Intravenous fluid

• Intravenous fluid administration


  Should be considered as any other pharmacological prescription
• Main indications for intravenous fluid administration

  • Resuscitation
  • Replacement
  • Maintenance
• Four Ds when prescribing fluids

  1. Drug

  2. Dosing

  3. Duration

  4. De-escalation
• Drug


  Consider the indication for the fluid and what effect is being sought
• Duration of therapy


  Consider when to start and when to stop therapy
• Dosing


  Consider how much fluid to give
• De-escalation


  Consider when the fluid therapy is no longer effective or required
• Osmolarity


  The number of osmoles per liter of solution
• Tonicity


  The effect a solution has on cell volume
• Types of tonicity


  • Isotonic
  • Hypotonic
  • Hypertonic
• Crystalloids


  Aqueous solutions composed of water and small solutes such as electrolytes and glucose
• Colloids


  Solutions containing large molecular weight particles such as proteins or hydroxyethyl starches (HES) suspended in a crystalloid solution
• Crystalloid solutions have a shorter intravascular half-life (20-30 min) compared to colloid solutions (3-6 h)
• Advantages of crystalloids over colloids

  • Are just as effective as colloids in restoring intravascular volume
  • Require 3-4 times the volume needed when using colloid to replace an intravascular volume deficit
  • Severe intravascular fluid deficits can be more rapidly corrected using colloid solutions
  • Rapid administration of large amounts of crystalloids (>4-5L) is more frequently associated with tissue edema
• Marked tissue edema from rapid crystalloid administration can impair oxygen transport, tissue healing, and return of bowel function following major surgery
• Infusion of 1 L of 0.9% NaCl adds 275 mL to the plasma volume and 825 mL to the interstitial volume
• Indications for 0.9% Sodium Chloride (Normal Saline) infusion approved by the FDA

  • Extracellular fluid replacement (e.g., dehydration, hypovolemia, hemorrhage, sepsis)
  • Treatment of metabolic alkalosis in the presence of fluid loss
  • Mild sodium depletion
• Other indications for 0.9% Sodium Chloride (Normal Saline) infusion

  • Used in traumatic brain injury or any brain edema
  • Replacement fluid in hyperkalemia
  • Preferred solution for diluting packed red blood cells prior to transfusion
  • Used in DKA when there is severe hypovolemia and when serum sodium less than 140meq/L
• Hypertonic saline


  Employed in therapy of severe symptomatic hyponatremia and severe brain edema
• 0.45% Sodium Chloride


  A hypotonic concentration of sodium chloride, best for parenteral maintenance fluids rather than aggressive intravascular volume repletion
• Lactated Ringer's


  Contains sodium, potassium, calcium, and lactate, designed to promote cardiac contraction and treat metabolic acidosis
• Advantages of Lactated Ringer's


  • Fewer adverse effects on acid-base balance compared to normal saline
  • Used as a replacement fluid in burn patients
• Disadvantages of Lactated Ringer's

  • Calcium can bind to certain drugs and reduce their bioavailability and efficacy
  • Calcium binding to citrated anticoagulant in blood products can inactivate the anticoagulant and promote clot formation
• Uses of dextrose solutions

  • D5% to prevent protein breakdown and replace water deficits
  • D10%, D20% or D50% for hypoglycemia
  • D20%, D25% or D50% for TPN
• Distribution of dextrose solutions

  <10% remains in intravascular space, <30% in interstitial, >50% in intracellular space, causing cellular swelling
• Disadvantages of dextrose solutions

  • Increased lactate production, especially in critically ill patients
  • Enhanced CO2 production
  • Hyperglycemia
  • Increased risk of infection and neuropathy
  • Aggravation of ischemic brain injury
  • Increased mortality in septic shock
• Colloids


  Do not pass across diffusional barriers as readily as crystalloids
• Types of colloids


  • Natural (plasma-derived): Human albumin

  Synthetic: Dextran, Gelatin, Hydroxyethyl starch (HES)
• Albumin 5% solution


  Colloid oncotic pressure (COP) of 20 mmHg, approximately half of the infused volume stays in the vascular space
• Albumin 20% solution


  COP of 70 mmHg, expands the plasma volume by 4 to 5 times the volume infused, intended for shifting fluid from the interstitial space to the vascular space in hypoproteinemic conditions
• Gelatins


  COP 27-34 mmHg, cheapest colloid, rapidly excreted by the kidneys (shorter duration 3-4 hr), can cause anaphylactoid reactions
• Hydroxyethyl starches (HES)


  COP 28 mmHg, long elimination half-life (17 days) but oncotic effects disappear within 24 hours, associated with coagulation dysfunction, pruritis, and renal impairment
• Dextran


  COP 40 mmHg, not used for volume expansion due to high incidence of anaphylactic reactions and negative effects on coagulation
• Indications for colloids


  • Fluid resuscitation in patients with severe intravascular fluid deficits (e.g., hemorrhagic shock) prior to blood transfusion
  • Fluid resuscitation in severe hypoalbuminemia or conditions with large protein losses such as burns
• Colloid solutions are prepared in normal saline and can also cause hyperchloremic metabolic acidosis
• Calculation of maintenance fluid

  Rule of 4:2:1 (infusion per hour): 4 mL/kg/hr for kg 1-10, + 2 mL/kg/hr for kg 10-20, +1 mL/kg/hr above 20 kg

  Shortcut formula: body weight + 40 (for patients >20kg)
• Additional fluid losses to consider

  • Nasogastric aspirates
  • Vomit
  • Diarrhea
  • Stoma, drains, fistula etc.
  • Polyuria