Acid-Base - Ex 5 Flashcards
Three body buffers
- HCO3
- Proteins (Hgb 80%, plasma proteins 20%), primarily intracellular
- Phosphates
Renal regulation of acid-base balance (4)
- Resorb all HCO3
- Regenerate HCO3
- Regulated production of NH3
- combines with H+ to make NH4+ - Normally, minimal HCO3 is secreted
Acid-base evaluation - First…
Look at pH
increase = alkalosis
decrease = acidosis
Acid-base evaluation - Second…
Has metabolic or respiratory component or both changed in the SAME direction as pH?
inc CO2 –> acid change
dec CO2 –> alkaline change
inc HCO3 –> alkaline change
dec HCO3 –> acid change
Low pH
Low HCO3
Metabolic acidosis (at least)
High pH
Low pCO2
Respiratory alkalosis
Low pH
Low HCO3
High pCO2
mixed metabolic and respiratory acidosis
Acid-base evaluation - Third…
Look for compensatory change
Has metabolic or respiratory component changed in an OPPOSITE direction from pH?
Low pH
Low HCO3
Low pCO2
Metabolic acidosis with respiratory compensation
What happens quicker, resp or metabolic compensation?
Resp compensation happens quickly (hours)
Metabolic compensation happens slower (days)
If compensation is inadequate…
then there may be a problem in the compensatory organ
if compensation is too much… of falls short of the expected level
there might be a mixed disorder
Metabolic Acidosis
Loss of H and Cl rich fluid –> results in decreased HCO3
- Gastric vomiting - loss to outside
- Proximal GI obstruction - “loss” in stomach
- Displaced abomasum - “loss in abomasum, omasum, reticulum, rumen
- Sweating - horses
Paradoxic acuduria
Gastric vomiting
Prox GI obstruction
Displaced abomasum
Heavy sweating in horses
Dehydration with low Cl
Kidney reabsorbs Na and excretes H–> urine is acidic
Hypochloremia can lead to…
Alkalosis
Respiratory alkalosis - 2
Hyperventilation –> blowing off excess CO2
- Hypoxemia from any cause
- low O2 stimulates hyperventilation - Stimulation of resp center
- normal pO2
- CNS dz, gram-neg sepsis, fever
- pain or excitement
Respiratory Acidosis - 4
Decreased ventilation –> can’t blow off CO2
- Airway obstruction
- Resp center depression
- Pulmonary dz
- pneumonia, pulmonary edema, etc - Restrictive dz
- pneumonia, pleural effusion, etc
Respiratory acidosis - O2 levels
pO2 is always low in these animals
- unless on sup O2
CO2 diffuses easier than O2 –> if O2 diffusion impaired, so will CO2
Metabolic Acidosis - 2
- Addition of acid
- ketoacidosis
- lactic acidosis
- ethylene glycol
- renal failure (inc acid waste) - Loss of HCO3
- diarrhea
- Addison’s dz (aldosterone stimulates HCO3 and Na reabsorption and stimulates K and H secretion)
Titrational acidosis (metabolic)
Increased organic acids
- HCO3 titrates the additional acid and is used up
- AG will be increased
- aka High anion gap acidosis
Secretional acidosis (metabolic)
Loss of HCO3
- AG will be normal
AG calculation
UA - UC = (Na + K) - (HCO3 + CL)
High anion gap acidosis
Low HCO3
Normal Cl
Caused by excess acids: aka Titrational
- ketones
- lactic acid
- sulfates
- phosphates
- uremic acids
- ethylene glycol
- metabolites
Normal anion gap acidosis
Low HCO3
High Cl
Caused by: aka Secretional acidosis
- loss of HCO3 rich fluids
- leads to inc renal Cl reabsorption
Mixed acidosis/alkalosis
Low Cl
High AG
Normal to increased HCO3
Caused by:
- combined alkalosis and high AG acidosis
Ex:
- High GI obstruction and lactic acidosis
- renal failure and vomiting (common in cats)
