Fluid And Electrolyte Imbalance - Na, K Flashcards
(51 cards)
With increased Na+ intake, what changes occur in sympathetic activity, ANP, plasma oncotic pressure, and RAS to maintain normal electrolyte concentration within the body?
Decreased sympathetic activity (leads to dilation of afferent arterioles and thus increased GFR —> decreased Na reabsorption in PT)
Increased ANP (leads to constriction of efferent arterioles and thus increased GFR —> decreased Na reabsorption in CDs)
Decreased plasma oncotic pressure (leads to decreased Na reabsorption in PT)
Decreased RAS (leads to decreased Na reabsorption in PT and CDs)
Overall result is increased Na+ excretion! [note that opposite would occur with decreased Na+ intake]
Hypovolemia independently stimulates secretion of what hormone?
ADH —> water retention
Signs/symptoms of hypovolemia
Decreased skin turgor
Thirst
Dry mucous membranes
Sunken eyes
Oliguria
As it worsens, may see tachycardia, hypotension, tachypnea, and confusion
Signs/symptoms of hypervolemia
Weight gain
Edema
“bounding” pulse
Causes of absolute, extrarenal hypovolemia
Bleeding GI fluid loss Skin fluid loss Resp. fluid loss Extracorporeal ultrafiltration
Causes of absolute, renal causes of hypovolemia
Diuretics
Na+ wasting tubulopathies
Genetic or acquired tubulointerstitial dz
Obstructive uropathy/postobstructive diuresis
Hormone deficiency
Hypoaldosteronism/adrenal insufficiency
What does it mean to have relative hypovolemia?
Decreased effective circulating fluid volume with increased total body sodium
Extrarenal vs. renal causes of relative hypovolemia
Extrarenal: edematous states, heart failure, cirrhosis, anaphylaxis, drugs, sepsis, pregnancy, third-spacing
Renal: severe nephrotic syndrome
Causes of hypervolemia d/t primary renal sodium retention (increased ECV)
Oliguric acute renal failure Acute glomerulonephritis Severe chronic renal failure Nephritic/nephrotic syndrome Primary hyperaldosteronism Cushing syndrome Early stage liver disease Conn syndrome Gordon syndrome Liddle syndrome
Causes of hypervolemia d/t secondary renal sodium retention (decreased ECV)
Heart failure
Late stage liver disease
Nephrotic syndrome (minimal change disease)
Pregnancy
Hyper or hyponatremia are considered WATER problems. What is considered hyper vs. hyponatremic?
Hypernatremia = plasma [Na] > 145 mEq/L
Hyponatremia = plasma [Na] < 135 mEq/L
Most common electrolyte abnormality encountered in clinical practice
Hyponatremia
Hypervolemic etiologies of hyponatremia
With decreased ECV: CHF, cirrhosis, sepsis, nephrotic syndrome, pregnancy, anaphylaxis
With increased ECV: acute renal failure, advanced chronic renal failure
Euvolemic etiologies of hyponatremia
SIADH (vascular stretch receptors cause Na dumping to keep volume relatively normal)
Drugs Glucocorticoid deficiency Hypothyroidism Primary polydipsia Poor osmolar intake Positive pressure ventilation
Hypovolemic etiologies of hyponatremia
Renal losses (indicated by U[Na]>30): diuretic excess, mineralocorticoid deficiency, salt-losing nephropathy, bicarbonaturia with RTA and metabolic alkalosis, cerebral salt wasting
Extrarenal losses (indicated by U[Na]<30): vomiting, diarrhea, third-spacing d/t burns/pancreatitis/trauma
Mnemonic for hyponatremia symptoms
SALT LOSS
Stupor/coma
Anorexia, N/V
Lethargy
Tendon reflexes decreased
Limp muscles (weakness)
Orthostatic hypotension
Seizures/HA
Stomach cramping
Treatment of patients with hyponatremia is based on presenting symptoms.
How would you treat a patient with Level 1, aka no or minimal symptoms, possibly including HA, irritability, inability to concentrate, altered mood, depression, falls, or unstable gait?
Fluid restriction
Consider a -vaptan under select circumstances like: inability to tolerate fluid restrictions, very low sodium level, need for correction to have surgery, high fracture risk with unstable gait, etc.
Treatment of patients with hyponatremia is based on presenting symptoms.
How would you treat a patient with Level 2, aka moderate symptoms, possibly including nausea, confusion, disorientation, or altered mental status?
-vaptan or hypertonic NaCl infusion, followed by fluid restriction
Treatment of patients with hyponatremia is based on presenting symptoms.
How would you treat a patient with Level 3, or severe symptoms, possibly including vomiting, seizures, obtundation, respiratory distress, or coma?
Hypertonic NaCl, followed by fluid restriction or vaptan
Why must correction of hyponatremia be done slowly?
Overly rapid correction can cause Osmotic Demyelination Syndrome
- In acute symptomatic hyponatremia you can use a faster rate of infusion (2.5 mEq/L/h) to get to a safer zone, but do not increase more than 20 mEq/L/day
- If chronic, rate of increase should be ~0.5 mEq/L/h until 120 mEq/Na/L with total increase not to exceed 8-12 mEq/L/day and no more than 18 in the first 48 hrs
Hypervolemic causes of hypernatremia
Administration of hypertonic saline, hypertonic sodium bicarb
Hypertonic dialysis
Hypertonic feedings
Primary hyperaldosteronism
Cushing syndrome
Euvolemic causes of hypernatremia
Diabetes insipidus (central or nephrogenic) — again counterintuitive but note that vascular stretch receptors are keeping volume ~normal
Hypodipsia
Insensible dermal and skin losses (only if hypodipsic)
Hypovolemic causes of hypernatremia
Lack of access to water
“Broken” thirst mechanisms
Mnemonic for hypernatremia symptoms
TRIP
T - twitching, tremors, hyperreflexia
R - restlessness, irritable, confusion, etc. (d/t brain cell shrinkage)
I - intense thirst, dry mouth, decreased urine output
P - pulmonary and peripheral edema
