acid-base disorders adapted from haber, r.j.: “a practical approach to acid- base disorders.”...

Acid-Base Acid-Base DisordersDisorders

Adapted from Haber, R.J.: “A practical Approach to Acid-Base Adapted from Haber, R.J.: “A practical Approach to Acid-Base Disorders.” Disorders.” West J. Med West J. Med 1991 Aug; 155:156-1511991 Aug; 155:156-151

Allison B. Ludwig, M.D.Allison B. Ludwig, M.D.

Site Director, Jacobi Medicine Site Director, Jacobi Medicine ClerkshipClerkship

Goals:Goals:

Learn to work through acid-base Learn to work through acid-base disorders without nomograms or disorders without nomograms or complicated mathematical formulascomplicated mathematical formulas

Be able to recognize and work through Be able to recognize and work through multiple offsetting disorders that are multiple offsetting disorders that are coincident in the same patientcoincident in the same patient

Outline:Outline:

Data Base, Terms and DefinitionsData Base, Terms and Definitions Simple-Acid Base DisordersSimple-Acid Base Disorders Mixed Acid-Base DisordersMixed Acid-Base Disorders

Data BaseData Base

Arterial pHArterial pH Arterial pCO2Arterial pCO2 Serum HCO3 (best from blood chemistry)Serum HCO3 (best from blood chemistry)

Terms and DefinitionsTerms and Definitions

VariableVariable Primary Primary DisorderDisorder

Normal Range, Normal Range, arterial Gasarterial Gas

Primary Primary DisorderDisorder

pHpH AcidemiaAcidemia 7.35 - 7.457.35 - 7.45 AlkalemiaAlkalemia

pCO2pCO2 Respiratory Respiratory alkalosisalkalosis

35 - 4535 - 45 Respiratory Respiratory acidosisacidosis

HCO3HCO3 Metabolic Metabolic acidosisacidosis

22 – 2622 – 26 Metabolic Metabolic AlkalosisAlkalosis

Respiratory compensation for metabolic disorders is rapidRespiratory compensation for metabolic disorders is rapid Full metabolic compensation for respiratory disturbances Full metabolic compensation for respiratory disturbances

requires renal adjustment and takes 3-5 days requires renal adjustment and takes 3-5 days

Outline:Outline:

Data Base, Terms and DefinitionsData Base, Terms and Definitions

Simple-Acid Base DisordersSimple-Acid Base Disorders Mixed Acid-Base DisordersMixed Acid-Base Disorders

Simple Acid-Base Simple Acid-Base DisordersDisorders

Look at the pH in order to determine the Look at the pH in order to determine the primary abnormalityprimary abnormality

Pathophysiologic principle: body does not Pathophysiologic principle: body does not fully compensate even for chronic acid-base fully compensate even for chronic acid-base disordersdisorders

Example #1Example #1


Normal Normal Range, Range, arterial Gasarterial Gas


pHpH AcidemiaAcidemia 7.35-7.457.35-7.45 AlkalemiaAlkalemia





pHpH 7.507.50

pCO2pCO2 2929

HCO3HCO3 2222

Acute Respiratory Alkalosis

Causes of Acute Causes of Acute Respiratory AlkalosisRespiratory Alkalosis

AnxietyAnxiety HypoxiaHypoxia Lung disease with or without hypoxiaLung disease with or without hypoxia CNS diseaseCNS disease Drug use—salicylates, catecholamines, Drug use—salicylates, catecholamines,

progesteroneprogesterone PregnancyPregnancy SepsisSepsis Hepatic EncephalopathyHepatic Encephalopathy Mechanical VentilationMechanical Ventilation










pHpH 7.257.25

pCO2pCO2 6060

HCO3HCO3 2626

Acute Respiratory Acidosis

Causes of Acute Causes of Acute Respiratory AcidosisRespiratory Acidosis

CNS depression—drugs, CNS eventCNS depression—drugs, CNS event Neuromuscular disorders—myopathies, Neuromuscular disorders—myopathies,

neuropathiesneuropathies Acute airway obstruction—upper airway, Acute airway obstruction—upper airway,

laryngospasm, bronchospasmlaryngospasm, bronchospasm Severe pneumonia or pulmonary edemaSevere pneumonia or pulmonary edema Impaired lung motion—hemothorax, Impaired lung motion—hemothorax,

pneumothoraxpneumothorax Thoracic cage injury—flail chestThoracic cage injury—flail chest Ventilator dysfunctionVentilator dysfunction










pHpH 7.347.34

pCO2pCO2 6060

HCO3HCO3 3131

Chronic Respiratory Acidosis with Metabolic Compensation

Causes of Chronic Causes of Chronic Respiratory AcidosisRespiratory Acidosis

Chronic lung disease—obstructive or Chronic lung disease—obstructive or restrictiverestrictive

Chronic neuromuscular disordersChronic neuromuscular disorders Chronic respiratory center depression—Chronic respiratory center depression—

central hypoventilationcentral hypoventilation


VariablVariablee









pHpH 7.507.50

pCO2pCO2 4848

HCO3HCO3 3636

Metabolic Alkalosis

Causes of Metabolic Causes of Metabolic AlkalosisAlkalosis

VomitingVomiting DiureticsDiuretics Excess mineralocorticoid activity—Cushing’s Excess mineralocorticoid activity—Cushing’s

syndrome, Conn’s syndrome, exogenous syndrome, Conn’s syndrome, exogenous steroids, licorice ingestion, increased renin steroids, licorice ingestion, increased renin states, Bartter’s syndromestates, Bartter’s syndrome

Excess alkali administrationExcess alkali administration Refeeding alkalosisRefeeding alkalosis


VariablVariablee


Normal Range, Normal Range, arterial Gasarterial Gas







pHpH 7.207.20

pCO2pCO2 2121

HCO3HCO3 88

Metabolic Acidosis with Respiratory Compensation

Causes of Metabolic Causes of Metabolic AcidosisAcidosis

Non-GapNon-Gap GI HCO3 loss: diarrhea, ureteral diversionsGI HCO3 loss: diarrhea, ureteral diversions Renal HCO3 loss: RTA, aldosterone inhibitors, Renal HCO3 loss: RTA, aldosterone inhibitors,

carbonic anhydrase inhibitorscarbonic anhydrase inhibitors Iatrogenic: normal saline Iatrogenic: normal saline

Anion GapAnion Gap Ketoacidosis: diabetic, alcoholicKetoacidosis: diabetic, alcoholic Renal failureRenal failure Lactic AcidosisLactic Acidosis RhabdomyolysisRhabdomyolysis Toxins: methanol, ethylene glycol, paraldehyde, Toxins: methanol, ethylene glycol, paraldehyde,

salicylatessalicylates

Outline:Outline:

Data Base, Terms and DefinitionsData Base, Terms and Definitions Simple-Acid Base DisordersSimple-Acid Base Disorders

Mixed Acid-Base DisordersMixed Acid-Base Disorders

The RulesThe Rules Look at the pH: whichever side of 7.40 the pH is on, the Look at the pH: whichever side of 7.40 the pH is on, the

process that caused it to shift to that side is the primary process that caused it to shift to that side is the primary abnormalityabnormality Principle: the body doesn’t fully compensate for primary acid-base Principle: the body doesn’t fully compensate for primary acid-base

disordersdisorders Calculate the anion gap: Na – (Cl + HCO3): if the anion Calculate the anion gap: Na – (Cl + HCO3): if the anion

gap is >20, there is a primary metabolic acidosis regardless gap is >20, there is a primary metabolic acidosis regardless of pH or HCO3of pH or HCO3 Principle: the body doesn’t generate a large anion gap to Principle: the body doesn’t generate a large anion gap to

compensate for a primary disordercompensate for a primary disorder Calculate the excess anion gap (total anion gap minus the Calculate the excess anion gap (total anion gap minus the

normal anion gap) and add this to the measured HCO3 normal anion gap) and add this to the measured HCO3 concentration, if >30, there is underlying metabolic concentration, if >30, there is underlying metabolic alkalosis; if <24, there is underlying non-gap metabolic alkalosis; if <24, there is underlying non-gap metabolic acidosisacidosis Principle: 1 mmol of unmeasured acid titrates 1 mmol of Principle: 1 mmol of unmeasured acid titrates 1 mmol of

bicarbonatebicarbonate

Understanding the anion Understanding the anion gapgap

Each millimolar decrease in HCO3 is accompanied by Each millimolar decrease in HCO3 is accompanied by a millimolar increase in the anion gap, the sum of the a millimolar increase in the anion gap, the sum of the new (excess) anion gap and the remaining (measured) new (excess) anion gap and the remaining (measured) HCO3 value should be equal to a normal bicarbonate HCO3 value should be equal to a normal bicarbonate concentrationconcentration










Respiratory Alkalosis and Anion Gap Metabolic Acidosis

1.1. Look at the pH to determine the Look at the pH to determine the primary process. primary process.

2.2. Calculate the anion gap: Na – (Cl + Calculate the anion gap: Na – (Cl + HCO3) HCO3)

3.3. Calculate the excess anion gap (total Calculate the excess anion gap (total anion gap minus the normal anion anion gap minus the normal anion gap) and add this to the measured gap) and add this to the measured HCO3 concentration, if >30, there is HCO3 concentration, if >30, there is underlying metabolic alkalosis; if underlying metabolic alkalosis; if <24, there is underlying non-gap <24, there is underlying non-gap metabolic acidosismetabolic acidosis

pHpH 7.507.50

pCO2pCO2 2020

HCO3HCO3 1515

NaNa 140140

ClCl 103103

What’s the Diagnosis?What’s the Diagnosis?

Salicylate OverdoseSalicylate Overdose





pHpH AcidemiaAcidemia 7.35-7.35-7.457.45

AlkalemiaAlkalemia





Anion Gap Metabolic Acidosis and Metabolic Alkalosis

pHpH 7.407.40

pCO2pCO2 4040

HCO3HCO3 2424

NaNa 145145

ClCl 1001001.1. Look at the pH to determine the Look at the pH to determine the

primary process. primary process. 2.2. Calculate the anion gap: Na – (Cl + Calculate the anion gap: Na – (Cl +

HCO3) HCO3) 3.3. Calculate the excess anion gap (total Calculate the excess anion gap (total

anion gap minus the normal anion anion gap minus the normal anion gap) and add this to the measured gap) and add this to the measured HCO3 concentration, if >30, there is HCO3 concentration, if >30, there is underlying metabolic alkalosis; if underlying metabolic alkalosis; if <24, there is underlying non-gap <24, there is underlying non-gap metabolic acidosismetabolic acidosis


Chronic renal failure in a Chronic renal failure in a patient with vomiting as patient with vomiting as

his uremia worsened.his uremia worsened.










Respiratory alkalosis, Anion Gap Metabolic Acidosis and Metabolic Alkalosis

pHpH 7.507.50

pCO2pCO2 2020

HCO3HCO3 1515

NaNa 145145

ClCl 1001001.1. Look at the pH to determine the Look at the pH to determine the

primary process. primary process. 2.2. Calculate the anion gap: Na – (Cl + Calculate the anion gap: Na – (Cl +

HCO3) HCO3) 3.3. Calculate the excess anion gap (total Calculate the excess anion gap (total

anion gap minus the normal anion anion gap minus the normal anion gap) and add this to the measured gap) and add this to the measured HCO3 concentration, if >30, there is HCO3 concentration, if >30, there is underlying metabolic alkalosis; if underlying metabolic alkalosis; if <24, there is underlying non-gap <24, there is underlying non-gap metabolic acidosismetabolic acidosis


History of vomiting History of vomiting (metabolic alkalosis), (metabolic alkalosis), alcoholic ketoacidosis alcoholic ketoacidosis

(metabolic acidosis), and (metabolic acidosis), and bacterial pneumonia bacterial pneumonia

(respiratory alkalosis)(respiratory alkalosis)










Respiratory Acidosis, Anion gap Metabolic Acidosis, Metabolic Alkalosis




pHpH 7.107.10

pCO2pCO2 5050

HCO3HCO3 1515

NaNa 145145

ClCl 100100


Patient presented in an obtunded state Patient presented in an obtunded state (respiratory acidosis), history of vomiting (respiratory acidosis), history of vomiting

(metabolic alkalosis), DKA (anion gap (metabolic alkalosis), DKA (anion gap metabolic acidosis)metabolic acidosis)

OrOr

Chronic respiratory acidosis and metabolic Chronic respiratory acidosis and metabolic compensation in whom an acute anion gap compensation in whom an acute anion gap

metabolic acidosis developedmetabolic acidosis developed










Anion Gap and Non-Anion Gap Metabolic Acidoses




pHpH 7.157.15

pCO2pCO2 1515

HCO3HCO3 55

NaNa 140140

ClCl 110110


DKA with non-gap DKA with non-gap acidosis during recovery acidosis during recovery

phase of DKA due to phase of DKA due to failure to regenerate failure to regenerate

HCO3 from keto-acids HCO3 from keto-acids lost in the urinelost in the urine

ConclusionsConclusions

Acid-base disturbances are easy to analyze if Acid-base disturbances are easy to analyze if approached systematicallyapproached systematically

Determine primary abnormalities based on pHDetermine primary abnormalities based on pH Calculate the anion gapCalculate the anion gap Calculate the delta gap and add to the Calculate the delta gap and add to the

measured HCO3 measured HCO3 Calculate an anion gap on EVERY chemistry Calculate an anion gap on EVERY chemistry

you seeyou see If there is an elevated anion gap, remember to If there is an elevated anion gap, remember to

get an ABG!!get an ABG!!

acid-base disorders adapted from haber, r.j.: “a practical approach to acid- base disorders.”...

Documents

metabolic disorders

acid base disorders

metabolic compensation

metabolic alkalosis

respiratory disturbances

chronic acidbase disorders

simple acidbase disorders

days slide