Arterial Blood GasArterial Blood Gas
Analysis & interpretationAnalysis & interpretation
Mohammed A. El-haj MPH
07/12/2011
What is an ABG?What is an ABG?
 The Components
– pH / PaCO2 / PaO2 / HCO3 / O2sat / BE
 Desired Ranges
– pH - 7.35 - 7.4...
Why Order an ABG?Why Order an ABG?
Aids in establishing a diagnosis
Helps guide treatment plan
Aids in ventilator manag...
LogisticsLogistics
 When to order an arterial line --
– Need for continuous BP monitoring
– Need for multiple ABGs
 Wher...
Acid Base BalanceAcid Base Balance
The body produces acids daily
– 15,000 mmol CO2
– 50-100 mEq Nonvolatile acids
The lu...
Acid Base BalanceAcid Base Balance
Assessment of status via bicarbonate-carbon
dioxide buffer system
 CO2 + H2O <--> H2C...
Normal valuesNormal values
Uncompensated
acidosis
pH
.7 35–.7 45
Uncompensated
alkalosis
Respiratory
alkalosis
CO2
35-45
R...
CompensationCompensation
7.4
7.35 7.45
Partial compensated Partial
Respiratory AcidosisRespiratory Acidosis
↓pH, ↑CO2,↓Ventilation
Causes
– CNS depression
– Pleural disease
– COPD/ARDS
– ...
Respiratory AcidosisRespiratory Acidosis
Acute vs Chronic
– Acute - little kidney involvement. Buffering
via titration vi...
Respiratory AlkalosisRespiratory Alkalosis
 ↑pH, ↓CO2, ↑Ventilation
 ↓ CO2 ↓ HCO3 (↑Cl to balance charges
hyperchloremia...
Respiratory AlkalosisRespiratory Alkalosis
Acute vs. Chronic
– Acute - ↓HCO3 by 2 mEq/L for every 10mmHg
↓ in PCO2
– Chro...
Metabolic AcidosisMetabolic Acidosis
↓pH, ↓HCO3
12-24 hours for complete activation of
respiratory compensation
↓PCO2 b...
The CausesThe Causes
Metabolic Gap Acidosis
– M - Methanol
– U - Uremia
– D - DKA
– P - Paraldehyde
– I - INH
– L - Lactic...
Metabolic AlkalosisMetabolic Alkalosis
 ↑pH, ↑HCO3
 ↑PCO2by 0.7 for every 1mEq/L ↑ in HCO3
 Causes
– Vomiting
– Chronic...
Mixed Acid-Base DisordersMixed Acid-Base Disorders
Patients may have two or more acid-base
disorders at one time
Delta G...
The six steps to ABGs analysisThe six steps to ABGs analysis
Look at the pH if it is normal/acidotic/alkalotic
Look at t...
Sample problemSample problem
pH 7.49
PCO2 40
HCO3 28
Uncompensated metabolic
alkalosis
 Vomiting/dearrhea
 In this ex...
Sample problemSample problem
pH 7.10
PCO2 25
HCO3 7
Uncompensated metabolic
acidosis
 DKA/Dearrhea/shock/bleeding
/sep...
Sample problemSample problem
pH 7.42
PCO2 18
HCO3 11
PO2 150
O2 sat 99%
compensated respiratory
alkalosis
 This pt i...
Sample problemSample problem
pH 7.35
PCO2 60
HCO3 32
PO2 92
O2 sat 96%
 No need for correction
or treatment because
...
Sample problemSample problem
pH 7.37
PCO2 33
HCO3 18
 Metabolic acidosis
 Fully compensated
Sample problemSample problem
pH 7.36
PCO2 62
HCO3 34
PO2 70
O2 sat. 90%
 Respiratory acidosis
 Fully compensated
 ...
Respiratory AlkalosisRespiratory Alkalosis
Most common causes of respiratory
alkalosis are:
1. Hypoxemia ( PaO2< 60mmHg a...
hypoxemiahypoxemia
Conditions causing V/Q (Ventilation
perfusion) miss match
1. Shunt: loss of alveolar surface area
2. D...
Danger a headDanger a head
Hypoxemia
Respiratory
alkalosis
Increased
W.O.B
Muscle
fatigue
Respiratory
Acidosis
Danger a headDanger a head
( Hypoxemia causing fatigue and respiratory
acidosis)
In the path from respiratory alkalosis to...
Case 1Case 1
A 26 year old man with unknown past medical history is brought in to the
ER by ambulance, after friends found...
Case 2Case 2
A 67 year old man with diabetes and early diabetic nephropathy (without
overt renal failure) presents for a r...
Case 3Case 3
A 68 year old woman with metastatic colon cancer presents
to the ER with 1 hour of chest pain and shortness o...
DefinitionsDefinitions
 Acidemia: Blood pH < 7.35
 Alkalemia: Blood pH > 7.45
 Acidosis:is a process that will result i...
Definitions (Continued)Definitions (Continued)
PH: - is a negative logarithm of Hydrogen
ion concentration; and it is the ...
Definitions (Continued)Definitions (Continued)
An acid: - is a hydrogen ion or proton donor, and a
substance which causes ...
Importance of acid-base balanceImportance of acid-base balance
• The hydrogen ion (H+)concentration must
be precisely main...
Acidosis - CNS depression, coma (pH ~
6.9)
Alkalosis - CNS excitability, tetany,
siezures
Hydrogen ion concentration is...
ACID-BASE CALCULATIONSACID-BASE CALCULATIONS
The Henderson equation is easier to use, but
only applies when pH is between...
ph H+ (nmol/l)
7 100
7.1 80
7.2 63
7.3 50
7.36 44
7.4 40
7.44 36
7.5 32
7.6 25
7.7 20
Normal pH:
Arterial blood: 7.35 - 7.45
Venous blood, interstitial fluid: 7.35
Intracellular: 6.0-7.4 (average 7.0)
Regulation of pHRegulation of pH
• *Buffer systems - very rapid (seconds),
incomplete
• *Respiratory responses - rapid (mi...
BackgroundBackground
H+
+ H+
CO3
-
⇔ H2CO3 ⇔ H2O + CO2
-Metabolic Disorders:
Affect HCO3
-:
(Normal 22-26 meq/L)
-Metaboli...
Primary Abnormality in AcidPrimary Abnormality in Acid
Base DisordersBase Disorders
Acidosis Alkalosis
Respiratory ↑ pCO2
...
Primary Abnormality in AcidPrimary Abnormality in Acid
Base DisordersBase Disorders
Acidosis Alkalosis
Respiratory ↑ pCO2 ...
Primary Abnormality in AcidPrimary Abnormality in Acid
Base DisordersBase Disorders
Acidosis Alkalosis
Respiratory ↑ pCO2 ...
Primary Abnormality in AcidPrimary Abnormality in Acid
Base DisordersBase Disorders
Acidosis Alkalosis
Respiratory ↑ pCO2 ...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis ↓ ↓ ↓
Metabolic Alkalosis
Acute Respirator...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis
Metabolic Alkalosis ↑ ↑
Acute Respiratory ...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis
Metabolic Alkalosis ↑ ↑ ↑
Acute Respirator...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis
Metabolic Alkalosis
Acute Respiratory Acid...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis
Metabolic Alkalosis
Acute Respiratory Acid...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis
Metabolic Alkalosis
Acute Respiratory Acid...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis
Metabolic Alkalosis
Acute Respiratory Acid...
Simple Acid-Base Disorders:
Type of Disorder pH PaCO2 [HCO3]
Metabolic Acidosis ↓ ↓ ↓
Metabolic Alkalosis ↑ ↑ ↑
Acute Resp...
CompensationCompensation
For each acid-base disorder , there is a
compensatory response mediated by the
kidneys or the lu...
Compensated Abnormality in AcidCompensated Abnormality in Acid
Base DisordersBase Disorders
Acidosis Alkalosis
1° Respirat...
Compensation (Continued)Compensation (Continued)
Formulas predict normal compensation in
both acute and chronic condition...
Buffer Systems
A substance that can prevent major
changes in the pH of body fluids by
removed or releasing hydrogen ions
...
Bicarbonate buffer system
*Primary extracellular buffer system (>50% of
extracellular buffering)
*Accurate assessment - re...
*CO2 regulated by the lungs - rapidly
*HCO3- is regulated by the kidneys – slowly
*Not powerful
*pKa = 6.1)the pK of a buf...
Protein buffer system
*Most powerful
*75 % of all intracellular buffering
*Hemoglobin
-important extracellular buffer due ...
Plasma protein
*acid buffer
*important intracellular buffer system
Phosphate buffer system
*H2PO4- and HPO42-
*important renal buffering system
*extracellular concentration, 1/12 that of
bi...
Respiratory Responses
 occurs within minutes of alteration in pH due to
stimulation/depression of respiratory centers in ...
Renal Responses
 the kidneys regulate pH by either acidification or
alkalinization of the urine
 complex response that o...
Renal & Respiratory CompensationRenal & Respiratory Compensation
Primary Disorder Primary
change
Predicted Compensatory
Re...
SUMMARY OF SIMPLE ACID-BASE DISORDERS ANDSUMMARY OF SIMPLE ACID-BASE DISORDERS AND
COMPENSATIONCOMPENSATION
Primary Acid-
...
GENERAL ASPECTS OFGENERAL ASPECTS OF
ACID-BASE DISORDERSACID-BASE DISORDERS
 A primary alteration in [H+], [HCO3-] or PCO...
DATA REQUIRED TO DIAGNOSEDATA REQUIRED TO DIAGNOSE
ACID-BASE DISORDERSACID-BASE DISORDERS
 An arterial blood gas shows th...
NORMAL LABORATORYNORMAL LABORATORY
VALUESVALUES
Arterial Blood Gas:
pH 7.35-7.45
[H+] 35-45 nmol/L or neq/L
PCO2 35-45 mm ...
SIMPLE ACID-BASE DISORDERSSIMPLE ACID-BASE DISORDERS
 Simple acid-base disorders have one primary
abnormality.
 The four...
Metabolic AcidosisMetabolic Acidosis
Secondary to
↑ Acid production or
↑ H+
CO3
-
loss
Characterized by low serum H+
CO3...
Anion GapAnion Gap
The anion gap (AG) represents the
difference between the major plasma
cations and anions ,and reflects...
 Why does this help us in patients with metabolic
acidosis?
– Secondary to
 ↑ Acid production or
 ↑ H+
CO3
-
loss
– In ...
Unmeasured anions whichUnmeasured anions which
accumulateaccumulate 
Anion Gap AcidosisAnion Gap Acidosis
Lactate
Keto...
Lactic AcidosisLactic Acidosis
Fundamentally what causes a lactic
acidosis?
Answer: Anaerobic metabolism
The differential diagnosis ofThe differential diagnosis of
Lactic AcidosisLactic Acidosis
Lactic acidosis occurs whenever...
The differential diagnosis ofThe differential diagnosis of
Lactic Acidosis (2)Lactic Acidosis (2)
 Low environmental O2
...
KetoAcidosisKetoAcidosis
Occurs whenever the cells are unable to
utilize glucose
KetoAcidosisKetoAcidosis
Three etiologies
– Diabetic Ketoacidosis
 Primarily in type 1 diabetes mellitus
 Severe, life ...
Metabolic
Acidosis
Anion Gap
Acidosis
NonAnion Gap
Acidosis
Ketoacidosis
Uremic
Acidosis
Lactic
Acidosis
Organic
Acidosis
...
Other anion gap acidosisOther anion gap acidosis
Uremia
– Failure to excrete daily metabolic acid load
– Accumulation of ...
Metabolic
Acidosis
Anion Gap
Acidosis
NonAnion Gap
Acidosis
Ketoacidosis
Uremic
Acidosis
Lactic
Acidosis
Organic
Acidosis
...
Non-anion gap metabolicNon-anion gap metabolic
acidosisacidosis
↑ Bicarbonate loss
 Diarrhea
 Severe Burns
 Urinary lo...
Metabolic
Acidosis
Anion Gap
Acidosis
NonAnion Gap
Acidosis
Ketoacidosis
Uremic
Acidosis
Lactic
Acidosis
Organic
Acidosis
...
Clinical ManifestationClinical Manifestation
 Headache
 Confusion
 Drowsiness
 ↑ RR and depth
 Nausea and vomiting
 ...
Metabolic Acidosis: TreatmentMetabolic Acidosis: Treatment
Treat underlying cause
Alkali replacement
– Acute metabolic a...
Metabolic AlkalosisMetabolic Alkalosis
Generation
Maintenance
Metabolic Alkalosis:Metabolic Alkalosis:
GenerationGeneration
Acid loss
– renal acid losses
 diuretic therapy
 mineralo...
Metabolic Alkalosis:Metabolic Alkalosis:
GenerationGeneration
Alkali gain
– bicarbonate administration
– milk alkali synd...
Metabolic Alkalosis: MaintenanceMetabolic Alkalosis: Maintenance
Decreased GFR
– renal failure
Increased proximal HCO3
-...
Metabolic Alkalosis: TreatmentMetabolic Alkalosis: Treatment
Saline responsive
– intravascular volume expansion with norm...
Respiratory AcidosisRespiratory Acidosis
Think “Murphy’s Law” again
From Brain to alveolus, many problems can
cause hypo...
Respiratory AcidosisRespiratory Acidosis
 Brain
 Spinal Cord
 Peripheral Nerve
 NeuroMuscular Junction
 Lung and Pleu...
Clinical ManifestationClinical Manifestation
 Hypercapnia
 ↑Pulse
 ↑RR
 ↑BP
 Mental cloudiness
 Feeling of fullness ...
Respiratory AlkalosisRespiratory Alkalosis
Hyperventilation  ↓PaCO2  ↑ pH
Etiologies
– Fever
– Pain
– Anxiety
– Pulmon...
MIXED ACID-BASE DISORDERSMIXED ACID-BASE DISORDERS
Mixed acid-base disorders include all
combinations of 2-3 simple acid ...
If there is extreme acidemia or alkalemia,
one could hypothesize multiple acid-base
disorders that that are additive.
• I...
Summary of the Approach toSummary of the Approach to
ABGsABGs
1. Check the pH
2. Check the pCO2
3. Select the appropriate ...
Putting it TogetherPutting it Together
What is the clinical picture?
Generate hypothesis!
What is the pH?
Acidemia Alkalemia
Check HCO3- & PaCO2
Is it respirator...
Case 1Case 1
A 26 year old man with unknown past medical history is
brought in to the ER by ambulance, after friends found...
Case 2Case 2
A 67 year old man with diabetes and early diabetic
nephropathy (without overt renal failure) presents for a
r...
Case 3Case 3
A 68 year old woman with metastatic colon cancer presents
to the ER with 1 hour of chest pain and shortness o...
pH7.34pH7.34, PaCO2 60 , HCO3- 31, PaCO2 60 , HCO3- 31
Primary Disorder Primary
change
Predicted Compensatory
Response
Met...
Case 1Case 1
 A 52 y.o. man with COPD is admitted to the hospital
with a lower extremity cellulitis.
 Hypothesis
 Labs:...
Case 1: AnswerCase 1: Answer
 A 52 y.o. man with COPD is admitted to the hospital
with a lower extremity cellulitis.
 La...
Case 2Case 2
 A 45 y.o. man reports 6 days of persistent nausea and vomiting.
PE  supine BP 100/60 pulse 105; Standing B...
Case 3Case 3
79 y.o. woman with CC of abdominal pain
Patient c/o abdominal pain for 2 days. Pain is
moderately severe & ...
Case 3 (continuedCase 3 (continued))
Labs:
– WBC 18K, 82% neutrophils, 10% bands
– HCT 37
– Na 138, K 4.2 HCO3
-
6 CL 106...
Metabolic
Acidosis
Anion Gap
Acidosis
NonAnion Gap
Acidosis
Ketoacidosis
Uremic
Acidosis
Lactic
Acidosis
Organic
Acidosis
...
Who gets your last ICU bed?Who gets your last ICU bed?
♦♦ 75 y.o. WF with COPD with CC cough & SOB
R.A. ABG  7.35, PaC02...
What is the clinical picture?
Generate hypothesis!
What is the pH?
Acidemia Alkalemia
Check HCO3- & PaCO2
Is it respirator...
Arterial punctureArterial puncture
Problems of taking arterialProblems of taking arterial
blood samplesblood samples
Bleeding
Vessel obstruction
Infection
Allen's test. The radial and ulnar arteries are
occluded by firm pressure while the fist is
clenched. The hand is opened ...
‫لحسن‬ ‫را‬ً ‫شك‬
‫استماعكم‬
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com
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Arterial blood gas analysis & interpretation egh nsg.forum-palestine.com

  1. 1. Arterial Blood GasArterial Blood Gas Analysis & interpretationAnalysis & interpretation Mohammed A. El-haj MPH 07/12/2011
  2. 2. What is an ABG?What is an ABG?  The Components – pH / PaCO2 / PaO2 / HCO3 / O2sat / BE  Desired Ranges – pH - 7.35 - 7.45 – PaCO2 - 35-45 mmHg – PaO2- 80-100 mmHg – HCO3 - 21-27 – O2sat - 95-100% – Base Excess - +/-2 mEq/L
  3. 3. Why Order an ABG?Why Order an ABG? Aids in establishing a diagnosis Helps guide treatment plan Aids in ventilator management Improvement in acid/base management allows for optimal function of medications Acid/base status may alter electrolyte levels critical to patient status/care
  4. 4. LogisticsLogistics  When to order an arterial line -- – Need for continuous BP monitoring – Need for multiple ABGs  Where to place -- the options – Radial – Femoral – Brachial – Dorsalis Pedis – Axillary
  5. 5. Acid Base BalanceAcid Base Balance The body produces acids daily – 15,000 mmol CO2 – 50-100 mEq Nonvolatile acids The lungs and kidneys attempt to maintain balance
  6. 6. Acid Base BalanceAcid Base Balance Assessment of status via bicarbonate-carbon dioxide buffer system  CO2 + H2O <--> H2CO3 <--> HCO3 - + H+  pH = 6.10 + log ([HCO3] / [0.03 x PCO2])
  7. 7. Normal valuesNormal values Uncompensated acidosis pH .7 35–.7 45 Uncompensated alkalosis Respiratory alkalosis CO2 35-45 Respiratory acidosis Metabolic acidosis HCO3 23-27 Metabolic alkalosis
  8. 8. CompensationCompensation 7.4 7.35 7.45 Partial compensated Partial
  9. 9. Respiratory AcidosisRespiratory Acidosis ↓pH, ↑CO2,↓Ventilation Causes – CNS depression – Pleural disease – COPD/ARDS – Musculoskeletal disorders – Compensation for metabolic alkalosis
  10. 10. Respiratory AcidosisRespiratory Acidosis Acute vs Chronic – Acute - little kidney involvement. Buffering via titration via Hb for example  pH ↓by 0.08 for 10mmHg ↑ in CO2 – Chronic - Renal compensation via synthesis and retention of HCO3 (↓Cl to balance charges hypochloremia)  pH ↓by 0.03 for 10mmHg ↑in CO2
  11. 11. Respiratory AlkalosisRespiratory Alkalosis  ↑pH, ↓CO2, ↑Ventilation  ↓ CO2 ↓ HCO3 (↑Cl to balance charges hyperchloremia)  Causes – Intracerebral hemorrhage – Salicylate and Progesterone drug usage – Anxiety ↓lung compliance – Cirrhosis of the liver – Sepsis
  12. 12. Respiratory AlkalosisRespiratory Alkalosis Acute vs. Chronic – Acute - ↓HCO3 by 2 mEq/L for every 10mmHg ↓ in PCO2 – Chronic - Ratio increases to 4 mEq/L of HCO3 for every 10mmHg ↓ in PCO2 – Decreased bicarb reabsorption and decreased ammonium excretion to normalize pH
  13. 13. Metabolic AcidosisMetabolic Acidosis ↓pH, ↓HCO3 12-24 hours for complete activation of respiratory compensation ↓PCO2 by 1.2mmHg for every 1 mEq/L ↓HCO3  The degree of compensation is assessed via the Winter’s Formula PCO2 = 1.5(HCO3) +8 ± 2
  14. 14. The CausesThe Causes Metabolic Gap Acidosis – M - Methanol – U - Uremia – D - DKA – P - Paraldehyde – I - INH – L - Lactic Acidosis – E - Ehylene Glycol – S - Salicylate Non Gap Metabolic Acidosis – Hyperalimentation – Acetazolamide – RTA (Calculate urine anion gap) – Diarrhea – Pancreatic Fistula
  15. 15. Metabolic AlkalosisMetabolic Alkalosis  ↑pH, ↑HCO3  ↑PCO2by 0.7 for every 1mEq/L ↑ in HCO3  Causes – Vomiting – Chronic diarrhea – Hypokalemia – Renal Failure
  16. 16. Mixed Acid-Base DisordersMixed Acid-Base Disorders Patients may have two or more acid-base disorders at one time Delta Gap Delta HCO3 = HCO3 + Change in anion gap >24 = metabolic alkalosis
  17. 17. The six steps to ABGs analysisThe six steps to ABGs analysis Look at the pH if it is normal/acidotic/alkalotic Look at the PaCO2 if it is normal/acidotic/alkalotic Look at the HCO3 if it is normal/acidotic/alkalotic If the pH match with the PCO2 or with the HCO3  If the value goes opposite direction of the pH (determine the compensation). Look at the Po2 and oxygen saturation
  18. 18. Sample problemSample problem pH 7.49 PCO2 40 HCO3 28 Uncompensated metabolic alkalosis  Vomiting/dearrhea  In this example the Bicarb is matching the pH  No compensation (Partial)
  19. 19. Sample problemSample problem pH 7.10 PCO2 25 HCO3 7 Uncompensated metabolic acidosis  DKA/Dearrhea/shock/bleeding /sepsis  In this example the Bicarb is matching the pH  No compensation (Partial)  Severe metabolic acidosis
  20. 20. Sample problemSample problem pH 7.42 PCO2 18 HCO3 11 PO2 150 O2 sat 99% compensated respiratory alkalosis  This pt is hyperventilated for too long (blowing off CO2)
  21. 21. Sample problemSample problem pH 7.35 PCO2 60 HCO3 32 PO2 92 O2 sat 96%  No need for correction or treatment because pH is normal  Compensation is bringing the pH to the side of 7.4 but doesn't to the opposite side (stop in 7.4)
  22. 22. Sample problemSample problem pH 7.37 PCO2 33 HCO3 18  Metabolic acidosis  Fully compensated
  23. 23. Sample problemSample problem pH 7.36 PCO2 62 HCO3 34 PO2 70 O2 sat. 90%  Respiratory acidosis  Fully compensated  E.g. COPD
  24. 24. Respiratory AlkalosisRespiratory Alkalosis Most common causes of respiratory alkalosis are: 1. Hypoxemia ( PaO2< 60mmHg and O2 sat. <90% ). A low PO2 drives increased breathing in spite of CO2 levels. 2. Anxiety 3. Pain
  25. 25. hypoxemiahypoxemia Conditions causing V/Q (Ventilation perfusion) miss match 1. Shunt: loss of alveolar surface area 2. Dead space 3. Diffusion defect
  26. 26. Danger a headDanger a head Hypoxemia Respiratory alkalosis Increased W.O.B Muscle fatigue Respiratory Acidosis
  27. 27. Danger a headDanger a head ( Hypoxemia causing fatigue and respiratory acidosis) In the path from respiratory alkalosis to respiratory acidosis, the acid/base will temporarily appear normal, however the Ve (minute ventilation) will be increased (and probably the W.O.B) Respiratory Alkalosis Normal ABG Respiratory Acidosis
  28. 28. Case 1Case 1 A 26 year old man with unknown past medical history is brought in to the ER by ambulance, after friends found him unresponsive in his apartment. He had last been seen at a party four hours prior. ABG: pH 7.25 Chem : Na+ 137 PCO2 60 K+ 4.5 HCO3 - 26 Cl- 100 PO2 55 HCO3 - 25
  29. 29. Case 2Case 2 A 67 year old man with diabetes and early diabetic nephropathy (without overt renal failure) presents for a routine clinic visit. He is currently asymptomatic. Because of some abnormalities on his routine blood chemistries, you elect to send him for an ABG. ABG: pH 7.35 Chem : Na+ 135 PCO2 34 K+ 5.1 HCO3 - 18 Cl- 110 PO2 92 HCO3 - 16 Cr 1.4 Urine pH: 5.0
  30. 30. Case 3Case 3 A 68 year old woman with metastatic colon cancer presents to the ER with 1 hour of chest pain and shortness of breath. She has no known previous cardiac or pulmonary problems. ABG: pH 7.49 Chem : Na+ 133 PCO2 28 K+ 3.9 HCO3 - 21 Cl- 102 PO2 52 HCO3 - 22
  31. 31. DefinitionsDefinitions  Acidemia: Blood pH < 7.35  Alkalemia: Blood pH > 7.45  Acidosis:is a process that will result in acidemia if left unopposed.  Alkalosis:is a process that will result in alkalemia if left unopposed  Metabolic refers to a disorder that results from a primary alteration in [H+] or [HCO3-].  Respiratory refers to a disorder that results from a primary alteration in PCO2 due to altered CO2 elimination.  Normal HCO3- 24 meq/L; Normal PCO2 40 mm Hg ; Normal pH 7.35-7.45
  32. 32. Definitions (Continued)Definitions (Continued) PH: - is a negative logarithm of Hydrogen ion concentration; and it is the initials of these two wards (puiessence Hydrogen) that mean the power of hydrogen
  33. 33. Definitions (Continued)Definitions (Continued) An acid: - is a hydrogen ion or proton donor, and a substance which causes a rise in H+ concentration on being added to water. A base: - is a hydrogen ion or proton acceptor, and a substance which causes a rise in OH- concentration when added to water. Strength of acids or bases refers to their ability to donate and accept H+ ions respectively.
  34. 34. Importance of acid-base balanceImportance of acid-base balance • The hydrogen ion (H+)concentration must be precisely maintained within a narrow physiological range • Small changes from normal can produce marked changes in enzyme activity & chemical reactions within the body
  35. 35. Acidosis - CNS depression, coma (pH ~ 6.9) Alkalosis - CNS excitability, tetany, siezures Hydrogen ion concentration is most commonly expressed as pH (= negative logarithm of the H+ concentration)
  36. 36. ACID-BASE CALCULATIONSACID-BASE CALCULATIONS The Henderson equation is easier to use, but only applies when pH is between 7.2 and 7.6. For this equation, one must calculate [H+] from pH. [H+] = 40 nEq/L when pH is 7.4. The [H+] increases 10 nEq/L for a 0.1 unit drop in pH. Henderson Eq. [H+] = 24 × PCO2 / [HCO3-]
  37. 37. ph H+ (nmol/l) 7 100 7.1 80 7.2 63 7.3 50 7.36 44 7.4 40 7.44 36 7.5 32 7.6 25 7.7 20
  38. 38. Normal pH: Arterial blood: 7.35 - 7.45 Venous blood, interstitial fluid: 7.35 Intracellular: 6.0-7.4 (average 7.0)
  39. 39. Regulation of pHRegulation of pH • *Buffer systems - very rapid (seconds), incomplete • *Respiratory responses - rapid (minutes), incomplete • *Renal responses - slow (hours to days), complete
  40. 40. BackgroundBackground H+ + H+ CO3 - ⇔ H2CO3 ⇔ H2O + CO2 -Metabolic Disorders: Affect HCO3 -: (Normal 22-26 meq/L) -Metabolic Acidosis ↑ Acid neutralizes HCO3 - ⇒ ↓H+ CO3 - , ↓ pH -Metabolic Alkalosis ↑ H+ CO3 - Production Drives Rxn to Right ⇒ ↓ H+ ⇒ ↑ pH
  41. 41. Primary Abnormality in AcidPrimary Abnormality in Acid Base DisordersBase Disorders Acidosis Alkalosis Respiratory ↑ pCO2 Metabolic H+ + H+ CO3 - ⇔ H2CO3 ⇔ H2O + CO2
  42. 42. Primary Abnormality in AcidPrimary Abnormality in Acid Base DisordersBase Disorders Acidosis Alkalosis Respiratory ↑ pCO2 ↓ pCO2 Metabolic H+ + H+ CO3 - ⇔ H2CO3 ⇔ H2O + CO2
  43. 43. Primary Abnormality in AcidPrimary Abnormality in Acid Base DisordersBase Disorders Acidosis Alkalosis Respiratory ↑ pCO2 ↓ pCO2 Metabolic ↓ H+ CO3 - H+ + H+ CO3 - ⇔ H2CO3 ⇔ H2O + CO2
  44. 44. Primary Abnormality in AcidPrimary Abnormality in Acid Base DisordersBase Disorders Acidosis Alkalosis Respiratory ↑ pCO2 ↓ pCO2 Metabolic ↓ H+ CO3 - ↑ H+ CO3 - H+ + H+ CO3 - ⇔ H2CO3 ⇔ H2O + CO2
  45. 45. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis ↓ ↓ ↓ Metabolic Alkalosis Acute Respiratory Acidosis Chronic Respiratory Acidosis Acute Respiratory Alkalosis Chronic Respiratory Alkalosis
  46. 46. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis Metabolic Alkalosis ↑ ↑ Acute Respiratory Acidosis Chronic Respiratory Acidosis Acute Respiratory Alkalosis Chronic Respiratory Alkalosis
  47. 47. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis Metabolic Alkalosis ↑ ↑ ↑ Acute Respiratory Acidosis Chronic Respiratory Acidosis Acute Respiratory Alkalosis Chronic Respiratory Alkalosis
  48. 48. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis Metabolic Alkalosis Acute Respiratory Acidosis ↓ ↑ Chronic Respiratory Acidosis ↓ ↑ Acute Respiratory Alkalosis Chronic Respiratory Alkalosis
  49. 49. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis Metabolic Alkalosis Acute Respiratory Acidosis ↓ ↑ ↑ Chronic Respiratory Acidosis ↓ ↑ ↑↑ Acute Respiratory Alkalosis Chronic Respiratory Alkalosis
  50. 50. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis Metabolic Alkalosis Acute Respiratory Acidosis Chronic Respiratory Acidosis Acute Respiratory Alkalosis ↑ ↓ Chronic Respiratory Alkalosis ↑ ↓
  51. 51. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis Metabolic Alkalosis Acute Respiratory Acidosis Chronic Respiratory Acidosis Acute Respiratory Alkalosis ↑ ↓ ↓ Chronic Respiratory Alkalosis ↑ ↓ ↓↓
  52. 52. Simple Acid-Base Disorders: Type of Disorder pH PaCO2 [HCO3] Metabolic Acidosis ↓ ↓ ↓ Metabolic Alkalosis ↑ ↑ ↑ Acute Respiratory Acidosis ↓ ↑ ↑ Chronic Respiratory Acidosis ↓ ↑ ↑↑ Acute Respiratory Alkalosis ↑ ↓ ↓ Chronic Respiratory Alkalosis ↑ ↓ ↓↓
  53. 53. CompensationCompensation For each acid-base disorder , there is a compensatory response mediated by the kidneys or the lungs that tends to bring the pH back towards normal. Compensation is never complete (i.e. pH never returns to 7.4). Therefore if the pH < 7.4, the primary process is an acidosis. If the pH > 7.4 the primary process is an alkalosis
  54. 54. Compensated Abnormality in AcidCompensated Abnormality in Acid Base DisordersBase Disorders Acidosis Alkalosis 1° Respiratory Compensation ↑ pCO2 ↓ pCO2 1° Metabolic Compensation ↓ H+ CO3 - ↑ H+ CO3 - ↑ H+ CO3 - ↓ H+ CO3 - ↑ pCO2 ↓ pCO2 H+ + H+ CO3 - ⇔ H2CO3 ⇔ H2O + CO2
  55. 55. Compensation (Continued)Compensation (Continued) Formulas predict normal compensation in both acute and chronic conditions. Inadequate compensation tells you that something else is wrong! Metabolic compensation takes time and is more complete in chronic conditions than acutely
  56. 56. Buffer Systems A substance that can prevent major changes in the pH of body fluids by removed or releasing hydrogen ions ,they can act quickly to prevent excessive changes in hydrogen ion concentration Bicarbonate, phosphate and protein buffering systems are the three major buffering systems
  57. 57. Bicarbonate buffer system *Primary extracellular buffer system (>50% of extracellular buffering) *Accurate assessment - readily calculated from PCO2 and pH using available blood gas machines *Consists of carbonic acid (weak acid) and bicarbonate
  58. 58. *CO2 regulated by the lungs - rapidly *HCO3- is regulated by the kidneys – slowly *Not powerful *pKa = 6.1)the pK of a buffer system identifies the pH at which the concentration of acid and base in that system is equal) 33222 HCOHCOHCOOH +↔↔+ +
  59. 59. Protein buffer system *Most powerful *75 % of all intracellular buffering *Hemoglobin -important extracellular buffer due to large concentration of hemoglobin in blood -buffering capacity varies with oxygenation -reduced hemoglobin is a weaker acid than oxyhemoglobin -dissociation of oxyhemoglobin results in more base available to combine w/ H+
  60. 60. Plasma protein *acid buffer *important intracellular buffer system
  61. 61. Phosphate buffer system *H2PO4- and HPO42- *important renal buffering system *extracellular concentration, 1/12 that of bicarbonate *pKa = 6.8 *phosphate is concentrated in the renal tubules
  62. 62. Respiratory Responses  occurs within minutes of alteration in pH due to stimulation/depression of respiratory centers in the CNS  H+ acts directly on respiratory center in Medulla Oblongata  alveolar ventilation increases/decreases in response to changes in CO2  alveolar ventilation is inversely proportional to PaCO2 *2 x ventilation pH 7.4 to 7.63 *¼ ventilation pH 7.4 to 7.0  incomplete response because as the change in alveolar ventilation brings pH back towards normal, the stimulus responsible for the change in ventilation decreases .
  63. 63. Renal Responses  the kidneys regulate pH by either acidification or alkalinization of the urine  complex response that occurs primarily in the proximal renal tubules  with acidosis, rate of H+ secretion exceeds HCO3- filtration  with alkalosis, rate of HCO3- filtration exceeds H+ secretion  occurs over hours/days, and is capable of nearly complete restoration of acid/base balance
  64. 64. Renal & Respiratory CompensationRenal & Respiratory Compensation Primary Disorder Primary change Predicted Compensatory Response Metabolic acidosis ↓ HCO3 1.2 ↓ PaCO2 per 1 meg ↓ HCO3 Metabolic Alkalosis ↑ HCO3 .7 ↑ PaCO2 per 1meq ↑ HCO3 Respiratory acidosis: Acute ↑PaCO2 1 meq ↑ HCO3 per 10 mm ↑PaCO2 Respiratory acidosis: Chronic ↑PaCO2 3.5 meq ↑ HCO3 per 10 mm ↑PaCO2 Respiratory alkalosis: Acute ↓PaCO2 2 meq ↓HCO3 per 10mm ↓ PaCO2 Respiratory alkalosis: Chronic ↓PaCO2 4 meq ↓HCO3 per 10mm ↓ PaCO2
  65. 65. SUMMARY OF SIMPLE ACID-BASE DISORDERS ANDSUMMARY OF SIMPLE ACID-BASE DISORDERS AND COMPENSATIONCOMPENSATION Primary Acid- Base Disorder Primary Defect Effect on pH Compensatory Response Expected Range of Compensation Limits of Compensatio n Respiratory Acidosis Hypoventilati on (↑PCO2) ↓ HCO3- Generation ↑ [HCO3-] = 1-4 mEq/L for each 10 mm Hg ↑ PCO2 [HCO3-] = 45 mEq/L Respiratory Alkalosis Hyperventilati on (↓PCO2) ↑ HCO3- Consumption ↓ [HCO3-] = 2-5 mEq/L for each 10 mm Hg ↓ PCO2 [HCO3-] = 12-15 mEq/L Metabolic Acidosis Loss of HCO3- or gain of H+(↑ HCO3-) ↓ Increase in Ventilation (↓PCO2) PCO2 = 1.5[HCO3-] + 8 PCO2 = 12-14 mm Hg Metabolic Alkalosis Gain of HCO3- or loss of H+ (↓ HCO3-) ↑ Decrease in Ventilation (↑PCO2 ( ↑ PCO2 = 0.6 mm Hg for each 1 mEq/L ↑ [HCO3-] PCO2 = 55 mm Hg
  66. 66. GENERAL ASPECTS OFGENERAL ASPECTS OF ACID-BASE DISORDERSACID-BASE DISORDERS  A primary alteration in [H+], [HCO3-] or PCO2 results in abnormal pH.  The body has several mechanisms to correct pH towards the normal range. -In the acute phase (minutes to hours), the extra- and intra- cellular buffer systems (most importantly the bicarbonate system) minimize the pH changes. - In the chronic phase (hours to days), renal or respiratory compensation partially or completely restore pH towards normal.  There are limits to both types of compensation.  Compensation does not result in over correction of pH.
  67. 67. DATA REQUIRED TO DIAGNOSEDATA REQUIRED TO DIAGNOSE ACID-BASE DISORDERSACID-BASE DISORDERS  An arterial blood gas shows the blood pH, PCO2 and [HCO3-].  A chemistry panel shows the [total CO2], [Cl-], [K+] and [Na+], [glucose], [BUN] and [creatinine].  The [total CO2] is the sum of the measured [CO2] + [HCO3-]. Thus the [HCO3-] from the blood gas and the [total CO2] from the electrolyte panel usually are within 2 mEq/L. Otherwise the measurements are in error or were taken at different times.
  68. 68. NORMAL LABORATORYNORMAL LABORATORY VALUESVALUES Arterial Blood Gas: pH 7.35-7.45 [H+] 35-45 nmol/L or neq/L PCO2 35-45 mm Hg [HCO3-] 22-26 mmol/L or mEq/L Plasma Electrolytes [Na+] 135-145 mEq/L [K+ ] 3.5-5.0 mEq/L [Cl-] 96-109 mEq/L [total CO2] 24-30 mEq/L
  69. 69. SIMPLE ACID-BASE DISORDERSSIMPLE ACID-BASE DISORDERS  Simple acid-base disorders have one primary abnormality.  The four primary disorders are respiratory acidosis, respiratory alkalosis, metabolic acidosis and metabolic alkalosis.  Mixed acid-base disorders have more than one abnormality. Two to three primary disorders can be combined together to result in a mixed disorder.
  70. 70. Metabolic AcidosisMetabolic Acidosis Secondary to ↑ Acid production or ↑ H+ CO3 - loss Characterized by low serum H+ CO3 - ( by hyperventilation  ↓ PCO2 ⇒ ↓ HCO3- ) Divided into two categories: – Anion gap metabolic acidosis (High anion gap) – NonAnion gap metabolic acidosis (Normal anion gap)
  71. 71. Anion GapAnion Gap The anion gap (AG) represents the difference between the major plasma cations and anions ,and reflects usually unmeasured anions such as sulfate. Anion Gap = [Na+ ] - ( [H+ CO3 - ]+ [Cl- ] ) Normal 14 +/- 2
  72. 72.  Why does this help us in patients with metabolic acidosis? – Secondary to  ↑ Acid production or  ↑ H+ CO3 - loss – In disorders associated with ↑ acid production there anions accumulate  ↑ anion gap whereas – In disorders associated with ↑ H+ CO3 - loss, there is no accumulation of unmeasured anions and the anion gap is normal
  73. 73. Unmeasured anions whichUnmeasured anions which accumulateaccumulate  Anion Gap AcidosisAnion Gap Acidosis Lactate Ketones Sulfates and phosphates Other organic acids
  74. 74. Lactic AcidosisLactic Acidosis Fundamentally what causes a lactic acidosis? Answer: Anaerobic metabolism
  75. 75. The differential diagnosis ofThe differential diagnosis of Lactic AcidosisLactic Acidosis Lactic acidosis occurs whenever the cells are unable to utilize aerobic respiration: i.e. whenever the cells are unable to obtain or utilize oxygen Consider Murphy’s law: “Whatever can go wrong will go wrong!” (i.e. take each step in oxygen absorption and distribution—any one of them can go away and cause lactic acidosis.)
  76. 76. The differential diagnosis ofThe differential diagnosis of Lactic Acidosis (2)Lactic Acidosis (2)  Low environmental O2  Inability to absorb O2  O2 unable to bind Hg  Unable to pump O2  Tissues unable to utilize O2  High altitude  Lung Disease  CO poisoning  Shock (cardiogenic)  Septic shock  Focal vascular obstruction  Cyanide poisoning
  77. 77. KetoAcidosisKetoAcidosis Occurs whenever the cells are unable to utilize glucose
  78. 78. KetoAcidosisKetoAcidosis Three etiologies – Diabetic Ketoacidosis  Primarily in type 1 diabetes mellitus  Severe, life threatening  Often associated with precipitating illness – Starvation ketoacidosis  Mild acidosis – Alcoholic ketoacidosis  Mild acidosis
  79. 79. Metabolic Acidosis Anion Gap Acidosis NonAnion Gap Acidosis Ketoacidosis Uremic Acidosis Lactic Acidosis Organic Acidosis Lung Disease CO poisening Shock (cardiogenic) Septic shock Focal vascular obstruction Cyanide poisening DKA (Type 1) Starvation Alcoholic
  80. 80. Other anion gap acidosisOther anion gap acidosis Uremia – Failure to excrete daily metabolic acid load – Accumulation of phosphates and sulfates Organic acidosis – Methanol – Ethylene Glycol – Salicylates
  81. 81. Metabolic Acidosis Anion Gap Acidosis NonAnion Gap Acidosis Ketoacidosis Uremic Acidosis Lactic Acidosis Organic Acidosis Lung Disease CO poisening Shock (cardiogenic) Septic shock Focal vascular obstruction Cyanide poisening DKA (Type 1) Starvation Alcoholic Methanol Ethylene Glycol Salicylate intoxication
  82. 82. Non-anion gap metabolicNon-anion gap metabolic acidosisacidosis ↑ Bicarbonate loss  Diarrhea  Severe Burns  Urinary loss (renal tubular acidosis)
  83. 83. Metabolic Acidosis Anion Gap Acidosis NonAnion Gap Acidosis Ketoacidosis Uremic Acidosis Lactic Acidosis Organic Acidosis Lung Disease CO poisening Shock (cardiogenic) Septic shock Focal vascular obstruction Cyanide poisening DKA (Type 1) Starvation Alcoholic Methanol Ethylene Glycol Salicylate intoxication Diarrhea Burns (severe) RTA
  84. 84. Clinical ManifestationClinical Manifestation  Headache  Confusion  Drowsiness  ↑ RR and depth  Nausea and vomiting  Peripheral vasodilation and decreased Cardiac output (pH ↓7 )  ↓BP  Hyperkalemias
  85. 85. Metabolic Acidosis: TreatmentMetabolic Acidosis: Treatment Treat underlying cause Alkali replacement – Acute metabolic acidosis  indicated when is pH less than ~7.15  goal is to raise serum [HCO3] to ~15mmol/L  bicarbonate dose = 0.5 x BW (kg) x{[HCO3]desired - [HCO3]actual} – Chronic metabolic acidosis  goal of treatment is to prevent long term sequelae  serum [HCO3] should be normalized
  86. 86. Metabolic AlkalosisMetabolic Alkalosis Generation Maintenance
  87. 87. Metabolic Alkalosis:Metabolic Alkalosis: GenerationGeneration Acid loss – renal acid losses  diuretic therapy  mineralocorticoid excess  Cushing’s syndrome  severe potassium depletion  Bartter’s syndrome  Liddle’s syndrome – gastrointestinal losses  gastric acid loss  chloride diarrhea
  88. 88. Metabolic Alkalosis:Metabolic Alkalosis: GenerationGeneration Alkali gain – bicarbonate administration – milk alkali syndrome – infusion of organic anions  citrate  acetate  lactate – rapid correction of chronic hypercapnia
  89. 89. Metabolic Alkalosis: MaintenanceMetabolic Alkalosis: Maintenance Decreased GFR – renal failure Increased proximal HCO3 - reabsorption – chloride depletion Increased distal tubular H+ secretion – hypokalemia
  90. 90. Metabolic Alkalosis: TreatmentMetabolic Alkalosis: Treatment Saline responsive – intravascular volume expansion with normal saline – potassium repletion Saline resistant – potassium repletion – mineralocorticoid antagonists – acetazolamide
  91. 91. Respiratory AcidosisRespiratory Acidosis Think “Murphy’s Law” again From Brain to alveolus, many problems can cause hypoventilation  ↑ PaCO2  ↓pH (Respiratory acidosis)
  92. 92. Respiratory AcidosisRespiratory Acidosis  Brain  Spinal Cord  Peripheral Nerve  NeuroMuscular Junction  Lung and Pleural disease  Stroke  Drug Intoxication  C spine injury,  Guillan Barre  Myasthenia Gravis  Asthma, COPD, ARDS, etc
  93. 93. Clinical ManifestationClinical Manifestation  Hypercapnia  ↑Pulse  ↑RR  ↑BP  Mental cloudiness  Feeling of fullness in the head  ↑ICP  Headache  Hyperkalemia
  94. 94. Respiratory AlkalosisRespiratory Alkalosis Hyperventilation  ↓PaCO2  ↑ pH Etiologies – Fever – Pain – Anxiety – Pulmonary disease – Sepsis – Salicylate intoxication – Neurologic disorders
  95. 95. MIXED ACID-BASE DISORDERSMIXED ACID-BASE DISORDERS Mixed acid-base disorders include all combinations of 2-3 simple acid base disorders. One must be able to recognize mixed acid- base disorders. This can be accomplished by examining the degree of compensation and calculating an anion gap. If the pH, PCO2 and [HCO3-] do not fit the rules of compensation for a simple disorder, one must hypothesize that there is a mixed acid-base disorder (or hypothesize that there is an error in the data).
  96. 96. If there is extreme acidemia or alkalemia, one could hypothesize multiple acid-base disorders that that are additive. • If there is a mild acidemia or alkalemia, or pH is normal, particularly with an anion gap one could hypothesize multiple acid-base disorders that cancel each other out.
  97. 97. Summary of the Approach toSummary of the Approach to ABGsABGs 1. Check the pH 2. Check the pCO2 3. Select the appropriate compensation formula 4. Determine if compensation is appropriate 5. Check the anion gap 6. If the anion gap is elevated, check the delta-delta 7. If a metabolic acidosis is present, check urine pH 8. Generate a differential diagnosis
  98. 98. Putting it TogetherPutting it Together
  99. 99. What is the clinical picture? Generate hypothesis! What is the pH? Acidemia Alkalemia Check HCO3- & PaCO2 Is it respiratory or metabolic? Check: Is compensation appropriate? Check Anion Gap Reach Final Diagnosis Step 1 Step 2 Step 3 Step 4 Step 5 Step 6
  100. 100. Case 1Case 1 A 26 year old man with unknown past medical history is brought in to the ER by ambulance, after friends found him unresponsive in his apartment. He had last been seen at a party four hours prior. ABG: pH 7.25 Chem 7: Na+ 137 PCO2 60 K+ 4.5 HCO3 - 26 Cl- 100 PO2 55 HCO3 - 25
  101. 101. Case 2Case 2 A 67 year old man with diabetes and early diabetic nephropathy (without overt renal failure) presents for a routine clinic visit. He is currently asymptomatic. Because of some abnormalities on his routine blood chemistries, you elect to send him for an ABG. ABG: pH 7.35 Chem 7: Na+ 135 PCO2 34 K+ 5.1 HCO3 - 18 Cl- 110 PO2 92 HCO3 - 16 Cr 1.4 Urine pH: 5.0
  102. 102. Case 3Case 3 A 68 year old woman with metastatic colon cancer presents to the ER with 1 hour of chest pain and shortness of breath. She has no known previous cardiac or pulmonary problems. ABG: pH 7.49 Chem 7: Na+ 133 PCO2 28 K+ 3.9 HCO3 - 21 Cl- 102 PO2 52 HCO3 - 22
  103. 103. pH7.34pH7.34, PaCO2 60 , HCO3- 31, PaCO2 60 , HCO3- 31 Primary Disorder Primary change Predicted Compensatory Response Metabolic acidosis ↓ HCO3 1.2 ↓ PaCO2 per 1 meg ↓ HCO3 Metabolic Alkalosis ↑ HCO3 .7 ↑ PaCO2 per 1meq ↑ HCO3 Respiratory acidosis: Acute ↑PaCO2 1 meq ↑ HCO3 per 10 mm ↑PaCO2 Respiratory acidosis: Chronic ↑PaCO2 3.5 meq ↑ HCO3 per 10 mm ↑PaCO2 Respiratory alkalosis: Acute ↓PaCO2 2 meq ↓HCO3 per 10mm ↓ PaCO2 Respiratory alkalosis: Chronic ↓PaCO2 4 meq ↓HCO3 per 10mm ↓ PaCO2
  104. 104. Case 1Case 1  A 52 y.o. man with COPD is admitted to the hospital with a lower extremity cellulitis.  Hypothesis  Labs: Na+ 139, K+ 4.9, Cl- 98, HCO3- 31  ABG: pH 7.34, PaCO2 60, PaO2 69  Is he acidemic or alkalemic?  Is this metabolic (from sepsis) or respiratory (from COPD)?  Is this acute or chronic? Why does that matter?
  105. 105. Case 1: AnswerCase 1: Answer  A 52 y.o. man with COPD is admitted to the hospital with a lower extremity cellulitis.  Labs: Na+ 139, K+ 4.9, Cl- 98, HCO3- 31  ABG: pH 7.34, PaCO2 60, PaO2 69  Why is he acidemic?  Is this metabolic (from sepsis) or respiratory (from COPD)?  Is this acute or chronic? Why does that matter?  Dx: Chronic Respiratory Acidosis – Not from sepsis – No need for intubation or ICU care – Note AG 10
  106. 106. Case 2Case 2  A 45 y.o. man reports 6 days of persistent nausea and vomiting. PE  supine BP 100/60 pulse 105; Standing BP 85/55 pulse 125. Neck veins are flat  Hypotheses?  Labs: – Na+ 140, K+ 2.2, Cl- 86, HCO3 42 BUN 80, Cr 1.9 – ABG: pH 7.53, PaCO2 53, PaO2 82 – Urine Na+ 2 meg/L  Acidemic or Alkalemic?  Metabolic or Respiratory?  What is his acid base disorder?  Why is he alkalemic?  How would you fix it? What’s with the urine sodium?  Answer: Metabolic alkalosis. Correct with NaCL
  107. 107. Case 3Case 3 79 y.o. woman with CC of abdominal pain Patient c/o abdominal pain for 2 days. Pain is moderately severe & diffuse, associated with vomiting. She reports passing no bowel movements or flatus for 2 days. PE: Elderly appearing woman in moderate distress; Vital signs T 38.5, RR 20, BP 115/60, HR 95. Abdominal exam: absent bowel sounds, diffusely distended, mild tenderness, without rebound or guarding. Rectal FOBT negative
  108. 108. Case 3 (continuedCase 3 (continued)) Labs: – WBC 18K, 82% neutrophils, 10% bands – HCT 37 – Na 138, K 4.2 HCO3 - 6 CL 106 BUN 45 Cr. 1.0 Glucose 110 – ABG: pH 7.10, PaCO2 20mm Hg, PaO2 90 What is her acid base disorder? What does it tell you?
  109. 109. Metabolic Acidosis Anion Gap Acidosis NonAnion Gap Acidosis Ketoacidosis Uremic Acidosis Lactic Acidosis Organic Acidosis Lung Disease CO poisening Shock (cardiogenic) Septic shock Focal vascular obstruction Cyanide poisening DKA (Type 1) Starvation Alcoholic Methanol Ethylene Glycol Salicylate intoxication Diarrhea Burns (severe) RTA
  110. 110. Who gets your last ICU bed?Who gets your last ICU bed? ♦♦ 75 y.o. WF with COPD with CC cough & SOB R.A. ABG  7.35, PaC02 60, Pa02 48. ♦♦ 70 y.o. WM with COPD with CC purulent sputum, SOB. ABG on 4L  7.2, PaC02 60, Pa02 of 70
  111. 111. What is the clinical picture? Generate hypothesis! What is the pH? Acidemia Alkalemia Check HCO3- & PaCO2 Is it respiratory or metabolic? Check: Is compensation appropriate? Check Anion Gap Reach Final Diagnosis Step 1 Step 2 Step 3 Step 4 Step 5 Step 6
  112. 112. Arterial punctureArterial puncture
  113. 113. Problems of taking arterialProblems of taking arterial blood samplesblood samples Bleeding Vessel obstruction Infection
  114. 114. Allen's test. The radial and ulnar arteries are occluded by firm pressure while the fist is clenched. The hand is opened and the arteries released one at a time to check their ability to return blood flow to the hand
  115. 115. ‫لحسن‬ ‫را‬ً ‫شك‬ ‫استماعكم‬

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