Flashcards in L63 – Shock and Heart Failure Deck (51):
Systemic, Generalized hypoperfusion of all cells and tissues due to failure of circulatory system
resulting in inadequate effective circulating volume
What are the 3 causes of shock?
Reduction in blood volume
Reduction in cardiac output
Redistribution of blood
What are the initial and protracted recovery of shock?
At first: reversible
Protracted: irreversible injury, death
What are the 4 types of Shock?
What is the cause of Hypovolaemic shock?
insufficient blood volume due to:
Hemorrhage > external and internal
Fluid loss > dehydration
Name some causes of external and internal hemorrhage?
External: chop / gunshot wounds, laceration
Hemoperitoneum due to ruptured aortic aneurysm
Ruptured ectopic pregnancy
What is the normal plasma, interstitial and intracellular fluid volumes?
Plasma 3 L
Interstitial fluid 11 L
Intracellular fluid 28 L
What is the normal blood volume?
5L > 60% plasma and 40% RBC
Body can compensate up to how many percentage fluid loss?
up to 20%
What is the effect of <10% volume loss on cardiac output ?
symptomatic (no change in arterial pressure, cardiac output)
What is the effect of 15%-25% volume loss on cardiac output ?
cardiac output starts to drop >> compensated hypotension
Explain the mechanism for maintaining BP in hypovolemia?
stimulation> release catecholamines > peripheral vasoconstriction
Atrial stretch receptor firing decrease > CVS centre > hypothalamus > release ADH to increase blood volume
Autoregulation > maintain perfusion to brain, heart but not other organs
Renal RAAS activation
What are the 4 stages of hypovolemic shock?
Early stage (15-25%)
Progressive/ advanced stage
How does progressive/ advanced stage hypovolemia occur?
when no therapeutic intervention is given for the early stage
What are the results of progressive/ advanced stage hypovolemia?
Same mechanisms stimulated in early stage to restore volume
- Irreversible damage to organs and tissue due to impaired perfusion, hypoxia
- Multi-organ breakdown by ischaemia
- Cardiac depression
- Tissue inflammation further decrease volume and CO
Explain the vicious cycle in progressive or decompensated shock?
Decreased CO > cardiac depression > decrease tissue perfusion > tissue necrosis
> Release of toxins > increase capillary permeability > further loss in volume
> further decrease in CO
What causes cardiac depression?
Decreased cardiac nutrition
How does decrease blood flow to brain lead to vascular dilation?
Decreased flow to brain > decreased nutrition of brain
> Decrease VASOMOTOR activity
> Vascular dilation
What type of hypersensitivity reaction is Anaphylactic shock?
What triggers anaphylactic shock?
+ prior sensitization
How does anaphylactic shock lead to DAD?
injured endothelium, epithelium >>
Inflammatory mediators cause Vasodilatation of
>> Interstitial edema, congested capillary, hyperplasia of type II pneumocyte and hyaline membrane formation
>> Exudate leak into alveolar airspace >> DAD
WHat is the treatment for anaphylactic shock?
inject adrenaline >> peripheral vasoconstriction to conserve blood volume
What are some symptoms of anaphylactic shock?
Swollen lips, eyes, soft tissue > skin rashes
Swollen mucosal lining > breathing difficulty
What occurs in cardiogenic shock?
Suddenly Weakened heart cannot pump enough blood to meet body's needs
What are the causes of cardiogenic shock?
Acute myocardial infarction
What are the causes of cardiac tamponade?
Fluid buildup in pericardial sac > exert pressure on heart
Ruptured dissecting aortic aneurysm
Penetrating injury to heart
What is the leading cause of septic shock?
Severe infection by Gram-negative, endotoxin-producing bacteria
What are some predisposing factors of septic shock?
- Debilitating diseases (e.g. neoplasm)
- Mechanical carriage of bacteria into blood during surgery
- Health status (e.g. nutrition)
Compare cardiogenic and septic shock. Which one causes more death in hospital settings?
What is the pathogenesis of septic shock?
1. Endotoxins > extensive endothelial damage
2. Disseminated intravascular coagulopathy
3. Inflammatory reaction
What are the common causes of septic shock?
Infection spreading into blood from kidney, urinary tract (E. coli)
Generalised infection from streptococcal / staphylococcus skin infections
Generalized gangernous infections
Name 2 causes of Peritonitis that can lead to septic shock?
From instrumental abortion and ruptured guts
What is the difference between procoagulant and anti-fibrinolytic factors?
Activate clotting factors
Consume clotting factors
What is the result of Histamines, complements activating endothelium?
Increase vascular permeability
Heart failure can be due to pressure or volume problems?
What is ejection fraction?
fraction of volume of blood in left ventricle that is pumped out with each ejection / contraction
How is ejection fraction calculated?
(EDV - ESV)/ EDV
EDV = end-diastolic volume
ESV = end-systolic volume
What is the normal and abnormal ejection fraction?
Normal = 55-70%;
Abnormal = <40%
What are the vasoconstricting systems?
What are the vasodilating systems?
Endothelium relaxing factors
Atrial natriuretic factor
What are the most common causes of Heart failure with decreased ejection fraction?
Ischaemic heart disease; or
Diseases that result in damage to heart muscles
What are some muscle abnormalities of the heart? (diseases)
What diseases affect the coordination of heart pumping?
Abnormal rhythms (nerve issue)
3 ways the heart fails?
Physically prevented from pumping
How does heart failure with decreased ejection fraction lead to pulmonary regurgitation?
Ventricular wall is weakened, dilated:
End-diastolic volume increases and ejection fraction decreases
Increase residual volume leads to regurgitation to pulmonary vessels
What is the common cause of Heart failure without drop in ejection fraction?
LV hypertrophy and decrease filling
How come ejection fraction is still normal in some heart failures?
Decrease in stroke volume
but relative to volume of LV, the ejection fraction maintains normal
What are the clinical examination results of heart failure?
Third heart sound
What is the function of nitroglycerin?
Vasodilator and pain relieve
What is the function of Digitalis?