Effect of Loading Dose of Dexmedetomidine on Dynamic Cerebral Blood Flow Autoregulation in Patients With Intracranial Glial Neoplasms.

BACKGROUND: Dexmedetomidine has been widely used in neuroanesthesia and critical care settings. The effects of dexmedetomidine on cerebral vascular autoregulation and hemodynamics in patients with intracranial pathology are not well defined. This study is aimed to address this issue.

METHODS: Fifteen patients with unilateral supratentorial glial tumor (group S) and 15 patients without any intracranial pathology (group C) were included in this study. Transient hyperemic response testing was conducted bilaterally in both groups with transcranial color Doppler. Dynamic autoregulation was assessed with transient hyperemic response ratio (THRR) and strength of autoregulation (SA) at baseline and after infusion of inj. dexmedetomidine (1 mcg/kg) over 10 minutes.

RESULTS: THRR and SA values in the hemisphere that had tumor (group S) showed no difference from baseline after a loading dose of dexmedetomidine (P=0.914, 0.217). In the nontumor hemisphere of group S and in both the hemispheres of group C, significant reduction in THRR and SA values were observed (P<0.001) after administration of a loading dose of dexmedetomidine. THRR values were higher in the tumor hemisphere when compared with the nonpathologic hemispheres (P<0.001), suggesting the possibility of baseline hyperemia.

CONCLUSIONS: In the hemisphere that had glial tumor, autoregulatory indices showed no significant change after dexmedetomidine. It can be because of abnormal vascular architecture and its altered reactivity to dexmedetomidine, or because of baseline hyperemia itself, but the exact mechanism needs to be elucidated. In the nonpathologic hemispheres, THRR and SA values were decreased, suggesting impaired autoregulation with the use of loading dose of dexmedetomidine.