Fluid Management Flashcards
What is meant by insensible losses? How does this compare to sensible fluid losses?
Water loses through skin and lungs.
Sensible fluid losses are through urine, sweat and faeces
State the amount of fluid in the 3 different compartments
Intracellular =25L
Extracellular = 15L
-Interstitial = 12L
-Plasma volume =3L
What is the main cation in intracellular and extracellular fluid?
Intracellular -K+
Extracellular -Na+
How much sodium and potassium is needed per day?
1-1.5mM/kg of Na
0.7-1mM/kg of k
What questions would you want to ask in a history to assess fluid balance of a patient ?
- are they thirsty? When did they last drink and how much?
- have they been profusely sweating ?
- Diarrhoea/ vomiting?
- urine frequency and colour
- diuretic medication
- past medical history of diabetes or chronic kidney disease
- confirm absence of hypervolaemia e.g. Swollen limbs, orthopnoea
What would you check when examining someone for their fluid balance status ?
- capillary refill time
- heart rate and blood pressure
- Dry mucous membranes ( mouth)
- dry axilla
Then ensure absence of hypervolaemia e.g. Raised JVP, basal lung crepitus, peripheral oedema
check weight - any fluctuations in short term can be due to fluid. check urine output/fluid balance. check U&Es
State some signs of dehydration
Low blood pressure , high heart rate Reduced capillary refil Sicken eyes Dry mouth Reduced skin turgidity Reduced ocular pressure
Why does the urea: creatinine ratio increase when dehydrated
Hypoperfusion of kidneys leads to less creatinine and urea being filtered and thus their levels rise
However urea is also further recycled to help conserve water and thus the urea levels rise more than creatinine
What could blood tests show if someone was hypovolaemic?
Hypernatremia Raised Hb , haemocrit Raised urea:creatinine ratio Raised lactate High osmolality
How is osmolality calculated
2(Na + K) + urea + glucose
What are the 3 reasons a patient may need fluids?
Routine maintainence
Resuscitation
Replacement and redistribution
What fluid and how much is given in fluid resuscitation?
500ml 0.9% NaCl or Hartmann over 15 mins (repeat until 2000ml given)
What ions need replacing in someone with a) vomiting and b) diarrhoea?
Vomiting - Na, H, K
Diarrhoea- Na, HCO3, K
What are the 3 types of fluids
Crystalloids
Colloids
Blood
How does 0.9% saline compare to hartmans?
both crystalloids
both contain Na and Cl
Hartmans also contains K and Ca - so don’t give hartmnas if hyperkalaemia
both their osmolarity is similar to ECF.
neither distribute to ICF
how much of hartmans and 0.9% saline stays within vasculature?
1/4, the rest will leave into the interstitium.
therefore if used in resuscitation need to bear this in mind i.e. 100ml blood loss requires 400ml 0.9%/hartmans to replace.
how can crystalloid fluids be categorised?
hypotonic, isotonic and hyper tonic.
what is hartmanns also known as?
compound sodium lactate
name 3 important crystalloid fluids
0.9% saline
Hartmans
5% dextrose
how does 5% dextrose compare to other crystalloids?
the dextrose is rapidly metabolised by the liver and thus this fluid is similar to giving pure water (hypotonic). Therefore a lot will move into the interstitium (1/12 stays in vessels)
distributes to all 3 compartments
what is 5% dextrose used for?
Because only 1/12 remains in vasculature it is not good for resuscitation.
however good for dehydration, hypernatriaemia or hyperosmolarity
what are colloids? explain the theory behind their distribution
large insoluble molecules e.g. albumin and starches
They preserve high colloid osmotic pressure. Therefore remain mainly in the blood
what are the risks associated with colloids?
anaphylaxis
coagulopathy
more likely to cause volume overload
can interfere with Xmatching so take blood for Xmatch before giving colloid
name an example of a colloid fluid
gelatin based: gelufusine
starch based
human albumin solution (HAS)
when are colloids mainly indicated compared to crystalloids?
crystalloids for resuscitation and maintainence
colloids only used in resusitation
what is required for maintenance?
water: 25-30ml/kg/day (or use 4:2:1 rule)
(however can also say you would bare this in mind but titrate the fluid according to the patients vital signs (urine output, blood pressure, heart rate)
na, Cl and K: 1mM/kg/day
50-100g/day of glucose
when should resuscitation not occur?
when the cause for dehydration etc is hypervolaemia because otherwise the fluid will just worsen the oedema etc
what should be considered when prescribing which fluid?
why they need it ? maintain, resus, replace
latest U&E results
co-morbidities esp heart failure and renal failure - risk of volume overload
age - someone who is 20 is unlikely to have heart/kidney failure so larger window for how much fluid they can take.
what is the difference between hypovolaemia and dehydration?
dehydration - loss of water and thus become hypernatraemic
hypovolaemia - loss of both water and sodium. can become haemodynamiccaly unstable.
dehydration can lead to hypovolaemia
what is the problem with long term administration of fluids?
the patient can become hypernatraemic and hyperchloriaemic. Therefore need to keep monitoring U&Es
when should hartmans be avoided?
if at risk of hyperkalaemia
e.g. k+ sparring drugs or renal compromise
post op because K is released by damaged cells
what in the heart hypo and hyperkalaemia lead to?
hypokalaemia - ventricular fibrillation
hyperkalaemia - asystole
how is oliguria defined?
less than 400ml/day or <20ml/hr
how is anuria defined?
<100ml/day
what is the normal urine output of an adult?
60ml/hr
what causes post op oliguria?
dehydration
surgery leads to release of aldosterone, cortisol and ADH which all retain fluid
what are third space losses?
sequestration of fluid in a space that is not involved in dynamic fluid exchange
this occurs with cell injury e.g. in surgery
what is the 4:2:1 rule for how much fluid someone requires?
1st 10kg - 4ml/kg/hr
2nd 10kg - 2ml/kg/hr
the rest - 1ml/kg/hr
therefore for 70kg man: 40 + 20 + 50 = 110ml/hr
what does hartmans contain?
Na (131mM), K (5mM), Cl, ca and HCO3
what does 0.9% saline contain?
Na (154), Cl (154)
308 osmolality
what does 5% dextrose contain?
50 g/L glucose
what defines whether a fluid is iso, hypo or hypertonic?
iso - 240-340
hypo <240
hyper >340
which type of fluid is most commonly hypertonic?
colloids - therefore they can help to reduce oedema.
who can give blood?
must be:
- fit and health
- between 17 and 66
- > 50kg
- no risk of having HIV
- never done IV drug use
- never had hepatitis
- not men who have sex with men
- not currently ill
what is contained within beriplex? Cryoprecipitate? Fresh frozen plasma?
beriplex: factor 2, 9 and 10 (sometimes 7) a.k.a. prothrombin complex
cryoprecipitate: fibrinogen, von willebrand, fibronectin, factor VIII and XIII
FFP - all clotting factors but less concentrated
what is the advantage of using blood products over a blood transfusion?
more tailored to individuals needs and avoids issues with blood transfusion
when is FFP used rather than cryoprecipitate and vice versa?
cryoprecipitate when individual needs a certain type of clotting factor because this will be higher conc
FFP if they need all factors generally or factors that aren’t in cryoprecipitate
how can the need for blood transfusion during surgery be minimised?
correct any anaemias before hand.
what defines a massive blood transfusion?
replacement of more than one unit / >50% of blood in 4 hours.
list 7 complications related to blood transfusion.
clotting problems - dilution of clotting factors with RBC
electrolyte distrubances - hyperK due to haemolysis
haemolytic anaemia - due to Ab and antigen reaction
infections - early and sepsis or late (HIV, Hep)
mild allergy
anaphylaxis
iron overload - late complication from bronze diabetes, liver damage and cardiomegaly
what is an acute haemolytic reaction that follows blood transfusion?
how is this treated?
someone with A blood type will have Ab against B and thus if transfused with B. the Ab will attack B resulting in haemolysis.
this presents as urticaria, fever, back and flank pain and haemoglobinuria.
stop transfusion, resuscitate, O2
why does the O2 carrying capacity of blood reduce as blood gets older?
less 2,3 BPG so O2 binds Hb more tightly so less readily releaed
what is plasmalyte?
a crystalloid solution
contains acetate and gluconate
also sodium and chloride (but less so than 0.9% saline)
which fluids minimise the risk of acidosis?
Hartmans and plasmalyte because less Cl content
how do the pH of different crystalloid solutions compare?
plasmalyte is exactly same as serum with pH of 7.4
Hartmans is the second least acidic
glucose and 0.9% saline are acidic
what is the advantage of using a balanced electrolyte solution (hartmans/plasmalyte) over 0.9% saline?
with 0.9% saline there is an increased risk of
- hyperchloraemic acidosis: this can especially be a problem when there is hypovolaemia and lack of perfusion and thus already some increase in lactate. - some risk of hypernatraemia (with balanced electrolytes, less Na so less likely)
still only small amount of K so can still add K to give correct amounts
what is the maximum rate of K infusion and why?
10mM/hour
otherwise arrhythmias
Give examples of 3rd space losses?
absess pancreatitis ileostomy peritonitis obstruction - fluid drawn in
how does the urine: plasma osmolality compare in pre-renal and renal failure?
pre-renal can still concentrate well so >1.5: 1 urine to plasma
renal: failure to conc so <1.1: 1 urine to plasma
other than vomiting and diarrhoea how else may fluids be lost?
NGT drains high out put stoma tachypnoea fever
other than a fluid challenge how else can we increase the Central venous pressure if it has dropped?
leg raising
in what way is hartmans an alkalising solution?
contains lactate which is a conjugate base
metabolised by liver (cori cycle ) to give HCO3
however be careful because if you measure the blood lactate after giving hartmans it can be high and make you think its endogenous lactate which is a sign of acidosis
what fluid changes occur post op?
increase release of ADH, cortisol and aldosterone due to stress response - retain water and sodium, loose K+
K+ released from damaged tissues.
