ARTERIAL BLOOD GAS: COLLECTION AND INTERPRETATION
description
Transcript of 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
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
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%
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
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.
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
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
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
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
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.
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
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
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.
• 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.
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
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
• 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?
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.
Na+
Regulatory Response to Acidemia
Cl-
H+
Protein- PO4
=,SO4=
Organic acids
normal anion gap
URINE
HCO3-
NH4+ H2PO4
-
PCT
DT
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)
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
Henderson EquationHenderson Equation 24 x pCO2
[H+] = [HCO3
-]
24 x pCO2
[H+] = [HCO3
-]
24 x pCO2 [H+] =
[HCO3-]
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
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
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
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.
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
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
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.
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
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
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
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
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
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)
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
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
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
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
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.
• 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.
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
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.
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.
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.
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.
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
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
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
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
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.
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 -- --
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
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.
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
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
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
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
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
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
MANAGEMENT OF METABOLIC MANAGEMENT OF METABOLIC ALKALOSISALKALOSIS
• Chloride repletionChloride repletion
• Potassium repletionPotassium repletion
• Treatment of hypermineralo-Treatment of hypermineralo-
corticoidismcorticoidism
• DialysisDialysis
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)
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
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
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.
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
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
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
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
• 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.
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.
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
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.
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.
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
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)
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.
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
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
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.
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
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.
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.
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.
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
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
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.
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 -- --
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
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.
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
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.
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.
Na+
Defects in Renal Proton Handling
Cl-
HCO3-
Protein- PO4
=,SO4=
Organic acids
High anion gap
PCT
DTH+
Na+
Defects in Renal Proton Handling
Cl-
HCO3-
H+
Protein- PO4
=,SO4=
Organic acids
High anion gap
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+
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.
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