ICU必備1精選課件

1、Objectives Whats an ABG? Understanding Acid/Base Relationship General approach to ABG Interpretation Clinical causes Abnormal ABGs Case studies Take home第1頁，共54頁。What is an ABGArterial Blood GasDrawn from artery- radial, brachial, femoralIt is an invasive procedure.Caution must be taken with patient

2、 on anticoagulants.Helps differentiate oxygen deficiencies from primary ventilatory deficiencies from primary metabolic acid-baseabnormalities 第2頁，共54頁。What Is An ABG?pHH+PCO2 Partial pressure CO2PO2 Partial pressure O2HCO3 BicarbonateBE Base excessSaO2 Oxygen Saturation第3頁，共54頁。Acid/Base Relationsh

3、ip 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 第4頁，共54頁。Case Study No. 160 y/o male comes ER c/o SOB.Tachypneic, tachycardic, diaphoretic andCyanotic. Dx acute re

4、sp. failure and ABGsShow PaCO2 well below nl, pH above nl, PaO2 is very low. The blood gas documentResp. failure due to primary O2 problem. 第5頁，共54頁。Case Study No. 260 y/o male comes ER c/o SOB.Tachypneic, tachycardic, diaphoretic andCyanotic. Dx acute resp. failure and ABGsShow PaCO2 very high, low

5、 pH and PaO2is moderately low. The blood gas documentResp. failure due to primarily ventilatoryinsufficiency.第6頁，共54頁。There are two buffers that work in pairsH2CO3NaHCO3Carbonic acid base bicarbonate These buffers are linked to the respiratory and renal compensatory system Buffers第7頁，共54頁。Respirator

6、y Component 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 第8頁，共54頁。Metabolic Component Function of the kidneys base bicarbonate Na HCO3 Process of kidneys excreting H+ into the urine and reabsorbi

7、ng HCO3- into the blood from the renal tubules1) active 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 第9頁，共54頁。H2O + CO2 H2CO3 HCO3 + H+Acid/Base Relationship第10頁，共54頁。Norma

8、l ABG valuespH7.35 7.45PCO235 45 mmHgPO280 100 mmHgHCO322 26 mmol/LBE-2 - +2SaO295% 第11頁，共54頁。AcidosisAlkalosispH 45HCO3 7.45PCO2 26第12頁，共54頁。Respiratory Acidosis Think of CO2 as an acid failure of the lungs to exhale adequate CO2 pH 45 CO2+ H2CO3 pH第13頁，共54頁。Causes of Respiratory Acidosis emphysema

9、 drug overdose narcosis respiratory arrest airway obstruction第14頁，共54頁。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第19頁，共54頁。Causes of Metabolic Alkalosis loss acid from stomach or ki

10、dney hypokalemia excessive alkali intake第20頁，共54頁。How to Analyze an ABGPO2NL = 80 100 mmHg2. pHNL = 7.35 7.45Acidotic7.45PCO2NL = 35 45 mmHgAcidotic45Alkalotic35HCO3NL = 22 26 mmol/LAcidotic 26第21頁，共54頁。Four-step ABG InterpretationStep 1: Examine PaO2 & SaO2 Determine oxygen status Low PaO2 (80 mmHg

11、) & SaO2 means hypoxia NL/elevated oxygen means adequate oxygenation第22頁，共54頁。Step 2: pHacidosis7.45Four-step ABG Interpretation第23頁，共54頁。Step 3: study PaCO2 & HCO 3 respiratory irregularity if PaCO2 abnl & HCO3 NL metabolic irregularity if HCO3 abnl & PaCO2 NLFour-step ABG Interpretation第24頁，共54頁。S

12、tep 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 occurs whenthe kidneys retain HCO3. Four-step ABG Interpretation第25頁，共54頁。 PaCO2 pH Relationship807.20607.30407.40307.

13、50207.60第26頁，共54頁。CompensatedRespiratoryAcidosisCO2More AbnormalRespiratoryAcidosisCO2ExpectedMixedRespiratoryMetabolicAcidosisCO2Less AbnormalCO2 Changec/wAbnormalityMetabolicMetabolic AcidosisCO2NormalCompensatedMetabolicAcidosisCO2 ChangeopposesAbnormalityAcidosisABG Interpretation第27頁，共54頁。Compe

14、nsatedRespiratoryAlkalosisCO2More AbnormalRespiratoryAlkalosisCO2ExpectedMixedRespiratoryMetabolicAlkalosisCO2Less AbnormalCO2 Changec/wAbnormalityMetabolicAlkalosisCO2NormalCompensatedMetabolicAlkalosisCO2 ChangeopposesAbnormalityAlkalosisABG Interpretation第28頁，共54頁。Respiratory AcidosispH7.30 PaCO2

15、 60 HCO3 26 第29頁，共54頁。Respiratory AlkalosispH7.50 PaCO2 30 HCO3 22 第30頁，共54頁。Metabolic AcidosispH7.30 PaCO2 40 HCO3 15 第31頁，共54頁。Metabolic AlkalosispH7.50 PCO2 40 HCO3 30 第32頁，共54頁。What are the compensations?Respiratory acidosismetabolic alkalosisRespiratory alkalosismetabolic acidosisIn respiratory

16、 conditions, therefore, the kidneys willattempt to compensate and visa versa.In chronic respiratory acidosis (COPD) the kidneys increasethe elimination of H+ and absorb more HCO3. The ABG willShow NL pH, CO2 and HCO3.Buffers kick in within minutes. Respiratory compensationis rapid and starts within

17、minutes and complete within 24 hours. Kidney compensation takes hours and up to 5 days.第33頁，共54頁。Mixed Acid-Base AbnormalitiesCase 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 dos

18、es 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:第34頁，共54頁。ABG ResultspH7.62BP115/80 mmHgPCO230 mmHgPulse88/minPO285 mmHgRR10/minHCO330 mmol/LVT1000mlBE10 mmol/LMV10LK+2.5 mmol/L Interpretation:Acute alveolar hyperventilat

19、ion (resp. alkalosis) and metabolic alkalosis with corrected hypoxemia.第35頁，共54頁。Case study No. 427 yo retarded with insulin-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

20、/LMV32LInterpretation:Partly compensated metabolic acidosis.第36頁，共54頁。Case study No. 574 yo with hx chronic renal failure and chronic diuretic therapywas admitted to ICU comatose and severely dehydrated. On40% oxygen her ABG & VS:pH7.52BP130/90 mmHgPCO255 mmHgPulse120/minPO292 mmHgRR25/minHCO342 mmo

21、l/LVT150mlBE17 mmol/LMV 3.75LInterpretation:Partly compensated metabolic alkalosis with corrected hypoxemia.第37頁，共54頁。Case study No. 643 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 airw

22、ay obstruction.An oxygen mask at 10 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. acidosis) andacute metabolic acidosis with corrected hypoxemia第38頁，共54頁。Case study

23、No. 717 yo, 48 kg with known insulin-dependent DM came to ERwith Kussmaul breathing and irregular pulse. Room airABG & VS:pH7.05BP140/90 mmHgPCO212 mmHgPulse118/minPO2108 mmHgRR40/minHCO35 mmol/LVT1200mlBE-30 mmol/LMV48LInterpretation:Severe partly compensated metabolicacidosis without hypoxemia. 第3

24、9頁，共54頁。Case No. 7 contdThis patient 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 administration calculation:Base deficit X weight (kg)

25、 430 X 48 = 360 mmol/LAdmin 1/2 over 15 min & 4 repeat ABG第40頁，共54頁。Case No. 7 contdABG result after bicarb:pH7.27BP130/80 mmHgPCO225 mmHgPulse100/minPO292 mmHgRR22/minHCO311 mmol/LVT600mlBE-14 mmol/LMV13.2L第41頁，共54頁。Case study No. 847 yo was in PACU for 3 hours s/p cholecystectomy. Shehad been on 4

26、0% oxygen and ABG & VS:pH7.44BP130/90 mmHgPCO232 mmHgPulse95/min, regularPO2121 mmHgRR20/minHCO322 mmol/LVT350mlBE-2 mmol/LMV7LSaO298%Hb13 g/dL第42頁，共54頁。Case No. 8 contdOxygen was changed to 2L N/C. 1/2 hour pt. ready to be D/Cto floor and ABG & VS:pH7.41BP130/90 mmHgPCO210 mmHgPulse95/min, regularP

27、O2148 mmHgRR20/minHCO36 mmol/LVT350mlBE-17 mmol/LMV7LSaO299%Hb7 g/dL第43頁，共54頁。Case No. 8 contd What is going on?第44頁，共54頁。Case No. 8 contdIf the picture doesnt fit, repeat ABG!pH7. 45BP130/90 mmHgPCO231 mmHgPulse95/minPO287 mmHgRR20/minHCO322 mmol/LVT350mlBE-2 mmol/LMV7LSaO2 96% Hb13 g/dLTechnical e

28、rror was presumed.第45頁，共54頁。Case study No. 967 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 mmHgPulse100/minPO255 mmHgRR25/minHCO318 mmol/LBE-5 mmol/LMV18LSaO288% Interpr

29、etation:Compensated metabolic acidosis withmoderate hypoxemia. Dx: PE第46頁，共54頁。Case study No. 1076 yo with documented chronic hypercapnia 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

30、on 2L oxygen & ABG &VS:pH7.44BP135/95 mmHgPCO263 mmHgPulse110/minPO252 mmHgRR22/minHCO342 mmol/LBE+16 mmol/LMV10LSaO286%. Interpretation:Chronic ventilatory failure (resp. acidosis)with uncorrected hypoxemia第47頁，共54頁。Case No. 10 contdShe was placed on 3L and monitored for next hour. She remained ale

31、rt, oriented and comfortable. ABG wasrepeated:pH7.36BP140/100 mmHgPCO275 mmHgPulse105/minPO265 mmHgRR24/minHCO342 mmol/LBE+16 mmol/LMV4.8LSaO292%. Pts ventilatory pattern has changed to more rapid andshallow breathing. Although still acceptable the pH andCO2 are trending in the wrong direction. High

32、-flow oxygen may be better for this pt to prevent intubation第48頁，共54頁。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 systematic with your analysis, start with ABCs 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