ABG Interpretation Julie Perkins RRTNPS LPCH Respiratory Care

ABG Interpretation Julie Perkins RRT-NPS LPCH Respiratory Care

p. H Normal p. H is 7. 35 -7. 45 ¡ Value <7. 35 is acidotic ¡ Value >7. 45 is alkalotic ¡ Acidosis & Alkalosis can be caused by a problem with the respiratory system or a metabolic cause ¡ Can also have combined respiratory/metabolic states ¡

Is it Respiratory or Metabolic? 1. Respiratory Acidosis ¡ Increased p. CO 2 >50 2. Respiratory Alkalosis ¡ Decreased p. CO 2<30 3. Metabolic Acidosis ¡ 4. Metabolic Alkalosis ¡ Decreased HCO 3 <18 Increased HCO 3 >30

Compensated or Uncompensated—what does this mean? 1. Evaluate p. H—is it normal? Yes 2. Next evaluate p. CO 2 & HCO 3 1. p. H normal + increased p. CO 2 + increased HCO 3 = compensated respiratory acidosis 2. p. H normal + decreased HCO 3 + decreased p. CO 2 = compensated metabolic acidosis

Compensated vs. Uncompensated 1. 2. 3. Is p. H normal? No Acidotic vs. Alkalotic Respiratory vs. Metabolic 1. 2. 3. 4. p. H<7. 30 + p. CO 2>50 + normal HCO 3 uncompensated respiratory acidosis p. H<7. 30 + HCO 3<18 + normal p. CO 2 uncompensated metabolic acidosis p. H>7. 50 + p. CO 2<30 + normal HCO 3 uncompensated respiratory alkalosis p. H>7. 50 + HCO 3>30 + normal p. CO 2 uncompensated metabolic alkalosis = =

Causes of Acidosis ¡ Respiratory l l Hypoventilation Impaired gas exchange ¡ Metabolic l l l Ketoacidosis ¡ Diabetes Renal Tubular Acidosis ¡ Renal Failure Lactic Acidosis ¡ Decreased perfusion ¡ Severe hypoxemia

Causes of Alkalosis ¡ Respiratory l Hyperventilation due to: ¡ Hypoxemia ¡ Metabolic acidosis ¡ Neurologic l l l Lesions Trauma Infection ¡ Metabolic l Hypokalemia l Gastric suction or vomiting l Hypochloremia

Assessing Oxygenation Normal value for arterial blood gas 80 -100 mm. Hg ¡ Normal value for venous blood gas 40 mm. Hg ¡ Normal Sa. O 2 ¡ l l Arterial: 97% Venous: 75%

Important points for assessing tissue oxygenation This is the O 2 that’s really available at the tissue level. ¡ Is the THb normal? ¡ l ¡ Low THb means the ability of the blood to carry the O 2 to the tissues is decreased Is perfusion normal? l Low perfusion means the blood isn’t even getting to the tissues

Let’s Practice

12 year old diabetic presents with Kussmaul breathing p. H : ¡ p. CO 2: ¡ p. O 2: ¡ HCO 3: ¡ BE: ¡ l 7. 05 12 mm. Hg 108 mm. Hg 5 m. Eq/L -30 m. Eq/L Severe partly compensated metabolic acidosis without hypoxemia due to ketoacidosis

17 year old w/severe kyphoscoliosis, admitted for pneumonia p. H: ¡ p. CO 2: ¡ p. O 2: ¡ HCO 3: ¡ BE : ¡ l 7. 37 25 mm. Hg 60 mm. Hg 14 m. Eq/L -7 m. Eq/L Compensated respiratory alkalosis due to chronic hyperventilation secondary to hypoxia

9 year old w/hx of asthma, audibly wheezing x 1 week, has not slept in 2 nights; presents sitting up and using accessory muscles to breath w/audible wheezes p. H: ¡ p. CO 2: ¡ p. O 2 ¡ HCO 3: ¡ BE: ¡ l 7. 51 25 mm. Hg 35 mm. Hg 22 m. Eq/L -2 m. Eq/L Uncompensated respiratory alkalosis with severe hypoxia due to asthma exacerbation

7 year old post op presenting with chills, fever and hypotension p. H: ¡ p. CO 2: ¡ p. O 2: ¡ HCO 3: ¡ BE: ¡ l 7. 25 32 mm. Hg 55 mm. Hg 10 m. Eq/L -15 m. Eq/L Uncompensated metabolic acidosis due to low perfusion state and hypoxia causing increased lactic acid