Correlates of postoperative pain and intravenous patient-controlled analgesia use in younger and older surgical patients

Perioperative Dexmedetomidine Infusion Improves Perioperative Care of Bariatric-Metabolic Surgery: A Single Center Experience with Meta-Analysis

PURPOSE

This study aims to determine the effects of perioperative dexmedetomidine infusion (PDI) on Asian patients undergoing bariatric-metabolic surgery (BMS), focusing on the need for pain medications and management of postoperative nausea and vomiting (PONV), and to investigate the association with these variables, including patients' characteristics and BMS data.

MATERIALS AND METHODS

A retrospective review of prospectively collected data was conducted in an Asian weight management center from August 2016 to October 2021. A total of 147 native patients with severe obesity were enrolled. All patients were informed of the full support of perioperative pain medications for BMS. The pain numeric rating scale scores, events of PONV, needs for pain medications, and the associated patients' characteristics were analyzed. A p-value of < 0.05 was considered statistically significant. Furthermore, to verify the effects of perioperative usage of dexmedetomidine for BMS, a systematic review with meta-analysis of currently available randomized control trials was performed.

RESULTS

Among the 147 enrolled patients, 107 underwent laparoscopic sleeve gastrectomy and 40 underwent laparoscopic Roux-en-Y gastric bypass. PDI has been used as an adjunct multimodal analgesia for BMS in our institution since June 2017 (group D; n = 114). In comparison with those not administered with perioperative dexmedetomidine (group C; n = 33), lower pain numeric rating scale scores (2.52 ± 2.46 vs. 4.27 ± 2.95, p = 0.007) in the postanesthesia care unit, fewer PONV (32.46% vs. 51.52%; p = 0.046), and infrequent needs of additional pain medications (19.47% vs. 45.45%; p = 0.003) were observed in group D. Multivariable analysis demonstrated that type II diabetes mellitus was correlated with the decreased need of pain medications other than PDI (p = 0.035). Moreover, dexmedetomidine seemed to have a better analgesic effect for patients with longer surgical time based on our meta-analysis.

CONCLUSION

Based on our limited experience, PDI could be a practical solution to alleviate pain and PONV in Asian patients undergoing BMS. Moreover, it might reduce the need for rescue painkillers with better postoperative pain management for patients with type II diabetes mellitus or longer surgical time.

Opioid prescriptions after knee replacement: a retrospective study of pathways and prognostic factors in the Swiss healthcare setting

OBJECTIVES

The optimal use of opioids after knee replacement (KR) remains to be determined, given the growing evidence that opioids are no more effective than other analgesics and that their adverse effects can impair quality of life. Therefore, the objective is to examine opioid prescriptions after KR.

DESIGN

In this retrospective study, we used descriptive statistics and estimated the association of prognostic factors using generalised negative binomial models.

SETTING

The study is based on anonymised claims data of patients with mandatory health insurance at Helsana, a leading Swiss health insurance.

PARTICIPANTS

Overall, 9122 patients undergoing KR between 2015 and 2018 were identified.

PRIMARY AND SECONDARY OUTCOME MEASURES

Based on reimbursed bills, we calculated the dosage (morphine equivalent dose, MED) and the episode length (acute: <90 days; subacute: ≥90 to <120 days or <10 claims; chronic: ≥90 days and ≥10 claims or ≥120 days). The incidence rate ratios (IRRs) for postoperative opioids were calculated.

RESULTS

Of all patients, 3445 (37.8%) received opioids in the postoperative year. A large majority had acute episodes (3067, 89.0%), 2211 (65.0%) had peak MED levels above 100 mg/day and most patients received opioids in the first 10 postoperative weeks (2881, 31.6%). Increasing age (66-75 and >75 vs 18-65) was associated with decreased IRR (0.776 (95% CI 0.7 to 0.859); 0.723 (95% CI 0.649 to 0.805)), whereas preoperative non-opioid analgesics and opioids were associated with higher IRR (1.271 (95% CI 1.155 to 1.399); 3.977 (95% CI 4.409 to 3.591)).

CONCLUSION

The high opioid demand is unexpected given that current recommendations advise using opioids only when other pain therapies are ineffective. To ensure medication safety, it is important to consider alternative treatment options and ensure that benefits outweigh potential risks.

Measurement of Postoperative Quality of Pain in Abdominoplasty Patients-An Outcome Oriented Prospective Study

(1) Background: Postoperative pain is a frequently underestimated complication significantly influencing surgical outcome and patient satisfaction. While abdominoplasty is one of the most commonly performed plastic surgery procedures, studies investigating postoperative pain are limited in current literature. (2) Methods: In this prospective study, 55 subjects who underwent horizontal abdominoplasty were included. Pain assessment was performed by using the standardized questionnaire of the Benchmark Quality Assurance in Postoperative Pain Management (QUIPS). Surgical, process and outcome parameters were then used for subgroup analysis. (3) Results: We found a significantly decreased minimal pain level in patients with high resection weight compared to the low resection weight group (p = 0.01 *). Additionally, Spearman correlation shows significant negative correlation between resection weight and the parameter "Minimal pain since surgery" (rs = -0.332; p = 0.013). Furthermore, average mood is impaired in the low weight resection group, indicating a statistical tendency (p = 0.06 and a Χ² = 3.56). We found statistically significant higher maximum reported pain scores (rs = 0.271; p = 0.045) in elderly patients. Patients with shorter surgery showed a statistically significant (Χ² = 4.61, p = 0.03) increased claim for painkillers. Moreover, "mood impairment after surgery" shows a dramatic trend to be enhanced in the group with shorter OP duration (Χ² = 3.56, p = 0.06). (4) Conclusions: While QUIPS has proven to be a useful tool for the evaluation of postoperative pain therapy after abdominoplasty, only continuous re-evaluation of pain therapy is a prerequisite for constant improvement of postoperative pain management and may be the first approach to develop a procedure-specific pain guideline for abdominoplasty. Despite a high satisfaction score, we detected a subpopulation with inadequate pain management in elderly patients, patients with low resection weight and a short duration of surgery.

Is ABO Blood Group a Predictive Factor for the Amount of Opioid Consumption in the First 24 Hours After Cesarean Section?

Background

Cesarean section is the most common major surgery performed globally. Blood group O has been found as a factor affecting pain severity after cesarean section. We aimed to evaluate the predictive factors, including ABO blood group, for the amount of opioid consumption (measured as milligrams of morphine equivalent [MME]) within the first 24 hrs after cesarean section.

Methods

This retrospective study was done in 1530 pregnant women who had a cesarean section under the same regimen of spinal anesthesia (2.2 mL of 0.5% hyperbaric bupivacaine and morphine 0.2 mg). All were prescribed regular paracetamol and ibuprofen for postoperative pain control. Univariate and multinomial regression analyses were performed to identify the predictive factors for opioid consumption in the first 24 hrs postoperatively.

Results

About 2/5 of them (43.3%) received 0 mg MME, while 25.6%, 23.7% and 7.4% received 1–5, 6–10 and >10 mg MME, respectively. The majority have blood group O (40.6%), while 23.4%, 28% and 8% have blood group A, B and AB, respectively. After univariate and multinomial regression analyses, operation time, opioid consumption in PACU, maximum VNRS within the first 24 hrs and consumption of both paracetamol and ibuprofen were identified as predictive factors for postoperative opioid consumption. ABO blood group exhibited no correlation for opioid requirement postoperatively.

Conclusion

ABO blood group is not a predictive factor for opioid requirement within the first 24 hrs following cesarean section. Duration of operation, opioid given in PACU, maximum VNRS on ward and consumption of both paracetamol and ibuprofen have been found to be predictive factors for postcesarean opioid requirement.

Inpatient Opioid Consumption Variability following Total Knee Arthroplasty: Analysis of 4,038 Procedures

This study examined an early iteration of an inpatient opioid administration-reporting tool, which standardized patient opioid consumption as an average daily morphine milligram equivalence per surgical encounter (MME/day/encounter) among total knee arthroplasty (TKA) recipients. The objective was to assess the variability of inpatient opioid administration rates among surgeons after implementation of a multimodal opioid sparing pain protocol. We queried the electronic medical record at our institution for patients undergoing elective primary TKA between January 1, 2016 and June 30, 2018. Patient demographics, inpatient and surgical factors, and inpatient opioid administration were retrieved. Opioid consumption was converted into average MME for each postoperative day. These MME/day/encounter values were used to determine mean and variance of opioids prescribed by individual surgeons. A secondary analysis of regional inpatient opioid consumption was determined by patient zip codes. In total, 23 surgeons performed 4,038 primary TKA. The institutional average opioid dose was 46.24 ± 0.75 MME/day/encounter. Average intersurgeon (IS) opioid prescribing ranged from 17.67 to 59.15 MME/day/encounter. Intrasurgeon variability ranged between ± 1.01 and ± 7.51 MME/day/encounter. After adjusting for patient factors, the average institutional MME/day/encounter was 38.43 ± 0.42, with average IS variability ranging from 18.29 to 42.84 MME/day/encounter, and intrasurgeon variability ranging between ± 1.05 and ± 2.82 MME/day/encounter. Our results suggest that there is intrainstitutional variability in opioid administration following primary TKA even after controlling for potential patient risk factors. TKA candidates may benefit from the implementation of a more rigid standardization of multimodal pain management protocols that can control pain while minimizing the opioid burden. This is a level of evidence III, retrospective observational analysis.

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.

Keeping tabs: Reducing postoperative opioid prescriptions for patients after breast surgical procedures

BACKGROUND

As the opioid crisis continues, it is critical that health care providers ensure they are not overprescribing opioid medications. At our institution (Walter Reed National Military Medical Center, Bethesda, MD), postoperative patients after breast surgeries are discharged with variable amounts of opioid medications. However, many patients report minimal opioid use. The objectives of this study were to characterize postoperative opioid usage and prescribing practices for patients undergoing various breast surgeries and to recommend the number of opioid pills for discharge for each procedure.

METHODS

This was a prospective, single-institution study of all patients undergoing breast surgery from October 2018 to 2019. All patients were enrolled in our institution's enhanced recovery after surgery protocol. Patients were given questionnaires at their 2-week postoperative clinic appointment that evaluated perioperative pain and use of pain medications. The electronic medical record was reviewed to obtain additional information. Appropriate parametric and nonparametric tests were used for analysis.

RESULTS

A total of 190 breast surgery patients completed the survey. We observed no significant differences in pain scores except between re-excision and mastectomy. Of these patients, 99% were prescribed opioids; however, only 53% of patients used them. Of those patients who were prescribed opioids, on average, all were prescribed more pills than were used.

CONCLUSION

Our study demonstrates that it is possible to discharge all breast surgery patients with fewer than 10 opioid pills, except for special circumstances. This is the first study to provide a set of specific recommended discharge medications. Utilization of an enhanced recovery after surgery protocol with standardized discharge opioids can be used successfully to reduce the number of opioids prescribed to patients.

Pain threshold, anxiety and other factors affect intensity of postoperative pain in gastric cancer patients: A prospective cohort study

Objective

This prospective cohort study explored factors related to postoperative pain in gastric cancer patients.

Methods

A total of 236 patients who underwent gastrectomy were enrolled. All patients enrolled in the study completed the Hospital Anxiety and Depression Scale (HADS) questionnaire and Life Orientation Test-Revised (LOT-R) questionnaire on the day before surgery. Heat pain threshold (HPT), cold pain threshold (CPT) and pressure pain threshold (PPT) were measured for all patients one day prior to surgery and demographic details were collected. All patients were connected to a patient-controlled intravenous analgesia (PCIA) pump at the end of the surgery. The occurrence of postoperative pain was used as a dependent variable, and multivariate logistic regression analyses were conducted to screen for factors affecting postoperative pain.

Results

In total, 83 patients (35.2%) had postoperative pain. Body mass index (BMI) ≥28 kg/m² [odds ratio (OR): 2.67; 95% confidence interval (95% CI): 1.07−6.67], total gastrectomy (OR: 2.64; 95% CI: 1.42−4.91), preoperative anxiety score ≥8 (OR: 2.37; 95% CI: 1.12−5.02), heat pain threshold ≤4.9 s (OR: 2.14; 95% CI: 1.06−4.32), pressure pain threshold ≤4 g (OR: 2.05; 95% CI: 1.05−4.03), and female gender (OR: 1.99; 95% CI: 1.04−3.83) were risk factors for postoperative pain.

Conclusions

Obesity, wide range of gastrectomy, high preoperative anxiety, low HPT and PPT, and female gender are associated with increased risk for postoperative pain.

Colorectal resection via natural orifice specimen extraction versus conventional laparoscopic extraction: a meta-analysis with meta-regression

BACKGROUND

Studies have shown differences in postoperative outcomes between two minimally invasive extraction methods for colorectal lesions-natural orifice specimen extraction surgery (NOSES) and conventional laparoscopic surgery (CLS). The aim of this study was to discover the major differences in NOSES and CLS to refine current practice.

METHODS

Electronic databases were searched for articles comparing NOSES and CLS from inception till March 2020. Weighted mean differences (WMD) and odds ratio (OR) were estimated for continuous and dichotomous outcomes, respectively. Summary statistics were calculated using the DerSimonian and Laird random effects.

RESULTS

Twenty-one studies (15 on malignant disease, 4 on benign disease, 2 on both) were included in this meta-analysis, totalling 2378 patients (1079 NOSE, 1299 CLS). NOSE was associated with decreased: intraoperative bleeding (WMD: - 10.652 ml; 95% CI: - 18.818 ml to - 2.482 ml; p < 0.001), pain score (WMD: - 1.520; 95% CI - 1.965 to - 1.076; p < 0.001), time to flatus (WMD: - 0.306 days; 95% CI: - 0.526 to - 0.085 days; p < 0.001), length of hospital stay (WMD: - 1.048 days; 95% CI: - 1.488 to - 0.609 days; p < 0.001), and total morbidity (OR: 0.548; 95% CI: 0.387 to 0.777; p = 0.001). Subgroup analyses showed significant differences between malignant and benign lesions for intraoperative bleeding (p = 0.011) and pain score (p = 0.010). Meta-regression analyses showed an association between the American Society of Anaesthesiologists (ASA) physical status classification III with pain (p = 0.03) and ASA III with time to flatus (p = 0.04).

CONCLUSIONS

This meta-analysis and meta-regression demonstrated that NOSES had better postoperative outcomes compared to CLS. More comprehensive reviews should be conducted on the long-term outcomes specific to the extraction site to better inform clinical practice.

Variations in postoperative opioid prescribing by day of week and duration of hospital stay

BACKGROUND

Studies demonstrate wide variation in postoperative opioid prescribing and that patients are at risk of chronic opioid abuse after surgery. The factors that influence prescribing, however, remain obscure. This study investigates whether day of the week or the postoperative day at the time of discharge impacts prescribing patterns.

METHODS

We identified patients who underwent commonly performed procedures at our institution from January 2014 through April 2019 and analyzed the relationship between postoperative opioids prescribed (oral morphine milligram equivalents) and both the day of the week and the postoperative day at discharge.

RESULTS

In ambulatory operations (n = 13,545), each day progressing from Monday was associated with increased morphine milligram equivalents prescribed on discharge (P = .0080). For inpatient cases (n = 10,838), surgeons prescribed more morphine milligram equivalents at discharge in the latter half of the week and during the weekend (P = .0372). Every additional postoperative day at discharge was associated with a +19.25 morphine milligram equivalent prescribed (P < .0001).

CONCLUSION

More opioids were prescribed on discharges later in the week and after prolonged hospital stays perhaps to avoid patients running out of medication. Providers may unintentionally allow such non-clinical factors to influence postoperative opioid prescribing. Increased awareness of these inadvertent biases may help decrease excess prescribing of potentially addicting opioids after an operation.

Repeated Cesarean Delivery Predicted a Higher Risk of Inadequate Analgesia Than Primary Cesarean Delivery: A Retrospective Study with Propensity Score Match Analysis

Purpose

This study aimed to compare the analgesic outcomes between primary and repeated cesarean delivery.

Patients and Methods

We performed a retrospective analysis based on the medical records of a teaching hospital in China from January 2018 to March 2019. We collected data on demographic characteristics, perioperative complications, anesthesia, and surgical factors for cesarean delivery patients. We also recorded the postoperative analgesic strategy, pain intensity (assessed by the number rating scale) during the first 48 hrs after surgery, hospital cost, and hospital stay. Postoperative inadequate analgesia was defined by a score of ≥ 4 in the number rating scale. Analgesic outcomes after cesarean delivery between primiparas and multiparas were compared using propensity score matching analysis. Moreover, subgroup logistic analysis for different age groups (≥ 35 and < 35 years) was performed to investigate the effect of the maternal category on postoperative inadequate analgesia.

Results

A total of 1543 patients were included in the analysis and 571 pairs (1142 patients) were matched in the primiparas and multiparaparas group according to their propensity score. In both the non-matched and matched cohort, the incidence of inadequate analgesia in the primiparas group was lower than that in the multiparas group (16.7% vs. 24.0%, P < 0.001 and 16.1% vs. 23.5%, P = 0.002; respectively). The multiparas group was identified as being at risk of inadequate analgesia after cesarean delivery in both age groups (age ≥ 35 years, odds ratio: 2.18, 95% confidence interval: 1.20–3.95; age < 35 years, odds ratio: 1.43, 95% confidence interval 1.08–1.89).

Conclusion

Multiparas that undergo a repeat cesarean delivery had a significantly higher risk of inadequate postoperative pain treatment than primiparas. The maternal category should be considered when formulating the postoperative analgesia strategy after cesarean delivery.

Inpatient Pain Scores and Narcotic Utilization Based on American Society of Anesthesiologists Score Following Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective.

OBJECTIVE

To examine the relationship between American Society of Anesthesiologists (ASA) score and inpatient pain and narcotics consumption following anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Higher ASA scores have been previously linked to increased postoperative complication rates, healthcare costs, length of stay, and hospital readmissions. However, to our knowledge, there have not been previous investigations into the association between ASA scores and postoperative inpatient pain and narcotics utilization following ACDF.

METHODS

Patients who underwent a single-level, primary ACDF were retrospectively reviewed and stratified into two cohorts based on ASA score less than or equal to 2 or ASA score more than 2. ASA score was tested for association with demographic variables and perioperative characteristics using student's t test, chi-squared analysis, and Fisher exact test. Inpatient pain scores and narcotics consumption on each postoperative day were then compared between cohorts using bivariate linear regression.

RESULTS

Two hundred eleven patients who underwent ACDF were included: 184 had an ASA score less than or equal to 2 and 27 had an ASA score more than 2. Higher ASA score was associated with older age, higher comorbidity burden as measured by the modified Charlson Comorbidity Index (CCI), and lower prevalence of obesity. Higher ASA scores were associated with longer duration of hospital stay, while other perioperative characteristics were similar between ASA score cohorts. There were no differences in inpatient Visual Analog Scale (VAS) pain scores, or hourly, daily, and cumulative inpatient narcotic consumption between cohorts on any postoperative day.

CONCLUSION

This retrospective investigation demonstrated that a higher ASA score is associated with increased operative time following ACDF. However, ASA score was determined not to be an independent risk factor that can predict postoperative pain or narcotics consumption among patients who undergo ACDF. Therefore, postoperative pain in the inpatient setting can be managed with similar modalities regardless of ASA score for patients undergoing ACDF.

LEVEL OF EVIDENCE

3.

In-hospital opioid consumption, but not pain intensity scores, predicts 6-month levels of pain catastrophizing following hepatic resection: A trajectory analysis

BACKGROUND

The study aims were to model acute pain intensity and opioid consumption trajectories up to 72 hr after open hepatic resection, identify predictors of trajectory membership and examine the association between trajectory memberships and 6-month pain and psychological outcomes. This is a long-term analysis of a published randomized controlled trial on the impact of medial open transversus abdominis plane catheters on post-operative outcomes.

METHODS

A total of 152 patients (89 males; mean age 63.0 [range: 54-72]) completed questionnaires on pain and related characteristics pre-operatively and 6 months post-operatively. Total opioid use was recorded several times over a 72-hr period while self-reported pain intensity scores were collected multiple times until hospital discharge. Analyses were carried out using growth mixture modelling, logistic regression and general linear models.

RESULTS

Both pain intensity and opioid consumption showed that a four-trajectory model best fits the data. Patients in the lowest opioid consumption trajectory were more likely to be classified in the constant mild pain intensity trajectory. Age and baseline levels of anxiety significantly predicted opioid trajectory membership while baseline depressive symptoms significantly predicted pain intensity trajectory membership. Patients in the two highest opioid consumption trajectories reported significantly higher levels of pain catastrophizing at 6 months compared to patients in the other 3 trajectories (all p < 0.05).

CONCLUSION

High consumption of opioids after surgery is associated with higher levels of pain catastrophizing 6 months later. Identification of patients within these trajectories may lead to the development of early interventions targeted to high risk individuals.

SIGNIFICANCE

Differences in initial levels of opioid consumption and rates of change in opioid consumption shortly after surgery can help predict long-term psychological responses to pain. Identifying key characteristics associated with initial opioid consumption can lead to the development of cost-effective early interventions targeted to high risk individuals.

Postoperative pain management in patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis: a narrative review

Posterior spinal fusion for adolescent idiopathic scoliosis is one of the most invasive surgical procedures performed in children and adolescents. Because of the extensive surgical incision and massive tissue trauma, posterior spinal fusion causes severe postoperative pain. Intravenous patient-controlled analgesia with opioids has been the mainstay of postoperative pain management in these patients. However, the use of systemic opioids is sometimes limited by opioid-related side effects, resulting in poor analgesia. To improve pain management while reducing opioid consumption and opioid-related complications, concurrent use of analgesics and analgesic modalities with different mechanisms of action seems to be rational. The efficacy of intrathecal opioids and nonsteroidal anti-inflammatory drugs as components of multimodal analgesia in scoliosis surgery has been well established. However, there is either controversy or insufficient evidence regarding the use of other analgesic methods, such as continuous ketamine infusion, perioperative oral gabapentin, acetaminophen, continuous wound infiltration of local anesthetics, a single dose of systemic dexamethasone, and lidocaine infusion in this patient population. Moreover, appropriate combinations of analgesics have not been established. The aim of this literature review is to provide detailed information of each analgesic technique so that clinicians can make appropriate choices regarding pain management in patients with adolescent idiopathic scoliosis undergoing posterior spinal fusion.

Correlation Between 24-Hour Predischarge Opioid Use and Amount of Opioids Prescribed at Hospital Discharge

Importance

The United States is experiencing an opioid abuse epidemic. Opioid overprescription by physicians may contribute to this epidemic.

Objectives

To determine if there was a correlation between a postoperative patient's 24-hour predischarge opioid use and the amount of opioids prescribed at hospital discharge and to determine the number of patients who used no opioids prior to discharge but were still prescribed opioids after hospital discharge.

Design, Setting, and Participants

This cross-sectional study performed a retrospective record review of 18 343 postoperative patients at Boston Medical Center and Lahey Hospital and Medical Center-Burlington Campus who were discharged home after a postoperative inpatient admission of at least 24 hours. Data collection spanned from May 22, 2014, to June 30, 2016, in the Boston Medical Center data set and from March 23, 2015, to September 7, 2016, in the Lahey Hospital and Medical Center-Burlington Campus data set.

Exposures

Surgery requiring a postoperative inpatient hospital stay longer than 24 hours.

Main Outcomes and Measures

The main outcome measures were the patient's 24-hour predischarge opioid use and the total quantity of opioids prescribed at hospital discharge. Potential overprescription was defined as the number of patients who used no opioids in the 24 hours prior to hospital discharge but were still prescribed opioids after hospital discharge.

Results

Among the 18 343 patients (10 069 women and 8274 men; mean age, 52.2 years) who underwent 21 452 surgical procedures, there was wide variation in the amount of opioids prescribed at hospital discharge given a postoperative patient's 24-hour predischarge opioid use. A total of 6548 patients (35.7%) used no opioids in the 24 hours prior to hospital discharge; however, 2988 of these patients (45.6%) were prescribed opioids at hospital discharge, suggesting potential overprescription. Services that had the highest rates of potential overprescription (obstetrics [adjusted odds ratio (AOR), 3.146; 95% CI, 2.094-4.765] and gynecology [AOR, 2.355; 95% CI, 1.663-3.390], orthopedics [AOR, 0.943; 95% CI, 0.719-1.242], and plastic surgery [AOR, 0.733; 95% CI, 0.334-1.682]) generally had the highest rates of patients still using opioids at hospital discharge. Pediatric surgery was the only service that did not have any cases of potential overprescription (AOR, 2.09 × 10-7; 95% CI, 0.000-0.016).

Conclusions and Relevance

Opioids are not regularly prescribed in a patient-specific manner to postoperative patients. Potential opioid overprescription occurs regularly after surgery among almost all surgical specialties.

Evaluation of pain relief sufficiency using the Cumulative Analgesic Consumption Score (CACS) and its modification (MACS)

Postoperative pain is one of the major complications in general and bariatric surgery, associated with ongoing problems such as ileus, pneumonia and prolonged mobilization. In this study, patients undergoing bariatric surgery were analyzed according to their postoperative pain relief regime. In one group patients were treated with a patient-controlled analgesia (PCA) device, while the other group was treated with oral and intravenous analgesic medication. The aim of this study was to analyze which postoperative pain relief therapy would be more appropriate. We chose the Cumulative Analgesic Consumption Score (CACS) and Numeric Rating Scale (NRS) for pain measurement. For better comparison, we performed a modification of CACS according to PCA treatment. We observed better pain relief in the PCA group. Furthermore, we observed an advantage of treatment with laxatives in patients treated with PCA. In conclusion, PCA devices are appropriate instruments for postoperative pain relief in bariatric patients. CACS is a practical tool for postoperative pain measurement, describing individual pain sensation more objectively, although holding further potential in modification.

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.

Postoperative pain and patient-controlled epidural analgesia-related adverse effects in young and elderly patients: a retrospective analysis of 2,435 patients

In this retrospective study, data of 2,435 patients who received fentanyl and ropivacaine-based patient-controlled epidural analgesia (PCEA) for pain relief after elective surgery under general or spinal anesthesia were reviewed. Differences in postoperative pain, incidence of patient-controlled analgesia (PCA)-related adverse effects, and risk factors for the need for rescue analgesics for 48 hours postsurgery in young (age 20–39 years) and elderly (age ≥70 years) patients were evaluated. Although there were no significant differences in postoperative pain intensity between the two groups until 6 hours postsurgery, younger patients experienced greater postoperative pain intensity compared with older patients 6–48 hours postsurgery. While younger patients exhibited greater incidence of numbness, motor weakness, and discontinuation of PCA postsurgery, elderly patients exhibited greater incidence of hypotension, nausea/vomiting, rescue analgesia, and antiemetic administration. Upon multivariate analysis, low fentanyl dosage and history of smoking were found to be associated with an increased need for rescue analgesia among younger patients, while physical status classification III/IV and thoracic surgery were associated with a decreased need for rescue analgesia among the elderly. Discontinuation of PCA was more frequent among younger patients than the elderly (18.5% vs 13.5%, P=0.001). Reasons for discontinuation of PCA among young and elderly patients, respectively, were nausea and vomiting (6.8% vs 26.6%), numbness or motor weakness (67.8% vs 11.5%), urinary retention (7.4% vs 8.7%), dizziness (2.2% vs 5.2%), and hypotension (3.1% vs 20.3%). In conclusion, PCEA was more frequently associated with numbness, motor weakness, and discontinuation of PCA in younger patients and with hypotension, nausea/vomiting, and a greater need for rescue analgesics/antiemetics among elderly patients. Therefore, in order to minimize the adverse effects of PCEA and enhance pain relief, different PCEA regimens and administration/prevention strategies should be considered for young and elderly patients.

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.

Prediction of Patient-Controlled Analgesic Consumption: A Multimodel Regression Tree Approach

Several factors contribute to individual variability in postoperative pain, therefore, individuals consume postoperative analgesics at different rates. Although many statistical studies have analyzed postoperative pain and analgesic consumption, most have identified only the correlation and have not subjected the statistical model to further tests in order to evaluate its predictive accuracy. In this study involving 3052 patients, a multistrategy computational approach was developed for analgesic consumption prediction. This approach uses data on patient-controlled analgesia demand behavior over time and combines clustering, classification, and regression to mitigate the limitations of current statistical models. Cross-validation results indicated that the proposed approach significantly outperforms various existing regression methods. Moreover, a comparison between the predictions by anesthesiologists and medical specialists and those of the computational approach for an independent test data set of 60 patients further evidenced the superiority of the computational approach in predicting analgesic consumption because it produced markedly lower root mean squared errors.

Effects of local and spinal administrations of mu-opioids on postoperative pain in aged versus adult mice

Introduction

Suboptimal management of postoperative pain leads to increased risk of chronic opioid therapy, especially in elderly patients.

Objectives

Although this age-dependent phenomenon has been observed clinically, basic mechanisms including baseline nociception, postoperative hypersensitivity, and mu-opioid efficiency in aged animals have never been evaluated.

Methods

We tested these criteria using incision model on adult (3–6 months) and aged (24 months) mice to assess translatability of postoperative animal studies to clinical observations.

Results

Thermal and mechanical testing revealed lower baseline nociception in aged vs adult mice, while behavioral assays after hind paw plantar incision showed similar hypersensitivity levels for both age groups. Efficiency of local and spinal mu-opioid injections on postoperative pain was assessed next. DAMGO, a pure mu-opioid, was effective in reducing postoperative hypersensitivity in aged and adult mice, although adult mice displayed increased sensitivity to higher doses (50 μg local; 1–15 μg spinal). Buprenorphine, a mixed mu-opioid agonist, produced dose-dependent antihypersensitivity with adult mice more sensitive to lower doses (0.1 μg local; 0.02 μg spinal), and aged mice more sensitive to higher doses (1, 10 μg local; 0.1, 1 μg spinal). Finally, exploratory locomotor activity was used to evaluate the suppression of incision-induced spontaneous pain by DAMGO. Spinal and systemic (intraperitoneal) DAMGO inhibited ongoing pain more in adults compared with aged mice.

Conclusion

As in humans, baseline nociception was lower in aged vs adult mice, while postoperative hypersensitivity magnitudes were comparable between groups. Unlike in humans, adult mice were more sensitive to mu-opioids, although higher doses of mixed mu-opioids were more effective for postoperative antihypersensitivity in aged mice.

Human Genetic Variability Contributes to Postoperative Morphine Consumption

High interindividual variability in postoperative opioid consumption is related to genetic and environmental factors. We tested the association between morphine consumption, postoperative pain, and single nucleotide polymorphisms (SNPs) within opioid receptor μ 1 (OPRM1), catechol-O-methyltransferase (COMT), uridine diphosphate glucose-glucuronosyltransferase-2B7, and estrogen receptor (ESR1) gene loci to elucidate genetic prediction of opioid consumption. We analyzed 20 SNPs in 201 unrelated Caucasian patients who underwent abdominal surgery and who were receiving postoperative patient-controlled analgesia-administered morphine. Morphine consumption and pain intensity were dependent variables; age and sex were covariates. A haplotype of 7 SNPs in OPRM1 showed significant additive effects on opioid consumption (P = .007); a linear regression model including age and 9 SNPs in ESR1, OPRM1, and COMT explained the highest proportion of variance of morphine consumption (10.7%; P = .001). The minimal model including 3 SNPs in ESR1, OPRM1, and COMT explained 5% of variance (P = .007). We found a significant interaction between rs4680 in COMT and rs4986936 in ESR1 (P = .007) on opioid consumption. SNPs rs677830 and rs540825 of OPRM1 and rs9340799 of ESR1 were nominally associated with pain Numeric Rating Scale scores. Combinations of genetic variants within OPRM1, COMT, and ESR1 better explain variability in morphine consumption than single genetic variants. Our results contribute to the development of genetic markers and statistical models for future diagnostic tools for opioid consumption/efficacy.

PERSPECTIVE

This article presents the efforts dedicated to detect correlations between the genetic polymorphisms and the clinical morphine effect self-administered by patients using a patient-controlled analgesia pump after major surgery. The clinical effect is expressed in terms of morphine consumption and pain scores. REGISTERED ON CLINICALTRIALS.GOV: NCT01233752.

Contribution of Endogenous Spinal Endomorphin 2 to Intrathecal Opioid Antinociception in Rats Is Agonist Dependent and Sexually Dimorphic

Interactions between exogenous and endogenous opioids are not commonly investigated as a basis for sexually dimorphic opioid analgesia. We investigated the influence of spinal endomorphin 2 (EM2), an endogenous mu-opioid receptor (MOR) ligand, on the spinal antinociception produced by intrathecally administered opioids. Activation of spinal MORs facilitated spinal EM2 release. This effect was sexually dimorphic, occurring in males but not in females. Although activational effects of testosterone were required for opioid facilitation of spinal EM2 release in males, the absence of this facilitation in females did not result from either insufficient levels of testosterone or mitigating effects of estrogens. Strikingly, in males, the contribution of spinal EM2 to the analgesia produced by intrathecally applied MOR agonists depended on their analgesic efficacy relative to that of EM2. Spinal EM2 released by the higher efficacy MOR agonist sufentanil diminished sufentanil's analgesic effect, whereas EM2 released by the lower efficacy morphine had the opposite effect on spinal morphine antinociception. Understanding antithetical contributions of endogenous EM2 to intrathecal opioid antinociception not only enlightens the selection of opioid medications for pain management but also helps to explain variable sex dependence of the antinociception produced by different opioids, facilitating the acceptance of sexually dimorphic antinociception as a basic tenet.

PERSPECTIVE

The male-specific MOR-coupled enhancement of spinal EM2 release implies a parallel ability to harness endogenous EM2 antinociception. The inferred diminished ability of females to utilize the spinal EM2 antinociceptive system could contribute to their greater frequency and severity of chronic pain syndromes.

The cumulative analgesic consumption score (CACS): evaluation of a new score to describe postsurgical analgesic consumption as a surrogate parameter for postoperative pain and invasiveness of surgical procedures

OBJECTIVE

To validate and evaluate the applicability of a new score to describe postsurgical analgesic consumption in urological and surgical patients across different categories of pain medications and the invasiveness of medical interventions.

MATERIALS AND METHODS

The cumulative analgesic consumption score (CACS) was determined for two cohorts of patients split into three groups with surgeries involving clinically distinct levels of invasiveness (n = 2 x 60). Nonparametric statistical analyses were performed to determine differences between the CACS among the different groups and to assess the correlation between CACS and numeric rating scale (NRS) values for pain intensity.

RESULTS

The score was determined for postoperative days 1 and 2 and revealed median scores of 0 (0-11), 3 (0-22) and 10 (6-17) for UA (urological patients from group A), UB (group B) and UC (group C), respectively, and 4 (0-20), 8 (0-38) and 17 (7-68) for SA (surgical patients from group A, SB (group B) and SC (group C), respectively. CACS enabled reliable differentiation between groups involving different levels of invasiveness (p < 0.001). CACS and peak NRS values showed variable degrees of correlation, as expressed by levels of significance ranging from p < 0.001 to p = 0.34 (NS).

CONCLUSIONS

The CACS is a valid and easily applicable tool to describe postsurgical analgesic consumption in urological and surgical patients. It can be used as a surrogate parameter to assess postsurgical pain and the invasiveness of surgical procedures. These aspects may be measured to compare surgical procedures, in both clinical trials and clinical practice settings.

Preoperative predictors of postoperative opioid usage, pain scores, and referral to a pain management service in total knee arthroplasty

BACKGROUND

Little is known about preoperative predictors of postoperative pain and referral to a recuperative pain management service after total knee arthroplasty (TKA).

QUESTIONS/PURPOSES

We sought to identify the preoperative predictors of postoperative pain scores, referral to a pain management service, and narcotic usage in patients undergoing primary total knee arthroplasty.

METHODS

We performed a prospective cohort study of 97 TKAs from a single surgeon. Pre and 6-week postoperative WOMAC, visual analog pain scale (VAS) scores, narcotic usage, and catastrophizing pain scores were collected.

RESULTS

After adjusting for all other variables, higher age and catastrophizing pain scores were associated with lower odds of postoperative opioid usage. Increasing age and BMI were associated with lower odds of being referred to pain management. There was no relationship between self-reported preoperative pain tolerance and postoperative change in WOMAC or VAS pain scores.

CONCLUSIONS

This information may help surgeons advise their patients preoperatively and set expectations during the recovery period.

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 the incidence of severe pain events following surgery: a review of 333,000 pain scores

OBJECTIVE/BACKGROUND

Prior work has not addressed sex differences in the incidence of severe postoperative pain episodes. The goal of this study was to examine sex differences in clinical postoperative pain scores across an array of surgical procedures using direct comparisons of numeric rating scale pain scores as well as using the incidence of severe pain events (SPEs).

DESIGN/SETTING

Retrospective cohort study of over 300,000 clinical pain score observations recorded from adult patients undergoing nonambulatory surgery at a tertiary care academic medical center over a 1-year period.

METHODS/PATIENTS

To test the hypothesis that the number of SPE on postoperative day (POD) 1 differed by sex after controlling for procedure, we calculated Cochran-Mantel-Haenszel statistics of sex by count of SPE, controlling for type of surgery.

ASSESSMENT TOOLS/OUTCOMES

Pain scores were collected from clinical nursing records where they were documented using the numeric rating scale.

RESULTS

In female patients, 10,989 (25.09%) of 43,806 POD 1 pain scores were considered SPE compared with 10,786 (22.45%) of 48,055 POD 1 pain scores in male patients. This produced an overall odds ratio of 1.16 (99% confidence interval 1.11-1.20) for females vs males to report an SPE for a pain score on POD 1. Estimates of the odds that a given pain observation represents an SPE for female vs male patients after controlling for type of surgery yielded an odds ratio of 1.14 (99% confidence interval, 1.10-1.19).

CONCLUSION

Female patients experience greater mean pain scores, as well as a higher incidence of SPE, on POD 1 for a variety of surgical procedures.

Preoperative predictors of pain following total knee arthroplasty

Total knee arthroplasty has provided dramatic improvements in function and pain for the majority of patients with knee arthritis, yet a significant proportion of patients remain dissatisfied with their results. We performed a prospective analysis of 215 patients undergoing TKA who underwent a comprehensive array of evaluations to discover whether any preoperative assessment could predict high pain scores and functional limitations postoperatively. Patients with severe pain with a simple knee range-of-motion test prior to TKA had a 10 times higher likelihood of moderate to severe pain at 6 months. A simple test of pain intensity with active flexion and extension preoperatively was a significant predictor of postoperative pain at 6 months after surgery. Strategies to address this particular patient group may improve satisfaction rates of TKA.

Procedure-specific risk factor analysis for the development of severe postoperative pain

BACKGROUND

Many studies have analyzed risk factors for the development of severe postoperative pain with contradictory results. To date, the association of risk factors with postoperative pain intensity among different surgical procedures has not been studied and compared.

METHODS

The authors selected precisely defined surgical groups (at least 150 patients each) from prospectively collected perioperative data from 105 German hospitals (2004-2010). The association of age, sex, and preoperative chronic pain intensity with worst postoperative pain intensity was studied with multiple linear and logistic regression analyses. Pooled data of the selected surgeries were studied with random-effect analysis.

RESULTS

Thirty surgical procedures with a total number of 22,963 patients were compared. In each surgical procedure, preoperative chronic pain intensity and younger age were associated with higher postoperative pain intensity. A linear decline of postoperative pain with age was found. Females reported more severe pain in 21 of 23 surgeries. Analysis of pooled surgical groups indicated that postoperative pain decreased by 0.28 points (95% CI, 0.26 to 0.31) on the numeric rating scale (0 to 10) per decade age increase and postoperative pain increased by 0.14 points (95% CI, 0.13 to 0.15) for each higher score on the preoperative chronic pain scale. Females reported 0.29 points (95% CI, 0.22 to 0.37) higher pain intensity.

CONCLUSIONS

Independent of the type and extent of surgery, preoperative chronic pain and younger age were associated with higher postoperative pain. Females consistently reported slightly higher pain scores regardless of the type of surgery. The clinical significance of this small sex difference has to be analyzed in future studies.

Does preoperative risk for delirium moderate the effects of postoperative pain and opiate use on postoperative delirium?

OBJECTIVES

To investigate whether preoperative risk for delirium moderates the effect of postoperative pain and opioids on the development of postoperative delirium.

DESIGN

Prospective cohort study.

SETTING

University medical center.

PARTICIPANTS

Patients 65 years of age or older scheduled for major noncardiac surgery.

MEASUREMENTS

A structured interview was conducted preoperatively and postoperatively to determine the presence of delirium, defined using the Confusion Assessment Method. We first developed a prediction model to determine which patients were at high versus low risk for the development of delirium based on preoperative patient data. We then computed a logistic regression model to determine whether preoperative risk for delirium moderates the effect of postoperative pain and opioids on incident delirium.

RESULTS

Of 581 patients, 40% developed delirium on days 1 or 2 after surgery. Independent preoperative predictors of postoperative delirium included lower cognitive status, a history of central nervous system disease, high surgical risk, and major spine and joint arthroplasty surgery. Compared with the patients at low preoperative risk for developing delirium, the relative risk for postoperative delirium for those in the high preoperative risk group was 2.38 (95% confidence interval: 1.67-3.40). A significant three-way interaction indicates that preoperative risk for delirium significantly moderated the effect of postoperative pain and opioid use on the development of delirium. Among patients at high preoperative risk for development of delirium who also had high postoperative pain and received high opioid doses, the incidence of delirium was 72%, compared with 20% among patients with low preoperative risk, low postoperative pain, and those who received low opioid doses.

CONCLUSIONS

High levels of postoperative pain and using high opioid doses increased risk for postoperative delirium for all patients. The highest incidence of delirium was among patients who had high preoperative risk for delirium and also had high postoperative pain and used high opioid doses.

Integrative acupoint stimulation to alleviate postoperative pain and morphine-related side effects: a sham-controlled study

BACKGROUND

Although it can be reduced, postoperative pain remains a problem. Acupressure with electric stimulation may be more effective for postoperative pain management than acupressure alone.

OBJECTIVES

This study aimed to evaluate the effects of integrative acupoint stimulation (IAS) on the relief of postoperative pain and on the reduction of morphine-related side effects.

DESIGN

A single-blinded, sham-controlled study with three groups.

SETTING

An orthopedic ward in a 2900-bed teaching medical center.

PARTICIPANTS

Forty-five subjects in each of three groups.

METHODS

Each subject received a multimedia course on patient-controlled analgesia (PCA) before surgery to learn about the use of narcotic analgesics and the operation of the PCA device. Treatment was as follows: (1) for the IAS group, auricular acupressure combined with transcutaneous electric acupoint stimulation (TEAS) at the true acupoint; (2) for the sham group, acupoint stimulation in the same manner but at a sham acupoint or without embedding seeds and pressure; (3) for the control group, no IAS intervention.

RESULTS

Pain scores were significantly lower in the IAS group than the other two groups at 2h and 4h after returning to the ward, and 24h after surgery. The analgesic requirement during the 72h after surgery and the overall incidence of morphine-related side effects were significantly lower in the IAS group.

CONCLUSION

The study demonstrates that combined auricular acupressure and TEAS decreased postoperative pain, the use of equianalgesic morphine, and morphine-related side effects. IAS provides better analgesia when used in conjunction with PCA after lumbar spine surgery and can be regarded as a component of multimodal analgesia.

Decision tree-based learning to predict patient controlled analgesia consumption and readjustment

Background

Appropriate postoperative pain management contributes to earlier mobilization, shorter hospitalization, and reduced cost. The under treatment of pain may impede short-term recovery and have a detrimental long-term effect on health. This study focuses on Patient Controlled Analgesia (PCA), which is a delivery system for pain medication. This study proposes and demonstrates how to use machine learning and data mining techniques to predict analgesic requirements and PCA readjustment.

Methods

The sample in this study included 1099 patients. Every patient was described by 280 attributes, including the class attribute. In addition to commonly studied demographic and physiological factors, this study emphasizes attributes related to PCA. We used decision tree-based learning algorithms to predict analgesic consumption and PCA control readjustment based on the first few hours of PCA medications. We also developed a nearest neighbor-based data cleaning method to alleviate the class-imbalance problem in PCA setting readjustment prediction.

Results

The prediction accuracies of total analgesic consumption (continuous dose and PCA dose) and PCA analgesic requirement (PCA dose only) by an ensemble of decision trees were 80.9% and 73.1%, respectively. Decision tree-based learning outperformed Artificial Neural Network, Support Vector Machine, Random Forest, Rotation Forest, and Naïve Bayesian classifiers in analgesic consumption prediction. The proposed data cleaning method improved the performance of every learning method in this study of PCA setting readjustment prediction. Comparative analysis identified the informative attributes from the data mining models and compared them with the correlates of analgesic requirement reported in previous works.

Conclusion

This study presents a real-world application of data mining to anesthesiology. Unlike previous research, this study considers a wider variety of predictive factors, including PCA demands over time. We analyzed PCA patient data and conducted several experiments to evaluate the potential of applying machine-learning algorithms to assist anesthesiologists in PCA administration. Results demonstrate the feasibility of the proposed ensemble approach to postoperative pain management.

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.

Predictors of postoperative movement and resting pain following total knee replacement

This study determined preoperative predictors of movement and resting pain following total knee replacement (TKR). We hypothesized that younger patients with higher preoperative pain intensity, pain sensitivity, trait anxiety, pain catastrophizing, and depression would be more likely to experience higher postoperative movement pain than older patients with lower scores on these variables prior to surgery, and that predictors would be similar for resting pain. Demographics, analgesic intake, anxiety, depression, pain catastrophizing, resting pain, movement pain (ie, during active knee range of motion), and quantitative sensory tests were performed preoperatively on 215 participants scheduled for a unilateral TKR. On postoperative day 2, analgesic intake, resting pain, and movement pain were again assessed. Significant predictors of moderate or severe movement pain were higher preoperative movement pain, von Frey pain intensity, and heat pain threshold. People with severe movement pain preoperatively were 20 times more likely to have severe movement pain postoperatively. When the influence of preoperative movement pain was removed, depression became a predictor. Significant predictors of moderate to severe resting pain were higher preoperative resting pain, depression, and younger age. These results suggest that patients with higher preoperative pain and depression are more likely to have higher pain following TKR, and younger patients may have higher resting pain. Cutaneous pain sensitivity predicted movement pain but not resting pain, suggesting that mechanisms underlying movement pain are different from resting pain. Aggressive management of preoperative pain, pain sensitivity, and depression prior to surgery may facilitate postoperative recovery.

Pain sensitivity and opioid analgesia: a pharmacogenomic twin study

Opioids are the cornerstone medication for the management of moderate to severe pain. Unfortunately, vast inter-individual differences in dose requirements complicate their effective and safe clinical use. Mechanisms underlying such differences are incompletely understood, are likely multifactorial, and include genetic and environmental contributions. While accumulating evidence suggests that variants of several genes account for some of the observed response variance, the relative contribution of these factors remains unknown. This study used a twin paradigm to provide a global estimate of the genetic and environmental contributions to inter-individual differences in pain sensitivity and analgesic opioid effects. Eighty one monozygotic and 31 dizygotic twin pairs successfully underwent a computer-controlled infusion with the μ-opioid agonist alfentanil in a single occasion, randomized, double-blind and placebo-controlled study design. Pain sensitivity and analgesic effects were assessed with experimental heat and cold pressor pain models along with important covariates including demographic factors, depression, anxiety, and sleep quality. Significant heritability was detected for cold pressor pain tolerance and opioid-mediated elevations in heat and cold pressor pain thresholds. Genetic effects accounted for 12-60% of the observed response variance. Significant familial effects accounting for 24-32% of observed variance were detected for heat and cold pressor pain thresholds and opioid-mediated elevation in cold pressor pain tolerance. Significant covariates included age, gender, race, education, and anxiety. Results provide a strong rationale for more detailed molecular genetic studies to elucidate mechanisms underlying inter-individual differences in pain sensitivity and analgesic opioid responses. Such studies will require careful consideration of the studied pain phenotype.

Does using a femoral nerve block for total knee replacement decrease postoperative delirium?

Background

The effect of peripheral nerve blocks on postoperative delirium in older patients has not been studied. Peripheral nerve blocks may reduce the incidence of postoperative opioid use and its side effects such as delirium via opioid-sparing effect.

Methods

A prospective cohort study was conducted in patients who underwent total knee replacement. Baseline cognitive function was assessed using the Telephone Interview for Cognitive Status. Postoperative delirium was measured using the Confusion Assessment Method postoperatively. Incidence of postoperative delirium was compared in two postoperative management groups: femoral nerve block ± patient-controlled analgesia and patient-controlled analgesia only. In addition, pain levels (using numeric rating scales) and opioid use were compared in two groups.

Results

85 patients were studied. The overall incidence of postoperative delirium either on postoperative day one or day two was 48.1%. Incidence of postoperative delirium in the femoral nerve block group was lower than patient controlled analgesia only group (25% vs. 61%, P = 0.002). However, there was no significant difference between the groups with respect to postoperative pain level or the amount of intravenous opioid use.

Conclusions

Femoral nerve block reduces the incidence of postoperative delirium. These results suggest that a larger randomized control trial is necessary to confirm these preliminary findings.

Prediction of postoperative pain using path analysis in older patients

PURPOSE

Effective postoperative pain management is important for older surgical patients because pain affects perioperative outcomes. A prospective cohort study was conducted to describe the direct and indirect effects of patient risk factors and pain treatment in explaining levels of postoperative pain in older surgical patients.

METHODS

We studied patients who were 65 years of age or older and were scheduled for major noncardiac surgery with a postoperative hospital stay of at least 2 days. The numeric rating scale (0 = no pain, 10 = worst possible pain) was used to measure pain levels before surgery and once daily for 2 days after surgery. Path analysis was performed to examine the association between predictive variables and postoperative pain levels.

RESULTS

Three hundred fifty patients were studied. We found that preoperative pain level, use of preoperative opioids, female gender, higher ASA physical status, and postoperative pain control methods were the strongest predictors of postoperative pain as measured on the first day after surgery. Younger age, greater preoperative symptoms of depression, and lower cognitive function also contributed to higher postoperative pain levels. Pain levels on the second day after surgery were strongly predicted by preoperative pain level, use of preoperative opioids, surgical risk, and pain and opioid dose on postoperative day 1. However, younger age, female gender, higher ASA physical status, greater preoperative symptoms of depression, lower cognitive function, and postoperative pain control methods indirectly contributed to pain levels on the second day after surgery.

CONCLUSION

Although preoperative pain and use of preoperative opioids have the strongest effects on postoperative pain, clinicians should be aware that other factors such as age, gender, surgical risk, preoperative cognitive impairment, and depression also contribute to reported postoperative pain. Based on significant statistical correlations, these study results can contribute to more effective postoperative care for those patients having the risk factors studied here. Preoperative treatment/intervention based in part on factors such as preoperative pain, use of preoperative opioids, and depression may improve postoperative pain management.