Transcutaneous pacing (TCP), also calledexternal pacing, is a temporary means of pacing a patient'sheart during a medical emergency. It should not be confused withdefibrillation (used in more serious cases, in ventricular fibrillation and other shockable rhythms) using a manual or automatic defibrillator, though some newer defibrillators can do both, and pads and an electrical stimulus to the heart are used in transcutaneous pacing and defibrillation. Transcutaneous pacing is accomplished by delivering pulses of electric current through the patient's chest, which stimulates theheart to contract.[1]
The most commonindication for transcutaneous pacing is an abnormally slowheart rate. By convention, a heart rate of fewer than 60 beats per minute in the adult patient is calledbradycardia.[2] Not all instances of bradycardia require medical treatment. Normal heart rate varies substantially between individuals, and many athletes in particular have a relatively slow resting heart rate.[3] In addition, the heart rate is known to naturally slow with age. It is only when bradycardia presents with signs and symptoms ofshock that it requiresemergency treatment with transcutaneous pacing.
Some common causes ofhemodynamically significant bradycardia includemyocardial infarction,sinus node dysfunction andcomplete heart block.[citation needed]
Transcutaneous pacing is no longer indicated for the treatment ofasystole (cardiac arrest associated with a "flat line" on theECG), with the possible exception of witnessed asystole (as in the case ofbifascicular block that progresses tocomplete heart block without anescape rhythm).[5]
During transcutaneous pacing, pads are placed on the patient's chest, either in the anterior/lateral position or the anterior/posterior position. The anterior/posterior position is preferred as it minimizes transthoracicelectrical impedance by "sandwiching" the heart between the two pads[citation needed]. The pads are then attached to a monitor/defibrillator, a heart rate is selected, and current (measured in milliamps) is increased until electrical capture (characterized by a wideQRS complex with tall, broad T wave on theECG) is obtained, with a corresponding pulse. Pacing artifact on the ECG and severe muscle twitching may make this determination difficult. It is therefore advisable to use another instrument (e.g. SpO2 monitor or bedside doppler) to confirm mechanical capture.
Transcutaneous pacing may be uncomfortable for the patient.[citation needed]Sedation should therefore be considered. Before pacing the patient in a prehospital setting sedation is recommended by administering an analgesic or an anxiolytic.[by whom?] Prolonged transcutaneous pacing may cause burns on the skin. According to the Zoll M Series Operator's Guide," Continuous pacing of neonates can cause skin burns. If it is necessary to pace for more than 30 minutes, periodic inspection of the underlying skin is strongly advised." It is meant to stabilize the patient until a more permanent means of pacing is achieved.
Other forms of cardiac pacing aretransvenous pacing, epicardial pacing,[6] and permanent pacing with animplantable pacemaker.
In addition to synchronized transcutaneous pacing offered by newer cardiac monitor/defibrillators, there is also an option for asynchronous pacing. Sometimes in the prehospital setting a situation may arise where ECG electrodes are not available or something interferes with their adhesion to the patient's skin. In these rare situations where the patient must be paced and there are no other alternatives, asynchronous pacing may be used. Again, this setting should only be used as a last resort due to possible adverse cardiac effects it could cause.
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