Disorders of calcium and sodium regulation Flashcards

Question

What causes euvolemia?

Answer 1

1) Adrenal failure (steroid deficiency) 2) Consequence of medications 3) SIADH

Answer 2

patients look fluid overloaded. Increase in sodium but a bigger increase in total body water, causing hyponatremia

Answer 3

Excess ADH or inappropriate ADH relative to plasma osmolality Often seen in the elderly

Answer 4

o Cancer: lung/lymphoma/leukaemia o Chest disease: pneumonia o CNS disorders: infections, injury o Drugs: opiates, thiazides, anti-convulsants, proton pump inhibitors, anti-depressants

Answer 5

1) Hyponatraemia with inappropriate low plasma osmolality 2) Urine osmolality > plasma osmolality (urine is being concentrated) 3) Urine sodium > 20 mmol/l (inappropriate sodium excretion) 4) Absence of adrenal, thyroid, pituitary or renal insufficiency 5) No recent use of diuretic agents

Answer 6

When the serum [Na] is low, water moves into cells to increase plasma osmolality, causing cell swelling The brain is encased by the skull, so there is little room for swelling Cerebral oedema can result

Answer 7

o Water rushes into the brain to try and increase the plasma osmolality o Can cause seizures and even death o Plasma dilution decreases serum osmolality, resulting in a higher osmolality in the brain compared to the serum. o This creates an abnormal pressure gradient and movement of water into the brain, which can cause progressive cerebral oedema, resulting in a spectrum of signs and symptoms from headache and ataxia to seizures and coma.

Answer 8

water leaves the brain to bring the osmolality back down, and can cause osmotic demyelination (due to brain adapting & minimising ill effects)

Answer 9

Patients who have ran the marathon

Answer 10

neurological disorder caused by severe damage to the myelin sheath of nerve cells in the pons

Answer 11

overly rapid correction of hyponatremia

Answer 12

with chronic hyponatremia, the brain compensates by decreasing the levels of osmolytes within the cells, so that they can remain relatively isotonic with their surroundings and not absorb too much fluid.

Answer 13

the cells increase their intracellular osmolytes so as not to lose too much fluid to the extracellular space.

Answer 14

```  Often asymptomatic  Mild confusion  Gait instability  Marked confusion  Drowsiness  Seizures ``` * symptoms worsen as plasma sodium falls

Answer 15

(Unconscious or seizures) - unusual o Give infusion of hypertonic (3%) saline o Can increase quickly

Answer 16

o Try to establish cause (might be easily reversible, e.g. stopping omeprazole) and treat underlying cause o Usually fluid restriction is correct management o Increase slowly o 2nd line treatment is controversial  Can consider AVPR2 antagonists (‘vaptans’), very occasionally used

Answer 17

 Most usually due to water loss (‘dehydration’) and inability to access water

Answer 18

Main causes: o Insensible/sweat losses (severe burns/sepsis) o GI losses o Diabetes Insipidus o Osmotic diuresis due to hyperglycaemia (HHS/DKA) (Seen a lot in patients with dementia => no intact thirst mechanisms)

Answer 19

```  Treat underlying cause!  Estimate total body water deficit if possible to guide fluid regimen  Avoid overly rapid correction o Aim for ↓ 10 mmol/l in 24 hours o Concern is cerebral oedema  Use IV 5% dextrose ```

Answer 20

- GI tract - Bones - Kidney

Answer 21

Absorbed throughout small intestine from dietary sources (only approx 10% of ingested calcium is absorbed) o Vitamin D dependent process

Answer 22

Calcium reservoir | o Regulates plasma Ca via action of osteoblasts and osteoclasts

Answer 23

Free Ca filtered by glomerulus | o 97-99% is reabsorbed

Answer 24

o Increases GI absorption o Increases bone resorption o Increased renal reabsorption

Answer 25

PTH secreted by the parathyroid glands – normally located on posterior surface of thyroid gland

Answer 26

high calcium (Ca2+) level in the blood serum. The normal range is 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L) with levels greater than 2.6 mmol/L defined as hypercalcemia.

Answer 27

 Moans = depression/slowed down  Bones = bone pain, muscle weakness, osteopaenia  Stones = predisposed to nephrocalcinosis/nephrolithiasis  Abdominal Groans = vomiting, constipation  Also increased thirst and polyuria  can cause nephrogenic diabetes

Answer 28

ECG changes:  Can predispose to dysrhythmia  Shortened QTc interval  Bradycardia

Answer 29

- primary hyperparathyroid | - malignancy

Answer 30

o Usually a single parathyroid adenoma o One PTH gland becomes overactive, churning out PTH o Increased bone resorption and GI absorption

Answer 31

o Usually due to secretion of PTH-related peptide - secreted by a lot of cancers. Acts at PTH receptor o Breast, lung and multiple myeloma are commonest tumours o Also, seen in bone metastases due to direct osteolysis and release of calcium from bones

Answer 32

Measure PTH: o If ↓ then malignancy is likely (PTHrP has negative feedback effect on PTH production) o If ‘normal’ or ↑ then primary hyperparathyroidism

Answer 33

- rehydration - bisphosphonate therapy - calcitonin - parathyroidectomy

Answer 34

o Mild < 3mmol/l o Moderate 3-3.5 mmol/l o Severe > 3.5 mmol/l

Answer 35

 Patients are often hypovolaemic - Hypercalcaemia can cause AKI - Hypovolemia exacerbates hypercalcemia by impairing the renal clearance of calcium  Isotonic (0.9%) saline infusion corrects hypovolaemia – be careful of fluid overload  Will not normalise calcium unless only mildly elevated

Answer 36

 Inhibit bone resorption (and therefore calcium release from bones) by inhibiting osteoclasts o Commonly used to treat osteoporosis  Agents of choice for treating hypercalcaemia of malignancy (underlying cause may be incurable) o Zolendronic acid is most commonly used  Delayed effect, maximal at 2-4 days after treatment

Answer 37

``` o Has opposite effects to PTH o Increases renal calcium excretion o Decreases bone resorption (increases osteoblast activity) o Only effective for 48 hours o Given as subcutaneous injection ```

Answer 38

inhibit vitamin d production

Answer 39

o Primary hyperparathyroidism o Only if resistant to treatment o Rarely indicated urgently, usually done as elective surgery

Answer 40

o Dysrhythmia | o Hypotension

Answer 41

hyperventilation causes very mild and transient hypocalcaemia due to alkalosis =>tingling in hands Alkalemia induces tetany due to a decrease in ionized calcium, whereas acidemia is protective.

Answer 42

Tetany, as calcium is important as a neurotransmitter

Answer 43

Increased neuromuscular excitability

Answer 44

Low ionized calcium levels in the extracellular fluid increase the permeability of neuronal membranes to sodium ion, causing a progressive depolarization, which increases the possibility of action potential If the plasma Ca 2+ decreases to less than 50% of the normal value, action potentials may be spontaneously generated, causing contraction of peripheral skeletal muscles.

Answer 45

calcium ions interact with the exterior surface of sodium channels in the plasma membrane ``` When calcium ions are absent, the voltage level required to open voltage gated sodium channels is significantly altered (less excitation is required). ```

Answer 46

Peri-oral numbness, muscle cramps, tingling of hands/feet If severe: carpopedal spasm, laryngospasm, seizures

Answer 47

- Low PTH - High measured PTH - Drugs - Hypomagnesaemia

Answer 48

- after parathyroid surgery | - autoimmune hypoparathyroidism

Answer 49

o Vitamin D deficiency => PTH level increases to try and increase vitamin D levels, but this may be insufficient to prevent hypocalcaemia o Chronic renal failure => reduced ability to hydroxylate vitamin D o Loss of Calcium => unusual but possible

Answer 50

o often results from PPIs and is required for PTH to cause effects o correcting calcium without correcting magnesium will not solve underlying problem o Leads to PTH resistance

Answer 51

```  Intravenous calcium replacement if tetany or cardiac manifestations  May also need magnesium infusion  Chronic management: o Vitamin D (D2 or D3) o Oral calcium salts  Treat underlying cause ```

Disorders of calcium and sodium regulation Flashcards

(75 cards)