Fluid Therapy & JVP Flashcards
dWhat 2 major groups can IV fluids be categorised into?
1) Crystalloids
2) Colloids
What are crystalloids? Give 3 examples
Solutions of small molecules in water
- sodium chloride
- Hartmann’s
- dextrose
What are colloids?
Give 2 examples
Solutions of larger organic molecules.
- albumin
- Gelofusine
Name 4 commonly used fluids
1) Sodium chloride 0.9% (normal saline)
2) Hartmann’s solution
3) Sodium chloride 0.18% / glucose 4%
4) 5% dextrose
What are isotonic solutions?
IV fluids that have a similar concentration of dissolved particles as blood.
What are hypertonic solutions?
Hypertonic fluids contain a higher concentration of solute compared to plasma and interstitial fluid; this creates an osmotic gradient and drives fluid from the interstitial space into the intravascular space.
What is a hypotonic solution?
A hypotonic fluid is a solution with a lower concentration of electrolytes than body plasma.
Give an example of a hypotonic solution
0.45% sodium chloride
Is normal saline iso/hypo/hypertonic?
Isotonic
Is Hartmann’s solution iso/hypo/hypertonic?
Isotonic
Is 5% dextrose iso/hypo/hypertonic?
Hypotonic
What does 5% dextrose solution contain?
Only dextrose and water
What is dextrose?
The D-isomer of glucose
Does 5% dextrose have a role in fluid resuscitation?
No - only maintenance.
What is the main advantage of 5% dextrose?
Being able to maintain hydration without administering an excess of electrolytes, and it can also be prescribed with supplementary potassium if required.
Does 5% dextrose have any substantial calorific or nutritional value?
No
What does normal saline contain?
Na+, Cl- and water.
Indications for normal saline?
Can be used in both resuscitation and maintenance regimes.
Potassium can be added to the solution too, aiding in electrolyte management.
Why should normal saline not be used as a lone fluid maintenance?
as excessive saline replacement can result in a hyperchloraemic acidosis.
What doe Hartmann’s solution contain?
Na+, Cl–, K+, HCO3– (as lactate), Ca2 and water.
Indications for Hartmann’s solution?
Similar to Normal Saline, it distributes in the intra-vascular and interstitial spaces, making it useful for both resuscitation and fluid maintenance.
How does Hartmann’s differ from normal saline?
1) Hartmann’s solution is considered to be more “physiological” than Normal Saline as it contains other electrolytes in concentrations similar to plasma.
2) It also contains lactate, which it uses to generate alkalising HCO3– ions.
Why should there should be a guarded use of lactate as a marker of acidosis if patients have received Hartmann’s solution?
As Hartmann’s contains lactate anions –> can interfere with the usefulness of serial lactate measurements.
Aim os using colloids?
Colloids are solutions containing proteins with large molecular weights, aiming to maintain a high plasma oncotic pressure to keep fluid within the intravascular compartment (in theory an advantage during fluid resuscitation).
However, clinical trials have shown their limited benefit in resuscitation*, and they also come with a small risk of anaphylaxis.
Indications for human albumin solution (HAS)?
HAS is still routinely used in patients who are unable to produce sufficient protein (e.g. decompensating liver disease). By temporarily increasing the plasma oncotic pressures, HAS allows intravascular volumes to be maintained.
When prescribing IV fluids, what are the 5 Rs that should be remembered?
1) resuscitation
2) routine maintenance
3) replacement
4) redistribution
5) reassessment
What are the general key considerations when prescribing fluids?
1) Is the aim of the fluid for resuscitation, maintenance, or replacement?
2) What is the weight and size of the patient?
3) Are there any co-morbidities present that are important to consider, such as heart failure or chronic kidney disease?
4) What is their underlying reason for admission? (After some operations, patients are deliberately run “on the dry side”, whilst septic patients or patients in bowel obstruction will need aggressive fluid prescribing).
5) What were their most recent electrolytes?
What are the 3 main reasons for fluid prescription?
1) resuscitation
2) maintenance
3) replacement
What is the distribution of fluid intracellularly vs extracellularly?
Around 2/3 distributes in to the intracellular fluid and the remaining 1/3 distributes in to the extracellular fluid.
Of that fluid in the extracellular space, what is the distribution between intravascular and interstitium?
Of that fluid in the extracellular space, around 1/5th stays in the intravascular space and 4/5th of this is found in the interstitium, with a small proportion in the transcellular space.
What does ‘fluid resuscitate’ mean?
Improving tissue perfusion by raising the intravascular volume.
If the aim is to fluid resus a patient, where is it important that fluids stay?
Within the intravascular compartment - this concept will help to understand why different fluids are available and for what purpose they might be used.
What are fluid losses from non-urine sources called?
Insensible losses
How are insensible losses affected in unwell patients?
Insensible losses will rise in unwell patients, who may be febrile, tachypnoeic, or having increased bowel output.
These factors should be taken into account when deciding how much fluid a patients needs replacing.
What clinical signs may you be looking for in a dehydrated patient?
1) Dry mucous membranes and reduced skin turgor
2) Decreasing urine output (should target >0.5 ml/kg/hr)
3) Orthostatic hypotension
4) In worsening stages:
- increased CRT
- tachycardia
- low BP
What clinical signs may you be looking for in a fluid overloaded patient?
1) raised JVP
2) peripheral or sacral oedema
3) pulmonary oedema
What is the suggested daily requirements for:
a) water
b) Na+
c) K+
d) glucose
per day when prescribing fluids?
a) 25 mL/kg/day
b) 1.0 mmol/kg/day
c) 1.0 mmol/kg/day
4) 50g/day
In a 70kg healthy male, you need to precribe fluids over 24h that provide how much:
a) water
b) Na+
c) K+
d) glucose
a) 1750ml (75 x 25 mL/kg/day)
b) 70 mmol
c) 70 mmol
d) 50g/day
Give an example of a typical fluid maintenance regimen in a healthy 70kg male
1st bag:
- 500mL of 0.9% saline with 20mmol/L K+ to be run over 8 hours
- This provides all of their Na+, around 1/3rd of their K+, and a quarter of their water
2nd bag:
- 1L of 5% dextrose with 20mmol/L K+ to run over 8 hours
- This provides a further 1/3rd of their K+, and half of their water, as well as glucose
3rd bag:
- 500mL of 5% dextrose with 20mmol/L K+ to run over 8 hours
- This provides the remaining 1/3rd of their K+, and a quarter of their water, as well as glucose
What is a reduced urine output defined as?
<0.5ml/kg/hour
Management of any reduced urine output (<0.5ml/kg/hr)?
Should be managed aggressively, giving a fluid challenge and the clinical parameters (including urine output) subsequently rechecked (also ensuring any catheter is not blocked or patient not retaining urine).
What should a fluid challenge in a patient with reduced urine output consist of?
The fluid challenge should be either 250ml or 500ml over 15-30mins, depending on the patient’s size and co-morbidities.
For example a 120kg 30yr male may need >500 ml to make any difference to their intravascular volume, whereas in a frail 80yr lady with ischaemic heart disease and renal disease, 250ml may be more appropriate.
When prescribing fluids you should assess any excess losses.
What 5 things should be look at?
1) Are there any third-space losses?
2) Is there a diuresis (increased or excessive production of urine)?
3) Is the patient tachypnoeic or febrile ?
4) Is the patient passing more stool than usual (or high stoma output)?
5) Are they losing electrolyte-rich fluid?
What is a third space loss?
Third-space losses refer to fluid losses into spaces that are not visible, such as the bowel lumen (in bowel obstruction) or the retroperitoneum (as in pancreatitis).
