Critical Care Trauma Centre




  1. System Overview
  2. Obtain Equipment
  3. Open Unit
  4. Prepare Panel
  5. Prime the Unit
  1. Position the Transducer
  2. Set Drainage Level
  3. Zero Transducer
  4. Connect to Patient
  5. Patient Monitoring


Nurses may prime and connect the intraventricular drainage system in CCTC.  All CSF draining catheters (intraventricular; lumbar ICP) must be connected to the Codmanä External Drainage System for safety.

Although EVD drains in CCTC are usually inserted using a microsensor technology, lumbar ICP monitoring is achieved through a fluid filled pressure monitoring circuit only. A standard transducer is used to measure pressure.


Reason for Monitoring Lumbar ICP

During thoracic aneurysm repair, blood flow to the thoracic and lumbar spines can become compromised during aortic cross clamping. Ischemia to the cord can lead to cord edema, which can cause the lumbar ICP to rise and impede normal flow of CSF within the spinal canal. If the lumbar ICP increases, drainage of lumbar CSF can reduce the risk of cord damage by reducing the pressure. Normal ICP is < 10 mmHg.

Thoracic or lumbar spinal cord damage causes paraplegia. In addition to ICP monitoring and drainage to maintain ICP below a target, hourly spinal cord assessment is required in the acute phase to promptly detect signs of cord impairment.  Edema can take ~48 hours to peak (following the last injury/ischemic insult). Document in the spinal section of CCTC flowsheet.

The Codman External Drainage System is a closed system for drainage and pressure monitoring of intracranial catheters. An antimicrobial filter located at the top of the graduated collecting chamber and bottom of the drainage collecting bag prevents backward flow of fluid or bacteria. The unit must hang upright at all times. If it is placed flat in a horizontal position, the filter at the top of the drip chamber can become wet, preventing the system from draining properly.

The panel has a "0" reference point that must be positioned at the level of the catheter (in CCTC, the lumbar spine is approximated as being level with the iliac crest in a patient lying supine). The drip chamber buretrol is then adjusted up or down until it is at a level equal to the maximum desired intracranial pressure.  Lumbar CSF pressure is normally equal to intracranial ICP. If the system is open to drainage, CSF will drain as soon as the pressure in the lumbar space exceeds the pressure determined by the height of the drip chamber above the catheter.

The Codman drainage unit uses 3-way stopcocks. . The stopcock can be opened in 3 directions simultaneously. The direction the prong points to represents the "off" position. This system may be utilized for continuous pressure monitoring alone, continuous drainage alone or continuous drainage and pressure monitoring. To obtain an accurate pressure measurement, the stopcock should be turned "off" to drainage and "open" to the patient catheter and pressure monitoring system.  If pressure is measured when the drainage unit is open in all 3 directions, the pressure measured will be a reflection of the patient and drainage bag.

With intracranial ICP monitoring, Cerebral Perfusion Pressure is calculated each hour to ensure that there is a sufficient pressure gradient to maintain cord perfusion. When monitoring lumbar ICP, a "Cord Perfusion Pressure" can be calculated each hour using the same formula.

Cord Perfusion Pressure = MAP - Lumbar ICP

A low blood pressure poses a serious risk to the spinal cord. Vascular orders include a target blood pressure that is generally higher than usual baseline orders.  If neurological finding develope or ICP is elevated, strategies to increase the systemic blood pressure will usually be ordered. This is to ensure an adequate perfusion pressure is provided to the spinal cord (as well as other vessels that come off of the thoracic and abdominal aorta).  Baseline hypertension is also common among patients undergoing aneurysm surgery.


Figure 1

The Drainage Unit ( Figure 1)

The panel (left) must be positioned in an upright position, with the "0" reference point (E) at the level of the patient's catheter. In CCTC, we use the iliac crest as the lumbar ICP reference point. 

The drip chamber is ordered to a level (in cmH20) to maintain a desired lumbar ICP (normal is the same as intracranial ICP if the bed position is flat). 

New orders may be required if the drainage output is higher than the maximum orders or if the ICP is below a minimum level.


Head of Bed

If the head of bed is flat or minimally elevated, the lumbar ICP should equal the intracranial ICP. ICP in the lumbar space may become higher if there is a flow obstruction due to cord edema.

HOB is usually kept close to flat to prevent overdrainage of intracranial CSF.  Overdrainage or excessive lower of the lumbar ICP can increase the risk for intracranial bleeding.


Figure 2

Buretrol Close-up (Figure 2)

  • Roller to adjust drip chamber up and down
  • Drainage tubing
  • Filter
  • Level of drainage (drip point)
  • Fluid collection
  • Arrow for alignment of drip chamber with level of desired pressure in cm H20 is the column to the right (red on panel) and mmHg is the column to the left (black on panel).



Figure 3


3-Way Stopcock (Figure 3)

The prong is pointing to pathways that are closed. This picture on the left displays the stopcock "open" to the patient, the drainage system and pressure monitoring.







Obtain Equipment

1.  Codman External Drainage System
2.  500 ml bag of 0.9% NaCl
3.  1 single transducer kit for arterial line
4.  IV pole
5.  Laser level (in CN cupboard)
or lasel level pen at CN desk.

6. Obtain PPE as required





Open Unit

Open package with Codman External Drainage Unit, being careful not to drop extension pieces out; extension pieces are loosely connected in package.



The connections are loosely attached to facilitate gas sterilization.


Prepare Panel

  1. Replace the vented white cap located on the mounting panel stopcock (at the "0" reference mark) with a dead-end luer lock cap (provided in kit).
  2. Turn the mounting panel stopcock with the flat side (off) toward the cap.

    Always leave the mounting panel stopcock in this position; if you wish to turn the stopcock open or closed to drainage, use the stopcock closest to the lumbar catheter.


This opens the system between the drainage tubing and drip chamber in preparation for flushing. 

By only adjusting one stopcock during use, the risk of accidental closure/opening of the system is reduced.



Prime the Unit

  1. Perform hand hygiene.
  2. Hang a bag of normal saline. 
  3. Using the normal saline, prime the pressure tubing as per setting up a hemodynamic system.
  4. Remove the extension piece at the distal end of the pressure tubing. 
  5. Remove the cap from the stopcock located at the end of the drainage tubing (this will be referred to as the "patient stopcock").
  6. Connect the distal end of the pressure tubing to the stopcock where the cap has been removed.  Be careful not to contaminate the connections.
  7. Turn the patient stopcock with flat side (off) towards the patient connection end of the circuit.
  8. Pull the flush device until the all air bubbles have been eliminated and fluid drips readily into the drip chamber.
  9. Turn the patient stopcock with the flat side (off) towards the drip chamber.
  10. Remove the unvented cap at the tip of the drainage tubing, being careful not to contaminate the end.
  11. Flush the circuit until all air has been expelled between the patient stopcock and end of drainage tubing. 
  12. Replace the unvented cap at the end of tubing and tighten. 
  13. Turn the patient stopcock to a 45 degree angle from the tip.




In accordance with the MoHLTC 4 moments of hand hygiene and LHSC infection control policies in an effort to reduce risk of transmission of microorganisms and secretions.

Heparin is not used due to risk of intracranial bleeding.  The system is not pressurized to avoid introducing fluid into the spinal fluid.

Once primed, the pressure tubing will be used to measure lumbar ICP.

The pressure tubing is connected to the stopcock closest to the patient to minimize the length of tubing that the pressure wave must travel. CSF drainage often contains blood and debris; adding the flush system at the patient stopcock allows the circuit to be flushed between the patient stopcock and the drip chamber as required to maintain patency and pressure transmission.

The entire circuit must be primed to facilitate drainage. Be careful to maintain aseptic technique; CSF contains glucose which promotes bacterial growth that can cause meningitis.

Tightening maintains sterility and prevents loss of priming fluid. A 45 degree angle on any stopcock ensures that it is "off" in all directions.



Position the Transducer

  1. Securely tape the transducer to the side of the mounting panel with the air fluid interface (the air evacuation port of the stopcock above the transducer) at the same horizontal position as the "0" reference on the mounting panel.
  2. Connect the transducer cable to the bedside monitor.
  3. Using the laser level, ensure that the "0" reference on the panel is level with the iliac crest if patient is supine.


Both the transducer and the mounting panel stopcock must be level with the lumbar space.

By securing both stopcocks at the same point, the transducer and mounting panel can be simultaneously referenced by adjustment of the mounting panel.



Set the Drainage Level

  1. Obtain an order for the level of the drainage chamber. 

  2. Orders should include a maximum CSF volume and both minimum and maximum lumbar ICP.

  3. Loosen the buretrol adjustment screw and move the drip chamber until the small arrow is aligned with the desired height.  

  4. Tighten the screw to secure the buretrol position.

NOTE: A typical order is "10 cmH20" above the lumbar space. The right hand column of numbers of the Codman drainage ujnit is in cmH20.  The column to the left is in mmHg (orders for drip chamber placement are usually in cmH20 - check with the physician to confirm the correct level). 

In the example of "10 cmH20", the system is correctly placed if the "0" reference point is level with the patient's iliac crest and the small arrow is aligned at the 10 cmH20 marking.   10 cmH20 =7.4 mmHg (bedside pressure measurement).

If the drain is in the open position, raising the head of bed can increases the pressure gradient between head and lumbar spine and can lead to over-drainage. Continuous drainage is safest with the HOB close to flat.

Excessive fluid removal or reduction in the intracranial pressure can increase the risk for intracranial bleeding.

Turn stopcock off temporarily when repositioning patient to prevent over-drainage. Recheck drain level and return to drainage position once patient's position has been stabilized.

A minimum ICP should be identified to prevent intracranial dehydration which may increase risk for bleeding.

Turn drain off to drainage if output exceeds ordered maximum (usually 10-20 ml/hr).If presure is low, an order to raise the drain level pr switch to intermittent drainage may be indicated.



If the "0" reference is level with the patient's catheter, a drainage level of 10 cmH20 above the lumbar space provides automatic "venting" of CSF if the pressure rises above 10 cmH20. 

If the "0" reference and the drip chamber are both positioned level with the catheter, drainage would occur the moment the lumbar CSF pressure > 0.  Normal lumbar CSF pressure is < 10 mmHg.  This could lead to over drainage and potential for cerebral bleeding.

Weaning of the drainage system can be done by raising the level of the drainage unit (the ICP would have to be higher before drainage would occur). Intermittent drainage may also be initiated, where pressure is monitored and drainage only opened if the pressure exceeds a specific level.

Both the patient and mounting panel stopcocks must be open between the patient's catheter and the drainage chamber for drainage to occur. When the system is left continuously open to drain and the drainage chamber is positioned to initiate drainage at a set level, pressure is maintained at a more consistent level. 

Note that the bedside monitor measures pressure in mmHg; 10 cmH20 is the same as 7.4 mmHg.  Thus, a properly positioned unit with the drip chamber at 10 cmH20 will drain if:

  • the stopcocks are open between the patient's catheter and the drip chamber
  • the pressure in the lumbar space exceeds 10 cmH20 (or exceeds 7.4 mmHg on the bedside monitor).
  • the catheter/circuit is patent (e.g. free of clot or debris)
  • there is fluid in the lumbar space (if the pressure is high due to cord edema, there may not be any CSF to drain)

If the circuit fails to drain despite a pressure on the monitor that is > than the level of the drainage chamber, patency can be assessed by lowering the entire drainage unit to below the head.

Notify CCTC resident AND Vascular Sugery if the unit fails to drain in the presence of an elevated pressure despite troubleshooting efforts



Zero the Transducer

  1. Select "ICP" as the monitor label.
  2. Open the transducer stopcock to air (taped to the mounting panel).
  3. Press "zero" on the bedside monitor.
  4. If the ICP is > 20, the scale will need to be increased.  


Zeroing and leveling the transducer ensures the bedside monitors reads the ICP accurately.

The ICP default scale is 20.


Connect to Patient

  1. Perfom hand hygiene and don non-sterile gloves.
  2. Connect the lumbar cathter to the drainage unit.


In accordance with the MoHLTC 4 moments of hand hygiene and LHSC infection control policies in an effort to reduce risk of transmission of microorganisms and secretions.


Patient Monitoring

Monitor lumbar ICP hourly.  Turn stopcock off to drainage for one minute each hour to obtain an accurate measurement.

Patient should have an arterial line for continous blood pressure monitoring.  Calculate a Spinal Cord Perfusion Pressure hourly.

Monitor spinal cord function hourly for initial 12 hours and if lumbar ICP is elevated.  Frequency may be decreased to Q2H per vascular surgery recommendations. Edema risk remains for at least 48-72 hours.

Monitor for acute change in bowel or bladder function (e.g., sudden diarrhea).  This may indicate acute spinal cord ischemia.

Notify CCTC physician AND Vascular Surgery immediately:

  • If blood pressure falls below target
  • If lumbar ICP remains above target despite drainage
  • If Spinal Cord Perfusion Pressure (MAP - lumbar ICP) falls below ordered target or previous trends
  • For any change in spinal or neurological assessment or changes in bowel function (indwelling Foley impedes bladder pressure monitoring.




ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM (2012) Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease:

Khan. (2012) Cerebrospinal fluid drainage for thoracic and thoracoabdominal aortic aneurysm surgery. Cochrane Vascular Group.

Ishikawa (2012). Acute subdural hematoma following thoracoabdominal aortic repair in a patient with Marfan syndrome: a rare complication of cerebrospinal fluid drainage.Ann Thorac Cardiovasc Surg. 18(5):488-90. Epub 2012 Mar 24.



Ullery. (2011). Risk factors, outcomes, and clinical manifestations of spinal cord ischemia following thoracic endovascular aortic repair. Journal of Vascular Surgery, September.

Fedorow (2010). Lumbar Cerebrospinal Fluid Drainage for Thoracoabdominal Aortic Surgery: Rationale and Practical Considerations for Management. Anesthesia & Analgesia. 111(1), 

Developed by:
Brenda Morgan

Initial Procedure: November 1988

Last Update: July 19, 2016 (BM)