WEEK 3 (IV FLUIDS)

• What are the main principles + priorities of FLUID RESUSCITATION?

  PRINCIPLES:

  1. early restoration of tissue perfusion
  2. preservation of renal function
  3. minimal biochemical disturbances
  4. avoidance of complications

  PRIORITIES:

  FIRST: restore volume

  SECOND: restore blood

  THIRD: normal coagulation
• What is RESTORING VOLUME?

  • improve circulating fluid to increase CO and tissue perfusion
  • End organs are susceptible to permanent damage
  • administer fluids to increase volume expansion which increases circulating volume and CO
• What is the 3:1 rule when restoring fluid volumes?

  Crystalloid solutions leave plasma due to small solutes which means a large proportion of fluid we give leaves circulation (~2/3 over 60min). This means we can give 3 x volume as to the volume that has been lost e.g. someone lost 500ml, we can give 1500ml
• What is the SECOND + THIRD PRIORITY?

  RESTORING BLOOD VOLUME:

  • restore volume where blood has been lost
  • we don't carry on ambo

  RESTORING COAGULATION:

  • TXA
  • may need platelets, plasma or clotting factors
• What is the TRIAD OF DEATH?

  • hypothermia
  • coagulopathy
  • acidosis
• What are the key complications associated with fluid administration?

  1. fluid overload (overload system, stress on heart, liver, kidneys)
  2. haemodilution (dilute RBC, clotting factors and platelets = reduces oxygen carrying)
  3. acidosis
  4. hypothermia (IV fluids are room temp, not body temp)
• What are the types of MEDICATION ADMINISTRATION?

  BOLUS: push of medication to administer specific doses

  • rapid onset of effect
  • short duration
  • small volume
  • higher risk

  INFUSION: slow continuous administration (longer with controlled rate)

  • slow onset
  • longer duration
  • large volume
  • lower risk
• What is the drip calculation?

  PER MIN = volume to be infused (ml) x drip factor. Divided by time for infusion in min

  PER SEC = drops per min divided by 60 seconds
• What is MOLARITY, OSMOLARITY + TONICITY?

  MOLARITY = number of moles of solute per 1L

  OSMOLARITY = number of particles present after being dissolved in H2O

  TONICITY = a measure of the osmotic pressure gradient between two solutions (describes whether a fluid has MORE or LESS osmolarity than the compartment next to it)
• What are the different types of TONICITY?

  HYPERTONIC = solution with a relative HIGHER osmolarity than that found in body cells and blood

  HYPOTONIC = solution with a relative LOWER osmolarity than that found in body cells and blood

  ISOTONIC = solution with the same osmolarity as that found in body cells and blood

  Typically comparing the osmolarity of an IV solution to than of an intravascular fluid
• What is an ISOTONIC solution?

  • no change in plasma osmolarity
  • there is still movement between ECF and plasma but NO NET MOVEMENT
  • same reabsorption and filtration as Starling's Law
  • in theory if we give 1L of isotonic solution into the intravascular compartment, this will not change the osmotic gradient and should remain in the plasma = more circulating volme
• What is a HYPOTONIC solution?

  • reduced plasma tonicity compared to ECF
  • movement out of the intravascular compartment (move to a more concentrated area)
  • hydrate cells whilst depleting vascular compartment
  • more water in the intravascular compartment and low solute
  • H2O moves towards the area of highly concentrated solutes (interstitial)
  • Giving 1L of hypotonic solution into the intravascular space, a large proportion will leave the space and into the interstitial.
  • NET EFFECT is to rehydrate cells rather than expand blood volume
  • used for conditions with cellular dehydration e.g. hyperglycaemia
• What is a hypertonic solution?

  • increases plasma osmolarity
  • movement into intravascular space from interstitial
  • increases circulating volume, increases urine output and decreases oedema
  • rapid volume expansion
  • Giving 1L of hypertonic solution into intravascular space, we are increasing the osmolarity of the blood.
  • fluid from the interstitial is pulled into the plasma (low concentrate to high)
  • promotes reabsorption
  • dehydrates cells as fluid is pulled from interstitial and intracellular spaces
• What are the 2 types of IV fluids?

  1. crystalloid
  2. colloid
• What is a crystalloid solution?

  • contains dissolved solutes and electrolytes
  • molecules quickly dissolve in solution
  • small particles that can easily move through cell membranes
  • categorised by tonicity
  • expect 1/3 of the solution to remain in the vascular space 1hr after administration
  • solutes move from one space to another and H2O follows

  EXAMPLES:

  • lactated ringers (isotonic)
  • normal saline (isotonic)
  • 5% dextrose in H2O (hypotonic)
• What is a colloid solution?

  • contains molecules that are too large to pass out of the capillary
  • prolonged effect
  • draws fluid in by osmotic pressures
  • usually proteins and hypertonic
  • need proper diagnostics and monitoring of blood

  EXAMPLES:

  • albumin
  • hespan + dextrans
• What are the advantages and disadvantages of CRYSTALLOID solutions?

  ADVANTAGES:

  • cheap
  • low risk of allergy

  DISADVANTAGES:

  • short half-life
  • larger volumes required
• What are the advantages and disadvantages of COLLOID solutions?

  ADVANTAGES:

  • longer half-life
  • small volume needed

  DISADVANTAGES:

  • expensive
  • risk of allergic reaction