prepared by nlert feb,2015 - twghsnurseunion.orgtwghsnurseunion.org/2015-2016 training...

Prepared by NLERT Feb,2015

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The 6 steps to ABG Interpretation


HomeostatsisHomeostatsisHomeostatsisHomeostatsis

體內平衡又稱恆定狀態或恆定性"The maintenance of a constant internal

environment".

“ All living creature keeping their inside as

constant and stable operating condition as

possible, whatever may be happening on the

outside”


Example homeostatis in human bodyExample homeostatis in human bodyExample homeostatis in human bodyExample homeostatis in human body

�Acid-base (pH) balance, body temperature,

Calcium and Phosphate level, blood glucose, fluid

volume, blood pressure etc.


Importance of acid base (pH) balanceImportance of acid base (pH) balanceImportance of acid base (pH) balanceImportance of acid base (pH) balance

� If the pH changes whether up or

down:

1. protein and enzymes becomes stop

functioning.

2. muscles and nerves becomes

weakening.

3. metabolic activities becomes

impaired.

4. blood pH below 6.9 or above 7.9 would

be life threatening.


Carbonic acid Carbonic acid Carbonic acid Carbonic acid ----Bicarbonate Bicarbonate Bicarbonate Bicarbonate

Buffering SystemBuffering SystemBuffering SystemBuffering System�A major buffer system in the acid-base balance.

�To alter any acid base imbalance thus maintain a

constant plasma pH.

�Base on carbonic acid equilibrium equation and involve

2 systems: lung and kidney


Carbonic acid Carbonic acid Carbonic acid Carbonic acid ----Bicarbonate Bicarbonate Bicarbonate Bicarbonate

Buffering SystemBuffering SystemBuffering SystemBuffering System� The way of 2 systems interact is through the formation of

carbonic acid (H2CO3).

� Movement through the carbonic acid system is tend

maintain a equilibrium status.

� If necessary, H2CO3 can break up to form either H+ and

HCO3 or CO2 and H2O

� The system works in both directions.

� By balancing back and forward, a normal pH is achieved.


Renal mechanisms

�Can eliminate large amounts of acid (H+)

�Excretion or retention of base (HCO3-)

�Can reserve and produce bicarb ions

HCO3 ion + Na ion NaHCO3

�Most effective regulator of pH but slow


Respiratory mechanisms

�Exhalation of carbon dioxide

�Excretion and retention of CO2

�Adjust body pH by changing rate and

depth of breathing


Response to acidosis


Response to alkalosis


Acidosis and alkalosis: Acidosis and alkalosis: Acidosis and alkalosis: Acidosis and alkalosis:

There are two abnormalities of acid-base

balance:

� Acidosis: Too much acid or too little base,

resulting in a decrease in blood pH<7.35

� Alkalosis: Too much base or too little acid,

resulting in an increase in blood pH>7.45

Metabolic or Respiratory Metabolic or Respiratory Metabolic or Respiratory Metabolic or Respiratory

acid base imbalanceacid base imbalanceacid base imbalanceacid base imbalance

�Acidosis and alkalosis are categorized as metabolic

or respiratory

�Depends on their primary cause. 1. Metabolic acidosis and metabolic alkalosis are caused by

an imbalance acids or bases production or excretion by the

kidneys.

2. Respiratory acidosis and respiratory alkalosis are caused

by amount of carbon dioxide exhalation due to lung or

breathing disorders.

Cause of Respiratory AcidosisCause of Respiratory AcidosisCause of Respiratory AcidosisCause of Respiratory Acidosis

�Lung diseases e.g. COPD, asthma or pneumonia.

�Airway obstruction e.g. swelling, sputum retention.

�Drugs (anesthetics, sedatives, and narcotics)

induce respiratory depression.

�Neuromuscular diseases impair breathing effort.

�Chest wall desfunction or deformities.


Cause of Metabolic AcidosisCause of Metabolic AcidosisCause of Metabolic AcidosisCause of Metabolic Acidosis

�DKA (metabolism of amino acid ��ketoacidosis)

�Lactic acidosis (anaerobic metabolism during heavy exercise, hypoxia or CPR)

�Chronic renal failure

�Diarrhea (excreted large amounts of bicarbonate).

�DO: methanol or excessive salicylate drug (aspirin)


Cause of Respiratory AlkalosisCause of Respiratory AlkalosisCause of Respiratory AlkalosisCause of Respiratory Alkalosis

�Hyperventilation (rapid, deep breathing)

�Mechanical overventilation

�Anxiety

�Fever

�Sepsis


Cause of Metabolic AlkalosisCause of Metabolic AlkalosisCause of Metabolic AlkalosisCause of Metabolic Alkalosis

�Loss of H ions from the GI tract (free drain of R/T,

R/D, vomiting, nasal gastric suctioning).

�Diuretics use such as Frusemide.

�Excessive NaHCO3 use.

�Massive blood transfusion (metabolism of

citrate��HCO3)


CompensationCompensationCompensationCompensation�Our body regulates pH by using the opposing

system to balance pH.

�It involves 2 opposing system :

�Respiratory system

�Renal system


CompensationCompensationCompensationCompensation

� If pH is out of balance because of primary respiratory

disorder.

� Renal system will make the corrections of pH.

�If the renal system is the primary cause of pH disorder.

�Respiratory system will make the corrections of pH.

This is called compensation.


Indications of ABGIndications of ABGIndications of ABGIndications of ABG

1. Assess respiratory function: PaO2, PaCO2

2. Assess metabolic status (Acid-Base)

3. Assess any electrolyte imbalance


Factors affecting ABG resultsFactors affecting ABG resultsFactors affecting ABG resultsFactors affecting ABG results

1. Temperature

2. The presence of air bubbles in ABG sample

3. Excessive heparin sodium in the sample

4. Clotted sample

5. Time between taken and analysis

6. Site of sampling (venous, arterial)


pH 7.35-7.45

pCO2 35-45mmHg or

4.7 -6 kPa

pO2 80-100mmHg or

10.3-13.3 kPa

O2 saturation 95-100%

HCO3- 22-26mEq/L

Base Excess + 2

Normal rangeNormal rangeNormal rangeNormal range


TestTestTestTest NormalNormalNormalNormal ↓ ↓ ↓ ↓ ValueValueValueValue ↑ ↑ ↑ ↑ ValueValueValueValue

pHpHpHpH 7.357.357.357.35----7.457.457.457.45 AcidosisAcidosisAcidosisAcidosis AlkalosisAlkalosisAlkalosisAlkalosis

pCO2pCO2pCO2pCO2 35353535----45mmHg45mmHg45mmHg45mmHgOrOrOrOr

4.74.74.74.7----6Kpa6Kpa6Kpa6Kpa

AlkalosisAlkalosisAlkalosisAlkalosis AcidosisAcidosisAcidosisAcidosis

HCO3HCO3HCO3HCO3 22222222----26 26 26 26 mEqmEqmEqmEq/L/L/L/L AcidosisAcidosisAcidosisAcidosis AlkalosisAlkalosisAlkalosisAlkalosis

pO2pO2pO2pO2 80808080----100 mmHg100 mmHg100 mmHg100 mmHg HypoxemiaHypoxemiaHypoxemiaHypoxemia ________________________________

SaO2 SaO2 SaO2 SaO2 95959595----100%100%100%100% HypoxemiaHypoxemiaHypoxemiaHypoxemia ________________________________

↓

↓

↓ ↑

↑

↑


6 Easy Steps to ABG 6 Easy Steps to ABG 6 Easy Steps to ABG 6 Easy Steps to ABG

InterpretationInterpretationInterpretationInterpretation

(1)Is the pH normal?

(2)Is the CO2 normal?

(3)Is the HCO3 normal?

(4)Match the CO2 or HCO3 with the pH?

(Identifying primary cause)

(5)Does the CO2 or HCO3 in the opposite direction

of the pH?

(Compensation)

(6)Are the PaO2 and SaO2 normal?


Step 1: pH analysisStep 1: pH analysisStep 1: pH analysisStep 1: pH analysis

�Normal range of blood pH: 7.35 to Normal range of blood pH: 7.35 to Normal range of blood pH: 7.35 to Normal range of blood pH: 7.35 to

7.457.457.457.45

�pH < 7.35 is acidicpH < 7.35 is acidicpH < 7.35 is acidicpH < 7.35 is acidic

�pH. > 7.45 is alkaloticpH. > 7.45 is alkaloticpH. > 7.45 is alkaloticpH. > 7.45 is alkalotic


Step 2: CO2 analysisStep 2: CO2 analysisStep 2: CO2 analysisStep 2: CO2 analysis

�Normal pCO2 level: 35-45mmHg

�Below 35mmHg or 4.7Kpa is alkalosis

�Above 45mmHg or 6Kpa is acidosis


Step 3: HCO3 analysisStep 3: HCO3 analysisStep 3: HCO3 analysisStep 3: HCO3 analysis

�Normal HCO3 level is 22Normal HCO3 level is 22Normal HCO3 level is 22Normal HCO3 level is 22----26 mEq/L26 mEq/L26 mEq/L26 mEq/L

�Below 22 mEq/L is acidosisBelow 22 mEq/L is acidosisBelow 22 mEq/L is acidosisBelow 22 mEq/L is acidosis

�Above 26 mEq/L is alkalosisAbove 26 mEq/L is alkalosisAbove 26 mEq/L is alkalosisAbove 26 mEq/L is alkalosis


Step 4: Match CO2 and HCO3 Step 4: Match CO2 and HCO3 Step 4: Match CO2 and HCO3 Step 4: Match CO2 and HCO3

with the pH levelwith the pH levelwith the pH levelwith the pH level

�Match either PCO2 and HCO3 with pH level to

determine the primary cause of acid-base

disorder

� If primary acid base disorder caused by

respiratory, CO2 level is opposite to pH level

� If Primary acid base disorder caused by

metabolic, HCO3 level is equal to pH level


MatchingMatchingMatchingMatchingRespiratory (Primary cause)

pH↓PCO2↑ Respiratory acidosis

pH↑PCO2↓ Respiratory Alkalosis

Metabolic (Primary cause)

pH↓HCO3↓Metabolic acidosis

pH↑HCO3↑Metabolic alkalosis


Opposite

Equal

Mixed acid base disorder

� That means more than one primary acid base

disturbance at the same time. (particularly in

critically illness).

For example

COPD patient who develops shock and lactic acidosis

pH↓ CO2 ↑HCO3↓and matched with primary cause

=> Mixed acidosis


Step 5: Does CO2 or HCO3 go to the

opposite direction of pH

(determinate the compensation)

�Either CO2 or HCO3 go to the opposite direction of pH, that means compensation in progress.


Primary system causing imbalance Compensating system

Respiratory (pCO2↑) acidosis Metabolic (HCO3 ↑)

Respiratory (pCO2↓) alkalosis Metabolic (HCO3↓)

Metabolic (HCO3 ↓) acidosis Respiratory (pCO2↓)

Metabolic (HCO3 ↑) Alkalosis Respiratory (pCO2↑)


Respiratory system Respiratory system Respiratory system Respiratory system

compensationcompensationcompensationcompensation

� Respiratory system balances pH by ↑ or ↓ RR to

manipulating the CO2 level.

� Fast and deep breathing “blows off” CO2 in

primary metabolic acidosis.

� Slow and shallow breathing “retains” CO2 in

primary metabolic alkalosis.

The process is fast.


Renal System Renal System Renal System Renal System

CompensationCompensationCompensationCompensation

�Primary respiratory alkalosis:Primary respiratory alkalosis:Primary respiratory alkalosis:Primary respiratory alkalosis:

KidneyKidneyKidneyKidney▶▶▶▶▶▶▶▶▶▶▶▶Excreting more HCO3Excreting more HCO3Excreting more HCO3Excreting more HCO3---- in in in in

urine and retaining more H+ urine and retaining more H+ urine and retaining more H+ urine and retaining more H+

�Primary respiratory acidosis:Primary respiratory acidosis:Primary respiratory acidosis:Primary respiratory acidosis:

KidneyKidneyKidneyKidney▶▶▶▶▶▶▶▶▶▶▶▶Excreting more H+ in urine Excreting more H+ in urine Excreting more H+ in urine Excreting more H+ in urine

and retaining more HCO3and retaining more HCO3and retaining more HCO3and retaining more HCO3----

The process is slow The process is slow The process is slow The process is slow

but more powerful.but more powerful.but more powerful.but more powerful.


Partial/Complete Partial/Complete Partial/Complete Partial/Complete

compensationcompensationcompensationcompensation�Compensation may not always be Compensation may not always be Compensation may not always be Compensation may not always be

complete and time consuming. complete and time consuming. complete and time consuming. complete and time consuming.

� If pH remains abnormal, it is partial If pH remains abnormal, it is partial If pH remains abnormal, it is partial If pH remains abnormal, it is partial

compensation.compensation.compensation.compensation.

� If pH returns to normal range, the If pH returns to normal range, the If pH returns to normal range, the If pH returns to normal range, the

compensation is complete. compensation is complete. compensation is complete. compensation is complete.

NoteNoteNoteNote

Nothing to do = no compensationNothing to do = no compensationNothing to do = no compensationNothing to do = no compensation


Step 6: Analysis pO2 and O2 Step 6: Analysis pO2 and O2 Step 6: Analysis pO2 and O2 Step 6: Analysis pO2 and O2

saturation saturation saturation saturation

�Evaluate the PaO2 and O2 saturation. If

they are below normal there is evidence of

hypoxemia.

�PaO2 (80-100mmHg or 10.3-13.3 kPa).

�SaO2 (95~100%).


ABG quiz

1. Metabolic Acidosis has a low level of

what?

A: PO2

B: CO2

C: Compensated Respiratory Acidosis

D: Bicarbonate (HCO3)


2. pH=7.18 PaCO2=68 HCO3=29

A: Uncompensated Metabolic Acidosis

B: Partly compensated respiratory acidosis

C: Combined Acidosis

D: Uncompensated respiratory Acidosis


3.Decrease HCO3 and decrease pH may

causes what?

A: Uncompensated

B: Increase arterial PO2

C: It will lower the pH

D: Metabolic Acidosis


4.The primary drive to breath comes from

the patient?

A: Acidosis

B: Bicarbonate (HCO3)

C: Uncompensated Metabolic Acidosis

D: CO2 level


5. A high CO2 will impact the pH?

A: Lower the pH value (acidosis)

B: Bicarbonate (HCO3)

C: Increase arterial PO2

D: Metabolic Acidosis


6. pH = 7.56 CO2 = 50 HCO3 = 38

A: Normal

B: Respiratory alkalosis without

compensation

C: Partly compensated metabolic alkalosis

D: Metabolic alkalosis


7. pH = 6.96 CO2 = 71 HCO3 = 16

A: Metabolic alkalosis

B: Normal

C: Mixed acidosis

D: Compensated acidosis


8. Interpret this blood gas

pH=7.50 PaCO2=60 HCO3=38

A: Combined acidosis

B: Partly compensated metabolic Alkalosis

C: Bicarbonate (HCO3)

D: Increase ventilation


9. pH = 7.16 CO2 = 82 HCO3 = 29

A: Metabolic acidosis

B: Partly compensated metabolic alkalosis

C: Respiratory alkalosis

D: Partly compensated respiratory acidosis

Prepared by NLERT FEb,2015

10. pH = 7.50 CO2 = 9 HCO3 = 7

A: Partly compensated respiratory

alkalosis

B: Respiratory alkalosis

C: Metabolic alkalosis

D: Partly compensated metabolic alkalosis


11. pH = 7.75 CO2 = 29 HCO3 = 40

A: Combined acidosis

B: Mixed alkalosis

C: Compensated respiratory acidosis

D: Compensated metabolic alkalosis


12. pH = 7.33 CO2 = 66 HCO3 = 35

A: Compensated respiratory acidosis

B: Metabolic alkalosis

C: Metabolic acidosis

D: Partly compensated respiratory acidosis


13. pH = 6.68 CO2 = 85 HCO3 = 10

A: Combined alkalosis

B: Compensated respiratory alkalosis

C: Mixed acidosis

D: Metabolic respiratory acidosis


14. pH = 7.35 CO2 = 42 HCO3 = 23

A: Combined alkalosis

B: Normal

C: Combined acidosis

D: Partly compensated metabolic acidosis


15. pH = 7.21 CO2 = 60 HCO3 = 24

A: Respiratory acidosis without

compensation

B: Compensated metabolic alkalosis

C: Compensated respiratory acidosis

D: Compensated respiratory alkalosis


16. pH = 7.48 CO2 = 19 HCO3 = 14

A: Normal

B: Respiratory acidosis

C: Compensated metabolic acidosis

D: Partly compensated respiratory

alkalosis


ReferenceReferenceReferenceReference

� Irwin RS & Rippe JM 2011 Irwin and Rippe’s Intensive Care Medicine (7th edition) Lippincott Williams & Wilkins: Philadelphia

� Domino FJ 2013 The 5-Minute Clinical Consult 21st Edition Lippincott Williams & Wilkins: Philadelphia

� Nettina SM 2010 Lippincott Manual of Nursing Practice (9th edition). Lippincott Williams & Wilkins: Philadelphia

� Carpenito-Moyet LJ 2009 Nursing Care Plans and Documentation: Nursing Diagnosis and Collaborative Problems (5th Edition). Lippincott Williams & Wilkins: Philadelphia


prepared by nlert feb,2015 - twghsnurseunion.orgtwghsnurseunion.org/2015-2016 training...

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