THE EFFECT OF PRIOR DURAL PUNCTURE ON CEREBROSPINAL-FLUID SUFENTANIL CONCENTRATIONS IN SHEEP AFTER THE ADMINISTRATION OF EPIDURAL SUFENTANIL

Sufentanil is a highly lipid soluble opioid that provides potent analg esia when administered in the subarachnoid space. Unfortunately, the p enetration of sufentanil into the cerebrospinal fluid (CSF) after epid ural administration is poor, and limits its effectiveness for epidural analgesia. Dural puncture may enhance the movement of epidural sufent anil into the subarachnoid space and increase its effectiveness. To de termine whether the administration of epidural sufentanil adjacent to a dural puncture results in significantly greater CSF concentrations, 18 adult ewes were studied. Animals in the control group had an epidur al catheter placed at the superior border of the pelvis without dural puncture. Animals in the study group had an epidural catheter placed, followed by a dural puncture performed using an 18-gauge Touhy needle. The dural puncture was performed one interspace cephalad to the epidu ral catheter. One hour after dural puncture, each animal received a lo ading dose of 0.35 mu g/kg of sufentanil (5 mu g/mL) through the epidu ral catheter, followed by an infusion of epidural sufentanil 0.15 mu g .kg(-1).h(-1) for a period of 4 h. After 4 h, CSF was sampled from a s ite one interspace caudad to the epidural catheter as well as at the c isterna magna. The mean CSF concentration of sufentanil at the level o f the pelvis for animals with a dural puncture was 12.1 +/- 3.0 ng/mL compared with 1.8 ng/mL in controls with intact dura. Sufentanil conce ntrations at the cisterna magna were below the level of detection (0.0 8 ng/mL) for all animals in both groups. We conclude that an 18-gauge dural puncture significantly increases movement of sufentanil from the epidural to the intrathecal space. This increase in sufentanil concen tration at the level of the pelvis was not associated with detectable levels of sufentanil at the brainstem. Implications: This study addres ses the effect of dural puncture on spinal fluid concentrations of suf entanil after epidural administration. A sheep model was used to measu re drug concentrations in the spinal fluid at the levels of the pelvis and brainstem after epidural administration. Dural puncture significa ntly enhanced movement of sufentanil into the spinal fluid at the leve l of the pelvis, but brainstem concentrations were below the level of detection. Analgesic concentrations of spinal sufentanil in the clinic al setting, as well as brainstem concentrations associated with respir atory depression, have yet to be defined.