Pharmacology - IV fluid therapy Flashcards
what percent of the body is TBW
60%, 40% ICF and 20% ECF (made of interstitial fluid and plasma)
equation for osmotic pressure…
n x c(c/m)RT
what is osmolality?
The measure of solute concentration per unit MASS of solvent. Number of osmoles of solute/kg. 1 osmole contains 6.02 x 1023 particles, Body fluids measured in millimolar concentrations (mosm/kg)
what is osmolarity?
The measure of solute concentration per unit VOLUME of solvent. Number of osmoles of solute/litre. Estimated osmolarity of body fluids can be calculated, 2([na+] + [k+]) + urea + glucose
what is normal plasma osmolarity?
298mosm/L
what is the daily maintainance requirement for iv fluids, in terms of fluid and electrolytes?
water = 30ml/kg, Na = 1 mmol/kg, K = 1 mmol/kg, Glucose = 50-100 g
what is Tonicity?
The measure of the osmotic pressure gradient between two solutions. Tonicity = effective osmolality, Only particles restricted to one of the compartments will determine water distribution, Particles which move freely will not influence water distribution ECF>Na, ICF>K and macromolecules.
if a soultion is hypertonic…
cells will dehydrate
if a solution is hypotonic…
cells will swell
what are Crystalloids?
aqueous solutions of mineral salts or other water-soluble molecules, cheap, non-allergenic, ECF expansion, (oedema, inceased vascular pressure), high Na load - may cuase hypernatraemia, useful in acute dehydration, resus.
what are Colloids?
contain larger insoluble molecules, such as gelatin; blood itself is acolloid, Anaphylaxis, Coagulopathy, Renal failure, rheology
give egs of Crystalloids
dextrose, saline, hartmanns solution, plasmalyte
give egs of Colloids
gelatins, starches, albumin, blood products.
what is dextrose?
Simple sugar. Total Body Water, Moves through all compartments, Not useful for Blood volume expansion, Zero sodium load, isotonic. For Chronic Dehydration and
Hypernatraemia
what does saline contain?
Nacl 0.9% give at 100ml/hour, Contains - Sodium 154 mmol/l – 10% higher than ECF, Choride 154 mmol/l – 50% higher than ECF
how much fluid (Slaine) is given for maintainance
30ml/kg/24hrs (20-25ml in frail & elderly), Never give over 100ml/hr due to risk of hyponatraemia
how much and what is given for replacement?
PlasmaLyte 148
questions to ask when giving fluid replacement…
pt volume status? Need for iv fluids? How much? What type?
what happens if the pt is HYPOvolaemic?
Feels nauseous, thirsty, Flat veins, Cool peripheries, No sweat, Low or postural BP and high HR, Concentrate oliguria, Responds to SLR = give fluids
what happens if the pt is HYPERvolaemic?
Feels breathless, not thirsty, Veins distended, Warm and oedematous extremities, Sweaty, High BP and High HR, Dilute urine (could be oliguric or polyuric) = give diuretics
what helps workout how much fluid is needed due to water defecit?
catheters, drains, input charts, vomit bowls, sputum pots, stool charts and stoma losses
what are insensible losses?
sweat, ventilation, open wounds, burns, bleeding. Normal daily loss = 400-800mls in adults.
what are the 5 R’s?
resus, routine maintainance, replacement, redistribution, Reassessment.
CASE 1
30 year old female, 49kg, Elective hysterectomy (low blood loss), Plasmalyte intraoperatively, Post op fluids: 0.18% saline/4% dextrose @ 62.5ml/hr, Speeded-up because of nausea (5L given over 16 hours [312.5ml/hr], Tailor iv fluid to compartment requiring filling, Excess hypotonic fluid in a patient secreting adh
Assume sodium of 138 at end of operation, 5l dextrose/saline (4l 5% dextrose + 1l 0.9% saline), Tbw = 55% of 49kg = 27l; ecf (before fluid) 9L, Saline distributes only in ecf. Water will fill all compartments, Ecf following fluid = 9l + 1l (saline) + 1.3 = 11.3l, Na content before fluid = 9 x 138mmol/l = 1242mmol/l, Na content after fluid = (9l X 138) + (154 in 1l 0.9% saline) = 1396mol/l, [na] after fluid = 1392/11.3 = 123mmol/l
