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