Fluids and Nutrition Flashcards
(42 cards)
Body composition of water?
Total water: 60% of 70kg = 42L
2/3 intracellular = 28L
1/3 extracellular = 14L
- Plasma 3L, Interstitial 10L, transcellular 1L
what is osmotic pressure?
pressure which needs to be applied to prevent the inflow of water across a semipermeable membrane
ie. ability of solute to attract water
what is oncotic pressure?
form of osmotic pressure exerted by proteins
what is hydrostatic pressure?
pressure exerted by fluid at equilibrium due to the force of gravity
third spacing of fluids leads to decrease in?
extracellular fluid
ie. bowel obstruction -> decreased fluid reabsorption -> 3rd space loss
peritonitis -> ascites -> 3rd space loss
minimum urine ouput should be?
0.5 ml/ kg/ h = 30 ml/kg for 60kg human
what is the Na daily requirement?
1.5- 2 mmol/kg/day = 120 mmol/ day for 60 kg
140 mmol/ day for 70 kg
what is the minimum K requirement for the day?
1 mmol/kg/ day = 60 mM/ day for 60kg
what is the average fluid daily requirement for a 60-70 kg human?
e.g. 1L 0.9% NaCl + 2L dextrose with 20mM K+ in each bag
each bag over 8h = 125 ml/h
replacing 3L, 154mM Na+ (around 120) and 60 mM of K+
what are sources of fluid losses that one should replace?
diarrhoea and vomiting
NG tube
drains
fever (+500mL for each degree increase)
Tachpnoea
High output stomas
CVP monitoring
- what is this measuring?
indicates RV preload and depends on venous return and cardiac output
causes of raised CVP?
High circulating volume
Low Cardiac Output: ie. pump failure
Causes of reduced CVP?
low circulating volume
what is a normal central venous pressure?
5-10 cm H2O
what does it mean if CVP does not change despite fluid challenge?
hypovolaemic
what does it mean if CVP increases and reverses after 30 min of fluid bolus?
pt euvolaemic
what does it mean if CVP is sustained above 5cm H2O after fluid challenge/
fluid overload/ pump failure
contents of 0.9% normal saline?
154 mM NaCl
used for normal daily fluid requirements + replace losses
*need to add K+
contents of Hartmanns’/ Ringer’s Lactate solution?
Na: 131 mM
Cl: 111 mM
K: 5mM
Ca: 2.2 mM
Lactate/ HCO3: 29mM
use in resus for trauma pts
alkalinising solution as lactate is a conjugate base
(lactate metabolised in liver -> HCO3 production)
what is a colloid/
contains large molecular weight molecules
e.g. gelatin, dextrans
to preserve oncotic pressure -> remains intravascular -> preferential increase in intravascular volume
e.g.s of colloids
albumin, blood
gelofusin
problems w colloids
increased risk of anaphylaxis
can interfere with cross matching -> take blood for x match before using
How to assess fluid status before examining pt?
History: thirst, surgery, other losses (D+V)
look at fluid balance chart
impression: pt drowsy?
Assessing pt fluid status on examination?
inspection: drips, drains, stomas, catheters, CVP
central CRT, HR, BP lying and standing
JVP
skin turgor, mucous membranes
oedema?
Urine Output, Urea/ creatinine
