Refractory pain treated with intrathecal drug delivery systems (IDDS) is an effective option for chronic pain patients unresponsive to more conservative therapies (1 ). Bupivacaine continuous infusion mixed with opioids or alone, is considered an appropriated option for chronic neuropathic pain(2,3 ). New devices for patient controlled intrathecal analgesia (PCIA) have emerged to improve results of IDDS. Bupivacaine has a therapeutical potential, to improve pharmacokinetic and increase analgesia (4)
Clinical case report of a 42 YO male patient with complete spinal cord lesion pain at T12 level, refractory to medical management , who received IDDS (SynchroMed®8627EL, Medtronic Inc.), tip of catheter at T11-T12 level. He had adequate analgesic response, with continuous infusion of hydromorphone 50 microgr/day + Bupivacaine 3mg/day. After approximately 4 years, he lost pain control and his pain increased. Pump integrity system was reviewed, and failure ruled out to explain refractoriness to treatment. When increasing opioid dose, side effects limited this therapeutic option.
In order to avoid a higher daily dose of Bupivacaine and maintain acceptable pump refill times, we decided to adapt a device (Medtronic myPTM® Model 8835) to patient pump, starting with very low doses of Bupivacaine (0.2mg bolus/ 5 boluses on demand/day) , in adittion to his daily continuous IDDS scheme. Patient was instructed in using this device (figure 1). After 3 days of treatment, patient reduced his frequency paroxisms and severity of pain NRS = 2/10.
We observed that addition of very low dose boluses of Bupivacaine on top of the continuous infusion by mean of PCIA programming modality (4), resulted in significant pain control, without adverse effects. . After 3 months with this new regimen, his previous pump needed replacement due to battery exhaustion, and we were able to continue this regimen, maintaining stable his opioid+bupivacaine continuous daily dose.
Very low dose of bupivacaine pulses (less than 0.5mg), in PCIA, compared to those described previously in literature (5), may have potential benefit on pain control for patients with refractory pain. To the best of our knowledge, such an observation has neither been reported for neuropathic pain in spinal cord injury patient. Theories such as a “current” effect of pulsatile bupivacaine (6), or a “priming” effect of a continuous infusion plus boluses, can explain this response (7). This result may decrease the risk of bupivacaine taquiphilaxis or haemodynamic effects in this population.