Analgesic efficacy of high-frequency spinal cord stimulation: a randomized double-blind placebo-controlled study.

INTRODUCTION: Spinal cord stimulation is a recognized treatment of chronic neuropathic and vascular pain. Recent data suggest that the use of very high-frequency (HF) stimulation modes does produce analgesia without paresthesia. AIM OF THE STUDY: To compare the efficacy of HF stimulation (HF spinal cord stimulation [HFSCS]) and sham stimulation on the patient's global impression of change (PGIC), pain intensity, and quality of life. PATIENTS AND METHODS: Forty patients who have achieved stable pain relief with conventional SCS have been recruited. After randomization, HFSCS and sham are initiated in a double-blind randomized two-period-crossover design. RESULTS: Complete data were available from 33 patients. The primary outcome was a minimal improvement in the PGIC. The proportion of patients responding under HFSCS was 42.4% (14/33 patients) vs. 30.3% (10/33 patients) in the sham condition. The mean benefit of HF vs. sham was not statistically significant with a proportion of 11.2% in favor of HFSCS (p = 0.30). There was a highly statistically significant "period effect," irrespective of treatment received, with 51.5% of patients (N = 17) improving at visit 3 vs. 21.2% (N = 7) at visit 5 (p = 0.006). The mean pain visual analog scale (VAS) on sham was 4.26 vs. 4.35 on HFSCS (p = 0.82) and the mean EuroQol five-dimensional (EQ-5D) index with HFSCS was 0.480 vs. 0.463 with sham (p = 0.78). CONCLUSION: This is the first randomized double-blind study on SCS. HFSCS was equivalent to sham for the primary outcome (improvement of PGIC) as well as for both the secondary outcomes (VAS and EQ-5D index). There was a highly statistically significant "period effect" (p = 0.006) with improved PGIC scores in the first study period regardless of the treatment. The same trend was seen for VAS and EQ-5D. It appears that the effect of HFSCS and sham is equal and only the order in the sequence, not the nature of the treatment, seems to dictate the effect.

Severe hypertension following accidental clonidine overdose during the refilling of an implanted intrathecal drug delivery system.

BACKGROUND: Complications associated with intrathecal pumps may be linked to the surgical procedure, the implanted device, or the medication itself. CASE REPORTS: Three patients treated chronically with intrathecal clonidine presented with clonidine overdose due to inadvertent extravasation during the refilling procedure. All patients experienced loss of consciousness and severe systemic hypertension that required aggressive parenteral treatment. DISCUSSION: Clonidine is an alpha-2 agonist with a nearly 100% bioavailability after oral or rectal administration. With high plasma concentration secondary to massive systemic overdose, the specificity for the alpha-2 receptor is lost and an alpha-1 agonist activity predominates and causes marked hypertension. Management of clonidine overdose consists of supportive therapy guided by signs and symptoms. CONCLUSION: Inadvertent injection into the subcutaneous pocket rather than the reservoir is rare but very dangerous as the drug cannot be retrieved and massive doses are involved. Signs and symptoms of systemic overdose with drugs commonly used in implanted drugs delivery system should be well known to ensure early diagnosis and treatment.