Cardiac Monitoring
Because it allows continuous observation of the heart’s electrical activity, cardiac monitoring is used in patients with conduction disturbances or in those at risk for life-threatening arrhythmias.
Like other forms of electrocardiography, cardiac monitoring uses electrodes placed on the patient’s chest to transmit electrical signals that are converted into a tracing of cardiac rhythm on an oscilloscope.
Two types of monitoring may be performed: hardwire or telemetry. With hardwire monitoring, the patient is connected to a monitor at bedside. The rhythm display appears at bedside, but it may also be transmitted to a console at a remote location. Telemetry uses a small transmitter connected to the patient to send electrical signals to another location, where they’re displayed on a monitor screen. Battery powered and portable, telemetry frees the patient from cumbersome wires and cables and lets him be comfortably mobile. Telemetry is especially useful for monitoring arrhythmias that occur during sleep, rest, exercise, or stressful situations.
Regardless of the type, cardiac monitors can display the patient’s heart rate and rhythm, produce a printed record of cardiac rhythm, and sound an alarm if the patient’s heart rate rises above or falls below specified limits. Monitors also recognize and count abnormal heartbeats as well as changes. For example, ST-segment monitoring helps detect myocardial ischemia, electrolyte imbalance, coronary artery spasm, and hypoxic events. The ST segment represents early ventricular repolarization, and any changes in this waveform component reflect alterations in myocardial oxygenation.1 Any monitoring lead that views an ischemic heart region will reveal ST-segment changes. The monitor’s software establishes a template of the patient’s normal QRST pattern from the selected leads; then the monitor displays ST-segment changes. Some monitors display such changes continuously; others, only on command. (See Lead selection.)
One application of bedside cardiac monitoring is a reduced-lead continuous 12-lead electrocardiogram (ECG) system (EASI system). This system uses an advanced algorithm and only five electrodes placed on the torso to derive a 12-lead ECG. The system allows all 12 leads to be simultaneously displayed and recorded. (See Understanding the EASI system.)
Equipment
Cardiac monitor ▪ lead wires ▪ patient cable ▪ disposable pregelled electrodes (number of electrodes varies from three to five, depending on patient’s needs) ▪ washcloth, soap, and water, or alcohol pads ▪ 4″ × 4″ gauze pads ▪ gloves ▪ Optional: clippers.
For Telemetry
Transmitter ▪ transmitter pouch ▪ telemetry battery pack, leads, and electrodes ▪ gloves.
Preparation of Equipment
Plug the cardiac monitor into an electrical outlet and turn it on to warm up the unit while you prepare the equipment and the patient. Insert the cable into the appropriate socket in the monitor. Connect the leadwires to the cable. In some systems, the leadwires are permanently secured to the cable. Each leadwire should indicate the location for attachment to the patient: right arm (RA), left arm (LA), right leg (RL), left leg (LL), and chest (C). Leadwires may also be color-coded for placement: white (RA), black (LA), green (RL), red (LL), and brown (chest). This designation should appear on the leadwire, if it’s
permanently connected, or at the connection of the leadwires and cable to the patient. Then connect an electrode to each of the leadwires, carefully checking that each leadwire is in its correct outlet.
permanently connected, or at the connection of the leadwires and cable to the patient. Then connect an electrode to each of the leadwires, carefully checking that each leadwire is in its correct outlet.
For telemetry monitoring, insert a new battery into the transmitter. Be sure to match the poles on the battery with the polar markings on the transmitter case.2 Test the battery’s charge and test the unit by pressing the button at the top of the unit; this ensures that the battery is operational. If the leadwires aren’t permanently affixed to the telemetry unit, attach them securely. If they must be attached individually, connect each one to the correct outlet.
Implementation
Confirm the patient’s identity using at least two patient identifiers according to your facility’s policy.6
Provide privacy and explain the procedure to the patient.
Ask the patient to expose his chest.2
Determine electrode positions on the patient’s chest based on the system and lead you’re using. (See Positioning monitoring leads, page 110.)
If necessary, clip the hair in an area about 4″ (10 cm) in diameter around each electrode site to ensure good skin contact with the electrodes.1,2
Clean the electrode area with a cleaning wipe or soap and water and dry it completely to provide for adequate transmission of electrical impulses.1,2,7
Clean the intended sites with an alcohol pad to remove oils from skin and improve impulse transmission.2
Gently abrade the skin at the intended sites to remove dead skin cells and to promote better contact with living cells.2 (Some electrodes have a small, rough patch for abrading the skin; otherwise, use a dry washcloth or a dry gauze pad.)
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