Therapeutic Effects of 7- to 14-Day Subanesthetic Ketamine Infusions for Chronic Pain on Standardized Psychiatric Measures

Abstract

Background: We have previously shown that subanesthetic ketamine infusions effectively reduce refractory pain. However, the effects of ketamine infusions on comorbid conditions of depression and anxiety have not been explored in this patient population. Methods: We investigated the effects of ketamine on mood and anxiety in patients with refractory chronic pain treated with 7–14 days of subanesthetic continuous intravenous ketamine infusions, using well-validated clinical scales. Results: There was a significant 52% reduction in pain severity and 33% reduction in pain interference scores following ketamine treatment. Ketamine treatment also reduced scores on the depression module of the Patient Health Questionnaire (PHQ-9) by 28% and scores on the Generalised Anxiety and Depression Assessment (GAD-7) by 36%. Conclusion: Multiday subanesthetic ketamine infusions effectively reduce pain, anxiety and depression in patients with complex chronic pain.

Plain language summary

What questions did we seek to answer?

Chronic pain is a common problem with limited effective treatments. We have previously shown that supervised, multiday ketamine treatments given in the hospital can effectively reduce pain levels, with benefit for months for patients with persistent chronic pain. However, pain is quite complex and often co-occurs with other conditions, particularly depression and anxiety. We aimed to investigate how our ketamine infusions would impact these two important classes of disorder. We assessed our patients with chronic pain undergoing ketamine treatments using thoroughly researched clinical measures of pain, mood and anxiety before and after the infusions.

What were the results?

Patients had significant reductions in the standardized measures of pain and anxiety, and improvements in mood. We statistically checked whether these reductions were related, and found that reduced pain levels did not correlate with improvements in mood and anxiety levels.

What do the results suggest?

Ketamine treatments given in a carefully monitored hospital setting are effective in reducing anxiety and improving mood in patients undergoing treatment for chronic pain. The absence of a correlation between the change in pain levels and the change in anxiety and depression levels suggests that ketamine might affect different parts of the brain to achieve these independent effects.

Tweetable abstract

A new study reveals multiday ketamine infusions in hospitals can effectively reduce pain while improving mood and reducing anxiety in patients suffering from refractory chronic pain.

Keywords::

• anxiety
• central sensitization syndrome
• chronic pain
• depression
• ketamine infusions

Author contributions

All authors contributed substantially to the conception and design of this project, including in drafting and revision of the article. All authors granted final approval and are responsible for the content included in the manuscript.

Acknowledgments

The authors would like to acknowledge the facilities and support provided by St. Paul’s Hospital.

Financial & competing interests disclosure

S Marzoughi received the Ludmila & Henry Zeldowicz Award 2022 from the University of British Columbia in part to support his research efforts. D Ripsman received financial support from the Dr Barbara Allan Scholarship in Medicine 2022 from the University of British Columbia in part to fund his research efforts. This research received no grants from any funding agency in the public, commercial, or not-for-profit sectors. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Additional information

Funding

S Marzoughi received the Ludmila & Henry Zeldowicz Award 2022 from the University of British Columbia in part to support his research efforts. D Ripsman received financial support from the Dr Barbara Allan Scholarship in Medicine 2022 from the University of British Columbia in part to fund his research efforts. This research received no grants from any funding agency in the public, commercial, or not-for-profit sectors. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.