INTRACRANIAL PRESSURE MONITORING

INTRACRANIAL PRESSURE MONITORING – Indications, Classification, General Instructions, Client and Environment Preparation, Equipment, Procedure, Interpreting ICP Waveforms and After Care

DEFINITION

Intracranial pressure monitoring measures the presence exerted by the brain, blood and cerebrospinal fluid against the inside of the skull

INDICATIONS

• Head trauma with bleeding or edema
• Over production or insufficient absorption of CSF
• Cerebral hemorrhage and space occupying lesion

CLASSIFICATION

• Intraventricular catheter monitoring:

In this procedure, which monitors ICP directly, the doctor inserts a small polyethylene or silicone rubber catheter into the lateral ventricle through a burr hole

Although, this method measures ICP most accurately, it carries the greatest risk of infection. This is the only type of ICP monitoring that allows evaluation of brain compliance and drainage of significant amounts of cerebrospinal fluid

Contraindications usually include stenotic cerebral ventricles, cerebral aneurysms in the path of catheter placement and suspected vascular lesions

• Subarachnoid bolt monitoring:

This procedure involves insertion of a special bolt into the subarachnoid space through a twist-drill burr hole that is positioned in the front of the skull behind the hairline

Placing the bolt is easier than placing an intra-ventricular catheter, especially if a computed tomography scan reveals the cerebrum has shifted or the ventricles have collapsed

This type of ICP monitoring also carries less risk of infection and parenchymal damage because the bolt does not penetrate the cerebrum

• Epidural or subdural sensor monitoring:

ICP can also be monitored the epidural or subdural space. For epidural monitoring, sensor is inserted into the epidural space through a burr hole. This system’s main drawback is questionable accuracy because ICP is not being measured directly from a CSF-filled space

For subdural monitoring, a fiber-optic transducer tip is placed on brain tissue under the dura mater. The main drawback to this method is its inability to drain CSF

• Intra-parenchymal monitoring:

In this procedure, the doctor inserts a catheter through a small subarachnoid bolt and after puncturing the dura, advances the catheter a few centimeters into the brain’s white matter. There is no need to balance or calibrate the equipment after insertion

Although this method does not provide directly access to CSF, measurements are accurate because brain tissue pressure correlate well with ventricular pressure

Intraparenchymal monitoring may be used to obtain ICP measurements in clients with compressed or dislocated ventricles

GENERAL INSTRUCTIONS

• ICP monitoring can detect elevated ICP early, before clinical danger signs develop, prompt intervention can help avert or diminish neurological damage caused by cerebral hypoxia and shifts of brain mass
• The four basic ICP monitoring systems are intra-ventricular catheter, subarachnoid bolt, epidural sensor and intraparenchymal pressure monitoring
• Regardless of which system is used, the procedure is always performed by a neurosurgeon in the operating room, emergency department or critical care unit
• Insertion of an ICP monitoring device requires sterile technique to reduce the risk of central nervous system (CNS) infection
• Setting up equipment for the monitoring system also requires strict asepsis

CLIENT AND ENVIRONMENT PREPARATION

• Explain the entire procedure to the client or his family
• Obtain informed consent
• Determine whether the client is allergic to iodine preparations
• Monitoring units and setup protocols are varied and complex and differ among health care facilities

EQUIPMENT

• Monitoring unit and transducers as ordered
• 16 to 20 sterile 4”/4” gauze pads
• Linen-saver pads
• Shave preparation tray or hair scissors
• Sterile drapes
• Povidone – iodine solution
• Sterile gown
• Surgical mask
• Two pairs of sterile gloves
• Head dressing supplies (two rolls of 4” elastic gauze dressing, one roll of 4” roller gauze, adhesive tape)
• Optional: suction apparatus, yardstick

PROCEDURE

• Provide privacy if the procedure is being done in an open emergency department or intensive care unit
• Obtain baseline routine and neurological vital signs to aid in prompt detection of decompensation during the procedure
• Place the client in the supine position, and elevate the head of the bed 30 degree (or as ordered)
• Place linen-saver pads under the patient’s head. Shave or clip his hair at the insertion site, as indicated by the doctor, to decrease the risk of infection
• Carefully fold and remove the device, hold the client’s head in your hands or attach a long strip of 4” roller gauze to one side rail
• Observe for cardiac arrhythmias and abnormal respiratory pattern
• After insertion, apply povidone-iodine solution and a sterile dressing to the site. If not done by the doctor, connect the catheter to the appropriate monitoring device, depending on the system used
• If the doctor has setup a drainage system, attach the drip chamber to the headboard or bedside IV pole as ordered

INTERPRETING ICP WAVEFORMS

Normal Wave

A normal ICP waveform typically shows a steep upward systolic slope followed by a downward diastolic slope with a dicrotic notch. In most cases, this waveform occurs continuously and indicates an ICP between 0 and 15 mm Hg normal pressure

A Wave

• The most clinically significant ICP waveform are A waves, which may reach elevations  of 50-100 mm Hg, persists of 5-20 minutes, then drop sharply-signaling exhaustion of the brain’s compliance mechanism
• A waves may come and go, spiking from temporary rises in thoracic pressure or from any condition that increases ICP beyond the brain’s compliance limits
• Activities such as sustained coughing or straining during defecation can cause temporary elevations in thoracic pressure

B Waves

• B waves appear sharp and rhythmic with a saw tooth pattern, occur every one and half to 2 minutes and may reach elevations of 50 mm Hg
• The clinical significance of B waves is not clear but the wave’s correlates with respiratory changes and may occur more frequently with decreasing compensation. Because B waves sometimes precede A waves, notify the doctor if B waves occur frequently

C Waves

• B wave, C wave are rapid and rhythmic, but they are not as sharp
• Clinically insignificant, they may fluctuate with reparations or systemic blood pressure changes

AFTER CARE

• Positioning the drip chamber too high may raise ICP; positioning it too low may cause excessive CSF drainage
• Inspect the insertion site at least every 24 hours or redness, swelling and drainage
• Clean the site, reapply povidone-iodine solution and apply a fresh sterile dressing
• Assess the client’s clinical status and take routine and neurological vital signs every hourly or as ordered
• Make sure you have obtained orders for waveforms and pressure parameters from the doctor
• Calculate cerebral perfusion pressure (CPP) hourly; use the equation CPP = MAP – ICP (MAP refers to mean arterial pressure)