英文血气分析精美

1,血气分析及酸碱失衡判断 Arterial Blood Gas Analysis and acid-base imbalance judgement,2,血气分析的意义,1、了解氧气的供应 是否存在呼吸衰竭及分型2、判断体内酸碱平衡的情况3、是反映肺脏和肾脏功能以及评估治疗效果的重要指标4、危重患者抢救和手术中监护的重要指标之一 多用动脉血做血气分析,3,肺内气体交换模式图,4,肾脏重吸收HCO3-原理,5,一、血气分析指标,1、动脉血氧分压(partial pressure of oxygen PaO2)：2、肺泡动脉氧分压差（P(A-a)O2）：3、pH (Potential of Hydrogen)4、动脉血二氧化碳分压（ partial pressure of carbon dioxide PaCO2）5、碳酸氢盐（HCO3 Bicarbonate）6、动脉血氧饱和度（SaO2 Oxygen saturation ）7、剩余碱（ Base Excess, BE）8、缓冲碱（buffer bases, BB)9、血浆CO2含量（total plasma CO2, T-CO210、阴离子间隙（AG）：,6,一、血气分析指标,1、动脉血氧分压(partial pressure of oxygen PaO2)：动脉血液中物理溶解氧分子所产生的压力。 正常范围80-100mmHg (12.613.3kPa）随年龄增加氧分压可有所下降 (102-0.33*年龄10) mmHg低于同年龄人正常值下线为低氧血症（hypoxaemia）轻度：80-60mmHg 中度：60-40mmHg 重度:7.45为碱血症，即失代偿性碱中毒。 pH 50mmHg为肺泡通气不足，见于呼吸性酸中毒（respiratory acidosis），型呼衰； （2）当PaCO2 SB ; 呼碱时AB 27mmol/L时,可为代谢性碱中毒;,11,6、动脉血氧饱和度（SaO2 Oxygen saturation ）： 动脉血氧与血红蛋白的结合程度，是单位血红蛋白含氧百分数。正常值97%以上，最高100%。,12,7、剩余碱（Base Excess, BE）：用酸或碱滴定血浆到PH7.4时，消耗的酸或碱的量。反映代谢性酸碱平衡失调。正常值：3mmol/L正值：说明需用酸滴定才能使血浆中的PH为7.4。表明血浆中固定碱增加。负值：说明需用碱滴定才能使血浆中的PH为7.4。表明血浆中固定酸增加。,13,8、缓冲碱（buffer bases,BB),是指血液中一切具有缓冲作用的碱性物质的总和，包括HCO3-,Hb-，和血浆蛋白等，是反映代谢性因素的指标。正常值：45-55mmol/L, 平均50mmol/L意义：反映机体对酸碱平衡失调时总的缓冲能力，不受呼吸的影响。BB减少提示代谢性酸中毒，BB增加提示代谢性碱中毒,14,9、血浆CO2含量（total plasma CO2, T-CO2,指血浆中结合的和物理溶解的CO2的总含量。正常值：25.2mmol/L，基本上反映的是HCO3的含量受呼吸和代谢因素的影响，呼酸和代碱时T-CO2增加，呼碱或代酸时T-CO2降低。,15,10、阴离子间隙（AG）： 指血浆中未测定的阴离子与未测定阳离子的差值。Na 未测定阳离子 HCO3-CL- 未测定阴离子AGNa（HCO3-CL- ）AG16mmol/L，不论PH高或低，就可诊断代酸,16,二、酸碱平衡的调节,机体代谢产生固定酸和挥发酸，但是由于体内 1.化学缓冲系统 2.细胞内外电解质的交换 3.肺肾的生理调节机制 允许pH值在7.357.45狭窄范围内变动，保证人体组织细胞赖以生存的内环境的稳定。,17,1. 缓冲系统： 碳酸氢盐缓冲系（NaHCO3 / H2CO 3 ） 磷酸盐缓冲系 (Na2HPO4 / NaH2PO4) 血浆蛋白缓冲系 血红蛋白缓冲系 其中最重要的是碳酸氢盐缓冲系统： 缓冲能力大，占全血缓冲总量50%，血浆 缓冲量的35%； 它通过CO2与肺、通过HCO3与肾相关联； NaHCO3 / H2CO3的比值决定pH值。,18,2. 细胞内外液电解质交换： 酸中毒：细胞外液2Na+1H+进入细胞内，细胞 的3k+进入细胞外。 硷中毒、低血钾或高血钾原理相同。 呼酸时还出现一种变化，红细胞内产生H2CO3增多，解离的HCO3与细胞外液Cl进行交换，缓解细胞外酸中毒。,19,3.肺在呼吸性酸碱平衡失调中的调节过程 当固定酸和非固定酸增加时NaHCO3，脑脊液的H+增加，呼吸中枢兴奋，呼吸加深加快，CO2排出增加，使NaHCO3 / H2CO3比值仍在20/1, pH值保持在正常范围。 肺调节到达完全代偿所需时间约36h。,20,4. 肾在呼吸性酸碱平衡失调中的调节过程： 呼酸时H2CO3,肾脏通过下列途径代偿，使NaHCO3,确保NaHCO3 / H2CO3比值仍在20/1, pH值在正常范围。 泌H+排酸 泌氨中和酸 HCO3 再吸收 肾调节到达完全代偿所需时间57d。,21,酸碱平衡失调类型,呼吸性酸中毒 respiratory acidosis呼吸性碱中毒 respiratory alkalosis代谢性酸中毒 metabolic acidosis 代谢性碱中毒 metabolic alkalosis混合性酸碱平衡紊乱Mixed acid-base balance disorder,22,1、呼吸性酸中毒,概念：由于呼吸功能障碍（包括肺泡通气或换气功能障碍），引起CO2潴留，PaCO2 ，PH 的高碳酸血症。病因：慢性阻塞性肺疾病、严重哮喘呼吸中枢受抑制：如麻醉镇静药物残留。胸廓功能障碍：膈肌麻痹、胸廓病变（如连枷胸）、神经、神经肌肉接头病变、疼痛影响。气道梗阻：误吸、喉痉挛、呼吸道分泌物堵塞及痉挛等。肺部病变：大面积肺炎、肺栓塞、ARDS等。心脏病变：左心衰竭呼吸机呼吸参数设计不合理。,23,呼吸性酸中毒,引起呼酸的几种常见疾病慢性阻塞性肺疾病、严重哮喘睡眠呼吸暂停综合征格林巴利综合征脊髓灰质炎重症肌无力（胸腺瘤）周期性麻痹ARDS连枷胸等,24,呼吸性酸中毒,急性呼酸临床表现主要由于CO2潴留及缺氧高碳酸血症 高K 室颤缺氧 紫绀、神志障碍（呼吸性脑病）,25,呼吸性酸中毒,慢性呼酸临床表现循环：血压，颅压，肺动脉高压呼吸：初始刺激呼吸，PaCO290mmHg，CO2麻醉；紫绀，气促胸闷等中枢：头痛，神志障碍，初始兴奋，后抑制植物神经：交感神经兴奋,26,呼吸性酸中毒,诊断：PaCO2 ，PH 急性呼酸：PaCO21mmHg，HCO3 0.1mmol /L，最高不超过32mmol/L.慢性呼酸：PaCO21mmHg，HCO3 0.4mmol /L,最高不超过45mmol/L.若PaCO2 1mmHg， HCO3 介于0.10.35mmol /L，肾脏未完全代偿,27,呼吸性酸中毒,治疗建立通畅气道（清除呼吸道分泌物、应用支气管扩张药物、气管切开、插管等）氧疗增加有效肺泡通气量，改善高碳酸血症；合理使用呼吸兴奋剂；机械通气（调整呼吸机参数）纠正酸碱平衡失调和电解质紊乱：血钾如不是过高，不必急于处理；PH预期值，合并呼酸 PaCO27.45、 HCO3 28mmol/L，同时PaCO2代偿性升高代碱大都同时有低钾、低氯,42,代谢性碱中毒,治疗治疗原发病 补充氯和钾，予精氨酸，停止服用利尿剂、停止或减少应用糖皮质激素25%精氨酸(ml)BE正值0.3体重（kg) 0.9,43,混合性酸碱平衡紊乱,44,血气分析简易判定方法,45,主要看三个指标,pH值PaC02HC03-,46,一、看pH ：定酸血症或碱血症（酸或碱中毒）,47,二、判定哪个因素是原发的，哪个是继发的（经典判断方法+结合临床） 原发性HCO3增多或减少是代谢性碱或酸中毒的特征 代硷：低钾低氯; 代酸：1.产酸多：乳酸、酮体; 2.获酸多：阿司匹林； 3.排酸障碍：肾脏病; 4.失碱：腹泻等导致酸中毒;原发性CO2增多或减少是呼吸性酸或碱中毒的特征,48,三、看“继发性变化”：是否符合代偿调节规律定单纯性或混合性酸碱紊乱。,49,例1.败血症并发感染中毒性休克患者的血气指标为：pH 7.32, PaO2 80mmHg，PaCO2 20mmHg, HCO310mmol/L。实测PaCO2 预计PaCO2 诊断：代酸合并呼碱,50,例2.过度换气8天者，不能进食，每日输葡萄糖和盐水，血气为：pH 7.59, PaCO2 20mmHg , HCO323mmol/L。 预计HCO316可能有代酸，AG30 mmol/L肯定有代酸。根据AG将代谢性酸中毒分为2类：高AG,正常血氯性代谢性酸中毒。高血氯,正常AG性代谢性酸中毒。,52,当高AG性代酸时，AG的升高数恰好等于HCO3的下降值时，既AG=HCO3 ，于是由AG派生出一个潜在 HCO3 的概念。 2、 潜在HCO3 =AG+实测HCO3 。当潜在HCO3 预计HCO3示有代碱存在。,53,AG在三重酸碱失调中应用判断步骤：确定呼酸/呼碱 计算AG定代酸 计算潜在HCO3 预计值HCO3定代碱。,54,AG在三重酸碱失调中应用例1.呼酸型（呼酸、代酸合并代碱） 某肺心病，呼吸衰竭合并肺性脑病者，用利尿剂和激素等治疗，血气电解质为：pH7.33, PaCO261mmHg, HCO38mmol/L，Na+140mmol/L，Cl 74mmol/L，K+ 3.5mmol/L。 按前述3步骤：原发性变化定呼酸 AG=140-38-73=28 定代酸 计算潜在HCO3 潜在HCO3=28-16+38=50 潜在HCO3预计值HCO3 = 50 32 定代碱。,55,例2. 呼碱型（呼碱、代酸和并代碱） 某冠心病左心衰患者合并肺部感染、呼吸困难3天而住院，血气电解质为：pH7.7, PaCO216.6mmHg , HCO320mmol/L，Na+ 120mmol/L，Cl70mmol/L。 按前述3步骤： 原发性变化 定呼碱 AG=120-70-20=30 定代酸 计算潜在HCO3 潜在HCO3=实测HCO3- +AG=20+14=34 潜在HCO3 预计值HCO3 = 3412 定代碱。,56,酸碱失衡的治疗,呼吸性酸中毒：改善通气，谨慎补碱呼吸性碱中毒：呼吸机管理，口鼻面罩代谢性酸中毒：补充NaCO3代谢性碱中毒: 补钾、氯化铵、盐酸精氨酸,57,ABG,Blood gas analysis, also called arterial blood gas (ABG) analysis, is a test which measures the amount of oxygen (O2) and carbon dioxide ( CO2) in the blood, as well as the acidity (pH) of the blood.,58,PurposeAn ABG analysis evaluates how effectively the lungs are delivering oxygen to the blood and how efficiently they are eliminating carbon dioxide from it. The test also indicates how well the lungs and kidneys are interacting to maintain normal blood pH (acid-base balance).,59,Blood gas studies are usually done to assess respiratory disease and other conditions that may affect the lungs, and to manage patients receiving oxygen therapy (respiratory therapy).In addition, the acid-base component of the test provides information on kidney function too.,60,An ABG is typically requested to determine the pH of the blood and the partial pressures of carbon dioxide (PaCO2) and oxygen (PaO2) within it.It is used to assess the effectiveness of gaseous exchange and ventilation, be it spontaneous or mechanical. If the pH becomes deranged, normal cell metabolism is affected.,61,The ABG allows patients metabolic status to be assessed too, giving an indication of how they are coping with their illness. It would therefore seem logical to request an ABG on any patient who is or has the potential to become critically ill. This includes patients in critical care areas and those on wards who trigger early-warning scoring systems.,62,Information provided by an ABG,PaCO2This is the partial pressure of carbon dioxide dissolved within the arterial blood. It is used to assess the effectiveness of ventilation. A high PaCO2 (respiratory acidosis) indicates underventilation, a low PaCO2 (respiratory alkalosis) indicates hyper- or overventilation. The normal range for a healthy person is 4.7-6.0 kPa or 35-45 mmHg although in chronic pulmonary diseases it may be considerably higher and still normal for that patient.,63,PaO2This is the partial pressure of oxygen dissolved within the arterial blood and will determine oxygen binding to haemoglobin (SaO2). It is of vital importance but is not used in determining patients acid base status and normally low readings indicate hypoxaemia.The normal range -9.3-13.3 kPa or 80-100 mmHg.,64,SaO2 Oxygen saturation measures how much of the haemoglobin (Hb) in the red blood cells is carrying oxygen (O2). Although similar to SpO2 (measured by a pulse oximeter), it is more accurate. The normal levels are 97% and above, although levels above 90% are often acceptable in critically ill patients.,65,pH (Potential of Hydrogen)The pH measures hydrogen ions (H+) in blood. The pH of blood usually between 7.35 to 7.45. A pH of less than 7.0 is called acid and a pH greater than 7.0 is called basic (alkaline). So blood is slightly basic.,66,HCO3 (Bicarbonate)Bicarbonate is a chemical (buffer) that keeps the pH of blood from becoming too acidic or too basic & indicates whether a metabolic problem is present (such as ketoacidosis). A low HCO3- indicates metabolic acidosis, a high HCO3- indicates metabolic alkalosis. HCO3- levels can also become abnormal when the kidneys are working to compensate for a respiratory issue so as to normalize the blood pH. Normal range - 2226 mmol/l,67,Base Excess (BE)The base excess is used for the assessment of the metabolic component of acid-base disorders, and indicates whether the patient has metabolic acidosis or metabolic alkalosis.,68,A negative base excess indicates that the patient has metabolic acidosis (primary or secondary to respiratory alkalosis). A positive base excess indicates that the patient has metabolic alkalosis (primary or secondary to respiratory acidosis). Normal range - -3 to +3 mmol/l,69,Normal results,partial pressure of oxygen (PaO2): 80-100 mm Hg partial pressure of carbon dioxide (PaCO2): 35-45 mm Hg oxygen saturation (SaO2): 94-100% bicarbonate (HCO3): 22-26 mEq/LpH: 7.35-7.45,70,When ABG is ordered?,Blood gas tests are ordered when you have symptoms of an O2/CO2 or pH imbalance, such as difficulty breathing or shortness of breath & also if you are known to have a respiratory, metabolic, or kidney disease and those are experiencing respiratory distress to evaluate oxygenation and acid/base balance. Patients who are “on oxygen” (have supplemental oxygen) may have their blood gases measured at intervals to monitor the effectiveness of treatment.,71,Also be ordered for patients with head or neck trauma, injuries that may affect breathing. Patients undergoing prolonged anesthesia particularly for cardiac bypass surgery or brain surgery may have their blood gases monitored during and for a period after the procedure.,72,Checking the blood gases from the umbilical cord of newborns may uncover respiratory problems as well as determine the babys acid/base status. Testing is usually only done if a newborns condition indicates that he or she may be having difficulty breathing.,73,Respiratory Acidosis,Respiratory acidosis is characterized by a lower pH and an increased PCO2 and is due to respiratory depression (not enough oxygen in and CO2 out). This can be caused by many things, including pneumonia, chronic obstructive pulmonary disease (COPD), and over-sedation from narcotics.,74,Respiratory Alkalosis,Respiratory alkalosis, characterized by a raised pH and a decreased PCO2, is due to over ventilation caused by hyperventilating, pain, emotional distress, or certain lung diseases that interfere with oxygen exchange.,pH PCO2,75,Metabolic Acidosis,Metabolic acidosis is characterized by a lower pH and decreased HCO3-; the blood is too acidic on a metabolic/kidney level. Causes include diabetes, shock, and renal failure.,pH HCO3,76,Metabolic Alkalosis,Metabolic alkalosis is characterized by an elevated pH and increased HCO3- and is seen in hypokalemia, chronic vomiting (losing acid from the stomach), and sodium bicarbonate overdose.,pH HCO3,77,Extraction,Arterial blood for blood gas analysis is usually extracted by a phlebotomist, nurse, respiratory therapist or Dr. Blood is most commonly drawn from the radial artery because it is easily accessible, can be compressed to control bleeding, and has less risk for occlusion.,78,Extraction,The femoral artery (or less often, the brachial artery) is also used, especially during emergency situations or with children. Blood can also be taken from an arterial catheter already placed in one of these arteries.,79,80,Extraction and analysis,The syringe is pre-packaged and contains a small amount of heparin, to prevent coagulation or needs to be heparinised,