Fluids Flashcards
Normal physiology
Total 42L water
14L ECF- 1L transcellul, 3.5L plasma, 9.5L interstit
28L ICF
Insensible loss
Unaware and diffic to quantify, cant be elim-
Transdermal diffus and evap
Resp evap
Sweat?
Sensible loss
Can be seen, felt and measured-
Urine
Defecation
Wounds
Osmotic press
Abil of a solute to attract water.
Or press needed to reverse osmosis.
Oncotic press
Press by prots to draw water into BV
Hydrostatic press
Press of incomp fluid on sealed container eg BV
Osmolality
Osmoles per kg of solvent
Plasma 280-305mOsmol/kg
Osmolarity
Osmoles per L of solution
Osmoles
Number of moles of solute that contrib to osmotic press
tonicity
Effective osmolarity of solution
Same fluid can be hyper or hypotonic dep on where put it
forces
Osmotic forces act across all compartments Stalrings forces (oncot and hstat) act btw intra vasc and interstit fluid
Veins vs arteries
MABP 80-100mmHg- high hstat press, high prot oncotic press.
Venous press 10mmHg- low hstat press, high oncotic
In sepsis capills leak prot so high oncot press into tiss so draws fluid out.
Imp ion concs
Na- plasma 137-147, interstit 144, IC 10 K- plasma 3.5-5, interstit 4, IC 160 Gluc- plasma 3.9-6.1 Prot- plasma 10 Cl- plasma 110
4/2/1 rule for baseline maint fluid only
1st 10kg- 4ml/kg/hr
2nd 10kg- 2ml/kg/hr
Subseq mass- 1ml/kg/hr
Often simplif to 1-2ml/kg/hr in adults
Na and K reqs for adult
Na- 1-1.5mmol/kg/day
K- 0.7-1mmol/kg/day
Regulation
ADH- opens CD aquapaorins. More rel if high Na.
High A and BNP predictor of HF.
RAAS
NICE
Asses the pt
5 Rs- resus, routine maint, repl, redistrib, reass
Less fluid, less Na, more K
Types
Crystalloid dissolved salt and sugar eg saline, hartmanns. Hypo, iso and hypertonic.
Colloid susp not dissolved eg gelatin, starch, alb. Draw fluid into BV. Rarely used now.
Blood products.
Contents
Isotonic fluids 300mOsM
0.9% saline- 154mmol/L Na, 154 Cl
5% dextrose- 50g/L gluc
Dextrose saline- 30 Na, 30 Cl, gluc
Hartmanns- 130 Na, 109 Cl, 4K
Can get KCl 20 or 40mmol/L to saline, dextrose and dextrose saline. Given by infusion pump. Req cardiac monit if central V.
Can give 10mmol/hr K via norm V, more can burn. Big vein up to 20mmol/hr.
Clinical assess
ABCDE, EWS Reason for fluids Hx Diag Dehyd- last food and fluid Losses- diarr, vom, burns Thirst Postural symps Urine output and col Drugs eg diuretics Weight Pulse Cap refill Mucous mems JVP Visible oedema Pmh- DM, CCF, CKD UE, Cr, Hb, haematocrit urine biochem ECG
Bolus
500ml bolus crystalloid eg hartmanns
Give fast with press bag attached
Asses resp
If inadeq give further bolus 250-500ml up to 2L total. Then seek help.
Tx cause
Fluid chall- 500ml in 10-30 mins. 20-30mk/kg/hr.
Resus vs repl
Resus- ongoing fluid loss
Repl- previous loss, reqs repl
Hypovol
Fluid chall- 500ml saline or hartmanns fast as poss
The reass
Crystalloid
Maint and hydration
colloid
Acute resus or repl. 250-500ml. Can worsen oedema if inflamm. Coagulopathic in trauma. Risk anaph. Expensive Crustalloid if in doubt. Main 3 are volplex gelatin, albumin, blood products.
confused pt
Exclude hypoxia and dehyd first
Key Qs
Pt size and weight Comorbidiy- heart, lung, renal Situation- resus vs maint Why in hosp- eg how far post op Most recent UE Underlying physiol What are they losing and how much- eg diarr, pancreatitis, open wound, perforat, obstruc cause loss electrolyte rich fluid.
fluid func
Maint SV and hence perfus
MABP= tpr x CO
CO= HR x SV
Low BP must be due to one of these facs eg dehyd, meds, sepsis
Too much fluid over time causes overload and HF
dextrose
Pure water not for resus
Good for maint just water
hartmanns
Good for resus
Still only 1/6 of it gets to plasma
May need lot in resus phase
sedentary av adult maint
2.5-3L/ day
150mmol Na per day
60mmol K per day
Renal dis
Cant excrete K- hyperK
fluids need to be isotonic
300 mOsM approx
Maint regimens if start IN BAL
Eg after resus
UE norm, still NBM
Loads of saline causes acidosis
Regimen 1- 1L saline 8hr, 1L 5% dextrose 8hr, 1L 5% dextrose 8hr.
Regimen 2- 1L dex/saline 8hr, three times.
Adjust acc to UO and UE.
resp to surgery
Incr ADH as stress- reduc UO, Na reten.
Incr aldoserone and cortisol- Na reten, loss K and H.
Incr catecholamines
Incr renin
K rel by damaged tiss. So dont us give supplem K during 1st 48 hr post op.
IV K risks
Renal comprom
K sparing diuretics
HypoK- VF
HyperK- asystole
K regimens if start IN BAL
Regimen 1- 1L saline 8hr 20M K, 1L 5% dextrose 8hr 20M K, 1L 5% dextrose 8hr.
Regimen 2- 1L dex/saline 20M K 8hr TWICE, then 1L dex/saline 8hr.
Over 20mmol/hr needs uspervis by senior and controlled pump.
UO
Oliguria under 400ml/day Anuria under 100 Sensitive indicator hydrat status Normal 0.5ml/kg/hr Hourly monit post op. Us bit low. If unus low then small bolus top ups and monit. Also check BP, catheter, UO, drug chart.
dehyd signs
Sunken eyes Reduc ocular press Reduc skin turgor Dry mucous mem Low UO Thirst Late- cap refill, tachc, low BP
Equation
Vol (ml)/ time (mins) x giving set= drops per min
Reasons
Resus- want to stay in IV space
Maint- want fluids to distrib to all comparts
Repl
fluid overload
JVP
Periph and pulm oedema
Late- tachyc/p, hypoxia
Monitor- UO, UE, weight.
daily reqs
25ml/kg/day water
1mmol/kg/day Na
1mmol/kg/day K
50g/day glucose
Fluid chall
Eg anyone with low UO
250 or 500ml hartmanns over 1hr
But account for pt facs
ongoing losses Qs
Thrid space loss Is there diuresis Tachyp Temp Amnt of stool Are they losing electrolyte rich fluid Egs- dehyd (high urea to Cr ratio and high PCV), vom (low K, low Cl, alkalosis), diarr (low K, acidosis)
Monitoring
Fluid bal
Weight
UE
