5. Renal Responses To Systemic Disorders Flashcards
What happens in congestion cardiac failure?
Occurs when heart muscle pump cannot cope with its workload
Cardiac output falls and fails to perfuse tissues adequately
Why does hypoperfusion result in?
Na+ and water retention by the kidneys, leading to oedema
Renal hypoperfusion is sensed by the kidneys as hypovolemia, resulting in compensation by retaining NaCl and water to increase circulating fluid volume (RAAS system stimulated)
What does management of CCF involve?
Reducing fluid load of body and thereby decreasing the workload of the heart
- diuretics
- ACE inhibitors
- nitrates
- vasodilators
What does increase in pulmonary venous pressure result in?
Transudation from the capillaries in the lungs and in pulmonary oedema
What is hypervolaemia often due to?
Kidney retention of sodium and water Reduced effective arterial volume Excessive sodium or fluid intake Cirrhosis Hyperaldosteronism
What are symptoms of hypervolaemia?
Coughing Tiredness Shortness of breath Plural effusion Ascites Pulmonary oedema Pumping action of heart grows weaker Oedema
What does shock from hypovolaemia lead to in the kidney?
Acute tubular necrosis (ATN)
What does a severe decrease in circulating volume stimulate?
Sympathetic activity to maintain the BP by tachycardia, peripheral vasoconstriction and increase in myocardial contractility
When can hypovolaemic shock occur?
Loss of blood volume from blood loss, loss of plasma (burns), loss of water and electrolytes (D&V)
How does the body counteract excessive vasoconstriction?
More prostaglandins are secreted within the kidneys
This maintains adequate blood flow through the kidney and sufficient GFR unless the shock is severe
What are the 2 major consequences of loss of large amounts of fluid?
Volume depletion - decreases tissue perfusion
Electrolyte and acid-base disturbances
How do you treat hypovolaemic shock?
Fluid replacement to restore ECF or may need blood transfusion
What happens if blood flow to the kidneys is not restored?
Acute kidney injury results from tissue anoxia and necrosis
What happens in hypertensive renal disease?
- Renal autoregulation maintains renal function despite variations in systolic BP
- Increase in BP transferred to kidney/glomerulus
- Arteriosclerosis of the major renal arteries occur and hyalinisation of small vessels with intimal thickening
- Can lead to chemical renal damage and reductions in size of kidneys
What are the renal causes of secondary hypertension?
Impaired Na+ and water excretion, increase blood volume
Stimulation of renin release
Most diseases of the kidney can result in hypertension
Renal artery stenosis - reduced perfusion, therefore excessive activation of RAAS
