Transcript METABOLIC ACIDOSIS

METABOLIC
ACIDOSIS
III-D2
Rodriguez, Jan Gayl – Sahagun, Marie Janice
SALIENT FEATURES
OBJECTIVE
• 45 Y/O FEMALE
• HIGH GRADE FEVER (39oC)
• CHILLS
• MYALGIA
• DIARRHEA
• BP : 84/52
• PR : 118 BEATS PER MINUTE
• RR : 42 CYCLES PER MINUTE,
LABORED
SUBJECTIVE
• DIABETES MELLITUS
• NO MEDICATIONS/
ALCOHOL
• DRY MUCOUS
MEMBRANES
• FLAT NECK VEINS
• NO EDEMA
• FIRM, MILDLY TENDER,
DISTENDED ABDOMEN
• HYPERACTIVE BOWEL
SOUNDS
SALIENT FEATURES
OBJECTIVE
(LAB DATA)
ACTUAL
NORMAL
Hemoglobin
15.5 g/dL
12-16
g/dL

Hematocrit
48 %
37-48%

WBC count
22.8x103
4.5-11
x103

ACTUAL
NORMAL
Serum
Creatinine
2.4 mg/dl
0.35-0.9
mg/dl

Lactate
3.0 meq/L
0.5-1.3
mEq/L

pH
7.39
7.347.44

pCO2
17.0
mmHg
35-45
mmHg

Glucose
342.0
mg/dL
65-110
mg/dL

Segmenters
Bands
66 %
50-70%
23 %
0-5%


Serum Na
138
meq/L
135-145
mEq/L

Ketones
None
None

Serum K
4.2
meq/L
3.5-5.0
mEq/L

BUN
28.0
mg/dL
7-21
mg/dL

Serum Cl
108
meq/L
95-108
meq/L

HCO3
10.0
meq/L
22-26
mEq/L

WHAT IS THE ACID BASE
DISTURBANCE PRESENT IN THIS
CASE?
METABOLIC ACIDOSIS
Respiratory
acidosis
Respiratory
alkalosis
Metabolic
alkalosis
Metabolic
acidosis
Patient
Normal
values
pH
7.38 – 7.44
H+
40 meq/L
pCO2
35 – 45
mmHg
HCO3
21 – 30
meq/L
METABOLIC ACIDOSIS
• Infection  Increased plasma lactate: 3.0
meq/L
• Severe diarrhea  Decreased serum
bicarbonate: 10 meq/L
• Increased serum chloride: 108 meq/L
• Kussmaul respiration
• Decreased PCO2 : 17 mmHg (compensated)
• Normal blood pH: 7.39 (compensated)
ALGORITHM FOR THE
DIAGNOSIS OF THE ACID BASE
DISORDER
1. Establish database
2. Identify the main disorder:
3. Evaluate compensation (using the formulas)
4. Determine the anion gap (AG, normal = 12).
* If the AG is >20 = metabolic acidosis
* If there is an AG,
 Calculate the gap-gap (delta-gap) = patient’s anion gap
– 12 (normal anion gap).
 Calculate the delta HCO3 = normal HCO3 (use 25) – the
patient's HCO3.
 delta-gap ÷ delta HCO3 should normally be between 1-2
If < 1 = combined non-gap and gap acidosis
If > 2 suggests = metabolic alkalosis.
RULE OF THUMB IN BEDSIDE
INTERPRETATION OF ACID BASE
DISORDER
RULE OF THUMB
Metabolic acidosis
•
PaCO2 should fall by 1.0 to 1.5 X the fall in
plasma HCO3- concentration
•
pCO2 should rarely be < 20 mmHg.
•
Bicarbonate deficit (mEq/L) = [0.5 x BW(kg)] x
(24 - HCO3)
Metabolic alkalosis
•
PsCO2 should rise by 0.25 to 1.0 X the rise in
plasma HCO3- concentration
RULE OF THUMB
Acute respiratory acidosis
•
Plasma HCO3- concentration should rise by about
1 mmole per liter for each 10 mm Hg increment
in PaCO2 ( 3 mmoles per liter).
•
Acute change pH/pCO2 = 0.008
Chronic respiratory acidosis
•
Plasma HCO3- concentration should rise by about 4
mmoles per liter for each 10 mm Hg increment in
PaCO2 ( 4 mmoles per liter).
•
Chronic change pH/pCO2 = 0.003
RULE OF THUMB
Acute respiratory alkalosis
•
Plasma HCO3- concentration should fall by about
1 to 3 mmoles per liter for each 10 mm Hg
decrement in the PaCO2, usually not to less than
18 mmoles per liter
•
Acute change pH/pCO2 = 0.008
Chronic respiratory alkalosis
•
Plasma HCO3- concentration should fall by about 2
to 5 mmoles per liter per 10 mm Hg decrement in
PaCO2 but usually not to less than 14 mmoles per
liter.
•
Chronic change pH/pCO2 = 0.003
HOW DO YOU COMPUTE FOR THE
ANION GAP?
WHAT IS ITS SIGNIFICANCE?
COMPUTE FOR THE ANION GAP OF
THIS PATIENT
ANION GAP COMPUTATION
• Anion Gap
 represents the difference between the
concentration of the major plasma cation (Na+)
and the major plasma anions (Cl- and HCO3-)
• Formula
AG = [Na+] – ([Cl-] + [HCO3-])
SIGNIFICANCE OF AG
• Nonvolatile acid added to body fluids  ↑ [H+], ↓ pH, ↓
[HCO3-]  ↑ Anion Concentration
• Change in Anion
- provides convenient way to analyze and help determine
the cause of metabolic acidosis
• NV 10-12 mmol/L
• Normal AG
- Anion of nonvolatile acid  Cl• High AG
- Anion of nonvolatile acid  Lactate, β-hydroxybutyrate
Calculation of AG is a useful way to identify the
cause of a metabolic acidosis
AG COMPUTATION (Case)
AG = [Na+] – ([Cl-] + [HCO3-])
= [138] – ([108) + [10])
= 20 meq/L (High AG)
ANION GAP
Normal Anion Gap
High Anion Gap
• Loss of bicarbonate
• Addition of HCl
• Renal Tubular
Dysfunction
• Overproduction of
organic acids
• Failure of the
kidneys to maintain
bicarbonate levels
Normal Anion Gap
• Diarrhea
• Renal Tubular Acidosis
• Carbonic Anhydrase Inhibition
High Anion Gap
•
•
•
•
Lactic Acidosis
Ketoacidosis
Drug and Toxin Induced
Advanced Renal Failure
Prediction of Compensatory Responses on
Simple Acid Base Disturbances
• Acid-Base Nomogram
– Shaded areas show 95% confidence limits for
normal compensation
– Finding acid-base values within the shaded
areas does not rule out a mixed disturbance
– Not a substitute for computation
Prediction of Compensatory Responses on
Simple Acid Base Disturbances
• Acid-Base Nomogram
– pH 7.39
– HCO3 10 mEq/L
– PCO2 17 mmHg
TREATMENT
• Antibiotic
• IVF/Vasopressors