Lab Med - Electrolytes Flashcards
BMP vs. CMP
- about same cost
- CMP is BMP + extras
- unless looking for something specific like K+, might as well order CMP
- BMP is Chem 7
- CMP is chem 19 or 24
What is included on BMP
- glucose
- BUN
- Cr
- BUN/CR ratio
- serum Na+
- serum K+
- serum Cl-
- CO2
- calculated osmolality
CO2 on BMP
- reflection of bicarb in blood
- venous measurement so not as accurate as ABG
- ABG is a better way to measure for acid base balance
Osmolality
- NL value (ish)
- what is it most helpful in determining
- 300 mOsm/kg or so
- helpful in determining hydration status
What is on CMP
- all on BMP plus:
- liver function
- pancreatic function
- Calcium
- albumin
*not Mg, separate test
Renin-angiotensin-aldosterone system
KNOW (but we know this, right??)
What is important to remember about ACEI/ARB
- all effect renin-angiotensin -aldosterone system
- particularly elevate K+
- must monitor K+ when pts take these meds
- if already high end of normal K+, do not use these meds, if do, increases K+ even further…
What lab tube is serum Na+ tested in?
marbled
Na+
- normal range
- panic ranges
NL: 135-145 meq/L
panic:
<125 meq/L
>155 meq/L
Na+ impact physiologically
neuromuscular function
What is the first question you should ask when dealing with hypo- or hypernatremia?
what is the volume status of the patient?
Hypervolemia sx
- edema
- rales
- ascites
- pleural effusion
- SOB
- CHF
- cirrhosis
- nephrosis
- decreased urine/serum osmolality
*wet
Hypovolemia sx
- dry mucous membranes
- dec. urine output
- absense tears
- delayed cap refill
- hypotension
- orthostatic hypotension
- tachycardia
- diuretic use
- excessive sweating
- v/d
Euvolemia sx
none of the sx of hypo- or hypernatremia
what volume status is related to hyponatremia
- example of condition this occurs in
- hyponatremia: hypervolemia (dilution issue)
- seen in SIADH - too much ADH, don’t pee, become edematous and hyponatremic
what volume status is related to hypernatremia
- 2 examples of when this occurs
- hypernatremia: hypovolemia (too little volume, concentrated sodium)
- diabetes insipidus: pee everything out
- too much Lasix, summer in OKC = dehydration
Value of:
- hyponatremia
- hypernatremia
<130 mEq/L
>150 mEq/L
What are the SS of
- hyponatremia
- hypernatremia
they are the same!
- lethargy, confusion, coma
- muscle twitches, seizures, tetany
- nausea, vom, Ileums (hypo)
- pulm/peripheral edema (hyper)
Hyponatremia
- what is MC cause
dilution issue (too much volume)
How to treat hyponatremia dt dilution issue?
- restrict fluids based on determination of
- ex: cut down calculated maintenance IV fluid by half for 24 hours and watch sodium (should rebound)
Hypernatremia
- two causes
- volume depletion (will have orthostatic hypotension)
- can also be euvolemic
Treatment of volume depletion related hypernatremia
- rehydrate with 0.9% physiologic saline until volume is restored
(if euvolemic tx with free water)
Potassium
- normal range
- panic range
NL: 3.5-5.0
Panic:
<3
>6
Potassium
- physiologic effects when out of range
- how regulated
- profound effect on neuromuscular and cardiac function (very important to keep in NL range)
- regulated by renal excretion
What is important to avoid when doing blood draw for Potassium
hemolysis
- will dump intracellular K+ into plasma, effect lab results
Hyperkalemia caused by:
- hemolysis, tissue damage, rhabdomyolysis
- acidosis
- renal failure
- ACEI
- BB
Others in slide but these are the ones Dr. McNeill said out loud
Hypokalemia cause by:
- low K+ intake (on Lasix for CHF, need K+ supplement to make up for what pee out)
- Diuretics
Two K+ sparing diuretics
- Spironolactone and triamterene
spironolactone used to treat:
- acne (back acne) bc blocks testosterone which causes acne. works better in women
- PCOS
- premenstrual dysforic disorder
- ascites (liver failure
Renal Tubular acidosis Type 1
- location
- acidemia?
- potassium status
- collecting tubules
- severe acidemia
- hypokalemia
Renal Tubular acidosis Type 2
- location
- acidemia?
- potassium status
- proximal tubule
- yes acidemia
- hypokalemia
Renal Tubular acidosis Type 4
- location
- acidemia?
- potassium status
- pathophys major organ
- Adrenal glands
- +/- mild acidemia
- hyperkalemia
Hypokalemia
- can cause (2)
- EKG changes
- neuromuscular and heart issues and ileus
- depressed T wave and presence of U waves
Hyperkalemia
- can cause (1)
- EKG change
- neuromuscular and heart issues
- peaked T waves in all leads
What is the basal body requirement for K+ per day
1-2 mEq/kg/day OR
about 60-80 mEq/day
Hypokalemia tx
- give potassium!
- IV with normal physiologic saline and add KCl to saline OR
- oral KCl
- go slow: good idea to correct first half of disturbance in first 8 hours, the other half in the remaining 16 hours
in general, how should the treatment of electrolyte disturbances proceed
SLOWLY, don’t want to overdo it and push them into converse hypo/hyper state
If have EKG changes due to K+ imbalance, what sort of Tx is needed?
IV
If do NOT have EKG changes due to K+ imbalance, what sort of tx is needed
can correct more slowly with KCl tablets vs. IV
Hyperkalemia effects at
- 7-8 mEq/L
- 10 mEq/L
- v. fib in 5% of people
- almost all people in v. fib
Hyperkalemia rapid tx
- protect myocardium: flood system with CaCl
- alkalize the blood with sodium bicarbonate- shifts K+ into cell
- Ampule of dextrose 50g followed by insulin bolus (10U) or regular fast acting insulin, insulin will shift K into cell
- Albuterol inhaler: sympathomimetic, shifts K+ into cell
*peaked t waves corrected quickly
Hyperkalemia slow tx
- polystyrene - drink or enema, binds K+ in GI and prevents its absorption
- 20-40 mg Lasix via IV, have them pee out the K+
Calcium
- normal range
- panic range
- NL: 8.5 - 10.5 mg/dL
- panic:
< 6.5 mg/dL
> 13.5 mg/dL
what causes about 60% of hypercalcemia?
parathyroid adenoma (benign)
What causes about 35% of hypercalcemia?
PTH-like secreting tumors
- breast, renal cell, prostate, lung cancers
- product PTH-RP (related protein)
- increases serum Ca+
Causes of hypercalcemia other than parathyroid adenoma (MC)
- intake of too much milk (or vitamin D)
- Paget’s dz: overactive digestion and laying down of bone in an abnormal pattern. Release of lots of bone Ca+
- Antacids (calcium carbonate): over consumption
- Lithium (bipolar tx)
- PTH-like secreting tumors
Causes of hypocalcemia
- hypoparathyroidism
- vitamin D deficiency
- renal insufficiency
- hypoalbuminemia
What must you also know to properly interpret Ca+ serum levels?
albumin
for every decrease in albumin by 1 mg/dL, must increase Ca by 0.8 mg/dL.
*if albumin decreased from 4 to 1: (3)(0.8) = 2.4 + calcium level on lab = adjusted calcium level
what three things regulate serum Ca
PTH
calcitriol
phosphorus
** there is a good picture of the system in the slides
where is calcitriol synthesized?
PCT
why hypocalcemia during renal failure?
Vitamin D is processed in the kidneys, need vitamin D to absorb Ca
Calcium effects on EKG
- Hypercalcemia: shortens ST and QT
- hypocalcemia: prolonged ST and QT
Hypocalcemia symptoms
- all related to tetany
- Chvostek’s sign (facial nerve twitch when rub)
- Trousseau’s sign (Bp cuff on arm = fingers spasm)
Hypocalcemia treatment
- add calcium
- if IV (acute) tx, need ICU care
- if can tx more slowly, oral tx is fine
Hypercalcemia
Stones (renal, biliary) Bones (bone pain) Groans (abd pain, n/v) Thrones (polyuria -> dehydration) psychiatric overtones (depression, cog dysfunction, insomnia, coma)
Hypercalcemia treatment
- saline diuresis: load up with normal saline IV and Lasix - will pee the calcium right out
- same as other electrolytes, slowly adjust to avoid hypocalcemia
Hypercalcemia causes
- need to investigate cause… not a dilution matter like Na+
- start with PTH
In hypercalcemia, what is expected PTH level
- low dt negative feedback
Hypercalcemia with high PTH
- primary hyperparathyroidism (60% of hypercalcemia)
- PTH-rP from a tumor
hypercalcemia with low PTH
- next step is bone survey/scan
- if not a malignancy, then check serum vitamin D
- Dr. McNeill did not go over the list specifically but there are multiple causes on the chart in the slides
hypercalcemia caused by primary hyperparathyroidism - what are the two main causes
- benign adenoma
- hyperplasia
What four types of cancer often cause PTHrP production
- breast
- lung (squamous cell)
- renal
- prostate
** native PTH will be low or zero in these cases
Chloride
- range
98-107 mEq/L
What electrolyte issue is almost always seen with Cl issue?
Na bc NaCl is commonly how Cl is in body
- treat the Na not the Cl
role of Cl
- principle anion of ECF
- maintaining normal acid-base balance and osmolality
causes of hyperchloridemia
- renal failure
- nephrotic syndrome
- overtx with saline
- hyperparathyroidism
- diabetes insipidus
- diarrhea = metabolic acidosis
- respiratory alkalosis
** same that causes hypernatremia
cause of hypochloridemia
- vomiting (will NOT cause hyponatremia bc vomit HCl, no Na)
- diarrhea
- GI suction
- renal failure with salt deprivation
- diuretics
- chronic resp. acidosis
- diabetic ketoacidosis
- excessive sweating
- SIADH
many more
Anion gap equation
= Na - (Cl- + HCO3-)
normal range 8-12 mmol/L
Acidosis with normal anion gap - two types
- diarrhea (MC)
- Renal tubular acidosis
Acidosis with increased anion gap - two types list
- exogenous
- endogenous
exogenous causes of acidosis with increased anion gap
- poisons like salicylate (ASA), old antifreeze
- alcoholic ketoacidosis
endogenous causes of acidosis with increased anion gap
- DM ketoacidosis
- uremia (elevated BUN)
how to workup acidosis
- ABG to determine if respiratory or not
- then figure out anion gap
Alkalosis two types
- chloride responsive
- chloride resistant
Chloride responsive alkalosis
- causes
- tx
- vomiting, NG suction
- tx: replace Cl, easy :)
Chloride resistant alkalosis
- causes
- tx
- endocrine disorders: Conn’s syndrome (hyperaldosteroneism), Barter’s syndrome, Cushings
- tx: can’t just add Cl, have to fix the endocrine disorder
Respiratory acidosis
- acute primary change
- arterial pH (ABG)
- K+
- anion gap
- sx
- pCO2 retention
- decrease in pH
- hyperkalemia
- normal anion gap
- dyspnea, rales, wheeze, respiratory outflow obstruction, etc.
Respiratory alkalosis
- acute primary change
- arterial pH (ABG)
- K+
- anion gap
- sx
- pCO2 depletion
- increase in pH
- hypokalemia
- normal or decreased anion gap
- anxiety, breathlessness, Chvostek, Trousseau
Metabolic acidosis
- acute primary change
- arterial pH (ABG)
- K+
- anion gap
- sx
- HCO3- depletion
- decrease in pH
- hyper or hypokalemia
- normal or increased anion gap
- weakness, air hunger, Kussmaul, dry skin and mucous membranes, etc.
Metabolic alkalosis
- acute primary change
- arterial pH (ABG)
- K+
- anion gap
- sx
- HCO3- retention
- increase in pH
- hypokalemia
- normal anion gap
- weakness, Chvostek, Trousseau
Three types of abnormal respiration to know for this exam
- Biot’s
- Kussmaul
- Cheyne-Stokes
Biot’s respiration
- describe
- cause
- breath normally, blood well oxygenated
- apnea
- rapid breathing to re-oxgygenate
- repeat
- neurological damage (stroke)
Kussmaul respiration
- describe
- cause
- slow, deep breathing
- metabolic acidosis
- diabetic ketoacidosis
Cheyne-Stokes respirations
- crescendo/decrescendo
- apnea
- repeat
- neurological damage
Two main types of IV fluid
- crystalloids: contain a salt but no particulates
- colloid: contain particulates, maybe also salts
Crystalloid fluids
- lactated ringers
- normal saline +/- dextrose
what happens if give 1/2 or 1/4 normal saline solution
dilute the physiologic saline, ok to do with reasonable kidney function but make sure don’t give too much free fluid without salt
*straight water IV needs to be in ICU
Colloids - 2 ex
- contain albumen
- blood :)
Fluid management objectives (5)
- treat the person not the lab value
- treat abnormalities at the approx rate they occured
- multiple problems should be treated in a sequence (next card)
- acidosis is related to elevations in K, Ca, Mg and alkalosis is opposite
- sx less severe if ALL electrolytes are low vs. just one
Sequence to treat problems
- fluid volume and perfusion deficits
- pH
- K, Ca, Mg
- Na, Cl
*when fluid and perfusion deficits are fixed, often pH and electrolytes will correct themselves
How to calculate baseline fluid requirements for an adult
- calculation
- first 10 kg = 100 ml/kg/24 hr
- second 10 kg = 50 ml/kg/24 hr
- weight > 20 kg = 20 ml/kg/24 hr
What is the K daily requirement
- 50-100 mEq/24hr but normal value is 60 mEq/24 hr
- what is normal rate of IV per hour
- how many cc in a liter
- 125 cc/hour
- 1000 cc in a liter
what is urine output goal for 24 hours
about 1 to 1.5 L (via foley)
- min 60 cc per hour
what is urine output directly related to
- GFR which is directly related to cardiac output
what adjustment is made to IV if patient has a fever
add extra 100-150 cc/24hr of fluid per 1 degree C of fever
