Background

The invasive nature of the current methods for monitoring of intracranial pressure (ICP) has prevented their use in many clinical situations. Several attempts have been made to develop methods to monitor ICP non-invasively. The aim of this study is to assess the relationship between ultrasound-based non-invasive ICP (nICP) and invasive ICP measurement in neurocritical care patients.

Methods and findings

This was a prospective, single-cohort observational study of patients admitted to a tertiary neurocritical care unit. Patients with brain injury requiring invasive ICP monitoring were considered for inclusion. nICP was assessed using optic nerve sheath diameter (ONSD), venous transcranial Doppler (vTCD) of straight sinus systolic flow velocity (FV_sv), and methods derived from arterial transcranial Doppler (aTCD) on the middle cerebral artery (MCA): MCA pulsatility index (PI_a) and an estimator based on diastolic flow velocity (FV_d). A total of 445 ultrasound examinations from 64 patients performed from 1 January to 1 November 2016 were included. The median age of the patients was 53 years (range 37–64). Median Glasgow Coma Scale at admission was 7 (range 3–14), and median Glasgow Outcome Scale was 3 (range 1–5). The mortality rate was 20%. ONSD and FV_sv demonstrated the strongest correlation with ICP (R = 0.76 for ONSD versus ICP; R = 0.72 for FV_sv versus ICP), whereas PI_a and the estimator based on FV_d did not correlate with ICP significantly. Combining the 2 strongest nICP predictors (ONSD and FV_sv) resulted in an even stronger correlation with ICP (R = 0.80). The ability to detect intracranial hypertension (ICP ≥ 20 mm Hg) was highest for ONSD (area under the curve [AUC] 0.91, 95% CI 0.88–0.95). The combination of ONSD and FV_sv methods showed a statistically significant improvement of AUC values compared with the ONSD method alone (0.93, 95% CI 0.90–0.97, p = 0.01). Major limitations are the heterogeneity and small number of patients included in this study, the need for specialised training to perform and interpret the ultrasound tests, and the variability in performance among different ultrasound operators.

Conclusions

Of the studied ultrasound nICP methods, ONSD is the best estimator of ICP. The novel combination of ONSD ultrasonography and vTCD of the straight sinus is a promising and easily available technique for identifying critically ill patients with intracranial hypertension.

中文翻译：

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超声非侵入性测量神经重症监护中的颅内压：一项前瞻性观察研究

背景

当前用于监测颅内压（ICP）的方法具有侵入性，因此无法在许多临床情况下使用它们。已经进行了数种尝试来开发无创监测ICP的方法。这项研究的目的是评估神经重症监护患者中基于超声的无创ICP（nICP）与有创ICP测量之间的关系。

方法和发现

这是对接受三级神经重症监护病房的患者进行的前瞻性单队列观察性研究。需要侵入性ICP监测的脑损伤患者被认为包括在内。NICP使用视神经鞘直径（ONSD）评估，静脉经颅多普勒直窦收缩期流速（vTCD）（FV _SV），并从动脉经颅多普勒（aTCD）在大脑中动脉（MCA）衍生的方法：MCA搏动指数（PI _a）和基于舒张流速（FV _d）的估计。）。包括2016年1月1日至11月1日对64例患者进行的445次超声检查。患者的中位年龄为53岁（范围37-64）。入院时格拉斯哥昏迷量表的中位数为7（范围3–14），格拉斯哥成果中量表的中位数为3（范围1-5）。死亡率为20％。ONSD和FV _sv与ICP的相关性最强（ONSD与ICP的R = 0.76；FV _sv与ICP的R = 0.72 ），而PI _a和基于FV _d的估算器与ICP的相关性不明显。结合使用2个最强的nICP预测因子（ONSD和FV _sv），可以得出与ICP（R= 0.80）。ONSD的颅内高压（ICP≥20 mm Hg）检测能力最高（曲线下面积[AUC] 0.91，95％CI 0.88-0.95）。与仅使用ONSD方法相比，ONSD和FV _sv方法的组合显示了AUC值的统计学显着改善（0.93，95％CI 0.90-0.97，p = 0.01）。主要的局限性是本研究包括异质性和少数患者，需要进行专门培训以执行和解释超声检查的方法，以及不同超声操作者之间性能的差异。

结论

在研究的超声nICP方法中，ONSD是ICP的最佳估计值。ONSD超声检查和直窦的vTCD的新颖结合是一种有前途且容易获得的技术，可用于识别重症颅内高压患者。