Blue Book Flashcards
volume concentration formula
V1 x C1 = V2 x C2
The predicted hematocrit of a 75 kg patient with a hematocrit of 30% and a circuit priming volume of 2200mL would be determined by:
V1 = 70 ml x 75 kg = 5250 blood volume
V2 = 5250 +2200 = 7450 total volume on bypass
C1 is .30 (present hematocrit)
V1 x C1 = V2 x C2 5250 x .30 = 7450 x C2 1575 = 7450 x C2 .211 = C2 the concentration or hematocrit on bypass is 21.1%
If a desire hematocrit is 25% on a 75 kg patient with a starting hematocrit of 30% and a priming volume of 2200. What formula can we use to see how much PRBCs need to be given?
V1 x C1 = V2 x C2
V1 x C1 = 5250 x .30 = 1575 patients RBC volume
v2 x C2 = 7450 [this is v1 + priming volume] x .25 = 1862.5 RBC volume for 25 hct
186.25 - 1575 = 287.5 RBCs needed
hematocrit of packed RBC is 70%
287.5/.70 = 410.7 mL of packed RBCs needed for hct of .25
what is the hematocrit of PRBC
70%
If it is necessary to add crystalloid solution to a patient and you wanted to find out new hct. What formula would you use?
75 kg patient with hct of 30% and a circuit priming volume of 2200 mL and you add 500 mL crystalloid to patient
V1 = (70 mL x 75kg) + 2200 = 7450 volume on bypass C1 = .35 Hct on bypass V2 = (70mL x75 kg)+2200+500 = 7950 volume after adding C2 = ?
7450 x .25 = 7950 x C2
.23 = C2 the new hct after adding 500 mL crystalloid
If a 350 mL of packed RBCs is added to a patient. How would you find out the new hct?
the RBC volume divided by the total volume equals the hct. The hct of PRBC is usually 70%
.70 x 350 = 245 mL RBCs
7450 [volume on bypass] x .25 = 1862.5
7950 [volume after adding 500]
1862.5 +245 [how many RBCs we added] / 7950+350 [volume]
= .25 new hct after adding 350 ml of packed RBCs
the goal of adequate heparinization is to maintain the patient’s ACT at
480 seconds
Why might a patient require additional heparin doses after the initial administration?
AT3 deficiency due to long hospital stays and heparinization
If additional heparin is given and does not help the anticoagulation status, what may be necessary?
give FFP containing AT3 or the specific component
why might the arterial line pressure rise greatly during test transfusion?
- cannula may be occluded by the aortic wall
- may be protruding into the media which could cause a dissection
Why might blood from the patient be removed after cannulation via the venous cannula?
- preserve platelets and clotting factors that would be lost during bypass for reinfusion at the end since blood has platelets, clotting factors, and red blood cells
what is the disadvantage of removing blood from the patient after cannulation but before going on bypass?
the hct of the patient drops for the bypass run
causes of aortic cannula high line pressure when initiating bypass
- kink in arterial cannula or line
- cannula improperly positioned
- clamp too near cannula when cross clamp applied
- cannula too small
- arterial systemic blood pressure very high
- aortic dissection
- blockage in arterial filter
what is the maximum acceptable electrical leakage?
100 microamperes
what is normal pulmonary artery pressure
25/8
where does the swan-ganz catheter go?
through the internal jugular vein, into the right atrium and out into the pulmonary artery
what are the circulating catecholamines
epinephrine and norepinephrine
what are catecholamines secreted by?
adrenal medulla
why does the blood pressure drop when going on bypass?
- circulating catecholamines due to dilution
- reduced systemic vascular resistance
what happens later in the surgery in terms of catecholamines?
large amounts of catecholamines are released by the reaction of the sympathetic nervous system due to stress of surgery
what can hypertension cause when on pump?
- leaking around suture and cannulation sites
- pump line pressure may rise
what can help fix hypertension on pump?
- lowering flow
- sometimes giving anesthetic agents is all that is needed
for every __ C that the patient is cooled, the oxygen consumption is decreased by __
7C that the patient is cooled, the oxygen consumption is decreased by 50%
pros and cons of normothermic bypass
- less platelet dysfunction
- requires higher flows that may increase blood trauma
if cooling is used as a temperature gradient less than ___C between the arterial and venous blood is maintaned
less than 10 C
why do we keep a gradient when cooling the patient
prevents the formation of micro bubbles
why might oxygen saturations are falling?
- not adequately paralyzed and may be experiencing subclinical shivering: more paralyzing agents
- blood flow may not be high enough
- may need to cool patient if oxygen saturations cannot be sustained
average adult’s blood flow to the brain is about
750 ml/min
blood flow to the coronary arteries is about
225 ml/min
blood flow to various organs while at rest or on bypass are:
brain - 15%
heart - 4-5%
kidneys - 27%
liver - 29%
the kidneys receive about _% of the cardiac output but only require __% of the body’s oxygen
25% of cardiac output but only require 7% of the body’s oxygen
how does retrograde cardioplegia travel
travels through the coronary veins, capillaries, arteries, and then exits into the aorta where it must be removed by venting
how does antegrade cardioplegia travel?
exits into the right atrium where it is removed by the venous cannula
why is warm cardioplegia used prior to cross clamp removal?
- uniformly warm the heart and provide arrest during the early reperfusion period
- warm dose flushes the coronary arteries of detrimental metabolic products and air accumulated during the cross clamp period
- replenishment of high energy phosphates
warming the blood too rapidly could cause what?
red blood cells to absorb fluid causing hemolysis
what is one of the problems with femoral bypass?
lack of venting and decompression of the heart
the hct on bypass is kept from
22-29%
this reduced hct circulating solution perfuses the capillaries and tissues better than blood with normal hct
why is a lower than normal hct better for perfusing arterioles and capillaries?
arterioles have an average critical closing pressure of 20 mmHg and this reduced viscosity helps to maintain flow and pressure
what does adding large amounts of crystalloid cause and what should be done to fix it?
large amounts of crystalloid solution may decrease the colloid osmotic pressure and cause third spacing of fluid
- 25% albumin should be added
- patients with decreased serum albumin and colloid pressure become edematous, often preventing closure of sternum
