Fluid and Electrolyte Distubances

Question 1

Normal serum osmolality

Answer 1

280 -295 mOsm/kg

Question 2

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

Answer 2

> ~285 mOsm/kg

Question 3

Definition of hypovolemia

Answer 3

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

Question 4

Normal amount of insensible losses in healthy adults

Answer 4

500-650 ml/d

Question 5

Signs of hypovolemia

Answer 5

Decreased JVP
orthostatic tachycardia
orthostatic hypotension

severe:
hypotension
tachycardia
peripheral vasoconstriction
peripheral hypoperfusion

Question 6

Orthostatic tachycardia

Answer 6

an increase of >15-20 bpm upon standing

Question 7

Orthostatic hypotension

Answer 7

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

Question 8

Symptoms of hypovolemia

Answer 8

Fatigue
Weakness
Thirst
Postural dizziness

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

Question 9

Therapeutic goals in hypovolemia

Answer 9

restore normovolemia and replace ongoing fluid losses

Question 10

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

Answer 10

Isotonic normal saline (0.9% NaCl)

Question 11

Hyponatremia

Answer 11

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

Question 12

Diagnostic approach to hyponatremia

Answer 12

Question 13

Features suggestive of hypoaldosteronism

Answer 13

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

Question 14

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

Answer 14

Cerebral salt wasting

Question 15

Conditions that may present with cerebral salt wasting

Answer 15

Subarachnoid hemorrhage
Traumatic brain injury
Craniotomy
Encephalitis
Meningitis

Question 16

Most frequent cause of euvolemic hyponatremia

Answer 16

SIADH

Question 17

Causes of acute hyponatremia

Answer 17

Question 18

The time period that clinically defines chronic hyponatremia

Answer 18

> 48h

Question 19

Overly rapid correction of hyponatremia

Answer 19

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

Question 20

Presentation of ODS (Central pontine myelinolysis)

Answer 20

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

Question 21

Pseudohyponatremia

Answer 21

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

Question 22

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

Answer 22

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

Question 23

Cornerstone of the therapy of chronic hyponatremia

Answer 23

Water deprivation

Question 24

Urine-to- plasma electrolyte ratio

Answer 24

(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

Question 25

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

Answer 25

Demeclocycline

Question 26

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

Answer 26

AVP antagonists (vaptans)

Question 27

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

Answer 27

Oral tolvaptan

Question 28

Treatment of acute symptomatic hyponatremia

Answer 28

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

Question 29

Na deficit

Answer 29

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

Question 30

Rate of correction of chronic hyponatremia

Answer 30

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

Question 31

Given to patients with Na overcorrection

Answer 31

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

Question 32

Definition of hypernatremia

Answer 32

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

Question 33

Individuals with highest risk of developing hypernatremia

Answer 33

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

Question 34

Most common gastrointestinal cause of hypernatremia

Answer 34

diarrhea

Question 35

Gestational DI

Answer 35

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

Question 36

Treatment for gestational DI

Answer 36

Desmopressin acetate (DDAVP)

Question 37

Diagnostic approach to hypernatremia

Answer 37

Question 38

Management of hypernatremia

Answer 38

Question 39

Hypokalemia

Answer 39

defined as plasma K concentration of <3.5 mM

Question 40

Causes of hypokalemia

Answer 40

Question 41

Relationship between hypomagnesemia and hypokalemia

Answer 41

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

Question 42

Role of hypokalemia as a risk factor of digoxin toxicity

Answer 42

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

Question 43

ECG findings of hypokalemia

Answer 43

Broad flat T waves, ST depression, and QT prolongation

Question 44

Functional effects of hypokalemia on the kidney

Answer 44

NaCl and HCO3 retention Polyuria Phosphaturia Hypocitraturia Activation of renal ammoniagenesis

Question 45

The diagnostic approach to hypokalemia

Answer 45

Question 46

Goals of therapy in hypokalemia

Answer 46

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

Question 47

Mainstay of therapy in hypokalemia

Answer 47

Oral replacement of KCL

Question 48

Peripheral intravenous dose of potassium correction

Answer 48

20-40 mmol of KCL per liter

Question 49

Central vein intravenous dose of potassium correction

Answer 49

10-20 mmol/h

Question 50

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

Answer 50

20 mmol in 100 ml of saline solution

Question 51

Strategies to minimize K+ losses

Answer 51

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

Question 52

Definition of hyperkalemia

Answer 52

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

Question 53

Most frequent underlying cause of hyperkalemia

Answer 53

Decrease in renal K+ excretion

Question 54

Pseudohyperkalemia

Answer 54

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

Question 55

Causes of hyperkalemia

Answer 55

Question 56

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

Answer 56

Absence of P waves Marked QRS widening Abnormal QRS axis

Question 57

Classic ECG manifestations in hyperkalemia

Answer 57

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

Question 58

First priority in the management of hyperkalemia

Answer 58

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

Question 59

Diagnostic approach to hyperkalemia

Answer 59

Question 60

Three stages of the treatment of hyperkalemia

Answer 60

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

Question 61

Most effective and reliable methods to reduce plasma K+ concentration

Answer 61

Hemodialysis