Finding the vulnerable postoperative population: A two-step cluster analysis of the PAIN-OUT registry.

BACKGROUND: Identifying predictors of poor postoperative outcomes is crucial for planning personalized pain treatments. The aim of this study was to examine pain outcomes using cluster analysis in N = 2678 patients from the PAIN-OUT registry at first postoperative day. METHODS: Indicator variables of the clustering analysis assessed multiple domains, such as clinical and surgical conditions, analgesic-anaesthetic variables, desire for more pain treatment and outcome variables of the International Pain Outcome Questionnaire (IPO) summarized as factor scores. RESULTS: Two-step cluster identified the three-cluster solution as the optimal. Two empirical groups (C1 and C2) included patients with good postoperative outcomes discriminated by peripheral nerve block use, while the other cluster (C3) grouped patients with the worst outcomes, where all patients desired more pain treatment. C3 comprised about 20% of the participants, mostly lower limb, abdominal and spine procedures. The best predictors of belonging to C3 included younger age, being male, preoperative opioid use, bone and fracture reduction procedures, institution, number of comorbidities and morphine equivalents in the recovery room. CONCLUSIONS: IPO factor scores can be used to select pain outcomes phenotypes in large clinical databases. Most of the predictors were present before the recovery period so perioperative planning should focus in the preoperative and intraoperative periods. SIGNIFICANCE: Improvement of postoperative pain requires assessment methods that go beyond pain intensity scores. We perform a cluster analysis among PAIN-OUT patients that revealed a cluster of vulnerable postoperative patients, using a novel composite measure of postoperative outcomes: the factor scores of the International Pain Outcomes Questionnaire. By changing the focus from pain intensity to multidimensional pain outcomes, male gender and number of comorbidities appeared as new risk factors for worse postoperative outcomes. The study also identified procedures that require urgent quality improvements.

Confirmatory factor analysis of the International Pain Outcome questionnaire in surgery.

BACKGROUND: Choosing perioperative suitable treatments requires reliable and valid outcome measurements. The International Pain Outcome (IPO) questionnaire has been widely used for quality improvement and research purposes within the PAIN-OUT network that has collected more than 550,000 data sets of postoperative patients in 200 hospitals worldwide. Our aim is to confirm psychometric properties of the Spanish version of the IPO questionnaire and its invariance by pain predictors. METHOD: Sample included 4014 participants within a large age range, who underwent different surgical procedures. Confirmatory factor analysis (CFA) assessed internal structure, considering invariance by sex, age, procedure, smoking, obesity, affective disorder, and chronic pain. Incremental predictive validity of factor scores on question would have liked more pain treatment and opioid requirement was also estimated with logistic binary regression. RESULTS: Confirmatory factor analysis verified original structure in 3 factors measuring pain intensity and interference (F1), adverse effects (F2), and perceptions of care (F3), with good internal consistency. Multigroup CFA analysis confirmed invariance by assessed pain predictors. Good incremental predictive capacity to identify would have liked more pain treatment was achieved. CONCLUSION: Our study confirms the factor structure, supports reliability, and adds some evidence of convergent validity of the Spanish adaptation of the IPO questionnaire. The sum of scores in its main factors serves a global outcome analysis tool. Low scores in F1 and F2 with high scores in F3 would indicate optimal quality of care.

Factors Associated With the Risk of Developing Moderate to Severe Acute Postoperative Pain After Primary Total Knee Arthroplasty: Results From the PAIN OUT Registry.

BACKGROUND: Total knee arthroplasty (TKA) is one of the most common procedures in orthopedic surgery and not always matches with patient's expectations of pain relief and function improvement. The aim of this study was to assess risk factors for developing moderate to severe acute postoperative pain (APOP) after TKA using the PAIN OUT questionnaire. METHODS: Prospective, multicentre, international cohort study within the PAIN OUT project. Patients' outcomes were measured with 11-point numerical rating scales (0 = null, 10 = worst possible). Patient and analgesic/anesthetic treatment were assessed. Odds ratio for moderate-severe pain was calculated for each variable and if they were statistically significant in the univariate logistic model, variables were fitted into a multivariate logistic regression model. The effect size was assessed by Cohen's d coefficient. RESULTS: In total, 968 patients were evaluated. The multivariate model identified chronic preoperative pain (P < .001), general anesthesia (P = .020), and receiving chronic opioids before (P = .020) or after the surgery (P < .001) as factors associated with moderate-severe APOP. No protective factors were observed. CONCLUSIONS: Our model identified several risk factors for APOP. From our results, preoperative chronic pain, general anesthesia and the use of opioid analgesics could be predictors for higher APOP. These findings may help establish new strategies for the treatment of pain in TKR. More studies should be carried out to identify acute pain predictors and to develop better strategies of pain management for risk patients.

Postoperative Pain Management in Spanish Hospitals: A Cohort Study Using the PAIN-OUT Registry.

Pain after surgery remains a problem worldwide, although there are no published data on postoperative outcomes in Spain. We evaluated 2,922 patients on the first day after surgery in 13 tertiary care Spanish hospitals, using the PAIN-OUT questionnaire. The aims were to: assess postoperative outcomes and anesthetic/analgesic management in Orthopedics (ORT) and General Surgery (GEN) patients; explore the influence of the analgesic therapy on outcomes and opioid requirements; evaluate and compare outcomes and analgesic management according to surgical procedure. Mean worst pain and percentage of patients in severe pain were 5.6 (on a numeric rating scale of 0-10) and 39.4%, respectively, slightly lower than those reported in Western countries (range, 5.0-8.4 and 33-55%). Patients' pain assessment (83.1%) and information were high (63.3%), but participation in decision-making (4.8) was lower than in the United States (7.0) and Europe (Germany, France, Norway, and Denmark; mean, 5.9). Patients after orthopedic surgery had the worst outcomes. General anesthesia was more frequent in GEN patients, whereas regional (central and peripheral) was more frequent in ORT surgery patients. Mean opioid consumption (20.2 mg per patient per 24 hours, oral morphine equivalents), was lower than reported and decreased >50% after regional analgesia. Intravenous morphine patient-controlled analgesia was seldom used (6.2%). Acute opioid treatments were associated with worsened outcomes whereas multimodal analgesia (mainly antipyretic analgesics-nonsteroidal anti-inflammatory drugs-opioids) were associated with improved results. Epidurals in abdominal surgery (16.7%) were also associated with better outcomes. Presurgical chronic pain (>7) and/or chronic opioid consumption, were associated with worsened pain outcomes; the latter with a 50% increase in postoperative opioid requirements. Tibia/fibula and foot surgeries (ORT), and gastric, small intestine, and anterior abdominal wall procedures (GEN) were the most painful. Rigorous control of chronic pain before surgery, and combining opioids with adjuvants and other analgesics perioperatively, might improve postoperative outcomes. PERSPECTIVE: We analyzed postoperative outcomes and analgesic management in patients from tertiary care Spanish hospitals. The study serves as a point of comparison with other Western countries and shows that pain intensity outcomes and opioid consumption were slightly better in the Spanish population. Chronic pain before surgery (numeric rating scale score >7) and/or chronic opioid consumption, were associated with worsened pain outcomes, suggesting that rigorous control of chronic pain before surgery, and combining opioids with adjuvants and other analgesics perioperatively, might improve outcomes. Patients' pain participation in decision-making was inadequate and should be improved in Spanish hospitals.