動脈血氣分析(英)

1、ABG INTERPRETATION,Debbie Sander PAS-II,Objectives,What’s an ABG? Understanding Acid/Base Relationship General approach to ABG Interpretation Clinical causes Abnormal ABG’s Case studies Take home,What is an A

2、BG,Arterial Blood GasDrawn from artery- radial, brachial, femoralIt is an invasive procedure.Caution must be taken with patient on anticoagulants.Helps differentiate oxygen deficiencies from primary ventilatory

3、deficiencies from primary metabolic acid-baseabnormalities,What Is An ABG?,pH[H+]PCO2 Partial pressure CO2PO2 Partial pressure O2HCO3 BicarbonateBE Base excessSaO2 Oxygen Saturation,,Acid/Base

4、Relationship,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.

5、1,60 y/o male comes ER c/o SOB.Tachypneic, tachycardic, diaphoretic andCyanotic. Dx acute resp. failure and ABG’sShow PaCO2 well below nl, pH above nl, PaO2 is very low. The blood gas documentResp. failure due to pr

6、imary O2 problem.,Case Study No. 2,,60 y/o male comes ER c/o SOB.Tachypneic, tachycardic, diaphoretic andCyanotic. Dx acute resp. failure and ABG’sShow PaCO2 very high, low pH and PaO2is moderately low. The blood gas

7、 documentResp. failure due to primarily ventilatoryinsufficiency.,There are two buffers that work in pairsH2CO3NaHCO3Carbonic acid base bicarbonate These buffers are linked to the respiratory and re

8、nal compensatory system,Buffers,,Respiratory Component,function of the lungs Carbonic acid H2CO3 Approximately 98% normal metabolites are in the form of CO2 CO2 + H2O ? H2CO3 excess

9、 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 from the renal tubules1) ac

10、tive exchange Na+ for H+ between the tubular cells and glomerular filtrate2) carbonic anhydrase is an enzyme that accelerates hydration/dehydration CO2 in renal epithelial cells,H2

11、O + CO2 ? H2CO3 ? HCO3 + H+,Acid/Base Relationship,,Normal ABG values,pH7.35 – 7.45PCO235 – 45 mmHgPO280 – 100 mmHgHCO322 – 26 mmol/LBE-2 - +2SaO2>95%,AcidosisAlkal

12、osis,pH 45HCO3< 22,pH> 7.45PCO2 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 dru

13、g overdose narcosis respiratory arrest airway obstruction,Metabolic Acidosis,failure of kidney function ? blood HCO3 which results in ? availability of renal tubular HCO3 for H+ excretion pH < 7.35 HCO

14、3 < 22,Causes of Metabolic Acidosis,renal failure diabetic ketoacidosis lactic acidosis excessive diarrhea cardiac arrest,Respiratory Alkalosis,too much CO2 exhaled (hyperventilation) ? PCO2, H2CO3 insuffici

15、ency = ? pH pH > 7.45 PCO2 < 35,Causes of Respiratory Alkalosis,hyperventilation panic d/o pain pregnancy acute anemia salicylate overdose,Metabolic Alkalosis,? plasma bicarbonate pH > 7.45 HCO

16、3 > 26,Causes of Metabolic Alkalosis,? loss acid from stomach or kidney hypokalemia excessive alkali intake,How to Analyze an ABG,PO2NL = 80 – 100 mmHg2. pHNL = 7.35 – 7.45Acidotic7.45PCO2NL =

17、 35 – 45 mmHgAcidotic>45Alkalotic 26,Four-step ABG Interpretation,Step 1: Examine PaO2 & SaO2 Determine oxygen status Low PaO2 (<80 mmHg) & SaO2 means hypoxia NL/elevated oxygen means ade

18、quate oxygenation,Step 2: pHacidosis7.45,,,Four-step ABG Interpretation,Step 3: study PaCO2 & HCO 3 respiratory irregularity if PaCO2 abnl & HCO3 NL metabolic irregularity if HCO3 abnl & PaCO2 NL,F

19、our-step ABG Interpretation,,Step 4:Determine if there is a compensatory mechanism workingto try to correct the pH.ie: if have primary respiratory acidosis will have increasedPaCO2 and decreased pH. Compensation

20、 occurs whenthe kidneys retain HCO3.,Four-step ABG Interpretation,~ PaCO2 – pH Relationship,,807.20607.30407.40307.50207.60,,,,Compensated,Respiratory,Acidosis,,,CO2,More Abnormal,,,,Respiratory,Acidos

21、is,,,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,,,Ac

22、idosis,ABG Interpretation,,,,,,,,,Compensated,Respiratory,Alkalosis,,,CO2,More Abnormal,,,,Respiratory,Alkalosis,,CO2,Expected,,,Mixed,Respiratory,Metabolic,Alkalosis,,CO2,Less Abnormal,,CO2 Change,c/w,Abnormality,,,Meta

23、bolic,Alkalosis,,CO2,Normal,,,Compensated,Metabolic,Alkalosis,,,CO2 Change,opposes,Abnormality,,,Alkalosis,ABG Interpretation,Respiratory Acidosis,pH7.30 PaCO2 60 HCO3 26,Respiratory Alkalosis,pH7.50 PaCO2

24、 30 HCO3 22,Metabolic Acidosis,pH7.30 PaCO2 40 HCO3 15,Metabolic Alkalosis,pH7.50 PCO2 40 HCO3 30,What are the compensations?,Respiratory acidosis?metabolic alkalosisRespiratory alkal

25、osis?metabolic acidosisIn respiratory conditions, therefore, the kidneys willattempt to compensate and visa versa.In chronic respiratory acidosis (COPD) the kidneys increasethe elimination of H+ and absorb more H

26、CO3. The ABG willShow NL pH, ?CO2 and ?HCO3.Buffers kick in within minutes. Respiratory compensationis rapid and starts within minutes and complete within 24 hours. Kidney compensation takes hours and up to 5 days.

27、,Mixed Acid-Base Abnormalities,Case Study No. 3:56 yo ? ? neurologic dz required ventilator support for severalweeks. She seemed most comfortable when hyperventilatedto PaCO2 28-30 mmHg. She required daily doses

28、 of lasix toassure 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,pH7.62BP115/80 mmHgPCO230 mmHgPulse88/minPO285 mmHgRR10/min

29、HCO330 mmol/LVT1000mlBE10 mmol/LMV10LK+2.5 mmol/L,Interpretation:Acute alveolar hyperventilation (resp. alkalosis) and metabolic alkalosis with corrected hypoxemia.,Case study No. 4,27 yo retarded ? with in

30、sulin-dependent DM arrived at ERfrom the institution where he lived. On room air ABG & VS:pH7.15BP180/110 mmHgPCO222 mmHgPulse130/minPO292 mmHgRR40/minHCO3 9 mmol/LVT800mlBE-30 mmol/LMV32

31、L,Interpretation:Partly compensated metabolic acidosis.,Case study No. 5,74 yo ? with hx chronic renal failure and chronic diuretic therapywas admitted to ICU comatose and severely dehydrated. On40% oxygen her ABG &a

32、mp; VS:pH7.52BP130/90 mmHgPCO255 mmHgPulse120/minPO292 mmHgRR25/minHCO342 mmol/LVT150mlBE17 mmol/LMV 3.75L,Interpretation:Partly compensated metabolic alkalosis with corrected hypoxemia.,Case

33、 study No. 6,43 yo ? arrives in ER 20 minutes after a MVA in which heinjured 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

34、 L is placed on his face. ABG & VS:pH7.10BP150/110 mmHgPCO260 mmHgPulse150/minPO2125 mmHgRR45/minHCO318 mmol/LVT? mlBE-15 mmol/LMV? L.,Interpretation:Acute ventilatory failure (resp. aci

35、dosis) andacute metabolic acidosis with corrected hypoxemia,Case study No. 7,17 yo, 48 kg ? with known insulin-dependent DM came to ERwith Kussmaul breathing and irregular pulse. Room airABG & VS:pH7.05BP1

36、40/90 mmHgPCO212 mmHgPulse118/minPO2108 mmHgRR40/minHCO35 mmol/LVT1200mlBE-30 mmol/LMV48L,Interpretation:Severe partly compensated metabolicacidosis without hypoxemia.,Case No. 7 cont’d,This patient

37、 is in diabetic ketoacidosis.IV glucose and insulin were immediately administered. Ajudgement was made that severe acidemia was adverselyaffecting CV function and bicarb was elected to restore pH to? 7.20.Bicarb ad

38、ministration calculation:Base deficit X weight (kg) 430 X 48 = 360 mmol/LAdmin 1/2 over 15 min & 4 repeat ABG,Case No. 7 cont’d,ABG result after bicarb:pH7.27BP130/80 mmHgPCO225

39、 mmHgPulse100/minPO292 mmHgRR22/minHCO311 mmol/LVT600mlBE-14 mmol/LMV13.2L,Case study No. 8,47 yo ? was in PACU for 3 hours s/p cholecystectomy. Shehad been on 40% oxygen and ABG & VS:pH7.44

40、BP130/90 mmHgPCO232 mmHgPulse95/min, regularPO2121 mmHgRR20/minHCO322 mmol/LVT350mlBE-2 mmol/LMV7LSaO298%Hb13 g/dL,Case No. 8 cont’d,Oxygen was changed to 2L N/C. 1/2 hour pt. ready to be D/Cto

41、 floor and ABG & VS:pH7.41BP130/90 mmHgPCO210 mmHgPulse95/min, regularPO2148 mmHgRR20/minHCO36 mmol/LVT350mlBE-17 mmol/LMV7LSaO299%Hb7 g/dL,Case No. 8 cont’d,What is going on?,Case No.

42、8 cont’d,If the picture doesn’t fit, repeat ABG!!pH7. 45BP130/90 mmHgPCO231 mmHgPulse95/minPO287 mmHgRR20/minHCO322 mmol/LVT350mlBE-2 mmol/LMV7LSaO2 96% Hb13 g/dL,Technical error was presum

43、ed.,Case study No. 9,67 yo ? who had closed reduction of leg fx without incident.Four days later she experienced a sudden onset of severe chestpain and SOB. Room air ABG & VS:pH7.36BP130/90 mmHgPCO233 mmH

44、gPulse100/minPO255 mmHgRR25/minHCO318 mmol/LBE-5 mmol/LMV18LSaO288%,Interpretation:Compensated metabolic acidosis withmoderate hypoxemia. Dx: PE,Case study No. 10,76 yo ? with documented chronic hype

45、rcapnia secondary tosevere COPD has been in ICU for 3 days while being tx forpneumonia. She had been stable for past 24 hours and wastransferred to general floor. Pt was on 2L oxygen & ABG &VS:pH7.44BP

46、135/95 mmHgPCO263 mmHgPulse110/minPO252 mmHgRR22/minHCO342 mmol/LBE+16 mmol/LMV10LSaO286%.,Interpretation:Chronic ventilatory failure (resp. acidosis)with uncorrected hypoxemia,Case No. 10 cont’d

47、,She was placed on 3L and monitored for next hour. She remained alert, oriented and comfortable. ABG wasrepeated:pH7.36BP140/100 mmHgPCO275 mmHgPulse105/minPO265 mmHgRR24/minHCO342 mmol/LBE+16

48、mmol/LMV4.8LSaO292%.,Pt’s ventilatory pattern has changed to more rapid andshallow breathing. Although still acceptable the pH andCO2 are trending in the wrong direction. High-flow oxygen may be better for thi

49、s pt to prevent intubation,Take Home Message:,,Valuable information can be gained from an ABG as to the patients physiologic condition Remember that ABG analysis if only part of the patient assessment. Be syst

50、ematic with your analysis, start with ABC’s as always and look for hypoxia (which you can usually treat quickly), then follow the four steps. A quick assessment of patient oxygenation can be achieved with a

51、 pulse oximeter which measures SaO2.,It’s not magic understanding ABG’s, it just takes a little practice!,Any Questions?,References,Shapiro, Barry A., et al; Clinical Application of BloodGases; 19942. American Jour

52、nal of Nursing1999;Aug99(8):34-63. Journal Post Anesthesia Nursing1990;Aug;5(4)264-724. Irvine, David;ABG Interpretation, A Rough and DirtyProduction,Practice ABG’s,PaO2 90SaO295 pH 7.48 PaCO2 32

53、 HCO3 24PaO2 60SaO290 pH 7.32 PaCO2 48 HCO3 25PaO2 95SaO2100 pH 7.30 PaCO2 40 HCO3 18PaO2 87SaO2 94 pH 7.38 PaCO2 48 HCO3 28PaO2 94SaO2 99

54、 pH 7.49 PaCO2 40 HCO3 306. PaO2 62SaO2 91 pH 7.35 PaCO2 48 HCO3 27PaO2 93SaO2 97 pH 7.45 PaCO2 47 HCO3 29PaO2 95SaO2 99 pH 7.31 PaCO2 38

55、 HCO3 15PaO2 65SaO2 89 pH 7.30 PaCO2 50 HCO3 2410. PaO2 110SaO2 100 pH 7.48 PaCO2 40 HCO3 30,Answers to Practice ABG’s,Respiratory alkalosisRespiratory acidosisMetabolic a