Causes of Acid-Base Disorders

Here are a list of causes of acid-base disorders with some handy mnemonics to help remember them:

1. METABOLIC ACIDOSIS

RAISED ANION GAP

ketones – DKA, alcohol, starvation

renal failure

lactate

toxins

useful mnemonic – CATMUDPILES

C – CN, CO

A – alcohols – ethanol

T – toluene

M – methanol, metformin

U – uraemia

D – DKA

P – paracetamol, paraldehyde

I – INH, Iron

L – lactate

E – ethylene glycol

S – salicylates, sepsis

 

NON ANION GAP 

useful mnemonic – USED CARP

U – ureteric fistula

S – small bowel fistula

E – extra Chloride

D – diarrhoea

C – carbonic anhydrase inhibitors

A – addison’s

R – RTA

P – pancreatic fistula

 

2. METABOLIC ALKALOSIS

useful mnemonic – CLEVER PD

C – contraction (dehydration)

L – liquorice (diuretic), laxative abuse

E – endocrine (Conn’s, Cushing’s)

V – vomiting, GI loss (villous adenoma)

E – excess alkali (antacids)

R – renal (Bartter’s), severe K depletion

P – post hypercapnia

D – diuretics

 

3. RESPIRATORY ALKALOSIS

Central causes

head injury

stroke

anxiety, pain, stress, voluntary

drugs – salicylates

pregnancy

Hypoxia

Hyperventilation

Pulmonary

PE

pneumonia

asthma

pulmonary oedema

Iatrogenic

mechanical ventilation

 

4. RESPIRATORY ACIDOSIS

Inadequate alveolar ventilation

Central – drugs, trauma, haemorrhage, tumour, spinal trauma, tetanus

Nerve / muscle – GBS, MGravis, muscle relaxants, toxins (organoPO4, snake venom), myopathies, diaphragm injury/ paralysis

Lung/ Chest wall – COPD, trauma (flail, contusion, haemothorax), pneumothorax, pulmonary oedema, ARDS, restrictive lung disease, aspiration

Airway – upper airway obstruction, laryngospasm, asthma (bronchospasm)

External – inadequate mechanical ventilation

CO2 overproduction

malignant hyperthermia

CO2 intake

iatrogenic – rebreathing CO2, addition of CO2 to inspired gas, laparoscopic surgery

 

5. RAISED A-a GRADIENT

VQ mismatch

shunt

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