CVD & Electrolyte Imbalances Flashcards
Where in the body is ADH produced & secreted
produced by magnocellular neurons in the hypothalamus; secreted by the posterior pituitary gland
ADH drives sodium & water reabsorption along which parts of the nephron?
TAL & CD
Hypernatremia is clinically defined as what?
Serum Na concentration > 145 mmol/L
What are the 3 main causes of Hypernatremia?
Diabetes Insipidus; Inadequate bodily fluid volume; hyperglycemia
How does hyperglycemia cause hypernatremia?
at high concentrations, glucose can act as an osmotic diuretic and trap free water in the lumen to be excreted through urine
What is the mechanism of Dehydration-induced Hypernatremia?
Hyperosmotic plasma relative to the renal luman; hyperosmotic urine
How does nephrogenic diabetes insipidus affect urine osmolarity?
the urine osmolarity does not change and will stay the same even if the water deprivation progresses
What are secondary causes of hypernatremia?
orthostatic hypotension; pneumonia; tachycardia
What is the drug of choice to treat central diabetes insipidus?
desmopressin
What drugs are 1st line for management of nephrogenic DI?
Thiazides; amiloride
What diseases have strong correlation w/ nephrogenic DI?
amyloidosis; sarcoidosis; SLE; malignancy; PKD; V2-receptor defects
How is hyponatremia clincialy defined?
serum Na concentration < 135 mM
What recreational drug has been shown to cause acute hyponatremia?
MDMA (Ecstasy)
How is factitious hyponatremia clinically defined?
Plasma osmolarity > 295 mOsm/Kg
What causes factitious hyponatremia?
hyperglycemia & mannitol; dilution of serum Na via osmosis
If a pt. has normal plasma osmolality but is hyponatremia what causes would be at the top of your DDx?
hyperproteinemia; hyperlipidemia;l bladder irrigation; pseudohyponatremia b/c Na serum con. is being displaced by increased occupancy of lipids and proteins both of which do not contribute to plasma osmolality
How is true hyponatremia clinically defined?
plasma osmolality < 280 mOsm/kg
What is happening with Hypotonic Hypervolemic Hyponatremia?
volume overload causes ECF to be hypotonic relative to the ICF; therefore water is going to move from the ICS to the ECS causing edema
What are the main causes of hypotonic hypervolemic hyponatremia?
CHF (decreased renal perfusion from low CO), Cirrhosis (vasodilation), Nephrotic syndrome (hypoalbuminemia), renal insufficiency (impairment of free water excretion)
What can cause hypotonic hyponatremia when ECF volume is normal?
SIADH, hypothyroidism; adrenal insufficiency
What are the clinical hallmarks of adrenal insufficiency?
hypotension or normal BP; skin hyperpigmentation (elelvatd MSH stimulates melanin synthesis in epidermal melanocytes) hyperkalemia (almost always due to hypoaldosteronism)
How do diuretics affect volume of the ECF?
decreases ECF volume
How will Insensible Loss & diaphoresis affect ECF?
it will decrease ECF
Secretory Diarrhea is caused by what pathogen and how will it affect the ECF volume?
cholera; will decrees ECF volume
normal plasma osmolarity is clinically defined as what?
Plasma osmolality: 280-295 mOsm/kg
What causes Plasma osmolality to be high and hyponatremic?
serum sodium levels are being diluted via reabsorption of water through the nephrons
what causes plasma osmolality to be normal and hyponatremic?
when molecules that do not participate in osmosis are increased in serum causing pseudohyponatremia
what causes plasma osmolality to be low and hyponatremic?
polydipsia & polyuria
Increased plasma volume of a substance not contributing to plasma osmolality is assoc. w/ what type of hyponatremia; what are common causes?
pseudohyponatremia: plasma level is normal; causes: proteinemia, hyperlipidemia, & bladder irrigation
Increased thirst causing water intoxication which overwhelms the body’s capacity to excrete water; this is characteristic of which type of hyponatremia?
true hyponatremia caused by primary polydipsia and urine osmolality < 100 mM
Increased plasma osmolarity induced by a substance drawing water out of the cells is characteristic of what type of hyponatremia and what causes would be at the top of your DDx?
factitious hyponatremia; causes: hyperglycemia
What type of hyponatremia is assoc. w/ the following characteristics:
decreased oncotic pressure resulting in markedly increased vasodilation and decreased arterial blood volume
Hypotonic Hyponatremia assoc. w/ cirrhosis
What type of hyponatremia is assoc. w/ the following factors:
a primary defect in NaCl reabsorption int he medullary TAL
hypotonic hyponatremia induced by sodium wasting syndrome; Parameters: decreased ECF & urine osmolaity > 100 mmol/L & Urine Na > 20 mmol/L
Describe the mechanism of Cerebral Edema?
rapid decrease in plasma osmolality drives water into the surrounding tissues; this causes tissue volume overload and edema to occur
What structure in the brain is most affected by cerebral edema?
the pons
How is the brain going to respond to cerebral edema and why is this important to consider in clinical settings?
The body’s natural response is going to be to drive osmolytes out of the tissue and back into the plasma causing acute hypernatremia to occur; therefore if hyponatremia is corrected too fast w/ IV hypertonic saline, then this can lead to osmotic demyelination syndrome
What symptoms are associated w/ osmotic demyelination syndrome?
quadriparesis, diplopia, loss of consciousness
Mild-moderate hyponatremia is clinically defined how and what are common symptoms?
Mild: 130-135; Moderate: 121-129; HA nausea, fatigue
Severe hyponatremia is clinically defined how and assoc. w/ what symptoms?
<120 meq/L; seizures, coma, respiratory arrest
What is the appropriate treatment for mild and severe hyponatremia?
isotonic saline; do not correct Na > 10 meq/L in a 24 hr. period
what medications are appropriate for treating SIADH?
vasopressin receptor antagonists; furosemid; salt tablets
The world health organization recommends a daily potassium intake of how much?
3510 mg/day
what tissue in body stores the most potassium?
skeletal muscle
Hyperkalemia is clinically defined by what parameter?
> 5 mmol/L
What are the main causes of hyperkalemia?
rhabdomyolysis; hemolysis; burns; strenuous exercise; sepsis; hypertonicity; insulin deficiency; metabolic acidosis
What drugs can induce hyperkalemia?
digoxin; BBs; succinylcholine; arginine; K-sparing diuretics
What is the mechanism of strenuous exercise-induced hyperkalemia?
Constant Repetition of APs to maintain muscle contraction will cause excessive efflux of K
What cautions concerning strenuous exercise should you counsel a pts. with h/o CVD?
Right after exercise there will be a rapid drop in serum K to replenish K stores in skeletal muscle tissues which puts everyone with or without h/o CVD at increased risk for arrhythmias & cardiac arrest but more so for those w. h/o CVD
What are drugs that decrease K excretion?
ACE inhibitors; trimethoprim; NSAIDs; spironolactone; triamterene; pentamidine
what diseases are assoc. w/ hyperkalemia?
End stage AIDS, Diabetic nephropathies; Sickle cell disease, metabolic acidosis; cirrhosis
EKG should be considered for hyperkalemia if serum levels exceed what parameter?
K > 6 mEq/L
What types of arrhythmias are assoc. w/ hyperkalemia?
sinus bradycardia, sinus arrest; VTach & V. fib.; Asystole
What are different interventions that can be applied in severe cases of hyperkalemia?
intravenous Ca; Insulin and glucose; Inhaled Beta agonists; sodium bicarbonate (more appropriate for metabolic acidosis); hemodialysis
What affect does exogenous Ca have on the heart?
stabilizes myocyte membranes by slowing down conduction
What effects do insulin and beta agonists have on the heart?
displaces K from myocytes
What drugs are used to decrease to K serum?
Patiromer (Veltassa) bind K+ in GI lumen increasing its excretion; Sodium Zirconium cyclosilicate; Kayexalate (Na polystyrene sulfonate) exchanges plasma K for lumenial GI Na
What are some of the causes of Hypokalemia?
Type IV renal tubular acidosis; metabolic & respiratory alkalosis; licorice; Cushing Syndrome; hyperaldosteronism; thyrotoxicosis
How are extrarenal vs. renal induced hypokalemia discerned?
24 hr. Urine: <30 mmol (extrarenal); > 30 mmol (renal)
A urine K to creatinine ratio higher than 13meq/g indicates what?
renal potassium wasting
What does the transtubular potassium gradient assess?
values > 2 indicate renal loss; values < 6 indicate inappropriate renal response to hyperkalemia
Unlike TPP, FHPP typically presents at ages younger than 20 and what else?
not caused by hyperthyroidism; genetic autosomal dominant inheritance pattern
what drugs are typically first line for hypokalemia in pts. w/ comorbidities?
ACE inhibitors; ARBs; BBs; Potassium sparing diuretics
what is the most appropriate treatment for hypokalemia in non-urgent situations/
oral potassium 40 - 100 mmol/day
the majority of free ionized Ca is flittered through which part of the nephron?
PT; followed by TAL and then Distal nephron; 70;20;15
What specialized receptors on Parathyroid gland cells can sense changes in serum Ca levels?
CaSRs
How does PTH act on the GI to increase Ca reabsorption?
promotes synthesis of calcitriol (Vitamin D) which enhances Ca absorption
Of all the Ca in luminal GI, the vast majority of it is reabsorbed where along the GI tract and via which receptors ?
duodenum & jejunum; through TRPV6
How does PTH increase Ca reabsorption through the kidney?
increases distal nephron reabsorption of Ca through TRPV5 receptors
How does PTH work on bone to increase Serum levels of Ca?
increases osteoclast activity
How does Vitamin D increases Ca reabsorption through the nephron?
stimulates TRPV5 receptors in DCT & CD
Describe how the mechanism of Ca self regulation works.
Ca ions can directly influence renal Ca reabsorption via CasR in all segments of the nephron
Hypercalcemia induced by excess Ca intake is referred to as what?
Milk alkali syndrome
What is the mechanism for sarcoidosis induced hypercalcemia?
increased endogenous production of Vitamin D: hypervitaminosis D
what are the parameters for mild, moderate, & severe hypercalemia?
Mild: 11-11.5 mg/dL usually asymptomatic; Moderate: 12-14 mg/dL fatigue & muscle weakness; severe: > 14 mg/dL assoc. w/ neruopsych deficits, GI complications, & nephrolithiasis, shot QT syndrome, bradycardia
What is mechanism for familila hypocalciuric hypercalcemia?
autosomal dominat; inactivates CaSRs in parathyroid gland thus increases the Ca amount to respond to high Ca
What are appropriate treatments for mild to moderate cases of hypercalcemia?
calcitonin; bisphosphosphonates (inhibit Osteoclast mediated bone resorption); glucocorticoids: decreases synthesis of Vit. D.
What are the common clinical manifestations of hypocalcemia?
Tetany: trosseau’s sign (carpal spasm), Chvostek’s sign (facial nerve tap elicits contraction of ipsilateral facial muscles); seizures; papilledema
What are the main causes of Hypophosphatemia?
hyperparathyroidism; Vit. D deficiency; Rickest & osteomalacia asso. w/ renal phosphate wasting; fanconi syndrome; diarrhea, antacids; respiratory alkalosis; increased insulin secretion
What does a 24 urine collection indicate?
Ph secretion < 100 mg (intestinal dysfunction); >100 mg: reduced renal absorption
what are common causes of acute hyperphosphatemia?
tumor lysis syndrome; rhabdomyolysis
What is a unique clinical manifestation of hyperphosphatemia?
pulmonary & cardiac calcifications
How can hyperphosphatemia be treated?
Volume expansion will promote renal excretion; antacids will cause chelation limiting absorption in intestine; hemodialysis
what part of the nephron reabsorbs the majority of Mg?
TAL; this is the one exception in which the PT is not the main player
How does PTH affect magnesium serum levles?
it increases renal reabsorption
what can impair magnesium reabsorption?
hypercalcemia due to activation of CaSR which decreases Mg reabsorption
What are the main causes of intestine induced hypomagnesemia?
diarrhea; proton pump inhibitors; mutations to the renal and intestinal TRP receptors
What are genetic diseases that cause hypomagnesemia
Glitelman syndrome: mutation of NCC channels
Barter’s syndrome: mutataed channel varies w/ each phenotype
autosomal recessive renal hypomagnesemia w/ hypocalcemia: mutation of TRVP6 receptors in small intestine
what are drugs that can induce hypomanesemia?
loop & thiazide diuretics inhibit Mg reabsorption; Amphotericin B, aminoglycosides
What is commonly given for reversing torsades de pointe?
IV magnesium
If a pt’s K serum level is b/t 5.5 & 6.5 what would you expect to see on an EKG?`
peaked t-waves and QT interval shortening
If a pt’s K serum level is b/t 6.5 & 7.5 what would you expect to see on an EKG?`
first-degree AV block, QRS widening, PR interval prolongation
If a pt’s K serum level is >7.5 what would you expect to see on an EKG?`
Flattened or absent p-waves
