Fluid Management & Blood Therapy Flashcards
Hypovolemia is
Common in patients scheduled for surgery due to NPO status, bowel preps, surgical trauma, evaporative losses and dry anesthetic gases
Hypovolemia is associated with significant increase in
Postoperative morbidity and mortality
PONV, organ dysfunction, prolonged hospital stays, and delirium
Goals of fluid therapy include
Avoid or correct a hypovolemia state
Restore intravascular volume
Maintain oxygen carrying capacity intravascularly
Maintain adequate tissue perfusion
Inadequate tissue perfusion leads to
Poor surgical outcomes
Total body water is
60% of lean body weight
Intercellular water is
40% of body weight (2/3rds of TBW)
Extracellular water is
20% of body weight (1/3rd TBW)
Plasma volume 4%
Interstitial volume 16%
Total body water varies with
Age, gender, and body habitus
The total body water in an average 70 kg adult male is
60% TBW
The total body water of an average 70 kg adult female is
55% TBW
The total body water of term infants is
75% TBW
The total body water for premature infants is
80-90% TBW
The total body water for elderly patients is
50-55% TBW
Osmosis is
the movement of water across a membrane from low solute to high solute
The solution with the higher concentration always has
a higher osmotic pressure than solution of lower concentration
Osmolality is
the number of osmotically active particles per kilogram of water
Osmolarity is
the number of osmotically active particles per liter of solution
Osmolality can be calculated by
(serum Na+ x 2) + blood glucose + blood urea (mmol/kg)
Tonicity is
the measure of particles which are capable of exerting an osmotic force
Isotonic means
two solutions with the same osmolarity
no osmotic pressure is generated across cell membranes
Hypotonic is a
solution with a lower osmolarity than plasma
Hypertonic is a
solution with a higher osmolarity than plasma
Plasma communicates continually with interstitial fluid via
capillary pores
What dictates fluid movement?
osmotic forces and hydrostatic pressures
Plasma colloid oncotic pressure maintains plasma volume using
proteins, albumin, and gamma globulins
Osmotic pressure is exerted by
macromolecules (colloid molecules)
Colloid molecules are responsible for
preventing fluid from leaving the plasma and exerting a “pull” from the interstitial space
Endothelial glycocalyx is a
gel layer in capillary epithelium that creates a physiologically active barrier within vascular space
_____ creates a barrier between vessel and blood
endothelial glycocalyx
Endothelial glycocalyx binds to
circulating plasma albumin, preserving oncotic pressure and decreasing capillary permeability to water
also contains inflammatory mediators, free radical scavenging, and activation of anticoagulation factors
Neurohormonal factors that influence fluid dynamics include
RAAS- reabsorption of sodium (and water)
antidiuretic hormone- reabsorption of water
Atrial natriuretic peptide- stimulates kidneys to release sodium and water, thereby reducing intravascular volume
Fluid volume status is assessed
during preop evaluation
Assessing for fluid volume status includes
skin turgor, mucous membrane, edema, lungs sounds, vital signs, urine output, HCT, urine specific gravity, BUN/creatinine
Crystalloid solutions are rapidly distributed
throughout ECF, hence the large volumes required to expand IVF
How much crystalloid is required to expand the IV compartment of 1L?
3-4L of crystalloid
When using crystalloid solutions, we ideally want to use
isotonic fluids with electrolyte composition similar to ECF
The electrolytes of lactated ringer include (Na, K, Ca, Cl, Lactate, glucose, and pH)
Na: 130 mEq/L K: 4 mEq/L Ca: 3 mEq/L Cl: 110 mEq/L Lactate: 28 mEq/L Glucose: 0 g/L pH: 6.5
Lactated ringer solution is
saline with electrolytes (K+, Ca++) and buffer (lactate)
slightly hypotonic (275), provides 100 cc free water per L of solution & tends to lower Na+
Lactate is converted to bicarb
- more physiologic than 0.9% NS
Lactated ringers should be avoided in
ESRD as it contains K+ & not mixed with PRBC because calcium binds to citrate
Normal saline is
0.9% NaCl in water
isotonic solution- osmolality 308
in large volumes produces high Cl- content, which leads to dilutional hyperchloremic metabolic acidosis
Normal saline is the preferred solution for
diluting PRBCs
Normal saline is composed of (Na, K, Ca, Cl, Lactate, glucose, and pH)
Na: 154 mEq/L K: 0 mEq/L Ca: 0 mEq/L Cl: 154 mEq/L Lactate: 0 mEq/L Glucose: 0 g/L pH: 6.0
Normosol-R is composed of (Na, K, Ca, Cl, glucose, Mg, acetate, gluconate, pH)
Na: 140 mEq/L K: 5 mEq/L Ca: 0 mEq/L Cl: 98 meq/L glucose: 0 g/L Mg: 3 mEq/L Acetate: 27 mEq/L Gluconate: 23 mEq/L pH: 7.4
D5W is considered a
hypotonic solution
has little place perioperatively
Concerns with D5W administration is
free water intoxication and hyponatremia
D5W provides
170-200 calories/1000 cc for energy and can cause hyperglycemia except in patients with DM receiving insulin or neonates
3% NaCl has
513 mEq
5% NaCl has
856 mEq
Hypertonic solution is used for
low volume resuscitation, burns, or closed head trauma
principle role is treatment of hyponatremia
Risks with hypertonic solutions include
hyperchloremia, hypernatremia, and cellular dehydration
Colloid solutions are
osmotically active substances
high molecular weight
Colloid solutions are administered in a volume equivalent
to volume of fluid/blood lost from intravascular volume
Albumin is a
blood derived colloid solution
obtained from fractionated human plasma
dose not contain coagulation factors or blood group antibodies
available as 5% or 25%
Albumin expands IV volume up to
5xs volume given by
Albumin (exchange of fluid)
draws fluid in from ISF
dextran is a
synthetic colloid solution that is a water soluble glucose polymer
Dextran 70 is used
for volume expansion
Dextran 40 is used for
improved blood flow in microcirculation and prevention of thrombosis
Side effects of dextran include
highly antigenic–> anaphylactic reaction
platelet inhibition
noncardiac pulmonary edema
interference with cross matching
The max dose of hydroxyethyl starch is
limited to <20 mL/kg/day
Hydroxyethyl starch (6%) is
hespan (0.95% sodium chloride in solution) or
Hextend (in a balanced electrolyte solution similar to Lactated Ringers)
Hydroxyethyl starch is as
effective as albumin for volume expansion but less expensive than albumin
Hydroxyethyl starch can cause
coagulopathy due to dilutional thrombocytopenia
When comparing crystalloids to colloids, crystalloids
are equally effective as colloid in restoring intravascular volume if given in sufficient amounts, support urine output better, less likely to cause pulmonary edema and inexpensive
When comparing crystalloids to colloids, colloids
have prolonged increase in plasma volume by maintaining plasma oncotic pressure, fluid of choice with hypoproteinemia, less tissue edema, less volume infused, intravascular half life is 3-6 hours for colloid vs. 20-30 minutes for crystalloid
Perioperative goals include
meet basal fluid requirements, replace losses, restore/maintain hemodynamic stability, enhance microvascular blood flow so that oxygen is delivered to tissues, maintain aerobic cellular metabolism
Crystalloids are effective for
initial management of ECF losses
hemorrhagic shock, major surgery, or trauma
large volumes lead to hemodilution & decreased plasma colloidal oncotic pressure–> edema and transudates
Continued fluid resuscitation should include colloids attempting to minimize interstitial edema of vital organs: heart, lung & brain
Colloids are effective plasma for
plasma expansion
Sources of intraoperative fluid requirements include
maintenance, fluid deficit, blood loss, and evaporative loss (3rd space loss)
Water and electrolytes are lost through
urine, feces and insensible loss from the respiratory tract and perspirations
The average normothermic 70 kg patient with a normal metabolic rate may lose
2500 ml water/day
The maintenance fluid requirement is calculated by the
4-2-1 rule
4cc/kg/hr for 1st 10 kg
2cc/kg/hr for 2nd 10 kg
1 cc/kg/hr for each additional kg
The fluid calculation for a 75 kg male is
40 cc +20cc + 55cc
115 cc/hour total
Calculating the fluid deficit is done by
taking the maintenance requirement and multiplying it by the number of hours patient is NPO
If a patient is receiving maintenance IV fluids, there is no NPO deficit but consider other losses:
preoperative bleeding, vomiting, diuresis, diarrhea, bowel prep, occult losses, fluid sequestration (edema), ascites, increased insensible losses, hyperventilation, fever and sweating
Fluid replacement strategy is
1/2 deficit replaced in 1st hour of surgery + MIVF
1/4 deficit replaced in 2nd hour + MIVF
Remaining 1/4th deficit replaced in 3rd hour of surgery + MIVF
If a patient is a 75 kg male and has been NPO for 8 hours, describe the fluid replacement strategy for this patient
115 cc/hr maintenance, 115 x 8= 920 cc
460 cc in 1st hour
230 cc in 2nd hour
230 cc in 3rd hour
Evaporative loss is
directly related to surface area of the surgical wound and duration of exposure
3rd space loss is due to
fluid shifts and intravascular volume deficit caused by redistribution of fluids
can be due to trauma, infection (sepsis), burns, and ascites
To calculate 3rd space loss, we need to know
type of procedure, degree of exposure, amount of surgical manipulation
3rd space loss replacement is based on
whether tissue trauma is minimal, moderate or severe
3rd space loss for minimal surgeries
(eye cases, lap chole, hernia, knee scope) 0-2 ml/kg/hour
3rd space loss for moderate surgeries
(open cholecystectomy, appendectomy) 3-5 ml/kg/hr
3rd space loss for severe surgeries
(bowel surgery, THR) 6-9 ml/kg/hr
3rd space loss for emergency surgeries
(Gun shot, MVA) 10-15 ml/kg/hr
1 gm of blood is approximately
1 cc of blood
Visual estimation of blood loss includes
floor and surgical drapes, suction containers (subtract irrigation fluid), soaked gauze 4x4, Ray-tech, soaked laparotomy pads, wet sponges
Wet sponges equate to
20-30% of dry value
Soaked laparotomy pads=
100-150 cc of blood
Ray-tech equate to
10-20 cc of blood
Soaked gauze 4x4 equate to
10 cc of blood
The biggest reason to transfuse is to
maintain O2 carrying capacity of blood
Most adults can tolerate (blood loss)
a 10% loss of EBV
After a 15-20% loss of EBV
we should measure Hgb in healthy patients; earlier if comorbidities dictate
Most providers are conservative with blood transfusion due to
risk of transfusion reaction and blood borne pathogens
Transfusion of health patients tends to occur at
6-7 g/dL (Hct 18-21%)
These patients may require higher hgb (10 g/dL) and Hct (30%)
elderly patients or patients with significant cardiovascular, pulmonary, or neurologic disease
Transfusion should occur when
maintain normovolemia with crystalloid or colloid until danger of anemia outweighs risk of transfusion
When replacing blood loss with crystalloid isotonic solution, replace in a
3:1 ratio- 3 mL crystalloid for 1 mL blood loss
When replacing blood loss with colloid solution, replace in a
1:1- 1 mL colloid for each 1 mL blood loss
When replacing blood with blood:
1:2- 1 mL PRBC for every 2mL blood loss
Estimated blood volume in premature neonates is
95mL/kg
Estimated blood volume in full term neonates is
85 mL/kg
Estimated blood volume in infants is
80 mL/kg
Estimated blood volume in children is
75 mL/kg
Estimated blood volume in adult males is
75 mL/kg
Estimated blood volume in adult females is
65 mL/kg
Estimated blood volume in elderly males is
65 mL/kg
Estimated blood volume in elderly females is
60 mL/kg
Allowable blood loss is used to
determine how much blood you can lose to reach a particular hematocrit
helps anesthetist design appropriate plan and time to transfuse patient
The allowable blood loss calculation is
Estimated blood volume x (pts starting HCT-allowable HCT)/ pts starting HCT
In a healthy 75 kg male with HCT 40%, will allow his HCT to drop to 25%. What is his ABL?
ABL= EBV x (pts HCT- allowable HCT)/pts HCT
75 x 75= 5625 mL
5625 x .15/.4= ABL
844/0.4= 2110 cc
Blood components include
PRBC, platelets, fresh frozen plasma, and cryoprecipitate
Type specific compatibility testing is for
ABO-Rh typing only; 98.9% compatible
Type and screen is done for
ABO-Rh type and screen for specific antibodies; commonly associated with non-ABO hemolytic reactions; 99.94% compatible
Type and crossmatch is done to
confirm ABO-Rh typing (done in <5 minutes), detects antibodies to other blood groups, detects antibodies in low titers (may take up to 45 minutes)
Massive transfusion is
replacement of patient’s total blood volume in <24 hours
acute administration of >1/2 the patient’s estimated blood volume in 3 hours or less
transfusion of 10 units of RBCs in 24 hours
ASA guidelines regarding blood transfusion:
rarely indicated if Hbg >10 g/dL and almost always indicated if Hgb <6 g/dL
if Hgb is between 6-10 g/dL transfusion is based on the patient’s risk for complications and inadequate oxygenation
USE OF A TRANSFUSION TRIGGER OF HGB IS NOT RECOMMENDED
Risks associated with blood product administration include
infections (hepatitis B or C, HIV, bacterial sepsis)
allergic reactions/ febrile reactions
TRALI- lung injury, noncardiogenic pulmonary edema
Hemolytic reactions
Acute hypotensive transfusion reaction
metabolic complications- decreased pH (lactate production) and increased potassium (cell lysis, increased with storage)
Complications associated with blood transfusion:
coagulopathy- usually occurs only after massive transfusion
dilutional thrombocytopenia- responds well to platelet transfusion
low factors V and VIII- stored blood factors may be 15-20% of normal
DIC- activation of clotting system–> microvascular fibrin deposition–> activation of fibrinolysis
Transfusion alternatives include
autologous blood, cell saver, and acute normovolemic hemodilution
1 unit PRBCs will increase hemoglobin
1 g/dL and Hct 2-3% in adults
10 mL/kg transfusion of RBCs will increase Hgb by
3 g/dL and Hct by 10%
Citrate toxicity is due to
citrate preservatives (used as an anticoagulant in stored blood) may bind to and chelate calcium -empiric administration of calcium is not warranted unless ionized calcium levels are low
Clinically significant hypocalcemia resulting in cardiac depression
does not occur in most normal patients unless the transfusion rate exceeds 1 unit every 5 minutes
In one unit of PRBC, the hematocrit is
70%
PRBCs should be
reconstituted with 0.9% normal saline
calcium in LR may cause blood to clot by reversing anticoagulant effect of citrate
PRBCs considerations
further testing if antibodies present or patient has had numerous blood products
type specific ABO and Rh factor alone is sufficient in 98.9% of patients (incompatibility seen in 1 in 1000)
Complications from autologous blood include
anemia, preop myocardial ischemia from the anemia, administration of the wrong unit (1 in 100,000)
need for more frequent blood transfusion
febrile and allergic reactions
Cell saver is the
salvage of blood from the surgical site
blood is processed washed and separated
red cells are transfused back
Contraindications to cell saver include
surgery with wounds contaminated with bacteria, amniotic fluid, malignant cells or patients with sepsis, chemical contaminants
Acute normovolemic hemodilution is when
blood is removed from patient
Replace blood volume lost with crystalloid or colloids
after surgical blood loss has slowed or stopped, patient’s blood transfused back to patient
Uses for platelets include
thrombocytopenia, dysfunctional platelets, active bleeding, platelet count <50,000
Volume of platelets is
200-400 cc
One unit increases platelet count
7000-10,000 one hour after transfusion
The incidence of platelet related sepsis is
1 in 12,000
The incidence of bacterial contamination risk is
1 in 2000
One unit of platelets is
obtained by centrifuging a single unit
Fresh frozen plasma contains
clotting factors and plasma proteins (no platelets)
The volume of FFP is
200-250 cc
FFP must be
ABO compatible
Uses of FFP include
urgent reversal of warfarin, known coagulation factor deficiencies, correction of microvascular bleeding in the presence of increased PT or PTT
correction of microvascular bleeding in the patient transfused with more than one blood volume when PT and PTT cannot be obtained in a timely fashion
Each unit of FFP increases clotting factor level by
2-3%
FFP is contraindicated for
augmentation of plasma volume or albumin concentration
Cryoprecipitate is derived from
precipitate remaining after FFP is thawed
Cryoprecipitate contains
factor VIII (hemophilia A), fibrinogen, vWF, XIII,
Cryoprecipitate is used in the treatment of
von Willebrand's disease fibrinogen deficiencies (ex massive transfusion)
Cryo should be
administered through a filter rapidly and complete within 6 hours
ABO compatible
