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Supporting life block > Fluid& electrolyte balance > Flashcards

Fluid& electrolyte balance Flashcards

1
Q

What proportion of our body weight is made up of total body water

A
  • 60% of ideal body weight for men

- 50-55% of ideal body weight for women

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2
Q

What is TBW made up of

A
  • 2/3= intracellular fluid

- 1/3= extracellular fluid

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3
Q

What is intracellular fluid made up of?

A
  • 75% interstitial fluid

- 25% plasma

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4
Q

What is the blood volume for females and males respectively?

A
  • 65ml/kg (females)

- 75ml/kg (males)

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5
Q

What are insensible losses?

A
  • We can’t detect/sense how much we’re losing

- e.g skin &lungs

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6
Q

What generates the differences between electrolyte distribution between the ECF&ICF?

A

The Na+/k+ pump

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7
Q

What can we always be certain of in terms of ions in any fluid?

A

In any fluid the total cations=total anions

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8
Q

What is the total Na in the body made up of?

A
  • 25% non exchangeable (in tissues such as bone)- slow turnover
  • 75% exchangeable- ECF
  • Normal range in plasma is 135-145mmol/L-reflects body water content
  • sodium consumption variable 110-220mmol/day
  • Approx 5-10mmol loss in sweat& faeces, most regulated by kidneys
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9
Q

How is sodium excretion regulated by?

A
  • Renin-angiotensin-aldosterone
  • Natriuretic peptides
  • Intrinsic renal mechanisms
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10
Q

How is dehydration/ increased osmolarity monitored/ controlled

A

Via the ADH system

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11
Q

Is the collecting duct permeable to water?

A

-If ADH is present, the collecting duct is highly permeable to water

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12
Q

In the case of fluid overload, how is this detected?

A
  • Atrial natriuretic peptide( ANP) is released when the atria are stretched
  • Brain/ B-type natriuretic peptide is released when the ventricles are stretched
  • Detected in the heart
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13
Q

What effect do the natriuretic peptides have on the afferent and efferent arterioles to the glomerulus

A
  • Dilate the afferent arteriole to the glomerulus

- constrict the efferent arteriole

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14
Q

What effect do the natriuretic peptides have?

A
  1. ) cause vasodilation & this decreases blood pressure
  2. ) Decrease renin which decreases ang II & aldo; this subsequently increases GFR leading to natriuresis& diuresis
  3. ) Increase GFR leading to decreased renin & allows for natriuresis and diuresis
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15
Q

When and why do we prescribe IV fluids?

A
  1. ) MAINTENANCE: To maintain euvolaemia when oral intake is reduced e.g being NBM,nauseated,vomiting or diarrhoea
  2. ) REPLACEMENT: previous/ongoing or predictable future losses such as Diaorrhea and vomitting, drains, urine, sweat,3rd spacing,burns , surgery, polyuria
  3. ) RESUSCITATION: Reapidly restore intravascular compartment e.g following haemorrhage,marked dehydration, vasodilation, shock
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16
Q

What are the symptoms & clinical signs of someone with hypovolemia?

A
  • Symptoms: GI losses, thirst,lethargy,postural dizziness,reduced urine volume, confusion
  • Clinical signs: Pulse=fast&weak; BP postural drop >20mmHg or low BP; loss of skin turgor;sunken eyes;dry mucous membranes
17
Q

What are the symptoms & clinical signs of someone with hypervolemia?

A
  • Symptoms: breathlessness,peripheral oedema,weight gain, abdominal bloating, confusion
  • Clinical signs: Pulse can be fast,bounding; BP can be high, can be low; skin turgor generally maintained; can have peripheral oedema; JVP can be elevated; can have ascites
18
Q

Which fluids can we use for resuscitation?

A
  • 0.9% NaCl
  • Balanced crystalloid solutions, such as Hartmann’s solution
  • Colloids
19
Q

Which fluids can we use for maintenance of blood volume?

A
  • 5% glucose

- Glucose& saline solutions, such as 0.18% saline in 4% glucose

20
Q

What is hyponatraemia?

A

Na<135mmol/L

-Low na in the blood

21
Q

How can we classify hyponatraemia?

A
  1. ) Hypovolaemia
  2. )Euvolaemia: urine Na>30mmol/L
  3. )Hypervolaemia urine Na <25mmol/L and in chronic kidney disease urine Na>30mmol/L
22
Q

What is SIADH?

A

syndrome of inappropriate ADH secretion

23
Q

What are the signs& symptoms of hyponatraemia?

A

Presence of symptoms related to severity

  • MILD hyponatremia(130-135mmol/L) = asymptomatic
  • MODERATE hyponatraemia(121-129mmol/L)=cramps,weakness,nausea
  • SEVERE hyponatraemia(,120mmol/L)= lethargy, headache,confusion
  • SEVERE& RAPIDLY EVOLVING hyponatraemia= seizures, coma,respiratory arrest

Osmotic gradient between ECF& ICF within the brain

  • Water moves into cells
  • Raised intracranial pressure due to oedema-Neurological symptoms
24
Q

How can we treat hyponatraemia?

A
  • Hypovolemia: correct volume depletion e.g 0.9% saline
  • Euvolaemia: underlying cause, fluid restriction
  • Hypervolaemia: underlyng cause, fluid restriction (vasopressin receptor antagonists)
  • Aggressive therapy used if the symptoms are severe and there has been acute hyponatraemia for less than 24hours
25
Q

What is the risk associated with rapid correction of low Na?

A

-Risk of central pontine myelinosis( a neurological disorder caused by severe damage of the myelin sheath of nerve cells in the pons; may be iatrogenically induced

26
Q

What is hypernatraemia & what are the symptoms ?

A
  • Na >145mmol/L
  • Results from: net water loss, hypertonic Na gain
  • Increase in plasma toxicity pulls water out of cells, resulting in a decrease in intracellular volume
  • severe if Na>158mmol/L
  • Symptoms: thirst,anorexia,weakness,stupor,seizures,coma
27
Q

How can we classify hypernatraemia?

A
  • Un-replaced water loss

- Sodium overload

28
Q

How can we treat hypernatraemia?

A
  1. ) Chronic hypernatraemia:
    - Treat underlying cause
    - Use of hypotonic fluid e.g 5% dextrose given slowly
    - Lower Na by max of 10mmol/L per day
    - always reassess
  2. ) Acute therapy/emergency
    - Hypotomic fluid
    - Lower Na by 1-2mmol/L/h to restore normal Na levels within 24h
    - Because acute, increase in the plasma Na can lead to irreversible neurologic injury— needs expert help
29
Q

What is hypokalaemia?

A
  • K<3.5mmol/L
  • K enters the body via oral intake or IV, largely stored in the cells, excreted in urine
  • Results from : decreased K intake; increased entry into cells; increased losses (GI/urine)
  • Manifestations are proportionate to severity…
    1. ) Muscle weakness; usually when <2.5mmol/L-progresses from lower extremities
    2. ) ECG changes &arrhythmias
    3. ) Chronic: renal abnormalities; impaired concentrating ability, raise BP
30
Q

What ECG changes may be present in hypokalaemia?

A
  • Flat T wave
  • U waves
  • ST depression
  • PR interval prolonged
  • Prolonged QT intervals
31
Q

How can we treat hypokalaemia?

A
  • Correct Mg levels
  • K replacement- oral vs IV
  • If IV max 10-20mmol/hr and cardiac monitoring
32
Q

What is hyperkalaemia?

A

k>5.5mmol/L

-Classified as 1.) increased release from cells 2.) reduced urinary excretion

33
Q

What are the symptoms of hyperkalaemia?

A
  • Paraesthesiae
  • Muscle weakeness-paralysis
  • arrhymias
34
Q

What ECG changes may result from hyperkalaemia?

A
  • Tall peaked T waves
  • shortened QT interval
  • PR interval lengthening
  • QRS widening
  • P waves disappear- sine waves
35
Q

How can we treat hyperkalaemia?

A
  • IV calcium gluconate- antagonise membrane action of high K
  • IV insulin with glucose- drive K into cells
  • Remove K from the body(consider loop diuretics, haemodialysis& haemofiltration)
  • Other therapies to drive K into cells: sodium bicarbonate, Beta agonists

Supporting life block (28 decks)

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