Barnes-Acid Base

Front 1

What is an anion gap?

Back 1

Anion gap= (Na+) – (Cl- + HCO3-)
Normal anion gap: 12 +/- 2
Albumin x 3 = expected anion gap
In metabolic acidosis, bicarbonate is diminished while other anions are increased

Front 2

What are the common causes of anion gap?

Back 2

MUDPILES
Methanol (formic acid)
Uremia
Diabetic ketoacidosis
Paraldehyde/phenformin
Iron tablets/INH
Lactic acidosis
Ethylene glycol (oxalic acid)
Salicylates

Front 3

What's the delta gap?

Back 3

Delta Gap=Measured AG – Expected AG; then add to measured HCO3-
If answer <24 con-commitant NAGMA
If answer >24 con-commitant Metabolic Alkalosis
(Another way to say this:
What was the Bicarb before the Anion was introduced?)

Front 4

What's compensation?

Back 4

respiratory system compensates for acidemia or alkalemia by either hyperventilation (acidemia response) or hypventilation (alkalemia response)
Winters Formula used for Acidosis:
1.5 * HCO3 + 8 = PCO2 +/- 2
Formula for Alkalosis (Summer’s Formula):
0.7 * HCO3 + 20= PCO2 +/- 5

Front 5

Case 1
Sodium 132 mEq/L
Urea Nitrogen 38 mg/dL
Potassium 6.0 mEq/L creatinine 2.6 mg/dL
Chloride 93 mEq/L
Bicarbonate 11 mEq/L
Glucose 720 mg/dL
Arterial blood gas analysis reveals: pH 7.26 and PCO2 25 mmHg

Back 5

Step 1: pH 7.26-Acidemia
Step 2: pH down; PCO2 down (compensation) = metabolic acidosis
Step 3: AG=(Na+) – (Cl- + HCO3-); (132) - (93 + 11) = 28
Step 4a: Winter's formula-ePCO2= 1.5 * 11 + 8= 24.5 +/- 2
Step 4b: Delta Gap= (28-12) +11=27 (con-commitant metabolic alkalosis)
Step 5-Differential Diagnosis
Step 6-Treatment

Front 6

Case 2 labs
Sodium 145 mEq/L
Urea Nitrogen 70 mg/dL
Potassium 1.9 mEq/L
creatinine 1.5 mg/dL
baseline creatinine 0.8 mg/dL)Chloride 86 mEq/L
Bicarbonate 45 mEq/L
pH 7.59 and PCO2 49 mmHg
Spot Urine Chloride is 74 mEq/L

Back 6

Step 1-Alkalemia
Step 2-pH up; PCO2 up = metabolic alkalosis
Step 3: AG-145 - (86 + 45)= 14
Step 4: Summer formula-ePCO2= 0.7 * 45 + 20= 51.5 +/- 5
Step 5-Differential Diagnosis
Step 6-Treatment

Front 7

What's metabolic alkalosis?

Back 7

Net loss of H+
Net addition of HCO3 (alkalai ingestion)
External loss of fluid containing Cl- (contraction alkalosis)

Front 8

Describe chloride responsive vs chloride non-responsive metabolic alkalosis

Back 8

Chloride-responsive-Urine Chloride <15-20 mEq/L
Chloride Non-responsive-Urine Chloride >20

Front 9

What are chloride responsive causes of metabolic alkalosis?

Back 9

Vomiting and NG suction
Diarrhea
Diuretics
Post-hypercapneic state

Front 10

What are chloride non-responsive causes of metabolic alkalosis?

Back 10

A. Mineralocorticoid excess (primary hyperaldosteronism, Adenoma, Cushing’s syndrome)
B. Apparent excess of mineralocorticoid (Licorice or Altoids, Liddle’s syndrome)
C. High dose Glucocorticoids
D. Normotensive-Severe K+ deficiency

Front 11

Case 3 Labs:
Serum lab values are:
Sodium 138 mEq/L
Urea Nitrogen 28 mg/dL
Potassium 4.2 mEq/L
creatinine 1.1 mg/dL
Chloride 112 mEq/L
Bicarbonate 14 mEq/L
Spot Urine Electrolytes: Sodium 100 mEq/L, Potassium 31 mEq/L,
Chloride 105 mEq/L 
Arterial blood gas analysis reveals: pH 7.32 and PCO2 28 mmHg

Back 11

Step 1-Acidemia
Step 2-pH down; PCO2 down = metabolic acidosis
Step 3: AG-138 - (112 + 14) = 12
Step 4: winter's formula-ePCO2= 1.5 * 14 + 8=29 +/- 2
Step 5-Differential Diagnosis
Step 6-Treatment

Front 12

What's happened in a non-anion gap metabolic acidosis (NAGMA)?

Back 12

bicarbonate is diminshed
chloride is increased

Front 13

What's a urinary anion gap?

Back 13

Urinary Anion Gap:
UAG= (Na + K+) – Cl-;
In a normal acid-base state, the UAG is (+) 30-50 mEq/l
Normal kidney function in metabolic acidosis, the UAG should be (-) 30-50 mEq/l, indicating a large amount of unmeasured ammonium cation (increased as extra H+ is secreted and paired w/ NH3 to be excreted as NH4).
Negative value suggests extra-renal origin (NH4+ in urine is the normal kidney response in the face of an acidosis)
Positive value suggests a renal origin in the presence of an acidosis

Front 14

What are the types of renal tubular acidosis?

Back 14

Type I (distal)
Type II (proximal)
Type IV
RTA of renal failure

Front 15

decreased H+ secretion
Normo-hypokalemia
Urine pH >5.3
HCO3<10 meq/L
Nephrocalcinosis
Urine pH constant

Back 15

Type I (distal) RTA

Front 16

decreased HCO3 reclamation
Normo-hypokalemia
Urine pH <5.3
HCO3 14-20
Urine pH variable

Back 16

Type II (proximal) RTA

Front 17

Aldosterone deficiency
Hyperkalemia
Urine pH < 5.3
HCO3 > 15
Associated with Diabetes
Measure Aldosterone

Back 17

Type IV RTA

Front 18

Decreased renal mass
Hyperkalemia
Urine pH < 5.5
Abnormal renal function

Back 18

RTA of renal failure

Front 19

A 68-year-old-woman is admitted with a one-week history of severe diarrhea. She is weak and appears lethargic. Blood pressure is 100/60 mmHg ( supine) and 70/40 mmHg (sitting). Mucous membranes are dry and there is poor skin turgor. There is no JVD or S3. Lungs are clear to auscultation. There is no peripheral edema. A Foley catheter is placed and a trace amount of dark urine is drained and is sent for analysis. She is begun on intravenous fluids. Urine output improves with fluid repletion.
Admission serum lab values are:
Sodium 137 mEq/L
Urea Nitrogen 77 mg/dL
Potassium 2.5 mEq/L
creatinine 3.0 mg/dL
Chloride 118 mEq/L
Bicarbonate 4.2 mEq/L
Spot urine electrolytes are: Sodium 25 mEq/L
Chloride 108 mEq/L
Potassium 40 mEq/L
Arterial blood gas analysis reveals: pH 7.04 and PCO2 16 mmHg

Back 19

Step 1-Acidemia
Step 2-pH down; PCO2 down = metabolic acidosis
Step 3-AG= 15
Step 4: winter's formula-ePCO2= 1.5 * 5 + 8= 15.5 +/- 2
Step 5 -Differential Diagnosis
Step 6-Treatment

Front 20

What are the causes of NAGMA (non anion gap metabolic acidosis)?

Back 20

diarrhea
glue sniffing
RTA
hyperchloremia

Front 21

What are Barnes' steps to acid-base disorders?

Back 21

1. Determine if the blood is Acidemic or Alkalemic
2. Determine the direction in change of PCO2 and pH (up or down from normal values)
3. Calculate the Anion Gap
4. PCO2 and HCO3 compensation; is there a mixed disorder
a. Winters formula: Expected pCO2 = 1.5 * HCO3- + 8 +/- 2
b. Delta Gap; Measured AG – Normal AG; then add to measured HCO3-
c. Metabolic Alkalosis: Expected pCO2 = 0.7 [HCO3] + 20 mmHg (range: +/- 5)
5. Map out your Differential Diagnosis
6. Treat underlying conditions unless pH in dangerous range, then treat with acute management.