Hospital for Sick Children, Toronto, Canada

A Protocol for Cerebral Function Monitoring in the NICU

Dr. Patrick McNamara, Matthew Keyzers RRT

Reprinted with permission of Hospital for Sick Children, Toronto, Canada. June 2006

The cerebral function monitor provides information on global cerebral activity. An abnormal CFM trace in the first six hours of life, after an asphyxial insult, is predictive of abnormalities on acute neurological testing and long term neurodevelopmental outcome. The CFM also provides information on duration, in-tensity and frequency of neonatal seizures that may be helpful in diagnosis and treatment.

1.0 Purpose:

To outline the clinical indications, setup process, ap-plication, and analysis a cerebral function monitor can provide to patients of a NICU.

2.0 Description:

An amplitude-integrated EEG, or Cerebral Function Monitor (CFM), is a device used to measure background electrocortical activity in the brain. Using a single lead, consisting of three wires placed over the biparietal or frontal region; it filters, rectifies and compresses a sig-nal to indicate the generalized level of electrical activity occurring across the entire brain. The signal is displayed on an x-y axis, using a very slow chart speed represent-ing a generalized view of brain activity.

CFM technology was initially developed in the 1960s for adults suffering from neurological depression or injury or undergoing surgery. However, due to techni-cal constraints and the need for constant recalibration, the technology did not gain wide acceptance. The

A Protocol forCerebral Function Monitoring in the NICU

Dr. Patrick McNamara, Matthew Keyzers RRT

technology was reintroduced in the mid 1980s by neo-natologists. Research showed it could be a sensitive tool for predicting severity of hypoxic-ischemic en-cephalopathy, if applied in the first 6–12 hours following perinatal asphyxia. The CFM has also demonstrated itself as a valuable detection tool for neonates experi-encing clinical or subclinical seizures. As an analogy, a CFM provides quick, general information of a patient’s brain activity like oximetry provides information on a patient’s blood oxygenation; or an ECG provides infor-mation on a patient’s cardiac status.

3.0 Indications:

• Hypoxic – Ischemic Encephalopathy

• Seizures or clinical scenario mimicking seizure disorders (e.g., apnea, hypertension, tachycardia)

• Significant neurological disorders (e.g., con-genital brain malformations, vascular lesions)

• Post cardiac arrest

• Inborn error of metabolism (e.g., urea cycle disorders, hypoglycaemia, hypocalcaemia)

• Neonatal abstinence syndrome (e.g., alcohol/opiate withdrawal)

4.0 Pitfalls:

• Requires proper lead stabilization to reduce or eliminate artefact caused by high frequency oscillation.

Guideline Special DIrection

1. Obtain Doctor’s order to initiate monitoring. Diagnostic tests require a doctor’s order.

2. Connect the cable to the cable input on the front of the

CFM.

3. Plug CFM into A/C outlet and turn power switch to ON

in rear of device.

4. Obtain CFM Hydrogel Electrodes, EEG abrasive skin

preparing gel (NUPREP), 2×2 gauzes.

• CFM hydrogel leads: room supply carts

• 2×2 gauze: Room supply carts

• NUPREP: CFM drawer in RT room

5. Establish where the three leads will be placed on

the head.

• Black wire lead (ground): placed in centre of forehead

• Red wire lead (left): placed 3.75 cm left of midline as

close to the coronal plane as possible.

• Yellow wire lead (right): placed 3.75 cm right of midline

as close to the coronal plane as possible.

*** A high forehead location is acceptable but parietal po-

sitioning will get a more accurate, global representation

of brain activity.

6. Using wet 2x2 gauze, scrub 3 areas to remove some of

natural skin oils.

*** USING ALCOHOL SWABS WILL LEAVE A THIN FILM ON

SKIN AND IMPAIR IMPEDANCE OF THE LEADS. JUST

USE STERILE WATER.

7. Apply a small amount of NUPREP to a 2×2 gauze and

scrub each lead area with circular motion for 30

seconds.

8. Wipe excess NUPREP off lead sites with dry 2x2

gauze.

9. Securely fasten the three hydrogel leads to prepared

areas.

Ensure there are no air bubbles and the leads are not lifting

off skin.

10. Connect lead wires to CFM cable module. • Red lead wire to Red cable module input.

• Yellow lead wire to Yellow cable module input.

• Black lead wire to Black cable module input.

• Consider shaving the area if the lead contact is poor or

the impedance is high ( > 10 ohms).

11. Press RECORD button on CFM screen. Small cursor arrow on right will begin to move up and

down on CFM tracing indicating recording.

12. Press PATIENT button on CFM screen and fill in the

name, birth date and ID number of the patient.

Please enter patient data in order that the CFM tracing can

be easily recalled from the device’s hard drive if monitoring

is later discontinued.

5.0 Setup Guidlines:

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6.0 Application Guidelines

The main screen is divided into 2 main graphing strips. The top strip is the cerebral function graph that mea-sures electrical brain activity [(µV), semi-logarithmic y-axis] versus time [(hr:min:sec), x-axis]. The bottom strip measures impedance of the leads and evaluates the connection of the leads to the patient’s scalp. The impedance strip should show a relatively flat line that is less than < 20 µW to ensure accuracy of the CFM trac-ing. An increasing level of impedance means the leads are lifting off the scalp and must be reapplied. If the lead lifts off enough, an alarm condition will sound.

Due to the slow charting speed of the CFM, it takes approximately 20 minutes before the clinician can pre-liminarily analyze the strip. Therefore, seizure treatment should never be delayed if clinical symptoms are ob-served. Doctors should make a habit of reviewing the CFM every 2–3 hours.

Markers should be labelled on the CFM tracing if the RN observes any clinical symptoms of seizures or ad-ministers any sedation or anticonvulsant therapy. If repositioning or stimulating the patient causes distur-bances in the tracing, these events should be labelled as well (x rays, etc.). Markers are placed by pressing the

MARKER button, tapping the CFM strip at the appropri-ate time, and then typing or selecting the appropriate marker from the window that pops up.

The CFM functions nicely as a long-term monitor and can be left in place for several days of constant record-ing. Within 12 hours of starting a CFM trace, a patient should be evaluated using a standard EEG, which may detect focal seizures or localize lesions that cannot al-ways be detected with CFM alone.

If recording is stopped on a patient at any time and is to be restarted, the operator should reapply leads (if not already on), press TOOLS, select the patient’s name from the list and press ACCEPT to display file. RESUME will continue the recording.

7.0 Steps to Wave Analysis

Observe the impedance graph and ensure the line is relatively flat and preferably below 10 kW. This indicates an accurate CFM tracing.

NorMAl TrACING

Examine the CFM strip as a whole.

• Is it a gentle wave? YES

• Do the lower and upper margins seem to flow in parallel? YES

• Is the lower margin above 5 µV? YES

• Is the upper margin above 10 µV? YES

• Is their regular widening & narrowing of the trace, within the above margins (Sleep Wake Cycling)? YES

This is classified as a normal trace and in most cases is a good prognostic sign. Early return of sleep wake cycling (SWS) after an asphyxial insult is also a good prognostic sign.

Normal trace; Upper margin is > 10 µV & lower margin is > 5 µV. The widening and narrowing of the trace im-plies periods of wakening and sleep i.e. SWS).

Hospital for Sick Children, Toronto, Canada. June, 2006 2

MoDerATely AbNorMAl TrACING

• Is the lower margin below 5 µV? YES

Moderately abnormal function present.

Keep in mind that anti-convulsant therapy may shift the wave downward.

Moderately abnormal trace; Upper margin is > 10 µV & lower margin is < 5 µV throughout the trace. There is no SWS.

SeVerely AbNorMAl TrACING

• Is the upper margin below 10 µV? YES

• Does the thickness of the wave appear thinner? YES

• Has the wave appeared to flatten out? YES

Severely abnormal function present. This may corre-spond with burst suppression or continuous low voltage on a regular EEG.

Severely abnormal trace; Upper margin is < 10 µV & lower margin is < 5 µV throughout the trace. There is evidence of SWS. Periodic bursts of electrical activity are seen.

SeIzUreS

• Is there a rising and narrowing pattern in the CFM tracing? YES

• In the gaps of the rising and narrowing (lower margin becomes suddenly raised for several minutes), does the eeG tracing show a distinct repetitive pattern? YES

Seizures are present.

Moderately abnormal trace with multiple seizures; Upper margin is > 10 µV & lower margin is < 5 µV throughout the trace. There is no evidence of SWS. Frequent and prolonged periods of elevation in both the lower and upper margins are seen that coincide with a repetitive rhythmic pattern on the eeG. This is characteristic of seizure activity.

3 Hospital for Sick Children, Toronto, Canada. June, 2006

Nurse

• Observe for clinical signs of seizures

• Track times of when procedures are done and when anti-convulsant and sedative therapy is given.

• Communicate problems or questions to the RT

• Informs RT of alarms or major trace changes

Physician or Nurse Practioner

• Orders when to commence and discontinue CFM using prescription sheets and CFM requisition

• Interprets the tracing

• Medical management of abnormalities detected on CFM trace

• Informs ancillary staff and other physicians

• Documents abnormal traces in patient chart with subsequent medical intervention

For further reading and training (includes many test samples):

http://www.azzopardi.freeserve.co.uk/CFM

Hospital for Sick Children, Toronto, Canada. June, 2006 4

7.1 Analysis and Prematurity

aEEG is feasible for monitoring cerebral activity in preterm infants and normative values have been sug-gested. SWS can be clearly identified on the trace from around 30 week’s gestation although a cyclical pattern emerges in some babies at 25-26 weeks gestation. A scoring system has been suggested by Burdjalov et al based on continuity, presence of cycling, amplitude of the lower border and bandwith (see bibliography).

This scoring system has not yet been tested in terms of its ability to recognise pathological states and is some-what subjective; however it may be useful as a guide for interpretation. This scoring system is recommended when aEEG is applied to premature infants to facilitate trace interpretation. Extremely low voltage patterns or burst suppression should be easily recognisable. There are no definitive reports on seizure patterns in prema-ture infants. Pathological patterns should be confirmed by more formal EEG evaluation.

8.0 responsibilities of Health Care Team Members During Cerebral Function Monitoring

All health care professionals (i.e. physicians, nurses, RT’s, nurse practitioners) involved in the care of critical-ly ill newborn infants will participate in CFM monitoring. Their roles must be clearly defined to ensure this tech-nology is used correctly when indicated and analyzed in a timely fashion thus ensuring optimal care is provided. Early identification of disturbances in global cerebral brain wave activity may lead to earlier therapeutic in-terventions, ultimately improving patient outcomes. Each unit must designate an individual (s) who will take responsibility for ensuring all staff understand the im-portance of this technology and that the designated responsible health professionals are educated in equip-ment troubleshooting and trace interpretation. This will ensure optimal usage of the technology.

respiratory Therapist or Nurse

• Sets up the equipment

• Operates the equipment

• Troubleshooting of technical difficulties

• Helps facilitate interpretation

reference list (1) al Naqeeb N, Edwards AD, Cowan FM, Azzopardi D. Assessment

of neonatal encephalopathy by amplitude-integrated electroencephalography. Pediatrics 1999; 103(6 Pt 1):1263-1271.

(2) Burdjalov VF, Baumgart S, Spitzer, AR. Cerebral function monitoring: a new scoring system for the evaluation of brain maturation in neonates. Pediatrics. 2003;112(4):855-861.

(3) Gluckman PD, Wyatt JS, Azzopardi D, Ballard R, Edwards AD, Ferriero DM et al. Selective head cooling with mild systemic hypothermia after neonatal encephalopathy: multicentre randomised trial. Lancet 2005; 365(9460):663-670.

(4) Hellstrom-Westas L, Rosen I, Svenningsen NW. Predictive value of early continuous amplitude integrated EEG recordings on outcome after severe birth asphyxia in full term infants. Arch Dis Child Fetal Neonatal Ed 1995; 72(1):F34-F38.

(5) Hellstrom-Westas L, Rosen I. Electroencephalography and brain damage in preterm infants. Early Hum Dev 2005; 81(3):255-261.

(6) ter Horst HJ, Brouwer OF, Bos AF. Burst suppression on amplitude-integrated electroencephalogram may be induced by midazolam: a report on three cases. Acta Paediatr 2004; 93(4):559-563.

(7) ter Horst HJ, Sommer C, Bergman KA, Fock JM, van Weerden TW, Bos AF. Prognostic significance of amplitude-integrated EEG during the first 72 hours after birth in severely asphyxiated neonates. Pediatr Res 2004; 55(6):1026-1033.

(8) Toet MC, Hellstrom-Westas L, Groenendaal F, Eken P, de Vries LS. Amplitude integrated EEG 3 and 6 hours after birth in full term neonates with hypoxic-ischaemic encephalopathy. Arch Dis Child Fetal Neonatal Ed 1999; 81(1):F19-F23.

(9) van Rooij LG, Toet MC, Osredkar D, van Huffelen AC, Groenendaal F, de Vries LS. Recovery of amplitude integrated electroencephalographic background patterns within 24 hours of perinatal asphyxia. Arch Dis Child Fetal Neonatal Ed 2005; 90(3):F245-F251.

Issuing Department: Neonatology Category: Neurological Diagnostics

Issuing Authority: Sub-Category: Cerebral Function Monitor

Section Name: Publication Status: Final Draft Content

reviewer: Dr. Patrick McNamara Creation Date: December, 2004

Additional editors: last Modified: August 23, 2006

Written by: Matthew Keyzers, RRT& Dr. Patrick McNamara

Hospital For Sick Kids, Toronto

reprinted with permission by

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