Fluids Flashcards
What is Total Body Water as a percentage in Males and Females?
63% of Lean Body Weight in Men
52% of Lean Body Weight in Women
In a 70kg man, how much is their Total Body Water?
45L
How is total body water divided into extracellular/intracellular fluids?
Intracellular = 2/3 Extracellular = 1/3
Under normal circumstances, what should daily fluid intake be?
2400ml - Drink 1500ml, Food 500ml, Metabolism 400ml
Under normal circumstances, what should daily fluid output be?
2400ml - Urine 1500ml, Insensible Loss 900ml
What are some symptoms of Volume Depletion?
Evidence of Fluid Loss Thirst, Syncope, Reduced Urine Output Resting Tachycardia Postural Hypotension Reduced JVP Prolonged CRT Dry Mouth Increased Skin Turgor
What are some symptoms of Volume Overload?
Background of relevant disease Symptoms of volume excess Peripheral/Sacral oedema Increased JVP Bibasal inspiratory crackles Third Heart Sound
Why is dextrose a poor choice of fluid for acute BP control?
The glucose is quickly metabolised leaving water, which distributes evenly across all compartments
What are Colloids?
Fluids that contain large insoluble molecules
Name an example of a Colloid
Albumin
Gelofusine
What are Crystalloids?
Fluids with mineral salts or other water soluble molecules
Name some Isotonic Crystalloid solutions
Saline - 0.9% NaCl
Hartmans - NaCl, KCl, CaCl
Name a Hypotonic Crystalloid Solution
Dextrose 5%
What is the 4-2-1 rule for maintenance fluid application?
4ml/kg/h for the first 10kg of lean body mass
2ml/kg/h for the second 10kg of lean body mass
1ml/kg/h for the remaining lean body mass
Give some examples of when IV fluid prescription would be appropriate
Patient is NBM such as prior to surgery
Pt is vomiting or has severe diarrhoea
Pt is hypovolaemic as a result of blood loss
What are the 5 ‘Rs’ of fluid prescription?
Resuscitation Routine Maintenance Replacement Redistribution Reassessment
What are some reasons why fluid prescription is necessary?
Resuscitation
Maintenance
Replacement
What are some important factors to consider before prescription of fluids?
Weight and size of patient
Co-morbidities, particularly HF/CKD
Reason for admission
Recent U&E
Why do septic patients need significant volumes of fluid?
Sepsis leads to increased vascular permeability, meaning more vascular fluid enters tissues. Larger volumes must be given to maintain intra-vascular volume
If patients clinically improve, what happens to their fluid excess?
They correct themselves by urinating out the excess fluid
What are the daily electrolyte requirements?
Water - 25mL/kg
Na+ - 1mmol/kg
K+ - 1mmol/kg
Glucose - 50g
What rule can be used to calculate hourly fluid requirements for anaesthatised patients?
4-2-1 rule
What is the 4-2-1 rule?
For maintenance fluids, per hour a patient needs:
4ml/kg for the first 10kg of Lean Body Weight
2ml/kg for the next 10kg of Lean Body Weight
1ml/kg for the remainder of Lean Body Weight
What are the hourly fluid requirements of a 70kg man while anaesthatised?
4ml * 10 = 40ml
2ml * 10 = 20ml
1ml * 50 = 50ml
Total = 40+20+50 = 110ml/h
