CEREBRAL BLOOD FLOW MONITORING

CEREBRAL BLOOD FLOW MONITORING – Definition, Indications, Client and Environment Preparation, Special Considerations, Equipment, Setting up the Sensor Monitor, Procedure, Care of the Insertion Site, Removing the Sensor and After Care

DEFINITION

Cerebral blood flow (CBF) monitoring is estimated blood flow in neurologically compromised client’s by calculating cerebral perfusion pressure. A sensor placed on the cerebral cortex calculates CBF in the capillary bed by thermal diffusion. Thermistors within the sensor detect the temperature differential between two metallic plates – one heated one neutral

INDICATIONS

• Cerebral blood flow monitoring reveals the effects of interventions on it
• This monitoring technique yields important information about the effects of intervention on CBF, which are essential in conditions in which compromised blood flow may put the client at risk, such as ischemia and infarction
• CBF monitoring is indicated whenever CBF alternations are anticipated. It is used commonly in clients with subarachnoid hemorrhage, trauma associated with high intracranial pressure or vascular tumors

CLIENT AND ENVIRONMENT PREPARATION

• Instruct the client and family members fully about the procedures involved in CBF monitoring
• Obtain informed content
• Instruct the client that the insertion site will be covered with a dry, sterile dressing

SPECIAL CONSIDERATIONS

• CBF fluctuates with the brain’s metabolic demands, ranging from 60 to 90 ml/100 g/minute normally. however, the client’s neurological condition dictates the acceptable range
• For instance, in a patient in a coma, CBF may be half the normal value; in a client in a barbiturate-induced coma with burst suppression on the EEG, CBF may be as 10 ml/100 g/minute
• Vasospasm secondary to subarachnoid hemorrhage result in CBF below 40 ml/100 g/minute
• In an awake client, CBF above 90 ml/100 g/minute
• If you suspect poor contact between the sensor and the cerebral cortex, turn the client toward the side of the sensor or gently wiggle the catheter back and forth (using a sterile-gloved hand)
• If your client has low CBF but no neurological symptoms that indicate ischemia, suspect a fluid layer (a small hematoma) between the sensor and the cortex
• As with intracranial pressure monitoring, CBF monitoring may lead to infection. Administration prophylactic antibiotics as ordered and maintain in sterile dressing around the insertion site
• CSF leakage, another potential complication, may occur at the sensor insertion site. To prevent leakage, the surgeon usually places an additional suture at the site
• To reduce the risk of infection. Change the dressing at the insertion site daily

EQUIPMENT

Cerebral blood flow monitoring requires a special sensor that attaches to a computer data system or to a small analog monitoring that operates on a battery for client transport

• For care of site: sterile 4”/4” gauze pads, clean gloves, sterile gloves, povidone-iodine solution or ointment
• For removing sensor: sterile suture removal tray, 1” adhesive tape, sterile 4”/4” gauze pads, clean gloves, sterile gloves and suture material

SETTING UP THE SENSOR MONITOR

• First assemble the following equipment at the bed side; a monitor and a sensor cable with an attached sensor. Attach the distal end of the sensor cable (from the client’s head) to the SENSOR CONNECT port on the monitor. When the sensor cable is securely in place, press on ON  key to activate the monitor
• Calibrate the system by pressing the CAL key. You should see the red light appear on the CAL button. Ideally, you will begin by calibrating the sensor to 00.0 by pressing the directional arrows. Readouts of plus or minus 0.1 are also acceptable

PROCEDURE

• The surgeon typically inserts the sensor in the operating room during or following a craniotomy (occasionally, he may insert I through a burr hole)
• He implants the sensor far from major blood vessels and verifies that the metallic plates have good contact with the brain surface
• Press the RUN key to display the CBF reading. Observe the monitor’s digital display and document the baseline value
• Record the CBF hourly. Be sure to watch for trends and correlate values with the client’s status. Be aware that stimulation or activity may cause a 10% increase in CBF, if you detect a 20% increase or decrease. Suspect poor contact between the sensor and the cerebral cortex

CARE OF THE INSERTION SITE

• Wash hands, put on clean gloves and remove the dressing from the sensor insertion site
• Observe the site for cerebrospinal fluid leakage, a potential complication. Then remove and discard your gloves
• Put on sterile gloves. Using aseptic technique, clean in insertion site with a gauze pad soaked in povidone-iodine solution
• Clean the site, starting at the center and working outward in a circular pattern
• Using a new gauze pad soaked with povidone-iodine solution, clean the exposed part of the sensor from the insertion site to the sensor
• Apply povidone-iodine ointment to the insertion site if your faculty’s policy permits
• Place sterile 4”/4” gauze over the insertion site to completely cover it, tape all edges securely to create an occlusive dressing

REMOVING THE SENSOR

• In most cases, the CBF sensor remains in place for about 3 days when used postoperative monitoring
• Explain the procedure to the client; then wash hands. Put on clean gloves, remove the dressing and dispose the gloving and dressing properly
• Open the suture removal tray and the package of suture material. The surgeon removes the anchoring sutures and then gently removes the sensor from the insertion site
• After the surgeon closes the wound with stitches, put on sterile gloves, apply a folded gauze pad to the site and tape it in place
• Observe the condition of the site, including any leakage

AFTER CARE

• Observe the neurological vital signs at regular intervals
• Check the insertion site at regular intervals
• Documentation