Sodium, Potassium, Calcium, and Fluids Flashcards Preview

Phase II: General Medicine Pt1 > Sodium, Potassium, Calcium, and Fluids > Flashcards

Flashcards in Sodium, Potassium, Calcium, and Fluids Deck (50):
1

What is the normal concentration of sodium in extra- and intracellular space?

Extracellular Na: 144 mmol/L
Intracellular Na: 10 mmol/L

2

What is the normal concentration of potassium in the extra- and intracellular space?

Extracellular K: 4 mmol/L
Intracellular K: 160 mmol/L

3

What is the normal concentration of calcium in the extra- and intracellular space?

Extracellular Ca: 1.5 mmol/L
Intracellular Ca: 100 nmol/L

4

What is the total water volume of the average 70kg male?

42L

5

What proportion of fluid is extracellular and intracellular?

Extracellular: 1/3 (14L)
Intracellular 2/3 (28L)

6

How can extracellular fluid be further divided?

Interstitial fluid (11L)
Plasma (3L)

7

What is the primary ion present in intercellular fluid?

Potassium

8

What is the primary ion present in extracellular fluid?

Sodium

9

What anion is mainly present in the plasma?

Proteins

10

What are the 3 reasons for prescribing IV fluids?

Resuscitation
Maintenance
Replacement

11

What are the indications for fluid resuscitation?

Hypovolaemia.
Provides urgent intravascular correction to restore organ perfusion.

12

What changes should be made to fluid prescribing if the patient is septic?

Significantly higher amount of fluid due to increased vascular permeability.

13

What are the indications for fluid maintenance?

To meet fluid and/or electrolyte requirements that are not being met orally or enterally.

14

What are the indications for fluid replacement?

Insensible losses
To replace any losses due to imbalances, ongoing losses, or redistribution problems.

15

What constitutes insensible fluid losses?

Sweating
Diarrhoea
Vomiting
Other pathological processes

16

What considerations should be made when prescribing fluids?

Aim of the fluid
Weight and size of patient
Patient co-morbidities: especially CKD and HF
Reason for admission
Electrolytes

17

State the contents of 0.9% saline

Sodium (154 mmol)
Chloride (154 mmol)

18

State the contents of 5% dextrose

Glucose (50 mmol)

19

State the contents of Hartmann's

Sodium (131 mmol)
Chloride (111 mmol)
Potassium (5 mmol)

20

Why is 0.9% saline ideal for fluid resus and maintenence?

It quickly equilibriates across the ECF. Distributes across ICF slower than dextrose.

21

Why is 5% dextrose appropriate for fluid maintenence?

It quickly distributes across all fluid compartments.

22

What is the benefit of using Hartmann's solution?

It provides some potassium in addition to fluid.

23

What IV infusion can be given in hypoglycaemic emergencies? Why is monitoring required afterwards?

Hypertonic 10-20% glucose
It can irritate veins

24

What are the daily requirements of water, Na, and K for the average patient?

Water: 1500-2500ml
Na: 50-100 mmol
K: 40-80 mmol

25

List 4 signs of mild-moderate dehydration

Dry mucous membranes
Dizziness
Fatigue
Reduced skin turgor
Postural hypertension
Slow capillary refill
Oligouria

26

List 3 signs of severe dehydration

Weakness
Hypotension
Tachycardia
Anuria
Confusion
Coma

27

List 4 signs of fluid overload

Raised JVP
Basal crepitus
Peripheral oedema
Pulmonary oedema

28

List 2 signs of severe fluid overload

Tachycardia
Tachypnoea

29

What should be done after fluid replacement?

Reassessment to determine if additional maintence is required.

30

Define hyponatraemia and state how its causes can be grouped

Na <135 mmol/L

Hyponatraemia with hypovolaemia
Hyponatraemia with euvolaemia
Hyponatraemia with hypervolaemia

31

Outline the causes of hyponatraemia with hypovolaemia

Extrarenal: (Urinary sodium <20 mmol/L)
Vomiting
Diarrhoea
Haemorrhage
Burns
Pancreatitis

Kidney: (Urinary sodium >20 mmol/L)
Osmotic diuresis
Diuretics
Adrenocortical insufficiency
Tubulo-interstitial renal disease
Unilateral renal artery stenosis
Recovery phase of ATN

32

How does hyponatraemia with hypovolaemia present?

Dominated by features of volume depletion.

33

Outline the causes of hyponatraemia with euvolaemia

Abnormal ADH release, SIADH
Major psychiatric illness
Increased ADH sensitivity
ADH-like subtances, oxytocin
Chronic alcohol abuse

34

What is a serious complication of hyponatraemia with euvolaemia? Which patients are most at risk?

Hyponatraemia encephalopathy

At risk: Post-op premenopausal females, children, hypoxic

35

Outline the causes of hyponatraemia with hypervolaemia

Heart failure
Liver failure
Oliguric kidney injury
Hypoalbuminaemia

36

What is SIADH

Syndrom of inappropriate ADH secretion.
Causes water retention and hyponatraemia

37

Outline causes of hypernatraemia

Water deficit
Iatrogenic
ADH deficiency: pituitary diabetes insipidus
Insensitivity to ADH: nephrogenic diabetes insipidus

38

When are clinical features present in hyponatraemia?

Often asymptomatic if mild to moderate or chronic (due to cerebral adaption).

Symptoms are dependent on severity of hyponatraemia and rate of fall.

Sudden fall to 125 mmol/L can result in convulsions

39

What symptoms can occur in mild hyponatraemia?

Anorexia
Headache
NaV
Lethargy

40

What symptoms can occur in moderate hyponatraemia?

Personality change
Muscle cramps and weakness
Confusion
Ataxia

41

What symptom can occur in severe hyponatramia?

Drowsiness

42

What causes convulsions in hyponatraemia?

Sudden fall to 125 mmol/L

43

What signs can present in hyponatraemia?

Neurological signs
Signs of hypovolaemia
Signs of hypervolaemia

44

State the neurological signs present in hyponatraemia

Decreased level of consciousness
Cognitive impairment
Focal or generalised seizures
Brainstem herniation (severe acute)

45

Which investigations should be done in suspected hyponatraemia?

Sodium
Potassium - Addison's disease
Serum hypo-osmolality to confirm SIADH
Urine sodium - renal cause
TSH and thyroxine
Imaging

46

Outline management principles for hyponatraemia

Correct underlying cause
Acute symptomatic: Hypertonic saline 3%
Chronic/asymptomatic: Saline (not hypertonic)

IV saline if hypovolaemic
Fluid restrict if SIADH

47

What is the commonest cause of acute hyponatraemia in adults?

Post-operative iatrogenic hyponatraemia

48

What complication can occur with hyponatraemia?

Sudden fall: Severe cerebral oedema and herniation.

Chronic: Cerebral oedema without herniation, Rhabdomyolysis, seizures, respiratory arrest.

49

What complication can occur if hyponatraemia is corrected too rapidly? How does this present?

Central pontine myelinolysis (Osmotic demyelination syndrome).

Typically presents with quadriplegia and pseudobulbar palsy. Locked-in syndrome can also occur.

50

What is the limit for sodium correction daily in hyponatraemia?

8 mmol/L per day