Biochemistry Flashcards
1
Q
Osmolar gap
- Calculated by
- Normal
- What might a large osmolar gap indicate
A
- 2[Na + K] + Urea + Glucose
- <10
- Presence of high levels of e.g. ethanol
2
Q
Compensation - level at which this is definitely occurring
- CO2 in metabolic acidosis
- CO2 in metabolic alkalosis
- HCO3 in respiratory acidosis
- HCO3 in respiratory alkalosis
A
- <4.5 kPa
- > 6.0 kPa
- > 30 mmol/L
- <24 mmol/L
3
Q
Acute respiratory acidosis results
A
CO2 high
pH low
4
Q
Chronic resp acidosis with compensation results
A
CO2 high
pH normal/ near normal
HCO3 high
5
Q
Hypoventilation
- Causes (3 types)
- Typical features (3)
- Blood tests (5)
- Other tests (2)
- Treatment (2)
A
- Neuromuscular disease (e.g. GBS, myasthaenia gravis), lung disease (e.g. COPD), decreased central respiratory drive (e.g. trauma, brainstem disease, encephalitis)
- Confusion, peripheral vasodilation (from raised ICP), coma
- FBC, U+E, TSH, ABG, toxicology
- CXR, lung function
- Treat cause, consider respiratory support
6
Q
Acute respiratory alkalosis - presentation
A
CO2 low
pH high
7
Q
Chronic respiratory alkalosis w/ compensation -presentation
A
CO2 low
pH normal / near to normal
HCO3 low
8
Q
Hyperventilation
- Causes (CNS, lung, hypoxia, drugs, endocrine, other)
- Clinical features
- Blood tests
A
- CNS (meningitis / stroke / anxiety / trauma), lung (pneumothorax, pneumonia, pulmonary oedema, PE), hypoxia (severe anaemia), drugs (salicyclates, catecholamines) endocrine (pregnancy, hyperthyroidism), other (sepsis, liver / heart failure / mechanical ventilation)
- Hand numbness, tingling round mouth, light headed, tachycardic
- ABG, U+E, TSH
9
Q
Anion gap
- Calculated using
- Purpose
Anion gap range:
- Low
- Normal
- High
- High anion gap - significance
- High anion gap - examples
- Normal anion gap - significance
- Normal anion gap - examples
- Normal anion gap - aka
A
- [Na + K] - [Cl - HCO3]
- To investigate if a metabolic acidosis is due to exogenous or endogenous acid
- Low: <12 mmol/L
- Normal: 12-16 mmol/L
- High: >16 mmol/L
- Metabolic acidosis from exogenous acid build up
- Lactate (type a) shock, sepsis, hypoxia, type b) metformin), ketones (DKA, alcohol), acid poisoning (methanol, salicyclates e.g. aspirin), urate (renal failure)
- Means metabolic acidosis from endogenous acid build up or bicarb loss e.g. GI / renal loss
- GI HCO3 loss (diarrhoea, fistula), renal tubular acidosis, hyperchloraemia, Addison’s disease (high K+)
- Hyperchloraemic metabolic acidosis
10
Q
Metabolic acidosis
- Cause (3 broad types)
- Blood tests
- Treatment in severe cases
A
- Increased H+ (Lactic acidosis, ketoacidosis, some drugs), failure to excrete H+ (renal), bicarb loss (GI or renal loss)
- FBC, U+E, ABG, lactate, serum osmolality, glucose
Loss of bicarb - GI loss or renal loss - Bicarb replacement
11
Q
Metabolic alkalosis
- Cause (3 broad types)
- Clinical features
- Blood tests
- Management (3)
A
- H+ loss (vomiting, diuretic therapy), HCO3 build up (ingestion), endocrine imbalance (cushing’s, hyperaldosteronism, fludrocortisone)
- Hypoventilation (compensation), hypocalcaemia symptoms (numbness/tingling of lips/peripheries, muscle cramps, seizures, bradycardia)
- ABG, U+Es, renin, aldosterone, cortisol
- Treat cause, replace fluid, replace electrolytes
12
Q
Hyponatraemia - causes
- Tests (4)
- Hypovolaemic - usual urine osmolality
- Urinary Na >30 (from kidneys - causes)
- Urinary Na <30 (from elsewhere)
Euvolaemic (Na normal, H20 gained)
- Urinary Na >30, urinary osmolality >100 (from kidneys)
- Low urinary Na/Osmolality (from elsewhere)
- Hypervolaemic/Oedematous - urine osmolality + Na
- Causes
- Management
A
- Assess hydration status, plasma + urinary osmolality, urinary Na+
- Urine osmolality >400
- Thiazide/loop diuretics, Addison’s, osmotic diuresis
- Extra-renal loss - D+V, burns, sweating
- SIADH (urine osmolality > 500), hypothyroid
- H2O intoxication
- Urine osmolality >100, Na <30
- Water excess - CCF, low albumin (cirrhosis / nephrotic syndrome), IV dextrose
- Treat cause, sodium correction (saline if hypo/Eu, fluid restrict if oedematous)
13
Q
Hypernatraemia
- Tests
- Causes - euvolaemic
- Hypovolaemic - producing small concentrated urine
- Not producing small amounts concentrated urine (2)
- DI - osmolalities
- Management - general
- If euvolaemic
- If hypovolaemic
A
- Hydration status, osmolality (urine/serum), fluid deprivation (DI)
- Iatrogenic from lots of crystalloid, Na+ drugs
- Normal response - dehydration, D+V, burns
- Abnormal response - osmotic diuresis (DKA), DI
- Plasma high, urine low
- Treat cause, sodium correction
- Dextrose
- Saline
14
Q
Hypokalaemia
- Causes - increased renal excretion
- Intestinal K+ loss
- Increased cellular uptake (3)
- Signs (2)
- ECG changes
- Management - if K+ >2.5
- If K+ <2.5
A
- Diuretics, endocrine e.g. Cushing/Conn, RTA, low Mg2+
- D+V
- Salbutamol, insulin, alkalosis
- Muscle weakness, hypotonia
- U wave, small/absent T, long QT, ST depression
- Sando K tablets
- KCl in 0.9% NaCl over 6 hours
15
Q
Hyperkalaemia
- Causes - less excretion
- Excess K+ load (2)
- Increased cellular release (2)
- Signs
- ECG changes
- Management
A
- AKI, CKD, Addison’s, NSAIDs, spironolactone, ACE-i
- Iatrogenic, blood transfusion
- Acidosis, tissue breakdown e.g. rhabdo/haemolysis
- Generalised muscle weakness, flaccid paralysis + paraesthesia in hands/feet, lethargy, confusion, palpitations
- Absent P, long PR, broad QRS, tall tented T
- Calcium gluconate 10 10 (if ECG changes / K+ >6.5), Actrapid Insulin Dextrose, Salbutamol Nebulisers