acid base disturbances
Download
Skip this Video
Download Presentation
Acid-Base Disturbances

Loading in 2 Seconds...

play fullscreen
1 / 44

Acid-Base Disturbances - PowerPoint PPT Presentation


  • 112 Views
  • Uploaded on

Acid-Base Disturbances. Clinical Approach 2006 Pravit Cadnapaphornchai. Simple vs Mixed. Simple When compensation is appropriate Mixed When compensation is in appropriate. Simple Acid-Base Disturbances. When compensation is appropriate Metabolic acidosis ( ↓ HCO 3 , ↓ pCO 2 )

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Acid-Base Disturbances' - marcia-barker


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
acid base disturbances

Acid-Base Disturbances

Clinical Approach

2006

Pravit Cadnapaphornchai

simple vs mixed
Simple vs Mixed
  • Simple
    • When compensation is appropriate
  • Mixed
    • When compensation is inappropriate
simple acid base disturbances
Simple Acid-Base Disturbances
  • When compensation is appropriate

Metabolic acidosis (↓ HCO3, ↓ pCO2)

Metabolic alkalosis (↑ HCO3, ↑ pCO2)

Respiratory acidosis (↑ pCO2, ↑ HCO3)

Respiratory alkalosis (↓ pCO2, ↓ HCO3)

stepwise approaches
Stepwise Approaches
  • History & physical examination
  • Arterial blood gas for pH, pCO2, (HCO3)
    • Use the HCO3 from ABG to determine compensation
  • Serum Na, K, Cl, CO2 content
    • Use CO2 content to calculate anion gap
  • Calculate anion gap
    • Anion gap = {Na - (Cl + CO2 content)}
  • Determine appropriate compensation
  • Determine the primary cause
organ dysfunction
Organ dysfunction
  • CNS – respiratory acidosis (suppression) and alkalosis (stimulation)
  • Pulmonary – respiratory acidosis (COPD) and alkalosis (hypoxia, pulmonary embolism)
  • Cardiac – respiratory alkalosis, respiratory acidosis, metabolic acidosis (pulmonary edema)
  • GI – metabolic alkalosis (vomiting) and acidosis (diarrhea)
  • Liver – respiratory alkalosis, metabolic acidosis (liver failure)
  • Kidney – metabolic acidosis (RTA) and alkalosis (1st aldosteone)
organ dysfunction1
Organ Dysfunction
  • Endocrine
    • Diabetes mellitus – metabolic acidosis
    • Adrenal insufficiency – metabolic acidosis
    • Cushing’s – metabolic alkalosis
    • Primary aldosteronism – metabolic alkalosis
  • Drugs/toxins
    • Toxic alcohols – metabolic acidosis
    • ASA – metabolic acidosis and respiratory alkalosis
    • Theophylline overdose – respiratory alkalosis
stepwise approaches1
Stepwise Approaches
  • History & physical examination
  • Arterial blood gas for pH, pCO2, (HCO3)
    • Use the HCO3 from ABG to determine compensation
  • Serum Na, K, Cl, CO2 content
    • Use CO2 content to calculate anion gap
  • Calculate anion gap
    • Anion gap = {Na - (Cl + CO2 content)}
  • Determine appropriate compensation
  • Determine the primary cause
slide8

pH

< 7.35 7.4 >7.45

Acidosis

Metabolic

Respiratory

Mixed

Alkalosis

Metabolic

Respiratory

stepwise approaches2
Stepwise Approaches
  • History & physical examination
  • Arterial blood gas for pH, pCO2, (HCO3)
    • Use the HCO3 from ABG to determine compensation
  • Serum Na, K, Cl, CO2 content
    • Use CO2 content to calculate anion gap
  • Calculate anion gap
    • Anion gap = {Na - (Cl + CO2 content)}
  • Determine appropriate compensation
  • Determine the primary cause
slide10

CO2 content

LowNormalHigh

Metabolic acidosis Normal Metabolic alkalosis

Resp alkalosis Mixed Resp acidosis

A normal CO2 content + high anion gap = metabolic acidosis +

Metabolic alkalosis or metabolic ac + compensatory respiratory ac.

stepwise approaches3
Stepwise Approaches
  • History & physical examination
  • Arterial blood gas for pH, pCO2, (HCO3)
    • Use the HCO3 from ABG to determine compensation
  • Serum Na, K, Cl, CO2 content
    • Use CO2 content to calculate anion gap
  • Calculate anion gap
    • Anion gap = {Na - (Cl + CO2 content)}
  • Determine appropriate compensation
  • Determine the primary cause
calculation of anion gap in metabolic acidosis
Calculation of Anion Gap in Metabolic Acidosis

Anion gap = Na – (Cl + HCO3)

Normal 8 ± 2

Correction for low serum albumin

Add (4-serum albumin g/dL) X 2.5

to the anion gap

stepwise approaches4
Stepwise Approaches
  • History & physical examination
  • Arterial blood gas for pH, pCO2, (HCO3)
    • Use the HCO3 from ABG to determine compensation
  • Serum Na, K, Cl, CO2 content
    • Use CO2 content to calculate anion gap
  • Calculate anion gap
    • Anion gap = {Na - (Cl + CO2 content)}
  • Determine appropriate compensation
  • Determine the primary cause
compensations for metabolic disturbances
Compensations for Metabolic Disturbances
  • Metabolic acidosis
    • pCO2 = 1.5 x HCO3 + 8 ( ± 2)
  • Metabolic alkalosis
    • pCO2 increases by 7 for every 10 mEq increases in HCO3
how does the kidney compensate for metabolic acidosis1
How does the kidney compensate for metabolic acidosis?
  • By reabsorbing all filtered HCO3
  • By excreting H+ as NH4+ (and H2PO4- )

Interpretations

Urine pH < 5.5

Urine anion gap Negative

compensations for respiratory acidosis
Compensations for Respiratory Acidosis
  • Acute respiratory acidosis
    • HCO3 increases by 1 for every 10 mm increases in pCO2
  • Chronic respiratory acidosis
    • HCO3 increases by 3 for every 10 mm increases in pCO2

If you don’t have kidneys, can you have chronic respiratory acidosis?

compensations for respiratory alkalosis
Compensations for Respiratory Alkalosis
  • Acute respiratory alkalosis
    • HCO3 decreases by 2 for every 10 mm decrease in pCO2
  • Chronic respiratory alkalosis
    • HCO3 decreases by 4 for every 10 mm decrease in pCO2

If you don’t have kidneys can you have chronic respiratory alkalosis?

mixed acid base disorders
Mixed Acid-Base Disorders
  • Mixed respiratory alkalosis & metabolic acidosis
    • ASA overdose
    • Sepsis
    • Liver failure
  • Mixed respiratory acidosis & metabolic alkalosis
    • COPD with excessive use of diuretics
mixed acid base disorders1
Mixed Acid-Base Disorders
  • Mixed respiratory acidosis & metabolic acidosis
    • Cardiopulmonary arrest
    • Severe pulmonary edema
  • Mixed high gap metabolic acidosis & metabolic alkalosis
    • Renal failure with vomiting
    • DKA with severe vomiting
stepwise approaches5
Stepwise Approaches
  • History & physical examination
  • Arterial blood gas for pH, pCO2, (HCO3)
    • Use the HCO3 from ABG to determine compensation
  • Serum Na, K, Cl, CO2 content
    • Use CO2 content to calculate anion gap
  • Calculate anion gap
    • Anion gap = {Na - (Cl + CO2 content)}
  • Determine appropriate compensation
  • Determine the primary cause
generation of metabolic acidosis
Generation of Metabolic Acidosis

Loss of HCO3

diarrhea

Administration of

HCl, NH4+Cl, CaCl2, lysine HCl

Exogenous acids

ASA

Toxic alcohol

Endogenous acids

ketoacids

DKA

starvation

alcoholic

Lactic acid

L-lactic

D-lactate

H+

HCO3-

Compensations

Buffers

Lungs

Kidneys

High gap

Normal gap

If kidney function is normal, urine anion gap Neg

slide23

Loss of H+ from GI

Vomiting, NG suction

Congenital Cl diarrhea

Loss of H+ from kidney

1st & 2nd aldosterone

ACTH

Diuretics

Bartter’s, Gitelman’s, Liddle’s

Inhibition of β – OH steroid deh

H

HCO3

Compensations

Buffer

Respiratory

Forget the kidney

Gain of HCO3

Administered HCO3,

Acetate, citrate, lactate

Plasma protein products

case 1
CASE 1

A 24 year old diabetic was admitted for weakness.

Serum Na 140, K 1.8, Cl 125, CO2 6, anion gap 9.

pH 6.84 (H+ 144) pCO2 30, HCO3 5

interpretation of case 1

Interpretation of Case 1

Patient has normal gap metabolic acidosis

interpretation of case 11
Interpretation of Case 1
  • Next determine the appropriateness of respiratory compensation
    • pCO2 = 1.5 x HCO3 + 8 ( ± 2)
    • pCO2 = 1.5 x 5 + 8 + 2 = 17.5
      • The patient’s pCO2 is 30
  • The respiratory compensation is inappropriate
interpretation of case 12
Interpretation of Case 1
  • This patient has normal anion gap metabolic acidosis with inappropriate respiratory compensation
  • The finding does not fit DKA but is consistent with HCO3 loss from the GI tract or kidney
diarrhea vs rta
Diarrhea

History

Urine pH < 5.5

Negative urine anion gap

dRTA

History

Urine pH > 5.5

Positive urine anion gap

Diarrhea vs RTA
case 2
Case 2

A 26 year old woman, complains of weakness.

She denies vomiting or taking medications.

P.E. A thin woman with contracted ECF.

Serum Na 133, K 3.1, Cl 90, CO2 content 32, anion gap11.

pH 7.48 (H+ 32), pCO2 43, HCO3 32.

UNa 52, UK 50, UCl 0, UpH 8

interpretation of case 2
Interpretation of Case 2
  • Determine the appropriateness of respiratory compensation
    • For every increase of HCO3 by 1, pCO2 should increase by 0.7
    • pCO2 = 40 + (32-25) x 0.7 = 44.9
      • The patient’s pCO2 = 43
interpretation of case 21
Interpretation of Case 2
  • This patient has metabolic alkalosis with appropriate respiratory compensation
interpretation of case 22
Interpretation of Case 2
  • Urine Na+ 52, UK+ 50, Cl- 0, pH 8
    • Urine pH = 8 suggests presence of large amount of HCO3. The increased UNa and UK are to accompany HCO3 excretion. The kidney conserves Cl
  • The findings are consistent with loss of HCl from the GI tract
  • Final diagnosis = Self-induced vomiting
vomiting vs diuretic
Active vomiting

ECF depletion

Metabolic alkalosis

High UNa, UK, low UCl

Urine pH > 6.5

Remote vomiting

ECF depletion

Metabolic alkalosis

Low UNa, high UK, low Cl

Urine pH 6

Active diuretic

ECF depletion

Metabolic alkalosis

High UNa, UK and Cl

Urine pH 5-5.5

Remote diuretic

ECF depletion

Metabolic alkalosis

Low UNa, high UK, low Cl

Urine pH 5-6

Vomiting vs Diuretic
case 3
Case 3
  • A 40 year old man developed pleuritic chest pain and hemoptysis. His BP 80/50. pH 7.4, pCO2 25, HCO3 15 and pO2 50
interpretation of case 3
Interpretation of Case 3
  • A normal pH suggests mixed disturbances
interpretation of case 31
Interpretation of Case 3
  • His pCO2 is 25, his HCO315
    • If this is acute respiratory alkalosis his HCO3 should have been 25-{(40-25) x 2/10}= 22
    • If this is chronic respiratory alkalosis, his HCO3 should have been 25 – {(40-25) x 4/10} = 19
    • If this is metabolic acidosis, his pCO2 should have been 1.5 x 15 + 8 = 30-31
interpretation of case 32
Interpretation of Case 3
  • He has combined respiratory alkalosis and metabolic acidosis
  • The likely diagnosis is pulmonary embolism with hypotension and lactic acidosis or pneumonia with sepsis and lactic acidosis
  • Other conditions are ASA overdose, sepsis, liver failure
case 4
Case 4
  • A patient with COPD developed CHF. Prior to treatment his pH 7.35, pCO2 was 60 and HCO3 32. During treatment with diuretics he vomited a few times. His pH after treatment was 7.42, pCO2 80, HCO3 48.
interpretation of case 4
Interpretation of Case 4
  • Pt’s data pH 7.35, pCO2 60 and HCO3 32
  • For acute respiratory acidosis
    • For every 10 mm elevation of pCO2, HCO3 increases by 1, his HCO3 should have been 25 + (60-40) x 1/10 = 27
  • He did not have acute respiratory acidosis
interpretation of case 41
Interpretation of Case 4
  • Pt’s data pH 7.35, pCO2 60 and HCO3 32.
  • For chronic respiratory acidosis
    • For every 10 mm elevation of pCO2, HCO3 increases by 3
    • His HCO3 should have been 25 + (60-40) x 3/10 = 31
      • His HCO3 is 32
  • He had well compensated chronic respiratory acidosis
interpretation of case 42
Interpretation of Case 4
  • His pH is now 7.42, pCO2 80, HCO3 48
  • If pCO2 of 80 is due to chronic respiratory acidosis, HCO3 should only be 32 +(80-60) x 3/10=38 and not 48
  • He had combined metabolic alkalosis and respiratory acidosis after treatment of CHF
case 5
Case 5
  • A cirrhotic patient was found to be confused. Serum Na 133, K 3.3, Cl 115, CO2 content 14, anion gap 4
  • pH 7.44 (H+ 36), pCO2 20, HCO3 13
interpretation of case 5
Interpretation of Case 5
  • Determine the respiratory compensation
    • For chronic respiratory alkalosis, every 10 reduction in pCO2, HCO3 should decrease by 4
    • HCO3 should be 25 - (40-20) x 4/10=17
    • For acute respiratory alkalosis, HCO3 = 21
    • Patient’s HCO3 is 13, suggesting a metabolic acidotic component is present
  • Anion gap is 4, even corrected for low albumin, is still low suggesting a normal gap metabolic acidosis
  • Patient had combined metabolic acidosis and respiratory alkalosis
ad