Presentation1 arteriAL BLOOD GAS ANA.pptx

this is a comprehensive ppt about abg

1. Arterial blood gas analysis

2. Buffer System

3. Acid base disorder An  acid base disorder  is a change in the normal value of extracellular pH that may result when renal or respiratory function is abnormal or when an acid or base load overwhelms excretory capacity.   Normal acid base values pH pCO2 HCO 3 - Range 7.35- 7.45 35-45 22-26 Optimal Value 7.4 40 24

4. Acid base disorder Clinical disturbances of acid base metabolism classically are defined in terms of the  HCO3-  /CO2  buffer system. Acidosis –  process that increases [H+] by increasing PCO2 or by reducing [HCO3-] decrease in the blood pH below normal range Alkalosis –  process that reduces [H+] by reducing PCO2 or by increasing [HCO3-]   Elevation in blood pH above the normal range

5. Respiratory Acid base disorder Respiratory acid-base disorders are those abnormalities in acid-base equilibrium initiated by a change in the arterial carbon dioxide tension (PaCO 2 )--the respiratory determinant of acidity in the following equation: Henderson Hasselbalch equation:   pH = 6.1 + log [HCO3-]/ 0.03 PCO2 Kassirer-Bleich equation:    [H+] = 24 × PCO2 / [HCO3-]

6. Respiratory Acid base disorder There are two respiratory acid-base disorders: respiratory acidosis and respiratory alkalosis.

7. Respiratory Acidosis Respiratory acidosis is the acid-base disturbance initiated by an increase in PaCO 2 . An increase in arterial pCO 2 can occur by one of three possible mechanisms: Presence of excess CO 2 in the inspired gas Decreased alveolar ventilation Increased production of CO 2 by the body

8. Respiratory Acidosis In acute respiratory acidosis , the Pa CO 2 is elevated above the upper limit of the reference range ( over 45 mm Hg) with an accompanying acidemia (pH <7.36). In chronic respiratory acidosis , the Pa CO 2 is elevated above the upper limit of the reference range, with a normal or near-normal blood pH secondary to renal compensation and an elevated serum bicarbonate (HCO 3 − >30 mm Hg ).

9. Respiratory Alkalosis Respiratory alkalosis is the acid-base disturbance initiated by a reduction in PaCO 2 . This occurs when there is excessive loss of CO 2 by alveolar hyperventilation. As a result, partial pressure of CO 2 and H + conc. falls

10. Metabolic acidosis Definition Metabolic acidosis is defined as a pathologic process that, when unopposed, increases the concentration of hydrogen ions in the body and reduces the HCO 3 concentration Metabolic acidosis can be produced by three major mechanisms. Increased acid generation Loss of bicarbonate Diminished renal acid excretion

11. Metabolic acidosis Acidosis due to Increased acid generation or poor acid excretion results in High anion gap metabolic acidosis and rest causes normal anion gap metabolic acidosis

12. Metabolic alkalosis Introduction: Metabolic alkalosis is a disorder with elevated serum bicarbonate, Elevated serum bicarbonate results from several mechanisms: Intracellular shift of hydrogen ions; Gastrointestinal loss of hydrogen ions; Excessive renal hydrogen ion loss; Administration and retention of bicarbonate ions; Volume contraction around a constant amount of extracellular bicarbonate (contraction alkalosis)

13. 5 Steps for Successful Blood Gas Analysis

14. Is this ABG authentic ? Henderson- Hasselbalch equation pH = 6.1 + log HCO 3 - 0.03 x PCO 2 pH expected = pH measured = ABG is authentic [H+] meq /l = 24 X (PCO 2 / HCO 3 ) H + ion pH 100 7.00 79 7.10 63 7.20 50 7.30 45 7.35 40 7.40 35 7.45 32 7.50 25 7.60

15. ACIDEMIA or ALKALEMIA? pH < 7.35  acidemia pH > 7.45  alkalemia This is  usually  the primary disorder An acidosis or alkalosis may be present even if the pH is in the normal range (7.35 – 7.45)

16. RESPIRATORY or METABOLIC? IS PRIMARY DISTURBANCE RESPIRATORY OR METABOLIC? pH HCO 3 or pH HCO 3 METABOLIC pH PCO 2 or pH PCO 2 RESPIRATORY RULE- If either the pH or PCO 2 is Normal, there might be mixed metabolic and respiratory acid base disorder.

17. If Respiratory – ACUTE or CHRONIC? Acute respiratory disorder - ∆pH (e-acute) = 0.008x ∆Pco 2 Chronic respiratory disorder - ∆pH (e-chronic) = 0.003x ∆pCO 2 .08 change in pH ( Acute ) .03 change in pH ( Chronic ) 10 mm Change PaCO 2 =

18. Is COMPENSATION adequate? Usually, compensation does  not  return the pH to normal (7.35 – 7.45). If the observed compensation is not the expected compensation, it is likely that more than one acid-base disorder is present.