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Principles of Monitoring & Fluid balance > Perioperative Fluid Management > Flashcards

Perioperative Fluid Management Flashcards

1
Q

What factors can cause patients undergoing GA to be hypovolemic?

A

NPO status
Trauma
Evaporation
Dry anesthetic gases

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2
Q

What complications are associated with a hypovolemic patient?

A

PONV
Organ dysfunction
Prolongation of hospital stay

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3
Q

What are the goals of fluid therapy?

A

Avoid or correct a hypovolemic state
Restore intravascular volume
Maintain O2 carrying capacity

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4
Q

What is the ultimate objective of fluid therapy?

A

To maintain adequate tissue perfusion, poor perfusion is associated with poor outcomes following surgery

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5
Q

What is the predominate substance in the body?

A

Water, about 45-75% of body weight

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6
Q

What factors determine total body water?

A

Age, gender and body habitus

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7
Q

What are the normal values for body water distribution in adults, infants and the elderly?

A 
Avg. 70kg Male 60% TBW
Avg. 70kg Female 55% TBW (more fat)
Premature infants 80-90% TBW
Term infants 75% TBW
Elderly 50-55% TBW
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8
Q

Define volume of distribution.

A

The apparent volume of body water that the drug appears to distribute to produce a drug concentration to that in the blood

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9
Q

What population has an increased volume of distribution for water soluble drugs?

A

Infants, more TBW than other populations

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10
Q

What population has an increased volume of distribution for lipid soluble drugs?

A

Obese patients, more fat to distribute

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11
Q

What primarily regulates the extracellular volume?

A

Body sodium balance

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12
Q

What primarily regulates the intracellular volume?

A

Body water balance

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13
Q

How are the body fluid compartments divided in the body?

A

Total body water 60%
ECF 20% ICF 40%
Plasma 4% Interstitial fluid 16%

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14
Q

What determines the tonicity and the osmolarity of the extracellular fluid?

A

Sodium concentration

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15
Q

What is a typical blood volume of an adult and what are its contents?

A

About 5L
2L Red cell volume
3L Plasma

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16
Q

What part of the body fluid are the red blood cells?

A

Red cell volume is actually considered part of the ICF

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17
Q

What mechanism cause water to move between the ICF and ECF?

A

Osmosis, from low solute concentration to high concentration

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18
Q

What determines osmotic pressure?

A

Osmotic pressure is proportional to the number of ions, not the molecular weight

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19
Q

Define osmolality?

A

Refers to the number of osmotically active particles per kilogram of water

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20
Q

How is osmolality calculated?

A

(Serum Na x 2) + blood glucose + blood urea

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21
Q

Why don’t we use osmole as a unit of measurement in medicine?

A

Too large in expressing osmotic activity of solutes in body fluids, miliosmoles (1/1000 osmole) is commonly used

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22
Q

Define Osmolarity?

A

Refers to the number of osmotically active particles per liter of solution, another way to express the concentration of a solution

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23
Q

What term is easier to use when referring to the body?

A

Osmolarity, body fluid already in liters

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24
Q

What does tonicity measure?

A

Measures the particles which are capable of exerting an osmotic force

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25
Q

Define what it means to have an isotonic solution.

A

The same osmolarity, no osmotic pressure is generated across cell membranes

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26
Q

What are the most commonly used isotonic solutions?

A

LR, NS

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27
Q

Define what it means to have a hypotonic solution?

A

The solution has a lower osmolarity than the plasma

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28
Q

Define what it means to have a hypertonic solution?

A

Solution with a higher osmolarity than plasma

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29
Q

What are the four components of Starling forces?

A

Capillary pressure
ISF pressure
ISF colloid osmotic pressure
Plasma colloid osmotic pressure

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30
Q

What is the pressure exerted by the macromolecules that prevents fluid from leaving the plasma and exerts a pull from the interstitial space

A

Colloid oncotic pressure, about 25mmHg

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31
Q

What does the colloid oncotic pressure use to maintain plasma volume?

A

Proteins
Albumin
Gamma globulins

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32
Q

Which of Starling’s forces can be controlled by the anesthetic provider?

A

Capillary hydrostatic pressure –> vasoactive agents

Capillary oncotic pressure –> giving crystalloids

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33
Q

Where does primary exchange of IVF and EVF take place?

A

Capillaries and small post capillary venules

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34
Q

What are the two most important components of exchange between the IVF and the EVF?

A

Bulk flow

Diffusion

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35
Q

Why are large volumes required when replacing with crystalloid?

A

It is rapidly distributed throughout the ECF

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36
Q

Approximately how much crystalloid is required to expand the intravascular compartment by 1 liter?

A

3-4L

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37
Q

What occurs when D5W is administered?

A

Glucose initially osmotically active but then rapidly metabolized, leaving free water without eletrolytes

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38
Q

How much D5W would be required to replace 500mL of plasma volume?

A

7L which is not suitable for resuscitation or rapid volume replacement

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39
Q

Why don’t we typically give D5W in the OR?

A

Patients are usually stressed –> increased cortisol –> increased blood sugar

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40
Q

What is the most commonly used fluid in the OR?

A

Lactated Ringers, most intraoperative losses are isotonic

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41
Q

Why don’t we use LR to dilute blood?

A

The calcium in the LR binds to the citrate anticoagulant in the blood and may result in clotting

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42
Q

Why might we avoid using LR in renal failure patients in the OR?

A

There is potassium in LR (4mEq) that can cause hyperkalemia

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43
Q

How is LR metabolized?

A

Lactate is converted to bicarbonate in the liver

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44
Q

What is the osmolality of LR?

A

273 making it slightly hypotonic and causes a slight decrease in serum Na

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45
Q

Why don’t we typically use NS in the OR?

A

Greater chloride content, with large volumes this may cause hyperchloremic metabolic acidosis

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46
Q

What is the osmolality of NS?

A

308

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47
Q

How many grams of sodium are in 0.9% NS?

A

9 grams

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48
Q

What are hypertonic solutions predominately used for?

A

Severe hyponatremia

Severe hypovolemic shock or burns

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49
Q

What is the mechanism behind giving a hyper osmotic fluid?

A

Drawls water from the interstitial compartment into the vascular space 12L interstitial > 3L plasma

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50
Q

What are some side effects of hypertonic solutions?

A

Hyperchloremia
Hypernatremia
Cellular dehydration
Limited intravascular duration

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51
Q

What is the purpose of colloid use?

A

Maintaining intravascular volume with the use of large osmotically active molecules

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52
Q

What are some adverse effects to using colloids?

A

Platelet coagulation
Anaphylactic reaction
Reticuloendothelial system (activates phagocytes)

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53
Q

What is the molecular weight of endogenous albumin?

A

69,000 and accounts for 60-80% of plasma colloidal oncotic pressure

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54
Q

How does albumin that leaks out get back into circulation?

A

Lymphatic system

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55
Q

Where is albumin synthesized?

A

Hepatocytes at a rate of 9-12g/day to maintain normal plasma concentration of 40g/L

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56
Q

What kind of solution is 5% albumin?

A

Isotonic

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57
Q

How does 25% albumin affect circulation?

A

Can expand the plasma volume up to 5x the current volume by drawling fluid in from the interstitial fluid

58
Q

How are synthetic colloids typically described?

A

Described by the average or the number averaged molecular weight

59
Q

What is the molecular weight of Dextran 70 and what is it most beneficial for?

A

Dextran 70 = MW: 70,000, it is a better volume expander

60
Q

How are dextran 40 and 70 metabolized?

A

Dextran 40 is small enough to be eliminated by the kidneys where Dextran 70 must pass into the tissues and undergo hydrolysis

61
Q

What is the molecular weight and effects of Dextran 40?

A

MW = 40,000 and it improves blood flow through microcirculation (reduced RBC sludging and reduction in blood viscosity)

62
Q

What is an undesirable side effect of dextran use?

A

Acquired Von Willebrands, reducing both components of factor VIII:
Factor VIII related antigen
FactorVIII coagulant

63
Q

What is the name of the hydroxyethyl starch that is mixed in 0.95% sodium chloride solution?

A

Hespan

64
Q

What is the name of the hydroxyethyl starch that is mixed in a electrolyte solution similar to LR?

A

Hextend

65
Q

What is the significance of the pattern on the hydroxyethyl substitution of hydroxyl starches?

A

It reduces the susceptibility to hydrolysis by non-specific amylases in the blood

66
Q

What problem can occur if HES molecules are too small?

A

They can leak out into the intravascular space, eliminated by the kidneys

67
Q

What problem can occur if HES molecules are too big?

A

Effect blood coagulation, broken down by amylase

68
Q

What is currently the starch of choice and why?

A

Voluven, avoids molecules leaking out and avoids coagulation issues

69
Q

What can occur with long term use of HES?

A

Storage of HES molecules in the reticuloendothelial system

70
Q

What determines if a crystalloid or a colloid should be used in a particular situation?

A

Crystalloids are generally used as maintenance fluid for insensible losses and as replacement for body fluid deficits
Colloids are used for fluid replacement and shock resuscitation

71
Q

How much fluid can 1g of colloid drawl into the plasma volume?

A

20mL

72
Q

How much does 500mL of albumin or hetastarch 6% increase the plasma volume?

A

500mL

73
Q

What are the major preoperative goals of fluid management?

A 
Meet basal fluid requirements
Replace losses
Restore/maintain hemodynamic stability
Enhance microvascular blood flow --> O2 delivery
Maintain aerobic cellular metabolism
74
Q

What is the formula for oxygen delivery?

A

DO2 = CI (cardiac index) x CaO2 (arterial oxygen content)

75
Q

What causes water and electrolyte losses to occur?

A

Urination

Evaporative loss from skin and lungs

76
Q

How much water does a normothermic patient lose per day?

A

2000mL/day
2500 from normal metabolic rate
May gain 400mL for metabolic water

77
Q

What is the 4-2-1 maintenance estimation calculation?

A

0-10kg = 4mL/kg
11-20kg = 2mL/kg
>20kg = 1mL/kg
Trick: if patient is over 20kg, just add 40mL to their weight in kgs

78
Q

How do we calculate NPO deficits?

A

Maintenance x hours fasting = deficit

This does not account for other loses that occur in the OR

79
Q

What are some causes of abnormal fluid losses?

A

Preoperative bleeding, vomiting, diuresis, diarrhea, bowel prep
Occult losses
Increased insensible losses

80
Q

How are the first three hours of fluid deficits typically replaced?

A

Hour 1 = 1/2 deficit + hourly maintenance
Hour 2 = 1/4 deficit + hourly maintenance
Hour 3 = 1/4 deficit + hourly maintenance

81
Q

What are some causes of obligatory fluid loss?

A

Evaporation, mostly apparent with large wounds (duration and surface are exposed)
Internal redistribution of body fluids (third spacing)

82
Q

What type of tissues are most likely to have third spacing?

A

Trauma, inflammation or infected tissue

83
Q

What does the provider need to know in order to calculate third space losses?

A

Type of procedure
Degree of exposure
Amount of surgical manipulation

84
Q

What is the major determinant in third space fluid replacement?

A

Based on whether the tissue trauma is minimal. moderate or severe

85
Q

How much fluid per kg should considered for third space losses if minimal tissue trauma is thought to occur?

A

1-2mL/kg/hr

86
Q

How much fluid per kg should considered for third space losses if moderate tissue trauma is thought to occur?

A

4-7mL/kg/hr

87
Q

How much fluid per kg should considered for third space losses if severe tissue trauma is thought to occur?

A

8-10mL/kg/hr

88
Q

What components make up the fluid requirements of a surgical patient?

A

Maintenance
NPO deficit
3rd Spacing
EBL

89
Q

What two major risk factors contribute to a conservative provider when it comes to transfusing blood products?

A

Blood borne pathogens

Transfusion reaction

90
Q

How much blood loss can a typical adult tolerate?

A

10% loss of EBV

91
Q

What is the main reason providers decide to transfuse a patient?

A

To maintain O2 carrying capacity

92
Q

At what point should the provider switch from using crystalloids and colloids to blood products?

A

When the danger of anemia outweighs the risk of transfusing

93
Q

What is the ratio of replacing crystalloid to blood volume lost?

A

Isotonic solution of 3mL for each 1 mL of blood loss

3:1

94
Q

What is the ratio of replacing colloid to blood volume lost?

A

1mL for each 1mL of blood loss

1:1

95
Q

What is the ratio of replacing blood components to blood volume lost?

A

Considered a colloid

1:1

96
Q

What does the hematocrit represent?

A

The RBC volume in the intracellular fluid

97
Q

What factors tend to increase blood volume?

A

Physical activity and Muscularity

98
Q

What factors tend to decrease blood volume?

A

Obesity, inactivity and chronic disease

99
Q

How do you calculate the estimated blood volume for adult males and females?

A

Males 75mL/kg

Females 65mL/kg

100
Q

What is the formula for allowable blood loss?

A

ABL = 3 [(EBV x Hct preop) - (EBV x Hct allowed)]

101
Q

How much does one unit of PRBC increase the Hgb and Hct?

A

Hgb 1g/dL

Hct 2-3%

102
Q

At what transfusion rate will the Hgb increase by 3g/dL and the Hct increase by 10%?

A

10mL/kg

103
Q

What should we assess in order to determine blood loss?

A

Suction canister
Sponges
Surgical field

104
Q

How much blood is lost in a full 4x4?

A

10mL

105
Q

How much blood is lost in a full Ray-tech?

A

10-20mL

106
Q

How much blood is lost in a full lap pad?

A

100mL

107
Q

How much blood is lost in wet sponges?

A

20-30% of dry value

108
Q

What is a type specific blood compatibility test?

A

ABO Rh typing only

99.8% compatible

109
Q

What does a type and screen blood compatibility test examine?

A

ABO Rh type and screen for specific antibodies commonly associated with non-ABO hemolytic reactions
99.94% compatible

110
Q

What does a type and crossmatch examine?

A

Confirms ABO Rh typing
Detects antibodies to other blood groups
Detects antibodies in low titers

111
Q

How long does it take to do ABO Rh typing?

A

Less than 5 minutes

112
Q

How long does it generally take to get back antibody titers?

A

May take up to 45 minutes

113
Q

What blood type is the universal donor?

A

O negative

114
Q

If the results of a type and crossmatch become available before transfusing 4 units of O negative blood what should be done?

A

The provider should switch to the crossmatched blood, if >4 O negative transfused STICK WITH IT

115
Q

What are the benefits to using whole blood?

A

It includes the clotting factors and antibodies

116
Q

How much volume is one bag of whole blood?

A

450mL, reserved for mass casualties and EBV loss > 25%

117
Q

How does giving pack red cells differ than giving whole blood?

A

Replaces RBC but not the volume

250-350mL

118
Q

How much does each unit of platelets increase the patients platelet count?

A

5000-10000

119
Q

At what platelet level could spontaneous hemorrhage occur?

A

10-20K

120
Q

About how long will platelets survive post transfusion?

A

About 1 week

121
Q

What does a bag of fresh frozen plasma contain?

A

All clotting factors except platelets, usually about 250mL

122
Q

How do we dose FFP?

A

About 10-15mL/kg

123
Q

About how long does it take FFP to thaw?

A

45 minutes

124
Q

What doses of FFP can be given for warfarin reversal therapy?

A

5-8mL/kg

125
Q

What is cryopreciptate used for?

A

To correct specific coagulopathies because it contains factors VIII, XIII and fibrinogen

126
Q

What transfusion product carries the greatest infectious risk from hepatitis and why?

A

Cryopreciptate, it is pooled from more than one donor

127
Q

What are some major complications associated with transfusions?

A

Immune hemolytic reactions
Immune non-hemolytic reactions
Infections (HIV, Hepatitis)
Metabolic complications

128
Q

What metabolic complications arise from transfusions?

A

Decreased ph from lactate production

Increased potassium from cell lysis

129
Q

When in a coagulopathy complication likely to occur from transfusion?

A

Usually occurs after massive transfusion >10 units

130
Q

What is a major complication associated with replacing blood loss with mass amounts of fluids?

A

Dilutional thrombocytopenia and low clotting factors

131
Q

What pathophysiology can occur with massive transfusions?

A

DIC

132
Q

What is the leading cause of transfusion related deaths in the US?

A

TRALI

133
Q

Explain what a TRALI may look like?

A

Noncardiogenic pulmonary edema, hypoxia HoTN, fever and fluid in ETT

134
Q

What is the treatment for TRALI?

A

Supportive measures

135
Q

What is considered a massive transfusion?

A

Replacement of patients total blood volume in 1/2 EBV in 3hrs
Transfusion of >10units of whole blood

136
Q

What electrolyte abnormality might be seen with massive transfusions and how should it be treated?

A

Hypocalcemia, only replace if ionized Ca levels are low

137
Q

What causes hypocalcemia with massive transfusions?

A

Citrate preservative may bind and chelate calcium

138
Q

When might a provider see cardiac compromise related to hypocalcemia from massive transfusions?

A

In normal patients does not occur unless the transfusion rate exceeds 1 unit every 5 minutes

139
Q

If a surgeon wants to use cell saver during a procedure what does that mean?

A

Blood loss from surgical field are suctioned up, RBC spun down and given back to the patient

140
Q

What should you do if the surgeon says he wants to use inraoperative isovolemic hemodilution during a procedure?

A

Draw off blood before procedure, replace with crystalloid or colloid, when blood loss occurs, Hct will be lower, give the patients blood back after the procedure is complete

141
Q

What are good techniques for transfusing products?

A

Warm the blood
Use a filter (170micrometer)
Reconstitute with NS

142
Q

Why do we reconstitute blood with NS when we use LR in the OR?

A

Calcium in LR may cause blood to clot by reversing the anticoagulant effect of citrate

Principles of Monitoring & Fluid balance (3 decks)

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