Week 3 - Fluid and Blood Therapy Flashcards
What is the body water distribution (5) relative to lean body weight in men, women, and term infant?
Men: intracellular (40%), extracellular (20% – intravascular 5% & interstitial 15% — total body water 60%
Women: intracellular (33%), extracellular (17% – intravascular 4% & interstitial 12% — total body water 50
Term Infant: intracellular (50%), extracellular (25% – intravascular 6% & interstitial 19% — total body water 70-75%
What are the classic fluid compartments?
Total Body Water (extracellular + intracellular)
Extracellular Fluid Volume (1/3 body weight) or Intracellular Fluid Volume (2/3 body weight)
Extracellular Fluid Volume –> interstitial fluid (3/4) or plasma or transcellular fluid
What occurs during surgery with the interstitial fluid space?
Capillary permeability increases and more fluid escapes to the interstitium
What is the third space?
A nonfunctional space somewhere within the body that accumulates fluid that escapes from the vasculature and the interstitium
- Does it really exist? if so needs replacement
- probably doesn’t exist – current theory leans toward restricted fluid admin
What are the consequences of hypovolemia?
-Contributes to inadequate tissue perfusion and postop complications
- Standard hemodynamic monitors don’t detect occult hypovolemia which contributes to inadequate perfusion
- Tachycardia lacks sensitivity and specificity as a surrogate assessment of volume status
- By the time hypotension is obvious, hypoperfusion has already occurred
- Fluids should be admin when pts require augmentation of perfusion and are volume responsive
What are consequences of hypervolemia?
Weigh Gain – >10% of preop weight has 32% mortality rate, <10% has 10% mortality rate
Pulmonary edema – occurred when volume infused >67mL/kg/hr
Bowel manipulation results in a 5-10% increase in weight at the anastomosis
Tissue edema leads to impaired wound healing secondary to decreased O2 tension
What is the goal of fluid management in surgical patients?
Maintain physiological homeostasis
Optimize Tissue Perfusion
-optimize vascular volume, stroke volume, oxygenation
What are the classic fluid maintenance calculations?
Replace maintenance fluids throughout surgery (basil rate) - 4:2:1 rule IBW
-4cc (10kg) + 2cc (10kg) + 1cc/kg (>20kg) – or IBW + 40
Replace Preoperative NPO Deficits - maintenance rate x # hours NPO
-50% in 1st hr, 25% in 2nd, 25% in 3rd
Replace Surgical Losses (EBL) - 3:1 rule
3rd Space Losses - 2-10 mL/kg/hr
What is goal directed fluid therapy (GDFT)?
Optimized fluid therapy to ensure adequate tissue perfusion –> tissue oxygen delivery –> cellular oxygenation
Prevent cell death and organ damage
How do you optimize tissue perfusion with goal directed fluid therapy?
Maintain appropriate intravascular volume
Maintain preload –> maintain CO
Maintain adequate tissue BP (arterial, venous, obstructive forces)
What is the concept of Fluid Responsiveness and Frank-Starling Curve?
Hypovolemia: fluid admin improves cardiac performance – there is “recruitable cardiac output”
Euvolemia: maximum cardiac output
Hypervolemia: further fluid has no benefit
How to calculate Pulse Pressure Variation and Systolic Pressure variation?
PPV = PP(max) - PP(min) / PP(mean)
SPV = SP(max) - SP(min)
What is the purpose of a fluid challenge?
Tests the functional reserve of the CV system – is there additional preload function that can be used to augment CO (SV) if additional fluid is presented to the heart (preload)
-can be repeated as long as the response is positive (increase in BP after fluid challenge likely increase CO = success)
Define Hypotonic, Isotonic, and Hypertonic fluids
Hypotonic: Na+ concentration less than 130 mEq/L = osmolarity <280 mOsm/L (ex: 0.45% NS)
*fluid moves into cells
Isotonic: Na+ concentration 130-155 mEq/L = osmolarity 280-310 mOsm/L (ex: LR or 0.9% NS)
Hypertonic: Na+ concentration greater than 155 mEq/L = osmolarity >310 mOsm/L (ex: 3% NS)
*fluid moves out of cells
What are examples of crystalloids?
Normal Saline (0.9%) - isotonic and isosmotic to plasma Na+ but less Cl- (large volumes result in mild hypernatremia and hyperchloremia - non ion gap acidosis)
Lactated Ringers - intended to mimic composition of plasma better (has minimal amounts of electrolytes added and frequently some sort of buffer
Hypertonic Saline - used for replacement in the case of hyponatremia or to reduce cerebral swelling
Glucose containing solutions - used to replace glucose in pts who need sugar
What are examples of colloids? When are they used?
Albumin, Hetastarch, Dextrans
- contain large molecular weight protein or glucose polymer particles
- create osmotic force which keeps water intravascular
- tend to stay intravascular longer than crystalloids
-Beneficial in the pt who needs volume support but tends to go into CHF and would not do well with large volumes of crystalloids
What are the advantages of crystalloids for perioperative use?
- Cheap
- Acceptable for replacement of preop, intraop, and postop isotonic fluid deficits
- Provide maintenance water and electrolytes
- Expansion of intravascular volume
When using crystalloid to replace blood loss; replace with _____ml(s) of crystalloid for every 1ml of blood loss.
Replace 3mL of crystalloid per 1mL of blood lost
*the ratio of blood volume to interstitial fluid volume is about 1:3
How do crystalloids move about the fluid compartments?
Sodium containing solutions move freely about the extracellular space
Sodium-free solutions (D5W) distribute throughout all fluid compartments
Within what fluid compartment does colloids distribute?
Almost exclusively to the intravascular space
*intravascular volume expansion can be accomplished with a smaller fluid volume, lasts longer, and results in less peripheral and pulmonary edema
When using colloid to replace blood loss; replace with _____ml(s) of colloid for every 1ml of blood loss.
generally administered in a 1:1 ratio equivalent to the volume of blood lost
When is a blood transfusion indicated?
When you desire to increase oxygen carrying capacity
NOT when your goal is intravascular volume expansion
*ultimate transfusion threshold must be based on the clinical judgement of many factors such as age, CV status, anticipated additional blood loss, arterial oxygenation, CO, and blood bolume
What is cross matching of blood?
An in vitro trial – takes 45 min
Donor cells are mixed with recipient serum, checks for ABO incompatibilities and other naturally antibodies
Antibody screening - recipient serum and commercially prepared RBCs that are specifically selected to contain the optimal number of RBC antigens
What is a type and screen of blood?
Donor blood is of the same ABO and Rh type and is screened for the presence of common antibodies
Recipient is ABO and Rh typed and screened for the presence of common antibodies
What are signs of hemolysis during a blood transfusion?
Red or pink urine
Hypotension
Bronchospasm
What is FFP?
the liquid portion of a single unit of blood which has been separated from the RBCs within 6 hours after donation and frozen at about -18*C
contains all the plasma proteins, especially Factor V and VIII
- must be transfused within 24 hours of thawing
- ABO compatibility is desirable but a crossmatch is not necessary
What is Cryoprecipitate?
Contains significant levels of Factor VIII and fibrinogen but also contains von Willebrand factor and fibronectin
Fraction of plasma that precipitates when FFP is thawed
Use for factor VIII deficiency, hemophilia A, or for Fibrinogen deficiencies
