperative pain and consumption of pain medication. Time to recovery and length of hospital stay are also influenced positively. Pain increases during physiotherapy, and may be mitigated by adopting limited weight bearing during the early postoperative period.

Do sex differences exist in opioid analgesia? A systematic review and meta-analysis of human experimental and clinical studies

Although a contribution of sex in opioid efficacy has garnered much attention, the confirmation and direction of any such difference remain elusive. We performed a systematic review of the available literature on sex differences in μ and mixed μ/κ opioid effect on acute and experimental pain. Fifty unique studies (including three unpublished studies) were included in the analyses. Across the 25 clinical studies on μ-opioids there was no significant sex-analgesia association. Restricting the analysis to patient-controlled analgesia (PCA) studies (irrespective of the opioid) yielded greater analgesia in women (n=15, effect size 0.22, 95% c.i. 0.02-0.42, P=0.028). Further restricting the analysis to PCA morphine studies yielded an even greater effect in women (n=11, effect size=0.36, 95% c.i. 0.17-0.56, P=0.003). Meta-regression indicated that the longer the duration of PCA, the difference in effect between the sexes further increased. Across experimental pain studies on μ-opioids women had greater antinociception from opioids (n=11, effect size=0.35; 95% c.i. 0.01-0.69, P=0.047), which was predominantly due to 6 morphine studies. Female patients had greater μ/κ opioid analgesia (n=7, effect size 0.84; 95% c.i. 0.25-1.43, P=0.005), but no sex-analgesia association was present in experimental studies (n=7). Sex differences exist in morphine-induced analgesia in both experimental pain studies and clinical PCA studies, with greater morphine efficacy in women. The data on non-morphine μ and mixed μ/κ-opioids are less convincing and require further study.

[Implementation of standardized postoperative pain therapy for orthopaedic patients. Comparison between unsystematic and standardized pain therapy]

BACKGROUND

The painless clinic and postoperative pain therapy are currently major issues in the management of surgical procedures. The aim of this study was to evaluate the benefit of a standardized pain therapy on the postoperative pain level after orthopaedic procedures.

PATIENTS AND METHODS

We investigated two different groups of patients who underwent an orthopaedic surgical procedure. Group 1 (n = 249) received a pain therapy which was based on an individual and surgery-dependent concept whereas group 2 (n = 243) was treated with a standardized pain therapy concept. The effect of the treatment was monitored with a VAS-based protocol.

RESULTS

Up to day 9 after surgery there was a significant difference between the two groups in regard to the postoperative pain. The patients of group 2 had less pain but had more unwanted side effects caused by the pain therapy during the first 3 days after surgery. Mobility and mental disposition were positively affected.

CONCLUSION

The implementation of a standardized pain therapy is successful in reducing postoperative pain. Mobility and mental disposition are also influenced positively. As a consequence the incidence of unwanted side effects is rising.

Sex, gender, and pain: a review of recent clinical and experimental findings

Sex-related influences on pain and analgesia have become a topic of tremendous scientific and clinical interest, especially in the last 10 to 15 years. Members of our research group published reviews of this literature more than a decade ago, and the intervening time period has witnessed robust growth in research regarding sex, gender, and pain. Therefore, it seems timely to revisit this literature. Abundant evidence from recent epidemiologic studies clearly demonstrates that women are at substantially greater risk for many clinical pain conditions, and there is some suggestion that postoperative and procedural pain may be more severe among women than men. Consistent with our previous reviews, current human findings regarding sex differences in experimental pain indicate greater pain sensitivity among females compared with males for most pain modalities, including more recently implemented clinically relevant pain models such as temporal summation of pain and intramuscular injection of algesic substances. The evidence regarding sex differences in laboratory measures of endogenous pain modulation is mixed, as are findings from studies using functional brain imaging to ascertain sex differences in pain-related cerebral activation. Also inconsistent are findings regarding sex differences in responses to pharmacologic and non-pharmacologic pain treatments. The article concludes with a discussion of potential biopsychosocial mechanisms that may underlie sex differences in pain, and considerations for future research are discussed.

PERSPECTIVE

This article reviews the recent literature regarding sex, gender, and pain. The growing body of evidence that has accumulated in the past 10 to 15 years continues to indicate substantial sex differences in clinical and experimental pain responses, and some evidence suggests that pain treatment responses may differ for women versus men.