Fluids / Resuscitation

Resuscitation Targets

• Targets:
  • Used to be urine output and BP
  • Now:  (Reach in 24 hours)
    • Oxygen Uptake (VO2) > 100 mL/min/m^2
      • Defined by: VO2 = Q x Hb x 1.34 x (SaO2 - SvO2) x 10
    • Lactate < 2.0
    • Arterial Base Deficit > -2 mmol
• Can predict fluid deficit:
  • Class I = 5 mL/kg
  • Class II = 15 mL/kg (postural tachycardia)
  • Class III = 25 mL/kg
  • Class IV = 35 mL/kg

Different Fluids

• Volume Infused	Type of Fluid	Plasma Volume Expansion (mL)
  1.000 mL	D5W	100
  1,000 mL	Lactated Ringer's	250
  1,000 mL	0.9% Saline	275
  250 mL	7.5% Hypertonic Saline	1,000
  1000 mL	5% Albumin	700
  100 mL	25% Albumin	450
  500 mL	Pentastarch	500
  	Plasma

  Reference: "Fluid Resuscitation in Circulatory Shock" book
  And Paul Marino's "The Little ICU Book"

(From "Little ICU book" and Stapczynski JS et al (Emerg Med Prep 1994)
 

• Isotonic Saline
  • Higher sodium, chloride, osmolality.
  • Drawbacks:
    • Hyperchloremic metabolic acidosis --> can create confusion esp in DKA management.
• Lactated Ringer's
  • Ringer's introduced in 1880 as calcium containing solution (promotes cardiac contraction in frogs).
  • Lactate added as a buffer in 1930's
  • Physiologic concentration of free calcium (but as consequence sodium must be lower to balance charge)
    • Lactate used to drop chloride concentration to 109 mEq/L (close to plasma 103)
  • Recommended for surgery, DKA, trauma, burns
  • Drawbacks:
    • Calcium can bind drugs (amphotericin, ampicillin, thiopental) - do not mix solutions.
    • Calcium can bind citrated anticoagulant in blood products, causes clot formation in donor blood.
      • Contraindicated as a diluent for blood products.
• Normal pH Fluid: Normosol / Isolyte / PlasmaLyte
  • Contain acetate and gluconate buffers (pH 7.4)
    • Also potassium (5 mEq/L) and Mg (3 mEq/L), and phosphate (1 mEq/L)
  • Not popular, but recommended as substitute for isotonic saline for washing salvaged RBC's.
• Dextrose Solutions
  • Dextrose was initially a nutrient in IV fluids (1L of 5% D5W gives 170 kcal/L)
  • 3L daily = 500 kcal = enough to meet daily requirements without breaking down proteins.
  • Drawbacks:
    • Expands intracellular fluid (not desired effect), only small portion intravascular.
    • Metabolized by hypoxic tissues to lactate (more acidosis?)
    • Can cause poor glycemic control (worse outcomes).
• Colloid Fluids
  • Large molecules that do not move out of vascular compartment.
  • Create "Colloid Osmotic Pressure" (COP)--> retains water in vascular compartment.
    • Most colloids have COP similar to plasma (stay in plasma), some have higher COP (draw fluid intro vascular space).
    • [i.e. 5% albumin COP = plasma COP]
  • Colloids MUCH (3 times) more effective than crystalloids in increasing plasma volume.

• Fluid	Mol. Wt.	Manufacturer	Duration	Colloid Osm. Press.	Plasma Volume to Infused Volume	Unit Size	Cost (AWP) 2005 Redbook
  Crystalloids
  Isotonic Saline		Hospira		-	0.275	1,000 mL	$1.46
  Ringer's Lactate		Hospira		-	0.250	1,000 mL	$1.48
  Colloids
  5% Albumin	69 kDa	Bayer	12h	20 mmHg	0.7 - 1.3	250 mL	$30.63
  25% Albumin	69 kDa	Bayer	12h	70 mmHg	4.0 - 5.0	50 mL	$30.63
  6% Hetastarch	450 kDa	Abbott	24h	30 mmHg	1.0 - 1.3	500 mL	$27.63
  10% Dextran-40 (6% Dextran-70)	26 kDa	Hospira	Dex-40: 6h Dex-70: 12h	40 mmHg	1.0 - 1.5	500 mL	$14.96
  Taken from "The ICU Book" by Marino 2008.

  • Albumin
    • Heat-treated preparations of human albumin - available as 5% (50g/L) and 25% (250 g/L) in isotonic saline. 
    • Solution of 5% comes in aliquots of 250 mL (~70% plasma retention), but lost after 12 hours.
    • 25% albumin 3x COP of plasma, draws fluid into interstitial space (increment 4-5x infused volume).   Given in 50 mL aliquots where hypovolemia associated with edema (i.e. hypoalbulinemia).  
      • 25% albumin = no appropriate for replacing volume losses.
    • Old Research: Increased mortality attributed to albumin infusion
    • New Research: Cannot reproduce increase in mortality, but reduced morbidity (comp w/ crystalloid)
  • Hydroxyethyl Starch
    • Synthetic starch polymer available as 6% solution in isotonic saline.
    • 3 preparations (based on molecular weight [MW])
      • High MW, Medium MW, Low MW
    • Only High MW available in US.
    • Drawbacks:
      • Increased bleeding with High MW (decreased Factor VIII, and vWF, impaired platelets) [esp if >1.5L is infused in 24hrs]
      • Elevates amylase levels (2-3x ULN) for 1 week, making it look like pancreatitis.
        • (amylase cleaves hetastarch before renal clearance)
      • Accumulates in liver and kidney
    • Studies:
      • Increased death, AKI, dialysis with 10% HES solution (200kDa) --> caused lower kDa HES to be used.
      • Scandinavian trial 6% HES  vs. Ringer's Lactate in severe sepsis --> increases mortality.
      • CHEST Trial: 7000 adults in ICU 6% HES vs. saline --> no mortality difference, but more dialysis in HES group
    • Still used in military, and OR's for rapid volume expansion (but max 33-50 mL/kg)
  • Dextrans
    • Glucose polymers papared as 10% dextran-40 or 6% dextran-70 (different molecular weights)
      • (Both diluted with normal saline)
    • Dextran-70 preferred due to longer duration (12h vs. 6h)
    • Rarely used due to drawbacks
    • Drawbacks:
      • Bleeding tendency (Decr. platelet aggregation, Factor VIII, vWF, enhanced fibrinolysis) [not an issue if low-doses used < 20mL/kg/day]
      • Coat surface of RBCs, interfere with crossmatching blood. (must wash RBC's prior to Xmatching)
      • Also increase ESR (interact with sediment of RBCs)
      • Acute renal failure (suspected, not proven)

Colloid vs. Crystalloid

• Colloid Pros
  • Much more effective in plasma volume expansion
    • 1/3 to 1/4 of volume required to expand the same amount of intravascular volume as crystalloid
• Colloid Cons
  • Expensive
  • No documented survival benefit (cannot justify expense)... many studies show equal efficacy
• Crystalloid Pros
  • Can cause similar intravascular volume expansion, and much cheaper (must infuse more volume)
• Crostalloid Cons
  • Not effective in intravascular volume expansion (goes interstitial)
• Generally:
  • Select fluid type for each scenario
  • i.e. dehydration --> loss of extracellular fluid --> use crystalloids
  • i.e. hemorrhage --> loss of intravascular fluid --> use colloids

Hypertonic Resuscitation

• Using 7.5% NaCl
• Infusing hypertonic saline causes double plasma volume expansion (moves water out of cells)
• Note: No firm indications for hypertonic resuscitation at the present time (2008)
• Potential uses:
  • Military (can carry smaller volumes of fluids for larger resuscitation)
  • Closed head injury trauma patients (limit cerebral edema)
  • Hemorrhage from vascular injury (limit loss from injured vessel)
  • Subarachnoid hemorrhage (6% hetastarch in hypertonic saline effective in reducing ICP)

Important Trials

• SAFE Study
  • No difference in mortality between Albumin and Normal Saline
  • Subgroup: increase in death at 2 years in pts with TBI (traumatic brain injury)
  • Albumin = higher ICP
• Finfer 2011:
  • Albumin = mortality benefit at 28 days in pts with severe sepsis
  • Subgroup: no difference in pts with or without hypoalbuminemia.
• FEAST Study (Fluid Expansion as Supportive Therapy)
  • African 3141 children presenting with febrile illness randomized to:
    • Fluid Bolus (20-40mL/kg) vs. Maintenance (albumin or crystalloid)
  • Result: Bolus = worse outcomes
  • Result: No difference albumin vs. crystalloid
• Scandinavian trial 6% HES  vs. Ringer's Lactate in severe sepsis --> increases mortality.
• CHEST Trial: 7000 adults in ICU 6% HES vs. saline --> no mortality difference, but more dialysis in HES group