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Principles > Principles-Fluid, Electrolytes, and Acid-Base Management > Flashcards

Principles-Fluid, Electrolytes, and Acid-Base Management Flashcards

1
Q

What cation is most important for intracellualar volume regulation and determines osmolality

A

Potassium

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2
Q

What cation is most important for extracellular volume regulation determines osmolality

A

Sodium

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3
Q

What is the normal plasma osmolality

A

280-290 mOsm/kg

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4
Q

** What is the equation for calculating plasma osmolity

A

2XNa + Glucose/18 + BUN/2.8

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5
Q

Crystalloid solutions contain

A

Low-molecular-weight ions (salts)

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6
Q

Colloid solutions contain

A

High-molecular-weight ions (proteins, glucose)

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7
Q

Colloid solutions ——–plasma colloid oncotic pressure

A

maintain

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8
Q

Crystalloid solutions—–rapidly equilibrate with, and distributes throughout?

A

the intravascular and interstitial fluid space

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9
Q

True/False

crystalloids, if given in sufficient amounts, are just as effective as colloids in restoring intravascular volume

A

True

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10
Q

Replacing intravascular volume with crystalloids require how much more volume relative to colloid use

A

3-4 times

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11
Q

Generally, severe fluid deficits are corrected with

A

colloids

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12
Q

Rapid administration of large amounts of crystalloids > 4-5L is associated with

A

significant tissue edema

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13
Q

Solutions are chosen according to what type of fluid loss

A

Isotonic

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14
Q

Most intraoperative fluid losses are

A

isotonic, therefore, solutions are usually isotonic

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15
Q

What is the ratio of cyrstalloid replacement for blood loss

A

3 ml of crystalloid for every 1 ml of blood lost

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16
Q

True/False

Lactated Ringers is the most commonly used fluid in OR

A

True

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17
Q

Is LR considered Isotonic

A

Yes, although it is slightly hypontonic

*least effect on extracellular fluid composition, most closest to physiological solution

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18
Q

LR is less or more osmotic than saline

A

Less (273 vs. 308)

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19
Q

LR contains which electrolytes

A 
Tonicity- 273
Na-130 mEq
Cl-109 mEq
Potassium-4 mEq
Ca- 3 mE1
Lactate- 28 mEq/L
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20
Q

Infusion of 1L of LR will add approx. how much volume to plasma after 1 hr

A

150-185 mL

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21
Q

LR should be administered with caution in which type of patient

A

kidney failure due to potassium

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22
Q

NS contains which electrolytes

A

Tonicity-308
Na-154
Cl-154

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23
Q

When given in large amounts, NS can produce —-, why?

A

hyperchloremic Acidosis, due to higher cloride content

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24
Q

Infusion of 1L of NS will contribute to how much volume increase in the plasma after 1h

A

275 mL

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25
Q

Which crystalloid is better for patient’s with renal failure

A

Nacl

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26
Q

What is the intravascular half-life of crystalloids

A

20-30 minutes

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27
Q

What is the intravascular half-life of colloids

A

3-6 hours

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28
Q

Name two indications for colloid use

A

Severe intravascular fluid deficit where RBC not available

Severe loss of protein (albumin)

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29
Q

Infectious transmission or anaphylactoid rxns are associated with which two colloids

A

Albumin (infection)

Dextran (anaphlactic/anaphylactoid)
-assoc. with renal failure

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30
Q

Hespan is a colloid that contains

A

Starch

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31
Q

Are there risks of transmitting infectious diseases, or anaphylactoid rxns with hespan

A

NO- synthetically made

-lowest risk of anaphylactoid

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32
Q

Large volume administration of hespan interferes with

A

blood clotting

*Don’t exceed 20 mL/kg

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33
Q

A unit of PRBC contains how much volume

A

250mL

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34
Q

A unit of PRBC has a hematocrit of

A

70%

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35
Q

How high will a unit of PRBC increase the Hgb/Hct

A

1 g/dL- hemoglobin
2-3%- hematocrit
*if only given RBC

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36
Q

One unit of platelet will increase count by

A

10,000-20,000

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37
Q

What is the goal for introperative fluid requirements

A

maintain an adequate intravascular volume

end-organ perfusion and oxygenation

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38
Q

What four criteria are used when calculating intraoperative fluid requirements

A

maintaining baseline fluid requirements
NPO deficit replacement
intraoperative fluid shift replacement
blood loss replacement

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39
Q

How is maintenance requirements calculated

A

4-2-1 Rule
1st 10 kg, give 4 mL/kg/hr
next 10 kg, give 2 mL/kg/hr
each kg above 20 kg, add 1 mL/kg/hr

  • Easiest way, add 40 kg to patient’s wait
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40
Q

How is NPO deficit calculated

A

maintenance rate (IV) x number of hours NPO

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41
Q

How is NPO deficit replaced

A

in first hour, give 50%
in second hour, give 25%
in third hour, give 25%

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42
Q

Blood loss should be replaced with

A

crystalloids or colloids to maintain intravascular volume until anemia outweighs risk of transfusion

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43
Q

A healthy patient can tolerate a hgb as low as

A

7 g/dL

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44
Q

Elderly patients, or those with significant cardiac/pulmonary disease must have a hemoglobin level of at least

A

10 g/dL

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45
Q

How is hemoglobin calculated based on hematocrit

A

hgb=hct/3

46
Q

What should the crystalloid to blood loss replacement ratio be

A

3: 1

i. e. if patient lost 100 mL of blood, give 300 mL of crystalloid

47
Q

What should the colloid-to-blood loss replacement ratio be

A

1:1

48
Q

How low should the hemoglobin be to transfuse

A

depends on the patient

49
Q

What is the Maximum Allowable Blood Loss (MABL)

A

A rough estimate of how much blood the patient can lose

50
Q

When would the MABL not apply

A

hemodynamic instability or patient in need of oxygen carrying capacity

51
Q

Describe how to calculate the MABL

A

1st- estimate patient’s blood volume (EBV)
2nd- estimate red cell mass (preop hct x EBV)
3rd- estimate the lowest acceptable hct loss x EBV
4th- subtract 3 from ERCM at preop hct
* this is the volume of rbc that would be lost if patient were to bleed to lowest acceptable hct
5th- multiply 4 by 2, then by 3 (this gives the range)- to account for plasma volume

52
Q

What is the expected blood volume for a premature neonate

A

95 mL/kg

53
Q

What is the expected blood volume for a full-term neonate

A

85 mL/kg

54
Q

What is the expected blood volume for an infant

A

80 mL/kg

55
Q

What is the expected blood volume for an adult male

A

75 mL/kg

56
Q

What is the expected blood volume for an adult female

A

65 mL/kg

57
Q

How is the Estimated Blood Volume determined (EBV)

A

multiplying patient’s weight by their expected blood volume

58
Q

What are the guidelines for replacing fluids for evaporation, and/or fluid shifts intravascularly

A

The degree of tissue trauma from procedure determines fluid requirements

Minimal tissue trauma, give 1-2 mL/kg/hr
Moderate tissue trauma, give 2-4 mL/kg/hr
Severe tissue trauma, give 4-4 ml/kg/hr

59
Q

Two causes of hyponatremia

A

sodium loss

free water excess

60
Q

How is plasma osmolality affected by sodium deficits

A

decreased-hypoosmolality

61
Q

Hypoosmolality r/t sodium deficit cause fluid to shift

A

into cells (swelling) and plasma volume to decrease leading to hypovolemia

62
Q

HypoNatremia r/t free water excess cause

A

both ICF and ECF volume to increase leading to hypervolemia, water intoxication with cerebral and pulmonary edema

63
Q

Sodium levels of > 125 mEq/L are

A

asymptomatic

64
Q

Sodium levels of < 120 mEq/L causes

A

lethargy, confusion, seizures, coma

65
Q

What is the treatment of choice for decreased total body sodium content

A

Isotonic Nacl

66
Q

What is the treatment of choice for normal or increased total body sodium (water excess)

A

Water restriction

67
Q

Rapid correction of hyponatremia can lead to what syndrome

A

Osmotic Demyelination Syndrome

68
Q

What are the symptoms of Osmotic Demyelination Syndrome

A

transient behavioral disturbances
seizures
permanent demyelination and nerve damage

*No cure

69
Q

Osmotic Demyelinaton Syndrome can be prevented by

A

Correction < 2.5 mEq/L per hour

70
Q

Never correct hypoNatremia any faster than

A

1.5 mEq/L per hour

71
Q

Why would patient’s with hypoNatremia be more sensitive to the myocardial depressant effects of anesthetics

A

Hyponatremia decreases the excitablilty of cells and may contribute to decreased myocardial contractility

72
Q

What are the three anesthetic questions that must be asked on any electrolyte disturbance

A

What underlying disorder is present?

Is the case elective or urgent?
-must be > 130 for elective cases

Is the patient hypovolemic or hypervolemic?

  • hypovolemic= more sensitive to volatile/IV anesthetics (decrease doses needed)
  • hypervolemic= pulmonary edema, alveolar edema, impaired gas exchange
73
Q

Hypernatremia is always associated with what osmolality change

A

hyperosmolality

  • fluid shift from cells to interstitial space of brain leading to shrinkage with tearing of meningeal vessels, and intracranial hemorrhage
74
Q

How to treat hypernatremia associated with hypovolemia

A

correct hypovolemia first with NS (restores intravascular volume)

then, correct hypernatremia with hypotonic fluids (draws fluid into cells)

75
Q

How to treat hypernatremia associated with hypervolemia

A 
diuretics (enhances sodium removal) 
hypotonic solution (replaces water deficit)
76
Q

Plasma sodium should not be decreased faster than

A

0.5 mEq/L/hr

77
Q

Hypernatremia affects MAC how

A

increases

78
Q

What is the normal plasma potassium

A

3.5-5 mEq/L

79
Q

HypoKalemia is associated with

A

cardiac rhythm disturbances

80
Q

True/False

Chronic hypoKalemia has fewer incidences of intraoperative dysrhythmias

A

True

81
Q

What are six causes of hypokalemia

A 
Intracellular movement of potassium
Increased potassium losses
Hypomagnesemia 
Diuretics
Hypersecretion of aldosterone
GI losses
82
Q

What are the three ECG manifestations of hypokalemia

A

T-wave flattening and inversion
Formation of a U wave
ST depression

83
Q

What effect does hypokalemia have on the excitablility of the heart

A

delayed ventricular depolorization-hyperpolarization

decreased cardiac contractility

84
Q

What are the four ECG manifestations of hyperkalemia

A

Peaked T waves
Prolonged PR interval
Progressive QRS widening to “sine wave”
ST segment depression

85
Q

Name three ways to treat hyperkalemia

A

Stabilization of membrane
-calcium chloride ( decreases membrane excitability)

Increase potassium movement intracellularly

  • hyperventilation
  • glucose + Insulin (50g glucose/10 Units of Insulin)
  • bicarbonate if acidotic
  • beta agonist- epinephrine

Increase Potassium excretion

  • diuretics
  • hemodialyis
  • kayexelate
86
Q

A 10mmHg decrease in PaC02 decreases serum potassium concentration by

A

0.5 mEq/L

87
Q

What is the normal calcium concentration

A

8.5-10.5 md/L

88
Q

What effect does calcium have on nerve tissue

A

hyperexcitable

-calcium stabilizes membrane of cells, so lack thereof would cause excessive excitability

89
Q

What are classic signs of hypocalcemia

A

Chvostek’s sign- tap jaw, excites facial mu
Trousseaus’s sign- carpal spasms when tourniquet applied

Prolonged QT interval

90
Q

What are classic signs of hypercalcemia

A

SHORTENED QT INTERVAL

lethargy, N/V, irritability

91
Q

Which acid/base disorder should be avoided in hypercalcemia

A

acidosis

  • avoid alkalosis in hypocalcemia
  • alkalosis decreases ionized calcium
92
Q

Hypophosphatemia has similar fluid shift behaviors as what electrolyte deficit

A

hypokalemia

93
Q

Hyperphophatemia has what effect on calcium

A

lowers plasma levels via precipitation and deposition into bone/soft tissues

94
Q

What is the normal magnesium concentration

A

1.7-2.1 mEq/L

95
Q

Low levels of magnesium are directly proportional to what two electrolyte disturbances

A

hypocalcemia

hypokalemia

96
Q

How does hypermagnesemia effect CNS, skeletal muscles, heart tissues, and respiratory system

A

sedation
muscle weakness
myocardial depression
respiratory depression

97
Q

How does hypermagnesemia effect NMB

A

potentiates it by antagonizing calcium at the pre-synaptic NM junction

98
Q

Clinically, what is the cause of acidosis

A

low-perfusion lactic acidosis (metabolic acidosis)

hypoventilation (respiratory acidosis)

99
Q

Clinically, what is the cause of alkalosis

A

diuretic therapy (metabolic alkalosis)

hyperventilation (respiratory alkalosis)

100
Q

Alveoloar gas equation reflects

A

alveoloar oxygenation (PA02)

*Always greater than Pa02

101
Q

Define anion gap

A

the difference between the serum sodium and the sum of chloride and bicarbonate concentration

normal=8-16

102
Q

Define base excess

A

difference between the normal quanity of Total buffer base and the buffer base calculated from a blood sample

Normal BE is -2 to +2

Elevation=increase in serum bicarbonate
Reduction=reduced serum bicarbonate

103
Q

Define compensation

A

alteration in bicarbonate or PaCO2 in direct response to a primary acid-base disturbance

104
Q

Define hypocapnia

A

reduced PaC02 (<35 mmHg)

105
Q

Define hypocarbia

A

reduced HCO3 ( < 22 mEq/L)

106
Q

What is the normal oxygen saturation

A

95-98%

107
Q

What effect does acidemia have on anesthetic agents

A

potentiates CNS and CV depressant effects of anesthesia

108
Q

Lactated ringers has what effect of bicarbonate concentrations and pH

A

increases bicarb concentrations and pH

via metabolism of lactate to bicarbonate

109
Q

Normal saline has what effect of bicarbonate concentrations and pH

A

decreases bicar concentrations and pH

-increased chloride ions leads to decreased bicarbonate leading to decrease in pH

110
Q

If a patient’s pH <7.2 and I have to administer sodium bicarbonate, how is the initial dose calculated

A

sodium bicarb= 0.3(24mEq/L - Actual HCO3)/2

111
Q

What are the three negative effects of administering sodium bicarb for metabolic acidosis

A

increase sodium levels
generates C02
decreases plasma potassium levels

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