昏迷患者脑水含量的实时估计。
Real time estimation of brain water content in comatose patients.
机构信息
Department of Neurology, Seoul National University Hospital, Seoul, South Korea.
出版信息
Ann Neurol. 2012 Sep;72(3):344-50. doi: 10.1002/ana.23619. Epub 2012 Aug 22.
OBJECTIVE
Although brain swelling is an important cause of neurological deterioration, real time measurement of brain edema does not currently exist. Because thermal conductivity is proportional to percentage water content, we used the thermal conductivity constant to estimate brain water content (BWC).
METHODS
Between June 2008 and November 2010, 36 comatose brain-injured patients underwent cerebral blood flow monitoring using a thermal diffusion probe in our neurocritical care unit. BWC was estimated hourly utilizing the measured thermal conductivity and the known temperature-adjusted thermal conductivity of water. In vitro experiments were performed to validate this formula using agar, glycerol, and water mixtures with different water content.
RESULTS
Thermal conductivity was highly correlated (R(2) = 0.99) and estimated water content was well correlated with actual water content (mean difference, 0.58%) in the in vitro preparations. The majority of the 36 patients (median age, 57 years; 44% female) had subarachnoid hemorrhage (n = 14) or cardiac arrest (n = 9). Initial BWC at the time of monitoring ranged from 67.3 to 85.5%. Brain regions appearing edematous on computed tomography showed higher estimated BWC than normal-appearing brain regions (79.1 vs 70.2%; p < 0.01). Bolus osmotherapy (20% mannitol or 23.4% hypertonic saline) decreased BWC from 77.2 ± 0.7% (mean ± standard error) at baseline to 76.1 ± 0.5% at 1 hour, 76.5 ± 0.3% at 2 hours, and 76.7 ± 0.2% at 3 hours (all p ≤ 0.03).
INTERPRETATION
Real time monitoring of BWC is feasible using thermal conductivity. Further studies are needed to confirm the clinical utility of this technique.
目的
尽管脑水肿是神经功能恶化的一个重要原因，但目前尚不存在实时测量脑水肿的方法。由于热导率与含水量成正比，我们使用热导率常数来估计脑水含量（BWC）。
方法
在 2008 年 6 月至 2010 年 11 月期间，我们在神经重症监护病房对 36 例昏迷的脑损伤患者使用热扩散探头进行了脑血流监测。利用测量的热导率和已知的经温度调整的水的热导率常数，每小时估算一次 BWC。通过使用琼脂、甘油和不同含水量的水混合物进行了体外实验来验证该公式。
结果
在体外制剂中，热导率具有高度相关性（R²=0.99），估算的水含量与实际水含量（平均差异为 0.58%）具有良好的相关性。36 例患者中的大多数（中位年龄为 57 岁，44%为女性）患有蛛网膜下腔出血（n=14）或心搏骤停（n=9）。监测时的初始 BWC 范围为 67.3%至 85.5%。CT 显示水肿的脑区比正常脑区的估计 BWC 更高（79.1%比 70.2%；p<0.01）。推注渗透性治疗（20%甘露醇或 23.4%高渗盐水）使 BWC 从基线时的 77.2±0.7%（均值±标准误差）下降至 1 小时时的 76.1±0.5%、2 小时时的 76.5±0.3%和 3 小时时的 76.7±0.2%（均 p≤0.03）。
结论
使用热导率实时监测 BWC 是可行的。需要进一步的研究来证实该技术的临床应用价值。
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