BASIC ARTERIAL BLOOD GAS (ABG) INTERPRETATION

By: Jesus Mario A Lopez Jr., R.T.,R.N.

Common Arterial Blood Gas Puncture Sites

4.bin

Obtaining ABG Puncture Sites

AdultChild (> 24 months)Neonate(< 12 months)1* - Radial A.2* - Brachial A.3* - Femoral A. 4* -Dorsalis Pedis A.5* - Posterior Tibial A. 1* - Radial A.2* - Brachial A.1* Brachial A. 2* Umbilical V.3* Capilliary and Heel Stick samples (opitional)

50.bin

30-40

45-60

90

Radial

Brachial

Femoral

10-20

Dorsalis P. & Posterior T.

Modified Allens Test

Sampling Hazards

Disruption of blood flow (e.g. Hematoma)

Clotting

Bleeding

Vessel spasm

Fistulas

Tissue trauma

Under Anticoagulant Therapy

Poor skin healing (underlying dse.)

Sampling Problems

Air Bubbles

* PaCo2

* Pa02 or

* pH

Improper cooling (> 1 hr.)

* PaCo2

* Pa02

* pH

Too much heparin

*pH

Factors may alter ABG results

Post suctioning

Nebulization (after?)

Movement (Turning)

Medications (I.V.)

Activity/Procedures

Handling of sample

Normal Values:

ParametersRangeAbsoluteMixed VenouspH7.35-7.457.407.31-7.41PaCO235-45 mmHg40 mmHg41-51 mmHgPaO280-100 mmHg95 mmHg37-43 mmHgHCO322-26 mmHg24 mEq/L22-26 mEq/LBE/BD-2 to +2 mEq/L 0 mEq/L-2 to +2 mEq/LO2 Sat %> 95%98%68-75 %

pH - 7.45=Alkalotic

HCO3 - 26mEq/L=Alkalotic

BE/BD - +2 Alkalotic

PaCO2 - > 45mmHg=Acidotic

< 35mmHg=Alkatotic

Organs involved in ABG

Respiratory Component = Lungs PaCo2

- minutes to compensate

Metabolic Component = Kidneys HCO3

- days/weeks to compensate

Primary and Compensatory response for acid-base disorders:

Primary Event Compensatory Response PaCO2 HCO3 PaCO2 HCO3

Arterial Oxygenation Status (PaO2)

* Note for individuals over age of 60 y/o, 1mmHg should be subtracted from the lower limits of mild and moderate hypoxemia for each year over 60 y/o. At any age a PaO2 < 40mmHg indicates severe hypoxemia, and a PaO2 of 100mmHgCorrected oxygenation= 80-100mmHgUncorrected/inadequate oxygenation=

Monitoring of O2 & CO2 status

ABG analysis (Confirmatory!!!)Pulse oximetry (least)EtCO2 monitoring (spot check/transport vent )Capillary gas determination(infants only)Transcutaneous monitoringOxygenation indices

Steps in ABG Interpretation:

Determine the pH

Determine whether respiratory or metabolic in origin

Determine the compensation

Determine the Oxygenation Status

________ _______ _______ ________

4

3

2

1

7.bin

pH= 6.90

PaCO2=70mmHg

PaO2=39mmHg

HCO3= 23mEq/L

BE/BD= -4mEq/L

O2 Sat= 90%

Age: 20 y/o

Fi02: R.A.

Interpretation: Uncompensated Respiratory Acidosis w/ Severe Hypoxemia

ABG: RESPIRATORY ACIDOSIS

Causes (mainly airway obstruction & resp. depression)COPD: Asthma, Bronchiectasis, Bronchitis, EmphysemaAtelectasisBrain traumaHypoventilation Sedatives, narcotics, anesthetics Pulmonary edema

ABG: RESPIRATORY ACIDOSIS

S/Sx RR & depthHA, visual disturbance, restlessness, drowsiness, confusionDiaphoresisCyanosisHyper Kdysrhythmias (VF)

ABG: RESPIRATORY ACIDOSIS

TxSemi-Fowlers, O2, coughingHydration Suction secretionsWOF RR distress, hyper KAntibiotics & other meds as ordered

pH= 7.60

PaCO2=52mmHg

PaO2=77mmHg

HCO3= 28mEq/L

BE/BD= +3mEq/L

O2 Sat= 94%

Age: 35 y/o

Fi02: 50% Simple Face Mask

Interpretation: Partially compensated Respiratory Alkalosis w/ uncorrected oxygenation

ABG: RESPIRATORY ALKALOSIS

Causes (mainly overstimulation of the respiratory system)HyperventilationFeverHypoxiaHysteriaOverventilation by mech vent.Pain Salicylates

ABG: RESPIRATORY ALKALOSIS

S/Sx RR & depth then RRHA, light-headedness, vertigoHypo Ca: paresthesia, tetany, convulsionHypo K

pH= 7.00

PaCO2=40mmHg

PaO2=88mmHg

HCO3= 29mEq/L

BE/BD= -8mEq/L

O2 Sat= 90%

Age: 54y/o

Fi02: 2LPM Via nasal cannula

Interpretation: Uncompensated metabolic acidosis w/ corrected oxygenation

ABG: METABOLIC ACIDOSIS

CausesDM & DKAASA toxicityHigh fat dietInsufficient CHO metabolismMalnutritionRFSevere diarrhea

ABG: METABOLIC ACIDOSIS

S/Sx RR, Kussmauls respirationHA, N/V/diarrheaFruity-smelling breathCNS depressionTwitching, convulsionHyper K

ABG: METABOLIC ACIDOSIS

TxNaHCO3 IVSz precautionFor DKA: NS & Regular Insulin IVFor RF: CHON, calorie diet; dialysis

pH= 7.48

PaCO2= 42mmHg

PaO2= 73mmHg

HCO3= 30mEq/L

BE/BD= +8.8mEq/L

O2 Sat= 96.21%

Age: 10 y/o

Fi02: R.A.

Interpretation: Uncompensated Metabolic Alkalosis w/ mild hypoxemia

ABG: METABOLIC ALKALOSIS

CausesDiureticsExcessive vomiting or GI suctioningHyperaldosteronismExcessive NaHCO3 intakeMassive BT (citrate converted to HCO3)

ABG: METABOLIC ALKALOSIS

S/Sx RR & depthN/V/diarrheaRestlessnessParesthesia, twitchingHypoK, HypoCa HR, dysrhythmias

Case Studies:

1. A 20 y/o female with known DM II entered the ER with Kussmauls breathing and irregular pulse. 02 @ 4Lpm via nasal prong, V/S and ABG were taken.

V/S = RR-25 bpmABG = pH 7.12

CR-108 bpm PaCO2 35mmHg

BP- 100/50 mmHg PaO2- 101mmHg

HCO3- 13 mEq/L

O2 Sat%- 99.0%

Interpretation: Uncompensated metabolic acidosis w/ over corrected oxygenation.

Case Studies:

2., A client recovering from surgery in the post-anesthesia care unit (PACU) is difficult to arouse two hours following surgery. The nurse in the PACU has been administering Morphine Sulfate intravenously to the client for complaints of post-surgical pain. The clients respiratory rate is 7 per minute and demonstrates shallow breathing. The patient does not respond to any stimuli

.

V/S = RR- 8 bpmABG = pH 7.10

CR- 40bpmPaCO2 60mmHg

BP- 50 palpPaO2- 41mmHg

O2 3lpm n.c.HCO3- 29mEq/L

O2 Sat%- 85%

Interpretation: Partially compensated respiratory acidosis w/ moderate hypoxemia.

Case Studies:

3. A two-year-old is admitted to the hospital with a diagnosis of asthma and respiratory distress syndrome. The father of the infant reports to the nurse that he has observed slight tremors and behavioral changes in his child over the past three days. The attending physician orders routine ABGs following an assessment of the ABCs. The ABG results are:

V/S = RR-25 bpmABG = pH 7.40

CR-135 bpmPaCO2 47mmHg

BP- 175/110 mmHgPaO2- 115mmHg

O2 7lpm tusk mask HCO3- 39mEq/L

O2 Sat%- 100.0%

Interpretation: Compensated metabolic alkalosis w/ over corrected oxygenation.