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Background Intravenous ketamine has been established as an efficacious and safe treatment, with transient effect, for treatment resistant depression. However, the effectiveness of intravenous ketamine in non-research settings and with ultraresistant depression patients remains understudied.
Aims: This study aims to measure the response and remission rates in ultraresistant depression patients in a clinical setting by means of a retrospective, open label, database study. Secondarily, the study will attempt to support previous findings of clinical predictors of effectiveness with intravenous ketamine treatment.
Methods: Fifty patients with ultraresistant depression were treated between May 2015 and December 2016, inclusive, in two community hospitals in Edmonton using six ketamine infusions of 0.5mg/kg over forty minutes over two to three weeks. Data were collected retrospectively from inpatient and outpatient charts. Statistical analysis to investigate clinical predictors of effectiveness included logistic regression analysis using a dependent variable of a 50% reduction in rating scale score at any point during treatment.
Results: At baseline, the average treatment resistance was severe, with a MSM score of 12.1 out of 15, 90.0% were resistant to ECT, and the average BDI score was 34.2. The response rate was 44% and remission rate was 16%. As a single predictor, moderate or severe anhedonia at baseline predicted a 55% increased likelihood of response.
Conclusion: In a clinical setting, intravenous ketamine showed effectiveness in a complex, severely treatment resistant, depressed population on multiple medication profiles concurrently. This study gave support to anhedonia as a clinical predictor of effectiveness.