Mole

Gram molecular weight of a substance (a.k.a. molar weight)

6.022 x 1023 entities

Millimole (mM)

Milligram molecular weight of a substance (a millimole is 1/1000 of a mole)

Weight of a substance (milligrams) Milliequivalents (valence of ion) Moles x 1000

Equivalent weight

Gram weight of a substance which will combine with or replace 1 gram (1 mole) of hydrogen; an equivalent weight can be determined by dividing the molar weight of a substance by its ionic valence.

Moles x valence of ion

Miilliequivalent (mEq)

Milligram weight of a substance which will combine with or replace 1 milligram (1 millimole) of hydrogen (a milliequivalent is 1/1000 of a equivalent)

Millimoles x valence of ion Equivalents x 1000 [Molecular weight (grams) / valence] x [1/1000]

Calcium

Ca2+

2

40

Chloride

Cl-

1

35.5

Magnesium

Mg2+

2

24

Phosphate

HPO4- (80%)

1.8

961

Phosphate pH = 7.4

H2PO4- (20%)

1.8

961

Potassium

K+

1

39

Sodium

Na+

1

23

Sulfate

SO4-

2

961

Mg/100mL --> mEq/L

[(mg/100mL) x 10 x valence] / atomic weight = mEq/L

mEq/L --> mg/100mL

[(mEq/L) x atomic weight] / 10 x valence = mg/100mL

mEq/L --> volume of percent of a gas

[(mEq/L) x 22.4 / 10] = volume percent

Calcium carbonate [CaCO3]

20

50

Calcium chloride [CaCl2 * 2H2O]

14

74

Calcium gluceptate [Ca(C7H13O8)2]

2

245

Calcium gluconate [Ca(C6H11O7)2 * H2O]

5

244

Calcium lactate [Ca(C3H5O3)2 * 5H2O]

7

154

Magnesium gluconate [Mg(C6H11O7)2 * H2O]

5

216

Magnesium oxide [MgO]

50

20

Magnesium sulfate [MgSO4]

17

60

Magnesium sulfate [MgSO4 * 7H2O]

8

123

Potassium acetate [K(C2H3O2)]

10

98

Potassium chloride [KCl]

13

75

Potassium citrate [K3(C6H5O7) * H2O]

9

108

Potassium iodide [KI]

6

166

Sodium acetate [Na(C2H3O2)]

12

82

Sodium acetate [Na(C2H3O2) * 3H2O]

7

136

Sodium bicarbonate [NaHCO3]

12

84

Sodium chloride [NaCl]

17

58

Sodium citrate [Na3(C6H5O7) * 2H2O]

10

98

Sodium iodine [NaI]

7

150

Sodium lactate [Na(C3H5O3)]

9

112

Zinc sulfate [ZnSO4 * 7H2O]

7

144

Aa gradient

Alveolar arterial oxygen gradient

FiO2

Inspired oxygen (expressed as a fraction) (0.21 in room air)

PaCO2

Arterial partial pressure carbon dioxide (mmHg)

PaO2

Arterial partial pressure oxygen (mmHg)

PIO2

Oxygen partial pressure of inspired gas (mmHg) (150mmHg in room air at sea level)

R

Respiratory exchange quotient (typically 0.8, increases with high carbohydrate diet, decreases with high fat diet)

Water deficit Note: Body weight is estimated weight in kg when fully hydrated; Na+ is serum or plasma sodium. Use corrected Na+ if necessary. Consult medical references for recommendations for replacement of deficit.

0.6 x body weight [1-140/Na+0]

Total serum calcium corrected for albumin level

[(Normal albumin - patient's albumin) x 0.8] + patient's measured total calcium

Acid base assessment (Henderson- Hasselbach equation)

pH = 6.1 + log((HCO3-/(0.03)(pCO2))

Alveolar gas equation

PIO2 = FiO2 x (total atmospheric pressure - vapor pressure of H2O at 37oC) PIO2 = FiO2 x (760mmHg - 47mmHg) PAO2 = PIO2 - PACO2 / R

Alveolar/arterial oxygen gradient (Aa gradient) Normal ranges: Children 15-20mmHg Adults 20-25mmHg

PAO2 - PaO2 [(713) (FiO2 - (PaCO2 / 0.8))] - PaO2

Acid-base equation

H+ (in mEq/L) = (24 x PaCO2) / HCO3-)

Corrected Na+ Note: Do not correct for glucose <150.

Measured Na2+ [1.5 x (glucose - 150 / 100)]

Acute metabolic acidosis

PaCO2 expected = 1.5 (HCO3-) + 8 ± 2 or expected decrease in PaCO2 = 1.3 (1-1.5) x decrease in HCO3-

Acute metabolic alkalosis

Expected increase in PaCO2 = 0.6 (0.5-1) x increase in HCO3-

Acute respiratory acidosis (<6h duration)

For every PaCO2 increase of 10mmHg, HCO3 increases by 1mEq/L

Chronic respiratory acidosis (>6h duration)

For every PaCO2 increase of 10mmHg, HCO3 increases by 4mEq/L

Acute respiratory alkalosis (<6h duration)

For every PaCO2 decrease of 10mmHg, HCO3 decreases by 2mEq/L

Chronic respiratory alkalosis (>6h duration)

For every PaCO2 decrease of 10mmHg, HCO3 decreases by 5mEq/L