Week 3 - Fluid and Blood Therapy

Question 1

What is the body water distribution (5) relative to lean body weight in men, women, and term infant?

Answer 1

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%

Question 2

What are the classic fluid compartments?

Answer 2

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

Question 3

What occurs during surgery with the interstitial fluid space?

Answer 3

Capillary permeability increases and more fluid escapes to the interstitium

Question 4

What is the third space?

Answer 4

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

Question 5

What are the consequences of hypovolemia?

Answer 5

-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

Question 6

What are consequences of hypervolemia?

Answer 6

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

Question 7

What is the goal of fluid management in surgical patients?

Answer 7

Maintain physiological homeostasis

Optimize Tissue Perfusion
-optimize vascular volume, stroke volume, oxygenation

Question 8

What are the classic fluid maintenance calculations?

Answer 8

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

Question 9

What is goal directed fluid therapy (GDFT)?

Answer 9

Optimized fluid therapy to ensure adequate tissue perfusion –> tissue oxygen delivery –> cellular oxygenation

Prevent cell death and organ damage

Question 10

How do you optimize tissue perfusion with goal directed fluid therapy?

Answer 10

Maintain appropriate intravascular volume

Maintain preload –> maintain CO

Maintain adequate tissue BP (arterial, venous, obstructive forces)

Question 11

What is the concept of Fluid Responsiveness and Frank-Starling Curve?

Answer 11

Hypovolemia: fluid admin improves cardiac performance – there is “recruitable cardiac output”

Euvolemia: maximum cardiac output

Hypervolemia: further fluid has no benefit

Question 12

How to calculate Pulse Pressure Variation and Systolic Pressure variation?

Answer 12

PPV = PP(max) - PP(min) / PP(mean)

SPV = SP(max) - SP(min)

Question 13

What is the purpose of a fluid challenge?

Answer 13

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)

Question 14

Define Hypotonic, Isotonic, and Hypertonic fluids

Answer 14

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

Question 15

What are examples of crystalloids?

Answer 15

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

Question 16

What are examples of colloids? When are they used?

Answer 16

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

Question 17

What are the advantages of crystalloids for perioperative use?

Answer 17

• Cheap
• Acceptable for replacement of preop, intraop, and postop isotonic fluid deficits
• Provide maintenance water and electrolytes
• Expansion of intravascular volume

Question 18

When using crystalloid to replace blood loss; replace with _____ml(s) of crystalloid for every 1ml of blood loss.

Answer 18

Replace 3mL of crystalloid per 1mL of blood lost

*the ratio of blood volume to interstitial fluid volume is about 1:3

Question 19

How do crystalloids move about the fluid compartments?

Answer 19

Sodium containing solutions move freely about the extracellular space

Sodium-free solutions (D5W) distribute throughout all fluid compartments

Question 20

Within what fluid compartment does colloids distribute?

Answer 20

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

Question 21

When using colloid to replace blood loss; replace with _____ml(s) of colloid for every 1ml of blood loss.

Answer 21

generally administered in a 1:1 ratio equivalent to the volume of blood lost

Question 22

When is a blood transfusion indicated?

Answer 22

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

Question 23

What is cross matching of blood?

Answer 23

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

Question 24

What is a type and screen of blood?

Answer 24

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

Question 25

What are signs of hemolysis during a blood transfusion?

Answer 25

Red or pink urine

Hypotension

Bronchospasm

Question 26

What is FFP?

Answer 26

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

Question 27

What is Cryoprecipitate?

Answer 27

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