ABG analysis; edited for 2022 cohort.pptx

Powerpoint

1. Arterial Blood Gas(ABG) Analysis Medical Surgical Nursing III 8 th August 2024 2022 cohort By. D. Kamalizeni

2. Learning Objectives Describe the components of ABG analysis Describe mechanisms that maintain the normal blood pH Describe steps to ABG analysis Interpret selected ABG values

3. Overview of ABG analysis Essential component/part of diagnosing and managing patient`s oxygenation status and acid-base balance Highly dependent on knowledge of: Genesis of parameters being analyzed

4. Pre- liquisite knowledge base continues.., Normal ranges of such parameters What abnormal parameters are likely to indicate Suggested interventions to resolve such abnormalities When further assessment is indicated

5. Measures of ABG pH Respiratory function(PaCO2, PaO2, SaO2) Metabolic function (Bicarbonate, Base excess) Is compensation occurring? And which way?

6. Measure of pH Deals with measure of acidity/alkalinity of blood Inversely proportion to no of hydrogen ions; the more the hydrogen ions, the lower the pH (acidity) and the fewer the no of hydrogen ions, the higher the pH (alkali)

7. Measure of pH continues…, Measured on a scale from 1 (very acidic) to 14 (very alkalotic ) A liquid with pH of 7 is neutral; neither acidic nor alkalotic Normal pH range for blood is 7.35 – 7.45; which must be maintained for normal cellular functioning

8. Maintenance of the normal blood pH Self-regulated Uses delicate buffer mechanisms: Respiratory response Renal response

9. Buffer mechanisms continues.., (revision) Resp and renal systems together form the physiological buffer systems that control pH by regulating amount of acid or base in the body

10. Respiratory response (revision) Co2 is the normal bi-product of metabolic activity It is carried in blood to the lungs for excretion While in the blood( erythrocytes ), CO2 combine with H2O to form carbonic acid(H2CO3 ) ( write this chemical reaction) This Carbonic acid dissociates into Hydrogen ions and bicarbonate ions: ( write this reaction ) pH will change according to level of H2CO3 in the blood

11. Respiratory response CTs…,, Deviations in blood CO2 triggers the resp syst to either increase or decrease rate & depth of resp until appropriate conc of CO2 is re-established Activation of the resp to compensate for any of such deviations occurs within 1 – 3minutes

12. Renal response To maintain normal ranges of blood pH, kidneys excrete or retain bicarbonate When pH decreases (acidic), kidneys retain bicarbonate (HCO3, as pH rises ( alkalotic ), kidneys excrete HCO3 This response occur from hrs to days following the deviation

13. The common acid-base disorders Respiratory acidosis Caused by accumulation of CO2 in the blood Mostly attributed by conditions that results into hypoventilation like: CNS depression 2 nd to HI, medication Impaired resp muscle functioning Pulmonary disorders like asthma Pain, chest trauma Abdominal distension

14. 2.Respiratory alkalosis Defined as pH greater than 7.45, PaCO2 less than 33 mmHg Caused by any condition that cause hyperventilation like: Anxiety, fear, Pain Increased metabolic demands Medication like resp stimulants

15. 3. Metabolic acidosis Defined with reference to reduced bicarbonate level with pH of less than7.35 Mostly caused by either a deficit of a base in the blood or an excess of acids other than CO2 Mostly caused by: Renal failure DKA Starvation

16. 4. Metabolic alkalosis Defined with reference to increased bicarbonate levels with pH greater than 7.45 May result from ingestion of more antacids, excess use of bicarbonate Usually iatrogenic in nature in hospitalized patients; (complications from related therapeutic interventions) like gastric suction

17. Components of ABGs pH Measurement of acidity or alkalinity based on hydrogen ions present Normal range is 7.35 – 7.45 PaO2 O2 that is dissolved in blood Normal range is 80 -100 mm Hg SaO2 Arterial O2 saturation; ranging from 95% to 100%

18. Components of ABGs HCO3 Amount of bicarbonate in the blood Normal ranges: 22 to 26 mEq / litre PaCO2 Amount of CO2 dissolved in the arterial blood Ranges from 35 to 45 mm Hg

19. Steps to ABG analysis/interpretation Evaluates both oxygenation status and acid-base balance; however each represent separate conditions Acid-base evaluation requires a focus on three of the reported; pH, PaCO2, HCO3 . Step one Assess pH to determine if blood is within normal range; alkalotic or acidic

20. Interpretation of ABG CTs…, Step 2 If blood is alkalotic or acidic; then determine if it is caused by a respiratory or metabolic problem With resp problem, if pH decreases below 7.35 then PaCO2 should rise and if pH rises above 7.45, PaCO2 should fall (explain) Therefore, compare pH and PaCO2 values; if pH and PaCO2 are moving in opposite direction, then the problem is respiratory in nature

21. Interpretation of ABG CTs…, Step 3 Finally assess HCO3 value With metabolic problem, as pH rises, the HCO3 should rise and as pH reduces, HCO3 should also reduce. So at this step, compare the 2 values(pH and HCO3); If both are moving in same direction, then problem is primarily metabolic in nature

22. Summary of the relationships btn pH, PaCO2 and HCO3 pH PaCO2 HCO3 EXPLAIN Respiratory acidosis Decreasing increasing normal Respiratory alkalosis Increasing decreasing normal Metabolic acidosis Decreasing Normal decreasing Metabolic alkalosis increasing normal increasing

23. Example Nabanda asthmatic patient has the following arterial blood gas values: pH = 7.22 PaCO2 = 55 mm Hg HCO3 = 25 mEq / litre Analyse the above values and institute appropriate interventions for Nabanda

24. Analysis of Nabanda`s ABG Step 1 PH of 7. 22 is low; decreasing; (normal is 7.35-7.45), therefore we have acidosis Step 2 PaCo2 of 55mmHg is high (normal is 35-45 mmHg) and moving in opposite direction with pH. Step 3 HCO3 is 25 mEq /l which is normal( normal is22 -26mEq/l); Therefore, acidosis is present(low pH); PaCO2 is high reflecting a resp problem which is respiratory acidosis

25. Management of Naphiri basing on the analysed ABG Plan Improve ventilation status by: providing O2 (Mechanical ventilation) pulmonary toilet, administration of bronchodilators & steroids

26. Scenarios for self practice Analyse the following ABGs and manage accordingly: pH = 7.50; PaCO2 = 42 mmHg; HCO3 = 33mEq/l pH = 7.32; PaCO2 =32 mmHg; HCO3 = 18 mEq /l pH = 7.35; PaCO2 = 48 mmHg; HCO3= 28 mEq /l

27. ADDITIONAL INFORMATION ON ABG (JUST TO KNOW) Compensation in acid-base imbalance

28. Compensation in acid-base imbalance Occurs in acid-base imbalance that exists over a long time The body tries to overcome either a resp or metabolic dysfunction Done in attempt to return the pH into the normal range Patient can be: Uncompensated: (pH outside the normal range) Partially compensated( as above) Fully compensated(pH within normal, other parameters may still remain abnormal)

29. Fully compensated states pH PaCO2 HCO3 Respiratory acidosis Normal but less than 7.40 Increasing increasing Respiratory alkalosis Normal, but more than 7.40 decreasing decreasing Metabolic acidosis Normal but less than 7.40 decreasing decreasing Metabolic alkalosis Normal but more than 7.40 increasing increasing

30. Partially compensated states pH PaCO2 HCOH Respiratory acidosis Decreasing increasing increasing Respiratory alkalosis Increasing decreasing decreasing Metabolic acidosis Decreasing decreasing decreasing Metabolic alkalosis increasing increasing increasing

31. Differences btn partially and fully compensated states In compensated states, pH falls either on the low or high side of neutral Noting where the pH falls within the normal range helps in determining whether the original acid-base imbalance was acidosis or alkalosis

32. Example Patient with kidney problem has the following ABG values: pH = 7.32 PaCO2 = 32 HCO3 = 18

33. Interpretation pH(7.32) is low, therefore we have acidosis PaCO2 is low(32). (Normally we would expect the 2 values (pH and PaCO2) to move in opposite direction) pH and PaCO2 moving in same direction reflects that the acid base disorder is primarily metabolic Low PaCO2 & low pH reflects that the lungs are compensating to blow off CO2 (both moving in same direction) Therefore this ABG denotes a partially compensated metabolic acidosis (pH, PaCO2 and HCO values decreasing; refer to table above)