Systems Pathology: disorders of acid base balance

Question 0

Acid homeostasis

Answer 0

ECF [H+] 35-45 pH 7.45
Temporary measure-> nothing has been removed
Co2+h2oh2co3 H+ +hco3
Co2 excreted/retained by lungs
Hco3 retainined, generated or excreted by kidneys

Question 1

Acid production and excretion

Answer 1

The body is a net acid producer
Carbonic acid-> oxidation of carbs and fats to co2 and water
Lactic acid and ketoacidosis-> partial oxidation of carbs and fats, non volatile- excreted by kidneys
Sulphuric acid and phosphoric acid-> metabolism of sulphur and phosphate, non volatile so excreted by kidneys

Question 2

Consequences of acidosis

Answer 2

Hyperkalaemia 
Hyperventilation 
Depression of consciousness
Coma
Death

Question 3

Consequences of alkalosis

Answer 3

Hypokalaemia

Hypocalcaemia -> muscle cramps, tetany, parathesia

Question 4

Respiratory acidosis

Answer 4

Co2 retention -> low pH/normal-> hco3 high normal/high
Causes:
COPD
Suppression of resp system
Upper airway obstruction
Resp muscle disease
Compensation-> metabolic-> renal hco3 generation and H excretion-> high hco3

Question 5

Respiratory alkalosis

Answer 5

Low CO2-> normal/high pH-> low/normal hco3
Hyperventilation->
Anxiety
Cerebral disease
Pulmonary embolus
Hypoxia
Compensation-> metabolic-> renal hco3 excretion

Question 6

Metabolic acidosis

Answer 6

Low hco3 -> low pH->pco2 normal/low 
Increased acid generation-> lactic, keto toxins
Impaired acid excretion-> renal failure
Bicarbonate loss-> diarrhoea 
Compensation-> resp-> hyperventilation 
-> kidney-> hco3 production

Question 7

Plasma anion gap

Answer 7

One negative charge balances one positive charge
Na and K provide more than 90% of plasma cation
Cl and hco3 80% of plasma anions
Anion gap= (Na+K) - (hco3+Cl)
Normally 14-20

Question 8

Metabolic acidosis high anion gap

Answer 8

Acute or chronic renal failure
Ketosis
Lactic acidosis
Intoxication
Renal tubular acidosis-> impaired hco3 production
Acetazolamide-> inhibits CD in tubules-> impaired hco3 formation
GI disease

Question 9

Metabolic alkalosis

Answer 9

High hco3-> high pH -> pco2 raised 
Iatrogenic-> base administration, diruetics 
Loss of acid from stomach
Hyperaldosteronism 
Compensation-> resp-> hypo ventilation

Question 10

Primary and compensatory changes summary

Answer 10

Metabolic acidosis-> low pH, low pco2, low hco3
Metabolic alkalosis-> high, high, high
Resp acidosis-> low, high, high
Resp alkalosis-> high, low, low

Question 11

Bases excess

Answer 11

The amount of H+ ions that would be required to return the pH to normal
Mirrors hco3 
Normally +\- 2
>3 metabolic alkalosis
<-3 acidosis