Fluid Management

Question 1

Fluid distribution in compartments

Answer 1

EXTRACELLULAR:
5L in intravascular compartment
9L of interstitial fluid

INTRACELLULAR
28L in intracellular compartment (2/3)

Question 2

Fluid rate of maintenance?

Answer 2

30ml/kg/hr

Question 3

Na+ rate of maintenance?

Answer 3

1mmol/kg/day

Question 4

K+ rate of maintenance?

Answer 4

1mmol/kg/day

Question 5

Normaly urine output?

Answer 5

> 0.5ml/kg/hr

Question 6

When should Hartmann’s solution be used?

Answer 6

Most physiological fluid so good for replacing plasma loss e.g GI losses or surgery

Not good for normal maintenance alone (due to Na overload and low K)

Question 7

When should normal saline be used?

Answer 7

Less physiological than Hartmann’s but not than dextrose.

Risk: High Na load on kidneys. Hyperchloraemic acidosis risk, leading to renal vasocontriction

Question 8

When should 5% dextrose be used?

Answer 8

Given instead of pure water to maintain initial osmolarity.
Glucose has no role. Used for maintenance to give water when needed with no electrolytes. Not used for replacement of plasma/blood loss as it is not physiological

Question 9

When should colloids be used?

Answer 9

Given when you want to keep fluid in intravascular space, then creating an osmotic gradient.

Risk of anaphalaxis and renal failure

E.g. starches, gelatins and albumins

Question 10

Example of crystalloids?

Answer 10

Saline

PlasmaLyte

Question 11

Difference between crystalloids and colloids?

Answer 11

Crystalloids fluids such as normal saline typically have a balanced electrolyte composition and expand total extracellular volume. Crystalloids exert a significant hydrostatic effect on capillaries that may lead to extracellular fluid accumulation. This could lead to increased gastrointestinal wall edema, which may slow post-operative gastrointestinal recovery. It could also lead to significant pulmonary edema, especially in patients with underlying cardiac systolic dysfunction or renal disease. There is also a risk of hemodilution, which may occur with crystalloid administration.

Colloid solutions (broadly partitioned into synthetic fluids such as hetastarch and natural such as albumin) exert a high oncotic pressure and thus expand volume via oncotic drag. May (rarely) trigger an anaphylactic reaction. While low dose colloids typically preserve hematocrit and coagulation factor levels, there is a risk of abnormal hemostasis occurring if too much colloid is administered, especially synthetic colloids. Of note crystalloids are significantly cheaper than colloids.

Question 12

Only give maintenance fluids if…

Answer 12

patient cannot drink.

Oral/NG-tube fluids are safer

Question 13

Traditional maintenance fluids regime?

Answer 13

NB. the traditional regime = “1 salty + 2 sweet”:
1L saline 0.9% + 20mmol potassium chloride (over 8 hours) 1L dextrose 5% + 20mmol potassium chloride (over 8 hours) 1L dextrose 5% + 20mmol potassium chloride (over 8 hours)

Question 14

In extracellular fluid loss, provide what replacement fluids?

Answer 14

Extracellular fluid (e.g. D&V, NG aspirates, stomas, burns, pancreatitis): should be replaced by a fluid similar to extracellular fluid
– which is similar to plasma (e.g. Hartmann’s solution, or saline if Hartmann’s solution not available). But note, if a patient needs a lot of sodium-rich fluid resus, Hartmann’s solution is preferred to normal saline because it contains less chloride (too much chloride causes a hyperchloraemic acidosis).

Question 15

In dehydration, provide what replacement fluids?

Answer 15

Normal dehydration (e.g. pyrexia, poor intake): should be replaced by normal maintenance fluids (e.g. dextrose-saline).

Question 16

In blood loss, provide what replacement fluids?

Answer 16

Blood: should be replaced with blood. If the patient continues to bleed, they may also need other products e.g. FFP, platelets to
actually stop the bleeding rather than replace the lost red cells.

Question 17

Fluid resus to replace pre-existing deficits is done in _____ _____

Answer 17

Fluid resus to replace pre-existing deficits is done in STAT boluses

You must prescribe a bolus and then reassess the patient’s urine output and blood pressure after the bolus to guide further fluid resus

Question 18

How to perform a fluid challenge?

Answer 18

For acutely hypotensive patients when you are unsure of the exact cause, fluid challenge with 250-500ml crystalloid over 5 minutes.
Monitor response by BP, UO and JVP:
↘respond fully = just give maintenance fluids
↘respond and fall again = more fluids (adequate resus depends on patient but usually around 20ml/kg quickly)
↘no response = patient is either fluid overloaded (don’t give any more fluids) or very depleted (give lots of fluids)-assess clinically

(Cycle notes: 500mls in 15 mins)

Question 19

How is K given is fluids that don’t contain it (all except Hartmann’s)

Answer 19

Addition of 20 or 40mmol KCl-/ hr

Question 20

x% means..

Answer 20

x grams in 100mls

Question 21

atropine is a

Answer 21

PS antagonist to treat bradycardia

Question 22

Normal fluid losses

Answer 22

Resp: 350ml
Urine: 1.2-2L
Sweat: 400ml
Faeces: 200ml

Question 23

Ion loss in GI losses e.g. vomitting and diarrhoea?

Answer 23

Chlorine and potassium

Question 24

Dehydration –> Decrease GFR –>

Answer 24

Urea** and creatinine rise

Question 25

NBM?

Answer 25

Nil by mouth

Question 26

Synthetic colloids, name 2?

Answer 26

Gelatine based e.g. dextrans

Starch based e.g. gelofusin

Question 27

Human protein solutions, name 2 colloids?

Answer 27

Blood products e.g.platelets, packed red cells

Human albumin solution (HAS) - used in liver failure

Question 28

ECG signs of potassium excess?

Answer 28

Bradycardia
Flattened P waves
Prolonged PR interval
Wide QRS
Sloped ST segment
Tall t waves

Question 29

Causes of excessive Na loss?

Answer 29

Burns, fistulae and surgical drains

Question 30

Main aim of fluid resus?

Answer 30

Maintain blood pressure i.e. perfusion