Intravenous Fluids

Objectives

  • Describe the distribution of Total Body Water intracellularly and extracellularly
  • Demonstrate awareness of the composition of the most common Crystalloids and how these distribute into the various body compartments
  • Classify Colloids by chemical structure and describe their clinical uses and drawbacks
  • Use this knowledge and understanding to select an IV fluid for use in various clinical scenarios

Crystalloids

Crystalloids are water-based solutions with added solutes (electrolytes or glucose). They differ in their composition, which determines their distribution throughout the body.

Click through the tabs to compare different crystalloids by content, pH and compartment distribution. It is important to note that glucose effectively becomes free body water (i.e. not limited to the extracellular space) and so is not suitable for fluid resuscitation. ‘Normal’ Saline and ‘Balanced’ Crystalloids (such as Plasmalyte) are retained in the extracellular spaces (in plasma and the interstitium) and so are much more suitable for fluid resuscitation. 

Normal Saline

5% Dextrose

Plasmalyte

Hartmann’s Solution

4% Glucose with 0.18% NaCl

Colloids

Colloids have been popular for their use as plasma volume expanders. This is because they are 100% retained within the intravascular space (at least initially). They are a crystalloid base with added colloid substance that does not freely diffuse across cell membranes. 

For various reasons, their use has fallen out of favour. However, you should be aware of their chemical classification and the pros and cons associated with each. 

Human Albumin Solution

Starches

Dextrans

Gelatins

Quiz

3
Created on By Anaestheasier

Intravenous Fluids

1 / 10

The extracellular fluid compartment makes up around a third of total body water. What proportion of this compartment is plasma?

2 / 10

Approximately how much of a 1L bag of 5% Glucose would be retained in the plasma?

3 / 10

If you wanted to select a fluid as a volume expander that would be 100% retained intravascularly for at least 2 hours, which of the following would be best used?

4 / 10

You are assisting in theatre for a long Maxillofacial case. Insensible losses are unlikely to be significantly raised. The patient is a 80kg female. Based on this information alone, what is likely to best represent her hourly maintenance fluid requirement?

5 / 10

Which of the following fluids will be most retained in the plasma?

6 / 10

Which of the following volumes best represents the Total Body Water of a 30-year-old average male of 70kg (BMI 23).

7 / 10

How is Plasmalyte buffered?

8 / 10

‘Normal Saline’ is 0.9% Sodium Chloride, equating to 9g/L. This gives it a roughly physiolgical osmolality. Which of these approximates normal physiological osmolality?

9 / 10

What is the estimated plasma volume of a 70kg male, assuming normal BMI?

10 / 10

Which of the following is not a side effect of IV Colloids?

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The average score is 83%

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