1 Arterial Blood Gasses At the end of this self study the participant will: 1. Correctly identify the following: a. Respiratory acidosis b. Respiratory alkalosis c. Metabolic acidosis d. Metabolic alkalosis See BJH Policy: Arterial Blood Gas Sampling Physician alert levels per BJC
Arterial Blood Gasses. At the end of this self study the participant will: 1. Correctly identify the following: Respiratory acidosis Respiratory alkalosis Metabolic acidosis Metabolic alkalosis See BJH Policy: Arterial Blood Gas Sampling - PowerPoint PPT Presentation
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Arterial Blood Gasses
At the end of this self study the participant will:
1. Correctly identify the following:
a. Respiratory acidosis
b. Respiratory alkalosis
c. Metabolic acidosis
d. Metabolic alkalosis
See BJH Policy: Arterial Blood Gas Sampling
Physician alert levels per BJC Laboratory: (http://www.testcatalog.org/nrr/catalogs/bjc/catalog/)
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• Normal pH: 7.35 to 7.45• For normal metabolism to occur pH must be
maintained in the normal range: • When the pH is below 7.35, blood is acidic. • When the pH is above 7.45, blood is alkalotic. • Physician alert values for blood pH are below 7.2
OR above 7.6– Values outside of that range may interfere with cellular
functioning, and if uncorrected, will lead to death.
pH
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PaCO2 - partial pressure of CO2 • Definition: the amount of carbon dioxide gas dissolved in the
blood• Normal PaCO2 : 35-45 mmHg (torr) • Physician alert value at BJH is 75 mmHg or greater• Carbon Dioxide is acidic
– as PaCO2 , pH levels , (acidic) – as PaCO2 , pH levels , (alkaline)
• Blood carries CO2 to the lungs, where excess CO2 combines with H2O to form carbonic acid (H2CO3). – The level of H2CO3 in blood determines blood pH– H2CO3 triggers the lungs to adjust the rate and depth of
ventilation to stabilize CO2 .
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HCO3 (Bicarb) (Base)
• Normal HCO3 : 22-26 mEq/L • Kidneys excrete or retain bicarbonate (HCO3)
according to pH level. – HCO3 , pH levels : alkaline– HCO3 , pH levels : acidic
• Kidneys may take from hours to days to correct an imbalance.
• Remember: the lungs and kidneys work together.• Goal: maintain blood pH by balancing 1 part acid to
20 parts base.
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PaO2 partial pressure of O2
• Normal PaO2 - 80-105 mmHg • Physician alert value 40 or less• PaO2 (Partial Pressure of Oxygen) amount of oxygen
dissolved in the blood. (The other 97% of oxygen is attached to the hemoglobin) – It primarily measures the effectiveness of the lungs
in pulling oxygen into the blood stream from the atmosphere.
– Critical Threshold <60 mmHg
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PaO2
• Elevated PaO2 levels are associated with:– Increased oxygen levels in the inhaled air – Polycythemia
• Decreased PaO2 levels are associated with:– Decreased oxygen levels in the inhaled air – Anemia – Heart decompensation – Chronic obstructive pulmonary disease – Restrictive pulmonary disease – Hypoventilation
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SaO2: Arterial Oxygen Saturation
• Definition: % of hemoglobin combined with O2 • Normal SaO2 on room air is in excess of 95%.
– deep or rapid breathing can to 98-99%. – Oxygen-enriched air (40% - 100%), can push SaO2 to
100%.• Oxygen Saturation will fall if O2 available:
• Oxygen Saturation will rise if:– Deep or rapid breathing occurs oxygen levels (supplemental O2)
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Summary of ABG Acid/BaseRespiratory Acidosis
Respiratory Alkalosis
Metabolic Acidosis
Metabolic Alkalosis
pH
7.35-7.45
<7.35 >7.45 <7.35 >7.45
CO2
35-45
>45 <35 35-45 35-45
HCO3
22-26
22-26 22-26 <22 >26
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Indications for ABG• Inadequate Ventilation?
– Not awake or breathing too fast, (concern about respiratory muscle fatigue)
• Are there concerns about oxygenation that can’t be addressed with pulse ox?– Carbon Monoxide (carboxyhemoglobinemia)– Methemoglobinemia (e.g., benzocaine intoxication)
• Are there concerns about acid-base balance?– Sepsis, DKA, Poly-drug overdose– Chronic CO2 retention
• Miscellaneous– After intubation– Monitor vent settings– Pre-op baseline