医学交流课件：血气分析 英文

1、ABG INTERPRETATION Objectives Whats an ABG? Understanding Acid/Base Relationship General approach to ABG Interpretation Clinical causes Abnormal ABGs Case studies Take home What is an ABG Arterial Blood Gas Drawn from artery- radial, brachial, femoral It is an invasive procedure. Caution must be tak

2、en with patient on anticoagulants. Helps differentiate oxygen deficiencies from primary ventilatory deficiencies from primary metabolic acid-base abnormalities What Is An ABG? pHH+ PCO2 Partial pressure CO2 PO2 Partial pressure O2 HCO3 Bicarbonate BE Base excess SaO2 Oxygen Saturation Acid/Base Rela

3、tionship This relationship is critical for homeostasis Significant deviations from normal pH ranges are poorly tolerated and may be life threatening Achieved by Respiratory and Renal systems Case Study No. 1 60 y/o male comes ER c/o SOB. Tachypneic, tachycardic, diaphoretic and Cyanotic. Dx acute re

4、sp. failure and ABGs Show PaCO2 well below nl, pH above nl, PaO2 is very low. The blood gas document Resp. failure due to primary O2 problem. Case Study No. 2 60 y/o male comes ER c/o SOB. Tachypneic, tachycardic, diaphoretic and Cyanotic. Dx acute resp. failure and ABGs Show PaCO2 very high, low pH

5、 and PaO2 is moderately low. The blood gas document Resp. failure due to primarily ventilatory insufficiency. There are two buffers that work in pairs H2CO3NaHCO3 Carbonic acid base bicarbonate These buffers are linked to the respiratory and renal compensatory system Buffers Respiratory Component fu

6、nction of the lungs Carbonic acid H2CO3 Approximately 98% normal metabolites are in the form of CO2 CO2 + H2O H2CO3 excess CO2 exhaled by the lungs Metabolic Component Function of the kidneys base bicarbonate Na HCO3 Process of kidneys excreting H+ into the urine and reabsorbing HCO3- into the blood

7、 from the renal tubules 1) active exchange Na+ for H+ between the tubular cells and glomerular filtrate 2) carbonic anhydrase is an enzyme that accelerates hydration/dehydration CO2 in renal epithelial cells H2O + CO2 H2CO3 HCO3 + H+ Acid/Base Relationship Normal ABG values pH7.35 7.45 PCO235 45 mmH

8、g PO280 100 mmHg HCO322 26 mmol/L BE-2 - +2 SaO295% AcidosisAlkalosis pH 45 HCO3 7.45 PCO2 26 Respiratory Acidosis Think of CO2 as an acid failure of the lungs to exhale adequate CO2 pH 45 CO2+ H2CO3 pH Causes of Respiratory Acidosis emphysema drug overdose narcosis respiratory arrest airway obstruc

9、tion Metabolic Acidosis failure of kidney function blood HCO3 which results in availability of renal tubular HCO3 for H+ excretion pH 7.35 HCO3 7.45 PCO2 7.45 HCO3 26 Causes of Metabolic Alkalosis loss acid from stomach or kidney hypokalemia excessive alkali intake How to Analyze an ABG 1. PO2NL = 8

10、0 100 mmHg 2. pHNL = 7.35 7.45 Acidotic7.45 3. PCO2NL = 35 45 mmHg Acidotic45 Alkalotic35 4. HCO3NL = 22 26 mmol/L Acidotic 26 Four-step ABG Interpretation Step 1: Examine PaO2 Clinical Application of Blood Gases; 1994 2. American Journal of Nursing1999;Aug99(8):34-6 3. Journal Post Anesthesia Nursi

11、ng1990;Aug;5(4)264-72 4. Irvine, David;ABG Interpretation, A Rough and Dirty Production Practice ABGs 1. PaO2 90SaO295 pH 7.48 PaCO2 32 HCO3 24 2. PaO2 60SaO290 pH 7.32 PaCO2 48 HCO3 25 3. PaO2 95SaO2100 pH 7.30 PaCO2 40 HCO3 18 4. PaO2 87SaO2 94 pH 7.38 PaCO2 48 HCO3 28 5. PaO2 94SaO2 99 pH 7.49 Pa

12、CO2 40 HCO3 30 6. PaO2 62SaO2 91 pH 7.35 PaCO2 48 HCO3 27 7. PaO2 93SaO2 97 pH 7.45 PaCO2 47 HCO3 29 8. PaO2 95SaO2 99 pH 7.31 PaCO2 38 HCO3 15 9. PaO2 65SaO2 89 pH 7.30 PaCO2 50 HCO3 24 10. PaO2 110 SaO2 100 pH 7.48 PaCO2 40 HCO3 30 Answers to Practice ABGs 1. Respiratory alkalosis 2. Respiratory acidosis 3. Metabolic acidosis 4. Compen