Electrolytes: Calcium, Magnesium and Phosphate Flashcards
1
Q
What are the calcium compartments within the body?
A
- 99% in bones – calcium hydroxyapatite
- 0.99% - extracellular and interstitium
- 0.01% - intracellular
2
Q
How is Calcium transported within the body?
A
- Into cells using ligand gated channels and voltage gated channels
- Out of cell with NCX and ATP-Ca2+ pump
3
Q
What are the types of Extracellular Ca2+?
A
- Diffusible
- Non-diffusible: large and bold to albumin
4
Q
What are forms of Diffusible Calcium?
A
- Free ionised: blood coagulation, hormone secretion, contraction of muscle, neuron action potentials
- Calcium Oxalate: electrically neutral and not useful for cellular processes
5
Q
How does pH affect non-diffusible calcium?
A
- Acidosis increases protons bound to albumin which lead to increased free ionised Ca2+ extracellularly and less bound Ca2+ due to repelling of Ca2+ by postively charged albumin
- Alkalosis decreases protons bound to albumin which lead to decrease free ionised Ca2+ extracellularly and more bound Ca2+ due to attractive of negatively charged albumin
6
Q
How does concentration affect non-diffusible calcium?
A
- Hyperalbuminemia increases amount of protein bound Ca2+. Same free ionised Ca2+. Pseudohypercalcaemia
- Hypoalbuminaemia decrease amount of protein bound Ca2+. Same free ionised Ca2+. Pseudohypocalcaemia
7
Q
How is Calcium regulated?
A
- Changes in extracellular Ca2+ detected by calcium sensing receptor in parathyroid cells. Affect parathyroid hormone amount
- Affects the kidneys, bones and GI active vitamin D to maintain or lose Ca2+
8
Q
What are common causes of Hypercalcaemia?
A
- Primary Hyperparathyroidism: commonest cause in non-hospitalised patients o Osteoclastic bone resorption
- Malignancy: the commonest cause in hospitalised patients. This may be due to number of processes, including; bone metastases, myeloma, PTHrP from squamous cell lung cancer
9
Q
What are other causes of Hypercalcaemia?
A
- Drugs: thiazides, calcium containing antacids
- Vitamin D intoxication
- Sarcoidosis* (other granulomatous diseases as well)
- Acromegaly
- Thyrotoxicosis
- Milk-alkali syndrome
- Dehydration
- Addison’s disease
10
Q
What are symptoms of Hypercalcaemia?
A
-
(Bones, Stones, Groans and Psychic Moans)
- Slower or absent reflexes
- General muscle weakness
- Polyuria, Polydipsia
- Constipation
- Abdominal Pain
- Confusion
- Hallucinations
- Stupor, tiredness, weakness
11
Q
What are some clinical syndromes caused as a result of Hypercalcaemia?
A
- Calcium oxalate kidney stones due to hypercalciuria
- Anorexia
- Weight loss,
- Hypertension
- Ectopic Calcification
- Cardiac Arrest
12
Q
How is Hypercalcaemia investigated?
A
- High Ca2+ in blood
- Electrocardiogram showing Bradycardia and AV block. Osborne wave
- Checking levels of PTH, Vit D, Phosphorus, Magnesium, Albumin
- Malignancy: decreased albumin, decreased chloride, alkalosis, decreased potassium, increased phosphate,
- Increased PTH indicates hyperparathyroidism
13
Q
How is Hypercalcaemia managed?
A
- Rehydration with 3 to 4 litres of IV 0.9% N saline.
- Following this, bisphosphonates may be used.
- Loop Diuretics can be used to inhibit Ca2+ absorption
- Glucocorticoids to increase GI excretion
14
Q
What are common causes of Hypocalcaemia?
A
-
Hypoparathyroidism
- Surgical removal
- Autoimmune destruction
- Congenital problems e.g. DiGeorge syndrome
- Deficiency in magnesium
-
Low Vitamin D
- Deficient diet, Malabsorption
- Cirrhosis
- Lack of sunlight
- Chronic renal failure
- Kidney Failure
-
Tissue injury
- Burns
- Rhabdomyolysis
- Tumour lysis syndrome: Due to increase phosphate release which form insoluble compounds with free ionised Calcium leading to calcium phosphate formation
- Acute Pancreatitis
- Blood transfusions
15
Q
What are symptoms of Hypocalcaemia?
A
- Tetany (unstable Na+ channels)
- Muscle cramps
- Abdominal pain
- Periorbital tingling
- Seizure, Anxious
- Dermatitis
- Perioral Paraesthesia
16
Q
What are signs of Hypocalcaemia?
A
- Chvostek’s sign
- Trousseau’s sign
- Laryngospasm
- Cataract’s (chronic)
17
Q
How is Hypocalcaemia investigated?
A
- Low Ca2+ in blood
- Electrocardiogram showing prolonged ST and QT, Arrythmias such as Torsades de points and AF
- Checking levels of PTH, Vit D, Phosphorus, Magnesium, Albumin
18
Q
How is Hypocalcaemia managed?
A
- PO calcium in mild cases
- Calcium Gluconate
- Vitamin D supplementation
19
Q
What are the compartments of Phosphate within the body?
A
- 85% in bones: combined with calcium to form calcium hydroxyapatiei
- 1% extracellular
- 14% intracellular: phosphorylation, ATP formation, part of DNA and RNA backbone, Part of Cell-Signalling Pathways
20
Q
How are Phosphates regulated?
A
- Changes vary with calcium levels.
- PTH can cause break down calcium hydroxyapatite to release Calcium and Phosphate ion which bind together again and Travel to kidney.
- Phosphate usually reabsorbed by sodium-phosphate co-transporters but in presence of PTH, the reabsorption of phosphate is decreased and calcium increased.
- Phosphate lost in urine and Calcium kept in blood.
21
Q
What are common causes Hyperphosphataemia?
A
-
Acute/Chronic kidney disease
- Secondary hyperparathyroidism: Phosphate reabsorbed into blood due to impaired excretion
- Pseudohypoparathyroidism: receptors don’t repond to PTH
- Hypoparathyroidism
-
Excessive Intake
- Phosphate based laxative intake
-
Cell death
- Crush injury, tumour lysis syndrome, rhabdomyolysis
-
Metabolic
- Respiratory acidosis decrease glycolysis so less phosphate drawn into cells
- DKA reduces cell intake of phosphate
22
Q
What are symptoms of Hyperphophataeimia?
A
- Tetany
- Chvostek’s sign
- Trosseau’s sign
- Tingling around a mouth
- Seizures
- Bone pain
- Metastatic Calcification e.g. nephrocalcinosis
23
Q
What is the investigations and management of Hyperphospataemia?
A
Blood tests are the main investigation
Management
- Decrease intake
- Avoid certain foods (dairy, meat, soda)
- Medication (PO4)3- binders (sevelamer)
- Increase excretion
- Fluids
- Loop diuretics
24
Q
What are common causes of Hypophosphatemia?
A
- Primary Hyperparathyroidism
- Vitamin D deficiency
- Refeeding Syndrome
- Fanconi Syndrome
- Lack of Absorption through GI: alcohol, medications, antacids
- Starvation e.g. malnourishment, anorexia nervosa
- Respiratory alkalosis
25
Q
What are symptoms of Hypophosphataemia?
A
- Muscle weakness
- Osteomalacia
- Rhabdomyolysis
- Altered mental status
- Symptoms of hypercalcaemia
- Arrhythmias or cardiac arrest
- Red cell, White cell and Platelet dysfunction
26
Q
What are the investigations and management of Hypophospataemia?
A
Blood tests is the investigation
Management
- Intravenous or oral phosphate slowly (don’t give to patient who is hypercalcaemic or oliguric)
- Avoid refeeding syndrome in cases of malnutrition
27
Q
What are the compartments used in Magnesium?
A
- About 49.5% in cells
- About 49.5% in bones
- 1% in extracellular space
- Intravascular space (Blood vessels, lymphatic vessels),
- Interstitial space
- 20% bound to proteins and 80% filtered to kidneys
28
Q
What are causes of Hypermagnaseamia?
A
- Renal Failure
- Increased ingestion of magnesium: Magnesium hydroxide, infusions
- Tumour lysis syndrome
29
Q
What are some complications as a result of Hypermagnaseamia?
A
- Delayed muscle contraction
- Neuromuscular junction inhibition by inhibiting Ca2+ influx
- Hypocalcaemia (inhibition of PTH hormone release)
- Vasodilation
- Muscle weakness
- Diminished reflexes
- Respiratory failure
- Coma
- Cardiac Arrhythmias (electrical potential altered)
- Heart Block
- Asystole
30
Q
What is the investigation and management of Hypermagnasaemia?
A
Blood tests for U&Es
Management
- Reduce intake
- Calcium gluconate
- Furosemide to promote Mg2+ excretion
- Dialysis in severe cases
31
Q
What are common causes of Hypomagnesaemia?
A
- Renal Failure (less reabsorption)
- Loop Diuretics (less positively charged lumen)
- Genetic mutation in ion channels: Gitelman Syndrome
- Prolonged Malnutrition
- Low absorption in gut (PPI, Diarrhoea)
- Uncontrolled diabetes mellitus
- Hungry Bone syndrome (due to lack of thyroid hormone and PTH)
- Alcoholism
32
Q
What are symptoms of Hypomagnasaemia?
A
- Uncontrolled nerve stimulation
- Tetany
- Ataxia
- Trousseau sign
- Chvostek sign
- Seizures
- Convulsions
- Abnormal Heart rhythms
33
Q
What are complications as result of Hypomagnasaemia?
A
Associated with :
- Hypokalaemia
- Hypocalcaemia
34
Q
What is the investigation and management of Hypomagnasaemia?
A
Blood tests for U&Es
Management
- Oral supplementation
- MgSO4 administered IV or IM
