BMP highlights Flashcards
1) List the tests in a BMP (know these)
2) What is the test that’s freq. included?
1) Sodium, potassium, chloride, bicarb(onate), BUN, creatinine, glucose
2) Calcium
Doubling of serum creatinine suggests ___% reduction in GFR
50%
Urea formed in the ___________ as a metabolic byproduct; BUN is excreted by the ____________.
liver; kidneys
Normal range of HCO3: _________ mEq/L
(know this)
22-26
Urine concentration of an electrolyte is helpful when compared to what?
serum levels
1) What is the gold-standard test to assess electrolytes with urine?
2) What is the more convenient test?
1) 24-hour urine collection to monitor electrolyte excretion
2) Fractional excretion (FE) of an electrolyte
Fractional excretion (FEx):
1) Low fractional excretion indicates ________
2) High fractional excretion indicates ________
1) retention
2) excretion
Osmolality of all solutes (electrolytes and others) in plasma is what?
280-295 mmol/kg
1) What is the normal serum range for sodium?
2) What is the normal serum range for potassium?
3) Are magnesium and phosphorus on BMP?
1) 135 – 145 mEq/L
2) 3.5 – 5.0 mEq/L
3) No; ordered separately
Sodium:
1) Is the main __________ cation
2) And the main determinant of extracellular __________ (affects fluid shifts)
1) extracellular
2) osmolality
1) _____________ is the most common electrolyte abnormality.
2) Is serum osmolality normally low, normal, or increased?
1) Hyponatremia
2) Usually low (hypotonic), sometimes normal or increased
1) Define severe (critical) hyponatremia
2) What is the normal sodium reference range?
3) Define severe (critical) hypernatremia
1) <125
2) 135-145 mEq/L* (important)
3) >160
Hyponatremia is usually due to an ________________________ diluting serum Na+, rather than a deficiency in total body Na+. (cells swell)
excess of total body water
What is the serum osmolality in hypernatremia; low, normal, or high?
Always high (unlike hyponatremia, which can be variable)(cells shrink)
Clinical manifestations and treatment of hypo/hypernatremia depend on what 2 things?
1) How far Na+ is outside of the normal range (severity)
2) Acuity of onset*
Differentiate between acute and chronic forms of hypo/hypernatremia (i.e. how long is each?)
Acute <48 hrs vs. chronic ≥48 hrs
(same concept applies to electrolyte disorders in general)
Acute and severe symptoms of hypernatremia may be seen with with Na+ >_____
> 160
What should the initial labs for hyponatremia include?
1) Serum and urine electrolytes
2) Serum and urine osmolality
What are the 3 initial labs for hypernatremia?
1) Serum sodium
2) Urine volume flow rate (oliguric or nonoliguric)
3) Urine osmolality
Hyponatremia: Serum osmolality ________ most of the time; urine osmolality usually _________
low; high
What are the 2 categories of hyponatremia? List causes of each
1) Pseudohyponatremia (normal serum osmolality)
Severe hypertriglyceridemia or hypergammaglobulinemia throws off sodium reading
2) Hypertonic (hyperosmolar) hyponatremia
Hyperglycemia and (less common) mannitol infusion
To calculate “corrected” sodium in hyperglycemia, increase sodium by _____ for every 100mg/dL rise in plasma glucose above normal (100 mg/dL)
1.6
What is the most common hyponatremia? How can you break that down further?
Hypotonic (hypo-osmolar) hyponatremia
What measurement defines “dilute urine”?
Urine osm <100
List 4 etiologies of Hypotonic ADH-Independent Hyponatremia
1) Primary (Psychogenic) polydipsia
2) “Beer potomania”
3) “Tea and toast diet”
4) Renal impairment
Patients with advanced renal impairment from AKI or CKD (GFR <_____) can cause hyponatremia
15
ADH-Independent Hypotonic Hyponatremia causes
1) “Excessive intake overwhelms ability of kidneys to excrete the water” describes what cause?
2) Insufficient dietary solute intake leads to inability to excrete water because of which cause?
3) When are the kidneys unable to adequately dilute urine (ADH is not the problem)?
1) Primary (Psychogenic) polydipsia
2) “Beer potomania” or “Tea and toast diet”
3) Renal impairment
_________________ causes are the most common category of hypotonic hyponatremias (urine osm >100, concentrated urine)
ADH dependent
1) ADH Dependent causes of hyponatremia involve what?
2) This is the appropriate response to what 2 things?
3) How are these causes categorized?
1) Failure to suppress ADH
2) Hypovolemia or reduced effective arterial volume
3) By pt volume status
ADH-Dependent Hypervolemic hypotonic hyponatremia etiologies:
1) Usually occurs in the setting of __________________ states (cirrhosis, heart failure, rarely nephrotic syndrome).
2) Decreased effective circulating volume triggers ADH activation; because of RAAS activation and increased aldosterone, is urine sodium low or high?
1) edematous
2) Low
ADH-Dependent Hypervolemic hypotonic hyponatremia etiologies: Give 3 examples of causes that reduce effective circulating volume
1) Cirrhosis
2) Heart failure (HF)
3) Nephrotic syndrome
Euvolemic hypotonic ADH-dependent hyponatremia: List 3 causes
1) SIADH
2) Reset osmostat
3) Adrenal insufficiency and severe hypothyroidism
1) Cortisol normally does what to ADH release?
2) What medications induce hyponatremia especially in older patients?
1) Inhibits it
2) Thiazide diuretics
Hyponatremia:
1) List 2 groups of meds that can lead to increased ADH
2) What recreational drug can lead to hyponatremia?
1) NSAIDs and SSRIs
2) MDMA (ecstasy)
Hyponatremia:
What two things should the lab consider? Why?
1) Serum and urine electrolytes (specifically Na+)
2) Serum and urine osmolality
-Urine osmolality is used as a surrogate for ADH activity
Factors affecting serum K+ concentration include what? (3)
1) Aldosterone
2) Sodium reabsorption
3) Acid-base balance
Hypokalemia:
1) What are the mild/mod clinical features?
2) Severe?
1) K+ 3.0-3.4
usually asymptomatic
2) K+ <2.5-3.0
Muscle weakness (including constipation from effects on GI smooth muscle), arrhythmias
Give an example of some features of a hypokalemia with an underlying cause
E.g. nephrogenic DI affects concentrating ability of urine: polyuria and polydipsia
Hypokalemia: Etiologies
1) How can insulin, beta-adrenergic agonists, alkalosis can cause hypokalemia?
2) What is at least one example of renal losses/ wasting causing hypokalemia?
1) Potassium shifted into cells
2) Loop diuretics
-Increased aldosterone
-Hypomagnesemia
Assessing urine potassium can help distinguish _________ from ___________ causes of hypokalemia
renal from non-renal
1) Assessing urine potassium can help distinguish renal from non-renal causes of what?
2) What is a convenient way to measure urine potassium?
3) What should be evaluated when a pt presents with low potassium?
1) Hypokalemia
2) Urine potassium to creatinine ratio (Uk/UCr)
3) Evaluate for acid-base disorders
1) Serious manifestations (usually K+ ≥7.0 mEq/L) of hyperkalemia include what?
2) What else may hyperkalemia cause?
1) Weakness or paralysis; cardiac conduction abnormalities and cardiac arrhythmias > lead to eventual cardiac arrest
2) Metabolic acidosis
Hyperkalemia etiologies include what? (4)
1) Increased K+ intake
2) Increased net K+ release from cells
3) Reduced urinary K+ excretion
4) Medications
Give some causes of increased net K+ release from cells
1) Pseudohyperkalemia
2) Tissue breakdown
3) Hyperglycemia
4) Metabolic acidosis
5) Others: Beta blockers, digitalis, exercise, etc
A combination of insulin deficiency and hyperglycemic hyperosmolarity can cause what?
Hyperglycemia and hyperkalemia
Hyperkalemia etiologies:
Give 4 examples of causes of impaired renal elimination of K+
1) AKI
2) CKD
3) Reduced aldosterone action
4) Low effective circulating volume
Drugs that induce Hyperkalemia:
1) List 3 drugs that reduce aldosterone release
2) Give an example of an aldosterone antagonist
3) What drug blocks sodium channels of principal cells? (Na+/K+ exchange via aldosterone)
4) How can beta-blockers induce hyperkalemia?
1) ACE-i, ARBs, and NSAIDs
2) Spironolactone
3) Triamterene
4) Block K+ uptake into cells
Ionized vs. Total Calcium:
1) Why is usually measuring total serum calcium sufficient?
2) What are exceptions? Why?
1) Bc changes in total mirror those in ionized fraction
2) exceptions where total calcium is low but ionized may be normal are:
Hypoalbuminemia, certain acid-base disorders:
-When serum albumin is <4 g/dL, serum Ca2+ is reduced by ~0.8 mg/dL* for every 1 g/dL of albumin below normal (4)
If __________ is low, total calcium is expected to be low; measure both when evaluating calcium
(______ is part of the CMP)
albumin (albumin is part of the CMP)
Calcium Homeostasis: Depends on _________ and ___________ (1,25-dihydroxyvitamin D), as well as negative feedback loops triggered by calcium
PTH and calcitriol
Calcium & Phosphorus are usually __________ related in the body
inversely
What is the hallmark of hypocalcemia?
important
Tetany
Chvostek sign + Trousseau sign are indicative of what?
Hypocalcemia
Hypocalcemia etiologies include what?
1) Hypoalbuminemia
2) Advanced CKD
3) Hypomagnesemia
4) Vitamin D deficiency
5) Primary hypoparathyroidism:
6) Alkalosis, diuretics, etc
1) What is the most common cause of decreased total serum Ca2+? (ionized Ca2+ may be normal)
2) What is the most common cause of true hypocalcemia?
1) Hypoalbuminemia
2) Advanced CKD
1) What do you need to do when a pt presents w hypocalcemia?
2) What is the most helpful lab to determine hypocalcemia etiology?
1) Confirm it is true hypocalcemia: e.g., low total serum calcium and low ionized calcium
2) PTH
Serum phosphate usually high in hypoparathyroidism or advanced CKD and low in vitamin D deficiency
Serum magnesium often low; may also measure vitamin D levels, renal function (creatinine
PTH is the most helpful in determining hypocalcemia etiology bc:
1) Serum ____________ usually high in hypoparathyroidism or advanced CKD, and low in vitamin D deficiency.
2) Serum ____________ often low; may also measure vitamin D levels, renal function (creatinine)
1) phosphate
2) magnesium
1) What are the PTH and phosphorus levels in hypoparathyroidism?
2) What are the PTH, phosphorus, and 25(OH)D levels in hypoparathyroidism?
1) PTH = low; phosphorus = high
2) PTH = low; phosphorus = high/ normal; 25(OH)D = low
1) What are the PTH, phosphorus, and creatinine levels in Chronic Kidney Disease?
2) What is the abnormal lab value in hypomagnesemia?
1) PTH: high, phosphorus: high, creatinine: high
2) Magnesium (low)
Hypercalcemia: Clinical Manifestations
May affect GI, kidney, and neurologic function
1) What presentation of hypercalcemia is usually primary hyperparathyroidism?
2) What presentation is usually malignancy-associated hypercalcemia?
1) Asymptomatic, mild hypercalcemia
2) Symptomatic, severe hypercalcemia
Hypercalcemia:
1) True or false: A pt would have elevated serum total and ionized calcium, and may have hypophosphatemia.
2) What are used to determine if hypercalcemia is PTH-mediated or not? Explain
1) True
2) Serum PTH levels:
High: primary hyperparathyroidism is the most likely cause
Low: eval for non-PTH-mediated cause (malignancy, Vit. D intoxication, etc.)
Both hypo- and hypermagnesemia can decrease PTH secretion/action and provoke ___________
hypocalcemia
GI losses (dietary, malabsorption) and urinary losses (diuretics, alcohol use) are common etiologies of what?
Hypomagnesemia
Arrhythmias (e.g., torsades de pointes) and neuromuscular and CNS hyperirritability (may be from low K+/Ca2+) may occur with low levels of what?
Magnesium (Hypomagnesemia)
Hypomagnesemia may cause hypo________ and hypo__________
hypokalemia and hypocalcemia
Decreased DTRs are the earliest clinical manifestation of what? What else may next?
Hypermagnesemia; respiratory muscle paralysis, cardiac arrest
Vitamin D deficiency and hyperparathyroidism are two etiologies of what?
Hypophosphatemia
1) Name 1 etiology of hyperphosphatemia
2) What can hyperphosphatemia cause?
1) CKD
2) Concurrent hypocalcemia
Osmotic demyelination syndrome can result from quickly reversing chronic ____________
hyponatremia
CKD, antacids, laxatives, and IV Mg (like for preeclampsia) may cause what?
Hypermagnesemia
