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Surgery > Fluids > Flashcards

Fluids Flashcards

1
Q

Why do fluids should be prescribed? (3) - general indications)

A
  • resuscitation
  • maintenance
  • replacement
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2
Q

General/ key considerations to remember before we prescribe fluids?

A
  • aim of the fluid -> resuscitation, maintenance, or replacement
  • weight and size of the patient
  • co-morbidities -> e.g. heart failure or chronic kidney disease
  • underlying reason for admission (e.g. sepsis or bowel obstruction will require aggressive fluid treatment)
  • most recent electrolytes levels
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3
Q

Fluid distribution around the body

(total body weight, intracellular, extracellular and transcellular)

A
  • around 2/3rd of total body weight is water -> around 2/3 of this distributes in to the intracellular fluid -> the remaining 1/3 will distribute in to the extracellular fluid
  • Of that fluid in the extracelular space -> around 1/5th stays in the intravascular space -> 4/5th of this is found in the interstitium + a small proportion in the transcellular space
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4
Q

What fluid compartments we want the fluid to stay in:

  • general hydration purposes
  • fluid resuscitation
A
  • Maintenance of hydration -> all compartments
  • Resuscitation -> we want to increase perfusion to the organs so we want most of the fluids in intravascular space
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5
Q

What happens to the fluid in intravascular compartment in sepsis?

A

Sepsis -> thigh junctions between capillary endothelial cells break -> vascular permeability increases -> fluid leaves the vasculature and enters the tissues

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6
Q

What’s required in terms of the fluids in sepsis?

A

As the fluid will escape intravascular compartment -> we need to give large amounts of IV fluids to maintain intravascular volume

  • need to monitor fluid balance
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7
Q

What population groups (2) and why should we take caution in while replacing the fluids?

A

Elderly and if HF -> due to risk of pulmonary oedema

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8
Q

What are insensible fluid loses?

A
  • insensible fluid loses -> loss of fluids in the patient that do not come from the urinary output (e.g. respiration, sweating and faeces)
  • insensible fluid loses raise in unwell patient as they may be: febrile, tachypnoeic or have increased bowel output -> need to take it into account while planning fluid replacement
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9
Q

Where does a fluid input come from?

A
  • 3/5 of fluid input comes from an enteral route input
  • the rest come from metabolic and food processes

*if pt NBM we need to replace or sources via parenteral route

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10
Q

Why does a patient may excessively urinate in the post-op period?

A

As patient will be recovering, they vascular permeability may return to normal -> therefore if an excess of fluid (e.g. by fluid replacement) they may urinate more to correct the levels to their baseline

  • allow it to happen but monitor their electrolytes
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11
Q

Signs of the fluid depletion in a patient

A

In a fluid-depleted patient:

  • dry mucous membrane
  • reduced skin turgor
  • orthostatic hypotension
  • decreased urine output (<0.5 ml/kg/hr)

In worsening stages: tachycardia, hypotension, increased cap refill

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12
Q

Signs of fluid overload in a patient

A
  • peripheral and sacral oedema
  • pulmonary oedema
  • raised JVP
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13
Q

What to monitor in case if a patient is fluid depleted/ overloaded?

A
  • start daily fluid input/output balance chart
  • daily weight measurement
  • monitor urea and electrolytes (U&Es) -> to check for kidney hypoperfusion, dehydration, electrolyte abnormalities
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14
Q

What are the components that need to be replaced in the fluids daily (apart from water) ? (4)

A
  • water
  • Na+
  • K+
  • glucose
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15
Q

How much needs to be replaced in the fluid daily? (NICE guidelines)

  • water
  • Na+
  • K+
  • glucose
A
  • water -> 25 ml/kg/day
  • Na+ -> 1.0 mmol/kg/day
  • K+ -> 1.0 mmol/kg/day
  • glucose -> 50g / day
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16
Q
  • 2 main categories of fluids used (setting use and name of category)
  • which one would give a faster fluid replacement effect
A

A. Crystalloids -> used widely in acute settings, theatres and as maintenance fluids

B. Colloids -> use in many hospital is decreasing (as significantly more expensive)

*there is no evidence that any of the categories is superior in terms of speed of fluid replacement

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17
Q

Example of crystalloid fluid (just names)

A
  • saline 0.9%
  • dextrose 5%
  • Dexterose saline
  • Hartmann’s solution
  • Dexterose 50%
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18
Q

What’s the purpose of giving saline 0.9%?

A

It expands extravascular compartment (75% interstitial and 25% plasma)

*only 25% o plasma expansion so need a lot of crystalloid t expand plasma

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19
Q

What’s the purpose of giving dextrose 5%?

A

Dexterose 5%

Aim: It is mostly to replace water deficit

  • it contains 50g/L of glucose
  • glucose will be readily metabolised by the liver -> water is left
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20
Q

Hartmann’s solution

  • what are the advantages
  • what happens in excess administration
A

Hartmann’s solution

  • Advantage: it is more physiologically similar -> as it contains Na+, K+, Cl-, Ca++ and lactate

*however once given it behaves like 0.9% saline -> expands extravascular volume

  • Excess administration: may cause lactic acidosis
21
Q

What are the colloids?

What are they usually used for?

A

Colloid - a substance that is unable to pass through the semi-permeable membrane -> it remains in extracellular compartment (they have greater osmolarity than plasma)

Use: extracellular volume replacement (e.g. haemorrhage or hypotension)

*not used as a general fluid replacement as stay only in extracellular compartment

22
Q

Examples (3) of colloids

A
  • gelatin derivatives (e.g. Haemaccel, Gelofusin) - made from animal gelatine; anaphylactic reactions possible
  • Human albumin solution (HAS)- only used at consultant’s/ expert’s request
  • Starch (e.g. Hetastarch, Pentastarch)
23
Q

How to manage initially a reduced urine output (in terms of fluid)

A

Reduced urine output (<0.5 ml/kg/hr)

  • commence fluid challenge
  • then, re-check clinical parameters and urine output
  • check that no urinary retention; no obstructed catheter
24
Q

How to do a fluid challenge?

A

250 ml or 500 ml over 15-30 mins

25
Q

How much fluid should be given (fluid challenge) may differ from:

A. 30 y old 120 kg lady

B. Frail, 80y old lady with renal disease and IHD

A

A. May need to give >500ml of fluid to make any difference

B. 250 ml of fluid may be enough

26
Q

What’s the normal range of serum potassium?

A

K+ range: 3.5 - 5.5 mmol/L

27
Q

Routes of potassium replacement in case of hypokalaemia

A
  • oral is preferred
  • IV - if unable to tolerate oral or if potassium is really low
  • K+ <2.5 mmol/L may require ITU admission and administration via a central line
28
Q

What are ‘third space loses’?

A

Loss of fluid ( other than urine, faeces, respiration and sweat) into the non-visible spaces e.g. through bowel lumen (intestinal obstruction) or retroperitoneum (in pancreatitis)

29
Q

Common electrolyte pattern in dehydration

A

Dehydration

high urea:creatinineratio and high ­PCV

*PCV - packed cell volume; proportion of blood that is made up of cells

30
Q

Common electrolyte pattern in vomiting

A

Vomiting:

low K+, low Cl–, and alkalosis

31
Q

Common electrolytes pattern in diarrhoea

A

Diarrhoea:

low K+ and acidosis

32
Q

Main use of:

  • crystalloids
  • colloids
A

Crystalloids -> general fluid replacement

Colloids -> hypovoluemia (haemorrhage or hypotension)

33
Q

Initial assessment of a post-op patient with a low urine output

A

Post-up low urine output => Check/ ensure that there is no:

  • ABC assessment
  • acute urinary retention -> feel for palpate bladder and positive fluid balance on the fluid chart (should be urinating)
  • ensure that a catheter is not blocked
  • hypovolemic shock -> check BP, HR, actively bleeding wounds and drains
34
Q

Case: a patient is post op and low urinary output; no signs of hypovolemia or acute urinary retention

  • possible cause?
  • what to do?
  • reassessment and possible further causes
A

Possible cause: dehydration

Management: increase IV infusion + reassess

If still low urinary output and positive response to fluid challenge-> AKI may be suspected

35
Q

Investigations to be done in a dehydrated patient (4)

A
  • U&Es
  • FBC
  • ABG
  • urinealysis
36
Q

Severity % scale of dehydration (3)

A
  • 15% → mild
  • 30% → moderate
  • 40% → severe
37
Q

Why in dehydration there may be mental state changes?

A

Due to the brain not being perfused

38
Q

What to give first: crystalloid or colloid?

A

Crystalloid first then colloid

(better in terms of the fluid movement across compartments)

39
Q

What fluids are commonly used for a fluid replacement?

A

Plasmalyte or Hartmann’s

(they contain substances similar to a normal physiological state e.g. K+, Na+, Cl-)

40
Q

Hyponatraemia

  • causes
  • presentation
A

Hyponatraemia

Causes: excess water, TURP syndrome (due to over-irrigation through an intratracheal catheter)

Presentation: impaired consciousness, confusion, clammy

41
Q

Management of hyponatraemia

  • calculation
  • what to use
A

Slow correction!!! (if done too fast → possible pontine demyelination syndrome)

Calculation:

weight (kg) x (pre-post Na) x 0.6

*pre - normal Na level/ level pre TURP

* post - current hyponatraemic level

GIve 1/2 in the first 8 hrs, 1/4 in next 8 hrs, 1/4 in next 8 hrs

Use: NaCL 1.% (infusion pump)

42
Q

Hypokalaemia

  • cause
  • presentation
  • management
A

Cause: low intake or excess loss

Presentation: ectopic beats, arrhythmia

Management:

  • Slow correction with 20mmol of KCl/hr
  • ECG monitoring
43
Q
A
44
Q

What can an excess of 0.9% NaCl cause?

A

hyperchloraemic acidosis

45
Q

What are the requirements for maintenance fluid?

  • water
  • Na, Cl, K
  • glucose
A
  • 25-30 ml/kg/day of water
  • approximately 1 mmol/kg/day of potassium, sodium and chloride
  • approximately 50-100 g/day of glucose to limit starvation ketosis
46
Q
A
47
Q

What is meant by 3rd space fluid loses?

A

Space Losses = ↓ ECF

• Bowel obstruction → ↓ fluid reabsorption → 3rd space

loss

• Sudden diuresis on day 2-3 post-op = recovery of

ileus

• Peritonitis → ascites → 3rd space loss

48
Q

What’s Parkland’s Formula? What fluid to use for that?

A

Parkland’s formula: 4 x wt x %burn = mL in 1st 24hrs

Use Hartmann’s

Surgery (18 decks)

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