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Arterial Blood Gas Interpretation for Nurses: Understanding pH, PO2, PCO2, HCO3, and BE, Slides of Nursing

Nebraska Methodist CollegeNursing

An overview of Arterial Blood Gas (ABG) interpretation for nurses, focusing on the essential components pH, PO2, PCO2, HCO3, and BE. It explains the normal ranges, the role of acid-base regulation through respiratory and renal systems, and case studies to help identify acidotic or alkalotic states.

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4/27/2015
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Arterial Blood Gas
Interpretation for the
Bedside Nurse
Andrea L. Briscoe, MSN, RN, CCRN
AnMed Health
Objectives
• Identify three essential components of the
ABG series
• Relate ABG results to potential
interventions in specific patient scenarios
Introduction
•Arterial Blood Gas (ABG) Overview
– Drawn from arterial source- radial (most often
used), brachial, and femoral
– Helpful in identifying respiratory/oxygenation
deficiencies and metabolic/acid-base balance
deficiencies
– Critical care patients may have arterial line
placed for frequent draws
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Partial preview of the text

Download Arterial Blood Gas Interpretation for Nurses: Understanding pH, PO2, PCO2, HCO3, and BE and more Slides Nursing in PDF only on Docsity!

Arterial Blood Gas

Interpretation for the

Bedside Nurse

Andrea L. Briscoe, MSN, RN, CCRN

AnMed Health

Objectives

  • Identify three essential components of the

ABG series

  • Relate ABG results to potential

interventions in specific patient scenarios

Introduction

  • A rterial B lood G as ( ABG ) Overview
    • Drawn from arterial source- radial (most often

used), brachial, and femoral

  • Helpful in identifying respiratory/oxygenation

deficiencies and metabolic/acid-base balance

deficiencies

  • Critical care patients may have arterial line

placed for frequent draws

Acid/Base Regulation Review

  • Buffering
    • Normal body mechanism that occurs rapidly in response to acid-base disturbances to prevent changes in H+ - Respiratory- regulates the excretion or retention of carbonic acid. Fastresponse- usually within minutes but response is weak. - If pH decreases= the rate and depth ofbreathing increases - If pH increase= the rate and depth ofbreathing decreases - Renal System- regulates the excretion and retention of bicarb (HCO3). Slower response – usually about 48 hours but a powerful result. - If pH decreases= the kidney will retainHCO - If pH increases= the kidney will releaseHCO

Knowledge Gap

  • Youssef, et al. (2013) indicated gap between

nurses’ knowledge and practices as compared

to the evident based guidelines of American

Association of Respiratory Care in

management of ABG sampling

  • Recommendations were to enrich nursing

knowledge and practices related to:

  • ABG indications, sampling practices, complications

of sampling and…

  • Interpretation of Parameters

ABG COMPONENTS

pH PO 2 SaO 2 PCO 2 HCO 3 BE

PCO 2

  • Partial pressure of

carbon dioxide

dissolved in arterial

blood.

Normal is 35-45 mmHg

HCO 3

  • The calculated value

of bicarbonate in the

bloodstream.

Normal is 22-26 mmol/L

Base Excess(BE)/Deficit

  • The base

excess/deficit

indicates the amount

of excess or

insufficient level of

bicarbonate in the

system.

  • Negative base level is reported as a deficit and associated with metabolic acidosis
  • Positive base level is reported as excess and associated with metabolic alkalosis

Normal is -2 to +2 mEq/L

Normal ABG values

  • pH 7.35-7.
  • PCO 2 35-45 mmHg
  • PO 2 80 – 100 mmHg
  • HCO 3 22-26 mmol/L
  • BE -2 to +
  • SaO 2 >95%

ABG Interpretation

  • The only two ways an

acidotic state can exist

is from too much CO 2

or too little HCO 3.

  • The only two ways an

alkalotic state can

exist is too little CO 2

or too much HCO 3.

Acid Base pH 7.35 7. CO2 45 35 HCO3 22 26

So the key is finding what KIND of acidotic or alkalotic state the patient is in: respiratory or metabolic! Figuring out what kind will then guide your treatment!

Interpretation Methods

1. Stepwise approach

2. “Tic-tac-toe” method

3. Color Method

  1. Color Method
  • Blue= base
  • Red= acid
  • Black= neutral

Practice ABG:

pH 7.24, PCO 2 75 , HCO 3 28

Now find the parameter color that

matches the pH…

Respiratory Acidosis

ABG ALTERATIONS

Case Study #

  • A 55 year old male is found down in a hospital waiting area. EMS is called and upon arrival, the patient is found to have an oxygen saturation of 88% and pinpoint pupils. He is brought to your ER where a room air arterial blood gas is performed.
  • Results: pH 7.25 PCO 2 60 PO 2 65 HCO 3 26
  • Acid-base status: _____________?

Respiratory Acidosis

  • Hypoventilation caused by any of the following:
    • COPD, Sleep apnea, or other lung diseases that result

in decreased excretion of CO 2

  • Over-sedation, head trauma, anesthesia, and drug

overdose

  • Neuromuscular disorders like Guillian-Barrè

Pneumothorax, flail chest or other chest wall trauma

interfering with breathing mechanics

  • Inappropriate ventilator settings
  • Treatment: Improvement of ventilation
  • Supplemental O 2 , Administration of reversal agents,

change in ventilator settings

↓pH + ↑CO 2

Case Study #

  • A 72 year old female presents with 2 days of fever, dyspnea, and productive cough. Her room air oxygen saturation is 85% and a room air ABG is obtained while waiting for portable chest X-ray.
  • Results: pH 7.54 PCO 2 25 PO 2 65 HCO 3 22
  • Acid-base status: _____________?

Respiratory Alkalosis

  • Excess CO 2 exhaled (hyperventilation)

caused by any of the following:

  • Anxiety/nervousness
  • Hypoxemia or interstitial lung disease
  • Pulmonary embolus, pulmonary edema
  • Bacteremia (sepsis), liver disease, or fever
  • Treatment:
  • Treat underlying cause
  • Slow respiratory rate

↑pH + ↓CO 2

Metabolic Alkalosis

  • Elevated bicarbonate level related to:
    • Chloride depletion- vomiting, prolonged NG suctioning, diuretic use
    • Hypokalemic alkalosis caused by the kidneys' response to an extreme lack or loss of potassium, which can occur when people take certain diuretic medications.
    • Excessive alkali intake, such as antacid abuse, massive blood transfusion containing citrate
  • Treatment:
    • Treat underlying cause
    • Administration of potassium/chloride replacement along with IV fluid administration

↑pH + ↑ HCO 3

Acid/Base Mnemonic

(ROME)

Respiratory

Opposite

↓pH + ↑CO 2 Acidosis ↑pH + ↓CO 2 Alkalosis

Metabolic

Equal

↓pH + ↓ HCO 3 Acidosis ↑pH + ↑ HCO 3 Alkalosis

R

O

M

E

Acid-Base Compensation

• Respiratory disturbances will result in

kidney compensation:

– Resp Acidosis

  • Increase acid excretion
  • Increase bicarb reabsorption
    • Slow process

– Resp Alkalosis

  • Increase bicarb excretion
    • Slow process

Acid-Base Compensation Cont.

  • Metabolic disturbances result in pulmonary

compensation:

  • Metabolic Acidosis
    • Hyperventilation to decrease PCO
      • Rapid compensation!
  • Metabolic Alkalosis
    • Hypoventilation
      • Rapid compensation

ABGs – Interpreting

Compensation

  • pH of 7.40 is used as “normal” when BOTH the pCO2 and HCO3 are abnormal.
  • 7.35 – 7.
    • So, 7.38 is now considered acidosis. In order to determine if the abnormality is due to the kidneys (metabolic) or lungs (respiratory) find the 2 matching values.
    • The match reveals the method of compensation.

High pH Low pH Alkalosis Acidosis High PaCO

Low PaCO

High PaCO

Low PaCO Metabolic Respiratory Respiratory Metabolic

Ex. pH 7.38 (7.40) Acidosis PaCO2 56 (35-45) Acidosis- lungs HCO3 35 (22-26) Alkalosis

Compensated Respiratory Acidosis

Using Technology in

Interpretation

  • Graphical ABG visualization
    • Shown improvement in accuracy of identification
    • Decreased response times when using graphical visualization
    • “Visualization may help nurses during high-stress situations when decisions must be made quickly” (Doig, 2011)

  • • pH 7.
  • • pCO
  • • pO
  • • HCO
  • • BE

  • • pH 7.
  • • pCO
  • • pO
  • • HCO
  • • BE -

  • • pH 7.
  • • pCO
  • • pO
  • • HCO
  • • BE -

  • pH 7.
  • pCO 2 25
  • pO 2 60
  • HCO 3 22
  • BE -

  • pH 7.
  • pCO 2 33
  • pO 2 55
  • HCO 3 18
  • BE -

Answers

1. Metabolic alkalosis

2. Metabolic acidosis

3. Respiratory acidosis

4. Compensated respiratory alkalosis

5. Compensated metabolic acidosis