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Fluids and electrolytes > Fluid & Electrolytes > Flashcards

Fluid & Electrolytes Flashcards

1
Q

What is the distribution of Total Body Fluids?

A

TBF = 50-60% of body weight > 60% ICF + 40% ECF

> ECF = 75% interstitial + 25% intravascular

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2
Q

Which fluids are crystalloids and colloids?

A

Crystalloids:
- D5W, D10W, D20W
- Nacl 0.9%, Nacl 0.45%, Nacl 3%
- Hartmann
- Lactate Ringer
- Plastmalyte
- D5/Nacl 0.2%, D5/Nacl 0.45%, D5/Nacl 0.9%

Colloids:
- Albumin 5%, 25%
- Dextran
- Gelafusin
- Hetastart

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3
Q

Pros and cons btw crystalloids and colloids?

A

Crystalloids:
- small molecules (water, Na+, Cl-, Dextrose)
- expands intravascular volume, but also partitions into interstitial spaces
- cheap and readily available
- larger total volume required
- shorter duration of action

Colloids:
- large molecules (albumin)
- expands intravascular volume by drawing fluids from interstitial space
- expensive
- smaller total volume required
- longer duration of action
- allergy reactions, renal toxicity, coagulation disturbances, interfere with cross matching

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4
Q

what is the physiological osmolarity of plasma?

A

295-310 mOsm/kg

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5
Q

Nacl
- what is the indication?
- pros?
- cons?

A

Indication: treat low ECF e.g. volume depletion from haemorrhage, shock, mild hypoNa

Pros:
- Max volume expansion: 20-25%
- Duration of action: 1-4h
- Fluid of choice for resuscitation

Cons:
- High Cl- content > may cause hyperchloremic metabolic acidosis > hyperkalemia

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6
Q

Dextrose
- what is the indication?
- pros?
- cons?

A

Indication:
- D5W: used to treat Hypernatremia, hypotonic
- D10W & D20W: hypertonic, provides free water and calories
- D50W: treat severe hypoglycaemia - give as 10ml IV bolus

MOA: dextrose is metabolised to water and CO2 –> eqv to “free” water

Cons:
- incr risk of hyperglycaemia
- NOT for fluid resuscitation, wont remain in IV space > water can cross membranes and evenyl distribute in TBF
- cross cerebral cells > elevated intracranial pressure

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7
Q

Hartmann solution:
- what is the indication?
- pros?
- cons?

A

Indication:
- fluid resus in burns and trauma, blood loss, hypovolemia due to third space shifts

MOA: goes into both IV and interstitial space > useful for fluid resus + maintenance

Pros:
- physiologically adaptable fluid
- sodium lactate: alkalinizing agent metabolised to bicarbonate and water
- has physiologic Cl content&raquo_space; adv over NS (so does not cause HyperCl Metabolic Acidosis)

Cons:
- Alkalosis
- Severe liver impairment
- contains Calcium with chelates with drugs

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8
Q

Plasmalyte?

A

Compared to HM:
- Higher osmolarity > more suitable for neuro pt
- less Cl content than HM and NS
- contains Mg

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9
Q

Plasmalyte/HM vs NS - which is better?

A
  • Plasmalyte/HM: less incidence of death, RRT/AKI in critically and non-critically ill patients
  • Plasmalyte has more physiological plamsa Cl & pH than NS&raquo_space; less risk of hyperCl metabolic acidosis & less rise of SCr
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10
Q

Albumin 5%
- what is the indication?
- MOA?
- pros?
- cons?

A

Indication:
- Fluid resus/maintenance

MOA: albumin is retained in IV compartment and creates colloidal osmotic pressure (oncotic pressure) > fluids travel from interstitial space to IV space > expansion of IV space

Pros:
- long duration of action compared to NS > 12-24h

Cons:
- Na and Cl content is higher than Nacl > greater risk of hyperCl metabolic acidosis

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11
Q

Albumin 25%
- what is the indication?
- MOA?
- pros?
- cons?

A

Hypertonic (compared to 5% Alb)

Indication:
- pooling of third spacing e.g. anascara. ascites
- post paracentesis in ascites

NOT used for fluid resus

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12
Q

Fluid Resuscitation: what is the initial management?

A

500-1000ml BOLUS over 30-60min

Choice of fluids: NS, HM, Albumin 5% > ISOTONIC fluids

the process is continued until SnS of IV volume depletion are improving

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13
Q

What fluid should NOT be used for fluid resus?

A

D5W
- is rapidly metabolised into water and CO2
- water is free to cross any membrane in the body

i.e. when 1L of D5W is administered IV, only ~500ml of fluid remains in the IV compartment

In neuro pts, with elevated intracranial pressure, D5W may result in “free” water crossing into cerebral cells > cerebral edema > further elevating ICP :(

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14
Q

NS vs Albumin 5%–Which is better for fluid resus?

A

Theoretical advantage of Albumin vs 0.9% NaCl?
1) Stays in IV space, exert oncotic pressure
2) Volume expanding effect much greater than 0.9% NaCl

SAFE study:
Neither albumin or 0.9% NaCl was proven superior in critically ill patients for fluid resuscitation (no difference in mortality)

Among critically ill patients with TBI, fluid resuscitation with albumin was associated with higher mortality rates than was resuscitation with 0.9% NaCl.

Conclusion: Dr’s preference, cost issues
- colloids carry an incr risk of anaphylaxis

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15
Q

Crystalloids vs colloids for fluid resus?

A

CRISTAL RCT:
NO significant difference in 28-day mortality. 90-day slightly favoured use of colloids

Cochrane study:
LITTLE to NO difference in mortality

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16
Q

When might colloids > crstyalloids?

A
  1. After fluid resuscitation with crystalloid (usually 4–6 L) has failed to achieve hemodynamic goals or after clinically significant edema limits the further administration of crystalloid
  2. Albumin may be considered in patients with low serum albumin who have required a large volume of resuscitation fluid.
  3. Patients with clinically significant edema, low albumin and poor diuresis
17
Q

Maintenance fluids:
- Enteral nutrition vs Parenteral?
- Appropriate regimen?

A

When possible, Enteral nutrition > Parenteral

Goals of using maintenance IV:
- Prevent dehydration and maintan a normal fluid and electrolyte balance

NICE IV fluid therapy:
- 25-30 ml/kg/day of water
- 1 mmol/kg/day of K, Na, Cl
- 50-100 g/day of glucose

18
Q

Signs and symptoms of
- Fluid depletion
- Fluid overload

A

Fluid depletion:
- dry mucous membranes, decreased skin turgor
- decr urine output (goal: > 0.5ml/kg/hr)
- Orthostatic hypotension
- incr capillary refill time
- tachycardia >90
- low BP < 90

Fluid overload
- raised JVP
- peripheral or sacral edema
- pulmonary edema > SOB
- increased weight overnight

19
Q

Hypokalaemia - Definition?

A

K < 3.5 (normal 3.5-5.1)

Mild: K 3.0-3.5 > Asymptomatic

Moderate: 2.5-3.0 > Cramping, malaise, myalgia, weakness

Severe: <2.5 > ECG changes, arrhythmia, paralysis

20
Q

Hypokalaemia - treatment?

A

Correct HYPOMg first!!

Mild - moderate (asymptomatic):
PO KCl 10-20 mmol/day, in 2-4 divided doses
Dosage forms:
- KCl 600mg SR tabs (8mmol), 500mg/5ml > 600mg OM - 1.2g TDS
- KCl mixt (6.7mmol/5ml) > 10-20ml TDS

Severe/ Moderate (symptomatic):
IV KCl 7.45% 10ml inj (10mmol) in 100ml NS/WFI infused over 1h (peripheral line)

REMINDER: must always have a duration of treatment to prevent overcorrection + recheck serum K

SE: phlebitis and pain at site of infusion

21
Q

How much does 10mmol (= 750mg KCK) of K Increase serum K by?

A

Every 10mmol of K administered ≈ increase serum K by 0.07mmol/L

22
Q

Can IV KCl be given as IV bolus?

A

NO!!!

only give as slow infusion.

23
Q

How to minimise KCl-infusion related pain/discomfort?

A
  1. slow down IV infusion rate > assess urgency of K replacement
  2. Infuse concurrently with maintenance IV fluid via the Y-junction of the IV line, if possible
  3. Consider absolute patency of vein. Observe for extravasation as it can lead to tissue necrosis.
  4. Ice pack
  5. 3ml of 1% lignocaine prior
24
Q

Hyperkalemia > Definition?

A

K > 5.0

CHECK! was the sample RBC hemolysed?

mild: 5.1-5.9
moderate: 6-7 (abnormal cardiac conduction/ECG changes)
severe: >7.0 ( muscle weakness/paralysis)

25
Q

Hyperkalemia > Treatment

A
  1. treat underlying causes e.g. stop supplements, high K diet, drugs promoting K retention
  2. when K >6.5 + ECG changes:
    URGENT Cardioprotection with 10ml IV bolus 10% Calcium gluconate over 2-3min
    - onset: within min
    - dose can be repeated if ECG changes persist
    - IV calcium is administered for myocardium membrane stabilisation and does not promote the intracellular shift or elimination of potassium
  3. IV actrapid 10units + 40ml D50W over 15min (order set)
    - if hyperglycaemic, can give insulin alone or lesser D50
    - onset: 10-20min > lowers serum K by 0.5-1.5mmol/L within 1h
  4. Sodium Polystyrene sulfonate (Resonium)
    PO 15g OD-QDS
    SE: risk of intestinal necrosis
    REMEMBER! space 3h apart from other PO drugs
  5. Sodium zirconium cyclosilicate (Lokelma)
    PO 10g TDS for 48h
    Advantage:
    - overall lower Na content
    - no risk of intestinal necrosis
    Disadvantage:
    - more expensive than Resonium
  6. Salbutamol 10-20mg in 4ml of NS nebulised over 10min , or 0.5mg IV infusion
  7. IV Sodium bicarbonate 50mmol infused slowly over 5min
  8. Loop/thiazide diuretics
  9. Dialysis
26
Q

HypoMg - Definition?

A

Mg < 0.7mmol/L]

Mild: 0.6-0.6
Moderate: 0.4-0.6
Severe: <0.4

usually due to impaired GI absorption, drugs

SnS:
- neuromuscular: tetany, twitching, seizures
- CV: arrhythmia, sudden cardiac death, hypertension

27
Q

HypoMg - treatment?

A

No/minimal symptoms:
- PO Mg (elemental) 250-500mg BD
- SE: diarrhoea, GI discomfort
- DDI: Levothyroxine, Mycophenolate, phosphate binders, Oral tetracycline, Raltegravir

Symptomatic or Mg <0.5:
- 2-4g Mg sulfate (8-16 mmol elemental Mg) over 4-12h
- duration: cont until 1-2 days after serum Mg conc normalises

Caution:
- renal insufficiency > incr risk of hyperMg
- Myasthenia Gravis

28
Q

Hypophosphatemia - Definition?

A

serum phosphate < 0.8

mild: 0.65-0.8
moderate: 0.32 - 0.65
severe: <0.32

29
Q

Hypophosphatemia - When to treat?

A

Mild + Symptomatic OR Moderate:
PO phosphate > Oral Fleet 2.5-5ml BD-TDS

Moderate + symptomatic OR severe:
IV Phosphate
- Potassium dihydrogen phosphate
- Sodium phosphate

30
Q

HypoCalcemia - when to treat?

A

Urgent correction with IV Ca if:
- symptomatic hypoCa
- corr Ca < 1.9
- prolonged qtc
- oral Ca contraindicated/cannot absorb

  1. Ca gluconate 10%
  2. Ca chloride 10% (3x more elemental Ca) > must be central line

Mild symptomatic/chronic hypoCa:
- PO calcium carbonate (40%) or acetate (25%)

31
Q

Hypercalcemia - when to treat?

A

Mild (<3) to Moderate asymptomatic:
- immediate tx NOT required
- ensure sufficient hydration 6-8 glasses of water/day

Moderate (3-3.5) Symptomatic to Severe (>3.5):
1. Hydrate with ISOTONIC saline: initial rate of 200-300ml/hr, then adjust to maintain urine output at 100-150ml/hr&raquo_space; promotes renal eliminate of Ca

  1. IM/SC Salmon Calcitonin (4 IU/kg)
    - repeat Ca levels in 4-6h&raquo_space; if hypoCa response is noted, then pt is calcitonin sensitive and the calcitonin can be repeated q6-12h
  2. Bisphosphonates (concurrently with saline + calcitonin)
    - IV zolendronic acid 4mg over 15min > max effect occurs aft 2-4days, can redose aft 1 week
    - CI: Crcl < 35
  3. SC denosumab > if pt refractory to OR CI to ZA
    - 120mg once weekly, up to 3 doses
    - concurrently with saline + calcitonin
32
Q

Metabolic acidosis (low bicarb)
- Definition
- treatment

A

Definition:
- blood pH <7.35
- Bicarb < 22 mmol/L

Treatment:
- IV sodium bicarb 8.4% injection in 20ml or 250ml > give as 75ml in 425ml D5 (peripheral line)
- PO sodium bicarb tabs 500mg-1g TDS

33
Q

Metabolic Alkalosis (high bicarb)
- Definition
- treatment

A

Definition:
- blood pH > 7.45
- bicarb 29

Treatment:
- IV Acetazolamide

34
Q

Hyponatremia
- Definition
- Treatment

A

Mild: 130-135
Moderate: 125-129
Severe: < 125

Treatment:
- IV Nacl 0.9%
- IV Nacl 3.0%
- PO Nacl/dextrose SR tablet

rule of thumb:
- incr the serum Na by 10mmol/L during the first 24h, then by 8mmol/L q24h until serum Na 130mmol/L
- avoid overly rapid correction to prevent Osmotic demyelination syndrome

35
Q

Hypernatremia
- Definition
- treatment

A

serum Na > 145 (thirst, confusion, coma)

treatment:
- IV Nacl 0.45%
- IV D5W

Fluids and electrolytes (2 decks)

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