IV Fluids
Lecture given:
Objectives
List the differences between colloids and crystalloids
- Crystalloid: water with varying amounts of electrolytes and glucose
- Colloid: albumin, plasma, or large molecular weight carbohydrates such as hydroxyethyl starch or dextran
- Blood components: RBC, platelets, FFP etc to replace missing elements (losses, destruction, underproduction)
Describe how various intravenous solutions distribute themselves throughout the extracellular and intracellular compartments of the body
- Normal saline: ECF - first into plasma, then equilibriate with interstitium
- D5W: free water - 2/3 into ICF, 1/3 into ECF (will need a lot of volume to actually replenish intravascular volume!) - This will dilute the serum solutes! (i.e. lower serum [Na])
- Colloids: Plasma - starling forces to draw more isotonic saline from the interstitium into plasma
- Other weird ones:
- 1/2 NS is 1/2 free water, 1/2 NS. So given 1000ml of 1/2 NS, then 500mL free water will distribute 2/3 ICF and 1/3 ECF, and then 500mL of NS would go into ECF. So the ICF would receive 333mL, and ECF will get 667mL
- bottom line: ECF hypovolemia: isotonic crystalloid/colloid; ICF should be managed by comparing what comes out with what goes in
Effects on electrolytes
- If there is water overload or underload, then must consider the desired effect of increasing or decreasing free water
- The effects of the infusate depends on the concentration of the infusate compared to what is urinated
- If fluid is hypertonic to urine, will increase serum Na
- If fluid is hypotonic to urine, will decrease serum Na
- Can try to mixing different solutions to replace different electrolytes, but MUST make sure the result is approximately isotonic!
- Esp when there is acid base and potasium problems
Maintenance Fluids
- Need to remember to replace loss and insensible losses
- 4-2-1 rule (first 10kg = 4ml/kg/hr, next 10kg = 2ml/kg/hr, after that 1ml/kg/hr, max 125ml/h)
- Healthy kidneys can handle a range of sodium and potassium intake. Ringer's lactate used often in surgical ward
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page revision: 6, last edited: 17 Apr 2012 03:25