Optimizing the Treatment of CRPS With Ketamine.

OBJECTIVE: This study aimed to develop a method that objectively measures the clinical benefits of ketamine infusions to treat complex regional pain syndrome (CRPS), thus making it possible, for the first time, to determine the optimal dosing of ketamine and duration of treatment to treat CRPS. MATERIALS AND METHODS: All patients were diagnosed with hyperalgesia associated with CRPS. Patients underwent an outpatient, 4-day, escalating dose ketamine infusion. Hyperalgesia was measured using pain thresholds. Clinical outcome was determined without knowledge of the patient's pain thresholds throughout treatment. RESULTS: We found a correlation between pain thresholds and the intensity of pain reported by the patient at various sites of the body. We found that clinical outcomes correlated with improvement in pain thresholds. There was a plateau in pain thresholds between days 3 and 4 for the lower extremities. There was no plateau in pain thresholds observed for the upper extremities. DISCUSSION: Our findings suggest that 4 days of treatment are sufficient for the treatment of CRPS of the lower extremities. For the upper extremities, >4 days may be required. Our study is the first to utilize quantitative sensory testing to direct the treatment of a chronic pain disorder.

Rate and Risk Factors Associated With Prolonged Opioid Use After Surgery: A Systematic Review and Meta-analysis.

Importance: Prolonged opioid use after surgery may be associated with opioid dependency and increased health care use. However, published studies have reported varying estimates of the magnitude of prolonged opioid use and risk factors associated with the transition of patients to long-term opioid use. Objectives: To evaluate the rate and characteristics of patient-level risk factors associated with increased risk of prolonged use of opioids after surgery. Data Sources: For this systematic review and meta-analysis, a search of MEDLINE, Embase, and Google Scholar from inception to August 30, 2017, was performed, with an updated search performed on June 30, 2019. Key words may include opioid analgesics, general surgery, surgical procedures, persistent opioid use, and postoperative pain. Study Selection: Of 7534 articles reviewed, 33 studies were included. Studies were included if they involved participants 18 years or older, evaluated opioid use 3 or more months after surgery, and reported the rate and adjusted risk factors associated with prolonged opioid use after surgery. Data Extraction and Synthesis: The Meta-analysis of Observational Studies in Epidemiology (MOOSE) and Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines were followed. Two reviewers independently assessed and extracted the relevant data. Main Outcomes and Measures: The weighted pooled rate and odds ratios (ORs) of risk factors were calculated using the random-effects model. Results: The 33 studies included 1 922 743 individuals, with 1 854 006 (96.4%) from the US. In studies with available sex and age information, participants were mostly female (1 031 399; 82.7%) and had a mean (SD) age of 59.3 (12.8) years. The pooled rate of prolonged opioid use after surgery was 6.7% (95% CI, 4.5%-9.8%) but decreased to 1.2% (95% CI, 0.4%-3.9%) in restricted analyses involving only opioid-naive participants at baseline. The risk factors with the strongest associations with prolonged opioid use included preoperative use of opioids (OR, 5.32; 95% CI, 2.94-9.64) or illicit cocaine (OR, 4.34; 95% CI, 1.50-12.58) and a preoperative diagnosis of back pain (OR, 2.05; 95% CI, 1.63-2.58). No significant differences were observed with various study-level factors, including a comparison of major vs minor surgical procedures (pooled rate: 7.0%; 95% CI, 4.9%-9.9% vs 11.1%; 95% CI, 6.0%-19.4%; P = .20). Across all of our analyses, there was substantial variability because of heterogeneity instead of sampling error. Conclusions and Relevance: The findings suggest that prolonged opioid use after surgery may be a substantial burden to public health. It appears that strategies, such as proactively screening for at-risk individuals, should be prioritized.