EFFECT OF DEXMEDETOMIDINE ON LUMBAR CEREBROSPINAL-FLUID PRESSURE IN HUMANS

Dexmodetomidine's potential for analgesia without respiratory depressi on and its opioid- and anesthetic-sparing properties make it an attrac tive choice as an anesthetic adjunct for patients undergoing neurosurg ery. However, the effects of dexmedetomidine on intracranial pressure are not known. We therefore studied the effect of dexmedetomidine on l umbar cerebrospinal fluid (CSF) pressure in patients after transphenoi dal pituitary tumor surgery. Sixteen transphenoidal pituitary tumor su rgery patients were randomized to receive placebo (n = 9) or dexmedeto midine (n = 7) for 60 min in the postanesthesia care unit. The study d rug was administered by a continuous computer-controlled infusion to a chieve an estimated plasma dexmedetomidine concentration of 600 pg/mL, the highest plasma concentration that has been used for clinical purp oses. Patient-controlled analgesia was used to administer morphine for postoperative discomfort. Lumbar CSF pressure (via lumbar intrathecal catheter), intraarterial blood pressure, and heart rate were monitore d continuously. There was no change in lumbar CSF pressure in either g roup. The highest values obtained were 19 mm Hg in the dexmedetomidine group and 20 mm Hg in the placebo group. During infusion, mean arteri al pressure decreased from 103 +/- 10 mm Hg to 86 +/- 6 mm Hg (P < 0.0 5), heart rate decreased from 77 +/- 12 bpm to 64 +/- 7 bpm (P < 0.05) , and cerebral perfusion pressure decreased from 95 +/- 8 mm Hg to 78 +/- 6 mm Hg (P < 0.05) in the dexmedetomidine group, but not in the pl acebo group. We conclude that dexmedetomidine does not have an effect on lumbar CSF pressure in patients with normal intracranial pressure w ho have undergone transphenoidal pituitary hypophysectomy. Implication s: The effects of dexmedetomidine (an alpha(2)-agonist) or placebo on lumbar cerebrospinal fluid pressure, measured via an intrathecal cathe ter, were studied postoperatively in 16 patients. Dexmedetomidine had no effect on lumbar cerebrospinal fluid pressure. We will continue to investigate the potential utility of dexmedetomidine for neurosurgical anesthesia.