Cardiac rhythm

Mechanisms of Cardiotoxicity Chemical compounds often affect the cardiac conducting system and thereby change cardiac rhythm and force of contraction. These effects are seen as alterations in the heart rate, conduction velocity of impulses within the heart, and contractivity. For example, alterations of pH and changes in ionic balance affect these cardiac functions. In principle, cardiac toxicity can be expressed in three different ways (1) pharmacological actions become amplified in an nonphysiological way (2) reactive metabolites of chemical compounds react covalently with vital macromolecules... 

ADMINISTERING HRETYLIUM. The nurse monitors cardiac rhythm and blood pressure continuously during administration. Hypotension and postural hypotension occur in about 50% of die patients receiving bretylium. If systolic pressure is less than 75 mm Hg, the nurse should notify the primary health care provider. The patient is kept supine until tolerance of postural hypotension develops. The nurse instructs the patient to change position slowly. Most individuals adjust to blood pressure changes within a few days. 

Waters RM, Orth OS, Gillespie NA. 1943. Trichloroethylene anesthesia and cardiac rhythm. 

Upon stabilization, placement of a pulmonary artery (PA) catheter may be indicated based on the need for more extensive cardiovascular monitoring than is available from non-invasive measurements such as vital signs, cardiac rhythm, and urine output.9,10 Key measured parameters that can be obtained from a PA catheter are the pulmonary artery occlusion pressure, which is a measure of preload, and CO. From these values and simultaneous measurement of HR and blood pressure (BP), one can calculate the left ventricular SV and SVR.10 Placement of a PA catheter should be reserved for patients at high risk of death due to the severity of shock or preexisting medical conditions such as heart failure.11 Use of PA catheters in broad populations of critically ill patients is somewhat controversial because clinical trials have not shown consistent benefits with their use.12-14 However, critically ill patients with a high severity of illness may have improved outcomes from PA catheter placement. It is not clear why this was... 

Consider tracheal intubation in cases of respiratory compromise. Treat patients who have bronchospasm with aerosolized bronchodilators. Use these and all catecholamines with caution because of the enhanced risk of cardiac dysrhythmias after exposure to some chemicals. When bronchodilators are needed, the lowest effective dose should be given and cardiac rhythm should be monitored. After decontamination, patients who are comatose,... 

Hypercalcemia, (weakness, headache, somnolence, nausea, cardiac rhythm disturbance), hypercalciuria... 

Arrhythmia is defined as loss of cardiac rhythm, especially irregularity of heartbeat. This chapter covers the group of conditions caused by an abnormality in the rate, regularity, or sequence of cardiac activation. 

The surface electrocardiogram (ECG) is the cornerstone of diagnosis for cardiac rhythm disturbances. 

After acute PSVT is terminated, long-term preventive treatment is indicated if frequent episodes necessitate therapeutic intervention or if episodes are infrequent but severely symptomatic. Serial testing of antiarrhythmic agents can be evaluated in the ambulatory setting via ambulatory ECG recordings (Holter monitors) or telephonic transmissions of cardiac rhythm (event monitors) or by invasive electrophysiologic techniques in the laboratory. 

Rapid diagnosis of cardiopulmonary arrest is vital to the success of CPR. Patients must receive early intervention to prevent cardiac rhythms from degenerating into less treatable arrhythmias. 

Cardiopulmonary arrest is diagnosed initially by observation of clinical manifestations consistent with cardiac arrest. The diagnosis is confirmed by evaluating vital signs, especially heart rate and respirations. Electrocardiography (ECG) is useful for determining the cardiac rhythm, which in turn determines drug therapy. 

Heart rate, cardiac rhythm, and blood pressure should be assessed and documented throughout the resuscitation attempt and after each intervention. Determination of the presence or absence of a pulse is paramount to deciding which interventions are appropriate. 

Reentrant cardiac rhythms, 5 82, 86, 87-88 Reentrant nematic phase, 15 102 Referee methods, of magnesium analysis, 15 348... 

High-level group term 334 Broad concepts for linking clinically related terms can be linked to one or more SOCs Cardiac rhythm disorders... 

Death. Chloroform levels of 40,000 ppm cause death in patients under chloroform anesthesia (Featherstone 1947 Whitaker and Jones 1965). Death is usually due to severe respiratory depression/ failure or disturbances in cardiac rhythm. Accidental or intentional ingestion of large doses of chloroform may lead to death (Piersol et al. 1933). Death in humans after oral exposure to chloroform is usually caused by respiratory obstruction by the tongue due to jaw relaxation, central respiratory paralysis, acute cardiac failure, or severe hepatic injury (Piersol et al. 1933 Schroeder 1965). 

Until the 1950s, the rare periodic phenomena known in chemistry, such as the reaction of Bray [1], represented laboratory curiosities. Some oscillatory reactions were also known in electrochemistry. The link was made between the cardiac rhythm and electrical oscillators [2]. New examples of oscillatory chemical reactions were later discovered [3, 4]. From a theoretical point of view, the first kinetic model for oscillatory reactions was analyzed by Lotka [5], while similar equations were proposed soon after by Volterra [6] to account for oscillations in predator-prey systems in ecology. The next important advance on biological oscillations came from the experimental and theoretical studies of Hodgkin and Huxley [7], which clarified the physicochemical bases of the action potential in electrically excitable cells. The theory that they developed was later applied [8] to account for sustained oscillations of the membrane potential in these cells. Remarkably, the classic study by Hodgkin and Huxley appeared in the same year as Turing s pioneering analysis of spatial patterns in chemical systems [9]. 

Acebntol is a selective j j-adrenoblocker. It possesses antianginal, antihypotensive, and antiarrhythmic action. It is nsed for arterial hypertension, preventing attacks of angina, and cardiac rhythm distnrbances. Synonyms of this drag are acebutolol, sectral, and others. 

Terminate IV therapy if persistent conduction disturbances or hypotension develop. As soon as the patient s basic cardiac rhythm appears to be stabilized, oral antiarrhythmic maintenance therapy is preferable (if indicated and possible). A period of approximately 3 to 4 hours (one half-life for renal elimination, ordinarily) should elapse after the last IV dose before administering the first dose of oral procainamide. 

Preexisting second- or third-degree AV block, right bundle branch block when associated with a left hemiblock (bifascicular block), unless a pacemaker is present to sustain the cardiac rhythm if complete heart block occurs recent myocardial infarction (Ml) presence of cardiogenic shock hypersensitivity to the drug. 

Injection - To relieve respiratory distress in bronchial asthma or during acute asthma attacks and for reversible bronchospasm in patients with chronic bronchitis, emphysema, and other obstructive pulmonary diseases severe acute anaphylactic reactions, including anaphylactic shock and cardiac arrest to restore cardiac rhythm. 

Cardiac events and fatalities Serious adverse cardiac events, including acute Ml, life-threatening disturbances of cardiac rhythm, and death have been reported following the administration of dihydroergotamine. 

Monitoring - Laboratory test monitoring for liver abnormalities is appropriate. Rapid IV administration Rapid IV administration of cimetidine has been followed by rare instances of cardiac arrhythmias and hypotension. Bradycardia, tachycardia, and premature ventricular beats in association with rapid administration of IV ranitidine may occur rarely, usually in patients predisposed to cardiac rhythm disturbances. 

Andrew EE, John PD, Kenneth AE, et al. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities. J Am Coll Cardiol. 2008 51 1-62. 

The treatment of an overdosage of digoxin requires monitoring of cardiac rhythm in order to detect arrhythmias. 

Parenteral /32-agonists such as albuterol (salbuta-mol) increase the activity of the membrane sodium-potassium ATPase, and so increase potassium entry into cells. Nebulized or infused albuterol (salbutamol) significantly lowers serum potassium concentration over 5 hours. A suitable initial dose of nebulized albuterol is 5 mg in adults. It can provoke tremor and tachyarrhythmia, and it is desirable to monitor cardiac rhythm during nebulization. The combination of nebulized albuterol (salbutamol) with infusion of insulin + glucose is more effective than the infusion alone. 

Serum concentrations have a major influence on the activity of quinidine on cardiac tissue. Low extracellular K+ concentrations antagonize the depressant effects of quinidine on membrane responsiveness, whereas high extracellular K+ concentrations increase quinidine s ability to depress membrane responsiveness. This dependency may explain why hypokalemic patients are often unresponsive to the antiarrhythmic effects of quinidine and are prone to develop cardiac rhythm disorders. 

Contraindications include hypersensitivity to local anesthetics of the amide type (a very rare occurrence), severe hepatic dysfunction, a history of grand mal seizures due to lidocaine, and age 70 or older. Lidocaine is contraindicated in the presence of second- or third-degree heart block, since it may increase the degree of block and can abolish the idioventricular pacemaker responsible for maintaining the cardiac rhythm. 

Propranolol is indicated in the management of a variety of cardiac rhythm abnormalities that are totally or partially due to enhanced adrenergic stimulation. In selected cases of sinus tachycardia caused by anxiety, pheochromocytoma, or thyrotoxicosis, (3-blockade will reduce the spontaneous heart rate. 

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