Week 9 Acute Kidney Injury

Question 1

what is pre renal AKI?

Answer 1

Actual GFR reduced due to reduced renal blood flow
no cell damage- kidneys work hard to restore blood flow- reabsorb salt and water- ADH and aldosterone released
responds to fluid resuscitation

Question 2

what is the effect of being hypertensive on GFR when mean arterial pressure drops?

Answer 2

autoregulation of the kidneys will cause maximal dilation of arterioles in order to maintain perfusion but in hypertensive pt the MAP they can withstand is higher than normal, below this level GFR falls rapidly

Question 3

what happens in normal autoregulation to maintain GFR?

Answer 3

intrarenal prostacyclin increased- vasodilate afferent arteriole
circulating vasocontrictors increased- vasoconstrict efferent arteriole

Question 4

as GFR cannot be directly measured and you rely on waste products to calculate why does this make AKI difficult to diagnose?

Answer 4

following AKI- actual GFR falls instantly and then starts to recover
we measure Creatinine levels in the blood which do not peak showing injury until 5days after insult

Question 5

what affects do NSAIDS and ACE-I/ARB (angiotensin 2 receptor blocker) have on kidney autoregulation when trying to maintain perfussion to the kidneys?

Answer 5

NSAIDS block prostaglandins which vasodilate the afferent arteriole
ACE-I- block angiotensin 2 which vasoconstricts the efferent arteriole
- both of these are the mechanisms used to increase perfusion to the kidney in order to maintain GFR by increasing the pressure and allowing more blood into the glomerulus

Question 6

what diseases of the AA can lead to too little or too great a response to autoregulation stimuli?

Answer 6

BP, progressive kidney disease, DM

Question 7

what are the 2 major branches of causes of prerenal AKI?

Answer 7

1. reduced effective extracellular fluid volume

2. impaired renal autoregulation

Question 8

what comes under the causes of reduced effective extracellular fluid volume?

Answer 8

hypovolaemia- blood loss, fluid loss,
cardiac failure- LV dysfunction, valve disease, tamponarde
systemic vasodilation- sepsis, cirrhosis, anaphylaxis

Question 9

what comes under the causes of impaired renal autoregulation?

Answer 9

• preglomerular vasoconstriction- sepsis, hypercalcaemia, drugs- NSAIDS, hepatorenal syndrome
• postglomerular vasodilation- ACEi, AIIR antagonists