8/3/2019 Corrected Electrolytes

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CORRECTED ELECTROLYTES

EXPECTED pCO2(In primary metabolic disturbance)ie is there a co-existing respiratory problem besides compensation?

IN METABOLIC ACIDOSIS:Expected pCO2 = (1.5 x HCO3) + 8 (+/-2)

if < than expected, then RESP ALKALOSIS existsif > than expected, then RESP ACIDOSIS exists

IN METABOLIC ALKALOSISExpected pCO2 = (0.9 x HCO3) + 9 (+/-2)

if < than expected, then RESP ALKALOSIS exists

if > than expected, then RESP ACIDOSIS exists

Alternative Method for Expected pCO2In primary met acidosis, pCO2 should = last 2 digits of pH between ph 7.4-7.1In primary met alkalosis, pCO2 should = last 2 digits of pH between ph 7.4-7.6

EXPECTED/CORRECTED BICARBIn Respiratory Acidosis

Acute: HCO3 1 (from 24) per 10 in pCO2 (Max 30)Chronic: HCO3 4 (from 24) per 10 in pCO2 (Max 36)Observed > Expected: = Concurrent Metabolic AlkalosisObserved < Expected: = Concurrent Metabolic Acidosis

CHECK ANION GAP!!!Observed = Expected: = Adequate compensation

Respiratory Alkalosis

Acute: HCO3 2 (from 24) per 10 in pCO2 (Min18)Chronic: HCO3 5 (from 24) per 10 in pCO2 (Min12)Observed > Expected: = Concurrent Metabolic Alkalosis

Observed < Expected: = Concurrent Metabolic Acidosis CHECK ANION GAP!!!Observed = Expected: = Adequate compensation

CORRECTED SODIUM (pseudo-hyponatremia)For each 3mmol/L increase in glucose adjust Na+ upwards by 1 mmol/L

Corrected Na+ = (Na+) + GLUCOSE3

Also artificially lowered by mannitol, sorbitol, glycerolOsmotically active substances draw water into ECF and increase the sodium

free space

8/3/2019 Corrected Electrolytes

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CORRECTED POTASSIUM

Each 0.10 in pH (from 7.4) = K+ by 0.5

Each 0.02 in pH (from 7.4) = K+ by 0.1

Method 1: Can add this number to observed K+Eg If pH 7.10, K+ 5.3

pH has from 7.4 7.1 = 0.3 (= 3 x 0.1)

So expect K+

to by 3 x 0.5 = 1.5So Expected K+ for this level of pH = 5.3 + 1.5 = 6.8This means: Observed K+ < Expected K+= Whole body K

+deficient

= Will need K+ replacement as acidosis resolves

OR: The better way

Method 2: Can subtract this number from observed K+

pH has from 7.4 7.1 = 0.3 (= 3 x 0.1)

So expect K+ to by 3 x 0.5 = 1.5So Expected K+ = 5.3 1.5 = 3.8= This is the level you can expect K

+to drop to as acidosis resolves

ie theyll become potassium deplete & need replacementPROBABLY BETTER TO DO IT THIS WAYEasier & quicker to write in VAQ:

Note: Given pH anticipate K+ to to (x) (K+ 0.5 per 0.1 in pH)Quicker & you dont need to write sums/explanation

CORRECTED CALCIUMAdd 0.10 to Ca2

+for every 5 albumin is below 40

Add 0.02 to Ca2+ for every 1 albumin is below 40