Intrathecal lidocaine elevates prostaglandin E2 levels in cerebrospinal fluid: a microdialysis study in freely-moving rats

Abstract

Background. In this study, we have investigated whether intrathecal (i.t.) lidocaine administration is accompanied with changes of cerebrospinal fluid (CSF) prostaglandin E 2 (PGE 2) levels. Methods. Rats were anaesthetized for i.t. implantation of a triple-lumen spinal loop dialysis catheter. CSF changes in PGE 2 after i.t. injection of saline, 400, or 1000 mg of lidocaine were measured. The impact of i.t. pretreatment with 5 mg MK801 (N-methyl-D-aspartate glutamate antagonist) or 10 mg SC76309A (COX-2 inhibitor) was also investigated. CSF dialysates for measurement of PGE 2 were collected for 4 h. During the whole procedure, motor and sensory blocks were evaluated. A separate group receiving i.t. lidocaine 400 mg (without dialysate sampling) was assessed for mechanical (Von Frey) and radiant heat pain. Results. PGE 2 levels increased to 400% of baseline and remained elevated for 90-120 min after i.t. lidocaine at both doses. Pretreatment with SC76309A and MK801 attenuated this increase. A 40 min period of enhanced pain response was observed after Von Frey filament stimulation during and after sensory and motor block recovery. Conclusions. I.T. lidocaine (400 or 1000 mg) increases PGE 2 levels in the CSF for 90-120 min along with a transient period of mechanical hyperalgesia after sensory and motor block recovery.