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From Flashcardlet > Clinical Lab Med 5 - Sodium > Flashcards

Clinical Lab Med 5 - Sodium Flashcards

1
Q

What percentage of a males body is water?

A

60%

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2
Q

What percentage of a female’s body is water?

A

50%

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3
Q

What fraction of the total body water is found in the ICF?

A

2/3

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4
Q

What fraction of the total body water is from in the ECF?

A

1/3

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5
Q

Where is the ECF located?

A

Vascular and interstitial fluids

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6
Q

What does water follow?

A

Salt

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7
Q

What are changes in the ECF volume dictated by?

A

Net gain or loss of sodium

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8
Q

What happens to the osmolality of the ECF if fluid loss is isotonic?

A

Osmolality is essentially unchanged

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9
Q

What is an example of isotonic fluid loss?

A

Blood loss

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10
Q

What is an example of hypotonic fluid loss?

A

NG suction, sweating

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11
Q

What happens to the osmolality of the ECF if fluid loss is hypotonic?

A

Increased osmolality

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12
Q

What happens to the shift of fluid if fluid loss is hypotonic?

A

Shift of ICF to ECF

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13
Q

What type of patients typically present with hyponatremia?

A

Common in hospitalized patients

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14
Q

What kind of volume levels present with hyponatremia?

A

Typically hypovolemic

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15
Q

What happens to the BUN/Cr ratio during hyponatremia?

A

Elevated BUN:Cr ratio

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16
Q

Why do hyponatremia patients present with hypovolemia?

A

Water follows salt

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17
Q

What is the BUN:Cr ratio of a hyponatremic patient?

A

Above 20:1

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18
Q

Why does an elevated BUN:Cr present with hyponatremia?

A

Kidney filters waste, so if volume is depleted, the kidney is not perfused and it can’t filter fluid, so nitrogenous wastes build up and increase BUN

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19
Q

What are two other instances when an elevated BUN:Cr ratio presents?

A

GI bleed, excessive amounts of protein intake (body builders)

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20
Q

What are two aspects of renal sodium loss?

A

High urinary sodium excretion and high urinary osmolaltiy

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21
Q

What is renal sodium loss most commonly due to?

A

Diuretics

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22
Q

What is a less common cause of renal sodium loss?

A

Renal tubular disease - salt wasting nephritis

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23
Q

What presents with renal tubular disease?

A

Acute tubular necrosis, tubular damage secondary to prolonged urinary tract obstruction

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24
Q

What causes acute tubular necrosis?

A

Prolonged hypotension - tubules die because they were not perfused due to decreased blood pressure

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25
Q

What are some cases of extra renal sodium loses?

A

Diarrhea
Fever
Sweat/exercise

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26
Q

What is an aspect of extra renal sodium loss?

A

Low urine sodium excretion

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27
Q

What is the reference range for sodium levels?

A

135-145

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28
Q

What is a rare cause of hyponatremia?

A

Decrased sodium intake

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29
Q

What type of patients have decreased sodium intake?

A

People with poor diets - anorexic, alcoholic

Hospital patients that are maintained on hypotonic IV fluids

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30
Q

Why is urine osmolality high with hyponatremic patients?

A

ADH prevents loss of fluid, so concentration of urine results

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31
Q

How is hyponatremia classified?

A

Volume status and/or osmolarity

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32
Q

What factors do we consider when classifying hyponatremia?

A
  • Patient history
  • Volume status
  • BUN:Cr
  • Urine osmolality
  • Plasma osmolality
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33
Q

What are some examples of a patient’s history that influence diagnosis of hyponatremia?

A

Diabetic? High cholesterol?

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34
Q

What are two volume statuses that affect hyponatremia?

A

Hypervolemia, hypovolemia

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35
Q

What symptoms present with hypervolemic hyponatremia?

A

Edema ascites

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36
Q

What symptoms present with hypovolemic hyponatremia?

A

Orthostasis, dry mucous membranes, tenting of skin

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37
Q

What is a physical finding?

A

Something you can see, touch, smell, taste, or hear

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38
Q

What value of increase in fluid volume results in edema?

A

10-15% increase in fluid volume

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39
Q

What is orthostasis?

A

When a patient goes from laying to sitting to standing, their pressure drops and heart rate increases to compensate

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40
Q

What plasma osmolality is typically associated with hyponatremia?

A

Plasma hypoosmolality

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41
Q

What is the formula to calculate plasma osmolaltiy?

A

(2xNa) + (Glucose/18) + (BUN/2.8) = plasma osmolality

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42
Q

What is the reference range for plasma osmolality?

A

280-295

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43
Q

What is the plasma osmolality of a patient with Na=140, Glucose=360, BUN=28?

A

(2x140)+(360/18)+(28/2.8) = 310 (hypertonic)

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44
Q

What is a typical condition that presents with hypertonic hyponatremia?

A

Uncontrolled diabetes

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45
Q

Why does uncontrolled diabetes associate with hypertonic hyponatremia?

A

Increased glucose (solute in the ECF) causes water to move into the ECF, so sodium concentration in the ECF is diluted

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46
Q

How do we treat hypertonic hyponatremia?

A

Correct the hyperglycemia

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47
Q

What do we not do to treat hypertonic hyponatremia?

A

Do not give saline - it will cause fluid to leave the ICF even more

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48
Q

What is the grading scale for edema?

A

1 - pit fills back in

4 - pit is still there

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49
Q

Where do we look to check for pitting?

A

Look at a dependent area - legs when standing, sacrum in bed

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50
Q

Where do we test for pitting?

A

Press on tibial crest

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51
Q

What is ascites?

A

Fluid in the abdominal cavity

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52
Q

What are two causes of pseudohyponatremia?

A

Hyperlipidemia

Hyperproteinemia

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53
Q

What condition causes hyperproteinemia?

A

Multiple myeloma causes amyelodosis, increasing proteins

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54
Q

Explain pseudohyponatremia

A

Proteins and lipids are usually 7% of plasma, while 93% of plasma is water. If increased levels of proteins/lipids are present, the percentage of water in the plasma decreases. When measuring sodium, lab counts the number of Na particles, not the concentration, so it seems as though Na levels decreased

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55
Q

What factor do we need to look at when diagnosing hypotonic hyponatremia?

A

Volume status

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56
Q

What are two different causes of hypotonic hyponatremia with hypervolemia?

A

Renal failure

CHF/hepatic cirrhosis

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57
Q

What is the urine sodium level of renal failure hypotonic hyponatremia with hypervolemia?

A

Greater than 20 meq/L

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58
Q

What it the urine sodium level of CHF/cirrhosis hypotonic hyponatremia with hypervolemia?

A

Less than 20 meq/L

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59
Q

How does renal failure result with hypotonic hyponatremia with hypervolemia?

A

Kidney is supposed to filter off fluid, but if in renal failure, volume increases and urine output decreases

60
Q

How does CHF cause edema?

A

Left ventricular failure
Decreased ejection fraction
Volume increases in LV
Pressure increases in LV
Volume backs up into LA
Volume backs up into lungs
Pressure increases in capillaries and fluid leaks out
Alveoli get wet, causing SOB, crackles, rales, pulmonary edema
Fluid even backs up to IVC/SVC and fluid leaks out into dependent areas

61
Q

What spaces does fluid move to and from during edema?

A

Fluid plasma into interstitial fluid

62
Q

How does cirrhosis cause edema?

A

Cirrhosis makes liver hard and small, liver is supposed to detoxify all wastes in volume, but the liver can’t handle the volume and fluid in vessels leak out into the abdominal space (ascites)

63
Q

What does the loss of fluid from the plasma lead to the production of?

A

Brain realizes that body is losing fluid - Production of ADH and aldosterone

64
Q

Why does ADH and aldosterone lead to hyponatremia?

A

Body holds onto volume, so Na is diluted - renal excretion of both sodium and water is impaired but rise in total water exceeds rise in sodium

65
Q

What is the treatment of hypotonic hyponatremia with hypervolemia?

A

Restriction of sodium

Fluid restriction

66
Q

What are the values of a sodium restriction?

A

1-3 grams/day

67
Q

What are the values of a fluid restriction?

A

1-1.5 L/day

68
Q

What must water intake be in terms of urine output?

A

Water intake must be less than urine output to raise plasma sodium

69
Q

What happens when diuretics like Lasix are used with CHF, in terms of Na levels?

A

Decreased Na levels`

70
Q

What are two ways hypotonic hyponatremia with hypovolemia is caused, generally?

A
  • Total body sodium is depleted disproportionately to water losses
  • Sodium deficit is replaced with hypnotic fluids
71
Q

What is the urine sodium level with renal losses in hypotonic hyponatremia with hypovolemia?

A

Urine sodium is greater than 20 meq/L

72
Q

What causes renal losses with hypotonic hyponatremia with hypovolemia?

A
  • Diuretic therapy

- Adrenal insufficiency or ACE inhibitors

73
Q

What is a disease that is associated with adrenal insufficiency?

A

Addison’s Disease

74
Q

What is the urine sodium level with extra-renal losses in hypotonic hyponatremia with hypovolemia?

A

Urine sodium is typically less than 20 meq/L

75
Q

What causes extra-renal losses with hypotonic hyponatremia with hypovolemia?

A
  • Diarrhea
  • Vomiting
  • Sweat
76
Q

With hypotonic hyponatremia with hypovolemia, what tare the clinical manifestations due to?

A

Clinical manifestations are usually due to volume depletion rather than hyponatremia

77
Q

What is the treatment of hypotonic hyponatremia with hypovolemia?

A

Re-expansion of the ECF volume with isotonic saline

Correction of any underlying disorders

78
Q

What causes hypotonic hyponatremia with euvolemia?

A

Primary polydipsia

SIADH

79
Q

How does primary polydipsia cause hypotonic hyponatremia with euvolemia?

A

Excessive water intake causes dilution of the sodium concentration

80
Q

What is the urine sodium content with hypotonic hyponatremia with euvolemia?

A

Considerably less than 20 meq/L

81
Q

What is the urine osmolality with hypotonic hyponatremia with euvolemia?

A

Urine osmolality is less than 100 moms/kg

82
Q

What type of patients usually have hypotonic hyponatremia with euvolemia?

A

Psychiatric patients

83
Q

How much water needs to be taken in in order to produce hypotonic hyponatremia with euvolemia?

A

Patient would need to take in more water than maximal urine volume, 10-15 L/day!

84
Q

What is the treatment of hypotonic hyponatremia with euvolemia?

A

Water restriction, monitors plasma sodium

85
Q

What does SIADH stand for?

A

Syndrome of inappropriate anti diuretic hormone

86
Q

What is one of the most common causes of hyponatremia?

A

SIADH

87
Q

When does SIADH occur?

A

If volume is normal, no ADH is produced. But if there is a brain tumor or lung tumor with small cell carcinoma, the tumor produces ADH - holds onto fluid and dilutes the Na concentration

88
Q

What is dilutional hyponatremia?

A

Disorder of fluid and electrolyte balance caused by excessive release of ADH

89
Q

What does ADH do?

A

DH stimulates maximum water conservation and concentrates the urine

90
Q

What does fluid and electrolyte imbalance in dilutional hyponatremia result from?

A

Inability to excrete dilute urine
Retention of water within the body
Low sodium levels

91
Q

What is a specific example of dilutional hyponatremia?

A

SIADH

92
Q

What are the characteristics of dilutional hyponatremia?

A
  • Low serum sodium and osmolality
  • Adequate urine sodium excretion
  • High urine osmolality
  • No edema
  • No evidence of dehydration
  • No appropriate cause for ADH
93
Q

Why do we say that there is no appropriate cause for ADH secretion in dilutional hyponatremia?

A

Excretion of urine that is less than maximally diluted in a patient with low osmolality and normal or slightly increased intravascular volume

94
Q

What conditions does dilutional hyponatremia result from?

A

Lung disease
Malignancy
CNS abnormalities
Cortisol deficiency

95
Q

Why does cortisol deficiency produce dilutional hyponatremia?

A

Cortisol inhibits ADH secretion

96
Q

How do we diagnose SIADH?

A

Diagnosis of exclusion

97
Q

What are the initial manifestations of hyponatremia?

A
  • Headache
  • Nausea
  • Malaise
  • Lethargy
  • Cramps
98
Q

What are the progressions of the manifestations of hyponatremia?

A
  • Delirium
  • Psychosis
  • Seizures
  • Coma
99
Q

When are manifestations of hyponatremia observed?

A

Sodium concentration less than 120 meq/L or if the rate of fall in sodium concentration is rapid

100
Q

When is the treatment of hyponatremia urgent?

A

When sodium concentration is less than 110 meq.L or if the patient is symptomatic

101
Q

Why can’t sodium deficit be corrected too quickly?

A

May cause acute or permanent neurological damage - central pontine myelinolysis when myelin tears away from axons

102
Q

What should the rate of increase in plasma sodium not exceed?

A

Should not exceed 0.5 meq/L per hour or 12 meq/L per day

103
Q

What should the rate of increase in plasma sodium not exceed in patients exhibiting seizure symptoms?

A

Sodium may be corrected more aggressive - no more than 1-1.5 meq/L per hour for the first 3-4 hours
Still not exceeding 12 meq/L per day

104
Q

What is the result of correcting hyponatremia too rapidly?

A

Neurologic dysfunction

105
Q

What is treatment of hyponatremia directed at?

A

Decreasing total body water

106
Q

What are the steps to treating hyponatremia and decreasing total body water?

A
  • Calculate free water excess
  • Aimfor rate of correction
  • Determine period of time that correction should occur
  • Titrate IV lasix to achieve urine output equal to rate of free water removal
  • Replace urine output with isotonic saline
107
Q

How do you calculate free water excess?

A

TBW = .6 x wt in kg

Free water excess = TBW x (1 - Na concentration/140)

108
Q

What is the ideal rate of correction of hyponatremia?

A

.5 meq/hr rise in plasma sodium concentration

109
Q

How do you calculate the target rate of free water removal?

A

Free water excess/period of time calculated

110
Q

Which is more common, hypo or hypernatremia?

A

Hyponatremia, hypernatremia is not very common

111
Q

What is the major cause of hypernatremia?

A

Lack of free access to water

112
Q

What kinds of patients develop hypernatremia?

A

Infants
Institutionalized patients
Patients with neurological disorders
(these patients may lose ability to respond to thirst signals)

113
Q

What lab value is the best indicator for hypernatremia?

A

Volume loss leads to elevated BUN:Cr ratio

114
Q

What does an elevated BUN:Cr ratio indicate?

A

Dehydration or hypovolemia - can indicate hypernatremia

115
Q

What is the urine osmolality associated with hypernatremia?

A

High urine osmolality

116
Q

Why is urine osmolality high with hypernatremia?

A

Body puts out little urine and the urine is very concentrated

117
Q

What are the two types of diabetes insipidus?

A

Central and nephrogenic

118
Q

What is central diabetes insipidus?

A

Absence of ADH from the posterior pituitary

119
Q

What is nephrogenic diabetes insipidus?

A

Renal resistance to ADH

120
Q

What is central DI associated with?

A

Encephalopathy
Head trauma
Pituitary surgery
Tumor

121
Q

What is nephrogenic DI associated with?

A

Third trimester of pregnancy

122
Q

What clinical symptoms present with central DI?

A

Drink and urinate frequency because the body doesn’t hold onto fluid because of lack of ADH
Body is easily dehydrated

123
Q

What is the treatment of diabetes insipidus?

A

d-Desmoarginine vasopressin (dDAVP)

124
Q

What is dDAVP?

A

d-Desmoarginine vasopressin - synthetic ADH in a nasal spray

125
Q

What other conditions receive dDAVP as a treatment?

A

Bed wetting and von Willebrand’s disease

126
Q

How is renal resistance to ADH treated?

A

Problem corrects itself after delivery

127
Q

What is the character of the urine with diabetes insipidus?

A

Large volumes of extremely dilute urine with low sodium in the urine

128
Q

How do we diagnose diabetes insipidus?

A

Water deprivation - patients will still fail to concentrate their urine because they do not respond to ADH or have ADH

129
Q

What diagnosis would we give if the patient does not respond to dDAVP?

A

Nephrogenic DI

130
Q

What diagnosis would we give if the patient can concentrate their urine after giving dDAVP?

A

Central DI

131
Q

What can administration of hypertonic fluids cause?

A

Rarely causes hypernatremia

132
Q

When do we give patients hypertonic fluids?

A

Occasionally during resuscitation patients

133
Q

What is an example of hypertonic fluids used during surgery?

A

Ringer’s lactate

134
Q

What is ringer’s lactate?

A

Used in surgery due to the loss of blood, used instead of blood transfusions - patient needs to be transferred to normal saline in post op

135
Q

What happens to a patient’s volume status if they are administered hypertonic fluids?

A

Normal volume status but extremely high urine sodium excretion

136
Q

What serum osmolality indicates isotonic hyponatremia?

A

Normal 280-295

137
Q

What are two types of isotonic hyponatremia?

A

Hyperproteinemia

Hyperlipidemia

138
Q

What serum osmolality indicates hypertonic hyponatremia?

A

High above 295

139
Q

What are two types of hypertonic hyponatremia?

A

Hyperglycemia

Mannitol, sorbitol, glycerol, maltose

140
Q

What serum osmolality indicates hypotonic hyponatremia?

A

Low below 280

141
Q

What is the next step in the diagram after hypotonic hyponatremia?

A

Volume status - Hypovolemic, euvolemic, hypervolemic

142
Q

What type of hypovolemic hypotonic hyponatremia results from UNa of less than 10?

A

Extrarenal salt loss

143
Q

What type of hypovolemic hypotonic hyponatremia results from UNa of more than 10?

A

Renal salt loss

144
Q

What are the types of hypovolemic hypotonic hyponatremia from extra renal loss?

A

Dehydration
Diarrhea
Vomiting

145
Q

What are the types of hypovolemic hypotonic hyponatremia from renal loss?

A

Diuretics
ACE inhibitors
Nephropathies
Mineralocorticoid deficiency

146
Q

What are the types of euvolemic hypotonic hyponatremia?

A

SIADH
Postoperative hyponatremia
Hypothyroidism
Psychogenic polydipsia

147
Q

What are the types of hypervolemic hypotonic hyponatremia?

A 
Edematous states:
CHF
Liver disease
Nephrotic syndrome
Advanced renal failure

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