Fluid Balance Flashcards
What is the average percetange of total body weight of body water content of an adult male?
60% body water
What is the average body water percentage in a female adult?
approx 50%
What is the total body water of a 70 kg man?
40 L
What proportion of total body water is found in the intracellular compartment?
2/3rd
What volume of TBW is found in the intracellular compartment in a 70 kg man?
25 L
What volume of TBW is found in the extracellular fluid in a 70 kg man?
15L (1/3rd)
What volume of TBW is found in plasma of a 70 kg man?
3L
What proportion of TBW is found in the ECF?
1/3rd
What are the major electrolyte characteristics of ECF?
- Major cation: Na+
- Major anion: Cl–
What are the major electrolytes in ICF?
- Low Na+ and Cl–
- Major cation: K+
- Major anion: PO42–
What is the average fluid intake per day?
2500 ml
What makes up total fluid intake in terms of sources of intake?
- Metabolism - 10%
- Foods - 30%
- Beverages - 60%
What makes up fluid output in terms of sources of fluid output?
- Faeces - 4%
- Sweat - 8%
- Insensible loss - 28%
- Urine - 60%
What happens to cells if someone becomes dehydrated?
Water moves out of cells to balance the now more concentrated ECF, causing cells to shrink
What are features of dehydration?
- Decreased urine output
- Decreased skin turgor
- Dry mouth
- Dry, flushed skin
If you gave 1 L water with 5% glucose, how would it distribute between compartments?
Distributed evenly between compartments
If you gave 1L of 0.9% saline, how would it distribute between compartments?
Would stay in the ECF, due to sodium being kept out of the cells
If you were to give 1L colloid, how would fluid be distributed between the different compartments?
Would stay in the vascular space
What are colloid solutions?
Solutions which contain larger insoluble molecules, such as gelatin; blood itself is a colloid. Colloids tend to remain in the vascular space
What is a crysalloid solution?
Aqueous solutions of mineral salts or other water-soluble molecules.
Which fluid type is more effective as a resus fluid?
Colloid - but associated with other complications so not often used
What are the 5 R’s of fluid management?
- Resusciation
- Replacement
- Redistribution
- Routine maintenance
- Reassessment
How would you manage someone if you thought they required resus fluids?
500 mls crystalloid, then reassess using ABCDE
What is hypotonic hydration?
Water intoxication
Tonicity of the water is less than ICF, meaning that fluid shifts into the cell, causing the cells to swell.
What can be consequences of hypotonic hydration?
- Cerebral oedema
- Nausea
- Vomiting
- Muscular cramping
What is oedema?
Accumulation of interstitial fluid
What is the physiology behind the development of oedema?
Due to anything that increases flow of fluid out of the blood or hinders its return
- Blood pressure
- Capillary permeability - usually inflammation
- Incompetent venous valves
- Localized blood vessel blockage
- Congestive heart failure
- Hypertension
- Blood volume
- Hypoalbuminaemia
- Blocked lymph vessels
What is the electrolyte composition of 0.9% saline?
- Na+ 154 mmol/L
- Cl- 154 mmol/L
What is the electrolyte composition of saline 0.18%/Glucose 4%?
- Na+ 31 mmol/L
- Cl- 31 mmol/L
- Glucose - 40g/l
What is the electrolyte composition of Hartmann’s solution?
- Na+ 131 mmol/L
- Cl- 112 mmol/L
- K+ 5 mmol/L
- HCO3- 29 mmol/L
- Ca2+ 4 mmol/L
If you had given someone 2 L of resus fluid, and they were still shocked, what would you do?
Seek expert advice
If someone, after being given an initial bolus of 500 ml resus fluid, was still shocked, what would you do?
Give another 250-500ml, then reassess
How would you asses whether someone needs fluid resuscitation?
Assess volume status based on examination, trends and context
- BP
- PR
- RR
- Cold peripheries
What clinical indicators might indicate that someone is in need of fluid resus?
- BP <100mmHg
- HR >90
- Cap refill > 2s
- Cold peripheries
- RR >20
- Positive leg raise test
If someone did not require fluid resus, how would you assess whether they needed IV maintenance fluids prescribed?
Calculate fluid and electrolyte requirements, then determine if they can maintain this orally
If someone did not need fluid resus, however required fluids and was deemed to be unable to mainatin fluid and electrolyte balance orally, what would your next step be?
Assess fluid and electrolyte needs, Based on:
- History - previous intake, abnormal losses, co-morbidities
- Clinical exam - Pulse, BP, Cap refill, JVP, post. hypotension, oedema
- Clinical monitoring - NEWS, fluid balance, weight
- Bloods - FBC, U+E’s, Creatinine, Urea
How would you determine whether you needed to give replacement fluids or routine mainatenance fluids?
Determine if complex fluid or electrolyte replacement or abnormal distribution issues:
- Abnormal losses
- Ongoing losses
- Existing deficits or excesses
What are the normal daily fluid requirments of an adult?
1-1.25mls/kg/hr
or
25-30 mls/kg/24hr
What is the daily electrolyte requirements for and adult?
- Na<strong>+</strong> - 1-2 mmol/kg/day
- K+ - 1 mmol/kg/day
- Cl- - 1 mmol/kg/day
What are daily glucose requirements for adults?
50-100 g/day
What do you need to check for when thinking about replacement fluids?
Check for
- Dehydration
- Hypo/hyperkalaemia
- Fluid overload
If any present, add or subtract deficits or excesses from daily maintenance
If there are no current existing abnormal fluid +/- electrolyte deficits or excesses, what would you want to assess for before prescribing fluids?
Check if there are any ongoing/predicted abnormal fluid or electrolyte losses
What are sources of abnormal fluid or electrolyte loss?
- Vomiting
- Biliary drainage
- High/low ileal stoma loss
- Diarrhoea/colostomy loss
- Ongoing blood loss
- Sweating/fever/dehydration
- Pancreatic/jejunal fistula/stoma
- Urinary loss
What are complex issues with fluid replacement that need expert advice?
- Gross oedema
- Severe sepsis
- Hypo/hypernatraemia
- Renal/liver/cardiac impairment
If someone did have ongoing abnormal fluid or electrolyte losses, how would you manage that?
Prescribe routine maintenance plus additional fluid and electrolyte to replace measured abnromal ongoing losses
What are 3rd space losses?
Tissue oedema - It is unseen and occurs with any tissue damage be it trauma, elective surgery or serious illness. Third space loss is not lost but redistributed.
What is the difference between shock and dehydration?
Shock refers to intravascular loss, whereas dehydration is loss of TBW:
- Loss of 20mls/kg from you intravascular space is >25% loss of circulating fluid volume.
- Loss of 20mls/kg from your total body water represents about 3% of your total body water
What is the definition of shock?
Failure of delivery of oxygen (and nutrients) to vital organs. Leads to rapid onset of tissue hypoxia and acidosis
How would you calculate fluids for someone who is obese?
Base calculations on ideal body weight
What should you do if patients have received IV fluids containing chloride concentrations greater than 120 mmol/l?
Monitor their serum chloride concentration daily
When would you consider givign blood as a resus fluid?
Only if ongoing losses and Hb less than 100 or if ongoing tissue ischamia, eg angina. Otherwise consider if Hb less than 80
When would you consider calling for help if someone was being given resus fluids?
>40 ml/kg
Describe the steps you would take to determining what fluid to prescribe an individual fluids?
- Do they need resus fluids?
- What are their fluid and electrolyte needs?
- Can they eat/drink?
- Does the patient have electrolyte excess/deficit?
- Does the patient have ongoing loss?
- Does the patient have redistribution/complex issues?
What fluids are best for using in a resus situation?
- NaCl 0.9%
- Hartmann’s solution - more appropriate if vomiting etc.
What are examples of maintence fluid regimens?
- Sodium chloride 0.9% (Normal saline)
- Hartmann’s solution
- Sodium chloride 0.18% / Glucose 4%
- 5% Dextrose
What fluids are only used as maintenance fluid regimens?
Both hypotonic
- Sodium chloride 0.18% / Glucose 4%
- 5% Dextrose
Why is it important to consider the spplementation of glucose in maintence fluid regimens?
To try to prevent hypoglycaemic ketosis
How would you calculate the electrolyte requirements of an individual for 24 hrs?
Na2+/K+ requirement = Weight x 1 mmol (+/- deficit excess from losses/gains)
How would you estimate electrolyte losses for particular fluid types - e.g. diarrhoea, vomiting etc.?
Use guidelines for average losses based on loss type e.g. vomit, urinary etc.
What is the maximum volume of fluid you should give to a 70kg man in one day?
70kg x 30ml = 2100 mls/day
Divide by 24 to get hourly rate
How much sodium would you give a 70kg man in one day who had no ongoing/abnormal losses or complex issues?
70kg x 1 mmol/kg = 70 mmol sodium/day
What test could you use to assess fluid responsiveness in a patient?
Passive leg raising - It is best undertaken with the patient initially semi-recumbent and then tilting the entire bed through 45°. Alternatively it can be done by lying the patient flat and passively raising their legs to greater than 45°.
- If, at 30–90 seconds, the are signs of haemodynamic improvementt - indicates volume replacement may be required.
- Patient condition deteriorates (in particular breathlessness) - indicates that the patient may be fluid overloaded
Is Hartmann’s good as a maintenance fluid?
No - over a 24 hour period you would give 3 times as much sodium and not enough potassium as required
What metabolic complication can occur when using saline as an IV fluid?
Hyperchloraemic metabolic acidosis
What effect can too saline have on the kidneys?
Cause renal vasoconstriction
Why is a dextrose-saline solution good for using as maintenance fluids?
If given at correct rate for patients weight - contains approximately correct amount of sodium for 24 hours
How would you calculate overall fluid requirements?
Maintenance fluids + replacement of fluid losses
Under what circumstances would you consider giving maintenance fluids instead of encouraging oral/ng fluid intake?
Only if the patient can’t drink enough
When calculating maintenance fluids, what 3 things would you tant to calculate in terms of quantity given before calulating rate of administration?
24 hour requirements for:
- Water - 1-1.25 ml/kg/hr or 25-30ml/kg/24hrs
- Sodium - 1 mmol/kg/24hrs
- Potassium - 1mmol/kg/24hrs
Calculate the following requirements in 24 hours for a 70kg patient:
- H2O
- K+
- Na2+
- Glucose
- Water (25-30ml/kg/24hrs) = 1680 - 2100 ml/24hrs
- K+ (1 mmol/kg/24hrs) = 70 mmol/24hrs
- Na2+ (1mmol/kg/24hrs) = 70 mmol/24hrs
- 50-100g/L glucose
Why do individuals need 50-100g/day of glucose?
To avoid starvation ketosis
When prescribing fluids to rail or elderly individuals or those with renal failure, what range for water replacement should you use?
What bloods should you always check before prescribing fluids?
U+E’s
If a patient is drinking some fluids, but not enough, how would you approach prescribiing maintenance fluids?
Check fluid baalance chart, and top up based on remaining deficit
Why should you not use maintenance regimens to correct plasma or blood loss?
Could result in dangerous hyponatraemia
What are indicators that someone may need urgent fluid resuscitation?
- SBP < 100 mmHg
- HR > 90 bpm
- CRT >2 seconds or peripheries are cold to touch
- RR > 20 bpm
- NEWS is 5 or more
- Passive leg raising suggests fluid responsiveness.
What should you replace blood loss with?
Blood
How would you determine pre-existing fluid/electrolyte deficit?
- History
- Observations
- Hydration status examination
- Fluid balance charts
- U+E’s
What is important to remember about U+E’s in terms of what it represents from a fluid and electrolyte point of view?
Only represents plasma concentrations - does not give an idea of whole body stores
If you gave someone a fluid bolus and they responded fully, what would be your next step?
Maintenance fluids
When should you take care when giving fluid boluses?
When individual has clinical features of HF
Why can K+ increase following surgery?
Due to excessive cell lysis
What fluids would you consider giving in sepsis?
Crystalloid
How would you treat fluid overload from fluid therapy in someone with HF?
- Fluid restrict
- Frusemide
- Low sodium diet
- Daily weight
What two clinical pictures do you need to consider in someone with HF and a low SBP and urine output?
- Acutal dehydration - are they fluid deplete?
- LVF and overload - LVF is worsened by fluid overload
What would you need to consider in terms of fluid management in someone with liver failure?
Excess Na+ could cause ascites - consider giving 5% dextrose only
What should you avoid giving in terms of fluid therapy in someone with an AKI?
K+
What should you avoid giving someone with CKD in terms of fluid therapy?
- Excess fluids, Na+ and K+
- Avoid hartmann’s - contains lactate
What must you give to an alcoholic before giving any dextrose fluid replacement?
Pabrinex - otherwise may precipitate korsakoffs syndrome
What fluid therapy would you prescribe in someone with a brain haemorrhage?
Saline - dextrose causes osmotic haematoma swelling
How does hyerchloraemic metabolic acidosis cause renal injury, salt retention and reduced cardiac contractility?
Chloride causes renal vasoconstriction, thus decreasing GFR and exacerbating sodium retention. Acidosis causes decreased contractility, thus meaning that if treated with inotropes, the heart cannot pump as well and inotropes have less of an effect
What is the best clinical measure of fluid balance?
Daily weights
How much salt is in 1 L of saline?
9g (36 packets of crisps)
What 4 questions do you need to address on the Scottish Daily IV/SC fluid prescription chart?
- Do they need fluid - are they hypovolaemic, euvolaemic or hypervolaemic?
- Why give fluid? - Maintenance, Replacement or Resuscitation
- How much do they need?
- What type of fluid?
What is the absolute maximum rate for delivering maintenance fluid?
100ml/hr - to avoid risk of hyponatraemia
What is the rough maintenance requirements/24hrs for indiviuals with a weight between 35-44kg?
1200 ml
What rate would you give 1200ml of maintenance fluid in someone who weighs between 35-44kg?
50 ml/hr
What volume of fluid would you give as maintenance fluid for someone between the weight of 45-54 kg over a 24 hr period?
1500ml
What rate would you give 1500 ml maintenance fluid to a patient that weighs between 45-54kg?
65 ml/hr
What volume of maintenance fluids would you give someone who weighed between 55-64kg?
1800 ml
What hourly rate would you give 1800ml of maintenance fluid to someone who weighed between 55-64kg?
75 ml/hr
What volume of maintenance fluid would you give someone in 24 hrs who was between the weights of 65-74 kg?
2100 ml
What hourly rate would you administer 2100ml of maintenance fluid to someone who was between the weights of 65-74kg?
85 ml/hr
What volume of maintenance fluid would you administer over a 24 hour period to someone who weighed >/= 75kg?
2400 ml
What houlry rate would you give someone 2400 ml who weighed >/=75kg?
100 ml/hr max
Based on maintenance fluids used in new scottish guidelines, why do all IV mainenance fluids need to be given via a volumetric pump?
They contain potassium
What maintenance fluid would you give someone based on new scottish guidelines?
0.18% NaCl/4% glucose/0.3% KCL (40 mmol/L KCl)
Based on new scottish guidelines, what maintenance fluid would you give someone if they had a K+ > 5 mmol/L?
0.18% NaCl/4% Glucose
What maintenance fluid should you use if someone has a Na+ of < 132 mmol/L?
Plasmalyte 148
What should patients who are fasting for >/= 6 hours for any reason be started on?
Maintenance fluid
How would you calculate replacement fluids?
Add up losses in the last 24 hours (e.g. blood, diarrhoea, drain output, fistulae etc.)
Is urine output a good guide for fluid replacement?
No - oliguria does not always require fluid therapy
What fluid would you use as replacement fluids?
Plasmalyte 148 - unless upper GI loss
According to new scottish guidelines, what fluid would you give instead of plasmalyte 148 as replacement fluids for upper GI losses?
0.9% saline with KCL as these patients will be hypochloraemic
How is plasmalyte 148 delivered?
By gravity or volumetric pump
According to new scottish fluid guidelines, what fluid should be used for fluid resuscitation?
Plasmalyte 148 - 250-500ml over 5-15 mins
What is important to do following the administration of every bag of fluid given to a patient?
Stop and review
According to new scottish guidlines, name the types of fluids used for the following situations:
- Resuscitation
- Replacement
- Maintenance
- Resuscitation - Plasmalyte 148
- Replacement - Plasmalyte 148, unless GI losses
- Maintenance - 0.18%/4% Glucose/0.3% KCl (no KCL if K+ > 5)
What are the concentrations of the following in Plasmalyte 148:
- Na+
- K+
- Mg+
- Cl-
- Na+ - 140
- K+ - 5.0
- Mg++ - 1.5
- Cl- - 98
