الفهرس 
PHYSIOLOGICAL CONSIDERATIONSOnly 14 pages are availabe for public view
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Abstract
This essay gives a concise knowledge about pacemakers and the present concept of anesthetic management of the pacemaker patient undergoing a surgical operation using a diathermy.
Artificial pacing is indicated for treatment of persistent bradycardia of any origin if it compromises hemodynamics.
The two major indications for permanent pacing are failure of impulse formation and failure of cardiac conduction.
Hence, the first chapter considers the conductive and excitatory system of the cardiac impulse beginning with the sinus node which under normal condition functions as the normal pacemaker of the heart with reference to its site, arterial supply, cellular structure and nervous connection modifying its activity. Then a hint was mentioned about the spread of cardiac excitation, the electrophysiology of cardiac stimulation. Also the genesis of the normal electrocardiogram from the electrical activity recorded by skin electrodes was discussed. The effect of the autonomic nervous system on the atrial and ventricular tissue specially the SA node was considered in this chapter.
This chapter also considers the pathophysiology of dysrhythmias that represent the main indication for pacing.Which includes sick sinus syndrome and complete heart block which are the most common indications for pacemakers which are considered in details with the other indications in next chapter. Any indication for permanent pacing is always an indication for temporary pacing in the preoperative period.
Temporary pacing is indicated prophylactically against life-threatining bradycardias, examples during and after cardiac surgery or pacemaker failure. At the end of this chapter a hint was mentioned about the electrophysiology of artificial cardiac pacing and the cardiovascular hemodynamic effects of pacing.
Temporary cardiac pacing can be accomplished transvenously through puncture of the internal jugular, subclavian, or femoral vein or percutaneously inserted. Other methods are via the esophagus, epicardially, more than 90 % of permanent cardiac pacemakers employ transvenous endocardial leads and the vessel of choice is the external jugular and subclavian.
A pacemaker consists of a power source, a lead and an electrodes. The pacemaker circuit may be a unipolar or a bipolar and cardiac stimulation circuit may be either endocardial or epicardial. There are different types of pacing modes. The most commonly implanted pacemaker nowadays is the demand ventricular pacemaker. Each pacing modality has different functional capabilities and therefore, specific indication and contraindications.
Programmability is the non-invasive persistent alterations of pacemaker characteristics within a preset range. Programming is achieved by using an external programmer. Almost all current pacemakers are multiprogrammable and the following are the commonly programmable functions: the rate, energy output, sensitivity, refractory period, hysteresis, blanking period, mode of function, A-V interval, lower-rate limit, upper rate response.
Surgical diathermy has important effects and uses during surgical operation. There are two types of surgical diathermy which are unipolar and bipolar surgical diathermy. A surgical diathermy could be a harmful equipment unless certain precautions are considered.
When a patient with an implanted pacemaker is undergoing any type of surgery, it is likely that most anesthesiologists will eventually care for these patients during surgery and diagnostic procedures. Preoperative evaluation of the patient should be complete with emphasis on undergoing the pathophysiology, severity and progression of the disease process that indicated pacemaker insertion. Usually patients should receive their prescribed doses of medications. Perioperative medication should be individualized for the patient’s needs. Laboratory work should include haemoglobin and electrolytes, also an ECG and chest radiograph should be done. The pacemaker should also be evaluated for proper functioning depending on whether the pacemaker is programmable or not. In programmable pacemakers with the appropriate programming device is the ideal.