Disorders of Na and K Regulation Flashcards
Solute per 1 L of solvent
Osmolarity
Solute per 1 Kg of solvent
Osmolality
What is the normal serum osmolarity?
280-290
If the serum osmolarity is increased, what 2 systems will regulate it?
ADH
Thirst
What 2 receptor types can sense increased serum osmolarity and can activate ADH release?
- Hypothalamus osmoreceptors
2. Arterial baroreceptors
What is the normal serum value for sodium?
140
What is the normal serum range for potassium?
3.5 - 4.5
What is the normal serum range for chloride?
98 - 112
Hyponatremia
Na < 135
In what patients is Hyponatremia common and what does it result from?
Common in hospitalized patients
= Results from an INCREASE in total body water
Usually Hyponatremia is _____
Asymptomatic
If sodium levels drop below 125, what are some possible symptoms?
CNS - headache, dizzy, confusion, seizure, coma
When drawing labs, they should be drawn ______
Simultaneously
What are 2 steps to assessing Hyponatremia?
- Measure serum osmolarity
2. Measure urine Na+ and urine osmolarity
If the serum osmolarity is hypotonic hyponatremia, what should then be assessed?
Volume status
What is an example of a disease that can cause Hyponatremia and a malignancy associated?
SIADH
– Small Cell Lung Cancer can cause ectopic ADH release
What is the treatment for Hyponatremia?
Hypertonic Saline (3%)
What is a potential side effect if Hyponatremia is corrected TOO FAST?
Osmotic Demyelination Syndrome
– locked in syndrome and other CNS issues
Hypernatremia
Na+ > 145
Hypernatremia commonly occurs in what patients and is associated with what risk factors?
Infants and elderly
– Trauma, burns, dementia and uncontrolled diabetes
What 2 things can cause Hypernatremia and which is the most common?
- Dehydration – most common
2. Sodium overload
What are the main symptoms with Hypernatremia?
Neurologic
– Intracranial hemorrhage
What is the treatment for Hypernatremia?
Correct sodium and replace water loss
If Sodium levels are corrected too fast with Hypernatremia, what is there a risk for?
Cerebral edema
What organ primarily controls serum potassium?
Kidney
The immediate response to changes in K+ levels are controlled by?
Transcellular shift – Na/K ATPase
The long term control to changes in K+ is controlled by?
Renal K+ excretion in distal nephron
Hyperkalemia
K+ > 5
What are the main symptoms with Hyperkalemia?
Cardiac arrhythmias
Muscle weakness
Metabolic ACIDOSIS
What changes will be seen on ECG with Hyperkalemia?
Widened QRS
Peaked T wave
– membrane potential less negative
What 2 mechanisms usually cause Hyperkalemia?
- Transcellular shift
2. Decreased renal K+ excretion
What are some transcellular shift causes of Hyperkalemia?
Pseudohyperkalemia (RBC hemolysis)
Decreased insulin
Metabolic acidosis
What are some decreased renal K+ excretion causes of Hyperkalemia?
Decreased Aldosterone
Kidney injury
Hypokalemia
K+ < 3.5
What are the symptoms with Hypokalemia?
Cardiac arrhythmias
Muscle weakness
Metabolic ALKALOSIS
Rhabdomyolysis
What ECG change is seen with Hypokalemia?
U wave
– membrane potential is more negative
What are the general causes of Hypokalemia?
Transcellular shift
Extrarenal loss
Renal loss
What are some causes of a transcellular shift that causes Hypokalemia?
Insulin
Beta2 Agonist
Metabolic Alkalosis
What are some extrarenal causes of Hypokalemia?
GI loss - N/V, diarrhea and sweat
