Acid-Base Abnormalities

Question 1

Normal pH range?

Answer 1

7.35-7.45

Question 2

Metabolic acidosis + Resp compensation is (normal anion gap)

Answer 2

HARD-ASS
Hyperalimentation
Addison’s disease
Renal tubular Necrosis
Diarrhoea (may also give hypokalaemia)
Acetazolamide
Sprionolactone
Saline infusion

Question 3

Anion gap equation

Answer 3

AG= [K+] + [Na+] - [Cl-] - [HCO3-]
Normal range: 10-18 mmol/L

Question 4

Metabolic acidosis with Resp Comp (Elevated anion gap)

Answer 4

Lactate: shock, sepsis, hypoxia
Ketones: diabetic ketoacidosis, alcohol
Urate: renal failure
Acid poisoning: salicylates, methanol

Question 5

Resp acidosis

Answer 5

COPD
Decompensation in life threatening asthma/ pulmonary oedema
Neuromuscular disease
Obesity hypoventilation syndrome
Drugs: benzodiazepines/ opioid overdose

Question 6

Respiratory alkalosis

Answer 6

anxiety leading to hyperventilation
pulmonary embolism
salicylate poisoning*
CNS disorders: stroke, subarachnoid haemorrhage, encephalitis
altitude
pregnancy

*salicylate overdose leads to a mixed respiratory alkalosis and metabolic acidosis. Early stimulation of the respiratory centre leads to a respiratory alkalosis whilst later the direct acid effects of salicylates (combined with acute renal failure) may lead to an acidosis

Question 7

Metabolic alkalosis

Answer 7

Metabolic alkalosis
Metabolic alkalosis may be caused by a loss of hydrogen ions or a gain of bicarbonate. It is due mainly to problems of the kidney or gastrointestinal tract

Causes
vomiting / aspiration
(e.g. peptic ulcer leading to pyloric stenos, nasogastric suction)
vomiting may also lead to hypokalaemia
diuretics
hypokalaemia
primary hyperaldosteronism
Cushing’s syndrome
Bartter’s syndrome

Question 8

Bartter’s syndrome

Answer 8

Bartter syndrome is an autosomal recessive disorder of salt reabsorption resulting in extracellular fluid volume depletion with low/normal blood pressure. Thickening of ascending loop of Henle.

SX: periodic paralysis, lethargy, salt cravings, polydipsia and polyuria, nocturnal urination, stunted growth, vomiting

Dx: usually excess amniotic fluid (polyhydramnios) 24-30 wks gestation,

Tx: Na, Cl and K supplementation +- spironolactone

Question 10

Renal tubular acidosis

Answer 10

-Type 1 RTA (distal)
inability to generate acid urine (secrete H+) in distal tubule
causes hypokalaemia
causes include idiopathic, rheumatoid arthritis, SLE, Sjogren’s,
Complications inc. renal stones+ nephrocalcinosis

-Type 2 RTA (proximal)
decreased HCO3- reabsorption in proximal tubule
causes hypokalaemia
complications include osteomalacia
causes include idiopathic, as part of Fanconi syndrome, Wilson’s disease
Type 3 (mixed) Type 4 (hyperkalaemia)

Question 11

DKA management

Answer 11

0.9% sodium chloride and a fixed-rate insulin infusion at 0.1 units/kg/hr.

Diabetic ketoacidosis: once blood glucose is < 14 mmol/l an infusion of 10% dextrose should be started at 125 mls/hr in addition to the saline regime

Question 12

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