ABG's (Exam 1) Flashcards by Isaiah Smith

ABG’s give us the best representation of

paCO2

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ABG: Purpose

To assess acid-base status and to determine adequacy of oxygenation and ventilation

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Normal pH

7.35 - 7.45 (balance of H+)

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Normal PaCO2

34-45 mmHg

Respiratory parameter

Carbonic acid dissolves into CO2 and H2O

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Normal HCO3

24-29 mEq/L

Metabolic parameter

THIS IS CALCULATED ON THE ABG

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Primary EVENT

The problem causing the acid imbalance

Hypoventilation - Hyperventilation - Vomiting - Diarrhea

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Primary DISORDER

What RESULTS from the primary event

Respiratory acidosis - metabolic alkalosis - etc

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Compensation Mechanisms

-Physiologic process that adjust the pH back to normal range

If lungs are the problem - the kidneys will compensate

If kidneys are the problem - the lungs will compensate (but not for long)

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General Causes of Imbalance is termed

Metabolic

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Metabolic

HCO3 (bicarbonate) level changes secondary to metabolic alteration (kidneys)

The problem is metabolic in nature

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Respiratory

H2CO3 (carbonic acid) level changes secondary to respiratory

The problems is respiratory nature

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Respiratory acidosis

Respiratory alkalosis

Increase or decrease in CO2

Changes in ventilation

(lung)

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Metabolic acidosis

Metabolic alkalosis

Changes in H+ or bicarbonate ions

(kidney)

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Acid Base Mnemonic

Respiratory
Opposite

Metabolic
Equal

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pH increase : PCO2 decreases

Respiratory alkalosis

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pH decrease : PCO2 Increase

Respiratory acidosis

pH increase : HCO3 increase

Metabolic alkalosis

pH decrease : HCO2 decrease

Metabolic acidosis

Metabolic Alkalosis: ABG

too much bicarb (HCO3) or not enough carbonic acid (H2CO3)

pH > 7.48 (high)
PaCO2 - 35-45 (normal)
HCO3 > 29 (high)

Metabolic Alkalosis: Common Causes

-Taking excess baking soda (increase bicarb)

-Prolonged Vomiting (losing stomach acid)

-NG tube suctioning (losing stomach acid)

-Diuretics (losing hydrogen ions)

Metabolic Alkalosis: Clinical Manifestations

CNS excitability
Dysrhythmias
Tremors
Muscle cramps
Paresthesias
Coma
N/V/D
Resp Depression (hypoventilation) (body trying to hold onto CO2)

H+ moves out of cell to try and increase pH which causes K+ to move into cell thus causing hypokalemia

Respiratory Alkalosis: ABG

H2CO3 (carbonic acid) Deficit in ECF

pH > 7.45 (high)
PaCO2 < 35 (low) (blowing off CO2)
HCO3 24-29 (normal) (kidneys not compensating yet)

What commonly causes Respiratory Alkalosis

Hyperventilation

Body is blowing off a lot of CO2

Respiratory Alkalosis: Common Causes

Hyperventilation (breathing more rapidly)

Increased metabolic demands (fever) (sepsis)

Medications

Acute anxiety and panic attack

PE or lung disease

CNS lesions

Ventilator settings

Respiratory Alkalosis: Clinical Manifestations

CNS excitability Tachypnea Syncope (passing out) Lightheadedness Confusion - blurred vision Paresthesia Hyperactive reflexes Coma

Respiratory Acidosis: Acute and Chronic ABG

H2CO3 (carbonic acid) excess in ecf pH <7.35 (low) PaCO2 > 45 (increase) HCO3 - 24-29 (normal acute) (chronic = kidney compensate = high = ph normal)

Respiratory Acidosis: Common Causes

Hypoventilation Acute = Resp arrest Chronic = COPD / Oversedation Too much CO2 retained (H+)

Respiratory acidosis: Clinical Manifestations

CNS depression Hypoventilation Dyspnea Respiratory distress Shallow respirations (fractures) Tachycardia Arrhythmias Decrease LOC - Coma - Stupor

Respiratory Acidosis: Common Causes

Cardiopulmonary arrest Head injury Narcotics Anesthesia pulmonary disorders Pain Abdominal distension Airway obstruction Chest way deformities Neuromuscular problems (DECREASE BREATHING)

How to tell the difference between acute vs chronic Respiratory Acidosis

Acute the kidneys have not yet compensated so HCO3 will be normal and pH will be acidic Chronic the kidneys have compensated so HCO3 will be high and pH will be more normal

Metabolic acidosis: ABG

HCO3 (bicarbonate) deficit in ECF -excess acids are added or bicarb is lost pH > 7.35 (low) PaCO2 34-45 (normal) HCO3 > 24 (low) pH and Bicarb are both low

Metabolic acidosis: Clinical Manifestations

CNS depression Hypotension Hyperkalemia Kussmaul respirations (DKA)

Metabolic Acidosis: Common Causes

Renal Failure Diabetes (Type 1) (DKA) Lactic acidosis Prolonged diarrhea (loss of HCO3) Starvation (body using fat = ketosis) Shock and cardiac arrest

Respiratory acidosis / alkalosis: Compensation

Kidneys will compensate by either: Conserving (reabsorbed) HCO3 (acidosis correction) Excreting HCO3 (alkalosis correction)

Metabolic Acidosis / Alkalosis: Compnesation

The lungs will compensate by either: Conserving CO2 (hypovent) (alkalosis correction) Excreting CO2 (hypervent) (acidosis) Kidney also attempts to correct