chapter 22 cardiac failure Flashcards
define cardiac failure
failure of the heart to pump enough blood to satisfy the body’s needs
2 acute effects from cardiac failure
reduced cardiac output, damming of blood in the veins which increases venous pressure
name some ways the body compensates for acute cardiac failure by sympathetic responses
baroreceptor reflex, chemoreceptor reflex, CNS ischemic response.
4 detrimental effects of excess fluid retention in severe cardiac failure
- increasing the work load of heart, 2. overstretcthing the heart which weakens the heart, 3. filtration of fluid into the lungs, causing pulmonary edema and deoxygenation of blood, 4. development of edema in the body
decompensated heart failure is what
the damage is so much that the body cannot compensate at all. The kidneys cant excrete enough fluid and edema develops all throughout the body
What is the critical cardiac output level required in a normal adult?
5L of blood a minute
Failure of the cardiac output to rise to the critical level required for normal renal function results in 3 things
- retention of more and more fluid, 2. Progressive elevation of mean systolic filling pressure, 3. progressive elevation of right atrial pressure
how can the decompensation process be stopped?
- strengthening the heart with cardiotonic drugs like digitalis. This makes the heart strong enough to pump enough blood for proper kidney function.
- administering diuretic drugs to increase kidney excretion
how do cardiotonic drugs like digitalis and cardiotonic glycosides strengthen the heart?
increase the amount of calcium ions in the muscle fibers
describe pulmonary edema
when the left heart fails without the right. Blood is pumped into the lungs quicker than the blood can be pumped out of the left heart. This causes the mean pulmonary filling pressure to rise which increases the pulmonary capillary pressure. If it rises above the colloid pressure it filters out of the capillaries into the interstitial spaces of the alveoli causing edema
define cardiac shock
inadequate cardiac pumping
Can acute left heart failure cause death?
yes, within minutes to hours
Why does acute cardiac failure not cause peripheral edema?
Becaue the capillary pressure actually falls not increases. ( since the left heart isnt pumping well, the aortic pressure falls, which means the peripheral capillary pressure falls, but the right atrial pressure increases.)
what actually causes the peripheral edema?
long term retention by the kidneys
whats happening with pressures during long term kidney retention? (specifically the right atrial and the capillary pressures)
This increases the blood to the heart which increases the right atrial pressure and returns the aterial pressure back to normal. Now there is an increase in Capillary pressure which causes the peripheral edema.
name some common reasons of reduced renal output of urine during cardiac failure
decreased glomerular filtration rate, activation of renin-angiotensin system and increased reabsorption of water and salt by renal tubules, increased aldosterone secretion, activation of sympathetic nervous system
What is ANP and where is it found and what does it do?
Atrial natriuretic peptide, released by atrial walls when they are stretched and it tells the kidneys to increase excretion of salt and water
describe the vicious acute pulmonary edema circle
a weak left heart leads to pooling of blood in lungs, this leads to less oxygenated blood which further weakens the heart, this leads to peripheral vasodilation which pushes more blood to the lungs which pools more blood into the lungs. ( this repeats and repeats)
therapeutic measures for those going through the pulmonary edema circle
tourniquets on limbs, duretic to loose fluid, oxygen mask, cardiotonic drug like digitalis to strengthen heart
what is cardiac reserve
the maximum percentage that the cardiac output can increase above normal .
whats the cardiac reserve in a adult
300-400%
Diagnosis of low cardiac reserve
- shortness in breath( dyspnea),2. muscle fatigue, 3. increase in heart rate.
name 2 conditions that cause high cardiac output failure
Arteriovenous fistula, beriberi
Arteriovenous fistula
This is a direct opening between a large artery and large vein. This decreases vascular resistance. This causes a raise in venous return which pretty much overloads the heart and lowers the cardiac reserve since it is alreay near its maximum capacity to pump blood through the AV fistula
Beriberi
Decreased cardiac output is caused by weakening of the heart from avitaminosis( lack of vitamins, specifically thiamine (B1)). Weak heart means less blood to the kidneys which causes retaining of fluid. This also causes a rise in venous return.
