pathophysiology of acid-base disorders tyler paradis md resident anesthesiologist ohsu apom...

PATHOPHYSIOLOGY OF ACID-BASE DISORDERSTyler Paradis MDResident AnesthesiologistOHSU APOMSaturday, Nov 21st 2015

1

Objectives

•Understand Pathophysiology of acid base balance

•Understand the various acid base abnormalities

•Understand how to interpret an ABG

2

CO2 TRANSPORT IN THE BLOOD

3

FORMS OF CO2 TRANSPORT IN THE BLOOD

4

1.Combined with Hemoglobin (~10%)

2.Dissolved in Plasma (~5%)

3.Bicarbonate (80-90%)

Carbamino-Hemoglobin

5

HHb–NH2 + CO2 ↔ HHb–NHCOO- + H+

• CO2 binds to terminal amino groups on the globin chains of hemoglobin.

• Deoxygenated Hb binds CO2 more readily than oxygenated Hb – known as the Haldane effect. As a result, CO2 content is higher in venous than arterial blood.

• CO2 also forms small amounts of carbamino compounds with plasma proteins.

Dissolved CO2

6

• Dissolved CO2 content is proportional to its partial pressure and solubility.

• The solubility of CO2 is 20x > O2.

Dissolved CO2

7

• Dissolved CO2 content is usually expressed in mEq/L blood.

• Dissolved CO2 = PCO2 x 0.03 (mm Hg) (mEq CO2/L/mm Hg)

= 40 x 0.03

= 1.2 mEq CO2/L

Bicarbonate Formation and the Chloride Shift

8

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

Carbonic Anhydrase

Cl-

RBC

Plasma

➢The presence of carbonic anhydrase in red blood cells results in rapid formation of bicarbonate within erythrocytes.

➢ There is no carbonic anhydrase in the plasma, so the CO2 hydration equation proceeds very slowly in plasma.

➢ HCO3- diffuses down its concentration gradient from RBCs into the plasma in

exchange for Cl-, a process called the chloride shift.

➢ The chloride shift is mediated by Band 3, a major membrane protein.

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

(slow)

ACID-BASE BALANCE AND

DISORDERS

9

CO2 HCO3_ CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3

_

Blood Kidney

Lung

The lungs regulate arterial PCO2 and thus the concentration of dissolved CO2 in blood via changes in alveolar ventilation, while the kidneys regulate [HCO3

_ ] via changes in renal H+ excretion.

Role of the Lungs and Kidneys in Acid-Base Homeostasis

10

Relationship Between The pH And The H+ Concentration In The Physiologic Range

pH H+

nM/L

7.8 16

7.7 20

7.6 26

7.5 32

7.45 36

7.4 40

7.35 45

pH H+

nM/L

7.3 50

7.2 63

7.1 80

7.0 100

6.9 125

6.8 160

11

Henderson - Hasselbalch Equation

pH = pK of carbonic acid + log

= 6.1 + log

[Dissolved CO2]

[HCO3_]

[0.03 PCO2]

[HCO3_]

12

Normal Acid - Base Balance

pH

7.0 7.2 7.4 7.8

H+ nm/L

1.2 24

7.6

40 25 20316379 50

HCO3_Dissolved

CO2

KidneyLung

13

Characteristics Of The Primary Acid - Base Disorders

Metabolic Acidosis

Metabolic Alkalosis

Respiratory Acidosis

Respiratory Alkalosis

[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p

pH Primary Disturbance

CompensatoryResponse

14


An abnormal physiological process in which there is a primary increase in PaCO2 due to a primary decrease in alveolar ventilation (hypoventilation), which results in a decreased ratio of [HCO3

_ ] / [dissolved CO2] and a decrease in the pH of the blood.

15

pH

7.0 7.2 7.4 7.8

H+ nm/L

2.4

24

7.6

40 25 20316379 50

HCO3_Dissolved

CO2

Kidney

Lung

pH

7.0 7.2 7.4 7.8

H+ nm/L

2.440

7.6

40 25 20316379 50

HCO3_

Dissolved CO2

KidneyLung

Respiratory AcidosisAnd Acidemia

Compensated RespiratoryAcidosis

16

Causes of Respiratory Acidosis (Alveolar Hypoventilation)

I. Airway Obstruction A. Chronic Obstructive Lung Disease B. Upper Airway ObstructionII. Chest Wall Restriction A. Kyphoscoliosis B. Pickwickian SyndromeIII. Respiratory Center Depression A. Anesthetics B. Sedatives

C. Opiates D. Brain injury or disease E. Severe hypercapnia, hypoxiaIV. Neuromuscular disorders A. Spinal cord injury B. Phrenic nerve injury C. Poliomyelitis D. Myasthenia Gravis E. Guillian-Barré Syndrome F. Administration of Curare-like Drugs G. Respiratory Muscle Diseases

17


An abnormal physiological process in which there is a primary decrease in PaCO2 due to a primary increase in alveolar ventilation (hyperventilation) resulting in an increase in the ratio of HCO3

- to dissolved CO2, and an increase in arterial pH.

18

pH

7.0 7.2 7.4 7.8

H+ nm/L

0.6

24

7.6

40 25 20316379 50

HCO3_

Dissolved CO2

Kidney

Lung

pH

7.0 7.2 7.4 7.8

H+ nm/L

0.6

14

7.6

40 25 20316379 50

HCO3_

Dissolved CO2

Kidney

Lung

Respiratory AlkalosisAnd Alkalemia

Compensated RespiratoryAlkalosis

19

Causes of Respiratory AlkalosisI. Respiratory Center Stimulation A. CNS 1. Anxiety 2. Hyperventilation Syndrome 3. Inflammation (encephalitis, meningitis) 4. Stroke 5. Tumors B. Drugs or Hormones 1. Salicylates 2. Progesterone 3. Hyperthyroidism C. Reflex 1. Hypoxemia 2. High Altitude 3. Metabolic Acidosis 4. Sepsis, fever 5. Pulmonary Embolism 6. Pulmonary Edema 7. Congestive Heart Failure 8. AsthmaII. Iatrogenic Mechanical OverventilationIII. Liver Failure

20

Metabolic Alkalosis

An abnormal physiological process in which there is a primary increase in [HCO3

_ ] due to an excessive gain of base (HCO3

_ ) or loss of acid (H+) resulting in an increase in the ratio of HCO3

- to dissolved CO2 and a rise in arterial pH.

21

pH

7.0 7.2 7.4 7.8

H+ nm/L

1. 2

34

7.6

40 25 20316379 50

HCO3_

Dissolved CO2

Kidney

Lung

pH

7.0 7.2 7.4 7.8

H+ nm/L

1. 5

34

7.6

40 25 20316379 50

HCO3_

Dissolved CO2

Kidney

Lung

Metabolic AlkalosisAnd Alkalemia

Compensated MetabolicAlkalosis

22

Causes of Metabolic AlkalosisI. Loss of Hydrogen Ions A. Vomiting B. Nasogastric Suction C. Gastric fistulas D. Diuretic therapy E. Severe Magnesium or Potassium Deficiency F. Overproduction of mineralocorticoids (Cushing’s syndrome; Primary hyperaldosteronism; renal artery stenosis) G. Ingestion of mineralocorticoids (Licorice ingestion; chewing tobacco) H. Inherited Disorders (Bartter’s Syndrome; Liddle’s syndrome; Gitelman’s syndrome)

II. Ingestion or administration of excess bicarbonate or other bases A. Intravenous bicarbonate B. Ingestion of bicarbonate or other bases (e.g., antacids)

23

Metabolic Acidosis

An abnormal physiological process in which there is a primary decrease in arterial [HCO3

_ ] due to an excessive loss of base (HCO3

_ ) or gain of acid (H+) resulting in a decrease in the ratio of HCO3

- to dissolved CO2 and thus a decrease in arterial pH. .

24

pH

7.0 7.2 7.4 7.8

H+ nm/L

1. 2

12

7.6

40 25 20316379 50

HCO3_Dissolved

CO2

Kidney

Lung

pH

7.0 7.2 7.4 7.8

H+ nm/L

0.612

7.6

40 25 20316379 50

HCO3_

Dissolved CO2

KidneyLung

Metabolic AcidosisAnd Acidemia

Compensated MetabolicAcidosis

25

Serum Electrolyte Concentrations

Na+ 136 - 145 mEq/L

K+ 3.5 - 5.0 mEq/L

Cl_ 100 - 106 mEq/L

CO2 Content (HCO3-) 24 - 28 mEq/L

Ca++ 4.3 - 5.3 mEq/L

Mg++ 1.5 - 2.5 mEq/L

HPO4_ _ , H2PO4

_ 1.5 - 3.0 mEq/L

H+ 40 x 10 _ 6 mEq/L

Anion Gap

[Na+ ] - ([Cl_ ] + [HCO3_ ]) Normal = 12 ± 4 mEq/L

140 - (103 + 25) = 12

26

Normal Metabolic Acidosis

Hyperchloremic

(Normal Gap)

Normochloremic

(Increased Gap)

A_

24

A_

12A_

12

HCO3-

25

HCO3-

13 HCO3-

13

Cl_

103

Cl_

115 Cl_

103

Na+

140

Na+

140Na+

140

Classification of metabolic acidosis arrived at by using anion gap. Bar A shows the normal relationship of the unmeasured anions (A_, anion gap) to plasma electrolytes; B and C illustrate the respective anion compositionof plasma in hyperchloremic and normochloremic metabolic acidosis.

A B C

27

Differential Diagnosis of Metabolic Acidosis

Normal Anion Gap (Hyperchloremia)

I. Gastrointestinal loss of HCO3_

A. Diarrhea B. Small bowel or pancreatic drainage or fistula C. Ureterosigmoidostomy, jejunal loop, ileal loop conduit D. DrugsII. Renal Loss of HCO3

_ A. Carbonic anhydrase inhibitors B. Renal tubular acidosis (RTA) III. Miscellaneous A. Dilutional acidosis B. Hyperalimentation

I. Lactic AcidosisII. Ketoacidosis A. Diabetic B. Starvation C. AlcoholicIII. Ingestion of Toxic Substances A. Salicylate overdose B. Paraldehyde poisoning C. Methyl alcohol ingestion D. Ethylene glycol ingestionIV. Failure of Acid Excretion A. Acute renal failure B. Chronic renal failure

Increased Anion Gap (Normochloremic)

28

Excess H+

H+ + HCO3_ ↔ H2CO3

_

H2CO3_ ↔ CO2 + H20

Diffusion Into Cells

Renal H+ Excretion

( Immediate )

ExtracellularBuffering

(Minute to Hours)

Respiratory Compensation

(2 - 4 hours )

IntracellularBuffering

(Hours to Days)Renal

Compensation

Lungs

29

Magnitude of Compensatory Responses To Acid - Base Disorders

Respiratory Compensation:

Metabolic Acidosis:1.2 mmHg ↓ in PCO2 per mEq/L ↓ in [HCO3

_ ]

Metabolic Alkalosis:0.7 mmHg ↑ in PaCO2 for every mEq/L ↑ in [HCO3

_ ]

Renal Compensation:

0.4 mEq/L Δ [HCO3_ ] for every mmHg Δ PaCO2

30

Simple vs. Mixed Acid-Base Disturbances

Simple Acid-Base Disturbance:

A single primary disturbance in acid-base balance that may or may not be associated with a secondary compensatory process modifying the change in pH.

Mixed Acid-Base Disturbance:

Combination of 2 or more primary disturbances of acid-base balance occurring at the same time,each of which would independently alter the pH.

1. Combination of primary acid-base disturbances that may augment their effect in pH. A. Combined metabolic and respiratory acidosis. B. Combined metabolic and respiratory alkalosis.

2: Combination of primary acid-base disturbances that tend to cancel out their effects on pH. A. Metabolic acidosis and respiratory alkalosis. B. Respiratory acidosis and metabolic alkalosis.

31

Interpretation of Arterial Blood Gas Results

A. Examine pH to determine if acidosis ( < 7.40 ) or alkalosis ( > 7.40 ).

B. Examine PaCO2 to see if there is a respiratory component to the acid-base disorder.

C. Examine [HCO3_ ] to see if there is a metabolic component to the

acid-base disorder.

D. Is there compensation? Is it appropriate ? Simple vs. Mixed disorder?

E. For mixed disturbance can calculate ΔAG (AG – normal AG)

F. Examine PaO2 to assess oxygenation.

32

Characteristics Of The Primary Acid - Base Disorders

Metabolic Acidosis

Metabolic Alkalosis



[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p



33

Arterial Blood Sample

Acidosis Alkalosis

Metabolic acidosis

Respiratory acidosis

MetabolicAlkalosis

Respiratoryalkalosis

Respiratory compensation

Renal compensation


Renal compensation

pH < 7.4

pH > 7.4

PCO2 < 35 mmHg[ HCO3_ ] > 26 mEq/LPCO2 > 45 mmHg[ HCO3

_ ] < 22 mEq/L

PCO2 < 35 mm Hg [ HCO3_ ] > 26 mEq/L PCO2 > 45 mm Hg [ HCO3

_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2

per mEq/L ↓ [ HCO3_ ]

*4 mEq/L ↑ [ HCO3_ ]

Per 10 mm Hg ↑PCO2 * 0.7 mm Hg ↑ PCO2

per mEq/L ↑ [ HCO3_ ]

* 4 mEq/L ↓ [ HCO3_ ]

per 10 mm Hg ↓ PCO2

* If the compensatory response is not appropriate, a mixed acid-base disorder should be suspected

34

The Bigger Picture - The Systematic Approach to A Patient With An Acid-Base Disorder.

In the clinical setting, the acid-base laboratory data (pH, PaCO2, HCO3_ ) should never be evaluated

independently of :

A. Patient History - Evaluate for potential processes related to acid-base disturbances.

B. Physical Examination - Are there clues relevant to acid-base, cyanosis, fever, nasogastric tube breathing pattern, tetany, hypotension, COPD, etc.

C. Plasma Electrolyte Concentrations

1. Na+, K+, Cl-, CO2 content

2. Anion gap (unmeasured anions) = Na+ - [HCO3_ + Cl- ]

a. Normal value = 12 mEq/L

b. Useful in clinical diagnosis of different causes of metabolic acidosis 1) High Anion Gap acidosis 2) Normal Anion Gap Acidosis

D. Other laboratory Data - Blood sugar, BUN, blood ammonia, blood cultures, pulmonary function data, x-rays, urine data, etc.

35

Acid-Base InterpretationpH PaCO2 [HCO3

-]

1. 7.63 20 22


-]

1. 7.63 ↑ 20 22

alkalosis


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]




-]

1. 7.63 20 ↓ 22

alkalosis

respiratory

Is there any compensation?

Metabolic Acidosis

Metabolic Alkalosis



[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p




-]

1. 7.63 20 22 -Normal range

Uncompensated respiratory alkalosis


-]

2. 7.47 20 16


-]

2. 7.47 ↑ 20 16

alkalosis


-]

2. 7.47 20 ↓ 16

alkalosis

respiratory

IS THERE COMPENSATION FOR THE RESPIRATORY ALKALOSIS?

Metabolic Acidosis

Metabolic Alkalosis



[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p




-]

2. 7.47 20 16 ↓

Yes, there is renal compensation for the respiratory alkalosis.

Is compensation appropriate?


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]




-]

7.47 20 16

Therefore, Compensated respiratory alkalosis

PCO2 is decreased from 40 to 20= 20

So there can be 2 x 4 or 8 mEq/L ↓ in [HCO3

-]24-8 =

16

Compensation for respiratory alkalosis:4 mEq/L ↓ [ HCO3

_ ] per 10 mm Hg ↓ PCO2

Comparing # 1 and # 2, pH PaCO2 [HCO3

-]

1. 7.63 20 26

2. 7.47 20 16

Renal compensatory excretion of HCO3

- lowered pH down towards normal

level.


-]

3. 7.22 60 24

50


-]

3. 7.22 ↓ 60 24

acidosis


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]



52


-]

3. 7.22 ↑ 60 24

acidosisrespiratory

Is there any compensation for the Respiratory Acidosis?

Metabolic Acidosis

Metabolic Alkalosis



[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p




-]

3. 7.22 60 24 - Normal

uncompensated (acute) respiratory acidosis


-]

4. 7.33 60 30

56


-]

4. 7.33 ↓ 60 30

acidosis


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]



58


-]

4. 7.33 ↑ 60 30

acidosis

respiratory

Is there any compensation for the Respiratory Acidosis?

Metabolic Acidosis

Metabolic Alkalosis



[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p




-]

4. 7.33 60 30 ↑

Yes, there is renal compensation.

Is it appropriate?


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]



Acid-Base Interpretation

pH PaCO2 [HCO3-]

7.33 60 30

Partially compensated respiratory acidosis

(possibly a mixed disorder)

[HCO3-] is increased 6 mEq/L above normal of

24.

2 x 4 = 8 mEq/L

PaCO2 is increased 20 mmHg above normal.

In respiratory acidosis, compensatory limit is 4 mEq/L ↑ [ HCO3

_ ] per 10 mm Hg ↑PCO2

Comparing # 3 and # 4, pH PaCO2 [HCO3

-]

3. 7.22 60 24

4. 7.33 60 30

Renal compensatory excretion of H+ raised pH up

towards normal level.


-]

5. 7.25 30 16


-]

7.25↓ 30 16

acidosis


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]




-]

7.25 30 ↓ 16

acidosis

respiratory

Not

Skip PCO2 for now, look at bicarb-->Metabolic Acidosis?

Metabolic Acidosis?pH PaCO2 [HCO3

-]

7.25 30 16 ↓

YES

Is there compensation?

Metabolic Acidosis

Metabolic Alkalosis



[HCO3_ ]p

[HCO3_ ]p

PCO2

PCO2

PCO2

PCO2

[HCO3_ ]p

[HCO3_ ]p




-]

7.25 30 ↓ 16

There is compensatory hyperventilation.

Is compensation appropriate?


Acidosis Alkalosis

Metabolic acidosis


MetabolicAlkalosis



Renal compensation


Renal compensation

pH < 7.4

pH > 7.4


_ ] < 22 mEq/L


_ ] < 22 mEq/L

* 1.2 mm Hg ↓ PCO2


*4 mEq/L ↑ [ HCO3_ ]



* 4 mEq/L ↓ [ HCO3_ ]




pH PaCO2 [HCO3-]

7.25 30 16

Compensated metabolic acidosis

[HCO3-] is decreased by 8 mEq/L (24-

16)

8 x 1.2 = 9.6 mm Hg40-10= 30 mmHg

∴

In metabolic acidosis, compensatory limit is 1.2 mm Hg ↓ PCO2

per mEq/L ↓ [ HCO3_ ].

In a man undergoing surgery, it was necessary to aspirate the contents of the upper gastro-intestinal tract. After surgery, the following values were obtained from an arterial blood sample: pH 7.55, PCO2 52 mm Hg and HCO3- 40 mmol/l. What is the underlying disorder

74

pH PaCO2 [HCO3-]

6. 7.55 52 40


75

pH PaCO2 [HCO3-]

6. 7.55 52 40

Alkalosis


76

pH PaCO2 [HCO3-]

6. 7.55 52 40 Metabolic alkalosis


77

pH PaCO2 [HCO3-]

6. 7.55 52 40

Metabolic acidosis with respiratory Compensation


Compensated metabolic alkalosis

[HCO3-] is increased by 16 mEq/L (40-

24)

16 x 0.7 = 11.2 mm Hg

40+11= 51 mmHg

∴

In metabolic alkalosis, compensatory limit is 0.7 mm Hg ↑ PCO2

per mEq/L ↑ [ HCO3_ ].

pH PaCO2 [HCO3-]

7.55 52 40

A person was admitted to hospital in a coma. Analysis of the arterial blood gave the following values: PCO2 16 mm Hg, HCO3- 5 mmol/l and pH 7.1. What is the underlying acid-base disorder?

79

pH PaCO2 [HCO3-]

7. 7.1 16 5


80

pH PaCO2 [HCO3-]

7. 7.1 16 5

Acidosis


81

pH PaCO2 [HCO3-]

7. 7.1 16 5

Metabolic Acidosis


82

pH PaCO2 [HCO3-]

7. 7.1 16 5

Metabolic acidosis with Respiratory compensation


pH PaCO2 [HCO3-]

7. 7.1 16 5

Compensated metabolic acidosis

[HCO3-] is decreased by 19 mEq/L (24-

5)

19 x 1.2 = 22.8 mm Hg

40-23= 17 mmHg

∴

In metabolic acidosis, compensatory limit is 1.2 mm Hg ↓ PCO2

per mEq/L ↓ [ HCO3_ ].

2 yo receiving deep sedation by the adult ED attending who gives him 4 mg morphine, respiratory rate is 6

84

pH PaCO2 [HCO3-]

8. 7.16 70 24

Acidosis


85

pH PaCO2 [HCO3-]

8. 7.16 70 24



86

pH PaCO2 [HCO3-]

8. 7.16 70 24

Compensation? --> No, HCO3 is normal

Uncompensated (acute) respiratory acidosis

35 yo Cystic Fibrosis patient on the Peds floor with end-stage lung disease

87

pH PaCO2 [HCO3-]

9. 7.30 89 38

Acidosis


88

pH PaCO2 [HCO3-]

9. 7.30 89 38



89

pH PaCO2 [HCO3-]

9. 7.30 89 38

Compensation? --> yes, HCO3 is increased


pH PaCO2 [HCO3-]

7.3 89 38

Partially compensated respiratory acidosis

(possibly a mixed disorder)

[HCO3-] is increased 14 mEq/L above normal of

24.

5 x 4 = 20 mEq/L

PaCO2 is increased 49 (~50) mmHg above norm.

In respiratory acidosis, compensatory limit is 4 mEq/L ↑ [ HCO3

_ ] per 10 mm Hg ↑PCO2

References

•Adapted from PATHOPHYSIOLOGY OF ACID-BASE DISORDERS, Patricia J. Metting, Ph.D. Professor Departments of Physiology & Pharmacology and Medicine, University of

Toledo COM, 2011

91

pathophysiology of acid-base disorders tyler paradis md resident anesthesiologist ohsu apom...

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