医学如何看血气分析结.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,如何看血气分析结,什么是血气分析,血气是指血液中所含的O2和CO2气体。,血气分析是指通过测定血液的pH、PO2、PCO2值，以及根据这些测定值推算出诸如SB、AB、BE、SatO2等参数来评价病人呼吸、氧合及酸碱平衡状态。,血气分析测定原理,早年进行血氧和二氧化碳的测定是采用经典的VanSlyke量气法。,此法原理是在真空密闭条件下利用皂素破坏红细胞，再用铁氢化钾破坏血红蛋白以释放O2，加辛酸去泡剂等混合液，然后测量所释气体的压力。而后又用CO2吸收剂及O2吸收剂分别将两种气体吸收，根据压力的改变，再计算出CO2和O2的含量。,血气分析测定原理,该法虽然准确可靠，但操作繁锁，又使用大量水银，极易污染环境，现在较少使用。,目前测定血气的仪器主要由专门的气敏电极分别测出O2、CO2和pH三个数据，并推算出一系列参数。,标本,一般采集动脉血,静脉血只能用于判定酸碱平衡情况。,采静脉血尽可能不使用止血带。,动脉血采集可在肱动脉、股动脉、前臂动脉以及其他任何部位的动脉进行。,用肝素抗凝，注意注射器内不能有肝素液残留。,标本,采血1-2ml即可。,拔针后，注射器不能回吸，只能稍外推，使血液充满针尖空隙，并排出第一滴血弃之,将塑料嘴或橡皮泥封住针头，隔绝空气,来回搓滚注射器，混匀抗凝血，立即送检。,也可采用微量取样器采集血标本。,标本放置时间,标本于体外37保存，每10分钟PCO2约增加1mmHg，pH值降低约0.01单位。,血样于4保存1小时内，其中pH、PCO2值没有明显变化，PO2值则有改变。,采取的血标本应在30分钟内检测完毕，如30分钟后不能检测，应将标本置于冰水中保存，最多不超过2小时，在30分钟到2小时之间，血PO2值仅供参考。,血气分析的检测目的,判断机体是否存在缺氧和缺氧程度,判断机体是否存在酸碱平衡失调,有助于了解病人内环境情况,血气分析常用指标,pH,氢离子浓度负对数,PCO,2,二氧化碳分压,PO,2,氧分压,HCO,3,碳酸氢盐,SB 标准碳酸氢盐,AB 实际碳酸氢盐,BE,碱剩余,SaO,2,氧饱和度,其他：K、Na、Cl,血气分析正常值,pH7.35 7.45 mean 7.40,PCO,2,35 45 mmHg mean 40mmHg,PO,2,80 100 mmHg,HCO,3,22 26 mmol/L mean 24mmol/L,BE-2-+2 mean 0,SaO,2,95%,离子正常值,Na+（135150 mmol/L，平均142 mmol/L）,K+（3.55.5 mmol/L，平均4.04.5 mmol/L）,Cl（98108 mmol/L，平均103 mmol/L）,四步法分析结果,Step 1:,Examine PaO,2,&SaO,2,氧分压(PaO2)与,氧饱和度,氧分压就是指物理溶解在血液中氧分子所产生的压力。,血氧饱和度是指氧与Hb结合的程度，是单位Hb含氧百分数。,正常,：PaO280mmHg,SaO295%,低氧血症：PaO2 80 mmHg,低氧血症分级,轻度,PaO,2,6080mmHg,中度,PaO,2,4059mmHg,重度,PaO,2,40mmHg,低 氧 血 症 病 因,(一)由于通气不足引起(伴高碳酸血症),(二)由于换气功能衰竭,肺炎、肺水肿、ARDS、,肺不张、肺栓塞等,(三)其它,高原,右,左分流的心血管病,Step 2:,分析,pH,四步法分析结果,pH值,是指体液中氢离子的负对数，是反应体液总酸度的指标，受呼吸和代谢因素共同影响。,正常：,动脉血7.357.45，平均7.40,异常,PH方向向下改变-7.45-碱血症,Step 3:,study PaCO,2,&HCO,3,四步法分析结果,二氧化碳分压(PaCO2),指物理溶解在血液中的二氧化碳分子所产生的压力,是肺泡通气量的,唯一,指标,也是酸碱平衡的指标,实际碳酸氢盐（HCO3-，AB）,隔绝空气的血液标本在实验条件下测得的血浆HCO3值,正常值为2227mmol/L，平均24mmol/L，动静脉血大致相等,标准碳酸氢盐（,standard bicarbonate，,SB）,SB是指血浆在标准条件下（37，PaCO2 40mmHg，Hb100%氧合时）所测得的HCO3-含量。,正常值为22-27mmol/L，平均为24mmol/L。不受呼吸因素的影响。,碱剩余（base excess，BE）,BE指标本在37，PCO2 40mmHg，Hb100%氧合情况下，将全血滴定至pH7.4时所需用的酸或碱的数量。需用酸量为正值，需用碱量为负值。,酸 碱 失 衡 的 类 型,一、单纯性酸碱紊乱,代酸、代碱、呼酸、呼碱,二、混合性酸碱紊乱,呼酸代酸、呼酸代碱,呼碱代酸、呼碱代碱,三、三重酸碱紊乱,代酸代碱呼酸,代酸代碱呼碱,Respiratory Acidosis,Think of CO,2,as an acid,（,H2O +CO2,H2CO3,）,failure of the lungs to exhale adequate CO,2,PCO,2,45,pH 7.35,Causes of Respiratory Acidosis,emphysema,drug overdose,narcosis,（,麻醉）,respiratory arrest,airway obstruction,Metabolic Acidosis,failure of kidney function,blood HCO,3,which results in,availability of renal tubular HCO,3,for H,+,excretion,pH 7.35,HCO,3,7.45,PCO,2,7.45,HCO,3,26,Causes of Metabolic Alkalosis,loss acid from stomach or kidney,hypokalemia,excessive alkali intake,Case Study No.1,56 yo,neurologic dz required ventilator support for several,weeks.She seemed most comfortable when hyperventilated,to PaCO,2,28-30 mmHg.She required daily doses of lasix to,assure adequate urine output and received 40 mmol/L IV K,+,each day.On 10th day of ICU her ABG on 24%oxygen&VS:,ABG Results,pH7.62,BP115/80 mmHg,PCO,2,30 mmHg,Pulse88/min,PO,2,85 mmHgRR10/min,HCO,3,30 mmol/L,VT1000ml,BE10 mmol/LMV10L,K,+,2.5 mmol/L,Case study No.2,27 yo retarded（,迟钝）,with insulin-dependent DM arrived at ER,from the institution where he lived.On room air ABG&VS:,pH7.15,BP180/110 mmHg,PCO,2,22 mmHg,Pulse130/min,PO,2,92 mmHgRR40/min,HCO,3,9 mmol/L,VT800ml,BE-30 mmol/LMV32L,Step 4:,Determine if there is a compensatory mechanism working,to try to correct the pH.,四步法分析结果,酸碱平衡调节机制,体内酸碱的绝对量时时刻刻都在变动，,pH、HCO,3,-,和H,2,CO,3,三者的关系,人体通过化学缓冲、离子交换、肺代偿、肾代偿四种基本形式，将PH值维持在一个狭窄的生理范围内。,HCO3-,pH=6.1+log-,H2CO3,缓冲系,离子交换,2Na,+,1H,+,3K,+,3K,+,2Na,+,1H,+,血液中H,+,升高时,血液中H,+,降低时,肺代偿,约98%正常代谢产生CO,2，,是体内酸的主要来源，由肺脏排出。,CO2 +H2O,H2CO3,机体通过调节CO,2,的排出量，从而维持酸碱平衡。,肾代偿,体内的固定酸及碱性物质必须经肾脏排出。主要有以下四种形式：,NaHCO,3,的再吸收,肾小管内缓冲盐的酸化,氨的分泌与铵盐的生成,钾的排泄与K,+,-Na,+,交换,肾脏调节酸碱平衡的作用强大，但需要（35）天才能达到最大代偿能力,什么是代偿,In respiratory conditions,therefore,the kidneys will,attempt to compensate and visa versa.,In chronic respiratory acidosis(COPD)the kidneys increase,the elimination of H,+,and absorb more HCO,3.,The ABG will,Show NL pH,CO,2,and HCO,3.,Buffers kick in within minutes.Respiratory compensation,is rapid and starts within minutes and complete within 24 hours.Kidney compensation takes hours and up to 5 days.,HCO3-,pH=6.1+log-,H2CO3,酸碱紊乱代偿预计值、所需时间,代偿公式 所需时间,代 酸,PCO,2,1.5,HCO,3,82.0 1224hr,代 碱,PCO,2,0.9,HCO,3,5,2436hr,急呼酸,HCO,3,0.1,PCO,2,3,510min,慢呼酸,HCO3=0.35pCO25.58,7296hr,急呼碱,HCO,3,0.2,PCO,2,2.5 510min,慢呼碱,HCO,3,0.49,PCO,2,1.72,7296hr,代偿极限：,代酸PCO,2,10mmHg,代碱PCO,2,55mmHg,呼酸acute:HCO,3,45mmol/L,chronic:HCO,3,30mmol/L,呼碱 acute:HCO,3,18mmol/L,chronic:HCO,3,12mmol/L,酸碱平衡失调代偿预计公式,Case Study No.1,56 yo,neurologic dz required ventilator support for several,weeks.She seemed most comfortable when hyperventilated,to PaCO,2,28-30 mmHg.She required daily doses of lasix to,assure adequate urine output and received 40 mmol/L IV K,+,each day.On 10th day of ICU her ABG on 24%oxygen&VS:,ABG Results,pH7.62,BP115/80 mmHg,PCO,2,30 mmHg,Pulse88/min,PO,2,85 mmHg,RR10/min,HCO,3,30 mmol/L,VT1000ml,BE10 mmol/LMV10L,K,+,2.5 mmol/L,analysis,代偿公式 所需时间,代 酸,PCO,2,1.5,HCO,3,82.0 1224hr,代 碱,PCO,2,0.9,HCO,3,5,2436hr,急呼酸,HCO,3,0.1,PCO,2,3,510min,慢呼酸,HCO3=0.35pCO25.58,7296hr,急呼碱,HCO,3,0.2,PCO,2,2.5 510min,慢呼碱,HCO,3,0.49,PCO,2,1.72,7296hr,analysis,代 碱,PCO20.9,HCO3 5,=0.9X(30-24)5=0.4-10.4mmHg,PCO2=40+,PCO2=40.450.4mmHg,Interpretation,:Acute alveolar hyperventilation,(resp.alkalosis)and metabolic alkalosis with corrected,hypoxemia.,Case study No.2,27 yo retarded,with insulin-dependent DM arrived at ER,from the institution where he lived.On room air ABG&VS:,pH7.15BP180/110 mmHg,PCO,2,22 mmHg,Pulse130/min,PO,2,92 mmHg,RR40/min,HCO,3,9 mmol/L,VT800ml,BE-30 mmol/LMV32L,analysis,代偿公式 所需时间,代 酸,PCO,2,1.5,HCO,3,82.0 1224hr,代 碱,PCO,2,0.9,HCO,3,5,2436hr,急呼酸,HCO,3,0.1,PCO,2,3,510min,慢呼酸,HCO3=0.35pCO25.58,7296hr,急呼碱,HCO,3,0.2,PCO,2,2.5 510min,慢呼碱,HCO,3,0.49,PCO,2,1.72,7296hr,Interpretation,:Partly compensated metabolic acidosis.,代 酸,1.5,HCO3+8,2.0,=1.5X(9-24)+8,2.0=-28.5-32.5mmHg,PCO2=40+,PCO2=11.57.5mmHg,Case study No.3,74 yo,with hx chronic renal failure and chronic diuretic therapy,was admitted to ICU comatose and severely dehydrated.On,40%oxygen her ABG&VS:,pH7.52BP130/90 mmHg,PCO,2,55 mmHg,Pulse120/min,PO,2,92 mmHg,RR25/min,HCO,3,42 mmol/L,VT150ml,BE17 mmol/LMV 3.75L,Interpretation,:Partly compensated metabolic alkalosis with,corrected hypoxemia.,代 碱,PCO20.9,HCO3,5=0.9x18,5,=11.2-21.2mmHg,Case study No.4,43 yo,arrives in ER 20 minutes after a MVA in which he,injured his face on the dashboard.He is agitated,has mottled,cold and clammy skin and has obvious partial airway obstruction.,An oxygen mask at 10 L is placed on his face.ABG&VS:,pH7.10BP150/110 mmHg,PCO,2,60 mmHgPulse150/min,PO,2,125 mmHgRR45/min,HCO,3,18 mmol/LVT?ml,BE-15 mmol/LMV?L,.,Interpretation,:Acute ventilatory failure(resp.acidosis)and,acute metabolic acidosis with corrected hypoxemia,急呼酸,HCO30.1,PCO2,3,=0.1X20,3,=-15mmol/L,Case study No.5,17 yo,48 kg,with known insulin-dependent DM came to ER,with Kussmaul breathing and irregular pulse.Room air,ABG&VS:,pH7.05BP140/90 mmHg,PCO,2,12 mmHgPulse118/min,PO,2,108 mmHgRR40/min,HCO,3,5 mmol/LVT1200ml,BE-30 mmol/LMV48L,Interpretation:,Severe partly compensated metabolic,acidosis without hypoxemia.,代 酸,PCO21.5,HCO3+8,2.0=1.5X-19+8,2.0=-34.5-38.5mHg,Case study No.6,男性，65岁，COPD伴感染,PH,PaCO,2,HCO,3,-,K,+,Na,+,Cl,-,AG,PaO,2,FiO,2,7.36,7.8（,58,）,32,3.2,135,92,11,8.9（67）,0.29,分析：患者为,COPD,伴感染，临床上以慢性呼酸最常见。结合病人,PH,、,PaCO,2,、,HCO,3,-,变化，,PH,和,PaCO,2,一致，应诊断为,慢性呼酸。是单纯性还是混合性，根据慢性呼酸公式：,HCO,3,-,=PaCO,2,0.35,5.58,HCO,3,-,=,（,58-40,）,0.35,5.58,=180.35,5.58,=0.8211.88mmol/L,预测,HCO,3,-,实际,HCO,3,-,，而,AG,正常。,诊断为单纯性慢性呼酸,Case study No.7,67 yo,who had closed reduction of leg fx without incident.,Four days later she experienced a sudden onset of severe chest,pain and SOB.Room air ABG&VS:,pH7.36BP130/90 mmHg,PCO,2,33 mmHgPulse100/min,PO,2,55 mmHgRR25/min,HCO,3,18 mmol/L,BE-5 mmol/LMV18L,SaO,2,88%,Interpretation:,Compensated metabolic acidosis with,moderate hypoxemia.Dx:PE,代 酸,PCO21.5,HCO3+8,2.0=1.5X-6+8,2.0=-15-19mmHg,男性，23岁，外伤后失血性休克，无尿。,PH,PaCO,2,HCO,3,-,K,+,Na,+,Cl,-,AG,PaO,2,FiO,2,7.19,6.1（46）,17,3.4,124,94,13,13.1（98）,0.25,分析：患者有休克、无尿，临床应考虑有代酸存在，结合病人PH,与,HCO,3,-,一致，故可诊断为代酸。,根据代酸公式：PaCO,2,=HCO,3,-,（0.150.02），病人PaCO,2,应在4.114.39 Kpa，而实际PaCO,2,为6.1Kpa，说明还存在呼酸。,Case study No.8,诊断为代酸合并呼酸,AG,的概念,血清中常规测得的阳离子总和与阴离子总和之差,AG=Na,+,HCO,3,Cl,12 4mmol/L,Na,+,UCCl,-,+HCO,3,-,+UA,AGUAUC,重要性：协助判断代酸和,血气指标不能揭示的复合性酸碱失衡,AG30mmol/L，,肯定酸中毒,AG2030mmol/L，酸中毒可能性大,AG1719mmol/L，少数病例酸中毒,AG 增 高 或 减 低 的 原 因,AG 16mmol/L,未检测阴离子浓度,如,代酸,严重稀释性低Na和低,严重代碱,蛋白血症,含阴离子抗生素如羧苄 青,血Cl估计过高，如高,含Na强酸盐(不包括盐酸盐),脂血症或溴化物中毒,血Na估计过低，如高,血浓缩,Na血症或血粘度,其它阳离子,如Ca,+,、Mg,+,严重高Cl,性代酸,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,ABG Interpretation,Compensated,Respiratory,Alkalosis,CO2,More Abnormal,Respiratory,Alkalosis,CO2,Expected,Mixed,Respiratory,Metabolic,Alkalosis,CO2,Less Abnormal,CO2 Change,c/w,Abnormality,Metabolic,Alkalosis,CO2,Normal,Compensated,Metabolic,Alkalosis,CO2 Change,opposes,Abnormality,Alkalosis,ABG Interpretation,谢谢,Practice ABGs,PaO,2,90SaO,2,95 pH 7.48 PaCO,2,32 HCO,3,24,PaO,2,60SaO,2,90 pH 7.32 PaCO,2,48 HCO,3,25,PaO,2,95SaO,2,100 pH 7.30 PaCO,2,40 HCO,3,18,PaO,2,87SaO,2,94 pH 7.38 PaCO,2,48 HCO,3,28,PaO,2,94SaO,2,99 pH 7.49 PaCO,2,40 HCO,3,30,6.PaO,2,62SaO,2,91 pH 7.35 PaCO,2,48 HCO,3,27,PaO,2,93SaO,2,97 pH 7.45 PaCO,2,47 HCO,3,29,PaO,2,95SaO,2,99 pH 7.31 PaCO,2,38 HCO,3,15,PaO,2,65SaO,2,89 pH 7.30 PaCO,2,50 HCO,3,24,10.PaO,2,110SaO,2,100 pH 7.48 PaCO,2,40 HCO,3,30,Answers to Practice ABGs,Respiratory alkalosis,Respiratory acidosis,Metabolic acidosis,Compensated Respiratory acidosis,Metabolic alkalosis,Compensated Respiratory acidosis,Compensated Metabolic alkalosis,Metabolic acidosis,Respiratory acidosis,Metabolic alkalosis,