L9: ABGs Flashcards by Jeri Sheldon (AZ PA Mast 20)

Q

What’s an Arterial Blood Gas?

A

used to detect and monitor indices of: oxygenation, ventilation, acid-base balance
→ also quantify: carboxyhemoglobin, methemoglobin

Procedure: draw blood from an artery→ usually radial (+/- brachial, femoral) with an anticoagulant→ place on ice→ analysis in lab→ results in 5-15 minutes

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Q

Normal pH

A

7.35-7.45 (use 7.4)

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Q

Normal pO2

A

80-100 mmHg

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Q

Normal O2 saturation

A

> 95

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Q

Normal pCO2

A

35-45 mmHg

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Q

Normal HCO3

A

22-26 mmol/L

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Q

Is oxygenation/pO2 used to determine acid-base conditions?

A

NO

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Q

Why bother with pO2?

A

More reliable than pulse ox

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Q

Acidemia

A

pH<7.35

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Q

Alkalemia

A

pH>7.45

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Q

In a mixed disorder

A

pCO2 and HCO3 move in opposite directions

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Q

High anion gap metabolic acidosis

A

“MUDPILES”
Methanol
Uremia
Diabetic ketoacidosis
Propylene glycol
Iron/Isoniazid
Lactate (lactic acidosis)
Ethanol/Ethylene glycol
Salicylates (ASA)/Starvation

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Q

General rules for acid-base disorders

A

It is only possible to have one respiratory disorder at a time, but 2 metabolic disorders can be present at once

Normal pH does not mean there is not an acid-base disorder: could have acidosis+alkalosis

Low bicarb is usually pathologic

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Q

MUDPILES: M

A

Methanol

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Q

MUDPILES: U

A

Uremia

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Q

MUDPILES: D

A

Diabetic ketoacidosis

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Q

MUDPILES: P

A

Propylene glycol

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Q

MUDPILES: I (2)

A

Iron/Isoniazid

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Q

MUDPILES: L

A

Lactate (lactic acidosis)

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Q

MUDPILES: E (2)

A

Ethanol/Ethylene glycol

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Q

MUDPILES: S (2)

A

Salicylates (ASA)/Starvation

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Q

Non anion gap metabolic acidosis is caused by (3)

A

GI bicarb loss
Renal bicarb loss
Hyperchloremia

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Q

Treat metabolic acidosis:

A

Treat underlying cause +/- sodium bicarbonate (immediate period), allow for normal respiratory compensation

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Q

Hyperchloremia is due to

A

due to normal saline resuscitation

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Renal bicarb loss is due to

Early renal failure Renal tubular acidosis Carbonic anhydrase inhibitors (acetazolamide) Aldosterone inhibitors (spironolactone)

GI bicarb loss is due to

Diarrhea GI fistulas Utererosigmoidostomy

Effects of vomiting vs diarrhea

Vomiting: lose acid= metabolic alkalosis Diarrhea: lose bicarb= metabolic acidosis

Urine chloride <25= chloride/fluid responsive metabolic alkalosis is caused by

GI losses: vomiting, NG suction Diuretics→ contraction alkalosis Cystic fibrosis Treat with fluids

Urine chloride >25= non-chloride responsive metabolic alkalosis is caused by

``` Barter’s syndrome Cushing’s Hyperaldosteronism Potassium depletion Citrate toxicity→ massive blood transfusion protocol Chronic diuretics Renin secreting tumor Treat underlying cause +/- potassium ```

Hyperchloremia

Non-anion gap metabolic acidosis

Diarrhea

Non-anion gap metabolic acidosis

Cushing’s

non-chloride responsive metabolic alkalosis

Hyperaldosteronism

non-chloride responsive metabolic alkalosis

Diabetic ketoacidosis

High anion gap metabolic acidosis

Potassium depletion

non-chloride responsive metabolic alkalosis

Citrate toxicity

non-chloride responsive metabolic alkalosis

Ethanol

High anion gap metabolic acidosis

Diuretics

chloride/fluid responsive metabolic alkalosis | contraction alkalosis

Renin secreting tumor

non-chloride responsive metabolic alkalosis

Chronic diuretics

non-chloride responsive metabolic alkalosis

Barter’s syndrome

non-chloride responsive metabolic alkalosis

Methanol

High anion gap metabolic acidosis

Ethylene glycol

High anion gap metabolic acidosis

Isoniazid

High anion gap metabolic acidosis

Uremia

High anion gap metabolic acidosis

Treatment for chloride/fluid responsive metabolic alkalosis

Fluids

Cystic fibrosis

chloride/fluid responsive metabolic alkalosis

Aldosterone inhibitors (spironolactone)

Non-anion gap metabolic acidosis

non-chloride responsive metabolic alkalosis treatment

Treat underlying cause +/- potassium

Carbonic anhydrase inhibitors (acetazolamide)

Non-anion gap metabolic acidosis

Renal tubular acidosis

Non-gap metabolic acidosis

Carbonic anhydrase inhibitors (acetazolamide)

Non-anion gap metabolic acidosis

Respiratory acidosis

poor ventilation causing accumulation of CO2

Causes of Respiratory acidosis

Acute airway obstruction: foreign body, tumor, laryngospasm/bronchospasm Lung disease: severe pneumonia/PE/COPD exacerbation, pulmonary edema, pulmonary fibrosis CNS depression: narcotics, CNS event, trauma, central sleep apnea Neuromuscular disorder: Guillain-Barre, Myasthenia Gravis, Brain stem/spinal cord injury, Impaired lung motion Inappropriate mechanical ventilation settings

Respiratory alkalosis

excess elimination of CO2 from the lungs→ pCO2<35 lightheadedness, palpitations, tachypnea, +/- paresthesias

Causes of Respiratory alkalosis

``` Hyperventilation Compensatory mechanism in sepsis Anxiety, pain CNS: neurogenic hyperventilation Salicylate overdose Pregnancy High altitude, Hypoxemia Hepatic encephalopathy ```

Hyperventilation

Respiratory alkalosis

Acute airway obstruction: foreign body, tumor, laryngospasm/bronchospasm

Respiratory acidosis

Compensatory mechanism in sepsis

Hyperventilation causing Respiratory alkalosis

Inappropriate mechanical ventilation settings

Respiratory acidosis

CNS depression: narcotics, CNS event, trauma, central sleep apnea

Respiratory acidosis

Anxiety, pain

causes Hyperventilation causing Respiratory alkalosis

Impaired lung motion

Respiratory acidosis

CNS: neurogenic hyperventilation

Respiratory alkalosis

Neuromuscular disorder: Guillain-Barre, Myasthenia Gravis, Brain stem/spinal cord injury

Respiratory acidosis

Lung disease: severe pneumonia/PE/COPD exacerbation, pulmonary edema, pulmonary fibrosis

Respiratory acidosis

Salicylate overdose

causes Hyperventilation causing Respiratory alkalosis

High altitude, Hypoxemia

causes Hyperventilation causing Respiratory alkalosis

Hepatic encephalopathy

causes Hyperventilation causing Respiratory alkalosis

Pregnancy

causes Hyperventilation causing Respiratory alkalosis

Pregnancy

causes Hyperventilation causing Respiratory alkalosis

Treat respiratory acidosis

Treat underlying cause, respiratory support (BiPAP) | Differentiate from chronic acidosis→ more stable (COPD) especially if with good compensation, won’t need BiPAP

Treat respiratory alkalosis

Treat underlying cause