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Surgery > Fluids and Nutrition > Flashcards

Fluids and Nutrition Flashcards

1
Q

Body composition of water?

A

Total water: 60% of 70kg = 42L

2/3 intracellular = 28L

1/3 extracellular = 14L

  • Plasma 3L, Interstitial 10L, transcellular 1L
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2
Q

what is osmotic pressure?

A

pressure which needs to be applied to prevent the inflow of water across a semipermeable membrane

ie. ability of solute to attract water

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3
Q

what is oncotic pressure?

A

form of osmotic pressure exerted by proteins

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4
Q

what is hydrostatic pressure?

A

pressure exerted by fluid at equilibrium due to the force of gravity

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5
Q

third spacing of fluids leads to decrease in?

A

extracellular fluid

ie. bowel obstruction -> decreased fluid reabsorption -> 3rd space loss

peritonitis -> ascites -> 3rd space loss

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6
Q

minimum urine ouput should be?

A

0.5 ml/ kg/ h = 30 ml/kg for 60kg human

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7
Q

what is the Na daily requirement?

A

1.5- 2 mmol/kg/day = 120 mmol/ day for 60 kg

140 mmol/ day for 70 kg

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8
Q

what is the minimum K requirement for the day?

A

1 mmol/kg/ day = 60 mM/ day for 60kg

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9
Q

what is the average fluid daily requirement for a 60-70 kg human?

A

e.g. 1L 0.9% NaCl + 2L dextrose with 20mM K+ in each bag

each bag over 8h = 125 ml/h

replacing 3L, 154mM Na+ (around 120) and 60 mM of K+

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10
Q

what are sources of fluid losses that one should replace?

A

diarrhoea and vomiting

NG tube

drains

fever (+500mL for each degree increase)

Tachpnoea

High output stomas

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11
Q

CVP monitoring

  • what is this measuring?
A

indicates RV preload and depends on venous return and cardiac output

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12
Q

causes of raised CVP?

A

High circulating volume

Low Cardiac Output: ie. pump failure

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13
Q

Causes of reduced CVP?

A

low circulating volume

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14
Q

what is a normal central venous pressure?

A

5-10 cm H2O

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15
Q

what does it mean if CVP does not change despite fluid challenge?

A

hypovolaemic

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16
Q

what does it mean if CVP increases and reverses after 30 min of fluid bolus?

A

pt euvolaemic

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17
Q

what does it mean if CVP is sustained above 5cm H2O after fluid challenge/

A

fluid overload/ pump failure

18
Q

contents of 0.9% normal saline?

A

154 mM NaCl

used for normal daily fluid requirements + replace losses

*need to add K+

19
Q

contents of Hartmanns’/ Ringer’s Lactate solution?

A

Na: 131 mM

Cl: 111 mM

K: 5mM

Ca: 2.2 mM

Lactate/ HCO3: 29mM

use in resus for trauma pts

alkalinising solution as lactate is a conjugate base

(lactate metabolised in liver -> HCO3 production)

20
Q

what is a colloid/

A

contains large molecular weight molecules

e.g. gelatin, dextrans

to preserve oncotic pressure -> remains intravascular -> preferential increase in intravascular volume

21
Q

e.g.s of colloids

A

albumin, blood

gelofusin

22
Q

problems w colloids

A

increased risk of anaphylaxis

can interfere with cross matching -> take blood for x match before using

23
Q

How to assess fluid status before examining pt?

A

History: thirst, surgery, other losses (D+V)

look at fluid balance chart

impression: pt drowsy?

24
Q

Assessing pt fluid status on examination?

A

inspection: drips, drains, stomas, catheters, CVP

central CRT, HR, BP lying and standing

JVP

skin turgor, mucous membranes

oedema?

Urine Output, Urea/ creatinine

25
Q

What to consider when prescribing fluids post op?

A

Post op:

raised ADH/ cortisol/ aldosterone -> Na + H20 conservation

raised K+: tissue damage, transfusion, stress hormones

solutions:

use UO to guide fluid replacement but may decrease maintenance fluids to 2L first 24h post op

Avoid K+ supplementation for first 24h post op

26
Q

what are some problems to consider in cardiac or renal failure when prescribing fluids?

A

RAS activation -> Na and H20 retention

solution: avoid fluids w Na -> give 5% dextrose

27
Q

mx of high output ileostomy?

A

Loperamide

codeine

28
Q

causes of reduced UO post op?

A

post renal: commonest

  • blocked/ malsited catheter
  • acute urinary retention

pre-renal: hypovolaemia

renal: NSAIDs, gentamicin

29
Q

mx of blocked catheter?

A

flush w 50 mL Normal saline and aspirate back

30
Q

mx of hypovolaemia causing low UO post op?

A

fluid challenge

500mL bolus over 15 min

look for CVP or UO response within minutes

31
Q

definition of refeeding syndrome?

A

life-threatening metabolic complication of refeeding via any route after a prolonged period of starvation

32
Q

what electrolytes are abnormal in refeeding syndrome?

A

low K+, Mg2+, PO4-

33
Q

Hypophosphataemia may lead to?

A

Rhabdomylolysis

Resp insufficiency

Arrhythmias

Shock

Seizures

34
Q

risk factors for refeeding syndrome?

A

malignancy

anorexia nervosa

alcoholism

GI surgery

starvation

35
Q

mx of refeeding syndrome?

A

liase w dietician

parenteral and oral PO4 supplementation

tx complications

36
Q

caloric requirements?

A

20-40 kcal/ kg/ day

37
Q

indications for enteral nutrition?

A

catabolic: sepsis, burns, major surgery

coma/ ITU

malnutrition

dysphagia: stricture, stroke

38
Q

complications of Ng tube for enteral nutrition?

A

nasal trauma

malposition -> aspiration pneumonia

tube blockage

39
Q

complications following enteral nutrition?

A

refeeding syndrome

aspiration

electrolyte imbalance

feed intolerance -> diarrhoea (build up feeds gradually to prevent diarrhoea)

40
Q

indications for parenteral nutrition?

A

prolonged obstruction or ileus (>7d)

high output fistula

short bowel syndrome

severe crohns/ malnutrition/ pancreatitis

unable to swallow

41
Q

how is parenteral nutrition delivered?

A

centrally as high osmolality toxic to veins

  • short term: via CV catheter
  • long term: via Hickman or PICC line

sterility is essential: use line ONLY for PN

42
Q

complications of parenteral nutrition?

A

line related:

line sepsis, cardiac arrhythmia, pneumo/haemothorax, central venous thrombosis

feed related:

villous atrophy of GIT

electrolyte disturbances - refeeding syndrome

hyperglycaemia and reactive hypoglycaemia

vitamin and mineral deficiencies

Surgery (17 decks)

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