Lectures 4,5,6 Flashcards
How to interpret a blood test when think issue with kidney
- Look at pH scale first
a. Acidosis or alkalosis? - 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
- Look at pH scale first
a. Acidosis or alkalosis? - 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
- 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
- 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
e. DISTAL TUBULE:
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
- buffers
- respiratory control
- 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
- ACIDOSIS… but what one?
- Resp system? Inc CO2
- What is happening to CO2? Is it increased more than normal? Is pa CO” more than normal?
- If resp is responsible then paCO2 raised as is the only way body can sort it out is to compensate metabolically
- If p CO2 not increased, what else??
Metabolic reasons? DECREASED bicarbonate - Diabetic ketoacidosis?
- Kidney disease?
- Diarrhoes?
- Severe faecal loss
- 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?
- Measures solutes in urine compare to water
- Normally range for carnivores dogs/ cat = 1.025- 1.045 = quite concentrated!
- Remember filtrate is hypoosmotic (more dilute when started) after LOH – probably 1.008 = much more dilute, concentrates in CD
Abnormal constituents of urine
- Glucose
- Blood
- Protein
- KEtones
- Cells
What is azotaemia?
- inc concentration nitrogenous waste products in blood