Background Chronic pain is usually refractory to treatment. Ketamine is often used to treat chronic refractory pain.In France most of the patients are treated in pain units day hospital.

This study aims to evaluate the effectiveness of continuous four days of Ketamine infusion associated with magnesium sulfate for inpatients.

Methods A total of 89 patients received a 4 days continuous subanesthetic IV ketamine infusion associated with 1000 mg/day of magnesium sulfate.Primary outcome was mean pain intensity (Numerical Rating Pain Scale) 30 days after infusion. Patient Impression of Change (PGIC), Anxiety and depression (HADS), Neuropathic Pain (NPSI), quality of life (SF-12) were secondary outcomes.

Results Ketamine continuous infusion was associed with decrease of NRS (7.54 ± 1.35 at d0 to 5.59 ± 2.2 at d30 [26%; p < 0.001]).The PGIC improved in 68.7 % patients (36.2 % reports “much improved” or “very much improved”).There was a significant decrease of Npsi total score (−28% ; p < 0.0001) and an increase of SF12 (Mental health dimension from 31.4 ±7.9 to 36.4 ± 8.9 [+15.9 % ; p < 0.0001]; Physical health dimension from 30.2 ± 6.7 to 32.8 ± 6.8 [+8.6% ; p:0.0007]).The mean HADS Depression decreased from 10 ± 4.5 at d0 to 8.2 ± 4.6 at d30 (−15% ; p:0.0012) ; The mean HADS Anxiety decreased from 11.35 ± 4.7 at d0 to 9.38 ± 4.5 at d30 (−14% ; p < 0.0001).

Conclusions Findings suggests that continuous low-dose infusion of ketamine is effective for chronic pain relief to inpatients.

The authors have declared no competing interest.

NCT06131970

This study did not receive any funding

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The study was conducted in accordance with the Declaration of Helsinki, approved by the local Ethics Committee (centre hospitalier princesse grace)IRB equivalent : 2022-RC-04 in 05/09/2022 and written informed consent was obtained from all participants before procedure.

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