Renal considerations of fluids and electrolytes

Question 1

Hypovolemia

Answer 1

Decrease in volume of blood plasma
○ Characterized by actual sodium depletion or excessive loss of
water

Question 2

Possible etiologies of hypovolemia

Answer 2

○ Loss of blood (external/internal bleeding)
○ Loss of plasma (severe burns and leaky lesions “third spacing”)
○ Loss of body sodium and intravascular fluid (diarrhea/vomiting)

Question 3

Hypovolemia clinical features

Answer 3

● Extreme thirst
● Hypotensive
● Tachycardia
● Dizziness
● Nausea
● Cyanosis

Question 4

Hypovolemia treatment

Answer 4

● Oxygen: Increase efficiency/oxygenation of the remaining blood supply
● IV fluids: Inotropic therapy (if in shock) – dopamine, epinephrine
○ Increase contractility of heart
● Replenish blood loss: Fresh frozen plasma or whole blood

Question 5

Hypervolemia

Answer 5

● Increase in volume of blood plasma
○ Characterized by an increase in total sodium which leads to increase in extracellular water

Question 6

Possible etiologies of hypervolemia

Answer 6

○ Inability to regulate sodium
■ CHF, acute renal failure, liver failure
○ Exogenous sodium
■ IV solutions, medications such as Mannitol (osmotic diuretic)
○ Fluid mobilization after burn injury

Question 7

Hypervolemia clinical features

Answer 7

● Weight gain
● Edema: Lower extremities and
potentially upper
● Ascites
● Pulmonary Edema
● Nocturnal Dyspnea
● JVD

Question 8

Hypervolemia Diagnostic findings

Answer 8

● Hypoxia
● CXR: Possible pulmonary congestion
● CBC: Hematocrit levels may be falsely
low due to dilution
● CMP: Low sodium, BUN, potassium
due to dilution
● Urine osmolality is lowered

Question 9

Hypervolemia treatment

Answer 9

● Treat the underlying cause
● Sodium and water restriction
● Loop Diuretics
● Nitroglycerine and morphine
● Vasodilators – Hydralazine
● Oxygen supplementation
● Hemodialysis

Question 10

Hypokalemia

Answer 10

● Defined as a serum potassium concentration of <3.5 mEq/L
○ Severe hypokalemia = <2.5 mEq/L
Hypokalemia: Practice Essentials, Pathophysiology, Etiology. (2020).
● Actually represents low level of body potassium
(quantitative), unlike decreased serum sodium level
(more to come on that…)

Question 11

Etiologies of hypokalemia

Answer 11

○ Poor dietary intake
○ Excessive loss of body fluid
■ Generally these losses are from GI or Renal systems

Question 12

Pathophysiology of Hypokalemia: GI loss

Answer 12

○ Vomiting and nasogastric suctioning
○ Diarrhea or laxative use, large direct
amounts of potassium are lost
○ Volume depletion and metabolic alkalosis
■ Increase the rate of potassium loss by
renal potassium excretion

Question 13

Hypokalemia pathophysiology: Renal loss

Answer 13

○ Diuretic treatment: Side effect of potassium loss
○ Renal tubular or interstitial disease: Both involved with potassium and water
reabsorption
○ Hyperaldosteronism: Increases K+
secretion in the collecting tubules → increase K+ excretion

Question 14

Hypokalemia clinical features

Answer 14

● Patients with mild hypokalemia are often asymptomatic
● Cardiovascular manifestations (most important to
recognize)
○ Hypotension
○ Palpitations and/or ventricular arrhythmias
○ Cardiac arrest
● Neuromuscular manifestations

Question 15

What does Critically low Potassium (<2.5 mEq/L) cause?

Answer 15

○ Flaccid paralysis
○ Hypercapnia due to effect on respiratory muscles
○ Rhabdomyolysis

Question 16

Decreased intracellular potassium levels can lead to muscle cell breakdown and _____

Answer 16

rhabdomyolysis (death of
muscle)

Question 17

Over-excretion of potassium may be accompanied by
over excretion of Hydrogen ions, resulting in _____

Answer 17

metabolic alkalosis

Question 18

Diagnostic Findings of hypokalemia (ECG findings)

Answer 18

Serum potassium level <3.5 mEq/L
○ ECG may possibly reveal
■ Flattened or inverted T waves
■ Prominent U waves (cause unknown)
■ ST depression
■ Premature ventricular contractions

Question 19

Hypokalemia Management: Emergent vs. non-emergent

Answer 19

○ Non-emergent
■ Oral Potassium therapy (Potassium Chloride (KCl))
■ In mild cases may postpone need of K+ replacement (i.e.
antiemetics)

○ Emergent – K+ <2.5 or presence of cardiac arrhythmias
■ Treat with IV Potassium Chloride

● Treating the underlying cause of the hypokalemia

Question 20

Hyperkalemia

Answer 20

● Defined as a serum potassium concentration of >5 mEq/L
● Several disease states can lead to cellular redistribution of K+ from the intracellular to extracellular compartment

Question 21

Severe hyperkalemia can result in ____

Answer 21

arrhythmias and death

Question 22

Diagnostic Findings of hyperkalemia

Answer 22

● Serum potassium level is >5.0 mEq/L
● If secondary to renal dysfunction
○ Elevated BUN and Creatinine
○ Fraction of excreted potassium will be low
● ABGs → reveal metabolic acidosis (retaining hydrogen with the K+)

Question 23

EKG findings for hyperkalemia

Answer 23

● EKG (finding will vary depending on
the K+ level)
○ Peaked T-waves
○ Prolonged PR
○ Flattened P-wave
○ Prolonged QRS
○ ST depression
○ Sine wave

Question 24

Hyperkalemia management

Answer 24

● Treatment depends potassium level and the evidence of cardiac toxicity
● Unless characteristic EKG findings are present, always confirm hyperkalemia by repeating the lab STAT
○ Potentially life-threatening hyperkalemia should be treated immediately, and then look for the cause

Question 25

Management in patients with severe hyperkalemia

Answer 25

● IV Calcium Gluconate
● Nebulized Albuterol
● IV Glucose (D50W) with IV Insulin

Question 26

IV Calcium Gluconate in treating severe hyperkalemia

Answer 26

○ Quick acting and can be life-saving
○ Doesn’t actually lower potassium, just stabilizes neural potentials to stabilize the cardiac membranes

Question 27

Other Treatments for hyperkalemia

Answer 27

● Diuretics – Furosemide (Lasix)
● Potassium Binders/Exchange Resins – Sodium Polystyrene Sulfonate
● *IV Sodium Bicarbonate
● Dialysis

Question 28

serum sodium concentration reflects disturbance in ____

Answer 28

water homeostasis

Question 29

Osmolality

Answer 29

○ Osmolality is a measure of the amount of all solutes that have been
dissolved in a solvent
○ e.g., how much Na+, K+, Glucose, Ca++, etc., (solutes) have dissolved in urine or plasma (solvent) Expressed as – mOsm/kg

Question 30

Hyponatremia

Answer 30

● Defined as a serum sodium concentration of <135 mEq/L
○ Signs and symptoms may not occur until sodium is <125 mEq/L

Question 31

Pathophysiology of hyponatremia

Answer 31

● If the serum sodium concentration is low, this should be interpreted as “too much water on board”
● The differential diagnosis is broad, but includes
○ Hypertonic fluid shift (hyperglycemia, mannitol therapy)
○ SIADH – causes excessive water retention and dilutional hyponatremia
○ Acute renal failure
○ CKD – affects ability to regulate water excretion
○ Diuretic therapy – not only can cause Potassium loss but also Sodium
○ Cerebral salt wasting – rare; renal sodium transport issue seen in
intracranial disorders

Question 32

Clinical Features of hyponatremia

Answer 32

● The signs and symptoms of hyponatremia depend on severity of
hyponatremia
● Signs and symptoms
○ Nausea with or without vomiting
○ Malaise and/or headache
○ Decreased level of consciousness
■ Cerebral edema/water driven into brain cells
○ Seizures
○ Coma

Question 33

Diagnostic Findings of hyponatremia

Answer 33

● Serum sodium concentration <135 mEq/L
1. Check Serum Osmolality
2. Check Urine Osmolality
3. Check Urine Sodium Concentration

Question 34

Serum osmolality in hyponatremia

Answer 34

● Helps to differentiate between isotonic, hypertonic, and hypotonic hyponatremia
○ Isotonic – between 280 and 295 mOsm/kg
○ Hypertonic – >295 mOsm/kg
○ Hypotonic – <280 mOsm/kg

Question 35

Hyponatremia diagnostic findings

Answer 35

Urine Osmolality: >100 mOsm/kg, suggests that the kidneys are lacking the ability
to dilute the urine (not diuresing)

Urine sodium concentration
● Decreased in conditions such as CHF, Cirrhosis, and non-renal water loss (vomiting, diarrhea, burns, third-spacing)
● Increased in conditions such as renal failure, diuretics, SIADH, adrenal insufficiency, and severe hypothyroidism

Question 36

Hyponatremia management

Answer 36

● Treat the underlying cause
● Treat in the ICU if sodium is < 125 mEq/L, or if the patient has symptoms
● Consultation with a Nephrologist
● Treatment is complex and depends on the volume status, as well
as severity and cause of the hyponatremia

Question 37

Management of hypervolemic hyponatremia

Answer 37

In the case of hypervolemic hyponatremia (such
as CHF, Cirrhosis, or Nephrotic syndrome…)
○ Underlying cause should be the focus of
treatment
○ Fluid restriction of no more than 1-1.5 L/day
○ Salt restriction
○ Loop diuretics used to offload excess fluid

Question 38

Hyponatremia management of SIADH

Answer 38

SIADH (Syndrome of inappropriate ADH) is one of the most common causes of hyponatremia (normovolemic/euvolemic hypotonic hyponatremia)
○ First line treatment is free water restriction
– No more than 1-1.5 L of free fluid intake
per day (from all sources - IV, PO)
○ Second line treatment is loops, urea, PO
sodium tabs

Question 39

For patients with a hypovolemic
hyponatremia, extracellular volume
should be replaced with_____

Answer 39

isotonic fluid
(0.9%)to restore sodium/water
balance

Question 40

Management of severe symptomatic hyponatremia (neurological symptoms)

Answer 40

○ Prompt IV Hypertonic Saline (3% NaCl) until sodium of 125 mEq/L
○ Can be dangerous and should be done in the ICU
○ If hyponatremia is corrected too quickly, more than 4-8 mEq/L per
day, it can cause Osmotic Demyelination Syndrome

Question 41

Osmotic Demyelination Syndrome

Answer 41

● Develops 2-6 days after rapid elevation in sodium
● Slurred speech, tremors, weakness, balance problems, dysphagia, behavioral
disturbances, lethargy, confusion, disorientation, and coma
● Often irreversible or only partially reversible

Question 42

Hypernatremia

Answer 42

● Serum Sodium concentration >145 mEq/L
● It is strictly defined as a hyperosmolar condition caused by a decrease in
total body water relative to sodium content
○ Hypernatremia is a water problem, not a problem with sodium
balance

Question 43

Pathophysiology of hypernatremia

Answer 43

● During hypernatremia, the extracellular fluid is hyperosmolar
● Water is pulled out of the cytoplasm (ICF) into the plasma (ECF) via
osmosis, Causing neuronal cell shrinkage
● Decrease in ECF can also lead to circulatory problems, such Tachycardia and hypotension
● Mortality rates of 30-48% with a serum sodium >150 mEq/L (mmol/L)

Question 44

Hypernatremia risk factors

Answer 44

○ Advanced age
○ Mental or physical impairment
○ Uncontrolled diabetes
○ Diuretic therapy
○ Hospitalization
○ Nursing home resident with
inadequate nursing care

Question 45

Clinical Features of hypernatremia

Answer 45

● Decreased level of consciousness
● Restlessness/irritability
● Convulsions/coma
● Tachycardia and hypotension
● Oliguria or anuria
● Dry mouth and dry mucous
membranes
● Lack of tears and decreased
saliva production

Question 46

Hypernatremia diagnostic findings

Answer 46

● Serum sodium >145 mEq/L
● Serum osmolality is always >290 mOsm/kg
○ Definition of hyperosmolar state
● Urine sodium concentration may be elevated or decreased depending
on the cause (more in 2 slides)

Question 47

Hypernatremia management

Answer 47

● Identify and treat the underlying condition
● Symptomatic hypernatremia should be treated inpatient → the ICU
● Hypovolemic hypernatremia
○ Initially with normal saline, then with hypotonic solutions
● Euvolemic hypernatremia
○ Fluid replacement
○ Central DI may require DDAVP (vasopressin or desmopressin)

Question 48

Caution – Rapid water replacement can cause ______

Answer 48

cerebral edema!