acid-base disorders

• CSN VittalCSN Vittal• CSN VittalCSN Vittal

• pH : 7.35 – 7.45

• PaCO2 : 35 – 45 mm Hg

• PaO2 : > 70 mm Hg

• HCO3- : 22 – 26 mEq/L

• BE : -2.0 to +2.0 mEq/L

• Depends on Acid : Base

• Proportional to HCO3- / H2CO3

• pH change to HCO3- is metabolic

• pH change to H2CO3 (CO2) is respiratory

• Difference between patient’s actual buffering capacity and normal buffering capacity• Normal Values : +/- 2.0 mEq/L

• Follows changes in HCO3-

1. Carbon dioxide (since CO2 and H2O form HCO3-, and H+ in

the presence of carbonic anhydrase)2. Production of nonvolatile acids from the metabolism of proteins and other organic molecules3. Loss of bicarbonate in faeces or urine4. Intake of acids or acid precursors

1. Use of hydrogen ions in the metabolism of various organic anions

2. Loss of acid in the vomitus or urine

• Consider the history• Look for clues on physical exam• Examine the electrolytes

– PCO2

– Potassium– Anion Gap

• Review other laboratory data• Analyze the arterial blood gas

• Loose Stools and decreased Intake• Polyphagia, Polydipsia of DM• History of Renal Insufficiency• Possibilty of Poisoning in Toddlers• Fever and Increasing Sickness• Any signs of CNS Disorder• Any Medication History

• Any Signs of Sepsis• Any Signs of Dehydration• Any Signs of Meningeal irritation• Any Signs of Addison’s Disease• Any Signs of Neuromuscular

Disease

5 Step Approach

1. pH: Normal, acid or alkaline?

2. Respiratory component – Is it like pH?

3. Metabolic component – Is SBE like pH?

4. Magnitude of change – minor, moderate or major?

5. Recognizing compensation

Step 1

Acidemic or Alkalotic?Acidemic or Alkalotic?

• Acidemic : pH < 7.35

• Alkalotic : pH > 7.45

A normal pH does not rule out acid base disorder

Step 2Respiratory Component : PCO2

If the respiratory change is like the pH,

i.e., both acid, then

the cause is respiratory

The exception : when the metabolic component is also acid -> both are contributing to the acid pH.

If the PCO2 is not like the pH, i.e., the PCO2 is low (alkaline), then the primary problem is not respiratory; the low PCO2 is a compensation for

the metabolic acidosis.

Step 3Metabolic Component : SBE

If the Standard Base Excess (SBE) is the component which is like the pH, i.e., both

acid (a negative base excess), then the cause is metabolic.

The exception, - is when the respiratory component is also acid; then both contribute to the acid pH.

If the SBE is not like the pH, i.e., the SBE is alkaline, then the primary problem is not metabolic; the high SBE is a compensation for the respiratory acidosis.

Step 4Magnitude of DisturbanceMagnitude of Disturbance

Just try to judge minor, moderate, or major, for clinical comment.

Whenever the pH is normal, i.e., pH = 7.4. then the PCO2 and the SBE are equal and opposite.

The slope for BE / PCO2 when pH = 7.4 gives us this ratio:

3 units of change in SBE = 5 mm Hg change in PCO2.

AdjectivePCO2

mmHg

SBEmEq/L

Alkalosis Severe <18 <13

Marked 18 to 25 13 to 9

Moderate 25 to 30 9 to 6

Mild 30 to 34 6 to 4

Minimal 34 to 37 4 to 2

Normal Normal 37 to 43 2 to -2

Acidosis Minimal 43 to 46 -2 to -4

Mild 46 to 50 -4 to -6

Moderate 50 to 55 -6 to -9

Marked 55 to 62 -9 to -13

Severe > 62 to <-13

Step 5

Recognizing compensationRecognizing compensation

• If a pt. with a respiratory problem has a high PCO2, e.g., 60 mmHg (raised by 20mmHg) then for "complete compensation" the SBE would have to be about 12

(using the 5 to 3 ratio given above). • If the SBE were zero = "no compensation" -

typical of an acute process of recent onset.

Most likely - the patient is somewhere in the middle (SBE = 6 mEq/L) which is typical for "compensation for chronic respiratory acidosis”.

Inverse example:

• if a patient with a metabolic problem has a low SBE, e.g., -12, then the PCO2 would have to be reduced by hyperventilation to about 20 mmHg to achieve "complete compensation".

• If the PCO2 were still normal then there would be "no compensation".

Again, far the most likely, the patient is somewhere in the middle (30 mmHg) which is typical for "compensation for metabolic acidosis".

Step 5

Recognizing compensationRecognizing compensation

Logical Approach to an Acid pH

1. Are the pH and the PCO2 both acid? If so the PCO2 contributes to the condition.

2. If not (i.e., PCO2 is alkaline) then the metabolic component is the cause and the PCO2 is compensatory.

3. Is either PCO2 or SBE normal? Because, if so, there is no compensation and you have a pure acidosis: (pure respiratory acidosis occurs fairly frequently, metabolic rarely)

4. To be typical the compensation must lie roughly half way between no compensation and complete compensation - use the rule 3 mEq/L = 5 mmHg to work out complete compensation.

5. If both components are acid, you don't have a typical single condition, you have a combined metabolic and respiratory acidosis.

Example A

pH = 7.2, PCO2 = 60 mmHg, SBE = 0 mEq/L

• Overall change is acid. • Respiratory change is also acid - therefore

contributing to the acidosis. • SBE is normal - no metabolic compensation. • Therefore, pure respiratory acidosis. • Typical of acute respiratory depression.• Magnitude: marked respiratory acidosis

Example BpH = 7.35, PCO2 = 60 mmHg, SBE = 7 mEq/L

• Overall change is slightly acid. • Respiratory change is also acid - therefore contributing to

the acidosis. • Metabolic change is alkaline - therefore compensatory. • The respiratory acidosis is 20 mmHg on the acid side of

normal (40). To completely balance plus 20 would require 20 * 3 / 5 = 12 mEq/L SBE

• The actual SBE is 7 mEq/L, which is roughly half way between 0 and 12, i.e., a typical metabolic compensation.

• Magnitude: marked respiratory acidosis with moderate metabolic compensation

Example C

pH = 7.15, PCO2 = 60 mmHg, SBE = - 6 mEq/L• Overall change is acid. • Respiratory change is acid - therefore contributing to the

acidosis. • Metabolic change is also acid - therefore combined

acidosis. • The components are pulling in same direction - neither

can be compensating for the other • Magnitude: marked respiratory acidosis and mild

metabolic acidosis

Example D

pH= 7.30, PCO2 = 30 mmHg, SBE = -10 mEq/L

• Overall change is acid. • Resp. change is alkaline - therefore NOT contributing to the acidosis. • Metabolic change is acid - therefore responsible for the acidosis. • The components are pulling in opposite directions. SBE is the acid

component so it is primarily a metabolic problem with some respiratory compensation

• The metabolic acidosis is 10 mEq/L on the acid side of normal (0). To completely balance 10 would require 10 * 5 / 3 = 17 mmHg respiratory alkalosis (= 23 mmHg)

• The actual PCO2 is 30 mEq/L which is roughly half way between 23 and 40, i.e., a typical respiratory compensation..

• Magnitude: marked metabolic acidosis with mild respiratory compensation.

Respiratory AcidosisRespiratory Acidosis

AcuteAcute The PaCOThe PaCO22 is elevated above the upper limit of the is elevated above the upper limit of the

reference range (i.e., > 45 mm Hg) with an reference range (i.e., > 45 mm Hg) with an accompanying acidemia (i.e., pH < 7.35).accompanying acidemia (i.e., pH < 7.35).

ChronicChronic The PaCOThe PaCO22 is elevated above the upper limit of the is elevated above the upper limit of the

reference range, with a normal or near-normal pH reference range, with a normal or near-normal pH secondary to renal compensation and an elevated secondary to renal compensation and an elevated serum bicarbonate (i.e., HCOserum bicarbonate (i.e., HCO33

-- > 30 mEq/L.) > 30 mEq/L.)

AcuteAcute The PaCOThe PaCO22 is elevated above the upper limit of the is elevated above the upper limit of the

reference range (i.e., > 45 mm Hg) with an reference range (i.e., > 45 mm Hg) with an accompanying acidemia (i.e., pH < 7.35).accompanying acidemia (i.e., pH < 7.35).

ChronicChronic The PaCOThe PaCO22 is elevated above the upper limit of the is elevated above the upper limit of the

reference range, with a normal or near-normal pH reference range, with a normal or near-normal pH secondary to renal compensation and an elevated secondary to renal compensation and an elevated serum bicarbonate (i.e., HCOserum bicarbonate (i.e., HCO33

-- > 30 mEq/L.) > 30 mEq/L.)

Respiratory DisturbancesRespiratory Disturbances

Is it Acute or Chronic ?Is it Acute or Chronic ? Is it Acute or Chronic ?Is it Acute or Chronic ?

Respiratory Acidosis

Acute: pH decrease

= 0.008 X (PaCO2 – 40)

Respiratory Alkalosis

Acute: pH Increase

= 0.008 X (PaCO2 – 40)

Chronic: pH decrease

= 0.003 X (PaCO2 – 40)

Chronic: pH Increase

= 0.003 X (PaCO2 – 40)

Respiratory Acidosis - AcuteRespiratory Acidosis - Acute

Abrupt failure of ventilation, Abrupt failure of ventilation, PaCO PaCO22

Neuromuscular disorders Neuromuscular disorders CNS Depression CNS Depression Brain stem InjuryBrain stem Injury

Musculoskeletal DisordersMusculoskeletal Disorders GBSGBS MyastheniaMyasthenia

Airway Obstructive DiseaseAirway Obstructive Disease AsthmaAsthma Foreign BodyForeign Body Laryngeal EdemaLaryngeal Edema Pulmonary EmbolismPulmonary Embolism

DrugsDrugs SedativesSedatives BarbituratesBarbiturates

Abrupt failure of ventilation, Abrupt failure of ventilation, PaCO PaCO22

Neuromuscular disorders Neuromuscular disorders CNS Depression CNS Depression Brain stem InjuryBrain stem Injury

Musculoskeletal DisordersMusculoskeletal Disorders GBSGBS MyastheniaMyasthenia

Airway Obstructive DiseaseAirway Obstructive Disease AsthmaAsthma Foreign BodyForeign Body Laryngeal EdemaLaryngeal Edema Pulmonary EmbolismPulmonary Embolism

DrugsDrugs SedativesSedatives BarbituratesBarbiturates

Respiratory Acidosis - Respiratory Acidosis - ChronicChronic

COPDCOPD

Obesity hypoventilation syndrome Obesity hypoventilation syndrome (i.e., Pickwickian syndrome)(i.e., Pickwickian syndrome)

Neuromuscular disorders Neuromuscular disorders Amyotrophic lateral sclerosisAmyotrophic lateral sclerosis

Severe restrictive ventilatory Severe restrictive ventilatory defectsdefects Interstitial fibrosis and Interstitial fibrosis and

Thoracic deformitiesThoracic deformities

COPDCOPD

Obesity hypoventilation syndrome Obesity hypoventilation syndrome (i.e., Pickwickian syndrome)(i.e., Pickwickian syndrome)

Neuromuscular disorders Neuromuscular disorders Amyotrophic lateral sclerosisAmyotrophic lateral sclerosis

Severe restrictive ventilatory Severe restrictive ventilatory defectsdefects Interstitial fibrosis and Interstitial fibrosis and

Thoracic deformitiesThoracic deformities


Symptoms:Symptoms:

Symptoms of the disease that causes Symptoms of the disease that causes respiratory acidosis are usually noticeablerespiratory acidosis are usually noticeable shortness of breathshortness of breath easy fatigueeasy fatigue chronic cough, or chronic cough, or wheezing.wheezing.

When respiratory acidosis becomes When respiratory acidosis becomes severe, severe, ConfusionConfusion irritability, or irritability, or lethargy may be apparent.lethargy may be apparent.

Symptoms:Symptoms:

Symptoms of the disease that causes Symptoms of the disease that causes respiratory acidosis are usually noticeablerespiratory acidosis are usually noticeable shortness of breathshortness of breath easy fatigueeasy fatigue chronic cough, or chronic cough, or wheezing.wheezing.

When respiratory acidosis becomes When respiratory acidosis becomes severe, severe, ConfusionConfusion irritability, or irritability, or lethargy may be apparent.lethargy may be apparent.


Treatment:Treatment:

Treat the underlying causeTreat the underlying cause Improve alveolar gas exchangeImprove alveolar gas exchange Assisted ventilationAssisted ventilation

Treatment:Treatment:

Treat the underlying causeTreat the underlying cause Improve alveolar gas exchangeImprove alveolar gas exchange Assisted ventilationAssisted ventilation

• Bicarbonate must not be infused to treat the acidosis because it generates more CO2

Respiratory AlkalosisHyperventilation, PaCO2

• Catastrophic CNS Events • Hemorrhage• Hysterical• Assisted ventilation• Drugs• Salicylates (early stages)• Interstitial Lung Disease• Cirrhosis, Liver Failure• Anxiety• Gram negative Septicemia• Hypoxia and severe anemia or high altitude

Hyperventilation, PaCO2

• Catastrophic CNS Events • Hemorrhage• Hysterical• Assisted ventilation• Drugs• Salicylates (early stages)• Interstitial Lung Disease• Cirrhosis, Liver Failure• Anxiety• Gram negative Septicemia• Hypoxia and severe anemia or high altitude

Respiratory AlkalosisSymptomsSymptoms

• Tingling and numbness• Parasthesias• Lethargy• Tetany• Unconsciousness• Vasospasm of cerebral vassals -

Hypercapnia

SymptomsSymptoms

• Tingling and numbness• Parasthesias• Lethargy• Tetany• Unconsciousness• Vasospasm of cerebral vassals -

Hypercapnia

Respiratory Alkalosis

TreatmentTreatment

• Treat underlying causeTreat underlying cause

TreatmentTreatment

• Treat underlying causeTreat underlying cause

Metabolic Acidosis

• Increased H+ Load

• Increased HCO3- Loss

Metabolic Acidosis

Anion Gap Metabolic AcidosisAccumulation of unmeasured anionsAccumulation of unmeasured anionsLow HCOLow HCO33 andand AGAG

ethanolethanol

remia remia

iabetic ketoacidosisiabetic ketoacidosis

araldehydearaldehyde

nfectionnfection

actic acidactic acid

thylene glycolthylene glycol

alicylatesalicylates

• MM• UU• DD•

PP• II• LL• EE• SS

Na+

Cl-

HCO3-

AG

Na+

Cl-

HCO3-

AG

• Salicylates

• Lactic acidosis

• Uremia

• Methanol intoxication

• Paint sniffing (toluene) / Paraldehyde

• Ethylene glycol intoxication

• DKA or alcoholic ketoacidosis

Non Anion Gap Metabolic AcidosisLoss of HCOLoss of HCO33 or External acid infusion or External acid infusion

Low HCOLow HCO33 AG AG << 12 12

• GI Losses of Bicarbonate (Diarrhoea)• Renal Losses

• Renal Tubular Acidosis• Renal Toxins• Carbonic Anhydrase Inhibitors• Ureteral Diversion• Compensation for Resp. Acidosis

• HCl or NH4Cl Infusion, TPN

Decrease in Anion Gap Metabolic AcidosisDefined as < 6

P araproteinemias, Multiple myeloma

L ithium intoxication

E xcessive Calcium and Magnesium

A lbumin is low (hypoalbuminemia)

B romism

Metabolic Acidosis

• Increased work of breathing : Deep rapid breathing (Kussmaul’s)

• Peripheral Vasodilatation, collapse, shock, impaired cardiac function

• Lethargy, drowsiness, confusion, stupor• Hyperkalemia• Nonspecific : Nausea, Vomiting• Chronic Acidosis:

Osteopenia – CaCo3 loss Muscle weakness – Glutamine loss

Clinical Features

Metabolic Acidosis

Principles:

• Identify cause• Initial goal : Bring the pH ~ 7.25

(For cardiac contractility & responsiveness to catecholamines)

Sodabicarb : 1-2 mEq/Kg [1 ml of 7.5% NaHCO3 = 0.9 mEq][Bicarb deficit (mEq/L) = Body wt.(Kg) X 0.3 X Base excess]

• Half as bolus• Half as infusion over 12 – 24 hrs.

Management

Metabolic Acidosis

• Potassium replacement :Serum K+ should be > 3.5 mEq/L before administering HCO3

-

• THAM (tromethamine; tris-hydroxymethyl aminomethane) An amino alcohol

Indication :In partients with CHF who may not be able to tolerate additional Na+ burden if treated with Sodabicarb.Dose : Body wt. (Kg) X Base excessAdministration: As infusion over 3 - 6 hours

Management – Contd.

Metabolic Acidosis

• DKA

• Lactic Acidosis

• RTA

• Uremia

• Salicylate toxicity

Specific Treatment

Metabolic Alkalosis

Very Dangerous:Very Dangerous:

• Shifts O2 dissociation curve to Lt.

• Causes vasoconstriction of all vessels except pulmonary circulation

• Suppresses ventilation

• Decreases ionized Ca++ and shifts K+ into cells – hypocalcemia and hypokalemia

Increase in extra-cellular pH (above 7.45) due to primary increase in plasma bicarbonate

Metabolic Alkalosis

Issues to Ponder over: • What generated the alkalosis?

• What is maintaining the alkalosis – what is preventing kidney from excreting the

alkali ?

Metabolic Alkalosis - Causes• Loss of acid: Loss of acid: GI LossesGI Losses• VomitingVomiting• NG suctionNG suction• Acid diarrhoea (Congenital Acid diarrhoea (Congenital

chloridorrhoeas, villous chloridorrhoeas, villous adenomas)adenomas)

Renal H+ LossRenal H+ Loss• DiureticsDiuretics (thiazides, (thiazides,

furosemide)furosemide)• Bartter’s SyndromeBartter’s Syndrome• Mg deficiencyMg deficiency• Hyperaldosteronism, Hyperaldosteronism,

Cushing’s Cushing’s

• Infusion of HCOInfusion of HCO33::

• IatrogenicIatrogenic• Milk Alkali syndromeMilk Alkali syndrome• Massive blood Massive blood

transfusion transfusion (citrated blood)(citrated blood)

• Rapid correction of Rapid correction of chronic hypercapniachronic hypercapnia

Metabolic Alkalosis

What’s maintainingWhat’s maintaining1. 1. Volume contraction (Chloride responsive)

NG Suction, vomiting, diuretics

2. Potassium deficiency

3. Chloride depletion

4. Increased mineralocorticoids

(Chloride resistant)

•Metabolic Alkalosis

What’s maintainingWhat’s maintaining

• Volume contraction (Chloride responsive)

• Adrenal Disorders

• Exogenous Steroids• Alkali Ingestion• Licorice• Bartter’s Syndrome


Clinical PresentationClinical Presentation

• Muscle cramps• Weakness• Hypoxia• Arrhythmias


Saline responsive intravascular volume expansion with normal

saline potassium repletion Ammonium chloride / Arginine chloride

in resistant casessistant alkalosisgastric losses)

Saline resistant potassium repletion mineralocorticoid antagonists acetazolamide Hemo or peritoneal dialysis : in severe

alkaloses with hyperosmolar states

Mixed Acid – Base Disorders

• Respiratory Acidosis + Metabolic Acidosis– Resp. Distress Syndrome

• Respiratory Acidosis + Metabolic Alkalosis– Excessive diuretic therapy, Chronic respiratory acidosis

with C.C.F.

• Metabolic Acidosis + Respiratory Acidosis– Hepatic Failure

• Respiratory Alkalosis + Metabolic Acidosis– Salicylate intoxication– Gm – ve sepsis

• Compensatory adjustments fall outside the expected reange

When to suspect a mixed acid base disorder:

1. The expected compensatory response does not occur

2. Compensatory response occurs, but level of compensation is inadequate or too extreme

3. Whenever the PCO2 and [HCO3-] becomes abnormal in the

opposite direction.

4. pH is normal but PCO2 or HCO3- is abnormal

5. In anion gap metabolic acidosis, if the change in bicarbonate level is not proportional to the change of the anion gap.

6. In simple acid base disorders, the compensatory response should never return the pH to normal. If that happens, suspect a mixed disorder.

• Vittal

Case 1 :

• Step 1: Alkalosis or Acidosis?

• Step 2: Primary Disturbance?

• Step 3: Acute or Chronic?

pH - 0.08 X (60-40)/10 = 0.16 7.4-0.16 = 7.24

Measured 370CpH 7.24pCO2 60.0 mmHg

pO2 56.0 mmHg

Calculated DataHCO3 actu 24 mmol/LBE +2O2 Sat 85%

Entered DataFiO2 70 %


pO2 56.0 mmHg

Calculated DataHCO3 actu 24 mmol/LBE +2O2 Sat 85%


5 mo. Old baby with bronchiolitis

Case 1:

• pH = 7.24 less than 7.35, so - acidosis • pCO2 = 60 mm Hg CO2 is > 45 mm Hg.- Resp. • HCO3

- = 24 mEq/L is normal. • BE = +2 is normal.

Conclusion: Acute Resp.Acidosis – UncompensatedAcute Resp.Acidosis – Uncompensated

Note: A pH of 7.24 could not be caused by a bicarbonate value that is WNL.

Analysis:

Case 2 :

• Step 1: Alkalosis or Acidosis?• Step 2: Primary Disturbance?• Step 4: What is the Anion Gap?Na-(Cl+HCO3)135-(115+8) = 12• Step 6: What is the expected CO2?(1.5 X HCO3) + (8+2) = 1.5X 8) + (8+2) = 18-22= 18-22


pO2 87.0 mmHg

S.Na+ 135 mEqS.Cl - 115 mEqCalculated DataHCO3

- actu 8 mmol/LBE -15O2 Sat 96%Entered DataFiO2 24 %


pO2 87.0 mmHg

S.Na+ 135 mEqS.Cl - 115 mEqCalculated DataHCO3

- actu 8 mmol/LBE -15O2 Sat 96%Entered DataFiO2 24 %

3 yr. Old baby with severe diarrhoea, diminished urine output, lethargy

Metabolic Acidosis withRespiratory Compensation

Case 3 :

• Step 1: Alkalosis or Acidosis?• Step 2: Primary Disturbance?• Step 4: What is the Anion Gap?Na-(Cl+HCO3)142-(108+10) = 24• Step 5: What is the corrected HCO3?(Corrected HCO3 = HCO3 + (AG - 12)10 + (24 - 12) = 22


pO2 60.0 mmHg

Calculated DataHCO3 actu 10 mmol/LBE -15O2 Sat 87%



pO2 60.0 mmHg

Calculated DataHCO3 actu 10 mmol/LBE -15O2 Sat 87%


8 mo.. Old baby resuscitated after a cardiac arrest; Na 142, Cl 108

Case 3 :

• Step 6: What is the expected pCO2?(Expected pCO2 = (1.5 X HCO3 + (8+2)

(1.5 X 10) + (8 + 2) = 21 – 25


pO2 60.0 mmHg

Calculated DataHCO3 act 10 mmol/LBE -15O2 Sat 87%



pO2 60.0 mmHg

Calculated DataHCO3 act 10 mmol/LBE -15O2 Sat 87%


8 mo.. Old baby resuscitated after a cardiac arrest; Na 142, Cl 108

Mixed Metabolic

&

Respiratory Acidosis

Case 4 :

• Step 1: Alkalosis or Acidosis?• Step 2: Primary Disturbance?• Step 3: Acute or Chronic?pH - 0.08 X (26-40)/10 = 0.12 7.4+0.12 = 7.52


pO2 112.0 mmHg

Calculated DataHCO3 actu 22 mmol/LBE +0.2O2 Sat 99 %



pO2 112.0 mmHg

Calculated DataHCO3 actu 22 mmol/LBE +0.2O2 Sat 99 %


4 yr. old girl with lethargy, irritability, jaundice

Acute Respiratory Alkalosis – Uncompensated

ExercisesExercises

Exercise 1:

pH = 7.2

PCO2 = 60 mm Hg

HCO3- = 24 mEq/L

SBE = 0 mEq/L

Analysis: Overall change is acid. Respiratory change is also acid - therefore contributing to the acidosis. Bicarb and SBE are normal - no metabolic compensation.

Conclusion:

Pure respiratory acidosis. Typical of acute respiratory depression.

Magnitude: MarkedMarked respiratory acidosis

Exercise 2:

pH = 7.31

pCO2 = 44 mm Hg

HCO3- = 20 mEq/L

Analysis: pH is less than 7.35, so the

condition is acidosis. pCO2 is normal. HCO3

- is less than 24 mEq/L.

Conclusion: This is an example of metabolic acidosis..

Note: This is the same pH as the first example, but it is due to too little bicarbonate

Exercise 3:

pH = 7.48

pCO2 = 33 mm Hg

HCO3- = 24 mEq/L

Analysis: pH is more than 7.45, so the condition is alkalosis. pCO2 is below 35 mm Hg. HCO3

- is normal.

Conclusion: This is an example of respiratory alkalosis.respiratory alkalosis.

Note: A pH of 7.48 could not be caused by a bicarbonate value that is WNL

Exercise 4:

pH = 7.48

pCO2 = 43 mm Hg

HCO3- = 33 mEq/L

Analysis: pH is more than 7.45, so the condition is alkalosis. pCO2 is normal. HCO3

- is above 28mEq/L.

Conclusion: This is an example of metabolic metabolic alkalosis.alkalosis.

Note: This is the same pH as the third example, but it is due to too much bicarbonate.

Exercise 5:

pH = 7.4

pCO2 = 60 mm Hg

HCO3- = 37 mEq/L

Analysis: Note that the carbon dioxide and bicarbonate values are both abnormal, but The pH is WNL.

In this case, the kidneys are retaining bicarbonate to counter the lungs’ retention of carbon dioxide, thus, keeping the 1 to 20 ratio and a pH that is WNL.

Conclusion: respiratory acidosisrespiratory acidosis with metabolic compensation

Exercise 6:

pH = 7.18

CO2 = 41 mm Hg

HCO3- = 14 mEq/L

BE = - 4

Analysis: The respiratory value is WNL, Bicarbonate is below normal. Base excess is actually a deficit (-4). There is a true deficit of bicarbonate. e.g. diabetic ketoacidosis. diabetic ketoacidosis.

Conclusion: Metabolic acidosisMetabolic acidosis where, where, as yet, there is no as yet, there is no compensation by the lungs.compensation by the lungs.

acid-base disorders

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