Fluid and Nutrition Management

Question 1

In the average person, what percentage weight does water contribute?

Answer 1

60%

Question 2

In the average person, what percentage body weight is Intracellular Fluid?

Answer 2

40%

Question 3

In the average person, what percentage body weight is Extracellular Fluid?

Answer 3

20%

Question 4

How can the Extracellular Compartment be further divided?

Answer 4

Intravascular (5%)

Extravascular/Interstitial (15%)

Question 5

How may fluid cross compartments?

Answer 5

Osmosis which depends on a solute gradient

Filtration which is the result of a hydrostatic pressure gradient

Question 6

Describe generally the electrolyte balance of the intracellular compartment

Answer 6

Low sodium

High Potassium

Question 7

Describe generally the electrolyte balance of the extracellular compartment

Answer 7

High sodium

Low potassium

Question 8

Compare the protein balances of the interstitial and the intravascular compartments of the extracellular compartment

Answer 8

Interstitial fluid has a very low protein balance

Question 9

What fluid(s) should be considered when trying to fill the intravascular compartment rapidly? Why?

Answer 9

Plasma Substitute or Blood
These fluids have a high colloid osmotic pressure and remain in the intravascular space in contrast to a crystalloid solution such as Hartmann’s which will distribute over the entire extracellular compartment, thus less would remain in the intravascular compartment

Question 10

What are the routes from which fluid is lost?

Which are termed ‘insensible losses’

Answer 10

Kidney
GI tract
Skin
Respiratory Tract

Skin and Resp tract are insensible

Question 11

Describe how many mL of fluid, mmol of Na+ and mmol of K+ are lost via the Kidney for a normal person in a 24 hour period.

Answer 11

2000mL
80-130mmol of Na+
60mmol of K+

Question 12

How many mL of fluid are lost each day via the faeces?

Answer 12

300mL

Question 13

How many mL of fluid are lost each day insensibly?

Answer 13

400mL

Question 14

Describe how surgery effects fluid loss

Answer 14

Surgery causes a stress response which leads to the release of ADH, catecholamines and activation of the RAAS, which results in oliguria and water retention.

Question 15

Describe the importance of assessing the patients state of hydration in spite of oliguria

Answer 15

Patient may be euvolaemic, unnecessary administration of fluids mat expand the blood volume and reduce haematocrit, overexpand the interstitial space, resulting in oedema and a salt load that the patient cannot excrete

Question 16

Explain the effect of surgery on potassium levels. Explain the basis for the recommendation that supplementary potassium may not be necessary in the first 48 hours post surgery or trauma

Answer 16

Potassium is released by damaged tissues, and may be further increased by blood transfusion (each unit of blood contains ~20mmol/L of potassium). If renal perfusion is poor and urine output sparse, the potassium will not be excreted and instead accumulates. This leads to hyperkalaemia and causes life-threatening arrhythmias.

Question 17

Unless they have a disorder affecting gastric emptying, up until what time mark can elective surgery patients continue clear fluids

Answer 17

2 hours

Question 18

Can a patients take carbohydrate drinks pre-operatively?

Answer 18

Yes, in fact, pre-op carbohydrate drinks around 2-3 hours before surgery can reduce anxiety and post-operative nausea and vomiting

Question 19

Describe a fluid regimen for a patient undergoing normal fluid loss

Answer 19

3L of 0.4% dextrose/0.18% saline with 20mmol/L of potassium added to each litre of fluid.

Question 20

How should a patient be monitored whilst on a fluid regimen?

Answer 20

Regular clinical assessment
Measurement of fluid losses
Daily weights
Regular blood samples

Question 21

Describe what fluids are described as special losses

Answer 21

Nasogastric aspirates
Losses of fistulas
Diarrhoea
Stomas

Question 22

As a rough guide, how would you manage the loss of gastric fluid?

Answer 22

Replace with equal volume of normal saline with extra potassium supplements

Question 23

As a rough guide, how would you manage losses from diarrhoea, ileostomy, small bowel fistulas and ileus?

Answer 23

Hartmanns solution

Question 24

Describe some signs of fluid deficit

Answer 24

Thirst
Dry mucous membranes
Loss of skin turgor
Tachycardia
Postural hypotension
Low JVP

These suggest a loss of between 5% and 15%