arterial blood gas: collection and interpretation

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ARTERIAL BLOOD GAS: ARTERIAL BLOOD GAS: COLLECTION AND COLLECTION AND INTERPRETATION INTERPRETATION Rey Jaime M. Tan, MD Rey Jaime M. Tan, MD Clinical Associate Professor Clinical Associate Professor University of the Philippines College of Medicine

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ARTERIAL BLOOD GAS: COLLECTION AND INTERPRETATION. Rey Jaime M. Tan, MD Clinical Associate Professor University of the Philippines College of Medicine. LEARNING OBJECTIVES. Review the ABG collection procedure Recognize the common errors in ABG collection - PowerPoint PPT Presentation

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Page 1: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

ARTERIAL BLOOD GAS: ARTERIAL BLOOD GAS: COLLECTION AND COLLECTION AND INTERPRETATIONINTERPRETATION

Rey Jaime M. Tan, MDRey Jaime M. Tan, MDClinical Associate ProfessorClinical Associate Professor

University of the Philippines College of Medicine

Page 2: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

LEARNING OBJECTIVESLEARNING OBJECTIVES

• Review the ABG collection procedureReview the ABG collection procedure

• Recognize the common errors in ABG Recognize the common errors in ABG

collectioncollection

• Identify and manage simple and mixed acid-Identify and manage simple and mixed acid-

base disturbancesbase disturbances

• Utilize the serum anion gap in the diagnosis Utilize the serum anion gap in the diagnosis

of acid-base disordersof acid-base disorders

Page 3: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Normal ABG ValuesNormal ABG Values

ABG INDEXABG INDEX NORMAL VALUE NORMAL VALUE pH pH 7.35-7.45 7.35-7.45

paCOpaCO22 35-45 mm Hg35-45 mm Hg

paOpaO2 2 80-100 mm Hg 80-100 mm Hg

[HCO[HCO33]] 22 - 26 meq/L22 - 26 meq/L

SaOSaO22 97-98%97-98%

Page 4: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Which of these ABG indices is Which of these ABG indices is notnot directly measured? directly measured?

A.A. pHpH

B.B. pCOpCO22

C.C. pOpO22

D.D. HCOHCO33

E.E. None of the aboveNone of the above

Page 5: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Steps in ABG CollectionSteps in ABG Collection

1.1. Prepare the materials needed.Prepare the materials needed.

2.2. Prepare the syringe with needle.Prepare the syringe with needle.

3.3. Select the puncture site.Select the puncture site.

4.4. Perform the modified Allen test.Perform the modified Allen test.

5.5. Collect the sample.Collect the sample.

6.6. Apply pressure on puncture site.Apply pressure on puncture site.

7.7. Prepare the specimen for transport.Prepare the specimen for transport.

Page 6: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Which ABG collection error/s Which ABG collection error/s will falsely elevate the pH?will falsely elevate the pH?

A.A. Failure to cool bloodFailure to cool blood

B.B. Dilution with heparinDilution with heparin

C.C. Venous admixtureVenous admixture

D.D. Air contaminationAir contamination

E.E. None of the aboveNone of the above

Page 7: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Which ABG collection error/s Which ABG collection error/s will affect the paOwill affect the paO22??

A. Failure to cool bloodA. Failure to cool blood

B. Dilution with heparinB. Dilution with heparin

C. Venous admixtureC. Venous admixture

D. Air contaminationD. Air contamination

E. None of the aboveE. None of the above

Page 8: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Effects of ABG collection errors on pH, Effects of ABG collection errors on pH, paCOpaCO22 and paO and paO22

ABG COLLECTION ERRORABG COLLECTION ERROR pH pH paCO paCO22 paOpaO22

1. Dilution with heparin 1. Dilution with heparin INC INC DEC DEC NCNC

2. Air contamination 2. Air contamination INC INC DEC DEC INCINC

3. Venous admixture3. Venous admixture DEC DEC INC INC DECDEC

4.4. Failure to cool bloodFailure to cool blood DEC DEC INC INC

DECDEC

Legend: INC=increase, DEC=decrease, NC=no changeLegend: INC=increase, DEC=decrease, NC=no change

Page 9: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Evaluation of HypoxemiaEvaluation of Hypoxemia

• Room air, patient < 60 y.o.Room air, patient < 60 y.o.

– Mild hypoxemiaMild hypoxemia paOpaO22 < 80 mm Hg < 80 mm Hg

– Moderate hypoxemiaModerate hypoxemia paOpaO22 < 60 mm Hg < 60 mm Hg

– Severe hypoxemiaSevere hypoxemia paOpaO22 < 40 mm Hg < 40 mm Hg

• For each year > 60 y.o., subtract 1 mm Hg for For each year > 60 y.o., subtract 1 mm Hg for

limits of mild and moderate hypoxemialimits of mild and moderate hypoxemia

• At any age, a paOAt any age, a paO22 < 40 mm Hg indicates < 40 mm Hg indicates

severe hypoxemiasevere hypoxemia

Page 10: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 1Case 1

A 56 year old female vendor developed A 56 year old female vendor developed

vomiting and diarrhea 3 days prior to vomiting and diarrhea 3 days prior to

admission. She self medicated with admission. She self medicated with

Loperamide, without relief. Her last urine Loperamide, without relief. Her last urine

output was 12 hours prior to ER consult. output was 12 hours prior to ER consult.

Her BP is 80/60, HR is 110/min. and RR Her BP is 80/60, HR is 110/min. and RR

is 28/min. She has poor skin turgor.is 28/min. She has poor skin turgor.

Page 11: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Her lab data are as follows:Her lab data are as follows:

Serum Na = 130 meq/L Serum Na = 130 meq/L pH = 7.30 pH = 7.30

K = 2.5 meq/LK = 2.5 meq/L pCO pCO22 = 30 mm Hg = 30 mm Hg

Cl = 105 meq/L Cl = 105 meq/L HCO HCO33 = 15 meq/L = 15 meq/L

BUN = 15 mmol/L BUN = 15 mmol/L pO pO22 = 90 mm Hg = 90 mm Hg

Creat = 177 umol/LCreat = 177 umol/L

Page 12: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is/are her acid-base disorder/s?What is/are her acid-base disorder/s? A. simple high AG metabolic acidosisA. simple high AG metabolic acidosis

B.B. simple NAG metabolic acidosis simple NAG metabolic acidosis

C.C. mixed metabolic acidosis and respiratory mixed metabolic acidosis and respiratory alkalosisalkalosis

D.D. mixed NAG and high AG metabolic acidosis mixed NAG and high AG metabolic acidosis

E.E. mixed NAG metabolic acidosis and mixed NAG metabolic acidosis and metabolic alkalosismetabolic alkalosis

Page 13: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

STEPWISE APPROACH TO ACID-STEPWISE APPROACH TO ACID-BASE DISORDERSBASE DISORDERS

1.1. Obtain diagnostic clues from the clinical setting. Obtain diagnostic clues from the clinical setting.

2.2. Obtain simultaneous ABG and electrolyte profile. Obtain simultaneous ABG and electrolyte profile.

3.3. Determine the primary disorder. Determine the primary disorder.

4.4. Check the compensatory response.Check the compensatory response.

5. Always calculate the anion gap.5. Always calculate the anion gap.

6.6. Use the delta/deltas when applicable. Use the delta/deltas when applicable.

7.7. Look for specific etiologies for the acid-base disorders. Look for specific etiologies for the acid-base disorders.

8. 8. Prescribe a treatment regimen. Prescribe a treatment regimen.

Page 14: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

• Vomiting Vomiting • DiarrheaDiarrhea• Poor urine outputPoor urine output• HypotensionHypotension

• Metabolic alkalosisMetabolic alkalosis• NAG Metabolic acidosisNAG Metabolic acidosis• High AG Metabolic acidosisHigh AG Metabolic acidosis• High AG Metabolic acidosisHigh AG Metabolic acidosis

1. Obtain diagnostic clues from 1. Obtain diagnostic clues from the clinical setting.the clinical setting.

Page 15: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

2. Obtain simultaneous ABG and 2. Obtain simultaneous ABG and electrolyte profile.electrolyte profile.

• Verify ABG using the Henderson equation.

24 x pCO2 24 x 30[H+] = = = 48

[HCO3-] 15

• Calculate the Na/Cl ratio.In hydration problems, Na/Cl = 1.4In acid-base problems, Na/Cl 1.4

Page 16: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Relationship between arterial pH Relationship between arterial pH and [H+] in the physiologic rangeand [H+] in the physiologic range

pHpH [H+] [H+] nanoeq/Lnanoeq/L

7.807.80 1616 7.707.70 2020 7.607.60 2626 7.507.50 3232 7.407.40 4040 7.307.30 5050 7.207.20 6363 7.107.10 8080 7.007.00 100 100

Page 17: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

• Venous pH is 0.02 – 0.04 pH units lower

than arterial pH

• Venous HCO3 is 2 – 3 meq/L higher than

arterial HCO3

• Venous pCO2 is 6 – 8 mm Hg higher

than arterial pCO2

Can venous blood be used to Can venous blood be used to determine acid base disorders?determine acid base disorders?

Page 18: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

pHpH

< 7.4< 7.4 >7.4>7.4acidemiaacidemia alkalemiaalkalemia

HCOHCO33 < 24 pCO < 24 pCO22 > 40 > 40 HCOHCO33 > 24 > 24 pCO pCO22 < 40 < 40

metabolicmetabolic respiratory respiratory metabolic metabolic respiratory respiratoryacidosisacidosis alkalosisalkalosis

3. Determine the primary disorder.3. Determine the primary disorder.

Page 19: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na+

Regulatory Response to Acidemia

Cl-

H+

Protein- PO4

=,SO4=

Organic acids

normal anion gap

URINE

HCO3-

NH4+ H2PO4

-

PCT

DT

Page 20: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Compensatory Mechanisms

1. Extracellular buffering primarily by HCO3-

(immediate)2. Respiratory compensation by an increase in

alveolar ventilation (minutes to hours)

3. Intracellular buffering primarily by proteins and phosphates (2 to 4 hours)

4. Renal compensation by an ↑ in H+ excretion and ↑HCO3

- reabsorption (hours to days)

Page 21: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Henderson-Hasselbalch equation:Henderson-Hasselbalch equation:

HCOHCO33pH = 6.1 + logpH = 6.1 + log

0.03 x pCO0.03 x pCO22

HCOHCO33

pHpH = 6.1 + log = 6.1 + log

0.03 x pCO0.03 x pCO22

HCOHCO33pHpH = 6.1 + log = 6.1 + log

0.03 x pCO0.03 x pCO22

Page 22: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Henderson EquationHenderson Equation 24 x pCO2

[H+] = [HCO3

-]

24 x pCO2

[H+] = [HCO3

-]

24 x pCO2 [H+] =

[HCO3-]

Page 23: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

SIMPLE ACID-BASE DISORDERS: SIMPLE ACID-BASE DISORDERS: COMPENSATORY RESPONSECOMPENSATORY RESPONSE

PRIMARY DISTURBANCE

INITIATING CHANGE

COMPENSATORY RESPONSE

METABOLIC ACIDOSIS

DEC HCO3 DEC pCO2 1.2 mm Hg dec in pCO2 per 1 meq/L fall in HCO3

METABOLIC ALKALOSIS

INC HCO3 INC pCO2 0.7 mm Hg inc in pCO2 per 1 meq/L rise in HCO3

Page 24: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

4. Compute for the compensatory 4. Compute for the compensatory response.response.

HCOHCO33 = 24 – 15 = 9 = 24 – 15 = 9

pCOpCO22 = 9 x 1.2 = 10.8 = 9 x 1.2 = 10.8

Exp. pCOExp. pCO22 = 40 – 10.8 = 29.2 = 40 – 10.8 = 29.2 ±± 2 2

Actual pCOActual pCO22 of 30 is within the exp. pCO of 30 is within the exp. pCO22

This is a simple metabolic acidosisThis is a simple metabolic acidosis

Page 25: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

TC = TATC = TAMC + UC = MA + UAMC + UC = MA + UA

MC - MA = UA - UC = anion gapMC - MA = UA - UC = anion gapNa - [Cl + HCONa - [Cl + HCO33] = UA - UC = anion gap] = UA - UC = anion gap

UA: Lactate, Ketones, Uremic anions, Toxic UA: Lactate, Ketones, Uremic anions, Toxic anions, Albumin anions, AlbuminUC: Potassium, Calcium, Magnesium, Globulin, UC: Potassium, Calcium, Magnesium, Globulin, Lithium Lithium

SERUM ANION GAPSERUM ANION GAP

Na - [Cl + HCONa - [Cl + HCO33] = 12 ] = 12 ±± 4 4

Page 26: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

5. Calculate the anion gap.5. Calculate the anion gap.

AG = Na – [Cl + HCOAG = Na – [Cl + HCO33]]

= 130 – [105 + 15]= 130 – [105 + 15] = 10= 10

This is a simple normal anion gap This is a simple normal anion gap metabolic acidosis.metabolic acidosis.

Note: A high AG ALWAYS indicates the presence of a Note: A high AG ALWAYS indicates the presence of a high AG metabolic acidosis.high AG metabolic acidosis.

Page 27: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na136

Cl100

AG 12

HCO3

24

NORMAL

Na136

Cl94

AG 22

HCO3

20

COMBINED AGMET. ACIDOSIS& MET. ALKALOSIS

AG HCO3

= 10 4

Na136

Cl106

AG 22

HCO3 8

COMBINED AG& NAG MET. ACIDOSIS

AG HCO3

= 1016

Na136

Cl100

AG 22

HCO3

14

SIMPLE AGMETABOLICACIDOSIS

AG HCO3

= 1010

DELTA AnionGap/DELTA HCODELTA AnionGap/DELTA HCO33

Page 28: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na136

Cl100

AG 12

HCO3

24

NORMAL

Na134

Cl110

AG 10

HCO3

14

SIMPLE NAGMETABOLICACIDOSIS

Cl HCO3

= 1010

Na128

Cl110

AG 10

HCO3 8

COMBINED NAG & AG MET. ACIDOSIS

Cl HCO3

= 1016

Na140

Cl110

AG 10

HCO3

20

COMBINED NAGMET. ACIDOSIS& MET. ALKALOSIS

Cl HCO3

= 10 4

DELTA Chloride/DELTA HCODELTA Chloride/DELTA HCO33

Page 29: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

6. Use the delta-deltas to detect 6. Use the delta-deltas to detect coexisting metabolic disorders.coexisting metabolic disorders.

Cl 105 –100 5

HCO3 24 – 15 9====

This is a combined normal anion gap This is a combined normal anion gap and high anion gap metabolic acidosis.and high anion gap metabolic acidosis.

Page 30: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

CAUSES OF METABOLIC ACIDOSISCAUSES OF METABOLIC ACIDOSIS

INCREASED ANION GAPINCREASED ANION GAP

• KetoacidosisKetoacidosis

DiabeticDiabetic

AlcoholismAlcoholism

StarvationStarvation• Lactic AcidosisLactic Acidosis• UremiaUremia• ToxinsToxins

NORMAL ANION GAPNORMAL ANION GAP

• Associated w/ K lossAssociated w/ K loss

DiarrheaDiarrhea

RTARTA• Interstitial nephritisInterstitial nephritis• Early renal failureEarly renal failure• Urinary tract obstrxnUrinary tract obstrxn• Drug-inducedDrug-induced

Page 31: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na+

States of Systemic Acidosis

Cl-

High anion gap

H+

Protein- PO4

=,SO4=

Organic acids

HCO3-

M- methanol U- uremia D- DKA P- paraldehyde I- iron, INH L- lactic acidosis E- ethylene glycol S- salicylates

Page 32: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

How would you correct her acid-How would you correct her acid-base disorder?base disorder? A. A. KCl infusionKCl infusion

B.B. Intravenous NaHCOIntravenous NaHCO3 3 dripdrip

C.C. Oral NaHCOOral NaHCO33

D.D. Hydration aloneHydration alone

Page 33: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

COMPLICATIONS OF HCOCOMPLICATIONS OF HCO33 THERAPY THERAPY

• Causes volume overload/hypernatremia/ Causes volume overload/hypernatremia/ hyperosmolalityhyperosmolality

Na contentNa content Na meq/mLNa meq/mL mosm/Lmosm/L0.9% saline0.9% saline 0.15 0.15 308 3087.5% NaHCO7.5% NaHCO33 0.89 0.89 1784 1784

8.4% NaHCO8.4% NaHCO33 1.00 1.00 2000 2000

Page 34: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

COMPLICATIONS OF HCOCOMPLICATIONS OF HCO33 THERAPY THERAPY

• Worsens hypokalemia and hypocalcemiaWorsens hypokalemia and hypocalcemia

• Induces intracellular acidosisInduces intracellular acidosis

• Causes overshoot alkalosisCauses overshoot alkalosis

• Stimulates organic acid productionStimulates organic acid production

• Decreases tissue oxygen deliveryDecreases tissue oxygen delivery

Page 35: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

BENEFITS OF HCOBENEFITS OF HCO33 THERAPY THERAPY

• minimizes depletion of buffer stores by minimizes depletion of buffer stores by

ongoing metabolic acidosisongoing metabolic acidosis

• reverses the harmful cardiovascular reverses the harmful cardiovascular

effects of systemic acidosis (decreased effects of systemic acidosis (decreased

cardiac output, decreased arteriolar cardiac output, decreased arteriolar

resistance, increased venoconstriction)resistance, increased venoconstriction)

Page 36: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

BENEFITS OF HCOBENEFITS OF HCO33 THERAPY THERAPY

• in severe acidemia, systemic pH is in severe acidemia, systemic pH is

sensitive to small absolute changes in sensitive to small absolute changes in

pCOpCO22 and HCO and HCO33

Pure LAPure LA LA + mild LA + mild worse LAworse LA HCO HCO3 3 Tx Tx COCO22 retention retention for pure LAfor pure LA

pHpH 7.15 7.15 7.06 7.06 6.70 6.70 7.35 7.35pCOpCO22 15 15 18 18 15 15 15 15

HCOHCO33 5 5 5 5 2 8 2 8

Page 37: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

GENERAL INDICATIONS FOR HCOGENERAL INDICATIONS FOR HCO33 THERAPY THERAPY

• pH < 7.20 and HCOpH < 7.20 and HCO33 < 5 - 10 mm Hg < 5 - 10 mm Hg

• Used when inadequate ventilatory Used when inadequate ventilatory

compensation is presentcompensation is present

• Elderly on beta blockers in severe acidosis Elderly on beta blockers in severe acidosis

with compromised cardiac function with compromised cardiac function

• Concurrent severe AG and NAG metabolic Concurrent severe AG and NAG metabolic

acidosisacidosis

• Severe acidemia with renal failure or Severe acidemia with renal failure or

intoxicationsintoxications

Page 38: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 2Case 2A 30 year old male with a history of epilepsy A 30 year old male with a history of epilepsy

has a grand mal seizure. Laboratory tests has a grand mal seizure. Laboratory tests

taken immediately after the seizure has taken immediately after the seizure has

stopped reveal:stopped reveal:

Arterial pH = 7.14Arterial pH = 7.14

pCOpCO22 = 45 mm Hg = 45 mm Hg

Plasma [NaPlasma [Na++] = 140 meq/L] = 140 meq/L

[K[K++] = 4.0 meq/L] = 4.0 meq/L

[Cl[Cl--] = 98 meq/L] = 98 meq/L

[HCO[HCO33--] = 17 meq/L] = 17 meq/L

AG = 25AG = 25

Page 39: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is/are his acid-base disorder/s?What is/are his acid-base disorder/s? A. simple high AG metabolic acidosisA. simple high AG metabolic acidosis

B.B. simple NAG metabolic acidosis simple NAG metabolic acidosis

C.C. mixed metabolic acidosis and mixed metabolic acidosis and respiratory alkalosisrespiratory alkalosis

D.D. mixed metabolic acidosis and mixed metabolic acidosis and respiratory acidosisrespiratory acidosis

Page 40: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

STEPWISE APPROACH TO ACID-STEPWISE APPROACH TO ACID-BASE DISORDERSBASE DISORDERS

1.1. Obtain diagnostic clues from the clinical setting. Obtain diagnostic clues from the clinical setting.

2.2. Obtain simultaneous ABG and electrolyte profile. Obtain simultaneous ABG and electrolyte profile.

3.3. Determine the primary disorder. Determine the primary disorder.

4.4. Check the compensatory response.Check the compensatory response.

5. Always calculate the anion gap.5. Always calculate the anion gap.

6.6. Use the delta/deltas when applicable. Use the delta/deltas when applicable.

7.7. Look for specific etiologies for the acid-base disorders. Look for specific etiologies for the acid-base disorders.

8. 8. Prescribe a treatment regimen. Prescribe a treatment regimen.

Page 41: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

• Seizure Seizure

• Depressed Depressed

sensoriumsensorium

• Lactic acidosisLactic acidosis• HAG metabolic HAG metabolic

acidosisacidosis• Respiratory acidosisRespiratory acidosis

1. Obtain diagnostic clues from 1. Obtain diagnostic clues from the clinical setting.the clinical setting.

Page 42: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 2Case 2

A 30 year old male with a history of A 30 year old male with a history of

epilepsy has a grand mal seizure. epilepsy has a grand mal seizure.

Laboratory tests taken immediately after Laboratory tests taken immediately after

the seizure has stopped reveal:the seizure has stopped reveal:

Arterial pH = 7.14Arterial pH = 7.14

pCOpCO22 = 45 mm Hg = 45 mm Hg

Plasma [NaPlasma [Na++] = 140 meq/L] = 140 meq/L

[K[K++] = 4.0 meq/L] = 4.0 meq/L

[Cl[Cl--] = 98 meq/L] = 98 meq/L

[HCO[HCO33--] = 17 meq/L] = 17 meq/L

AG = 25AG = 25

Page 43: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

pHpH

< 7.4< 7.4 >7.4>7.4acidemiaacidemia alkalemiaalkalemia

HCO3 < 24 pCO2 > 40HCO3 < 24 pCO2 > 40 HCO3 > 24HCO3 > 24 pCO2 < 40 pCO2 < 40 metabolicmetabolic respiratoryrespiratory metabolic metabolic respiratory respiratory

acidosisacidosis alkalosisalkalosis

3. Determine the primary disorder.3. Determine the primary disorder.

Page 44: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

HCOHCO33

2424pCOpCO22

4040vs.vs.

24 - 1724 - 17 2424

45 - 4045 - 40 4040

vs.vs.

77 2424

55 4040

>>

The primary disorder is a The primary disorder is a metabolic acidosis.metabolic acidosis.

Page 45: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

4. Compute for the compensatory 4. Compute for the compensatory response.response.

HCOHCO33 = 24 – 17 = 7 = 24 – 17 = 7

pCOpCO22 = 7 x 1.2 = 8.4 = 7 x 1.2 = 8.4

Exp. pCOExp. pCO22 = 40 – 8.4 = 31.6 = 40 – 8.4 = 31.6 ±± 2 2

Actual pCOActual pCO22 of 45 is higher than exp. pCO of 45 is higher than exp. pCO22

This is a mixed metabolic acidosis This is a mixed metabolic acidosis and respiratory acidosis.and respiratory acidosis.

Page 46: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

6. Use the delta-deltas to detect 6. Use the delta-deltas to detect coexisting metabolic disorders.coexisting metabolic disorders.

AG 25 – 12 13

HCO3 24 – 17 7====

This is a combined high anion gap This is a combined high anion gap metabolic acidosis and metabolic metabolic acidosis and metabolic

alkalosis.alkalosis.

Page 47: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

How would you correct his acid-baseHow would you correct his acid-basedisorder?disorder? A. administer IV NaHCOA. administer IV NaHCO3 3 using HCOusing HCO33 deficit deficit

B.B. administer oral NaHCO administer oral NaHCO3 3 at 1 meq/kg/dayat 1 meq/kg/day

C.C. Intubate Intubate

D.D. no treatment no treatment

Page 48: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Compute HCOCompute HCO33 deficit. deficit.

HCOHCO33 deficit = deficit = [Desired HCO[Desired HCO33 – Actual HCO – Actual HCO33]] x 0.5* x kg BWx 0.5* x kg BW

* As the serum HCO* As the serum HCO33 decreases below 5-10, the volume decreases below 5-10, the volume of distribution increases and total HCOof distribution increases and total HCO33 requirement will requirement will also increase also increase use 0.7 – 1.0 use 0.7 – 1.0

Maintenance HCOMaintenance HCO33 = 1 meq/kg/day = 1 meq/kg/day

Page 49: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Principles of HCOPrinciples of HCO33 therapy in therapy in

lactic acidosislactic acidosis

• Primary effort should be directed at improving Primary effort should be directed at improving the delivery of oxygenthe delivery of oxygen

• Use NaHCOUse NaHCO33 only when HCO only when HCO33 < 5 mmol/L < 5 mmol/L

• In states of low cardiac output, raising the In states of low cardiac output, raising the cardiac output will have a larger impact on the cardiac output will have a larger impact on the pH of the ICF than will HCOpH of the ICF than will HCO33 therapy therapy

• In cases with low alveolar ventilation, In cases with low alveolar ventilation, increase ventilation to lower the tissue pCOincrease ventilation to lower the tissue pCO22

Page 50: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Principles of HCOPrinciples of HCO33 therapy in therapy in

ketoacidosisketoacidosis• In ketoacidosis, the rate of HIn ketoacidosis, the rate of H++ production is production is

slow and NaHCOslow and NaHCO33 therapy may carry the risk therapy may carry the risk of provoking severe hypokalemia, of provoking severe hypokalemia, NaHCO NaHCO33 should be should be avoidedavoided in most cases in most cases

• Consider HCOConsider HCO33 therapy: therapy:

• Severe hyperkalemia despite insulinSevere hyperkalemia despite insulin

• When HCOWhen HCO33 < 5 mmol/L < 5 mmol/L

• Worsening acidemia inspite of insulinWorsening acidemia inspite of insulin

Page 51: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 3Case 3

Alona, a 22 year old dancer, complains of Alona, a 22 year old dancer, complains of

weakness. She denies vomiting and weakness. She denies vomiting and

intake of medications other than vitamins. intake of medications other than vitamins.

Physical examination reveals a thin lady Physical examination reveals a thin lady

with a BP of 90/55 mm Hg, HR of 110/min with a BP of 90/55 mm Hg, HR of 110/min

and an orthostatic drop in blood pressure.and an orthostatic drop in blood pressure.

Page 52: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Her lab data are as follows:Her lab data are as follows:

PlasmaPlasma UrineUrine

NaNa mmol/L mmol/L 133 133 52 52

K mmol/LK mmol/L 3.1 3.1 50 50

Cl mmol/LCl mmol/L 90 90 0 0

HCOHCO33 mmol/L mmol/L 32 32 -- --

pHpH 7.48 7.48 7.0 7.0

pCOpCO22 mm Hg mm Hg 45 45 -- --

Page 53: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is/are her acid-base What is/are her acid-base disorder/s?disorder/s? A. A. simple metabolic alkalosissimple metabolic alkalosis

B.B. mixed metabolic alkalosis and mixed metabolic alkalosis and respiratory alkalosisrespiratory alkalosis

C.C. mixed metabolic alkalosis andmixed metabolic alkalosis andrespiratory acidosisrespiratory acidosis

D.D. mixed metabolic alkalosis andmixed metabolic alkalosis andmetabolic acidosismetabolic acidosis

Page 54: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

pHpH

< 7.4< 7.4 >7.4>7.4acidemiaacidemia alkalemiaalkalemia

HCO3 < 24 pCO2 > 40HCO3 < 24 pCO2 > 40 HCO3 > 24HCO3 > 24 pCO2 < 40 pCO2 < 40 metabolicmetabolic respiratory respiratory metabolicmetabolic respiratory respiratory

acidosisacidosis alkalosisalkalosis

3. Determine the primary disorder.3. Determine the primary disorder.

Page 55: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

SIMPLE ACID-BASE DISORDERS: SIMPLE ACID-BASE DISORDERS: COMPENSATORY RESPONSECOMPENSATORY RESPONSE

PRIMARY DISTURBANCE

INITIATING CHANGE

COMPENSATORY RESPONSE

METABOLIC ACIDOSIS

DEC HCO3 DEC pCO2 1.2 mm Hg dec in pCO2 per 1 meq/L fall in HCO3

METABOLIC ALKALOSIS

INC HCO3 INC pCO2 0.7 mm Hg inc in pCO2 per 1 meq/L rise in HCO3

Page 56: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

4. Compute for the compensatory 4. Compute for the compensatory response.response.

HCOHCO33 = 32 - 24 = 8 = 32 - 24 = 8

pCOpCO22 = 8 x 0.7 = 5.6 = 8 x 0.7 = 5.6

Exp. pCOExp. pCO22 = 40 + 5.6 = 45.6 = 40 + 5.6 = 45.6 ±± 2 2

Actual pCOActual pCO22 of 45 is within the exp. pCO of 45 is within the exp. pCO22

This is a simple metabolic alkalosisThis is a simple metabolic alkalosis

Page 57: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is the cause of her hypokalemia What is the cause of her hypokalemia and metabolic alkalosis?and metabolic alkalosis? A. A. diuretic intakediuretic intake

B.B. surreptitious vomitingsurreptitious vomiting

C.C. Bartter’s like syndromeBartter’s like syndrome

D.D. adrenal tumoradrenal tumor

E. E. nonreabsorbable anionnonreabsorbable anion

Page 58: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

METABOLIC ALKALOSISUrine Cl < 10 meq/day Urine Cl > 20 meq/day

• VomitingVomiting• Diuretics (Remote)Diuretics (Remote)• Post-hypercapneaPost-hypercapnea• Chronic diarrheaChronic diarrhea• Chloride deficiency Chloride deficiency

syndromesyndrome• Congenital Congenital

chloridorrheachloridorrhea• Cystic fibrosisCystic fibrosis

• Normal BP– Bartter’s syndrome– Severe K depletion– Diuretics (current)– hypercalcemia

• Increased BP– Hyperaldosteronism– Cushing’s syndrome– Ectopic ACTH– Excess corticosterone

Page 59: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Diuretic Recent Remote Vomiting Recent Remote Bartter’s Expanded blood volume Nonreabsorb-able anion

U Na High Low High Low High High High

U K High Low High Low High High High

U Cl High Low Low Low High High Low

U pH < 6 < 6 > 7 < 6 6-6.5 5-8 < 6

Page 60: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

How should her metabolic alkalosis How should her metabolic alkalosis be managed? be managed?

A. correct hypokalemiaA. correct hypokalemia

B.B. hydrate with NSS hydrate with NSS

C.C. administer an acidifying agent administer an acidifying agent

D.D. give carbonic anhydrase give carbonic anhydrase

Page 61: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

MANAGEMENT OF METABOLIC MANAGEMENT OF METABOLIC ALKALOSISALKALOSIS

• Chloride repletionChloride repletion

• Potassium repletionPotassium repletion

• Treatment of hypermineralo-Treatment of hypermineralo-

corticoidismcorticoidism

• DialysisDialysis

Page 62: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

MANAGEMENT OF METABOLIC MANAGEMENT OF METABOLIC ALKALOSISALKALOSIS

• Increase HCOIncrease HCO33 excretion with excretion with

carbonic anhydrase inhibitors carbonic anhydrase inhibitors

(acetazolamide)(acetazolamide)

• Acidifying agents (HCl, NHAcidifying agents (HCl, NH44Cl)Cl)

Page 63: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

INDICATIONS FOR HClINDICATIONS FOR HCl

• pH > 7.55 and HCOpH > 7.55 and HCO33 > 35 with > 35 with contraindications for NaCl or KCl usecontraindications for NaCl or KCl use

• For immediate correction of metabolic For immediate correction of metabolic alkalosis in the presence of hepatic alkalosis in the presence of hepatic encephalopathy, cardiac arrhythmias, encephalopathy, cardiac arrhythmias, digitalis intoxicationdigitalis intoxication

• When initial response to NaCl, KCl or When initial response to NaCl, KCl or acetazolamide is too slow or too littleacetazolamide is too slow or too little

Page 64: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

USE OF HClUSE OF HCl

• Use sterile 0.1 – 0.2 N HCl solution (100 – Use sterile 0.1 – 0.2 N HCl solution (100 – 200 meq/L)200 meq/L)

• Use a large central veinUse a large central vein

• Do NOT exceed 0.2 meq/kgBW/hour of Do NOT exceed 0.2 meq/kgBW/hour of HClHCl

• HCl requirement (meq/L) = HCl requirement (meq/L) =

[Actual – Desired HCO[Actual – Desired HCO33] x 0.5 x kgBW] x 0.5 x kgBW

Page 65: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 4Case 4Lola, an 87 year old female, with a Lola, an 87 year old female, with a

longstanding history of COPD and longstanding history of COPD and

congestive heart failure with marked edema, congestive heart failure with marked edema,

was treated with a diuretic and lost 5 liters of was treated with a diuretic and lost 5 liters of

ECF. Her mental state deteriorated following ECF. Her mental state deteriorated following

treatment. Physical examination revealed treatment. Physical examination revealed

that she was obtunded. BP = 100/70that she was obtunded. BP = 100/70 HR=110 HR=110

RR = 24 She had scattered rhonchi and rales RR = 24 She had scattered rhonchi and rales

on both lung fields but no more edema.on both lung fields but no more edema.

Page 66: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Her lab data revealed the following:Her lab data revealed the following:

Steady state AdmissionSteady state Admission

pHpH 7.29 7.29 7.34 7.34

pCOpCO22 mm Hg mm Hg 60 60 85 85

HCOHCO33 mmol/L mmol/L 29 29 44 44

pOpO22 mmHg mmHg 50 50 39 39

K mmol/LK mmol/L 4.1 4.1 3.1 3.1

AGAG 11 11 16 16

Creat umol/LCreat umol/L 57 57 66 66

Page 67: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Her pOHer pO22 at steady state suggests at steady state suggests

A. mild hypoxemiaA. mild hypoxemia

B. moderate hypoxemiaB. moderate hypoxemia

C.C. severe hypoxemia severe hypoxemia

D.D. normal value for agenormal value for age

Page 68: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Her pOHer pO22 on admission suggests on admission suggests

A. mild hypoxemiaA. mild hypoxemia

B. moderate hypoxemiaB. moderate hypoxemia

C. severe hypoxemia C. severe hypoxemia

D. normal value for ageD. normal value for age

Page 69: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is/are her acid-base What is/are her acid-base disorder/s on admission?disorder/s on admission?

A.A. acute respiratory acidosisacute respiratory acidosis

B.B. A + chronic respiratory acidosisA + chronic respiratory acidosis

C.C. B + metabolic alkalosis B + metabolic alkalosis

D.D. C + metabolic acidosisC + metabolic acidosis

E.E. chronic respiratory acidosischronic respiratory acidosis

Page 70: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

• COPD COPD • Diuretic use Diuretic use • HypokalemiaHypokalemia • Acute Resp FailureAcute Resp Failure• Pneumonia ? Pneumonia ? • Sepsis ?Sepsis ?

• Chronic respiratory acidosisChronic respiratory acidosis• Metabolic alkalosisMetabolic alkalosis• Metabolic alkalosisMetabolic alkalosis• Acute respiratory acidosisAcute respiratory acidosis• Acute respiratory acidosisAcute respiratory acidosis• High AG metabolic acidosisHigh AG metabolic acidosis

1. Obtain diagnostic clues from 1. Obtain diagnostic clues from the clinical setting.the clinical setting.

Page 71: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

pHpH

< 7.4< 7.4 >7.4>7.4acidemiaacidemia alkalemiaalkalemia

HCO3 < 24 pCO2 > 40HCO3 < 24 pCO2 > 40 HCO3 > 24HCO3 > 24 pCO2 < 40 pCO2 < 40 metabolicmetabolic respiratory respiratory metabolic metabolic respiratory respiratory

acidosisacidosis alkalosisalkalosis

3. Determine the primary disorder.3. Determine the primary disorder.

Page 72: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

SIMPLE ACID-BASE DISORDERS: SIMPLE ACID-BASE DISORDERS: COMPENSATORY RESPONSECOMPENSATORY RESPONSE

PRIMARY DISTURBANCE

INITIATING CHANGE

COMPENSATORY RESPONSE

RESPIRATORY ACIDOSIS ACUTE CHRONIC

INC pCO2

INC HCO3 1 meq/L inc in HCO3 per 10 mm Hg rise in pCO2 3.5 meq/L inc in HCO3 per10 mm Hg rise in pCO2

RESPIRATORY ALKALOSIS ACUTE CHRONIC

DEC pCO2

DEC HCO3 2 meq/L dec in HCO3 per 10 mm Hg fall in pCO2 5 meq/L dec in HCO3 per 10 mm Hg fall in pCO2

Page 73: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

4. Compute for the compensatory response.4. Compute for the compensatory response.COPD:COPD:pCOpCO22 = 60 - 40 = 20 = 60 - 40 = 20

HCOHCO33 = 20/10 x 3.5 = 7.0 = 20/10 x 3.5 = 7.0

Exp. HCOExp. HCO33 = 24 + 7.0 = 31 = 24 + 7.0 = 31

Acute Respiratory Failure:Acute Respiratory Failure:pCOpCO22 = 85 - 60 = 25 = 85 - 60 = 25

HCOHCO33 = 25/10 x 1 = 2.50 = 25/10 x 1 = 2.50

Exp. HCOExp. HCO33 = 29.0 + 2.5 = 31.5 = 29.0 + 2.5 = 31.5

Actual HCOActual HCO33 of 44 is higher than exp. HCO of 44 is higher than exp. HCO33

This is a mixed respiratory acidosis and metabolic This is a mixed respiratory acidosis and metabolic alkalosis.alkalosis.

Page 74: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

AG = 16AG = 16

Although the AG is normal, the AG Although the AG is normal, the AG actually rose from baseline, suggesting actually rose from baseline, suggesting subtly that there is a concomitant subtly that there is a concomitant metabolic acidosis.metabolic acidosis.

Note: A high AG ALWAYS indicates the presence of a Note: A high AG ALWAYS indicates the presence of a high AG metabolic acidosis.high AG metabolic acidosis.

5. Calculate the anion gap.5. Calculate the anion gap.

Page 75: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

How should she have been managed How should she have been managed on admission?on admission? A.A. intubation and mechanical ventilationintubation and mechanical ventilation

B.B. low flow oxygenation by nasal pronglow flow oxygenation by nasal prong

C.C. oxygen by face maskoxygen by face mask

D.D. KCl correctionKCl correction

Page 76: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

MANAGEMENT OF RESPIRATORY MANAGEMENT OF RESPIRATORY ACIDOSISACIDOSIS

• Correct underlying cause for hypo-Correct underlying cause for hypo-

ventilationventilation

• Increase effective alveolar ventilation: Increase effective alveolar ventilation:

intubate, mechanically ventilateintubate, mechanically ventilate

• Antagonize sedative drugs (e.g. naloxone)Antagonize sedative drugs (e.g. naloxone)

• Stimulate respiration (e.g. progesterone)Stimulate respiration (e.g. progesterone)

• Correct metabolic alkalosis (e.g. carbonic Correct metabolic alkalosis (e.g. carbonic

anhydrase inhibitors)anhydrase inhibitors)

Page 77: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 5Case 5

Mr. X, a 42 year old male alcoholic, is Mr. X, a 42 year old male alcoholic, is

brought to the ER obviously intoxicated. brought to the ER obviously intoxicated.

He was found in Rizal park in a pool of He was found in Rizal park in a pool of

vomitus. On PE he is unkempt and vomitus. On PE he is unkempt and

incoherent with a markedly contracted incoherent with a markedly contracted

ECF volume. Temp. is 39ECF volume. Temp. is 3900C with C with

crackles on his right upper lung field.crackles on his right upper lung field.

Page 78: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

His lab data are as follows:His lab data are as follows:

Serum Na = 130 mmol/L Serum Na = 130 mmol/L pH = 7.53pH = 7.53

K = 2.9 mmol/L K = 2.9 mmol/L pCOpCO22 = 25 mm Hg = 25 mm Hg

Cl = 80 mmol/L Cl = 80 mmol/L HCOHCO33 = 20 mmoll/L = 20 mmoll/L

RBS = 15 mmol/LRBS = 15 mmol/L pOpO2 2 = 60 mm Hg = 60 mm Hg

BUN = 12 mmol/L BUN = 12 mmol/L Alb = 38 gm/LAlb = 38 gm/L

Creat = 120 umol/LCreat = 120 umol/L AG = 30AG = 30

Plasma osm = 320 mosm/kgPlasma osm = 320 mosm/kg

Plasma ketones weakly positivePlasma ketones weakly positive

Page 79: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is/are his acid-base disorder/s?What is/are his acid-base disorder/s? A.A. simple respiratory alkalosissimple respiratory alkalosis

B.B. simple metabolic alkalosissimple metabolic alkalosis

C.C. simple high AG metabolic acidosissimple high AG metabolic acidosis

D.D. mixed respiratory alkalosis,mixed respiratory alkalosis, metabolic acidosis and metabolicmetabolic acidosis and metabolic

alkalosisalkalosis

Page 80: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

pHpH

< 7.4< 7.4 >7.4>7.4acidemiaacidemia alkalemiaalkalemia

HCO3 < 24 pCO2 > 40HCO3 < 24 pCO2 > 40 HCO3 > 24HCO3 > 24 pCO2 < 40 pCO2 < 40 metabolicmetabolic respiratory respiratory metabolic metabolic respiratoryrespiratory

acidosisacidosis alkalosisalkalosis

3. Determine the primary disorder.3. Determine the primary disorder.

Page 81: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

SIMPLE ACID-BASE DISORDERS: SIMPLE ACID-BASE DISORDERS: COMPENSATORY RESPONSECOMPENSATORY RESPONSE

PRIMARY DISTURBANCE

INITIATING CHANGE

COMPENSATORY RESPONSE

RESPIRATORY ACIDOSIS ACUTE CHRONIC

INC pCO2

INC HCO3 1 meq/L inc in HCO3 per 10 mm Hg rise in pCO2 3.5 meq/L inc in HCO3 per10 mm Hg rise in pCO2

RESPIRATORY ALKALOSIS ACUTE CHRONIC

DEC pCO2

DEC HCO3 2 meq/L dec in HCO3 per 10 mm Hg fall in pCO2 5 meq/L dec in HCO3 per 10 mm Hg fall in pCO2

Page 82: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

4. Compute for the compensatory response.4. Compute for the compensatory response.

Acute Respiratory AlkalosisAcute Respiratory AlkalosispCOpCO22 = 40 - 25 = 15 = 40 - 25 = 15

HCOHCO33 = 15/10 x 2 = 3.00 = 15/10 x 2 = 3.00

Exp. HCOExp. HCO33 = 24 – 3 = 21 = 24 – 3 = 21

Actual HCOActual HCO33 of 20 is within the exp. HCO of 20 is within the exp. HCO33

This is a simple respiratory alkalosis.This is a simple respiratory alkalosis.

Page 83: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

AG = 30AG = 30

There is a high anion gap metabolic There is a high anion gap metabolic acidosis.acidosis.

Note: A high AG ALWAYS indicates the presence of a Note: A high AG ALWAYS indicates the presence of a high AG metabolic acidosis.high AG metabolic acidosis.

5. Calculate the anion gap.5. Calculate the anion gap.

Page 84: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

6. Use the delta-deltas to detect 6. Use the delta-deltas to detect coexisting metabolic disorders.coexisting metabolic disorders.

AG 30 - 12 18

HCO3 24 – 20 4====

This is a combined high anion gap This is a combined high anion gap metabolic acidosis and metabolic metabolic acidosis and metabolic

alkalosis.alkalosis.

Page 85: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is/are the cause/s of hisWhat is/are the cause/s of hisacid-base disorder?acid-base disorder? A.A. aspiration pneumoniaaspiration pneumonia

B.B. alcoholic ketoacidosisalcoholic ketoacidosis

C.C. vomitingvomiting

D.D. renal failurerenal failure

E.E. all of the aboveall of the above

Page 86: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

MANAGEMENT OF RESPIRATORY MANAGEMENT OF RESPIRATORY ALKALOSISALKALOSIS

• Correct underlying cause for hyperventilationCorrect underlying cause for hyperventilation

• Rebreathe carbon dioxideRebreathe carbon dioxide

• Mechanical ventilatory control of respiration:Mechanical ventilatory control of respiration:

– increase dead spaceincrease dead space

– decrease back-up ratedecrease back-up rate

– decrease tidal volumedecrease tidal volume

– paralyze respiratory musclesparalyze respiratory muscles

Page 87: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Case 6Case 6

A 27 year old patient notices progressive A 27 year old patient notices progressive

weakness when climbing stairs in the weakness when climbing stairs in the

past several months. She denies diarrhea past several months. She denies diarrhea

or any problem in the GI tract. There are or any problem in the GI tract. There are

no special findings in the physical no special findings in the physical

examination.examination.

Page 88: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Her lab data are as follows:Her lab data are as follows:

PlasmaPlasma UrineUrine

Creat Creat mol/Lmol/L 70 70 -- --

Na mmol/L Na mmol/L 140 140 57 57

K mmol/LK mmol/L 2.7 2.7 32 32

Cl mmol/LCl mmol/L 115 115 82 82

HCOHCO33 mmol/L mmol/L 17 17 -- --

pHpH 7.32 7.32 7.3 7.3

pCOpCO22 mm Hg mm Hg 32 32 -- --

Page 89: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

What is the cause of this patient’s What is the cause of this patient’s acid-base disorder?acid-base disorder?

A.A. diarrheadiarrhea

B.B. renal tubular acidosis type Irenal tubular acidosis type I

C.C. renal tubular acidosis type IIrenal tubular acidosis type II

D.D. renal tubular acidosis type IVrenal tubular acidosis type IV

E.E. early renal failureearly renal failure

Page 90: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

pHpH

< 7.4< 7.4 >7.4>7.4acidemiaacidemia alkalemiaalkalemia

HCOHCO33 < 24 pCO < 24 pCO22 > 40 > 40 HCOHCO33 > 24 > 24 pCO pCO22 < 40 < 40

metabolicmetabolic respiratory respiratory metabolic metabolic respiratory respiratoryacidosisacidosis alkalosisalkalosis

3. Determine the primary disorder.3. Determine the primary disorder.

Page 91: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

4. Compute for the compensatory 4. Compute for the compensatory response.response.

HCOHCO33 = 24 – 17 = 7 = 24 – 17 = 7

pCOpCO22 = 7 x 1.2 = 8.4 = 7 x 1.2 = 8.4

Exp. pCOExp. pCO22 = 40 – 8.4 = 31.6 = 40 – 8.4 = 31.6 ±± 2 2

Actual pCOActual pCO22 of 32 is within the exp. pCO of 32 is within the exp. pCO22

This is a simple metabolic acidosisThis is a simple metabolic acidosis

Page 92: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

5. Calculate the anion gap.5. Calculate the anion gap.

AG = Na – [Cl + HCOAG = Na – [Cl + HCO33]]

= 140 – [115 + 17]= 140 – [115 + 17] = 8= 8

This is a simple normal anion gap This is a simple normal anion gap metabolic acidosis.metabolic acidosis.

Note: A high AG ALWAYS indicates the presence of a Note: A high AG ALWAYS indicates the presence of a high AG metabolic acidosis.high AG metabolic acidosis.

Page 93: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

6. Use the delta-deltas to detect 6. Use the delta-deltas to detect coexisting metabolic disorders.coexisting metabolic disorders.

Cl 115 –100 15

HCO3 24 – 17 7====

This is a combined normal anion gap This is a combined normal anion gap metabolic acidosis and metabolic metabolic acidosis and metabolic

alkalosis.alkalosis.

Page 94: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na+

Defects in Renal Proton Handling

Cl-

HCO3-

Protein- PO4

=,SO4=

Organic acids

High anion gap

PCT

DTH+

Page 95: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na+

Defects in Renal Proton Handling

Cl-

HCO3-

H+

Protein- PO4

=,SO4=

Organic acids

High anion gap

Page 96: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Na+

normalanion gap

Protein- PO4

=,SO4=

Organic acids

urine

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

HCO3-

Cl-Cl-

HCO3- losing disorders

Renal (RTA) Gastrointestinal

Defects in Renal Proton HandlingHyperchloremic Metabolic Acidosis

H+

Page 97: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

Calculate the urine anion gap.Calculate the urine anion gap.

UAG = UNa + UK – UClUAG = UNa + UK – UCl = 57 + 32 - 82= 57 + 32 - 82 = 7= 7

This suggests that the kidneys are unable This suggests that the kidneys are unable to generate enough ammonium to excrete to generate enough ammonium to excrete excess acid. excess acid. This is consistent with a renal tubular This is consistent with a renal tubular acidosis.acidosis.

Page 98: ARTERIAL BLOOD GAS:  COLLECTION AND INTERPRETATION

RENAL TUBULAR ACIDOSISRENAL TUBULAR ACIDOSIS

Type 1Type 1 Type 2Type 2 Type 4Type 4

ABGABG NAG NAG Metabolic Metabolic acidosisacidosis

NAG NAG Metabolic Metabolic acidosisacidosis

NAG NAG Metabolic Metabolic acidosisacidosis

Serum KSerum K LowLow LowLow HighHigh

Urine pHUrine pH > 5.5> 5.5 Dependent Dependent on serum on serum HCOHCO33

< 5.5< 5.5