ARTERIAL BLOOD GASDR.MADE WIDIA, SP.A(K)

Normal ABG ParametersArterial Mixed Venous

Normal Range Normal Range

pH 7,40 7,35-7,45 7,36 7,31-7,41

PaCO2 (mmHg) 40 35-45 46 41-51

PaO2 (mmHg) 100 80-100 40 35-42

SaO2 (%) 97 95-100 75 68-77

HCO3 - (mEq/L) 24 22-26 24 22-26

BE (mEq/L) 0 ±2 0 ±2Note.21% O2 at sea level

Oxygenation

• Normal variationsDue to age, FiO2,or barometric pressure

Age: PaO2≈110-1/2 patient’s age

• Abnormal variationsHyperoxemia = above normal valuesHypoxemia = below normal values

Mild Hypoxemia Moderate Hypoxemia Severe HypoxemiaPaO2 (mmHg) 60-79 40-59 <40

SaO2 (%) 91-94 86-90 <85

Notes: PaO265 mmHg - Begin O2 therapy60 mmHg – O2 stimulus to breathe55 mmHg – Begin O2 therapy (CO2 retainers)30 mmHg – Loss of conciousness20 mmHg – Brain damage likely

Signs and Symptoms of Acute Hypoxemia(relative order of appearance)

Tachypnea Arrhytmias Loss of coordination

Dyspnea Blurred or tunnel vision Lethargy/weakness

Pallor Impair judgement Tremors/hyperactive reflexes

Tachycardia Confusion Stupor

Hypertension Euphoria Coma≈30 mmHg

Headache Bradycardia Death

Anxiety Hypotension

Cyanosis Nausea/vomitting

Signs and Symptoms of Acute Hypercarbia(relative order of appearance)

Tachypnea Hypotension

Dyspnea Drowsiness

Tachycardia Hallucination

Hypertension Convulsion

Vasodilatation (diaphoresis, flushing) Coma ≈70 mmHg

Headache Death

Bradypnea

Signs and Symptoms of Chronic Hypoxemia(relative order of appearance)

Arrhytmias Papilledema

↓CO Polycythemia

Clubbing Impaired judgment

Dyspnea Myoclonic jerking

Irritability Pulmonary hypertension

Tiredness

Types Physiological cause ExamplesAtmospheric Insufficient O2 available :

↓FiO2 → ↓PaO2

↓PIO2 high altitude, drowning, O2 therapy error

Tidal Hypoventilation(↑PaCO2→ ↓PaO2)

Pulmonary obstruction, pulmonary restriction, CNS depression, N-M disorders

Alveolar Wasted ventilation, regional hypoventilation :(↑PaCO2→ ↓PaO2)

shunt : (PvO2 + PaO2→↓PaO2)

V/Q abnormality : (PvO2 + PaO2→↓PaO2)

Diffusion defect :(PaO2→block→↓PaO2)

Pulmonary emboli

Shock, pneumonia/atelectasis

COPD, high O2 therapy

Fibrosis/sarcoidosis, A-C block, pulmonary edema, O2 therapy

Hypoxemia/Hypoxia-Cause and Effects

Types Physiological cause ExamplesHemoglobic Q abnormality : ↓CaO2, PaO2

normal, ↓SaO2 Anemia, hemmorrhage, sickle cell, CO poisoning

Stagnan Q abnormality : ↓O2 transport (↓PvO2→↓PaO2)

Cardiovascular failure, arrhythmias, shock, hemmorrhage

Histotoxic Cyanide poisoning

Demand ↑metabolic demand causing one or more hypoxias

Execise, fever, burns, hyperthyroidism

Step 1:Check pH

Step 2:Check PaCO2

(N=35-45)

Step 3: Check HCO3

-

(N=22-26)

Interpretation

↑ (>7,45; Alkalosis)

↑ ↑ PC Metabolic Alkalosis

N ↑ Metabolic Alkalosis

↓ N Respiratory Alkalosis

↓ ↓ PC Respiratory Alkalosis

Normal(7,35-7,45)

↑ ↑ FC Metabolic Alkalosis (7,41-7,45)FC Respiratory Acidosis (7,35-7,39)

N N Normal

↓ ↓ FC Metabolic Acidosis (7,35-7,39)FC Respiratory Alkalosis (7,41-7,45)

↓ (<7,35;Acidosis)

↑ ↑ PC Respiratory Acidosis

↑ N Respiratory Acidosis

N ↓ Metabolic Acidosis

↓ ↓ PC Metabolic Acidosis

INTERPRETING ABG’s

FC = Fully Compensated; PC = Partially Compensated

Respiratory Disorder pH and PaCO2 go in opposite direction

Metabolic Disorder pH and HCO3- go in same direction

Compensating* PaCO2 and HCO3- go in same direction

Mixed Disorder* PaCO2 and HCO3- go in opposite direction

Type of Disorders

*Expected compensation must be done to determine whether or not a disorder is pure or mixed

pH/PaCO2/HCO3- Relationship – Expected Effects and Compensation

Respiratory Disorders

PaCO2 pH HCO3-

Acute ↑ 10 mmHg → ↓ 0,05 ↑ 1 mEq/L

↓ 10 mmHg → ↑ 0,10 ↓ 2 mEq/L

Chronic ↑ 10 mmHg → ↓ 0,03 ↑ 4 mEq/L

↓ 10 mmHg → ↑ 0,03 ↓ 5 mEq/L

Metabolic Disorders

Acidosis PaCO2 = last two digits of pHPaCO2 = (1,5 x HCO3

-) + 8 ± 2

Alkalosis PaCO2 change is variable, rarely above 55 mmHg

pH PaCO2 HCO3- K+ Cl-

Respiratory Acidosis (Ventilatory Failure)

Uncompensated (acute) ↓ ↑ N N N

Partially compensated ↓ ↑ ↑ N N

Fully compensated (chronic) N ↑ ↑ N↑ ↓

Respiratory Alkalosis (Alveolar hyperventilation)

Uncompensated (acute) ↑ ↓ N N N

Partially compensated ↑ ↓ ↓ N N

Fully compensated (chronic) N ↓ ↓ ↓ ↑

Metabolic Acidosis

Uncompensated (acute) ↓ N ↓ ↑ ↑

Partially compensated ↓ ↓ ↓ ↑ ↑

Fully compensated (chronic) N ↓ ↓ N N

Metabolic Alkalosis

Uncompensated (acute) ↑ N ↑ ↓ ↓

Partially compensated ↑ ↑ ↑ ↓ ↓

Fully compensated (chronic) N ↑ ↑ N N

Overview of Acid – Base Disorders and Parameter Changes

Respiratory Alkalosis (Alveolar Hyperventilation)CNS disorderCVA (infarct)Drugs : Ammonium chloride; epinephrine, progesterone, respiratory stimulants, salicylate poisoning (early)Infections (G-)Lesion (meningitis, encephalitis)Metabolic acidosis (CSF)Psychogenic :Anxiety, neurosis, painTrauma

MetabolicBacteremiaExerciseFeverHepatic failure (coma)HyperthyroidismMetabolic acidosis

PulmonaryAsthma (early)Atelectasis (early)COPD (early)Pneumonia (early)Pulmonary burnsPulmonary edemaPulmonary embolismRestrictive disorders (mild or early)

↓Diaphragm movementAbdominal distensionObesityPregnancy

CardiovascularAnemiaCarbon monoxid poisonCHFMIPulmonary embolismShock

OtherAltitude (high)Hypoxemia (most common cause)Mechanical ventilation

Metabolic AcidosisAnion gap↑Cardiac arrestDiarrhea (severe,↑loss of HCO3-)↑Cl-

↑K+

Liver failure

↑AcidsKetones (DKA or starvation)Lactic (shock, hypoxia)Renal failure (↓secretion of acids)

Ingestion :CO poison, cyanide, ethylene glycol (antifreeze), exogenous acids (NH4Cl,diamox), INH overdose, methanol (sterno), paraldehyde, phenformin, salicylate poison (late stage)

Metabolic AlkalosisNatural :Inadequate dietIngestion of baseVomiting (upper GI)

Iatrogenic : HCO3

- during arrest, NG Sx (↓Cl-), ↓K+, ↑Na+, massive blood replacement, IV therapy (↑SO4 +/or PO4), diuretic therapy (↑excretion of H+, K+, Cl-), steroid therapy, aldosteronism (Cushing’s)

Cardiopulmonary System ↓myocardial contractility↑ or ↓ myocardial irritabilityPulmonary vascular constrictionSystemic vasodilation

ArrhythmiasHeart failureFlushed skin color/diaphoresisPulmonary hypertension

Central Nervous System Depressed cortical functionDilated cerebral vessels↑ or ↓ respiratory center activity

Disoriented, somnolence, coma

Focus neurological signs, NM irritability

Headache, ↑ CSF pressureHyperventilation (if

metabolic)Hypoventilation (if

respiratory)

Renal and Metabolic ↑serum Cl- and K+ (early)↑excretion of Cl- and K+ (later)Reabsorption of HCO3

-

Hyper/hypochloremiaHyperkalemia↑ urine K+

Nausea, vomiting

Physiological Effects and Clinical Manifestations of Acidosis

Cardiopulmonary System Bronchoconstriction↑ myocardial irritabilityPulmonary vascular dilationSystemic vasoconstriction

ArrhythmiasDyspnea↓ PVR↑HR, palpitationsPale skin color

Central Nervous System Constricted cerebral vessels (↓cerebral edema)

↑ excitability dan NM irritability

↑ or ↓ respiratory center activity

Anxiety, nervousness, light-headedness, tingling / numbness, ↑reflexes, seizures, tetany

↓CSF pressureHyperventilation (if

respiratory)Hypoventilation (limited, if

metabolic)

Renal and Metabolic ↓ serum Cl- and K+ (early)↓ excretion of Cl- and K+ (later)Excretion of HCO3

-

Hyper/hypochloremiaHypokalemia↓urine K+

Physiological Effects and Clinical Manifestations of Alkalosis

Equation Comments Significance

Acid-Base

Anion Gap1.AG = (Na+ + K+ )-(Cl- + HCO3

- )2.AG = Na+ - (Cl- + HCO3

- )3.AG = Na+ - (Cl- + CO2 content)

Normal = 20 mEq/LNormal = 12 mEq/LNormal = 14 mEq/LAlkalosis causes and ↑ anion gapAcidosis cause a ↓ anion gap

Evaluate the electrolyte balance between cations and anions in the extracellular fluid

Indicates if there is a metabolic acidosis

↑AG = ↑ unmeasured anions: lactate (hypoxia or hyperventilation), poisons (alcohol,salicylates).

↓unmeasuredd cations : K+, Ca++ ,Mg++ ↓AG =↓ unmeasured anions:albumin↑ unmeasured cations : K+, Ca++ ,Mg++

Base Excess (BE)1.BE = ∆PaCO2 +∆pH x 100 22.BE ≈ ∆PaCO2 3.BE ≈ ∆HCO3

- + 10∆pH

Base deficit (BD) = -BE∆PaCO2 from 40∆pH from 7,40Accurately only in range of : PaCO2 30-50, pH 7,30-7,50∆HCO3

- from 24

Use for compensated metabolic conditionsUse for compensated metabolic conditions

Bicarbonat Correction of pHHCO3

- = (0,2)body weight x BDCorrect to pH 7,40BD = Base Deficit

Used to correct for metabolic acidosis

Equation

Equation Comments Significance

Henderson-Hasselbach1.pH = 6,1 + log (HCO3

- /H2CO3 )2.pH = 6,1 + log (HCO3

- /dissolved CO2 )3.pH = 6,1 + total CO2 – 0,03 PaCO2 0,03 PaCO2 4.PaCO2 = total CO2 0,3 x (1-antilog (pH-6,1))

Total CO2 = volume% 2,2

Calculation of pH or PaCO2

Rule of 8’sAt : pH HCO3

- = 7,6 8/8 (PaCO2 ) 7,5 6/8 (PaCO2 ) 7,4 5/8 (PaCO2 ) 7,3 4/8 (PaCO2 ) 7,2 3/8 (PaCO2 )

Examples : whenpH 7,4, PaCO2 40, HCO3

- = 5/8 (40) = 25pH 7,3, PaCO2 60, HCO3

- = 4/8 (60) = 30

Estimate of HCO3- in relation to pH

and PaCO2

Siggaard-Anderson Nomogram See Appendix Used to determine BE, total CO2 , actual HCO3

- and standard HCO3-

T40 BicarbonateT40 = HCO3

- - expected ∆HCO3-

HCO3- = standard plasma

Expected ∆HCO3- = PaCO2 -40

15

Used to find a “true” metabolic component in acute hypercapnia