Lecture 15: Cardiac failure heart sounds and shock Flashcards
Cardiac failure definition
Failure of the heart to pump enough blood to satisfy the needs of the body
Effects of sympathetic innervation in cardiac failure
Strengthens muscle contraction
Increases tone of most vessels, especially veins
Increases mean systemic filling pressure
Compensatory mechanism by ANS for acute cardiac failure
Baroreceptor reflex
Chemoreceptor reflex
CNS ischemic response
Acute effects of heart attack
Reduced cardiac output
Damming of blood in veins–> increased venous pressure
Effect of increased right atrial pressure during heart attack
Increased right atrial pressure can maintain cardiac output at near normal levels despite a weak heart
Exercising while in compensated heart failure
Causes immediate return of symptoms to acute heart failure
What happens to capillary pressure during heart failure and what are the results
Capillary pressure decreases which reduces chances of peripheral edema
What causes pulmonary edema
Left side of heart fails without failure of right side
Blood is pumped into lungs but not out of lungs
Pulmonary filling pressure rises, capillary pressure rises
Blood can then flow out of capillaries into lungs causing edema
Two major problems of left heart failure
Pulmonary vascular congestion
Pulmonary edema
Changes in aortic, capillary and right atrial pressure during heart failure
Aortic pressure drops
Capillary pressure drops
Right atrial pressure increases
Atriovenous fistula
Overloads heart because of excessive venous return caused by decrease in peripheral vascular resistance
Venous return curve rotates upward
Beriberi
Thiamin deficiency Weakening of heart Decreased blood flow to kidney-->fluid retention Increased mean filling pressure Shift of venous return curve to right
First heart sound
AV valves close at the onset of ventricular systole
Second heart sound
Semilunar valves close at end of systole
Left to right shunt and example of condition
Blood flows backward and fails to flow through systemic circulation
Patent ductus arteriosus
Right to left shunt
Blood flows from right to left side of heart, bypassing lungs
Tetralogy of fallot
Circulatory shock definition
Inadequate blood flow throughout the body to the extent that tissues are damaged because of low oxygen/nutrients
Cardiac abnormalities that decrease ability to pump blood
Myocardial infarction
Toxic state of heart
Severe valve dysfunction
Heart arrhythmias
Cardiogenic shock is
Circulatory shock resulting from diminished cardiac pumping ability
Factors that decrease venous return
Diminished blood volume
Decreased vascular tone
Obstruction of blood flow
Negative feedback mechanisms during cardiac shock
Powerful sympathetic reflux initiated by arterial baroreceptors and vascular stretch receptors
-Results from decrease in arterial pressure after hemorrhage and decrease in pressures in pulmonary arteries and veins
Sympathetic reflexes in cardiac shock result in
Arterioles constrict in most of circulatory system
Veins and venous reservoirs constrict
Heart activity increases markedly
Autoregulation in cerebral and cardiac vessels
Maintain more or less normal pressure as long as the arterial pressure does not drop below 70mm Hg
Baroreceptor reflexes
Elicit powerful sympathetic stimulation of circulation
Central nervous system ischemic response
Elicits even more powerful sympathetic stimulation throughout body but is not activated until arterial pressure drops below 50mm Hg
Reverse stress relaxation of the circulatory system
Causes blood vessels to contract around the diminished blood volume so that the blood volume that is available more adequately fills the circulation
Increased secretion of renin by the kidneys and formation of angiotensin II
Constricts the peripheral arteries and also causes decreased outputs of water and salt by the kidneys
Increased secretion by the posterior pituitary gland of vasopressin (ADH)
Constricts peripheral arteries and veins and greatly increases water retention by kidneys
Increased secretion of epinephrine/norepinephrine by adrenal meddula
Constricts peripheral arteries/veins and increases heart rate
Compensatory mechanisms that return blood volume back to normal
Absorption of large quantities of fluid from intestinal tract
Absorption of fluid into the capillaries from interstitial spaces of body
Conservation of water/salt by kidneys
Increased thirst and appetite for salt
Factors in the final lethal progression of shock
Vasomotor failure Blockage of small vessels Increased vascular permeability Release of toxins by necrotic tissue Cardiac depression caused by endotoxin Generalized cellular deterioration
Neurogenic shock
Shock may occur without loss of blood volume
Vascular capacity increases so much that normal amount of blood cannot fill space
Causes of neurogenic shock
Sudden loss of vasomotor tone-dilation of veins
Deep general anesthesia
Spinal anesthesia
Brain damage
