Week 9: Biochemical Tests 1 Flashcards
Includes: Sodium (Hyper/hyponatraemia) Potassium (Hyper/hypokalaemia) Chloride Bicarbonate Urea Creatinine
What is the reference range for sodium?
135-145mmol/L
What is the definition of hypernatraemia?
Plasma sodium concentration of > 145mmol/L.
What are the general causes of hypernatraemia? (2)
- Water Depletion:
- Loss of water to sodium
excess. - Decreased fluid intake.
- Loss of water to sodium
- Increased sodium intake / water excess retention:
- Mineralcorticoid excess
- Medication
- Renal Failure
What are the signs and symptoms of hypernatraemia? (8)
Dry Skin
Postural Hypotension
Oliguria (little urine production)
Thirst
Confusion
Drowsiness
Lethargy
Extreme cases - coma (>155mmol/L)
Give examples of drugs that can cause hypernatraemia. (7)
Corticosteroids
NSAIDs
Laxatives
Lithium
Injectables
Soluble prep. e.g. paracetamol, co-codamol
Antibiotics e.g. gentamycin, rifampicin
Explain the management process for hypernatraemia. (2)
- Identify + treat underlying cause (e.g. medicines should be changed to an alternative if it has recently been introduced)
- Replace body water:
Orally (Mild)
I.V. Dextrose 5% (Moderate/Severe)
What are the severity ranges for hypernatraemia? (3)
Mild: 146-149mmol/L
Moderate: 150-169mmol/L
Severe: >170mmol/L
How should IV dextrose 5% be administered? (1)
It should be given slowly at a rate of 12mmol over 24 hours to reduce the risk of cerebral oedema.
What monitoring is considered for altered sodium levels? (3)
Urine output
Weight
Fluid status
What is the definition of hyponatraemia?
Plasma sodium conc. <135mol/L.
What are the severity ranges for hyponatraemia? (3)
Mild: 130-135mmol/L
Moderate: 121-129mmol/L
Severe: <120mmol/L
What are the signs and symptoms for mild/moderate hyponatraemia? (6)
Headaches
Nausea
Fatigue
Cramps
Muscle Weakness
Confusion
What are the signs and symptoms of severe hyponatraemia? (3)
Seizures
Coma
Respiratory Arrest
What factors cause hyponatraemia? (2)
Over hydration +/or Low sodium intake
What are the causes of hyponatraemia? (8)
Medications
Mineralcorticoid deficiency
Water/fluid excess
Abnormal losses of sodium
Alcohol excess
Severe burns
Malnutrition
Blood sample dilution by IV fluids.
Give e.g. of drugs that can can cause hyponatraemia. (6)
- Diuretics:
- Thiazide: Bendroflumethiazide, Indapamide
- Loop: Furosemide
- Antidepressants:
- SSRI: Fluoxetine, Paroxetine, Citalopram
- TCA: Amitriptyline
- Anticonvulsants: Carbamazepine
- ACEi’s: Ramipril, Lisinopril, Enalapril.
- Sulphonylureas: Gliclazide, Tolbutamide
- PPI’s: Omeprazole, Pantoprazole.
Explain the management process for hyponatraemia.
- Identify and correct underlying cause e.g. increase salt intake/fluid restriction.
- If needed:
Mild-Moderate: Slow sodium, 4-8 tablets (2.4-4.8g) OR
Demeclocycline 900-1200mg daily in divided doses.
Severe: I/V NaCl
At what rate should IV NaCl be administered?
It should be administered slowly to reduce the risk of osmotic demyelination.
What are the severity ranges for hyperkalaemia?
Mild: 5.5-5.9mmol/L
Moderate: 6.0-6.4mmol/L
Severe: ≥ 6.5mmol/L
What are the causes for hyperkalaemia? (10)
Medication
Renal (AKI/CKD/Rhabdomyolysis/Hypoaldosteronism)
Advanced CCF
Acidosis
DKA
Severe Tissue Damage
Hormonal Effects
Fragile Blood Cells
Diet
What is pseudohyperkalaemia?
An artificial rise in K+ levels due to an underlying cause.
What can cause pseudohyperkalaemia?
Delay in sample reaching lab
Contamination
Haemolysis of sample
Drip arm
What are the signs and symptoms of hyperkalaemia? (6)
Fatigue
Muscle Weakness
Abnormal Cardiac Conduction:
- Chest pain + palpitations
- ECG changes
- Cardiac Arrest (severe)
What signs and symptoms of hyperkalaemia would be considered as a medical emergency? (3)
1 or more:
Severe hyperkalaemia (> 6.5mmol/L)
ECG changes
Chest pain + palpitations
Explain the management process for hyperkalaemia. (5)
- Assess patient: ABCDE
- Identify cause/stop potentially offending drugs immediately.
- Rule out pseudohyperkalaemia.
- Ensure adequate hydration.
- Consider severity: Severe/ECG changes (Medical emergency)
Explain how mild/moderate hyperkalaemia is managed in community. (2)
- Mild (5.5-5.9mmol/L):
- Correct underlying cause, repeat blood test
- Medication review and dietary changes.
- Moderate (6-6.4mmol/L):
- Carry out an ECG
- Assess course of action based on results
- No high-risk factors, review patient.
- Carry out an ECG
Explain when hospital referral is considered for hyperkalaemia. (3)
> 6.5mmol/L
Acute ECG changes and > 5.5mmol/L
Rapid rise
Outline the 5 step approach to managing hyperkalaemia in hospitals.
Protect heart
Shift K+ into cells
Remove K+ from body
Monitoring
Prevention
Explain the process of protecting the heart in hyperkalaemic patients.
If ECG changes are present:
1. 30ml of 10% Ca Gluconate IV OR 10ml of 10% Ca chloride IV.
Antagonises cardiac excitability.
What is the interaction between digoxin and calcium gluconate?
It can increase digoxin toxicity causing arrhythmias.
How should calcium gluconate be administered? (2)
20-30 mins intervals at a slow rate via infusion.
Then it’s reconstituted to 100ml of glucose.
If a patient has high calcium levels, what medications should not be given if they experience hyperkalaemia? (2)
Calcium gluconate/chloride
Explain the process of shifting potassium into cells. (4)
- Insulin-glucose infusion:
- 10 units soluble insulin in 250ml dextrose 10%
- 10-20mg salbutamol nebuliser (IHD)
- Doesn’t reduce total body K+ = will start to leak back into extracellular space (2-6 hrs)
- Shift into cells TEMPORARILY!
Explain the process of removing potassium. (4)
Potassium exchange polymers:
- Anion exchange resin
- Potassium binders
Dialysis
Give example of an anion exchange resin that treats hyperkalaemia.
Calcium resonium 15g TDS
Give e.g. of potassium binders that treats hyperkalaemia. (2)
Patiromer calcium (8.4g OD)
Lokelma (sodium zirconium cyclosilicate)
Counsel a patient on using Patiromer calcium (3)
It’s taken orally - 8.4g OD adjust dose acc.
Onset of action = 4-7 hrs
Can cause GI irritation and reduced Mg levels.
Counsel a patient on Lokelma (sodium zirconium cyclosilicate) (4)
Orally administered (10g up to TDS for up to 72 hrs)
45ml H20
Onset of action = 1hr
Common s/e = fluid imbalance/retention, oedema.
When would dialysis be used as a treatment option to remove K+ levels? (3)
Used as 3rd line treatment if Anion exchange resin and potassium binders are ineffective.
Need to contact with critical care team and renal consultant/registrar for additional advice.
What monitoring is considered for hyperkalaemic patients? (4)
- Continuous cardiac monitoring where ECG features are present.
- K+ levels every 2-4 hrs.
- Blood glucose levels
- Baseline, 15,30,60,90,120 minutes and up to 6hrs post dose.
What are the treatment aims for hyperkalaemia? (4)
Improved patient health
Optimal tx and return home
Optimise and ongoing monitoring
Advise sick day rules (withold meds temporarily) - prevents hyperkalaemia during acute illness (sepsis to AKI)
Explain the process of preventing hyperkalaemia. (2)
Stop nephrotoxic medications and drugs that cause hyperkalaemia.
What are the severity ranges for hypokalaemia?
Mild <3.5mmol/L
Moderate 2.5-3mmol/L
Severe <2.5mmol/L
Give e.g. of drugs that cause hyperkalaemia. (7)
ACEi
K+ sparing diuretics
ARBs
K+ supplements
Trimethoprim (CKD)
NSAIDs
K+ containing laxatives
What are the causes of hypokalaemia? (4)
Medication
Decreased K+ intake
Abnormal losses = D+V, Ileostomy
Acid-base disturbances
What are the signs and symptoms of hypokalaemia? (6)
Hypotonia (reduce muscle tone)
Cardiac Arrhythmias
Muscle Weakness
Fatigue
Confusion
Paralytic Ileus
Give e.g. of drugs that cause hypokalaemia (5)
Salbutamol (high doses)
Diuretics (Loop/Thiazide)
Insulin
Steroids
Chronic laxative abuse
Explain the management process for mild/moderate hypokalamia. (3)
- Sando K: 1-2 tablets TDS
- Kay-Cee-L: 10-20ml TDS
- Slow K: Avoid
Explain the management process for severe hypokalaemia. (1)
IV replacement (w/ continuous cardiac monitoring - depending on K+ conc.)
What does the NPSA state about administering K+ permanganate?
It can increase the risk of of death or serious harm to the patient if taken orally.
What is the interaction between digoxin and hypokalaemia? (2)
This increases the risk of digoxin toxicity.
Digoxin competes with K+ ions at binding sites hence, lowers K+ levels predisposing to toxicity.
What is the reference range for Chloride?
95-105mmol/L
What are the causes of increased Cl- levels? (2)
- Excess ingestion
- Dehydration
What are the causes for reduced Cl- levels?
- Vomiting
- Diarrhoea
- Diuresis
- Dehydration
What is the reference range for Bicarbonate?
24-30mmol/L
What are the causes for increased bicarbonate levels? (5)
- Excess antacids
- Thiazide/loop diuretics
- Metabolic alkalosis
- Hypokalaemia
- Vomiting
What are the causes for decreased bicarbonate levels? (5)
- Diarrhoea
- Renal Failure
- Diabetes Mellitus
- Metabolic Acidosis
- Respiratory Alkalosis
What is the main symptom indicating high bicarbonate levels?
Vomiting
What are the signs and symptoms for reduced bicarbonate? (3)
Headache
Drowsiness
Coma (severe acidosis)
What is urea? (3)
End product of protein/muscle metabolism.
Excreted from kidneys in unchanged form.
If kidney filtration is impaired, serum creatinine levels will rise.
What are the causes for high urea levels?
- Renal Failure
- Sepsis
- Urinary Tract Obstruction (UTO)
- CCF
- Dehydration
- GI bleed
What are the causes for low urea levels? (5)
- Pregnancy
- Low protein intake
- Chronic Liver Disease
- Overhydration
- Starvation
Explain what process of creatinine undergoes. (1)
Creatinine undergoes complete glomerular filtration and its clearance is a marker of GFR.
What is GFR? (2)
Glomerular Filtration Rate:
- Rate at which kidney filters and it varies with age + gender.
- Levels of creatinine will correlate with lean body mass.
What are the causes for increased creatinine levels? (3)
- Dehydration
- Renal Failure
- Urinary Tract Obstruction
What are the causes for reduced creatinine levels? (2)
- Pregnancy
- Chronic Muscle Wasting
