Nephrology - Acid base

Question 1

Normal anion gap metabolic acidosis

Answer 1

• ammonium chloride injection
• diarrhoea
• fistula
• acetazolamide
• Addison’s disease
• renal tubular acidosis
• ureterosigmoidostomy
• Carbonic anhydrase inhibitors (e.g., topiramate, acetazolamide)
• Chemotherapy (e.g, ifosfamide, cisplatin)
• Antibiotics (e.g., aminoglycosides, trimethoprim/sulfamethoxazole)
• Amphotericin B
• Lithium
• Pentamidine
• Rifampin
• Inhaled toluene

MCQs

Question 2

Raised anion gap metabolic acidosis

Answer 2

• renal failure
• hypoxia
• diabetic ketoacidosis
• alcohol poisoning
• shock
• salicylate poisoning

Question 3

Low Anion Gap (<6)

Answer 3

• Lab error
• Lithium tox
• Bromide tox
• Hypoalbuminemia
• Paraproteinemias
• Severe hypercalcemia/hypermagnesemia

Question 4

causes of combined respiratory and metabolic acidosis

Answer 4

• Acute cardiac failure.
• Severe exacerbation of obstructive airways disease and pre-renal failure from diuretics.
• Aspirin poisoning
• Severe pneumonia with renal failure due to septicaemia or interstitial nephritis (Legionnaire’s disease)
• Septicaemia from any cause complicated by ARDS
• Malaria complicated by pneumonia
• Acute renal failure and fluid overload
• Renal pulmonary syndromes: anti-GBM disease, Wegener’s granulomatosis, microscopic polyarteritis nodosa
• Acute massive pulmonary embolism
• Cardiac arrest (before ventilation)

Question 5

Metabolic alkalosis

Answer 5

• Bartter’s syndrome
• hypokalaemia
• carbenoxolone
• primary hyperaldosteronism
• congenital adrenal hyperplasia
• diuretics
• Cushing’s syndrome
• vomiting / aspiration
• liquorice

Question 6

Hypokalemia with alkalosis

Answer 6

• vomiting
• diuretics
• Cushing’s syndrome
• Conn’s syndrome (primary hyperaldosteronism)

Medstudy

• Reduction in effective arterial blood volume
  
  • Volume contraction: vomiting, NG suction, bleeding, or diuretics (thiazides and loops)
  • Renovascular disease: renal artery stenosis or fibromuscular dysplasia
  • 2° hyperaldosteronism: severe HF, cirrhosis, nephrotic syndrome
• 1° aldosteronism
• Renin-secreting tumor
• Cushing syndrome
• Liddle’s, Bartter’s, and Gitelman’s

Question 7

Hypokalemia with acidosis

Answer 7

• diarrhoea
• renal tubular acidosis
• acetazolamide
• partially treated diabetic ketoacidosis

Question 8

Causes of respiratory alkalosis

Answer 8

Due to stimulation of the central nervous system

• Anxiety
• Hypoxia
• Salicylate poisoning
• Encephalitis
• Brainstem injury

Due to pulmonary disease

• Asthma
• Pneumonia
• Lung fibrosis
• Pulmonary oedema
• Pulmonary embolus

Question 9

Causes of chloride-responsive
metabolic alkalosis

Answer 9

• Vomiting,
• nasogastric suction,
• postdiuretic use, and
• posthypercapnic states

Note: urine chloride concentrations less than 15 mEq/L

Question 10

Causes of chloride-resistant metabolic alkalosis

Answer 10

• mineralocorticoid excess,
• current diuretic administration,
• milk-alkali syndrome,
• Bartter syndrome, and
• severe hypokalemia

Note: urine chloride concentrations over 20 mEq/L.