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1、1,ABG INTERPRETATION血气分析解读,SIMC ICU Liu,2,Objectives,Whats an ABG? Understanding Acid/Base Relationship General approach to ABG Interpretation Clinical causes Abnormal ABGs Case studies,3,What is an ABG,Arterial Blood Gas 动脉血气 Drawn from artery- radial, brachial, femoral 由动脉取样一般取桡动脉、肱动脉、股动脉 It is an
2、 invasive procedure. 这是侵入性检查 Caution must be taken with patient on anticoagulants. 有凝血功能障碍的患者慎用 Helps differentiate oxygen deficiencies from primary ventilatory deficiencies from primary metabolic acid-base abnormalities 协助区分缺氧/通气不足和酸碱代谢异常,4,What Is An ABG?,pH H+ PCO2 Partial pressure CO2 PO2 Partia
3、l pressure O2 HCO3 Bicarbonate BE Base excess SaO2 Oxygen Saturation,5,Acid/Base Relationship,This relationship is critical for homeostasis酸碱平衡对内环境是非常重要的 Significant deviations from normal pH ranges are poorly tolerated and may be life threatening 酸碱严重失衡后果严重，甚至可能致命 Achieved by Respiratory and Renal
4、systems 一般由呼吸系统和肾脏决定,6,Case Study No. 1,60 y/o male comes ER c/o SOB.Tachypneic, tachycardic, diaphoretic and Cyanotic. Dx acute resp. failure and ABGsShow PaCO2 well below nl, pH above nl, PaO2 is very low. The blood gas documentResp. failure due to primary O2 problem. 60岁男性进入急诊室。查体见呼吸过速、心动过速、大汗、发绀
5、，诊断急性呼衰。动脉血气分析结果PaCO轻度降低，PH升高，PaO2非常低。结果显示其主要问题为缺氧,7,Case Study No. 2,60 y/o male comes ER c/o SOB.Tachypneic, tachycardic, diaphoretic and Cyanotic. Dx acute resp. failure and ABGsShow PaCO2 very high, low pH and PaO2 is moderately low. The blood gas document Resp. failure due to primarily ventilat
6、or insufficiency. 60岁男性进入急诊室。查体，呼吸过塑，心动过速，大汗，发绀，诊断急性呼衰。动脉血气分析结果显示PaCO2非常高，PH降低，PaO2中度降低。结果显示其主要问题为通气不足。,8,Buffers,There are two buffers that work in pairs H2CO3NaHCO3Carbonic acidbase bicarbonate These buffers are linked to the respiratory and renal compensatory system 两者和呼吸、肾脏代偿密切相关,9,Respiratory C
7、omponent,function 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,10,Metabolic Component,Function of the kidneys base bicarbonate NaHCO3 Process of kidneys excreting H+ into the urine and reabsorbing HCO3- i
8、nto the blood from the renal tubules 肾脏将H+排泄至尿液，并从肾小管重吸收HCO3-1)active exchange Na+ for H+ between the tubular cells and glomerular filtrate 在肾小管和肾小球主动用Na+交换H+2)carbonic anhydrase is an enzyme that accelerates hydration/dehydration CO2 in renal epithelial cells 可以加速CO2在肾上皮细胞的水化和脱水反应,11,Acid/Base Rela
9、tionship,H2O+CO2 H2CO3 HCO3+H+,12,Normal ABG values,pH 7.35 7.45 PCO2 35 45 mmHg PO280 100 mmHg HCO3 22 26 mmol/L BE -2 - +2 SaO2 95%,13,Acidosis酸中毒Alkalosis碱中毒,pH 45 HCO3 22,pH 7.45 PCO2 26,14,Respiratory Acidosis,Think of CO2 as an acid 把二氧化碳想象成酸 failure of the lungs to exhale adequate CO2 肺无法排出足够
10、的二氧化碳 pH 45 CO2+ H2CO3 pH,15,Causes of Respiratory Acidosis,Emphysema 肺气肿 drug overdose 药物过量 narcosis 麻醉 respiratory arrest 呼吸暂停 airway obstruction 气道阻塞,16,Metabolic Acidosis,failure of kidney function blood HCO3 which results in availability of renal tubular HCO3 for H+ excretion pH 7.35 HCO3 22,17
11、,Causes of Metabolic Acidosis,renal failure 肾衰竭 diabetic ketoacidosis 酮症酸中毒 lactic acidosis 乳酸酸中毒 excessive diarrhea 严重腹泻 cardiac arrest 心跳骤停,18,Respiratory Alkalosis,too much CO2 exhaled (hyperventilation) 过度通气 PCO2, H2CO3 insufficiency = pH pH 7.45 PCO2 35,19,Causes of Respiratory Alkalosis,hyperv
12、entilation 过度通气 panic d/o pain pregnancy acute anemia 急性贫血 salicylate overdose 水杨酸过量,20,Metabolic Alkalosis,plasma bicarbonate pH 7.45 HCO3 26,21,Causes of Metabolic Alkalosis,loss acid from stomach or kidney 由胃或肾脏过量丢失酸性物质 hypokalemia 低血钾 excessive alkali intake 过量碱性物质摄入,22,How to Analyze an ABG,PO2
13、NL = 80 100 mmHg pHNL = 7.35 7.45 Acidotic7.45 PCO2NL = 35 45 mmHg Acidotic45 Alkalotic 26,23,Four-step ABG Interpretation,Step 1: Examine PaO2 & SaO2 Determine oxygen status Low PaO2 (80 mmHg) & SaO2 means hypoxia PaO2和SaO2降低提示缺氧 NL/elevated oxygen means adequate oxygenation 正常或更高的数值表明氧合充分,24,Four-
14、step ABG Interpretation,Step 2: pHacidosis 7.45,25,Four-step ABG Interpretation,Step 3: study PaCO2 & HCO 3 respiratory irregularity if PaCO2 abnl & HCO3 NL 呼吸系统异常会显示PaCO2异常，HCO3正常 metabolic irregularity if HCO3 abnl & PaCO2 NL 代谢系统异常会显示HCO3异常，PaCO2正常,26,Four-step ABG Interpretation,Step 4: Determin
15、e if there is a compensatory mechanism working to try to correct the pH. 判断机体是否在进行代偿 ie: if have primary respiratory acidosis will have increased PaCO2 and decreased pH.Compensation occurs when the kidneys retain HCO3. 例如：如果主要是呼吸性酸中毒的话会导致PaCO2升高，PH降低。当肾脏仍有足够的HCO3时会进行代偿,27, PaCO2 pH Relationship,807.
16、20607.30407.40307.50207.60,28,ABG Interpretation,Compensated,Respiratory,Acidosis,CO2,More Abnormal,Respiratory,Acidosis,CO2,Expected,Mixed,Respiratory,Metabolic,Acidosis,CO2,Less Abnormal,CO2 Change,c/w,Abnormality,Metabolic,Metabolic Acidosis,CO2,Normal,Compensated,Metabolic,Acidosis,CO2 Change,opposes,Abnormality,Acidosis酸中毒,29,ABG Interpretation,Compensated,Respiratory,Alkalosi
