Chapter 21 - Fluid and Diuretic Therapy in Heart Failure

Question 1

What is the formula of arterial blood pressure?

Answer 1

CO x SVR

Question 2

What are the neural/hormonal/cardiovascular adaptations to preserve blood pressure?

Answer 2

1. Activation of sympathetic nervous system and release of hormones
2. Increased systemic vascular resistance
3. Reduction of autonomic reflex activity
4. Cardiac remodeling

Question 3

T/F: forward failure refers to clinical signs of low cardiac output, but instead describes the renal response triggered by low cardiac output.

Answer 3

False. Renal sodium and water retention as a consequence of reduced cardiac output

Question 4

T/F: ventricular stroke volume is directly related to ventricular filling pressure

Answer 4

True

Question 5

What is the LA pressure in order to develop pulmonary edema from acute CHF?

Answer 5

> 20mmHg

Question 6

T/F: pleural effusion correlates better with pulmonary capillary wedge pressure than with right atrial pressure

Answer 6

True

Question 7

True/false: pleural effusion may become chylous in nature in patients with advanced CHF

Answer 7

True

Question 8

Why do some dogs and cats develop pulmonary edema after administration of maintenance IV crystalloid solution?

Answer 8

The vascular compliance of the pulmonary circulation is much smaller than that of the systemic circulation, and sudden expansion of the plasma volume usually increases pulmonary venous pressure more than systemic venous pressure.

Question 9

Why cannot CVP be used to gauge the effect of IVF on left sided cardiac filling pressure, especially in the setting of isolated left sided CHF?

Answer 9

Difference in vascular compliance and cardiac function.

Left sided filling pressure may increase much more rapidly than CVP, though both increase simultaneously.

Question 10

What are indications for fluid therapy in patients with CHF?

Answer 10

Persistent anorexia, dehydration, renal failure, moderate to severe hypokalemia, digitalis intoxication, drug-induced hypotension, gastroenteritis, anemia, and serious metabolic (e.g., diabetes mellitus), neoplastic, or infectious diseases.
Need for intravenous drugs.
Pericardial disease.
General anesthesia.

Question 11

Why are diuretics still recommended in the CHF patient requiring fluid therapy?

Answer 11

• Diuretics must be given concurrently to prevent untoward retention of sodium derived from the diet or crystalloid therapy (electrolyte management).
• Diuretic therapy also promotes redistribution of extracellular water from edematous sites to the venous system.
• Furosemide also acts initially to increase GFR (possibly by releasing vasodilating prostaglandins) –> need for water intake or fluid therapy to avoid decreased cardiac filling and GFR

Question 12

What are the IV fluids recommended for patients with CHF?

Answer 12

5% dextrose or 0.45% NaCl in 2.5% dextrose

Question 13

What are the most common electrolyte disturbances seen with diuretic therapy?

Answer 13

Hypokalemia, hypochloremia, and metabolic alkalosis

Question 14

What diuretics are less likely to induce hypokalemia?

Answer 14

ACE inhibitors, spironolactone

Question 15

What is the worst prognostic factor in patients with CHF: hyponatremia or hypernatremia?

Answer 15

Hyponatremia

Question 16

What are causes for hyponatremia in the patient with CHF?

Answer 16

• Impaired renal water excretion related to persistent release of ADH
• Diuretics causing hypokalemia, inducing plasma volume depletion and release of ADH, and impairing function in the diluting segments of the nephron
• Thiazide diuretics

Question 17

What respiratory rates in resting dogs correlates well with radiographic evidence of pulmonary edema?

Answer 17

Respiratory rates exceeding 35 to 40 in resting dogs

Question 18

What CVP and pulmonary wedge pressure are typically associated with formation of edema in patients with CHF?

Answer 18

Pulmonary wedge pressure greater than 20 mm Hg and CVP greater than 10 to 12 cm H2O may be associated with formation of edema.

Question 19

In patients with CHF, what does a ventricular (S3) gallop sound typically corresponds to?

Answer 19

A ventricular (S3) gallop sound typically corresponds to elevated filling pressures and as such will be diminished or eliminated with effective diuresis or management of heart failure.

Question 20

What is pulmonary capillary wedge pressure equivalent to?

Answer 20

Pulmonary capillary wedge pressure is equivalent to the mean left ventricular filling pressure

Question 21

What do these situations correspond to?
• Normal cardiac output and normal pulmonary capillary wedge pressure
• Normal cardiac output with high pulmonary capillary wedge pressure predisposing to edema
• Low cardiac output and low pulmonary capillary wedge pressure
• Low cardiac output and high pulmonary capillary wedge pressure

Answer 21

• Normal cardiac output and normal pulmonary capillary wedge pressure (the normal situation)
• Normal cardiac output with high pulmonary capillary wedge pressure predisposing to edema (left-sided CHF with volume expansion)
• Low cardiac output and low pulmonary capillary wedge pressure (volume depletion, as with excessive diuresis)
• Low cardiac output and high pulmonary capillary wedge pressure (severe left-sided heart failure, cardiogenic shock)

Question 22

How are the wedge pressure and CVP in patients with biventricular CHF?

Answer 22

In biventricular CHF, both the wedge pressure and CVP are abnormally high