Yr 2 3 Fluid Replacement Solutions Flashcards
Fluid compartments
- body water - 60% adult body weight
- Body water - 80% neonate
- ECF
-20% body WEIGHT
OR
-1/3 total body WATER (Na+ main cation) - ICF
-40% BW
-2/3 body water (K+ main cation) - Interstitial fluid
- 15% body weight
OR
- 1/4 total body WATER - Intravascular fluid
5% bodyweight
or 1/12 total body water
For 500kg horse work out ICF ECF Interstitial fluid Intravascular fluid
ECF - 20% BW = 100kg
ICF - 40% BW = 200kg
Interstitial - 15% BW = 75kg
IVF - 5% BW = 25kg
30kg dog, 10% dehydrated and has a fluid deficit of 3L. How much fluid is missing from plasma?
- 10% fluid deficit = 3L
- check lec
What does dehydration result in?
- Fall in blood volume
- = Fall in blood pressure
- activation of baroreceptor reflex and RAAS
- baroreceptor - medulla oblongata - inc sympathetic, dec parasympathetic
- RAAS - inc renin release from JG cells
How do we give fluids?
- Enteral- Ideally use the natural route i.e. the gut, Oral voluntary intake, Via tube
- Parenteral- IV, Intra-osseous, Intra-peritoneal, SC
Oral fluid therapy
- what is it based on?
- when do you sue
- what do you rely on
- Based on
o Active sodium-glucose co-transport
o Equimolar Na & Glucose = much more fluid is reabsorbed - Use when mild/ moderate fluid volume disturbances-
- Severe decrease in BP will result in vasoconstriction which reduced absorption of water from the GI tract - relies on gastrointestinal tract functioning
How has the development of oral fluids changed
- 1st gen equimolar glucose and Na
- 2nd gen - additional bicarbonate to reduce risk of metabollic acidosis as lot of HCO3- lost in diarrhoea
- 3rd gen - higher glucose - esp important for young nutritional demands
- glutamine which promotes villus repair and regeneration as D causes atrophy. Atrophy = no normal absorption
How to choose oral fluid
- Rehydration ability
- Ability to correct acidosis.
- How much glucose?
- Nutritional ability & prevention of villus atrophy to help maintain growth - glutamine is expensive
scouring 40kg calf
advise to farmer
- give ASA scour starts
- Give most natural way for calf to suckle - teat. If no drink then stomach tube
- 40kg calf = 4-8 litres daily
- Give little and often
- Decide on product
- DO NOT STOP FEEDING MILK as this causes more villus damage and atrophy
Types of parenteral fluids
Crystalloids and Colloids
Crystalloids
a. Salt solutions that that freely cross capillary walls. (most electrolytes are v small molecules so can pass inbetween)
i. Stay in vascular space for short time (freely cross). Quickly (mins) leak into extracellular fluid compartment
Colloids
a. Non crystalline substances consisting of large molecules diluted in a crystalloid. Capillary endothelium is impermeable to these large molecules so tend to stay in vascular space
Crystalloids more in depth
- electrolyte solutions
2. give either non physiological or physiological solutions
Talk about crystalloids physiological and non physiological solutions
- non physiological solutions
- 0.9% NaCl
- Has tonicity similar to plasma but is a non physiological, chloride rich unbalanced salt solution
- Because if analysed ECF it contains a lot more than Na and Cl - physiological
a. Isotonic to plasma and designed to mimic plasma so:
- Are buffered
i. Can contain HCO3
ii. or more often – contain molecules (such as acetate, gluconate, and lactate) these anions are metabolised in the liver produce of HCO3-
c. Balanced
i. contain electrolytes in addition to Na+ and Cl- (such as K+ Ca2+ Mg2+ ), making them similar to protein free plasma. Lactated Ringer’s is an example of a balanced solution.
What sort of solutions can crystalloids be?
- isotonic
- hypertonic
- hypotonic
Isotonic crystalloid solutions
• These have the same concentration of electrolytes as plasma and are therefore isosmotic (same number of particles) with plasma when they are administered into the circulation.
• E.g. 0.9% Na Cl
o Most solutions have a high [Na+ ] and therefore similar to ECF rather than intracellular fluid
• Are poor plasma volume expanders as less than 25% of solution injected into vein is retained in vascular space within 30 mins.
o If inject 250ml into 30kg dog, it won’t stay very long as you are putting into vasculature it empties out into extracellular space
• Within 1 hour, 75% of isotonic crystalloid has moved into the extravascular space. i.e. fluid quickly distributes within extracellular fluid compartment
Hypertonic crystalloid sollutions
Result in fluid accumulation in intracellular space
• Considered to be plasma expanders because their inc tonicity causes water to move from interstitial and intracellular sites into the intravascular compartment • E.g. 7.2% NaCl solution (8X more conc what normal saline!
o High conc salt conc into ECF, water moves in, inc blood volume and therefore pressure
Hypotonic crystalloid solutions
• These have a lower concentration of electrolytes than plasma but are isosmotic with plasma when they are administered into the circulation.
o 5% dextrose in water is isotonic when it enters the circulation but dextrose (glucose) is a penetrating solute and so
o dextrose enters cells and is metabolised
o a 5% dextrose (form of glucose) solution is therefore hypotonic as effectively you are administrating water
o dextrose sued up so left with water
Why would you use a hypotonic crystalloid solution when something is going to end up as water?
o Fluid therapy si often aimed at expanding plasma volume BUT NOT ALWAYS!
o Face trauma – animal can’t drink
o Doesn’t need high Na all time
Tonicity vs osmolarity
- O - describes number of particles between 2 solutions, determines where water will move (high to low conc)
- T - what happens between cells and body fluids. Cell membranes have different permeabilities
Colloids
• Colloids – Large molecules (5 – 1000kDa) thus can’t pass through healthy vascular endothelium
o Therefore they inc colloidal osmotic pressure of the plasma & “pull” water from the interstitial space = PLASMA VOLUME EXPANDERS
When would you use colloids?
difficult to administer sufficient volumes of fluids rapidly enough to resuscitate a patient (e.g., large patient, emergency surgery, large fluid loss).
• When decreased oncotic pressure is suspected 1. E.g. hypoproteinaemia
• Often use crystalloids with them: as wanna make sure there is fluid going into animal
What is a colloid?
• Colloids are water-based solutions with a molecular weight too large to freely pass across the capillary membrane
What are the diff types of colloid?
Natural: whole blood, plasma, albumen: When animal requires RBSs, clotting factors or albumin, blood products are colloid of choise
2. Synthetic - starches, gelatins, dextranss
Adverse effects of colloids
o Anaphylactic reactions
o Coagulopathies
o Oedema (also a risk with crystalloids and basically ALL fluid therapy
What is the maintenance fluid requirement of a normal 12 kg dog?
50ml/kg in 24 hrs = 600 mls per day
How is a intravenous solution containing NaCl 7.2% best described
Hypertonic crystalloid solution
Major difference between 2nd and 3rd gen oral replacement fluids
third gen contain more glucose than 2nd
Approx ECF 100kg calf
20L
