Renal considerations of fluids and electrolytes Flashcards
Hypovolemia
Decrease in volume of blood plasma
○ Characterized by actual sodium depletion or excessive loss of
water
Possible etiologies of hypovolemia
○ 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)
Hypovolemia clinical features
● Extreme thirst
● Hypotensive
● Tachycardia
● Dizziness
● Nausea
● Cyanosis
Hypovolemia treatment
● 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
Hypervolemia
● Increase in volume of blood plasma
○ Characterized by an increase in total sodium which leads to increase in extracellular water
Possible etiologies of hypervolemia
○ 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
Hypervolemia clinical features
● Weight gain
● Edema: Lower extremities and
potentially upper
● Ascites
● Pulmonary Edema
● Nocturnal Dyspnea
● JVD
Hypervolemia Diagnostic findings
● 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
Hypervolemia treatment
● Treat the underlying cause
● Sodium and water restriction
● Loop Diuretics
● Nitroglycerine and morphine
● Vasodilators – Hydralazine
● Oxygen supplementation
● Hemodialysis
Hypokalemia
● 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…)
Etiologies of hypokalemia
○ Poor dietary intake
○ Excessive loss of body fluid
■ Generally these losses are from GI or Renal systems
Pathophysiology of Hypokalemia: GI loss
○ 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
Hypokalemia pathophysiology: Renal loss
○ 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
Hypokalemia clinical features
● Patients with mild hypokalemia are often asymptomatic
● Cardiovascular manifestations (most important to
recognize)
○ Hypotension
○ Palpitations and/or ventricular arrhythmias
○ Cardiac arrest
● Neuromuscular manifestations
What does Critically low Potassium (<2.5 mEq/L) cause?
○ Flaccid paralysis
○ Hypercapnia due to effect on respiratory muscles
○ Rhabdomyolysis
Decreased intracellular potassium levels can lead to muscle cell breakdown and _____
rhabdomyolysis (death of
muscle)
Over-excretion of potassium may be accompanied by
over excretion of Hydrogen ions, resulting in _____
metabolic alkalosis
Diagnostic Findings of hypokalemia (ECG findings)
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
Hypokalemia Management: Emergent vs. non-emergent
○ 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
Hyperkalemia
● 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
Severe hyperkalemia can result in ____
arrhythmias and death
Diagnostic Findings of hyperkalemia
● 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+)
EKG findings for hyperkalemia
● EKG (finding will vary depending on
the K+ level)
○ Peaked T-waves
○ Prolonged PR
○ Flattened P-wave
○ Prolonged QRS
○ ST depression
○ Sine wave
Hyperkalemia management
● 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
Management in patients with severe hyperkalemia
● IV Calcium Gluconate
● Nebulized Albuterol
● IV Glucose (D50W) with IV Insulin
IV Calcium Gluconate in treating severe hyperkalemia
○ Quick acting and can be life-saving
○ Doesn’t actually lower potassium, just stabilizes neural potentials to stabilize the cardiac membranes
Other Treatments for hyperkalemia
● Diuretics – Furosemide (Lasix)
● Potassium Binders/Exchange Resins – Sodium Polystyrene Sulfonate
● *IV Sodium Bicarbonate
● Dialysis
serum sodium concentration reflects disturbance in ____
water homeostasis
Osmolality
○ 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
Hyponatremia
● Defined as a serum sodium concentration of <135 mEq/L
○ Signs and symptoms may not occur until sodium is <125 mEq/L
Pathophysiology of hyponatremia
● 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
Clinical Features of hyponatremia
● 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
Diagnostic Findings of hyponatremia
● Serum sodium concentration <135 mEq/L
1. Check Serum Osmolality
2. Check Urine Osmolality
3. Check Urine Sodium Concentration
Serum osmolality in hyponatremia
● Helps to differentiate between isotonic, hypertonic, and hypotonic hyponatremia
○ Isotonic – between 280 and 295 mOsm/kg
○ Hypertonic – >295 mOsm/kg
○ Hypotonic – <280 mOsm/kg
Hyponatremia diagnostic findings
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
Hyponatremia management
● 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
Management of hypervolemic hyponatremia
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
Hyponatremia management of SIADH
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
For patients with a hypovolemic
hyponatremia, extracellular volume
should be replaced with_____
isotonic fluid
(0.9%)to restore sodium/water
balance
Management of severe symptomatic hyponatremia (neurological symptoms)
○ 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
Osmotic Demyelination Syndrome
● 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
Hypernatremia
● 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
Pathophysiology of hypernatremia
● 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)
Hypernatremia risk factors
○ Advanced age
○ Mental or physical impairment
○ Uncontrolled diabetes
○ Diuretic therapy
○ Hospitalization
○ Nursing home resident with
inadequate nursing care
Clinical Features of hypernatremia
● 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
Hypernatremia diagnostic findings
● 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)
Hypernatremia management
● 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)
Caution – Rapid water replacement can cause ______
cerebral edema!
