Intracranial Pressure Monitoring

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W20 Intracranial Pressure Monitoring

Fabio S. Taccone, Sarice L. Bassin, Thomas P. Bleck, Jean-Louis Vincent

Anatomy

For brain monitoring, the entry point is located in the superiorly directed midpupillary line, 3 cm lateral to the sagittal suture and 2 cm anterior to the coronal suture on the right (frontal approach). This is the most commonly chosen site because it sits anterior to the motor strip, is lateral to both the superior sagittal sinus and the large bridging veins, and is on the nondominant hemisphere in most patients. If using a posterior approach, the entry point is 6 cm from the inion and 3 cm lateral to the midline. For lumbar monitoring, the L3-4 space is preferred.

There are four main ways to monitor ICP:

1 Using an external flexible catheter inserted into the lateral cerebral ventricles (ventriculostomy)—the gold standard method

2 Using a catheter (fluid-coupled) or fiberoptic transducer (fluid-uncoupled) placed into the brain parenchyma (intraparenchymal catheter)

3 Using a screw or bolt placed through the skull into the subarachnoid space

4 Using a sensor positioned in the epidural/subdural space beneath the skull.

A lumbar drain can also be used to measure ICP and control CSF outflow if zeroed at the level of the third ventricle.

Procedure

• Ventriculostomy:

• Place the patient in supine position with head of the bed elevated to approximately 20 degrees.

• Shave areas (frontal or posterior) bilaterally.

• Prepare with chlorhexidine-alcohol solution, and cover with a sterile drape.

• Inject lidocaine solution (1%) into the skin and subcutaneous tissue.

• Make a 1-cm incision with the scalpel and extend down to the bone. Hold the twist drill perpendicular to the skull to make a burr hole, avoiding the brain parenchyma.

• Once the burr hole is irrigated, insert a spinal needle through the dura to verify that the incision is large enough to accommodate the catheter.

• Advance the ventricular catheter through the burr hole perpendicular to the brain parenchyma, toward the inner canthus of the ipsilateral eye. Insert the catheter to a depth of approximately 6 cm to enter the frontal horn of the lateral ventricle. If cerebrospinal fluid (CSF) is encountered before a depth of 6 cm, withdraw the stylet and advance the catheter the remaining distance. If CSF flow is not obtained at 6 cm, additional attempts should be made with the catheter tip directed more medially (i.e., toward the bridge of the nose or the inner canthus of the contralateral eye).

• Tunnel the external end of the catheter under the scalp to exit through a separate incision approximately 5 to 6 cm from the entry point. Connect the distal end of the catheter to a pressure transducer and/or drainage system. Close the incision wound with sutures, and secure the catheter to the scalp with nylon suture. Apply a sterile nonocclusive dressing to minimize the risk of infection.

• Zero the pressure transducer (fluid-coupled) at the level of the external auditory meatus.

• Intraparenchymal:

• Placement and tunneling of the device is similar to that of a ventriculostomy, but the depth of insertion depends on the compartment being monitored (subdural space, parenchyma, or ventricular system).

• Subarachnoid screw or bolt:

• The device is inserted using the same location and technique described earlier for burr hole placement. Once the burr hole is drilled, the dura and arachnoid are opened, and the threaded bolt is placed into the skull abutting the dura. Continuous fluid coupling between the subarachnoid space and an external pressure transducer is recorded through rigid tubing attached to the top of the bolt.

• Epidural/subdural sensor:

• This is inserted via the burr hole into the space between the skull and the epidural lining.

• Lumbar drain:

• Place the patient in lateral decubitus.

• Use the same preparation as for brain monitoring.

• Insert a 14-guage needle with 10 to 15 degrees of angulation in the cephalic direction, and once the lumber cistern is entered, rotate the needle 90 degrees, remove the obturator from the needle, and measure an opening pressure.

• Insert the catheter with a guidewire until the 15 cm mark on the catheter. Remove the needle while keeping the catheter in the same position. Remove the guidewire from the lumbar drain catheter, and connect the drain to the CSF collecting system.

After Procedure

Postprocedure Care

• If fluid-coupled systems are used, the pressure transducer must be adjusted to the head position to avoid errors in measurement.

• Check for air bubbles, blood clots, or other material occluding the tubing.

• Inspect the drain insertion site to ensure no leakage of CSF around the exit site.

• Sample CSF daily to detect infection early.

• Normal ICP values are 0 to 10 mm Hg (under resting conditions).

• Intracranial hypertension is defined as sustained elevation of ICP above 20 to 25 mm Hg for more than 5 minutes.

Outcomes and Evidence

• Monitoring ICP is mandatory in critically ill patients with intracranial hypertension to evaluate cerebral perfusion pressure and drain excess CSF.

• Ventriculostomy is the gold standard to measure ICP but must be continuously zeroed. Fiberoptic monitors are zeroed prior to insertion and not affected by patient position or bed height. ICP can also be measured via subarachnoid, epidural/subdural, or lumbar drain.

• The risk of a hemorrhagic complication from placement of an ICP monitor ranges from approximately 0.5% to 10%. The risk of hemorrhage increases dramatically when coagulation abnormalities are present.

• The rate of infection associated with ICP monitors correlates with duration of placement, presence of a CSF leak, frequency of CSF sampling, presence of intraventricular hemorrhage, and concurrent systemic infection. The utility of prophylactic antibiotics and daily surveillance of CSF cultures is highly controversial.

Suggested Reading

Zanier ER, Ortolano F, Ghisoni L, et al. Intracranial pressure monitoring in intensive care: clinical advantages of a computerized system over manual recording. Crit Care. 2007;11:R7.

Soldatos T, Chatzimichail K, Papathanasiou M, et al. Optic nerve sonography: a new window for the non-invasive evaluation of intracranial pressure in brain injury. Emerg Med J. 2009;26:630-634.

Smith M. Monitoring intracranial pressure in traumatic brain injury. Anesth Analg. 2008;106:240-246.

Bekar A, Doğan S, Abaş F, et al. Risk factors and complications of intracranial pressure monitoring with a fiberoptic device. J Clin Neurosci. 2009;16:236-240.

Hoekema D, Schmidt RH, Ross I. Lumbar drainage for subarachnoid hemorrhage: technical considerations and safety analysis. Neurocrit Care. 2007;7:3-9.

Abadal-Centellas JM, Llompart-Pou JA, Homar-Ramirez J, et al. Neurologic outcome of posttraumatic refractory intracranial hypertension treated with external lumbar drainage. J Trauma. 2007;62:282-286.

Cremer OL. Does ICP monitoring make a difference in neurocritical care? Eur J Anesthesiol. 2008;25:87-93.

Beer R, Lackner P, Pfausler B, et al. Nosocomial ventriculitis and meningitis in neurocritical care patients. J Neurol. 2008;255:1617-1624.

Lavinio A, Menon DK. Intracranial pressure: why we monitor it, how to monitor it, what to do with the number and what’s the future? Curr Opin Anaesthesiol. 2011. Epub ahead of print

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W20 Intracranial Pressure Monitoring

Fabio S. Taccone, Sarice L. Bassin, Thomas P. Bleck, Jean-Louis Vincent

Anatomy

For brain monitoring, the entry point is located in the superiorly directed midpupillary line, 3 cm lateral to the sagittal suture and 2 cm anterior to the coronal suture on the right (frontal approach). This is the most commonly chosen site because it sits anterior to the motor strip, is lateral to both the superior sagittal sinus and the large bridging veins, and is on the nondominant hemisphere in most patients. If using a posterior approach, the entry point is 6 cm from the inion and 3 cm lateral to the midline. For lumbar monitoring, the L3-4 space is preferred.

There are four main ways to monitor ICP:

1 Using an external flexible catheter inserted into the lateral cerebral ventricles (ventriculostomy)—the gold standard method

2 Using a catheter (fluid-coupled) or fiberoptic transducer (fluid-uncoupled) placed into the brain parenchyma (intraparenchymal catheter)

3 Using a screw or bolt placed through the skull into the subarachnoid space

4 Using a sensor positioned in the epidural/subdural space beneath the skull.

A lumbar drain can also be used to measure ICP and control CSF outflow if zeroed at the level of the third ventricle.

Procedure

• Ventriculostomy:

• Place the patient in supine position with head of the bed elevated to approximately 20 degrees.

• Shave areas (frontal or posterior) bilaterally.

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