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PSBIM 2023 Nephro > Fluid and Electrolyte Distubances > Flashcards

Fluid and Electrolyte Distubances Flashcards

1
Q

Normal serum osmolality

A

280 -295 mOsm/kg

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2
Q

AVP secretion is stimulated as systemic osmolality increases above this threshold level

A

> ~285 mOsm/kg

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3
Q

Definition of hypovolemia

A

Hypovolemia generally refers to a state of combined salt and water loss, leading to contraction of the ECFV

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4
Q

Normal amount of insensible losses in healthy adults

A

500-650 ml/d

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5
Q

Signs of hypovolemia

A

Decreased JVP
orthostatic tachycardia
orthostatic hypotension

severe:
hypotension
tachycardia
peripheral vasoconstriction
peripheral hypoperfusion

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6
Q

Orthostatic tachycardia

A

an increase of >15-20 bpm upon standing

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7
Q

Orthostatic hypotension

A

a >10-20 mmHg drop in blood pressure on standing

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8
Q

Symptoms of hypovolemia

A

Fatigue
Weakness
Thirst
Postural dizziness

severe: oliguria, cyanosis, abd and chest pain, confusion or obtundation

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9
Q

Therapeutic goals in hypovolemia

A

restore normovolemia and replace ongoing fluid losses

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10
Q

The most appropriate resuscitation fluid for normonatremic or hyponatremic patients with severe hypovolemia

A

Isotonic normal saline (0.9% NaCl)

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11
Q

Hyponatremia

A

plasma Na+ concentration <135 mM

-almost always the result of an increased circulating AVP and/or increased renal sensitivity to AVP, combined with an intake of free water

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12
Q

Diagnostic approach to hyponatremia

A
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13
Q

Features suggestive of hypoaldosteronism

A

Hyperkalemia and hyponatremia in a hypotensive and or/hypovolemic patient with high urine Na concentration

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14
Q

A rare cause of hypovolemic hyponatremia, encompassing hyponatremia with clinical hypovolemia and inappropriate natriuresis in association with intracranial disease

A

Cerebral salt wasting

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15
Q

Conditions that may present with cerebral salt wasting

A

Subarachnoid hemorrhage
Traumatic brain injury
Craniotomy
Encephalitis
Meningitis

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16
Q

Most frequent cause of euvolemic hyponatremia

A

SIADH

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17
Q

Causes of acute hyponatremia

A
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18
Q

The time period that clinically defines chronic hyponatremia

A

> 48h

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19
Q

Overly rapid correction of hyponatremia

A

> 8-10 mM in 24h or 18 mM in 48h

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20
Q

Presentation of ODS (Central pontine myelinolysis)

A

Paraparesis or quadriparesis
Dysphagia
Dysarthria
Diplopia
“Locked-in syndrome’
Loss of consciousness

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21
Q

Pseudohyponatremia

A

defined as coexistence of hyponatremia with a normal or increased plasma tonicity

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22
Q

The ultimate “gold standard” for the diagnosis of hypovolemic hyponatremia

A

Demonstration that plasma Na+ concentration corrects after hydration with normal saline

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23
Q

Cornerstone of the therapy of chronic hyponatremia

A

Water deprivation

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24
Q

Urine-to- plasma electrolyte ratio

A

(Urinary Na + K)/ Plasma Na

a quick indicator of electrolyte-free water excretion

Ratio > 1 - should be aggresively restricted (<500 ml/d)
Ratio ~1 - should be restricted 500-700 ml/d

Ratio <1 should be restricted <1L/d

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25
Q

A potent inhibitor of principal ells and can be used in patients whose Na levels do not increase in response to furosemide and salt tablets

A

Demeclocycline

26
Q

Highly effective in SIAD and in hypervolemic hyponatremia due to heart failure or cirrhosis, reliably increasing plasma Na concentration due to their “aquaretic” effects

A

AVP antagonists (vaptans)

27
Q

Most appropriate for the management of significant and persistent SIAD that has not responded to water restriction and/or oral furosemide and salt tablets

A

Oral tolvaptan

28
Q

Treatment of acute symptomatic hyponatremia

A

Hypertonic saline 3% (512 mM) to acutely increase plasma Na concentration 1-2 mM/h to a total of 4-6 mM

29
Q

Na deficit

A

0.6 x BW x (target plasma Na concentration - starting plasma Na concentration)

30
Q

Rate of correction of chronic hyponatremia

A

<8-10 in the first 24h and <18 mM in the first 48 hours

31
Q

Given to patients with Na overcorrection

A

AVP agonist desmopressin acetate (DDAVP) and or administration of free water, typically IV D5W to prevent or reverse the development of ODS

32
Q

Definition of hypernatremia

A

an increase in the plasma Na concentration to >145 mM
-result of combined water and electrolyte deficit

33
Q

Individuals with highest risk of developing hypernatremia

A

Elderly individuals
-reduced thirst and/or diminished access to fluids

34
Q

Most common gastrointestinal cause of hypernatremia

A

diarrhea

35
Q

Gestational DI

A

a rare complication of late-term pregnancy wherein increased activity of a circulating placental protease with “vasopresssinase” activity leads to reduced circulating AVP and polyuria, often accompanied by hypernatremia

36
Q

Treatment for gestational DI

A

Desmopressin acetate (DDAVP)

37
Q

Diagnostic approach to hypernatremia

A
38
Q

Management of hypernatremia

A
39
Q

Hypokalemia

A

defined as plasma K concentration of <3.5 mM

40
Q

Causes of hypokalemia

A
41
Q

Relationship between hypomagnesemia and hypokalemia

A

Magnesium depletion:
-inhibitory effects on muscle Na+/ATPase activity
-secondary kaliuresis
-exagerrated K+ secretion by the distal nephron

**hypomagnesemic patients are clinically refractory to K+ replacement in the absence of Mg2+ repletion

42
Q

Role of hypokalemia as a risk factor of digoxin toxicity

A

Reduced competition between K+ and digoxin for shared binding sites on cardiac Na+/K+-ATPase subunits

43
Q

ECG findings of hypokalemia

A

Broad flat T waves, ST depression, and QT prolongation

44
Q

Functional effects of hypokalemia on the kidney

A

NaCl and HCO3 retention
Polyuria
Phosphaturia
Hypocitraturia
Activation of renal ammoniagenesis

45
Q

The diagnostic approach to hypokalemia

A
46
Q

Goals of therapy in hypokalemia

A

Prevent life-threatening and/or serious chronic consequences, to replace the associated K+ deficit, and to correct the underlying cause and/or mitigate future hypokalemia

47
Q

Mainstay of therapy in hypokalemia

A

Oral replacement of KCL

48
Q

Peripheral intravenous dose of potassium correction

A

20-40 mmol of KCL per liter

49
Q

Central vein intravenous dose of potassium correction

A

10-20 mmol/h

50
Q

Absolute amount of K+ that should be administered to prevent inadvertent infusion of a large dose

A

20 mmol in 100 ml of saline solution

51
Q

Strategies to minimize K+ losses

A

non-K+ sparing diuretics,
Restricting Na+ intake,
Using clinically appropriate combination of non-K+ sparing and K+ sparing medications

52
Q

Definition of hyperkalemia

A

defined as a plasma potassium level of 5.5 mM, occurring in up to 10% of hospitalized patients

53
Q

Most frequent underlying cause of hyperkalemia

A

Decrease in renal K+ excretion

54
Q

Pseudohyperkalemia

A

an artifactual increase in serum K due to the release of K+ during or after venipuncture

55
Q

Causes of hyperkalemia

A
56
Q

Difference of hyperkalemic brugada’ sign and genetic brugada’s syndrome

A

Absence of P waves
Marked QRS widening
Abnormal QRS axis

57
Q

Classic ECG manifestations in hyperkalemia

A

5.5-6.5 mM - tall peaked T waves

6.5-7.5 mM - loss of P waves

7.0-8.0 mM- widened QRS complex

> 8.0 mM - sine wave pattern

58
Q

First priority in the management of hyperkalemia

A

Assess the need for emergency treatment, followed by a comprehensive workup to determine the cause

59
Q

Diagnostic approach to hyperkalemia

A
60
Q

Three stages of the treatment of hyperkalemia

A
  1. Immediate antagonisms of the cardiac effects of hyperkalemia
  2. Rapid reduction in plasma K+ concentration by redistribution into cells
  3. Removal of potassium
61
Q

Most effective and reliable methods to reduce plasma K+ concentration

A

Hemodialysis

PSBIM 2023 Nephro (8 decks)

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