Myocardial function

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

Li, X.Y., Sun, S.Z. Bradamante, S., Piccinini, F. and Bolli, R (1993). Effects of the spin trap alpha-phenyl-N-tert-butylnitrone on myocardial function and flow a dose response study in the open chest dog and in the isolated rat heart. Free Rad. Biol. Med. 14 (3), 277-285. 

Heart failure is a clinical syndrome characterized by a history of specific signs and symptoms related to congestion and hypoperfusion. As HF can occur in the presence or absence of fluid overload, the term heart failure is preferred over the former term congestive heart failure. Heart failure results from any structural or functional cardiac disorder that impairs the ability of the ventricle to fill with or eject blood.1 Many disorders such as those of the pericardium, epicardium, endocardium, or great vessels may lead to HF, but most patients develop symptoms due to impairment in left ventricular (LV) myocardial function. 

Unlike other adrenoblockers, labetalol lowers blood pressure more by lowering resistance of peripheral vessels than by suppressing myocardial function. This, along with a reduction in pressure, fails to change heart rate. Currently, eight of the most frequently used j8-adrenoblock-ers in medicine are used for hypertension therapy, and their syntheses are described in Chapter 12. They are propranolol (12.1.3), metoprolol (12.1.5), acebutol (12.1.6), athenolol (12.1.7), nadolol (12.1.8), pindolol (12.1.9), timolol (12.1.10), and labetalol (12.1.12). 

Hemodynamic effects - Small decreases in cardiac output and increases in systemic vascular resistance have occurred, with no significant negative inotropic effect. Blood pressure and pulse rate remain essentially unchanged. Mild depression of myocardial function has been observed following IV mexiletine (dosage form not available in the US) in patients with cardiac disease. 

Anesthesia and major surgery If carvedilol treatment is to be continued perioperatively, take particular care with anesthetic agents which depress myocardial function. 

Heyndrickx GR, Millard RW, McRitchie RJ, Maroko PR, Vatner SF. Regional myocardial functional and electrophysiological alterations after brief coronary artery occlusion in conscious dogs. J Clin Invest 1975 56 978-985... 

Opioids play an important role in anesthetic practice. Opioid analgesics potentiate the efficacy of anesthetics. They can be given as part of the premedication as well as during the operation. Examples of short acting agents with high potency are fentanyl, sufentanyl, alfentanil and remifentanil. Because of their hemodynamic stability these agents can be used for patients with compromised myocardial function. Respiration must be maintained artificially and may be depressed into the postoperative period. They are usually supplemented with inhalation anesthetic, benzodiazepines or propofol. 

Although myocardial depression is not a problem in patients with normal cardiac function, in patients with compromised myocardial function, quinidine may depress cardiac contractility sufficiently to result in a de-... 

Disopyramide directly depresses myocardial contractility. The negative inotropic effect may be detrimental in patients with compromised cardiac function. Some patients develop overt congestive heart failure. At usual therapeutic doses, depression of myocardial function is not a problem in most patients with normal ventricular function. 

Lidocaine does not depress myocardial function, even in the face of congestive heart failure, at usual doses. 

Propranolol is contraindicated for patients with depressed myocardial function and may be contraindicated... 

Although opioid anesthesia is particularly useful in patients with compromised myocardial function, the opioids depress respiration by inhibiting the responsiveness of the medullary respiratory center to PCO2 and alter the rhythm of breathing. Consequently, it is necessary to assist ventilation intraoperatively. Since respiratory depression may extend into the postoperative period as a result of drug accumulation in the tissues, the use of opioids whose clearances are slow, remain most appropriate for patients who are expected to require postoperative ventilatory care. 

Patients with coronary artery disease are particularly challenging for anesthesia, since alterations in vascular responsiveness and myocardial function may put them at risk. In this respect, which statement correctly describes the cardiovascular action of an agent or agents that should be taken into account when planning anesthesia for such patients ... 

The most important toxicities caused by doxorubicin involve the heart and bone marrow. Acutely, doxorubicin may cause transient cardiac arrhythmias and depression of myocardial function. Doxorubicin may... 

The effects of sympathomimetic drugs on blood pressure can be explained on the basis of their effects on heart rate, myocardial function, peripheral vascular resistance, and venous return (see Figure 6-7 and Table 9-4). The endogenous catecholamines, norepinephrine and epinephrine have complex cardiovascular effects because they activate both and 13 receptors. It is easier to understand these actions by first describing the cardiovascular effect of sympathomimetics that are selective for a given adrenoreceptor. 

Isojarvi JI, Airaksinen KE, Mustonen JN, Pakarinen AJ, Rautio A, Pelkonen O, Myllyla VV. Thyroid and myocardial function after replacement of carbamazepine by oxcarbazepine. Epilepsia 1995 36(8) 810-6. 

Alpha-adrenergic antagonists are used primarily as antihypertensive drugs because of their ability to block vascular alpha-1 receptors. Beta-adrenergic antagonists (beta blockers) are administered primarily for their inhibitory effects on myocardial function and are used in the prevention and treatment of hypertension, angina pectoris, arrhythmias, and myocardial reinfarction. Many of the drugs introduced in this chapter are discussed further in chapters that deal with the specific clinical conditions (e.g., hypertension, asthma, and other disorders). 

Brief History. M.R. is a 48-year-old man with a history of coronary artery disease and cardiac rhythm disturbances. Specifically, he has experienced episodes of paroxysmal supraventricular tachycardia, with his heart rate often exceeding 180 beats per minute. He has been treated for several years with the nonspecific beta blocker propranolol (Inderal). Oral propranolol (60 mg/d) has successfully diminished his episodes of tachycardia. In an effort to improve his myocardial function and overall cardiovascular fitness, M.R. recently enrolled as an outpatient in a cardiac rehabilitation program. Under the supervision of a physical therapist, he attended cardiac training sessions three times each week. A typical session consisted of warm-up calisthenics, bicycle ergometry, and cool-down stretching activities. Each session lasted approximately 45 minutes. 

Parenteral administration of 27 to 60 jLig/kg of selenium to laboratory animals has been shown to inhibit doxorubicin-induced decreases in myocardial vitamin E and GSH peroxidase levels and to reduce changes in myocardial function that are consistent with acute doxorubicin-induced cardiotoxicity. Oral supplementation of sodium selenite also protects against acute doxorubicin-induced cardiotoxicity in rabbits. 

If the underlying disease causes cardiac function to deteriorate despite expansion of plasma volume, the kidney continues to retain salt and water, which then leaks from the vasculature and becomes interstitial or pulmonary edema. At this point, diuretic use becomes necessary to reduce the accumulation of edema, particularly that which is in the lungs. Reduction of pulmonary vascular congestion with diuretics may actually improve oxygenation and thereby improve myocardial function. Edema associated with heart failure is generally managed with loop diuretics. In some instances, salt and water retention may become so severe that a combination of thiazides and loop diuretics is necessary. 

Significant depression of myocardial contractility has been observed in individuals who acutely consume moderate amounts of alcohol, ie, at a blood concentration above 100 mg/dL. Myocardial biopsies in humans before and after infusion of small amounts of alcohol have shown ultrastructural changes that may be associated with impaired myocardial function. Acetaldehyde is implicated as a cause of cardiac dysfunction by altering myocardial stores of catecholamines. 

Chen ER Bittner HB, Davis RD, Van Trigt R Folz R. Physiological effects of extracellular superoxide dismutase transgene overexpression on myocardial function after ischemia and reperfusion injury. J Thorac Cardiovasc Surg 1998 I 15 450-458. 

I Harada K, Grossman W, Friedman M, et al. Basic fibroblast growth factor improves myocardial function in chronically ischemic porcine hearts. J Clin Invest 1994 94(2) 623-630. 

Improves myocardial function after cold storage with preservation solution supplemented with it [159]... 

The subtle chronic abnormalities in myocardial function that occur 10-20 years after anthracycline exposure in childhood are best detected by exercise echocardiography, since these patients may have normal resting cardiac function (40). 

Pihkala J, Saarinen UM, Lundstrom U, Virtanen K, Virkola K, Siimes MA, Pesonen E. Myocardial function in children and adolescents after therapy with anthracyclines and chest irradiation. Eur J Cancer 1996 32A(1) 97-103. 

Hesseling PB, Kalis NN, Wessels G, van der Merwe PL. The effect of anthracyclines on myocardial function in 50 long-term survivors of childhood cancer. Cardiovasc J South Afr 1999 89(Suppl l) C25-8. 

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