• Check all stopcocks. Ensure that all stopcocks are open to both the drainage unit and to the patient catheter (the system is open in any direction where one of the stopcock "prongs" are pointed). 

• Ensure that the "0" on the drainage unit panel is positioned at the external auditory canal, and the arrow on the drainage collecting chamber is positioned at the correct position above the head. 
• Note that drainage will only occur if a) the system is open, and b) the ICP exceeds the level of the drainage unit.  For example, if the unit is positioned at 10 cmH20 above the patient's head (which is equal to 7.4 mmHg), the ICP must be higher than 10 cmH20 (or higher than 7.4 mmHg on the bedside monitor) before drainage will occur.
• NOTE: To ensure that the ICP measurement obtained is accurate, the ICP reading should be taken when the stopcock is closed to drainage and open between the pressure system and the patient catheter.  Pressure measurements that are obtained when the stopcock is opened to both drainage and monitoring can be inaccurate (they would reflect a blended pressure from both the patient catheter AND the drainage bag versus an ICP from the patient catheter alone). 

• To check for catheter patency, lower the drainage chamber below the patient's head (ensuring that the drainage system remains vertical).  If the catheter is patent, CSF drainage should occur. 
• Evaluate the ICP waveform. 
• Ensure that an appropriate scale is selected to ensure good visibility of the waveform. 
• If the catheter is patent, a crisp waveform should be present; the waveform should demonstrate pressure changes that correspond to the heart rhythm. 
• A flat waveform suggests that the catheter is not patent. Note that if the ICP increases significantly, brain edema could obstruct the catheter tip and impair waveform transmission.
• To confirm that an increase in the ICP accurately reflects raised intracranial pressure, observe the patient for other findings that support the ICP reading such as: bradycardia, hypertension, pupillary dilation, any other neurological deterioration or a reduction in the SjO2.

NOTE: If the cause of the problem is either #3 or #4, the problem requires medical intervention (i.e. catheter flushing or medical intervention to treat the ICP).