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ATERIAL BLOOD GASES

ATERIAL BLOOD GASES. Dr Sadia Haroon Respiratory module Ist year MBBS 2019. Acid-Base Balance. Cells need steady balance between acids and bases Normal acid - base balance: 1:20 One part acid (CO 2 ): 20 parts base ( HCO 3 - ) => perfect pH of 7.40

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ATERIAL BLOOD GASES

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  1. ATERIALBLOOD GASES Dr Sadia Haroon Respiratory module Ist year MBBS 2019

  2. Acid-Base Balance • Cells need steady balance between acids and bases • Normal acid - base balance: 1:20 One part acid (CO2): 20 parts base (HCO3-) => perfect pH of 7.40 • Consider CO2 an acid b/c it results in an acid when dissolved in blood: CO2 + H2O ↔ H2CO3↔ HCO3- + H+

  3. Acid-Base Balance • Acid gain or base loss => Acidosis • (pH < 7.40) • Gain base or lose acids => Alkalosis • (ph > 7.40)

  4. Regulation of Acid-Base Balance • Regulatory mechanisms are very sensitive to small changes in pH • Buffers • Respiratory System • Renal System

  5. Regulation of Acid-Base Status: Buffers • Immediately combine with excess acid to form substances that do not greatly affect pH. • Bicarbonate (HCO3-) • Most important buffer • Absorption, excretion, production regulated by kidney • Other buffers: Phosphate, Ammonium, Protein

  6. Regulation of Acid-Base Status: Respiratory System • Increased CO2 or H+ levels => stimulates respiratory => increased ventilation => blows off (exhales) CO2=> eliminating excess acid. If acidotic • Hyperventilation => CO2 eliminated => improvement in acidotic state • If alkalotic (low CO2 or H+): • hypoventilation => CO2 retained => improvement in alkalotic state • Quick response: within 1-2 min of pH imbalance

  7. Regulation of Acid-Base Status: Renal System • Kidneys conserve and/or eliminate H+ and HCO3- in response to abnormal pH • If acidotic => eliminate H+ (acid) and retain HCO3- (base) in effort to normalize pH • If alkalotic => Eliminate HCO3- (base) in effort to normalize pH • Response to abnormal pH is slow (hours to days)

  8. The major function of the pulmonary system (lungs and pulmonary circulation) is to deliver oxygen to cells and remove carbon dioxide from the cells. • If the patient’s history and physical examination reveal evidence of respiratory dysfunction, diagnostic test that will help to identify and evaluate the dysfunction is determination of arterial blood gases. • ABG analysis is one of the first tests ordered to assess respiratory status because it helps evaluate gas exchange in the lungs. • An ABG test can measure how well the person's lungs and kidneys are working and how well the body is using energy.

  9. INDICATIONS FOR ABG • Lung Failure • Kidney Failure • Shock • Trauma • Uncontrolled diabetes • Asthma  • Chronic Obstructive Pulmonary Disease • Hemorrhage • Drug Overdose • Metabolic Disease • Chemical Poisoning

  10. INDICATIONS FOR ABG • ABG analysis is a diagnostic tool that allows the objective evaluation of a patient’s oxygenation, ventilation and acid-base balance (Coombs, 2001). • The results from an ABG will indicate how well a patient’s respiratory system is working. • - they also indicate how well a patient’s kidneys and • other internal organs (the metabolic system) are functioning.

  11. DEFINITION It is a diagnostic procedure in which blood is obtained from an artery directly by an arterial puncture or accessed by a way of indwelling arterial catheter

  12. indication • To obtain information about patient ventilation (PCO2) , oxygenation (PO2) and acid base balance • Monitor gas exchange and acid base abnormalities for patient on mechanical ventilator or not • To evaluate response to clinical intervention and diagnostic evaluation ( oxygen therapy ) • An ABG test may be most useful when a person's breathing rate is increased or decreased or when the person has very high blood sugar levels, a severe infection, or heart failure

  13. ABGcomponent • PH: measures hydrogen ion concentration in the blood, it shows blood’ acidity or alkalinity • PCO2 : It is the partial pressure of CO2 that is carried by the blood for excretion by the lungs, known as respiratory parameter • PO2: It is the partial pressure of O2 that is dissolved in the blood , it reflects the body ability to pick up oxygen from the lungs • HCO3 : known as the metabolic parameter, it reflects the kidney’s ability to retain and excrete bicarbonate

  14. Normal values: • PH = 7.35 – 7.45 • PCO2 = 35 – 45 mmhg • PO2 = 80 – 100 mmhg • HCO3 = 22 – 28 meq/L

  15. Carbon dioxide concentration • The carbon dioxide concentration (pCO2) provides information concerning ventilation and reveals whether the respiratory system is working effectively. Because of this the pCO2 is often called the respiratory parameter. The pCO2 is also measured in kPa and indicates how much carbon dioxide a patient has in their blood. The normal range is 4.5-6.0kPa (Cornock, 1996).( 35-45 mmhg ) • Carbon dioxide results from all metabolic processes in the body. In order to be removed from the body it is transported to the lungs and then exhaled. It is transported to the lungs in a plasma solution in the form of a chemical called carbonic acid (H2CO3). This is an acidic solution, so if the patient has too much or too little carbon dioxide it will become difficult for them to maintain the correct blood pH.

  16. Bicarbonate ion level and base excess • In simple terms the bicarbonate ion (HCO3) concentration and base excess (BE) provide information about how much alkali there is in the blood. This will indicate how well the patient’s metabolic system is working, which relates closely to kidney function (HuttoFaria, 1997). • HCO3 and BE are referred to as the metabolic parameter. The normal range for HCO3 is 22-26mEq/L and for base excess (BE) it is -2 to +2 (Woodrow, 2004). As both of these values essentially measure the same thing it is not necessary to consider both. • Accurate ABG analysis can be achieved by considering the HCO3 level alone.

  17. Hydrogen ion concentration • The hydrogen ion concentration (pH) provides information on acid-base balance. This relates to how much acid or alkali a patient has in their blood. The pH scale uses values from one to 14 as a way of indicating whether a solution is acidic, neutral or alkaline (Fig 1). • For the body to work effectively it needs the pH of arterial blood to be 7.4. Only small variations of 0.05 can be tolerated without causing ill effects. • So within an arterial blood gas the normal range for pH should be 7.35-7.45 (Guyton and Hall, 2000). In the simplest terms, if the pH is within the range of 7.35-7.45 the acids and the alkalis within the blood are correctly balanced.

  18. EQUIPMENT Blood gas kit OR • 1ml syringe • 23-26 gauge needle • Stopper or cap • Alcohol swab • Disposable gloves • Plastic bag & crushed ice • Lidocaine (optional) • Vial of heparin (1:1000) • label

  19. Sites for obtaining abg • Radial artery ( most common ) • Brachial artery • Femoral artery Radial is the most preferable site used because: • It is easy to access • It is not a deep artery which facilitate palpation, stabilization and puncturing • The artery has a collateral blood circulation

  20. Performance phase: • Wash hands • Put on gloves • Palpate the artery for maximum pulsation • Place a small towel roll under the patient wrist • Instruct the patient to breath normally during the test and warn him that he may feel brief cramping or throbbing pain at the puncture site • Clean with alcohol swab in circular motion • Skin and subcutaneous tissue may be infiltrated with local anesthetic agent if needed

  21. Insert needle at 45 radial ,60 brachial and 90 femoral • Withdraw the needle and apply digital pressure • Check bubbles in syringe • Place the capped syringe in the container of ice immediately • Maintain firm pressure on the puncture site for 5 minutes, if patient has coagulation abnormalities apply pressure for 10 – 15 minutes

  22. Follow up phase: • Send labeled, iced specimen to the lab immediately • Palpate the pulse distal to the puncture site • Assess for cold hands, numbness, tingling or discoloration • Documentation include: results of Allen's test, time the sample was drawn, temperature, puncture site, time pressure was applied and if O2 therapy is there • Make sure it’s noted on the slip whether the patient is breathing room air or oxygen. If oxygen, document the number of liters . If the patient is receiving mechanical ventilation, FIO2 should be documented

  23. ABG Parameters • PaO2 • Partial pressure of O2 • Normal: 80 - 100 mmHg • Measures the effectiveness of the lungs in oxygenating the blood. Reflects ability of lungs to diffuse inspired oxygen across the alveolar membrane into the circulating blood • SaO2 • Oxygen saturation • Normal: > 95% • % of hgb that is saturated with oxygen.

  24. ABG Parameters • PaCO2 • Partial Pressure of CO2 • Normal: 35 - 45 mmHg • Reflects effectiveness of ventilation (movement of air into and out of lungs). • HCO3– • Normal: 22 - 26 mEq/l • Bicarbonate ion; metabolic parameter. • Part of buffer system.

  25. pH - Normal 7.35 - 7.40 • Measures acidity • Determined by relative concentrations of CO2 and HCO3 • Base Excess • + 2 mEq/L • Amount of acid or alkali needed to titrate 1 L of fully oxygenated blood to a pH of 7.40 when T = 37 & PaCO2 = 40 mm Hg

  26. ABG Interpretation: Assess Oxgenation Step 1 • Look at PaO2 and SaO2 • Normal? • Hypoxemic

  27. ABG Interpretation: Assess Acid-Base Balance Step 2 • Look at pH • Acidotic, alkalotic, or normal? • If normal • High normal? • Low normal?

  28. ABG Interpretation: Assess Acid-Base Balance Step 3 • Look at PaCO2 • Is it altered (i.e. increased or decreased)? • If altered, consider the direction of the alteration: • Could it have caused the alteration in pH? • Could it be compensation?

  29. ABG Interpretation: Assess Acid-Base Balance Step 4 • Look at HCO3- • Is it altered (i.e. increased or decreased)? • If altered, consider the direction of the alteration: • Could it have caused the alteration in pH? • Could it be compensation?

  30. ABG Interpretation: Assess Acid-Base Balance Step 5 • Decide if the abnormal pH is caused by the pCO2 (respiratory causes) or the HCO3 (metabolic causes).

  31. ABG Interpretation: Assess Acid-Base Balance Step 6 • Determine if compensation is present • Look at parameter (PaCO2 or HCO3) that did not cause the pH disturbance. Has it changed in effort to normalize the pH? • If yes, compensation is present. • If no, compensation is not present.

  32. Quiz about aBG • Lots of pCO2 makes a patient------------ • Not enough pCO2 makes a patient -------- Lots of HCO3 makes a patient -------------– • Not enough HCO3 makes a patient----------– • If the level of pCO2 is causing the problem - it -------------------in nature – • If the level of HCO3 is causing the problem - it is --------------------in nature

  33. 1.pH: 7.24, CO2: 20, HCO3: 18 2.pH: 7.2, CO2: 52, HCO3: 25 3.pH: 7.12, CO2: 38, HCO3: 21 4.pH: 7.13, CO2: 27, HCO3: 13 5.pH: 7.66, CO2: 43, HCO3: 37 6.pH: 7.25, CO2: 20, HCO3: 19 7.pH: 7.1, CO2: 38, HCO3: 18 8.pH: 7.39, CO2: 46, HCO3: 27 9.pH: 7.39, CO2: 55, HCO3: 31 10.pH: 7.39, CO2: 35, HCO3: 25

  34. pH: 7.24, CO2: 20, HCO3: 18 - Partially Compensated Metabolic Acidosis pH: 7.2, CO2: 52, HCO3: 25 - Uncompensated Respiratory Acidosis pH: 7.12, CO2: 38, HCO3: 21 - Uncompensated Metabolic Acidosis pH: 7.13, CO2: 27, HCO3: 13 - Partially Compensated Metabolic Acidosis pH: 7.66, CO2: 43, HCO3: 37 - Uncompensated Metabolic Alkalosis pH: 7.25, CO2: 20, HCO3: 19 - Partially Compensated Metabolic Acidosis pH: 7.1, CO2: 38, HCO3: 18 - Uncompensated Metabolic Acidosis pH: 7.39, CO2: 46, HCO3: 27 - Fully Compensated Respiratory Acidosis pH: 7.39, CO2: 55, HCO3: 31 - Fully Compensated Respiratory Acidosis pH: 7.39, CO2: 35, HCO3: 25 - Normal

  35. pH: 7.56, CO2: 26, HCO3: 14 • pH: 7.72, CO2: 23, HCO3: 26 • pH: 7.16, CO2: 22, HCO3: 13 • pH: 7.13, CO2: 46, HCO3: 27 • pH: 7.2, CO2: 36, HCO3: 16 • pH: 7.58, CO2: 38, HCO3: 28 • pH: 7.42, CO2: 45, HCO3: 23 • pH: 7.3, CO2: 54, HCO3: 25 • pH: 7.1, CO2: 40, HCO3: 18 • pH: 7.32, CO2: 43, HCO3: 18

  36. pH: 7.56, CO2: 26, HCO3: 14 - Partially Compensated Respiratory Alkalosis • pH: 7.72, CO2: 23, HCO3: 26 - Uncompensated Respiratory Alkalosis • pH: 7.16, CO2: 22, HCO3: 13 - Partially Compensated Metabolic Acidosis • pH: 7.13, CO2: 46, HCO3: 27 - Partially Compensated Respiratory Acidosis • pH: 7.2, CO2: 36, HCO3: 16 - Uncompensated Metabolic Acidosis • pH: 7.58, CO2: 38, HCO3: 28 - Uncompensated Metabolic Alkalosis • pH: 7.42, CO2: 45, HCO3: 23 - Normal • pH: 7.3, CO2: 54, HCO3: 25 - Uncompensated Respiratory Acidosis • pH: 7.1, CO2: 40, HCO3: 18 - Uncompensated Metabolic Acidosis • pH: 7.32, CO2: 43, HCO3: 18 - Uncompensated Metabolic Acidosis

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