Arulvelan Appavoo, Manikandan Sethuraman, Easwer Hari V, Krishnakumar Kesavapisharady
Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, Kerala, India.
J Neurosurg Anesthesiol. 2015 Oct;27(4):289-94. doi: 10.1097/ANA.0000000000000159.
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.
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.
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.
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.
右美托咪定已广泛应用于神经麻醉和重症监护环境。右美托咪定对颅内病变患者脑血管自动调节和血流动力学的影响尚不明确。本研究旨在解决这一问题。
本研究纳入了15例单侧幕上胶质细胞瘤患者（S组）和15例无任何颅内病变的患者（C组）。两组均采用经颅彩色多普勒对双侧进行短暂充血反应测试。在基线时以及在10分钟内输注注射用右美托咪定（1 mcg/kg）后，用短暂充血反应比（THRR）和自动调节强度（SA）评估动态自动调节。
给予负荷剂量右美托咪定后，有肿瘤的半球（S组）的THRR和SA值与基线相比无差异（P = 0.914，0.217）。在S组的无肿瘤半球以及C组的双侧半球中，给予负荷剂量右美托咪定后，THRR和SA值均显著降低（P < 0.001）。与非病变半球相比，肿瘤半球的THRR值更高（P < 0.001），提示存在基线充血的可能性。
在有胶质细胞瘤的半球中，右美托咪定后自动调节指标无显著变化。这可能是由于血管结构异常及其对右美托咪定的反应性改变，或者是由于基线充血本身，但确切机制有待阐明。在非病变半球中，THRR和SA值降低，提示使用负荷剂量右美托咪定后自动调节受损。
