Lecture 19: Clinical Problems: Electrolytes Flashcards

1
Q

Question to ask before giving IVF

A
  • is my patient, euvolaemic, hypovolaemic (dehydrated) or hypervolaemic (fluid overload)
  • Does my patient need IVF
  • How much?
  • What type do they need?
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2
Q

Types of Fluid

A

Hypotonic Fluid: (fluid→ cells, cells swell)

Hypertonic Fluid: (Fluid → out of cells, cells shrink)

Isotonic Fluid: Keep everything the same

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3
Q

How do you assess volume status (fluid overload or dehydrated)

A

Fluid Overload:

  • Weight gain
  • Swollen ankles
  • High BP

Dehydration:

  • Weight loss
  • Dry mouth
  • Low BP
  • Dizziness
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4
Q

When DOESN’T the patient need IV fluids

A

Drinking enough, on enteral feed, already fluid overloaded

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5
Q

What are the IV fluids for?

A
  1. Maintenence: to maintain normal fluid balance (in patients not drinking/eating etc)
  2. Replacement of losses: replace lost body fluids + electrolytes (vomiting, poops etc)
  3. Rescuscitation: hypotensive, very very sick and need heaps of fluid to get system up.
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6
Q

How much is maintenence fluid?

A

~2-3L

To counteract loss from pee, poo, sweat and breathing

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7
Q

What is the 4:2:1 rule for paediatric IVF

A

Babies don’t need the same amount of fluid as adults (1L bag over 8hrs = 3L/day)

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8
Q

Replacement Fluid: What might you be replacing? How do you know what to replace

A

Vomiting, post-surgery drainage, poops!

Replacing loss + continue maintenence fluid!

  • Careful assessment of fluid status (weight and JVP helpful)
  • Patient record of losses (fluid balance charts)
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9
Q

What do we need to do if a patient is SHOCKED

A

Rescuscitation: give them a lot of fluid really quickly to bring the BP up

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10
Q

When do you give Isotonic fluid?

A

Generally give this (safest). Unless your giving maintanence fluid and your overloaded (give hypotonic), or have a high serum Sodium (give hypotonic)

Plasmalyte (mimics plasma) or saline (0.9% NaCl)

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11
Q

When do you give hypotonic fluid?

A

Rarely, when the patient needs maintenence fluid but already overloaded or with a high serum Na+.

Use 5% dextrose: start as isotonic but metabolised bu cells to → free water

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12
Q

When do you give Hypertonic Fluid?

A

For very low serum Na+

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13
Q

What is Hyponatraemia (low serum sodium)?

A

due to water excess (not low Na+).

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14
Q

Where is the IV fluids going?

A

Extracellularly

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15
Q

Na+ loss is from?

A
  • GI loss (vomiting, diarrhoea)
  • Hypo-aldosterone (less Na+ reabsorbed)
  • Sweat
  • Diuretics
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16
Q

What is Pseudohyponatremia??

A

When lab tests say you have low Na+ but you don’t!!

Very high triglycerides or protein

17
Q

When do you get water excess?

A

Syndromes with water overload:

  • Cirrhosis
  • Heart Failure
  • Nephrotic Syndrom

SIADH

Polydipsia

18
Q

Whats the serum osmolality like in hyponatremia?

A

Low! (most of osmo from Na+)

19
Q

Water Excess with euvolaemia

A

No signs of dehydration, oedema, JVP not elevated.

No evidence of fluid overload, so it’s probably
-SIADH
-Polydipsia
-Overhydration with low Na IVF
Diuretics

20
Q

How do you know the hyponatraemia is due to Polydipsia?

A

The patient will have a unusually low urine osmolality

(usually hyponatraemic patients have high urine osmolarity)

21
Q

SIADH

A

Usually in response to low BP or dehydration (sensed via baroreceptors and osmoreceptors)

ADH release despite neither of these occuring

Causes: tumors, CNS, drugs, lung disease

22
Q

Diuretics

A

Commonest tohave low Na+ with Thiazides

  • can lead to an increased ADH
  • cause decreased Na+ through decreasing NA+ reab.

Like SIADH but due to a drug

23
Q

Correction of Hyponatraemia

A
  • Saline* for a dehydrated patient with sodium loss
  • Fluid restriction* for patients with water excess