Pain and Quality of Life metrics following Use of Repeated Ketamine Infusion in Chronic Pain Patients.

Pain and Quality of Life metrics following Use of Repeated Ketamine Infusion in Chronic Pain Patients.

Background:

The use of ketamine in treating chronic pain in clinical and nonclinical settings has recently increased significantly (Crumb et al., 2018, Ricardi et al., 2023), primarily because of the ongoing opioid epidemic. Ketamine does not produce respiratory depression in clinical doses, which makes it advantageous over opioids. Low-dose ketamine infusion produces opioid-sparing effects in addition to reducing opioid tolerance. In chronic pain patients, it can decrease hyperalgesia and allodynia (Visser and Schug, 2006). Considering the potential antidepressant effects, ketamine may have other important roles in chronic pain patients (Cohen et al., 2018). Although it is well tolerated in clinical settings when benzodiazepines are used to alleviate the psychotropic effects, close monitoring of the use of ketamine is recommended due to its cardiovascular and CNS effects as well as the abuse potential.

Purpose/Objectives:

Low-dose infusion of ketamine in clinical settings produces good analgesia for neuropathic pain conditions. It is recommended for complex chronic pain because of the few contraindications and beneficial risk profile (Voute et al., 2022). Clinical research data is needed to guide evidence-based and regulatory decisions. This study was designed to answer the question; what are the long-term analgesic and quality of life effects following repeated ketamine infusion in chronic pain patients?

Method:

Using a retrospective study design, we studied 103 patients with chronic pain who returned for repeated ketamine infusions depending on when they needed it for pain control in a hospital pain clinic over 3.5 years. Other pain treatment modalities were stable. The pain was measured using the 0 to 10 scale. Quality of Life (QOL) responses were summarized on a 0 to 5 scale.

At each visit, data were obtained on the duration of previous pain relief, quality of life, and pain score before and after the infusion. The perceived attributable pain reduction (PAPR) was categorized as less than 50%, 50% -75%, or greater than 75%. The perceived duration of pain relief was categorized as less than one month, 1 -2 months, or greater than two months. Statistical analyses involved summary statistics for demographic data and examination of trends using scatter plots and linear regression.

Results:

The average age was 52 years (SD 13, IQR 42 – 63). 76% were female. At baseline, 103 participated, and a decreasing number returned for subsequent infusion, with only one returning for the maximum of 24^th visit over 3.5 years. The average change in pain score was 4/10. The median duration of relief was three weeks.

For the first visit, the post-infusion pain reduction was less than 50% in 41% of the 103 patients. 27% had a decrease between 50 to 75%, and 32% had a greater than 75% reduction. The number of patients reporting improved pain relief increased in subsequent visits. The change in pain score was not associated with the duration of relief.

78 (76%) of the 103 patients completed the QOL survey following the initial visit. The median QOL score following ketamine infusion was 3. Most patients reported improved QOL at baseline and in subsequent visits.

Conclusions: Subanesthetic doses of ketamine as an infusion effectively control pain over time. Over the course of 3.5 years, our study shows that the number of patients reporting pain relief lasting 1-2 months increased in subsequent visits. The change in pain score is not associated with the duration of relief. Most patients reported improved quality of life at baseline and in subsequent visits. These findings have to be taken in light of the study's limitations. This was a retrospective study based on chart review. Patients who opted to use ketamine infusion could have been self-selected and not representative of all chronic pain patients. In addition, the analgesic effects may be affected by the effects of other concomitant treatment agents, even if stable. A well-designed prospective study is needed to confirm these findings.

Disclosures: Nothing to disclose by any author.

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