Wong Frankie W H
Clinical Neurosciences Department, Calgary Zone Alberta Health Services, Calgary, AB.
Dynamics. 2011 Fall;22(3):19-24.
Intracranial pressure monitoring using an external ventricular drainage (EVD) system is the most commonly used technology to monitor intracranial pressure or drain cerebrospinal fluid (CSF) in neurological and neurosurgical patients. CSF samples are collected routinely from the EVD system for laboratory tests. No study has been conducted to identify where the most appropriate site for CSF collection is in order to reduce the disruption of the closed EVD system and reduce the risk of infection.
The purpose of this study was to identify a CSF sampling port in the EVD system that is easily accessible, provides accurate results, and minimizes disruption to the closed EVD system.
Fifty patients admitted to the neurological and neurosurgical intensive care step-down unit with the EVD system between July 2007 and September 2009 agreed to participate in the study. There were 21 women and 29 men. Forty-seven patients' data were analyzed.
The design was quasi-experimental using a convenience sample. Two samples of CSF were collected daily. One sample was collected from the proximal port and another sample was collected from the distal port. The second sample was collected immediately after the first. Each set of samples (proximal and distal) was tested and compared for any differences in appearance, culture results, and concentrations of protein, glucose, and white cell count.
Using a two-tailed paired t test with 95% confidence interval, there was no statistically significant difference between the samples obtained from the two collection sites for protein, glucose, white cell count, appearance, and culture. Pearson's correlation coefficient was also used to analyze the correlation for the continuous measures. Both protein and glucose had very high correlations. However, the white cell count, and white cell counts and culture had very low correlations.
The distal port of the EVD system is safe and easy for CSF collection. It also provides accurate results for CSF samples. When the CSF sample is collected from the distal port, the entire volume of CSF in the drip chamber should be collected and tested to obtain an accurate WBC count per unit of volume.
使用外部脑室引流（EVD）系统进行颅内压监测是神经科和神经外科患者监测颅内压或引流脑脊液（CSF）最常用的技术。脑脊液样本通常从EVD系统中采集用于实验室检测。尚未开展研究来确定脑脊液采集的最合适部位，以减少对封闭的EVD系统的干扰并降低感染风险。
本研究的目的是在EVD系统中确定一个易于操作、能提供准确结果且能最大程度减少对封闭EVD系统干扰的脑脊液采样端口。
2007年7月至2009年9月期间入住神经科和神经外科重症监护降级病房且使用EVD系统的50名患者同意参与本研究。其中女性21名，男性29名。分析了47名患者的数据。
采用便利样本的准实验设计。每天采集两份脑脊液样本。一份样本从近端端口采集，另一份样本从远端端口采集。第二份样本在第一份样本采集后立即采集。对每组样本（近端和远端）进行检测，并比较外观、培养结果以及蛋白质、葡萄糖和白细胞计数浓度的差异。
使用95%置信区间的双尾配对t检验，从两个采集部位获得的样本在蛋白质、葡萄糖、白细胞计数、外观和培养方面无统计学显著差异。还使用Pearson相关系数分析连续测量指标的相关性。蛋白质和葡萄糖的相关性都非常高。然而，白细胞计数以及白细胞计数与培养的相关性非常低。
EVD系统的远端端口用于脑脊液采集安全且简便。它也能为脑脊液样本提供准确结果。当从远端端口采集脑脊液样本时，应采集并检测滴壶中全部体积的脑脊液，以获得每单位体积准确的白细胞计数。
