Loop diuretics heart failure

Loop diuretics are the drugs of choice for the treatment of edematous patients with congestive heart failure, cirrhosis of the liver, and nephrotic syndrome. Excretion of Na is helpful only to the extent that some of the... 

TABLE 3-6. Loop Diuretics Used in Heart Failure... 

Loop diuretics Congestive heart failure and pulmonary edema, ascites... 

FIGURE 8-2. General treatment algorithm for acute decompensated heart failure (ADHF) based on clinical presentation. IV vasodilators that may be used include nitroglycerin, nesiritide, or nitroprusside. Metolazone or spironolactone may be added if the patient fails to respond to loop diuretics and a second diuretic is required. IV inotropes that may be used include dobutamine or milrinone. (D/C, discontinue HF, heart failure SBP, systolic blood pressure.) (Reprinted and adapted from J Cardiac Fail, Vol 12, pages el-el 22, copyright 2006, with permission from Elsevier.)... 

Treat the heart failure, increase diuretic dose, switch to better-absorbed loop diuretic... 

Therapy of congestive heart failure. By lowering peripheral resistance, diuretics aid the heart in ejecting blood (reduction in afterload, pp. 132, 306) cardiac output and exercise tolerance are increased. Due to the increased excretion of fluid, EEV and venous return decrease (reduction in preload, p. 306). Symptoms of venous congestion, such as ankle edema and hepatic enlargement, subside. The drugs principally used are thiazides (possibly combined with K+-sparing diuretics) and loop diuretics. 

These potent diuretic agents interact with almost the entire nephron, including Henle s loop (Fig. 7). Their primary effect is probably the inhibition of the active reabsorption of chloride ions, which then leads to the enhanced excretion of sodium ions and water. Plasma volume is reduced as a result of these effects, whereas in the long-term both cardiac preload and afterload will diminish. The metabolic side-effects of the loop diuretics are globally the same as those of the thiazides, with some incidental differences. Plasma renin activity increases by loop diuretic treatment and it can be well imagined that this effect is noxious in the long-term management of heart failure. The loop diuretics provoke a clearly... 

Potassium-sparing diuretics, such as amiloride and triamterene. These agents reduce at the tubular level the reabsorption of sodium and water, whereas the excretion of potassium is diminished. Their primary effects are independent of aldosterone. They are slow-acting and weak diuretics, which are unsuitable as monotherapy of hypertension or heart failure. For this reason, they are always combined with thiazide or loop diuretics. Several combined preparations are commercially available. 

Diuretics (loop) Renal insufficiency Heart failure Not used in other hypertensives Pregnancy... 

Fluid overload occurs commonly in patients with renal failure, often in the absence of associated heart disease. If salt and water intake is not controlled in the patient who is oliguric or anaemic, plasma volume and symptoms of congestive heart failure ensue. Hypertension and coronary heart disease with increasing age contributes to the congestive heart failure. Diuretics like loop-diuretics or metolazone may be of value. Digitalis should be used with caution in patients on dialysis as cardiac arrhythmias may ensue in patients receiving dialysis in the presence of hypokalemia. 

Management necessitates correction of the underlying cause. In unusually severe cases, with haemoglobin levels as low as 20 or 30 g/1 and particularly in elderly patients where heart failure is present, a single unit of packed red cells can be given over 6 hours with a loop-acting diuretic such as 10 mg of oral or intravenous furosemide. Haemoglobin levels will correct at the rate of 20 g/1 every 3 weeks provided replacement is adequate. It should be noted that for stores to be reconstituted 3 and sometimes 6 months of oral treatment are needed. 

Both drugs are used in conjunction with other diuretics like thiazide or loop diuretics to augment natriuresis and reduce loss of potassium. Triamterene may be used in the treatment of congestive heart failure, cirrhosis and the edema caused by secondary hyperaldosteronism. Amiloride is also useful in lithium induced diabetes insipidus. 

Loop diuretics Furosemide Block Na/K/2CI transporter in renal loop of Henle Like thiazides t greater efficacy Severe hypertension, heart failure See Chapter 15... 

Furosemide Loop diuretic Decreases NaCI and KCI reabsorption in thick ascending limb of the loop of Henle in the nephron (see Chapter 15) Increased excretion of salt and water reduces cardiac preload and afterload reduces pulmonary and peripheral edema Acute and chronic heart failure severe hypertension edematous conditions Oral and IV duration 2-4 h Toxicity Hypovolemia, hypokalemia, orthostatic hypotension, ototoxicity, sulfonamide allergy... 

See Table 15-6. Potassium-sparing diuretics are most useful in states of mineralocorticoid excess or hyperaldosteronism (also called aldosteronism), due either to primary hypersecretion (Conn s syndrome, ectopic adrenocorticotropic hormone production) or secondary hyperaldosteronism (evoked by heart failure, hepatic cirrhosis, nephrotic syndrome, or other conditions associated with diminished effective intravascular volume). Use of diuretics such as thiazides or loop agents can cause or exacerbate volume contraction and may cause secondary hyperaldosteronism. In the setting of enhanced mineralocorticoid secretion and excessive delivery of Na+ to distal nephron sites, renal K+ wasting occurs. Potassium-sparing diuretics of either type may be used in this setting to blunt the K+ secretory response. 

The diuretic and mild vasodilator actions of the thiazides are useful in treating virtually all patients with essential hypertension and may be sufficient in many. Loop diuretics are usually reserved for patients with renal insufficiency or heart failure. Moderate restriction of dietary Na+ intake (60-100 mEq/d) has been shown to potentiate the effects of diuretics in essential hypertension and to lessen renal K+ wasting. 

Loop diuretics, the next class of diuretic drugs to be developed, are also the most potent. Their introduction was a major advance in the treatment of congestive heart failure. Furosemide (Lasix), the first of the loop diuretics, debuted in 1965. 

In addition to their diuretic activity, loop agents appear to have direct effects on blood flow through several vascular beds. Furosemide increases renal blood flow. Furosemide and ethacrynic acid have also been shown to reduce pulmonary congestion and left ventricular filling pressures in heart failure before a measurable increase in urinary output occurs, and in anephric patients. 

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. 

Profound first-dose hypotension can occur when ACE inhibitors are introduced to patients with heart failure. This effect may be particularly pronounced if the patient is taking a high dose of a loop diuretic. Temporary withdrawal of the loop diuretic could be considered but is not appropriate in this case as it may cause rebound pulmonary oedema. Therefore in this case the steps are to initiate the ACE inhibitor at low dose (e.g. ramipril 1.25 mg daily at night time while the patient is lying down) and then to monitor blood pressure hourly for the first 4 hours. 

Bumetanide 1 mg od Loop diuretic, why BP is low, what evidence of heart failure is there ... 

Thiazide diuretics are ineffective once the GFR becomes less than 25 mL/min, and loop diuretics are often used at high doses (e.g. furosemide 500 mg to 1 g daily) to gain an effect. Metolazone is effective when combined with a loop diuretic. Potassium-sparing diuretics such as amiloride are not recommended. Spironolactone is not generally used, but is beneficial in low dose for the treatment of heart failure even in patients on dialysis. Beta-blockers and calcium channel blockers are generally well tolerated. Any ankle swelling with calcium channel blockers must not be confused with fluid overload. 

Q9 What is the mechanism of action of loop diuretics and why may they be more useful in congestive heart failure than the thiazides ... 

Treat the heart failure, increase diuretic dose, switch to better-absorbed loop diuretic High-volume paracentesis Higher dose of diuretic, diuretic combinatbn therapy, add lowdose dopamine... 

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