4 ABG - Acid base disorder PDF

Basic Arterial Blood Gases Mohammed Ahmed SeNaN MsRC, BS , RCP 4 Respiratory Therapist Department  Make it easy The 6 steps to ABG Interpretation November 24 Mohammed-SeNaN- MsRC 2 2 INTRODUCTION: The major function of the pulmonary sy...

Basic Arterial Blood Gases Mohammed Ahmed SeNaN MsRC, BS , RCP 4 Respiratory Therapist Department  Make it easy The 6 steps to ABG Interpretation November 24 Mohammed-SeNaN- MsRC 2 2 INTRODUCTION: The major function of the pulmonary system (lungs and pulmonary circulation) is to deliver oxygen to cells and remove carbon dioxide from the cells. 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.  Homeostatsis "The maintenance of a constant internal environment". “ All living creature keeping their inside as constant and stable operating condition as possible, whatever may be happening on the outside” November 24 Mohammed-SeNaN- MsRC 4  Example homeostasis in human body Acid-base (pH) balance, body temperature, Calcium and Phosphate level, blood glucose, fluid volume, blood pressure etc. November 24 Mohammed-SeNaN- MsRC 5 November 24 Mohammed-SeNaN- MsRC 6 Importance of acid base (pH) balance  If the pH changes whether up or down: 1. protein and enzymes becomes stop functioning. 2. muscles and nerves becomes weakening. 3. metabolic activities becomes impaired. 4. blood pH below 6.9 or above 7.9 would be life threatening.  Car bon ic aci d - Bi car bonat e Bu f f er i ng Sy st em A major buffer system in the acid-base balance. To alter any acid base imbalance thus maintain a constant plasma pH. Base on carbonic acid equilibrium equation and involve 2 systems: lung and kidney  Ca r b o n i c a c i d - Bi c a r b o n a t e Bu f f e r i n g S y s t e m 1) The way of 2 systems interact is through the formation of carbonic acid (H2CO3). 2 ) Movement through the carbonic acid system is tend maintain a equilibrium status. 3 ) If necessary, H2CO3 can break up to form either H+ and HCO3 or CO2 and H2O 4 ) The system works in both directions. 5 ) By balancing back and forward, a normal pH is achieved.  Renal mechanisms  Can eliminate large amounts of acid (H+)  Excretion or retention of base (HCO3-)  Can reserve and produce bicarb ions HCO3 ion+ Na ion NaHCO3  Most effective regulator of pH but slow  Respiratory mechanisms  Exhalation of carbon dioxide  Excretion and retention of CO2  Adjust body pH by changing rate and depth of breathing Response to acidosis Response to alkalosis  Acidosis and alkalosis: There are two abnormalities of acid-base balance: Y Acidosis: Too much acid or too little base, resulting in a decrease in blood pH7.45  Metabolic or Respiratory acid base imbalance Y Acidosis and alkalosis are categorized as metabolic or respiratory Y Depends on their primary cause. 1. Metabolic acidosis and metabolic alkalosis are caused by an imbalance acids or bases production or excretion by the kidneys. 2. Respiratory acidosis and respiratory alkalosis are caused by amount of carbon dioxide exhalation due to lung or breathing disorders. 3 DEFINITION: It is a diagnostic procedure in which a blood is obtained from an artery directly by an arterial puncture or accessed by a way of indwelling arterial catheter  INDICATION: 4 - 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. - 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  EQUIPMENT: 5 - Blood gas kit - 1ml syringe - 23-26 gauge needle - cap - Alcohol swab - Disposable gloves - Plastic bag & crushed ice - Lidocaine (optional Vial of heparin 1:1000) - label 6 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  Radial artery cannulation: 7  Brachial artery puncture: 8 9 PERFORMANCE PHASE: -Wash hands - Put on gloves -Palpate the artery for maximum pulsation If radial, perform Allen's test - 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 10 ALLEN’S TEST: It is a test done to determine that collateral circulation is present from the ulnar artery in case thrombosis occur in the radial - 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  Factors affecting ABG results 1. Temperature 2. The presence of air bubbles in ABG sample 3. Excessive heparin sodium in the sample 4. Clotted sample 5. Time between taken and analysis 6. Site of sampling (venous, arterial)  SPECIMEN CARE: 12 Several things should be considered prior to sending the specimen to the lab: Gas diffusion through the plastic syringe is a potential source of error 13 Air bubbles that exceed 1 to 2 % of the blood volume can cause a falsely high PaO2 and a falsely low PaC02. gently removing the bubbles without agitation and analyzing the sample as soon as possible  TRANSPORT: 14 - IT should be placed on ice during transport to the lab and then analyzed as quickly as possible. This reduces oxygen consumption by leukocytes, which can cause a factitiously low PaO2. In addition, it reduces the likelihood that error due to gas diffusion through the plastic syringe or air bubbles will be clinically significant.  COMPLICATION: 15 -Arteriospasm - Hematoma - Hemorrhage - Distal ischemia - Infection - Numbness 16 ABG COMPONENT - 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.  NORMAL VALUES: 17 ❖PH = 7.35 – 7.45 ❖PCO2 = 35 – 45 mmhg ❖PO2= 80 – 100 mmhg ❖HCO3 = 22 – 26meq/L  pH 7.4 HCO-3 Respiratory Component Metabolic Component (acid) (base) Arterial blood pH = 7.40 Venous Blood pH = 7.35 18 19 Feb,2015 Prepared by NLERT 34  o r ma l rr aa nn gg ee No pH 7.35-7.45 pCO2 35-45mmHg or 4.7 -6 kPa pO2 80-100mmHg or 10.3-13.3 kPa O2 saturation 95-100% HCO3- 22-26mEq/L Base Excess +2 November 24 Mohammed-SeNaN- MsRC 36 Te s t No r ma l ↓ Va l u e ↑ Va l u e pH 7.35- 7.45 Ac i d o s i s ↓ Al k a l o s i s ↑ p CO2 35- 45mmHg Al k a l o s i s ↓ Ac i d o s i s ↑ Or 4.7- 6Kp a HCO3 22- 26 mEq /L Ac i d o s i s ↓ Al k a l o s i s ↑ p O2 80- 100 mmHg Hy p o x e mi a Sa O2 95- 100% Hy p o x e mi a  6 Ea s y St e p s t o ABG Int er pr et at i on (1)Is the pH normal? (2)Is the CO2 normal? (3)Is the HCO3 normal? (4) Match the CO2 or HCO3 with the pH? (Identifying primary cause) (5)Does the CO2 or HCO3 in the opposite direction of the pH? (Compensation) (6)Are the PaO2 and SaO2 normal?  ABG quiz 1. Metabolic Acidosis has a low level of what? A: PO2 B: CO2 C: Compensated Respiratory Acidosis D: Bicarbonate (HCO3) 2. pH=7.18 PaCO2=68 HCO3=29 A: Uncompensated Metabolic Acidosis B: Partly compensated respiratory acidosis C: Combined Acidosis D: Uncompensated respiratory Acidosis 3.Decrease HCO3 and decrease pH may causes what? A: Uncompensated B: Increase arterial PO2 C: It will lower the pH D: Metabolic Acidosis 4.The primary drive to breath comes from the patient? A: Acidosis B: Bicarbonate (HCO3) C: Uncompensated Metabolic Acidosis D: CO2 level 5. A high CO2 will impact the pH? A: Lower the pH value (acidosis) B: Bicarbonate (HCO3) C: Increase arterial PO2 D: Metabolic Acidosis 6. pH = 7.56 CO2 = 50 HCO3 = 38 A: Normal B: Respiratory alkalosis without compensation C: Partly compensated metabolic alkalosis D: Metabolic alkalosis 7. pH = 6.96 CO2 = 71 HCO3 = 16 A: Metabolic alkalosis B: Normal C: Mixed acidosis D: Compensated acidosis 8. Interpret this blood gas pH=7.50 PaCO2=60 HCO3=38 A: Combined acidosis B: Partly compensated metabolic Alkalosis C: Bicarbonate (HCO3) D: Increase ventilation 9. pH = 7.16 CO2 = 82 HCO3 = 29 A: Metabolic acidosis B: Partly compensated metabolic alkalosis C: Respiratory alkalosis D: Partly compensated respiratory acidosis FEb,2015 10. pH = 7.50 CO2 = 9 HCO3 = 7 A: Partly compensated respiratory alkalosis B: Respiratory alkalosis C: Metabolic alkalosis D: Partly compensated metabolic alkalosis 11. pH = 7.75 CO2 = 29 HCO3 = 40 A: Combined acidosis B: Mixed alkalosis C: Compensated respiratory acidosis D: Compensated metabolic alkalosis 12. pH = 7.33 CO2 = 66 HCO3 = 35 A: Compensated respiratory acidosis B: Metabolic alkalosis C: Metabolic acidosis D: Partly compensated respiratory acidosis  13. pH = 6.68 CO2 = 85 HCO3 = 10 A: Combined alkalosis B: Compensated respiratory alkalosis C: Mixed acidosis D: Metabolic respiratory acidosis Feb,2015 Prepared by NLERT 14. pH = 7.35 CO2 = 42 HCO3 = 23 A: Combined alkalosis B: Normal C: Combined acidosis D: Partly compensated metabolic acidosis 15. pH = 7.21 CO2 = 60 HCO3 = 24 A: Respiratory acidosis without compensation B: Compensated metabolic alkalosis C: Compensated respiratory acidosis D: Compensated respiratory alkalosis 16. pH = 7.48 CO2 = 19 HCO3 = 14 A: Normal B: Respiratory acidosis C: Compensated metabolic acidosis D: Partly compensated respiratory alkalosis  Steps for ABG analysis 1. Are the data consistent 2. What is the pH? Acidemic or Alkalemic? 3. What is the primary disorder present? 4. Is there appropriate compensation? 5. Is the compensation acute or chronic? 6. Is there an anion gap? 7. If there is a AG, what is the delta gap? 8. What is the differential for the clinical processes? November 24 Mohammed-SeNaN- MsRC 56 November 24 Mohammed-SeNaN- MsRC 57 November 24 Mohammed-SeNaN- MsRC 58  6-steps- approach: Step 1: Assess the internal consistency of the values using the Henderseon-Hasselbach equation: [H+] = 24 (PaCO2) [HCO3-] If the pH and the [H+] are inconsistent, the ABG is probably not valid. November 24 Mohammed-SeNaN- MsRC 59  pH Approximate [H+] (mmol/L) 7.00 100 7.05 89 7.10 79 7.15 71 7.20 63 7.25 56 7.30 50 7.35 45 7.40 40 7.45 35 7.50 32 7.55 28 7.60 25 7.65 22 November 24 Mohammed-SeNaN- MsRC 64 November 24 Mohammed-SeNaN- MsRC 65  DETERMINE PRIMARY DISORDER Check the trend of the pH, HCO3, pCO2 The change that produces the pH is the primary disorder pH = 7.25 HCO3 = 12 pCO2 = 30 ACIDOSIS ACIDOSIS ALKALOSIS METABOLIC ACIDOSIS  DETERMINE PRIMARY DISORDER Check the trend of the pH, HCO3, pCO2 The change that produces the pH is the primary disorder pH = 7.25 HCO3 = 28 pCO2 = 60 ACIDOSIS ALKALOSIS ACIDOSIS RESPIRATORY ACIDOSIS  DETERMINE PRIMARY DISORDER Check the trend of the pH, HCO3, pCO2 The change that produces the pH is the primary disorder pH = 7.55 HCO3 = 19 pCO2 = 20 ALKALOSIS ACIDOSIS ALKALOSIS RESPIRATORY ALKALOSIS  DETERMINE PRIMARY DISORDER If the trend is the same, check the percent difference The bigger % difference is the 10 disorder (16-24)/24 = 0.33 (60-40)/40 = 0.5 pH = 7.25 HCO3 = 16 pCO2 = 60 ACIDOSIS ACIDOSIS ACIDOSIS RESPIRATORY ACIDOSIS  DETERMINE PRIMARY DISORDER If the trend is the same, check the percent difference The bigger %difference is the 10 disorder (38-24)/24 = 0.58 (30-40)/40 = 0.25 pH = 7.55 HCO3 = 38 pCO2 = 30 ALKALOSIS ALKALOSIS ALKALOSIS METABOLIC ALKALOSIS  CHECK THE COMPENSATORY RESPONSE Is there appropriate compensation for the primary disturbance? 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. November 24 Mohammed-SeNaN- MsRC 72 November 24 Mohammed-SeNaN- MsRC 73 November 24 Mohammed-SeNaN- MsRC 74 November 24 Mohammed-SeNaN- MsRC 75 Metabolic acidosis PCO2= 1.5 X HCO3 + 8 +-2 Metabolic alkalosis PCO2= o.7 X HCO3 + 20 +_1.5  PCO2 HCO3 Acute respiratory ↑ 10 ↑ 1 acidosis Acute respiratory ↓ 10 ↓ 2 alkalosis Chronic respiratory ↑ 10 ↑ 3.5 acidosis Chronic respiratory ↓ 10 ↓ 4 alkalosis  Disorder Expected compensation Correction factor Metabolic acidosis PaCO2 = (1.5 x [HCO3-]) +8 ±2 Acute respiratory acidosis Increase in [HCO3-]= ∆ PaCO2/10 ±3 Chronic respiratory Increase in [HCO3-]= 3.5(∆ PaCO2/10) acidosis (3-5 days) Metabolic alkalosis Increase in PaCO2 = 40 + 0.6(∆HCO3-) Acute respiratory alkalosis Decrease in [HCO3-]= 2(∆ PaCO2/10) Chronic respiratory Decrease in alkalosis [HCO3-] = 5(∆ PaCO2/10) to 7(∆ PaCO2/10) November 24 Mohammed-SeNaN- MsRC 78  COMPENSATORY RESPONSE METABOLIC ACIDOSIS PaCO2 = (1.5 X HCO3) + 8 ± 2 Winter's formula HCO3 =12 PaCO2 =1.5 X 12 + 8 = 26 ± 2 HCO3 =7 PaCO2 = 1.5 X 7 + 8 = 18.5 ± 2  OR Last two digits of pH should equal PCO2 –if equal = no respiratory disturbances –if PCO2 high = overlapping respiratory acidosis –if PCO2 low = overlapping respiratory alkalosis November 24 Mohammed-SeNaN- MsRC 81 November 24 Mohammed-SeNaN- MsRC 82 November 24 Mohammed-SeNaN- MsRC 83  CALCULATE THE ANION GAP Calculate the anion gap (if a metabolic acidosis exists): AG= [Na+]-( [Cl-] + [HCO3-] )-12 ± 2 A normal anion gap is approximately 12 meq/L. In patients with hypoalbuminemia, the normal anion gap is lower than 12 meq/L; the “normal” anion gap in patients with hypoalbuminemia is about 2.5 meq/L lower for each 1 gm/dL decrease in the plasma albumin concentration (for example, a patient with a plasma albumin of 2.0 gm/dL would be approximately 7 meq/L.) November 24 Mohammed-SeNaN- MsRC 85 November 24 Mohammed-SeNaN- MsRC 86 November 24 Mohammed-SeNaN- MsRC 87 November 24 Mohammed-SeNaN- MsRC 88  Important easy formula November 24 Mohammed-SeNaN- MsRC 89  ANION GAP Na – (HCO3 + Cl) = 10-12 mmol/L Na = 135 HCO3 = 15 Cl = 97 RBS = 100 mg% Anion Gap = 135 – (15 + 97) =135 -112 = 23 November 24 Mohammed-SeNaN- MsRC 91 November 24 Mohammed-SeNaN- MsRC 92 November 24 Mohammed-SeNaN- MsRC 93 November 24 Mohammed-SeNaN- MsRC 94 November 24 Mohammed-SeNaN- MsRC 95 November 24 Mohammed-SeNaN- MsRC 96  CHECK THE DELTA / DELTA If an increased anion gap is present, assess the relationship between the increase in the anion gap and the decrease in [HCO3-]. Assess the ratio of the change in the anion gap (∆AG ) to the change in [HCO3-] (∆[HCO3-]): ∆AG/∆[HCO3-] This ratio should be between 1.0 and 2.0 if an uncomplicated anion gap metabolic acidosis is present. If this ratio falls outside of this range, then another metabolic disorder is present: If ∆AG/∆[HCO3-] < 1.0, then a concurrent non-anion gap metabolic acidosis is likely to be present.  AG = Na – Cl – HCO3 (normal 12 ± 2)  AG corrected = AG + 2.5[4 – albumin]  If there is an anion Gap then calculate the Delta/delta gap.  Only need to calculate delta gap (excess anion gap) when there is an anion gap to determine additional hidden metabolic disorders (nongap metabolic acidosis or metabolic alkalosis)  If there is no anion gap then start analyzing for non- anion acidosis  DELTA - DELTA AG/HCO3 = 1 Pure Anion gap metabolic acidosis AG/HCO3 > 1 AG Metabolic Acidosis + metabolic alkalosis AG Metabolic Acidosis AG/HCO3 < 1 + non-AG metabolic acidosis November 24 Mohammed-SeNaN- MsRC 100 November 24 Mohammed-SeNaN- MsRC 101 November 24 Mohammed-SeNaN- MsRC 102 November 24 Mohammed-SeNaN- MsRC 103 November 24 Mohammed-SeNaN- MsRC 104 November 24 Mohammed-SeNaN- MsRC 105 November 24 Mohammed-SeNaN- MsRC 106 November 24 Mohammed-SeNaN- MsRC 107 November 24 Mohammed-SeNaN- MsRC 108 November 24 Mohammed-SeNaN- MsRC 109 Questions ?? November 24 Mohammed-SeNaN- MsRC 110 http://dc10.arabsh.com/i/02764/23oogtqhhpk7.gif Have a great day November 24 Mohammed-SeNaN- MsRC 111