Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Surgery Finals > Fluids and nutrition > Flashcards

Fluids and nutrition Flashcards

(54 cards)

Start Studying
1
Q

What % of the body is water?

A

60%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is water stored in the body?

A

2/3 intracellular = 28L

1/3 extracellular = 14L: 3L plasma, 10L interstitial, 1L transcellular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define osmotic pressure

A

The pressure which needs to be applied to prevent the inflow of water across a semipermeable membrane i.e. ability of a solute to attract water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define oncotic pressure

A

Form of osmotic pressure exerted by proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define hydrostatic pressure

A

Pressure exerted by a fluid at equilibrium due to the force of gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are hydrostatic and osmotic pressures collectively known as (whose forces)?

A

Starling’s forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What determines the distribution of fluid in the body?

A
  • ECF/ICF balance determined by osmotic pressure
  • Distribution within ECF is deterined by Starling’s forces:
    • Capillary and insterstitial oncotic pressure
    • Capillary and interstitial hydrostatic pressure
    • Filtration coefficient (capillary permeability)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are some examples of 3rd space losses?

A
  • Bowel obstruction -> decreased fluid reabsorption
  • Sudden diuresis on day 2-3 post op = recovery of ileus
  • Peritonitis -> ascites
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a typical minimum urine output?

A

0.5ml/kg/h = about 30ml/h

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the usual sodium requirement?

A

1.5-2mmol/kg/day - about 100mmol/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the normal potassium requirement?

A

1mmol/kg/day = 60mM/day

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What would be a typical fluid regimen for adults with no specific comorbidity?

A
  • 1L normal saline + 40mmol KCl over 8h
  • 1L normal saline + 40mmol KCl over 8h
  • 1L dextrose (5%) over 8 hours
  • =3L fluid, 200mmol Na, 80mmol KCl/24h
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the purpose of CVP monitoring?

A

Indicates RV preload; it depends on venous return and cardiac output such that a raised CVP indicates either increased circulating volume or decreased cardiac output (pump failure) whereas a low CVP indicates a low circulating volume.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a normal CVP?

A

~5-10cmH2O but remember a single reading isn’t as useful as serial

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do you interpret the CVP change after a fluid challenge?

A
  • Unchanged: hypovolaemic
  • Increase that reverses after 30 minutes: euvolaemic
  • Sustained increase >5cmH2O: overload/failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What might be more useful than a fluid challenge in determining the CVP response to fluids?

A

Passive leg raising - a sustained increase in CVP indicates heart failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are some examples of crystalloid fluids?

A
  • Normal saline
  • 5% dextrose
  • Dextrose-saline
  • Hartmann’s/Ringer’s lactate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the contents of normal saline and what is its pH?

A
  • 0.9% NaCL - 9g/L or 154mM NaCl
  • pH 5-6
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What can you use to give normal daily fluid requirements?

A

Normal saline, 5% dextrose or dextrose-saline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How many g of dextrose are in a bag of 5% dextrose?

A

50g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the contents of dextrose-saline?

A
  • 4% dextrose = 40g/L
  • 0.18% NaCl = 31mM NaCl
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the contents of Hartmann’s/Ringer’s lactate?

Study These Flashcards
A
  • Na: 131mM
  • Cl: 11mM
  • K: 5mM
  • Ca: 2.2mM
  • Lactate/HCO3: 29mM
23
Q

What do you use Hartmann’s/Ringer’s lactate for?

Study These Flashcards
A
  • Resuscitation in trauma patients
  • Burns: use Parklands formula - 4 x weight x % burn = mL in 1st 24 hours
24
Q

What is the pH of Hartmann’s?

Study These Flashcards
A

6.5, but it is an alkalinising solution - lactate isn’t an acid itself but a conjugate base. It’s given exogenously as sodium lactate, and lactate is metabolised in the liver producing HCO3 (Cori cycle)

25
What is the physiological reason to use colloids?
* Larger molecular weight molecules e.g. gelatin, dextrans * These preserve oncotic pressure * Therefore remain in the intravascular space, meaning they cause a preferential increase in intravascular volume
26
What are some examples of colloids?
* Synthetic * Gelofusin * Volplex * Haemaccel * Voluven * Natural * Albumin * Blood
27
What do you use colloids for?
* Fluid challenge: * 250-500ml over 15-30 mins * Hypovolaemic shock * Mount Vernon formula for burns: * (weight x % burn)/2 = ml colloid per unit time
28
What are some of the problems with colloids?
* Anaphylaxis * Volume overload * Can interfere with cross matching (so take a cross match befroe you give it)
29
What are some of the problems with post op fluids and how can you solve them?
* Issues: * High ADH, aldosterone and cortisol cause Na and water conservation * Hyperkalaemia: tissue damage, transfusion, stress hormones * Solutions * Use urine output (aiming for \>30ml/hour) to guide fluid replacement but may need to decrease maintenance fluids to 2L first 24 hours post op * Avoid K+ supplementation for first 24 hours post op
30
What are the issues with using fluids in cardiac or renal failure and how do you deal with them?
* RAS activation causes sodium and water retention * Avoid fluids with sodium - give 5% dextrose
31
How do you manage fluids in patients with bowel obstruction?
* Significant third space losses of fluid and electrolytes, so probably need more than usual * Regimen: 0.9% normal saline with 20-40 mM KCl added to each bag * Titrate fluids to clinical findings on serial examination * Serial U+Es to guide electrolyte replacement
32
What are the issues with fluids in pancreatitis and how do you manage them?
* Inflammation causes a significant fluid shift into the abdomen * Patients need aggressive fluid resus and maintenance * Insert urinary catheter and consider CVP monitoring * 0.9% normal saline with 20-40mM KCl added to each bag * Keep urine output \>30ml/hour * Serial U+Es for electrolyte replacement
33
What is the composition of ileal fluid?
* Na: 130mM * Cl: 110mM * K: 10mM * HCO3: 30mM
34
What counts as normal or high output for an ileostomy?
Normal: 10-15mL/kg/day = ~700ml/day High output = \>1000ml/day
35
How should you manage fluid status in ileostomy patients?
* The ileum will adapt to limit fluid and electrolyte losses * Fluids: * 0.9% normal saline and KCl * Daily requirements and replace losses, titrated to urine output and U+Es * If high output give loperamide and codeine
36
What are the causes of post op reduced urine output?
* Post renal * Commonest cause * Blocked/malsited catheter * Acute urinary retention * Pre renal: hypovolaemia * Renal: NSAIDs, gentamicin * Anuria usually = blocked or malsited catheter * Oliguria usually = inadequate fluid replacement
37
How do you manage reduced urine output post op?
* Information: op history, obs chart (UO), drug chart (nephrotoxins) * Examinatino: assess fluid status, examine for palpable bladder, inspect drips, drains, stomas, CVP * Action: * Suspect catheter problem: flush with 50ml NS and aspirate back * Suspect pre renal problem: fluid challenge with 250-500ml colloid bolus over 15-30 mins and look for CVP or UO response within minutes
38
How would you assess fluid status clinically?
* History: balance chart, surgery, other losses, thirsty * Impression: drowsy, alert * Inspection: drips, drains, stomas, catheters, CVP * Examination * IV volume * CRT, HR, BP lying and standing, JVP * Tissue perfusion * Skin turgor, oedema (ankle, pulmonary, ascites), mucus membranes * End organ * UO, urea and creatinine, consciousness, lactate * Other tests * Pulmonary capillary wedge pressure: indirect measure of left atrial pressure * CVP
39
How would you assess nutritional status of a patient?
* Clinical * History: weight loss, diet * Examination: skin fat, dry hair, pressure sores, cheilitis, weight and BMI (\<20kg/m2) * Anthropometric: skin fold thickness, arm circumference * Investigations: albumin, transthyretin (prealbumin), phosphate
40
What are the daily nutritional requirements for an adult per kg?
* 20-40 calories * 2g carb * 3g fat * 0.5-1g protein * 0.2-0.4g nitrogen
41
What are the options for routes of delivery for enteral nutrition?
* PO is best - consider a semi solid diet if risk of aspiration * Fine bore NGT (9Fr) * Percutaneous endoscopic gastrostomy * Jejunostomy * Build up feeds gradually to prevent diarrhoea
42
What different kinds of enteral feeds are there?
* Oral supplements * Polymeric e.g. osmolite, jevity * Intact proteins, starches and long chain FAs * Disease specific * E.g. low branched chain AAs in hepatic encephalopathy * Elemental * Simple AAs and oligo/monosaccharides * Require minimal digestion and used if abnormal GIT e.g. in Crohn's
43
What are the indications for enteral feeding?
* Catabolic: sepsis, burns, major surgery * Coma/ITU * Malnutrition * Dysphagia: stroke, stricture
44
What are some complications of enteral feeding?
* NGT * Nasal trauma * Malposition or tube blockage * Feeding * Feed intolerance causing diarrhoea * Electrolyte imbalance * Aspiration * Refeeding syndrome
45
What are the indications for parenteral feeding?
* Prolonged obstruction or ileus (\>7d) * High output fistula * Short bowel syndrome * Severe Crohn's * Severe malnutrition * Severe pancreatitis * Unable to swallow e.g. oesophageal Ca
46
How is parenteral nutrition given?
* Centrally, because the high osmolality is toxic to veins * Short term: CV catheter * Long term: Hickmann or PICC line * Sterility is essential, so only use the line for PN
47
How should parenteral nutrition be monitored?
* Standard * Weight, fluid balance, urine glucose daily * Zinc, magnesium weekly * Initially * Blood glucose, FBC, U+E, LFTs, phosphate - 3 times a week * Once stable * Blood glucose, FBC, U+E, phosphate daily * LFTs weekly
48
What are the contents of a typical parenteral feed?
* 2000 Kcal: 50% fat, 50% carb * 10-14g nitrogen * Vitamins, minerals, trace elements * Combined with H2O
49
What are the complications of parenteral feeding?
* Line related * Pneumothorax/haemothorax * Cardiac arrhythmia * Line sepsis * Central venous thrombosis -\> PE or SVCO * Feed related * Villous atrophy of GIT * Electrolyte disturbances * Refeeding syndrome * Hypercapnoea from excessive CO2 production * Hyperglycaemia and reactive hypoglycaemia * Line sepsis: increased risk with TPN * Vitamin and mineral deficiencies
50
What is the definition of refeeding syndrome?
Life threatening metabolic complication of refeeding via any route after a prolonged period of starvation
51
What is the pathophysiology of refeeding syndrome?
* Low carbs induces a catabolic state with low insulin, fat and protein catabolism and depletion of intracellular phosphate * Refeeding causes increased insulin in response to carbs and a high cellular phosphate uptake * This leads to hypophsophataemia and: * Rhabdomyolysis * Respiratory insufficiency * Arrhythmias * Shock * Seizures
52
What chemical abnormalities are seen in refeeding syndrome?
Low potassium, low magnesium, low phosphate
53
Which patients are at risk of refeeding syndrome?
* Malignancy * Anorexia nervosa * Alcoholism * GI surgery * Starvation
54
How do you prevent and treat refeeding syndrome?
* Prevent: * Identify and monitor at risk patients * Liaise with dietician * Treat * Parenteral and oral phosphate supplementation * Treat complications

Surgery Finals (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions