Fluids Tutorial

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اشترك في: الخميس إبريل 04, 2013 10:28 pm

Fluids Tutorial

مشاركةبواسطة دكتور كمال سيد » الأربعاء ديسمبر 16, 2015 6:44 pm

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.

How much fluid will you prescribe for this lady ?

2.5L - 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).

3.0L - 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.

4.0L 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.

2.0L – 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.

What fluid regimen will you prescribe for her?

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.

Would you like to add anything to the fluids, doctor?

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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Re: Fluids Tutorial

مشاركةبواسطة دكتور كمال سيد » الأربعاء ديسمبر 16, 2015 7:02 pm

Case 2 : Perioperative loss

Your registrar calls you to tell you about a 70kg female patient who had an anterior resection 6 hours ago. The registrar says there was intraoperative blood loss of 800ml and that 500ml of Hartmanns was given by the theatre anaesthetist. He says the patient has an abdominal drain in situ which has produced 300ml of blood, but has now stopped draining. He mentions that the patient was euvolaemic prior to the operation.

The registrar says the patient is to remain nil-by-mouth in case she needs to go back to theatre. He asks you to prescribe more fluid for the patient, who has had only 500ml of normal saline since the operation.

What's the first thing that you should do for this patient now?

Make sure you physically see the patient. Go to the bedside and examine the patient and check the blood results. Whenever taking a complex handover it is important to get as much information as possible. Speak to the nurse looking after the patient to see if they have any concerns, and speak to the patient / read the notes to find out if they have any important past medical history you should be aware of (eg heart or renal failure).
You go to see the patient who is alert but complaining of pain. You examine her and find her to be showing signs of hypovolaemia.

What are the clinical signs of hypovolaemia ?

There are a number of clinical signs and symptoms. They are summarised in the table below:

It is worth noting that although hypotension is an important sign, this patient may have a normal or even high blood pressure, as he is complaining of pain.
You notice that the patient has a catheter in situ. The nurse tells you that this was placed by the anaesthetist pre-operatively. The catheter bag contains 100ml of concentrated urine.

How much urine should have collected in the bag in the 6 hours since the operation? What could you do to confirm that the recorded urine output value of 100ml is correct?

The minimum acceptable urine output for adults with normal renal function is 0.5-1 ml/kg/hr. Below this the patient is likely to be in renal failure. In the last 6 hours this patient should have produced: 0.5 x 70 x 6 = 210ml minimum. If a patient has produced less than the minimum obligatory volume of urine this should prompt urgent intervention with a fluid challenge and senior input. However, it is a good idea to first check two things:

1. That the patient is not known to be in end stage renal failure and on dialysis– this could be a normal urine output for them! The place to look for this is in the notes, or ask the patient.

2. That the catheter bag has not simply been drained recently! Look at the fluid balance chart to check if there is any recorded urine output. In this case, the nurse tells you that she recently emptied the catheter bag, which contained 500ml of concentrated urine.
The patient tells you that she is still feeling very nauseous. She has a nasogastric tube in-situ, which has produced 300ml since the operation and is still producing large amounts of clear aspirate.

Which important electrolyte is commonly lost in vomit and NG aspirate?

Although many electrolytes are lost, the most problematic may be potassium. The loss of hydrochloric acid from the stomach may induce hypochloraemia and metabolic alkalosis. As a response to this, the kidneys increase the reabsorption of hydrogen ions from the tubules, at the expense of potassium which is exchanged and lost in the urine.

Bicarbonate is not usually lost from NG aspirate. More commonly it is lost in diarrhoea which may cause metabolic acidosis. The opposite is usually the case from NG losses.

Phosphate loss is not a common problem.

Sodium loss is not generally a problem with NG aspirate (see above).

The nurse asks you what volume of fluid the patient is likely to need over the next 24 hours.

Calculate the approximate fluid requirements for this patient, over the next 24 hrs.

This patient has clearly lost a lot of fluid, and a simple 3 L regimen is unlikely to be enough. Remember that when calculating fluid requirements you should try to account for previous losses and gains, present state of hydration, and anticipated future losses.
The easiest thing to do is make a table of inputs and outputs since the patient was last known to be euvolaemic:

As the patient was euvolaemic before the operation, we can calculate that at this point in time she is approximately 1000ml negative and this may explain her clinical signs of dehydration. Over the next 24 hours, if her NG output continues (in addition to urine output and insensible losses) we can anticipate fluid losses of approximately 3700ml, and as such we must replace this IV.

Therefore as the patient is currently in 1000ml negative balance with an anticipated future loss of 3700ml over the next 24hr, this would suggest that it would be necessary to replace at least 4700ml over the next 24hr.

As the patient is not known to have renal or cardiac failure it would seem reasonable to prescribe 5L (or more) of fluids over the coming 24 hours. However, the patient should have regular reassessment as the NG aspirate may reduce, or there may be third space losses to consider. This patient is also likely to have significant electrolyte dyscrasias, which should be carefully monitored and corrected as necessary.

You prescribe adequate replacement and maintenance fluids for the patient, and return regularly to review them. You also prescribe adequate analgesia and antiemetics. The patient's hydration improves and their pain settles. Everyone thinks you are a hero! But, just as you settle down in the mess for a well earned coffee, your on-call bleep chirps up

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Re: Fluids Tutorial

مشاركةبواسطة دكتور كمال سيد » الأربعاء ديسمبر 16, 2015 7:38 pm

Case 3 : Fluid overload

While on-call, you are bleeped to see an 82 year old man with known ischaemic heart disease, who was admitted a few hours ago with an episode of chest pain. The nurses looking after him tell you that he has been eating and drinking normally while in hospital, but they are concerned that he has dropped his blood pressure and become increasingly confused in the past 30 minutes.

On assessment you find him to be quite confused, with a blood pressure of 83/72 (baseline 115/90). He does not have a catheter in situ and his bed pad is dry.

How will you manage this situation?

Increasing confusion and a fall in blood pressure is potentially serious. You should recognise that this patient needs attention. In any such situation you should manage the patient following an ABC algorithm, involving senior help early if you feel you are out of your depth! In this case the patient's airway and breathing are normal, but on examination he looks dry...

You decide that the patient may benefit from a fluid challenge, to see if his blood pressure picks up with fluid repletion.

Which of the following would you give him:

250-500ml Normal Saline STAT or 250-500ml Volplex STAT - Either of these would make for a reasonable fluid challenge. The idea is to watch for a response while the fluid remains intravascular, and so it does not matter greatly weather colloid or crystalloid is used (although glucose is best avoided as it redistributes very quickly). Fluid challenge should be given as a stat dose rather than a slow infusion. NB : 'STAT' comes from the Latin 'statim', meaning 'immediately' .

1000ml Normal Saline over 2hrs and 1000ml Volplex over 2hrs - A fluid challenge is a quick bolus of a small amount of fluid to encourage a physiological response. This is too much fluid, given over too long. 500-1000ml Normal Saline over 1hr or 500-1000ml Volplex over 1hr in an unknown patient is likely to be too much fluid still. Only small amounts of fluid should be needed to lift the blood pressure. Using large amounts can lead to problems…

Before you can prescribe the fluids, your well-meaning SHO (who unfortunately had not read this tutorial) has given the patient a stat dose of 2L Volplex. The patient quickly becomes more unwell.

On examination he is now short of breath, with a respiratory rate of 35 and crackles are heard bi-basally. The oxygen saturation is 90 on 2L oxygen via nasal specs (baseline 98% on air) and his lips are slightly blue.

What has happened to the patient? How would you go about managing this acute situation? Write down what you would do, and what order you would do it in.

The patient has known ischaemic heart disease which may predispose to heart failure. Large intravenous boluses are dangerous in these patients, as they often lead to fluid overload and pulmonary oedema, as has happened here.
Acute heart failure with pulmonary oedema is an emergency. These patients will be very unwell. The patient should again be managed by an ABC algorithm.
Turn the oxygen up to 15L, and switch to a non-rebreathing mask. Stop the fluids! (don't forget to do this!) Call for help. The patient will need to be cared for in a monitored bed or transferred to HDU/ITU.
(intensive therapy unit - or - high dependency unit)

You bleep your registrar, who quickly arrives to help stabilise the patient. The registrar asks you to prescribe the ‘acute heart failure drugs’ on the chart, and asks you to keep a close eye on the patient's cardiac function.

Make a list of 4 drugs you might need to prescribe for this patient, and the ways in which you can further monitor the patient's cardiac function on the ward.
The exact drugs that are used to treat heart failure may vary from case to case.
: However, most patients in acute heart failure will require

Oxygen – remember this needs to be prescribed on the drug chart!

Diamorphine – not all patients will need this, but it acts as a pulmonary venodilator and relieves some of the backpressure from the heart.

Nitrates – are also vasodilators, although they work more by reducing the arterial tone so that the heart has to work less hard to pump blood forward.

Furosemide – This is a powerful and fast-acting loop diuretic which helps to remove the excess fluid by diuresis.

Although HDU/ITU is the ideal place to monitor cardiac function, some simple monitoring can be set up on the ward : Continuous or regular ECG monitoring. Regular blood pressure and heart rate monitoring. Catheterise the patient. Urine output is a good indicator of cardiac output. The patient should have a fluid balance chart started, if they do not already have one. Frequent weighing – Patients' weights should not fluctuate much day-to-day. If a patient gains a lot of weight over the course of the day or night, this may suggest that they are retaining fluid.

After a few hours, you manage to stabilise the patient and the registrar heads back to theatre. The nursing staff are very busy on a drug round, and sister asks if you could help out by replacing a cannula that has tissued and starting some maintenance fluids for a different patient. You haven't set up a drip for a while, so you nip to the doctors office to remind yourself of how to do it, by watching Module 5 of this tutorial.

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Re: Fluids Tutorial

مشاركةبواسطة دكتور كمال سيد » الأربعاء ديسمبر 16, 2015 8:19 pm

Module 4 Summary : Clinical Cases

Module 3 Summary : Prescribing

Module 2 Summary : Clinical Assessment

Module 1 Summary : Physiology

theory & practice

Module 5 : OSCE Video and Mark Sheet

Module 5 : OSCE Video and Mark Sheet


Welcome to module 5

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Re: Fluids Tutorial

مشاركةبواسطة دكتور كمال سيد » الأربعاء ديسمبر 16, 2015 8:41 pm

Case 3 : Fluid overload

Case 2 : Perioperative loss

Case 1 : Maintenance fluids

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