医大ICU必备课件.ppt

Click to edit Master title style,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Objectives,Whats an ABG?,Understanding Acid/Base Relationship,General approach to ABG Interpretation,Clinical causes Abnormal,ABGs,Case studies,Take home,What is an ABG,Arterial Blood Gas,Drawn from artery-radial,brachial,femoral,It is an,invasive,procedure.,Caution must be taken with patient on anticoagulants.,Helps differentiate oxygen deficiencies from primary,ventilatory deficiencies from primary metabolic acid-base,abnormalities,What Is An ABG?,pHH,+,PCO,2,Partial pressure CO,2,PO,2,Partial pressure O,2,HCO,3,Bicarbonate,BE Base excess,SaO,2,Oxygen Saturation,Case Study No.2,60 y/o male comes ER c/o SOB.,Tachypneic,tachycardic,diaphoretic and,Cyanotic.Dx acute resp.failure and ABGs,Show PaCO,2,very high,low pH and PaO,2,is moderately low.The blood gas document,Resp.failure due to primarily ventilatory,insufficiency.,There are two buffers that work in pairs,H,2,CO,3,NaHCO,3,Carbonic acid base bicarbonate,These buffers are linked to the respiratory and renal compensatory system,Buffers,Respiratory Component,function of the lungs,Carbonic acid H,2,CO,3,Approximately 98%normal metabolites are in the form of CO,2,CO,2,+H,2,O,H,2,CO,3,excess CO,2,exhaled by the lungs,Metabolic Component,Function of the kidneys,base bicarbonate Na HCO,3,Process of kidneys excreting H,+,into the urine and reabsorbing HCO,3,-,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 CO,2,in renal epithelial cells,H,2,O +CO,2,H,2,CO,3,HCO,3,+H,+,Acid/Base Relationship,Normal ABG values,pH7.35 7.45,PCO,2,35 45 mmHg,PO,2,80 100 mmHg,HCO,3,22 26 mmol/L,BE-2-+2,SaO,2,95%,AcidosisAlkalosis,pH 45,HCO,3,7.45,PCO,2,26,Respiratory Acidosis,Think of CO,2,as an acid,failure of the lungs to exhale adequate CO,2,pH 45,CO,2,+H,2,CO,3,pH,Causes of Respiratory Acidosis,emphysema,drug overdose,narcosis,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,How to Analyze an ABG,PO,2,NL=80 100 mmHg,2.pHNL 7.35 7.45,Acidotic,7.45,PCO,2,NL=35 45 mmHg,Acidotic,45,Alkalotic,35,HCO,3,NL=22 26,mmol,/L,Acidotic,26,Four-step ABG Interpretation,Step 1:,Examine PaO,2,&SaO,2,Determine oxygen status,Low PaO,2,(80 mmHg)&SaO,2,means hypoxia,NL/elevated oxygen means adequate oxygenation,Step 2:,pHacidosis7.45,Fourstep ABG Interpretation,Step 3:,study PaCO,2,&HCO,3,respiratory irregularity if PaCO,2,abnl,&HCO,3,NL,metabolic irregularity if HCO,3,abnl,&PaCO,2,NL,Four-step ABG Interpretation,Step 4:,Determine if there is a compensatory mechanism working,to try to correct the pH.,ie:if have primary respiratory acidosis will have increased,PaCO,2,and decreased pH.Compensation occurs when,the kidneys retain HCO,3,.,Four-step ABG Interpretation,PaCO,2,pH Relationship,807.20607.30,40,7.40,307.50207.60,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,Respiratory Acidosis,pH7.30,PaCO,2,60,HCO,3,26,Respiratory Alkalosis,pH7.50,PaCO,2,30,HCO,3,22,Metabolic Acidosis,pH7.30,PaCO,2,40,HCO,3,15,Metabolic Alkalosis,pH7.50,PCO,2,40,HCO,3,30,What are the compensations?,Respiratory acidosis,metabolic alkalosis,Respiratory alkalosismetabolic acidosis,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.,Mixed Acid-Base Abnormalities,Case Study No.3:,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 24oxygen&VS:,ABG Results,pH7.62BP115/80 mmHg,PCO,2,30 mmHgPulse88/min,PO,2,85 mmHgRR10/min,HCO,3,30 mmol/LVT1000ml,BE10 mmol/LMV10L,K,+,2.5 mmol/L,Interpretation,:Acute alveolar hyperventilation,(resp.alkalosis)and metabolic alkalosis with corrected,hypoxemia.,Case study No.4,27 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 mmHgPulse130/min,PO,2,92 mmHgRR40/min,HCO,3,9 mmol/LVT800ml,BE-30 mmol/LMV32L,Interpretation,:Partly compensated metabolic acidosis.,Case study No.5,74 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 mmHgPulse120/min,PO,2,92 mmHgRR25/min,HCO,3,42 mmol/LVT150ml,BE17 mmol/LMV 3.75L,Interpretation,:Partly compensated metabolic alkalosis with,corrected hypoxemia.,Case study No.6,43 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,Case study No.7,17 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.,Case No.7 contd,This patient is in diabetic ketoacidosis.,IV glucose and insulin were immediately administeredA,judgement was made that severe acidemia was adversely,affecting CV function and bicarb was elected to restore pH to,7.20.,Bicarb administration calculation:,Base deficit X weight(kg),4,30 X 48,=360 mmol/LAdmin 1/2 over 15 min&,4 repeat ABG,Case No.7 contd,ABG result after bicarb:,pH7.27BP130/80 mmHg,PCO,2,25 mmHgPulse100/min,PO,2,92 mmHgRR22/min,HCO,3,11 mmol/LVT600ml,BE-14 mmol/LMV13.2L,Case study No.8,47 yo,was in PACU for 3 hours s/p cholecystectomy.She,had been on 40%oxygen and ABG&VS:,pH7.44BP130/90 mmHg,PCO,2,32 mmHgPulse95/min,regular,PO,2,121 mmHgRR20/min,HCO,3,22 mmol/LVT350ml,BE-2 mmol/LMV7L,SaO,2,98%,Hb13 g/dL,Case No.8 contd,Oxygen was changed to 2L N/C.1/2 hour pt.ready to be D/C,to floor and ABG&VS:,pH7.41BP130/90 mmHg,PCO,2,10 mmHgPulse95/min,regular,PO,2,148 mmHgRR20/min,HCO,3,6 mmol/LVT350ml,BE-17 mmol/LMV7L,SaO,2,99%,Hb7 g/dL,Case No.8 contd,What is going on?,Case No8 contd,If the picture doesnt fit,repeat ABG!,pH7.45BP130/90 mmHg,PCO,2,31 mmHgPulse95/min,PO,2,87 mmHgRR20/min,HCO,3,22 mmol/LVT350ml,BE-2 mmol/LMV7L,SaO,2,96%,Hb13 g/dL,Technical error was presumed.,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 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,Case study No.10,76 yo,with documented chronic hypercapnia secondary to,severe COPD has been in ICU for 3 days while being tx for,pneumonia.She had been stable for past 24 hours and was,transferred to general floor.Pt was on 2L oxygen&ABG&VS:,pH7.44BP135/95 mmHg,PCO,2,63 mmHgPulse110/min,PO,2,52 mmHgRR22/min,HCO,3,42 mmol/L,BE+16 mmol/LMV10LSaO,2,86%,.,Interpretation:,Chronic ventilatory failure(resp.acidosis),with uncorrected hypoxemia,Case No.10 contd,She was placed on 3L and monitored for next hour.She remained alert,oriented and comfortable.ABG was,repeated:,pH7.36BP140/100 mmHg,PCO,2,75 mmHgPulse105/min,PO,2,65 mmHgRR24/min,HCO,342 mmol/L,BE+16 mmol/LMV,4.8L,SaO,2,92%,.,Pts ventilatory pattern has changed to more rapid and,shallow breathing.Although still acceptable the pH and,CO,2,are trending in the wrong direction.High-flow,oxygen may be better for this 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 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 a pulse,oximeter,which measures SaO,2.,Its not magic understanding ABGs,it just takes a little practice!,Any Questions?,References,Shapiro,Barry A.,et al;,Clinical Application of BloodGases;,1994,2.American Journal of Nursing1999;Aug99(8):34-6,3.Journal Post Anesthesia Nursing1990;Aug;5(4)264-72,4.Irvine,David;,ABG Interpretation,A Rough and DirtyProduction,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,