Electrolytes And Fluid Balance

Front 1

Na+

Normal range?
Significance?

Back 1

135-145 mEq/L

indicative of fluid balance in the body.
most abundant extracellular cation; main determinant of intravascular volume

Front 2

K+

Normal range?
Significance?

Back 2

3.5--5 mEq/L

indicates kidney function (+ if kidneys go south), acidosis (+) alkalosis (-) due to H+/K+ exchange pumps. most abundant extracellular cation

Front 3

Cl-

Normal range?
Significance?

Back 3

96-109 mEq/L

indicative of acid/base balance; changes opposite to CO2 (CO2 up, Cl down and vice versa)

Front 4

HCO3- (total CO2)

Normal range?
Significance?

Back 4

24-31 mEq/L

reflects acid/base balance. high = alkalosis; low = acidosis

Front 5

BUN

Normal range?
Significance?

Back 5

~6--20mg/dL in adults; higher in elderly, lower in kids

Reflects volume loss/overload in kidney dysfunction etc. BUN will go up faster than SCr. BUN:SCr ratio should be ~10; higher = vol depletion

Front 6

SCr

Normal range?
Significance?

Back 6

0.6-1.3 adults, 0.3-1.0 peds

indicates ability of kidneys to clear Cr; high = kidney damage.

Front 7

Gluc

Normal range?
Significance?

Back 7

70-100mg/dL fasting

T2DM control;

Front 8

pH

Normal range?
Significance?

Back 8

7.35-7.45

changes reflect acid/alkalemia

Front 9

Mg2+

Normal range?
Significance?

Back 9

1.8–3.0 mg/dL

muscle function, nerve transmission; serves as cofactor for Na/K ATPase. relatively safe even at ~7mg/dL (pre-eclampsia)

Front 10

Ca2+

Normal range?
Significance?

Back 10

8.5-10.9 mg/dL

bone disease, cardiac function, muscle function
elevated in malignant cancers, hypoparathyroidism, vitD excess
low in CKD

Front 11

How to correct for [Ca++] in hypoalbuminemia?

Back 11

Corrected [Ca2+] = Observed [Ca2+] + (0.8)(4.0 – albumin)

i.e. add 0.8 mg/dL Ca2+ for each 1.0 change from 4g/dL albumin

do this whenever albumin <4g/dL bc ~50% of total [Ca2+] is tightly bound by albumin.

Front 12

What is the ion gap, and why do we care?

Back 12

A.G. = [Na+] - ([Cl-] + [HCO3-]) = cations - anions

norm is ~12. represents unmeasured anions (globulins, sulfate, etc.)

Helps us isolate cause of metabolic acidosis.
large gap = acid accumulation. normal gap = Cl- gain or HCO3- depletion

Front 13

What is the maximal rate for correction of K+ levels? Why?

Back 13

10mEq/hr without cardiac monitoring

20mEq/hr with cardiac monitoring.

rapid changes mess with cardiac function.

Front 14

How much (in mEq) of Na+ and Cl- are in a 1.0L bag of NS?

Back 14

154 mEq of each

(308mEq total in bag; equivalent osmolarity of serum)

Front 15

What happens to electrolytes and acid/base in chronic diarrhea?

Back 15

-lose HCO3
-acidosis

Front 16

PO4(3-)

Normal Range?
Significance?

Back 16

2.6-4.5 mg/dL (4-7mg/dL peds)

needed for making ATP.
elevated in CKD, AKI; may cause hypocalcemia, hyperparathyroidism.
too low --> resp. failure.

Front 17

How to best go about correcting hyponatremia?

Back 17

First restore euvolemia with NS. Most Na+ imbalance is somehow related to fluid status.

Then IV NS (if pt can handle fluid vol) or 3-5% hypertonic saline (if pt can't handle large vol of fluid).

MAXIMUM change of >12mEq/L/day in either direction.

Front 18

What happens if Na+ changes too quickly?

Back 18

Increase Na+ --> crenation of brainstem cells, demyelination.

Decrease Na+ --> cerebral edema, also CNS damage.

Front 19

Where do the symptoms of Na+ imbalance manifest? K+ imbalance?

Back 19

Na+ CNS (confusion, seizures)

K+ heart (arrhythmias. always do an EKG if K+ is off)

Front 20

SIADH

Drugs that cause it?
How to correct it?

Back 20

Too much vasopressin --> no peeing --> xs free H2O, hyponatremia

carbamazepine, vinca alkaloids, cyclophosphamide

tx w/H2O restriction OR demeclocycline (blocks ADH from binding receptor --> LOTS OF PEE)

Front 21

Rough estimate of how much K+ is required to correct hypoK?

How many bananas?

Back 21

~100mEq K+ for every 1.0mEq drop below 3.0mEq/L.

1 banana = ~10mEq K+ (~425mg K+) so 10 bananas!

conclusion: don't use bananas

Front 22

How to correct hyperkalemia?

Back 22

Don't wait for euvolemia. Do EKG, IV Calcium gluconate, SHIFT K+ STAT to buy some time.

-IV NaHCO3 (K+ will go into cells as H+ comes out to buffer)
-Insulin + glucose (Na/K ATPase coupled to insulin receptor)
-Albuterol (b-adrenergic R coupled to Na/K ATPase)

Then transition pt to:
-thiazide or loop diuretic +/- fluid challenge
-kayexelate (Na+/K+ exch resin)
-dialysis

Front 23

Metabolic acidosis

pH
pCO2
HCO3-

Back 23

< 7.35 pH
pCO2 low (resp compensation)
HCO3- low

Front 24

Metabolic alkalosis

pH, pCO2, HCO3-?

Back 24

> 7.45 pH
pCO2 high (resp compensation)
HCO3- high

Front 25

Respiratory acidosis

pH, pCO2, HCO3-?

Back 25

<7.35 pH
pCO2 high (hypoventilation)
HCO3- high (kidneys retain bicarb to buffer)

Front 26

Respiratory alkalosis

pH, pCO2, HCO3-?

Back 26

> 7.45 pH
pCO2 low (hyperventilation)
HCO3- low (kidneys excrete HCO3-)