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Module 4 : Case Scenarios

 

 

Case 1 : Maintenance fluids

 

A 75 year old lady weighing 70kg is admitted following a stroke. She has a dense left-sided hemiparesis. The A and E SHO has assessed her and found her to have an unsafe swallow. She is apyrexial and otherwise well. Your registrar asks you to make her ‘nil-by-mouth’ and prescribe maintenance fluids.

 

 

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  Test Yourself !  
   
  How much fluid will you prescribe for this lady ?

That's correct, well done!
 

2.5 L - We haven't been given any information about her insensible losses or urine output, but she is apyrexial and otherwise well so it is probably safe to assume these are normal in this instance. Therefore, assuming a fluid requirement of aprox 30ml/kg/day we could calculate that she needs at least 2100ml of fluid per day (see Physiology : Fluid balance in health to revise this).

 

3.0 L - Although she probably needs less than this, 3.0-3.5 L is usually very safe in an otherwise healthy person as unneeded fluid will be easily removed by the kidneys.

 

4.0 L is probably not necessary for maintenance. However, if you prescribe 4.0 L at a rate of 1L every 8-hours, this will continue to provide her with her required maintenance fluid if the operating list is running late, although it would be wise to reassess her first.

 

2.0 L – This is probably too little fluid and puts her at risk of dehydration. This is not ideal, especially before intrabdominal surgery as the risk of post-operative DVT is high.

 

Sorry, that's incorrect!
 

2.5 L - We haven't been given any information about her insensible losses or urine output, but she is apyrexial and otherwise well so it is probably safe to assume these are normal in this instance. Therefore, assuming a fluid requirement of aprox 30ml/kg/day we could calculate that she needs at least 2100ml of fluid per day (see Physiology : Fluid balance in health to revise this).

 

3.0 L - Although she probably needs less than this, 3.0-3.5 L is usually very safe in an otherwise healthy person as unneeded fluid will be easily removed by the kidneys.

 

4.0 L is probably not necessary for maintenance. However, if you prescribe 4.0 L at a rate of 1L every 8-hours, this will continue to provide her with her required maintenance fluid if the operating list is running late, although it would be wise to reassess her first.

 

2.0 L – This is probably too little fluid and puts her at risk of dehydration. This is not ideal, especially before intrabdominal surgery as the risk of post-operative DVT is high.

 

 

 

 

 

After assessing the patient and finding her to be euvolaemic, you decide to prescribe 3 litres of fluid over the next 24 hours. Her blood results show that her electrolytes are all within normal limits.

 

 

  Test Yourself !  
   
  What fluid regimen will you prescribe for her?

How did you do?
 

There is a degree of acceptable variation here. As she is euvolaemic with no electrolyte dyscrasias we can assume typical electrolyte and fluid losses will occur over the next 24 hours. As she is 70kg in weight, her sodium needs are 70-140 mmol/day. Ideally, she should be prescribed 1 L of Hartmanns solution, which contains 131mmol Na. However, for one day 1 L of Normal saline (contains 154 mmol) would be acceptable. The rest of the volume should be given as glucose solution, which does not contain further electrolytes. Suggested regimens : 1L 5% Glucose, 1L 0.9% Saline, 1L 5% Glucose (sequentially as '8-hourly bags') 1L 5% Glucose, 1L Hartmanns, 1L 5% Glucose (sequentially as '8-hourly bags')

 
 

 

 

 

The nurse who is giving the fluid bleeps you as you have left the ‘drugs to add’ and ‘dose to add’ column of the prescription blank. She would like to know if you wish to add anything to the fluid? The surgical registrar has not asked you to write her up for any pre-operative medication other than maintenance fluids.

 

 

  Test Yourself !  
   
  Would you like to add anything to the fluids, doctor?

How did you do?
 

As well as sodium, it is important to think about replacing potassium losses when prescribing maintenance fluids. As this patient is 70Kg she will need approximately 70 mmol of potassium replacement in 24 hours (often less will be enough). As most crystalloids are now available with potassium pre-added it can be practically difficult to give exactly the ideal amount. Bags tend to come with 20 or 40mmol pre added, so prescribing 20mmol per bag will make administration more practical. This would mean the patient would receive 60mmol of potassium in a glucose, saline, glucose regimen, and 45 mmol potassium in a glucose, Hartmanns, glucose regimen (because heartmanns is not available with extra potassium, although it contains 5mmol as standard). In fact, both of these regimens will probably provide adequate potassium for one day. However, it is vital to check blood results regularly to ensure the potassium level is not becoming deranged, as this can have fatal consequences if uncorrected!

 
 

 

 

 

You prescribe the fluids safely and legally on the drug chart and the patient undergoes her procedure without incident the following day. The registrar is pleased with you. He asks if you can give him a hand managing Case 2, a post-operative patient with significant fluid loss…

 

 

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