Lectures 4,5,6 Flashcards Preview

Year 2 (&1) NSF Urinary > Lectures 4,5,6 > Flashcards

Flashcards in Lectures 4,5,6 Deck (27)
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How to interpret a blood test when think issue with kidney

1. Look at pH scale first
a. Acidosis or alkalosis?
2. Acidosis
a. Look at PCO2 and bicarbonate, are what accept?
b. Low bicarbonate  metabolic reasons
c. Resp system compensation? CO2 will go down if R system trying to componsate


when acidosis when alkalosis?

acidosis - pH below 7.35
alkalosis pH < 7.45


What is the first line of defence when pH change

1. Look at pH scale first
a. Acidosis or alkalosis?
2. Acidosis
a. Look at PCO2 and bicarbonate, are what accept?
b. Low bicarbonate  metabolic reasons
c. Resp system compensation? CO2 will go down if R system trying to componsate


What is the second line of defence with acid abse balance

2. Respiratory control of A/B
a. Second line of defence
b. RAPID reflex, occurs constantly
c. Changing the rate and depth of breathing in order to change the amount of CO2 exhaled or retained
d. Takes care of 75% most pH disturbances
e. Low pH:
i. Chemoreceptors in carotid and aortic bodies detect change in protons
ii. Signal to resp control centre in hypothalamus
iii. RCC drives inc in rate and depth of breathing (occurs when running)
iv. This dec co2 = dec plasma H+
v. Responds to inc CO2 by detecting inc in protons


Limitation of respiratory control of acid and base balance

works great until issue with resp system
i. Doesn’t function if resp system and control centres not working e.g. pneumonia, resp obstruction
ii. Limited by availability of bicarbonate ions
iii. Can’t protect ECF from pH changes due to inc or depressed CO2 levels (can’t buffer itself


Kidney response to acid base balance

3. Kidney: final line of defence = slow but only way to get rid of acids other than carbonic acid
a. Excretion/ reabsorption of acidic ions (H+ and NH4+) or basic ions (HCO3- or OH-) = only way to eliminate acids other than carbonic acid.
b. By time filtrate got to distal convoluted tubule ALL filtered bicarbonate has been reabsorbed back in, most in proximal and little in LoH
c. Got rid of some H+ in proximal by unregulated secretion = protons that will bind to non bicarbonate buffers
d. 100% bicarbonate normally reabsorbed, proton secreted out, binds to bicarbonate and brings it bac into blood
i. INTERCALLATED cell PUMPS (2 types of cells found in D)
ii. ATPASE pumps on either apical or basolateral side
iii. Pump protons out into filtrate
iv. Mechanism requires ATP, protons to bind to non bicarbonate buffers, if on apical side = produce new bicarbonate = important
v. ALKALOSIS = opposite, pumps on basolateral side = protons pumped back into blood and secrete bicarbonate which is secreted into filtrate


How does the body respond to acid base balance

1. buffers
2. respiratory control
3. kidney - final line of defence


Respiratory acidosis

• Occurs when problem with resp tract
• Animal unable to ventilate normally
• CO2 accumulates e.g. hypoventilation
• Results in build up of protons leads to academia
• Blood pH drops below 7.35


Metabolic acidosis

• EITHER due to Decreased bicarbonate: (too much Bicarbonate out of system which is used as a buffer)
• = chronic diarrhoea. Particularly young animals with D
• KIDNEY not working = kid reabsorbs bicarbonate, if kidney action reduced bi = filtered out but not reabsorbed back. Or cells in distal tubule = not make new
• Conditions that give Increased acid load  diabetic animals = produce energy from fats = produce ketone bodies = like pouring acid into blood = diabetic ketoacidosis


pH less than 7.35 what shoudl you be thinking

1. ACIDOSIS... but what one?
2.  Resp system? Inc CO2
1. What is happening to CO2? Is it increased more than normal? Is pa CO” more than normal?
2. If resp is responsible then paCO2 raised as is the only way body can sort it out is to compensate metabolically
3. If p CO2 not increased, what else??
 Metabolic reasons? DECREASED bicarbonate
1. Diabetic ketoacidosis?
2. Kidney disease?
3. Diarrhoes?
4. Severe faecal loss
5. LOOk at bicarbonate: decreased (acid then bicarbonate is used p)


pH greater than 7.45 what should you be thinking?

1. Respiratory: dec Co2
 Hyperventilation = dec paCO2
 Metabolic compensation
2. Metabolic :
 Produce lot of HCL in gut, vomit lot – get rid of protons


Functions of kidney

• Fluid and electrolyte homeostasis
• Nitrogenous waste excretion
• Acid-base homeostasis - seminar
• Renin production
• Blood pressure homeostasis
• Synthesis of calcitriol (active vitamin D3 / 1,25-dihydroxycholecaliferol)
• Erythropoietin production


What deos urine specific gravity measure?

1. Measures solutes in urine  compare to water
2. Normally range for carnivores dogs/ cat = 1.025- 1.045 = quite concentrated!
3. Remember filtrate is hypoosmotic (more dilute when started) after LOH – probably 1.008 = much more dilute, concentrates in CD


Abnormal constituents of urine

1. Glucose
2. Blood
3. Protein
4. KEtones
5. Cells


What is azotaemia?

1. inc concentration nitrogenous waste products in blood


What happens if GFR is reduced/ stops

1. Azotaemia - inc conc nitrogenous waste products in blood - urea and creatinine
2. Inc conc K+ in blood, inc conc inorganis phosphate in blood


What does azotaemia tell us about GFR adn WHy

decreased GFR
2. either problem with kidney OR CV (reduced bp)
1. Filtered urea has too much time to be reabsorbed into system
2. If filtration rate slowed down the kidney is really rubbish at getting rid of urea and creatinine  high U and C


What would you expect with a dehydrated animal?

1. Expect urine specific gravity to inc – lot of ADH produced, lot of water reabsorbed = small concentrated urine
2. GFR in severe dehydration 
1. will dec
2. severe dehydration want to inc bp
3. D causes low blood vol, low blood pressure, so angiotensin released, causing vasoconstriction which drops GFR


Reduced kidney function due to...

kidney disease but can be CV also


How will we know if reduced kidney function is an issue with CV?

1. Reduced GFR, azotemic BUT animal kidney still functions so will still be able to concentrate urine!
2. E.g. hypovolaemia


How will we know if reduced kidney function is issue with kidney

1. Reduced GFR, results in azotaemia but it CAN’T concentrate urine!!!!
2. E.g. rupture of bladder


Clinical signs of animal with diseased kidneys

1. Inc conc nitrogenous waste products urea and creatinine  AZOTAEMIA
2. Inc conc inorganic phosphate
3. Decrease conc bicarbonate  metabolic acidosis because of this
4. Produce no urine at all or produce loads of urine that is not conc
5. Disturbance in conc of K+ - hyperkalaemia or hypo depending on disease


Why would hyperkalacemia occur if diseased kidney

1. If eating and taking in K+:
= Sudden reduced kidney function means less than normal excretion and K+ builds up in ECF e.g. stone or sudden poisoning
2. 1. Acidosis- e.g. metabolic as reduced kidney function
= The homeostasis of pH TRUMPS that of K+ and H+ is pumped into filtrate in exchange for K+


Why would hyPOkalacaemia occur?

1. remember no storage of K+
2. so animal stops eating = stops taking in K+ = stops secreting K+ in urine
3. HOWEVER with kidney disease can’t do this regulation well so more K+ lost in urine
4. Not eating and producing lots of urine  HYPOkalaemic


Clinical signs of blood potassium disturbance: all to do with membrane potential

1. Hyperkalaemia  Nerve and muscle initially more excitable but depolarised cells cant repolarise properly and thus become less excitable: bradycardia and cardiac arrhythmias, slow heart rate
2. Hypokalaemia  nerve and muscle cells hyperpolarised and less excitable = weak muscles, floppy, can’t stand


Signs of kideny disease

• Metabolic acidosis
• Low bicarbonate
• High phosphate
• Often high but sometimes low K+
• Often loads of dilute urine, can’t concentrate or stop producing urine altogether


Addisons disease

disease: primarily dogs
1. Hypoadrenocorticism
2. Dogs cannot produce enough aldosterone hormone from adrenal cortex
a. Aldosterone normally gets rid of K+ and causes reabsorption Na on principle cells
3. Clinical signs: due to high potassium and (critically) low sodium
a. Not enough aldosterone
b. Too much K+ retained = High K+
i. Hyperkalaemia – cardiac arrhythmias including bradycardia
c. Too much Na secreted = LOW Na = Hypovolaemia
i. Not enouch water in ECF = low blood volume, circularatory collapse, poor circulation
ii. – circulatory collapse
4. Diagnose:
a. Measure ration of Na+:K+ which should be <27:1
5. Acute cases are related but DIE quickly without treatment