Fluids Flashcards
Types of fluid, Parental nutrition
Describe the different body fluid compartments within the body.
Fluid is stored within two main stores in the body:
Intracellular fluid (fluid within cells)
Extracellular fluid (outside of cells)
How much fluid is stored in the different body fluid compartments in the body?
Intracellular fluid (25L)
Extracellular fluids (15L)
- Plasma (3L)
- Interstitial fluid (12L)
Therefore total for about a 70kg person is 40L
What is the purpose of intracellular fluid store?
Give the cell structure in addition to facilitating metabolic processes that occur inside the cell
Describe the water balance within the body.
Usually kept relatively balanced in the body.
Intakes:
Fluids 1500mL
Food 800mL
Carbohydrate metabolism 300mL
Output:
Sensible losses: Urine 1500mL
Stools 200mL
Insensible losses (sweat or respiration): 900mL
What is meant by sensible losses?
Sensible fluid losses are losses that can be seen, felt or measured, such as urine output. Fluid loss through respiration cannot be easily measured and so is known as an insensible loss.
By understanding the daily fluid balance, how much fluid does an average person require?
25-30mL/kg/day
Which substances are able cross the cell membranes to different fluid compartments and which are unable to?
Water, small molecules are able to cross the semi-permeable cell membrane whereas larger colloidal substances and proteins are unable to move freely across from different fluid compartments.
The free movement of smaller molecules ensures that nutrients are able to move into cells and waste products can move out.
There is tight regulation of electrolytes contained within cells. Sodium and potassium concentrations for example are tightly regulated and controlled by a sodium/potassium Na+/K+ ATPase.
What does the Na+/K+ ATPase do?
For every ATP molecule, 3 sodium ions are exported from the cell whilst 2 potassium ions are imported.
What is the plasma, interstitial and intracellular concentration for sodium?
Plasma concentration: 142 mmol/L
Interstitial fluid: 145 mmol/L
Intracellular: 12 mmol/L
What is the plasma, interstitial and intracellular concentration for potassium?
Plasma concentration: 4 mmol/L
Interstitial fluid: 4.1 mmol/L
Intracellular: 150 mmol/L
What is the plasma, interstitial and intracellular concentration for chloride?
Plasma concentration: 103 mmol/L
Interstitial fluid: 113 mmol/L
Intracellular: 4 mmol/L
What is the plasma, interstitial and intracellular concentration for bicarbonate?
Plasma concentration: 25 mmol/L
Interstitial fluid: 27 mmol/L
Intracellular: 12 mmol/L
Which electrolyte is responsible for distribution of fluid?
Sodium increases the osmotic pressure, causing an increase in extravascular fluid (fluid retention).
What are some of the other fluids in the body that can have different concentrations of electrolytes?
Saliva
Gastric juice
Small intestine
Bile
Colon and diarrhoea
Sweat
Therefore if a patient has any condition that causes excess fluid loss of one of these stores you may have to adjust the electrolytes within the fluid bag.
What does maintaining fluid balance involve?
-Monitoring the fluid input and output
-That the daily normal requirements are maintained
-In addition to the normal requirements ensure that any additional losses are also compensated for.
What is the homeostatic system which ensures volume homeostasis?
The renin angiotensin system which is activated when there is a drop in renal perfusion. RAAS leads to the production of Angiotensin two which triggers the adrenal glands to release aldosterone and your pituitary gland to release antidiuretic hormone.
Aldosterone causes sodium and water retention and anti-diuretic hormone causes a reduction in the renal excretion of water and also increases thirst.
When may the RAAS not work as well?
After injury, illness or surgery
Which conditions would cause an reduction in fluid requirements?
Renal impairment
Liver impairment
Cardiac failure
Head injury (intracranial pressure increase)
Which conditions would cause an increase in fluid requirements?
Vomiting/diarrhoea
High output stomas (compensate for the loss of fluids)
Fistulas (connection of the gut)
Burns (skin is a barrier to fluid loss)
When is IV fluids indicated?
To correct acute losses of fluid or maintain homeostasis such as after:
Blood loss
Fluid loss
Maintain organ perfusion (inadequate perfusion of the kidney) and function
When there is a prolonged failure of oral intake (mucositis as a result of chemotherapy)
Excessive losses
Nil by mouth (maintain kidney function after anaesthesia)
Special case patients - burns, brain injury, children
What are some of the consequences if fluid balance is incorrect?
Electrolyte imbalance (and the clinical consequences of this- arrhythmias)
Peripheral oedema
Pulmonary oedema
Renal impairment
Acid/base disturbance
What are some of the clinical observations of fluid depletion?
Weight loss
Reduced blood pressure
Rapid, shallow breaths
Tachycardia, weak pulses - to maintain cardiac output
Reduced, concentrated urine
Reduced skin turgor (elasticity)
Thirst
Raised temperature
Increased capillary refill time
What needs to be reminded in terms of drug therapy and dehydration?
Some drugs may mask the symptoms of dehydration. Tachycardia is an example of dehydration, in a patient taking beta blockers they may not experience the symptoms of tachycardia when they are dehydrated.
What are some of the clinical observations of fluid overload?
Weight gain
Normal or raised blood pressure
Rapid, moist cough (pulmonary oedema)
Rapid pulse
Increased or decreased urine output
Oedematous skin
No change in thirst or temperature