Fluids Flashcards
What do you need to when you are asked to prescribe some fluids?
- History
a. How much have they been eating/drinking over past few days?
b. Clinical monitoring- fluid balance chart
c. Weight - Vital parameters
a. Temperature
b. BP
C. RR
d. Pulse
e. Cap refill
Trend over the past few days - Check lab results
a. FBC
b. U&e
c. Creatinine - Any extra sources of fluid loss?
e.g stomas, drains, nausea or vomiting and output from this.
Basically figure out any extra losses over maintanese
What are the two main fluid compartments?
Intracellular (70%) and extracellular (30%)
What is the extracellular fluid divide into?
Interstitial and Intravascular
What is starlings hypothesis?
Fluid movement due to filtration across the wall of a capillary is dependent on the balance between the hydrostatic pressure gradient and oncotic pressure gradient across the capillary.
What is the component of intracellular fluid?
High potassium concentration
Low sodium concentration
Intracellular solute concentrations remain more or less constant
What is extracellular fluid concentration?
High sodium concentration
Low potassium concentration
What is the maintenance requirements in an average healthy adult with no extra losses?
2 to 2.5l of fluid per day
e.g 1.5l to replace losses in urine and 500-800 ml in insensible losses
What is the routine maintenance of fluids, electrolytes and glucose per day?
25-30ml/kg/day of water
1mmol/kg/day each of sodium, chloride and potassium
50-100 g/day of glucose to limit starvation ketosis
How much urine does a health person lose?
1ml/kg/hour
so 1.5 to 2.5l a day
In fluid replacement, what should you aim for a minimum urine output?
0.5ml/kg/hour
Sweating results in loss of…
sodium
Diarrhoea/increased stoma output are sources of loss of
sodium, potassium and bicarbonate
Vomiting may lead to loss of
potassium, chloride and hydrogen ions
Electrolytes in sodium chloride 0.9%
Na: 154 Cl: 154 K+: Nil Lactate: nil Calcium: nil glucose: nil
Electrolytes in glucose 5%
All nil
except 50g/litre glucose
Electrolytes in hartmann (sodium lactate)
Na: 131 CL: 131 K: 5 Lactate: 29 Ca: 2 Glucose: nil
Electrolytes in NaCL 0.18% &Glucose 4%
Na: 30 Cl: 30 K: nil lactate: nil calcium: nil Glucose: 40g/litre
Electrolytes in gelofusine
Na: 154 Cl: 12 K: nil lactate: nil calcium: nil glucose: nil
If someone is hypovolaemic, why might their BP be normal?
Compensation secondary to peripheral vasoconstriction (may show increase cap refill time).
Check orthostatic BP (when hypotension is absent, there may be dramatic drop inbox on standing and is a sensitive and early indicator of volume loss)
What are the benefits of crystalloids?
Cheap and effective solutions
Do not cause adverse immunological reactions
What can crystalloids be used for?
Maintenance and replacement fluids
How are crystalloids classed as?
Hypotonic- lowers serum osmolality and are not commonly used e.g. NaCL 0.45%
Hypertonic- increase plasma tonicity and draw fluid out of cells e.g. NaCL 3%, mannitol
Isotonic- fluid stays almost entirely within extracellular compartment e.g. NaCL 0.9%
How much does sodium chloride 0.9% distribute in each fluid compartment?
100% within extracellular fluid
25% will go in intravascular
75% is in interstitial fluid
How does glucose 5% distribute in each fluid department?
2/3 in intracellular fluid
1/3 goes to extracellular fluid
(only 80ml of 1000 would go into intravascular space- that is why it is not commonly used for resus in blood loss)
Examples of colloids
Blood
Dextran
Gelatin
Human albumin
Drawbacks of colloid
Higher cost
Risk of anaphylactoid and anaphylaxis
What is the colloid distribution in fluid compartments?
1000ml of human albumin compartment
100% stays in intravscular compartment
What to use- colloids vs crystalloid in resus?
Crystalloids cause initial expansion within vessels then redistribute.
SR has shown no difference between the use of colloid and crystalloid. However, from practice use, crystalloids are more available and cheaper so use them first.
Nice guidelines:
Use crystalloid containing Na+ in the range of 131-154 (so sodium chloride 0.9%)
Human albumin solution 4-5% can be considered for fluid resuscitation only in patients with severe sepsis. Note: human albumin solution 20% should not be used as it is hyperoncotic and rapid administration in fluid resuscitation scenarios can lead to rapid volume expansion and cardiac failure.
What is distributive shock?
- Results in relative hypovolaemia
Causes include: sepsis, anaphylaxis and neurogenic shock
What is hypovolaemic shock?
Most common form
Causes include haemorrhage, burns or any cause of substantial fluid loss
How is shock severity graded?
1-4
What is shock severity 1?
15%- 750ml volume lost
Mild resting tachy, slight delayed cap refill at 3 seconds (10% volume loss)
What is shock severity 2?
15-30% loss
750-1000ml
Cool peripheries, tachycardia, decrease pulse pressure, delayed cap refill (5 seconds)
May have catecholamine driven increase in diastolic BP and some anxiety
What is shock severity 3?
30-40%
1500-2000ml
Marked tachycardia and tachypnoea, decreased systolic BP
Very narrow pulse pressure, oliguria, low volume pulse, postural drop of 20-30mmHg and confusion/agitation
What is shock severity 4?
40-50%
2000-2500ml
Low GCS or unconscious, minimal or no urine output
Thready pulse, very tachycardiac, very low BP, cold skin
What are the signs that a patient may need urgent fluid resus?
Systolic blood pressure less than 100 mmHg
Heart rate is more than 90 beats per minute
Capillary refill time more than 2 seconds or peripheries are cold to touch
Respiratory rate more than 20 breaths per minute
National Early Warning Score (NEWS2) is 5 or more
Passive leg raising suggests fluid responsiveness
What is the passive leg raise for?
thought to mimic the administration of a fluid bolus by redirecting blood from the lower limbs to the heart (i.e. increased pre-load). This auto-transfusion of blood has been shown to increase cardiac output in patients’ who are fluid depleted. Therefore, the test is used to predict which patients are most likely to respond to administration of a fluid bolus.
One minute after performing the PLR manoeuvre the patient’s heart rate, blood pressure and stroke volume variance should be checked. After returning the patient to their original position, their observations should return to baseline pre-test values.
Sodium chloride 0.9% in large volumes may result in…
Hypercholaraemic acidosis
What is the rate for IV fluid resus
500ml of a crystalloid solution in the range of 130-154 mmol/l (e.g. sodium chloride 0.9%) administered over less than 15 min
Any resus fluid are IN ADDITION to calculated maintenance fluid requirements
What types of fluid regimen are there?
resus
maintenance
replacement
What are the complications of fluid overload?
- Dilutional hyponatraemia- treat with fluid restriction
2. Pulmonary oedema:
How to treat fluid overload?
Stop intravenous fluids: this is essential to avoid further deterioration.
Furosemide: can be given as a bolus or infusion. It causes a diuresis and venodilation.
Sublingual nitrate: causes a reduction in preload, the effects of which can be seen within five minutes.
Intravenous nitrate: provides an excellent and titratable pre- and after-load reduction. BP monitoring is essential with this intervention, as hypotension is an indication to stop the infusion.
Continuous positive airway pressure ventilation: has been shown to improve gas exchange by recruiting collapsed alveoli and redistributing excess fluid into the interstitial and intravascular compartments. It reduces pre- and after-load although this measure is usually only carried out by critical or coronary care units.
What should you consider when picking a fluid?
4D’s
- Correct drug?
- Correct dose and rate of administration?
- Duration and review date documented?
- De-escalation- when to STOP parental fluid prescription been document?
