Disorders of Sodium Metabolism Flashcards Preview

Renal Block > Disorders of Sodium Metabolism > Flashcards

Flashcards in Disorders of Sodium Metabolism Deck (12):

1. Describe the differences between salt and water content in the body.

osmolality equilibrates between body compartments, sodium is restricted to the ECF and water moves to achieve equilibrium


2. Explain why the sodium ion determines the extracellular fluid volume.

Na+ stays in the ECF, so Na+ content of the ECF will either cause water to enter or exit this compartment and determine the ECF volume


3. Evaluate total body sodium content. What are the signs and symptoms of low sodium?

thirst (angiotensin II)
decreased BP
dry mouth
decreased urine output
dry axilla
low JVP
skin turgor reduced


4. Describe sodium transport in the nephron. List the sodium channels located in each section of the nephron.

PCT: Na/H antiporter
Ascending Limb: NKCC channel
DCT: Na/Cl cotransporter
Cortical duct: ENaC (epithelium sodium channel)


5. Explain how the body regulates the sodium balance.

volume status is the major mediator of sodium balance

sympathetic system: vasoconstriction , reducing the amount of Na filtered; activates RAAS thru B2 receptors

Renin Angiotensin System: angiotensin II causes vasoconstriction, aldosterone causes reabsorption of salt and reabsorption of water

ANP: vasodilation in response to atrial stretch, can cause increased salt delivery as well as act as a direct inhibitor to sodium reabsorption

pressure natriuresis- increased systemic pressure causes loss of sodium


Changes in salt content manifest as changes in _____ volume.

extracellular volume effected by changes in salt content


Define effective circulating volume.

effective circulating volume refers to part of the ECF that is in the arterial bed

essentially the pressure perfusing the arterial baroreceptors in the carotid sinus and glomerular afferent arterials that the body uses to monitor volume status


Describe why patients with CHF retain water using effective circulating volume.

diminished cardiac output leads to reduced effective circulating volume which causes the system to retain Na+ and water despite appropriate volume (can lead to edema)

note in cirrhosis ECF volume is increased but plasma volume is decreased due to low albumin


If you were measuring Na+ and Cl- to determine fluid status, would you test serum concentration or urine concentration?

urine sodium and chloride (modulated by aldosterone) tell you about volume status, unlike serum sodium, they are markers of effective circulating volume


Is sunken fontanelle a symptom of sodium gain or loss and why?

sodium gain- expansion of the ECF causes fluid to leave the ICF, causing shrinkage of brain


How do you treat volume depletion?

administer isotonic fluids to maintain appropriate intravascular volume then address osmolarity


How do you treat volume overload.

remove extra sodium either by decreasing sodium intake or increasing output