Anesthesia – fluid replacement in blood loss

How do you assess the amount of blood loss, visually?
– Surgical field
– Drapes
– Suction bottles
– Irrigation fluid
– Spondges
– Within an organ removed
– In a horse trailer, kennel, etc.

How much blood does a 4×4 gauze sponge hold?
15 ml

How much blood will a lap sponge hold?
50-75 ml

How can you directly assess blood loss?
Blood in a suction jar.

(PCV of suction jar/pre-op PCV of patient) x volume of jar = estimated ml of blood in suction jar

How can amount of blood loss be assessed through physiologic observation?
– BP decrease
– Decrease in PCV, TP, hemoglobin
– Decrease in urine output
– Increase in heart rate (ESPECIALLY IN DOGS)
– Increase in vasoconstriction
– Decreased tissue perfusion and oxygenation
– Decreased ET CO2

When is oxygen transport compromised?
PCV is less than 20%

When is there depressed cardiac function?
PCV is less than 30%

Rules of thumb: When should you do a blood transfusion?
– Acute loss of greater than or equal to 20% of blood volume
– PCV is less than or equal to 20%
– Plasma protein is less than 3.5 g/dl
– Hemoglobin is less than 7-10 g/dl

What are some other things that would suggest a blood transfusion is needed?
– Patient is unresponsive to crystalloids/colloids
– Hypovolemic shock: pale MM, prolonged CRT, increased HR and RR, decreased arterial BP, decreased CVP

What are some considerations for determining if a transfusion is needed?
– Is anemia acute or chronic?
– What is the cause?
– Is there potential for more blood loss?
– How did the patient respond to other supportive therapies?
– What is the status of the patient (cardiopulmonary, renal, etc.)?

T/F: It is harmful to transfuse a normal PCV?

As hematocrit increases, so does blood viscosity, which may not be desirable in a patient with poor tissue perfusion from acute hemorrhage/shock.

How do you calculate blood volume?
– 6-8% of total body weight in kg


– 60-80 ml/kg

What is considered minimal blood loss?
Less than 10% of blood volume

What should you do when there is minimal blood loss during surgery?
Use crystalloid volume replacement; 3ml of crystalloid for every 1 ml blood lost

– Monitor for hemodilution (PCV, TP, BP)
– Monitor clinical status (CV function, perfusion, BP, HR, etc.)

What can CV depression be exacerbated by?
– Further blood loss
– Anesthetic drugs
– Hypothermia
– Positioning
– Over ventilating

What is considered moderate blood loss?
10-20% of blood volume

What should you do during moderate blood loss?
– May increase surgical rate of bolus crystalloid
– Consider an IV bolus of colloid (several times to expand IV volume w/less risk of peripheral edema)


What is considered a severe loss?
Greater than or equal to 20% of blood volume

What should you do during severe blood loss?
Give fresh whole blood (provides RBCs plus plasma, coagulation factors, etc.); stored has less clotting factors.

What should you give if whole blood is not available?
Combination of PRBC and fresh frozen plasma.

20 ml/kg whole blood will raise hematocrit by what %?

10 ml/kg of packed red cells will raise hematocrit by what %?

What are some signs that transfusion is effective?
– HR normal
– Improved systemic BP
– Increased urine output
– Normal central venous pressure
– Pink MM
– Increased expired CO2 (indicates improved perfusion/cardiac output)

What are some risks of blood transfusion?
Acute hemolytic reaction (intravascular hemolysis) within the first few hours:
– Hypotension
– Tachyardia

Acute hypersensitivity reaction due to histamine release usually within the first 45 minutes
– Hypotension
– +/- tachycardia and urticaria
– Bronchoconstriction

What are some other risks of blood transfusion?
– Delayed hemolytic reaction (3 days to 3 weeks)
– Viral, bacterial contamination
– Cardiac overload
– Citrate toxicity (hypocalcemia)
– Hyperkalemia (old, stored blood)
– Cats (wrong type blood given — A vs. B)

How can you prevent transfusion reactions?
– Universal donors
– Cross-match (especially if previous transfusion, ALL cats)
– Store blood properly
– May pre-treat w/diphenhydramine or glucocorticoids

What is cross-matching in cats? What happens if A blood is given to a B cat?

AB antigen blood group system; A, B, or AB

A positive: MOST cats
B positive: SOME cats; 95% of B cats possess IgM anti-A

If A blood is transfused into B cats, rapid destruction results in severe clinical reactions; hypotension, apnea, AV-block within a few minutes.

Dog erythrocytes antigen
8 DEA recognized.

Universal donor: DEA 1.1; safer to use in a dog that has never been transfused

Ideally, you should know the blood type and do a cross-match.

Increased risk of hemolytic disease with subsequent transfusions.

What is the lethal triad?
– Hypothermia
– Acidosis
– Coagulopathy

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