interpreting abgs (or the abcs of abgs) suneel kumar md

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Interpreting ABGs Interpreting ABGs (or the ABCs of ABGs) (or the ABCs of ABGs) Suneel Kumar MD Suneel Kumar MD

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Page 1: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Interpreting ABGsInterpreting ABGs(or the ABCs of ABGs)(or the ABCs of ABGs)

Interpreting ABGsInterpreting ABGs(or the ABCs of ABGs)(or the ABCs of ABGs)

Suneel Kumar MDSuneel Kumar MD

Page 2: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Arterial Blood Gases• Written in following manner:

pH/PaCO2/PaO2/HCO3

– pH = arterial blood pH

– PaCO2 = arterial pressure of CO2

– PaO2 = arterial pressure of O2

– HCO3 = serum bicarbonate concentration

Page 3: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Oxygenation• Hypoxia: reduced oxygen

pressure in the alveolus (i.e. PAO2)

• Hypoxemia: reduced oxygen pressure in arterial blood (i.e. PaO2)

Page 4: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Hypoxia with Low PaO2

• Alveolar diffusion impairment

• Decreased alveolar PO2

– Decreased FiO2

– Hypoventilation– High altitude

• R L shunt• V/Q mismatch

Page 5: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Hypoxia with Normal PaO2

• Alterations in hemoglobin– Anemic hypoxia– Carbon monoxide poisoning– Methemoglobinemia

• Histotoxic hypoxia– Cyanide

• Hypoperfusion hypoxia or stagnant hypoxia

Page 6: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Alveolar—Arterial Gradient

• Indirect measurement of V/Q abnormalities

• Normal A-a gradient is 10 mmHg• Rises with age• Rises by 5-7 mmHg for every 0.10

rise in FiO2, from loss of hypoxic vasoconstriction in the lungs

Page 7: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Alveolar—Arterial Gradient

A-a gradient = PAO2 – PaO2

• PAO2 = alveolar PO2 (calculated)

• PaO2 = arterial PO2 (measured)

Page 8: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Alveolar—Arterial Gradient

PAO2 = PIO2 – (PaCO2/RQ)

• PAO2 = alveolar PO2

• PIO2 = PO2 in inspired gas

• PaCO2 = arterial PCO2

• RQ = respiratory quotient

Page 9: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Alveolar—Arterial Gradient

PIO2 = FiO2 (PB – PH2O)• PB = barometric pressure (760 mmHg)• PH2O = partial pressure of water vapor

(47 mmHg)

RQ = VCO2/VO2

• RQ defines the exchange of O2 and CO2 across the alveolar-capillary interface (0.8)

Page 10: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Alveolar—Arterial Gradient

PAO2 = FiO2 (PB – PH2O) – (PaCO2/RQ)

Or

PAO2 = FiO2 (713) – (PaCO2/0.8)

Page 11: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Alveolar—Arterial Gradient

• For room air:PAO2 = 150 – (PaCO2/0.8)

• And assume a normal PaCO2 (40):

PAO2 = 100

Page 12: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Acid-Base

• Acidosis or alkalosis: any disorder that causes an alteration in pH

• Acidemia or alkalemia: alteration in blood pH; may be result of one or more disorders.

Page 13: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Six Simple Steps1. Is there acidemia or alkalemia?2. Is the primary disturbance respiratory

or metabolic?3. Is the respiratory problem acute or

chronic?4. For metabolic, what is the anion gap?5. Are there any other processes in

anion gap acidosis?6. Is the respiratory compensation

adequate?

Page 14: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Henderson-Hasselbach Equation

pH = pK + log [HCO3/PaCO2] x K(K = dissociation constant of CO2)

Or

[H+] = 24 x PaCO2/HCO3

Page 15: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Henderson-Hasselbach Equation

pH7.207.307.407.507.60

[H+]6050403020

Page 16: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 1:Acidemia or Alkalemia?

• Normal arterial pH is 7.40 ± 0.02– pH < 7.38 acidemia– pH > 7.42 alkalemia

Page 17: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 2:Primary Disturbance

• Anything that alters HCO3 is a metabolic process

• Anything that alters PaCO2 is a respiratory process

Page 18: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 2:Primary Disturbance

• If pH, there is either PaCO2 or HCO3

• If pH, there is either PaCO2 or HCO3

Page 19: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 3:Respiratory

Acute/Chronic?• Acute:

CO2 by 10 pH by 0.08

• Chronic:CO2 by 10 pH by 0.03

• Changes in CO2 and pH are in opposite directions

Page 20: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 4:For Metabolic, Anion Gap?

Anion gap = Na+ - (Cl- + HCO3-)

– Normal is < 12

Page 21: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Increased Anion Gap• Ingestion of drugs or toxins

– Ethanol– Methanol– Ethylene glycol– Paraldehyde– Toluene– Ammonium chloride– Salicylates

Page 22: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Increased Anion Gap• Ketoacidosis

– DKA– Alcoholic– Starvation

• Lactic acidosis• Renal failure

Page 23: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 4:For Metabolic, Anion

Gap?

• If + AG, calculate Osm gap:

Calc Osm = (2 x Na+) + (glucose/18) + (BUN/2.8) + (EtOH/4.6)

Osm gap = measured Osm – calc Osm

Normal < 10 mOsm/kg

Page 24: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Nongap Metabolic Acidosis

• Administration of acid or acid-producing substances– Hyperalimentation– Nonbicarbonate-containing IVF

Page 25: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Nongap Metabolic Acidosis

• GI loss of HCO3

– Diarrhea– Pancreatic fistulas

• Renal loss of HCO3

– Distal (type I) RTA– Distal (type IV) RTA– Proximal (type II) RTA

Page 26: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Nongap Metabolic Acidosis

• Calculate urine anion gap:Urine AG = (Na+ + K+) – Cl-

– Positive gap indicates renal impaired NH4

+ excretion

– Negative gap indicates normal NH4+

excretion and nonrenal cause

Page 27: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Nongap Metabolic Acidosis

• Urine Cl- < 10 mEq/l is chloride responsive and accompanied by “contraction alkalosis” and is “saline responsive”

• Urine Cl- > 20 mEq/l is chloride resistant, and treatment is aimed at underlying disorder

Page 28: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 5: Any other process with elevated

AG?• Calculate gap, or “gap-gap”:

Gap = Measured AG – Normal AG (12)

Page 29: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 5: Any other process with elevated

AG?• Add gap to measured HCO3

– If normal (22-26), no other metabolic problems

– If < 22, then concomitant metabolic acidosis

– If > 26, then concomitant metabolic alkalosis

Page 30: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 6: Adequate respiratory

compensation?Winter’s Formula

Expected PaCO2 = (1.5 x HCO3) + 8 ± 2

– If measured PaCO2 is higher, then concomitant respiratory acidosis

– If measured PaCO2 is lower, then concomitant respiratory alkalosis

Page 31: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Step 6: Adequate respiratory

compensation?• In metabolic alkalosis, Winter’s

formula does not predict the respiratory response– PaCO2 will rise > 40 mmHg, but not

exceed 50-55 mmHg– For respiratory compensation, pH will

remain > 7.42

Page 32: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Clues to a Mixed Disorder

• Normal pH with abnormal PaCO2 or HCO3

• PaCO2 and HCO3 move in opposite directions

• pH changes in opposite direction for a known primary disorder

Page 33: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 1• A 24 year old student on the 6

year undergraduate plan is brought to the ER cyanotic and profoundly weak. His roommate has just returned from a semester in Africa. The patient had been observed admiring his roommate's authentic African blowgun and had scraped his finger on the tip of one of the poison darts (curare).

Page 34: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 1

138 10026

7.08/80/37

Page 35: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 1• What is the A-a gradient?

A-a gradient = [150 – 80/0.8] - 37A-a gradient = 13

• Acidemia or alkalemia?• Primary respiratory or metabolic?• Acute or chronic?

PCO2 by 40 would pH by 0.32

Page 36: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 1• What is the anion gap?

AG = 138 – (100 + 26)AG = 12

Page 37: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 1

• Acute respiratory acidosis

Page 38: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 2• A 42 year old diabetic female who

has been on insulin since the age of 13 presents with a 4 day history of dysuria which has progressed to severe right flank pain. She has a temperature of 38.8ºC, a WBC of 14,000, and is disoriented.

Page 39: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 2

135 99

124.8

7.23/25/113

Page 40: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 2• What is the A-a gradient?

A-a = [150 – 25/0.8] – 113 = 6• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 135 – (99 + 12) = 24

Page 41: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 2• What is the gap?

Gap = 24 – 12 = 12Gap + HCO3 = 12 + 12 = 24

– No other metabolic abnormalities

• Is the respiratory compensation appropriate?Expected PCO2 = (1.5 x 12) + 8 ± 2 =

24 ± 2– It is appropriate

Page 42: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 2

• Acute anion gap metabolic acidosis (DKA)

Page 43: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3• A 71 year old male, retired

machinist, is admitted to the ICU with a history of increasing dyspnea, cough, and sputum production. He has a 120 pack-year smoking history, and quit 5 years previously. On exam he is moving minimal air despite using his accessory muscles of respiration. He has acral cyanosis.

Page 44: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3

135 93

30

7.21/75/41

Page 45: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3• What is the A-a gradient?

A-a = [150 – 75/.8] – 41 = 15• Acidemic or alkalemic?• Primary respiratory or metabolic?• Acute or chronic?

– Acute PCO2 by 35 would pH by 0.28

– Chronic PCO2 by 35 would pH by 0.105• Somewhere in between

Page 46: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3• What is the anion gap?

AG = 135 – (93 + 30) = 12

Page 47: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3

• Acute on chronic respiratory acidosis (COPD)

Page 48: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3b• This same patient is intubated and

mechanically ventilated. During the intubation he vomits and aspirates. He is ventilated with an FiO2 of 50%, tidal volumes of 850 mL, PEEP of 5, rate of 10. One hour later his ABG is 7.48/37/215.

Page 49: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 3b• Why is he alkalotic with a normal

PCO2?– Chronic compensatory metabolic

alkalosis and acute respiratory alkalosis

Page 50: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 4• A 23 year old female presents to

the Emergency Room complaining of chest tightness and light-headedness. Other symptoms include tingling and numbness in her fingertips and around her mouth. Her medications include Xanax and birth control pills, but she recently ran out of both.

Page 51: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 4

135 10922

7.54/22/115

Page 52: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 4• What is the A-a gradient?

A-a = [150 – 22/.8] – 115 = 8• Acidemia or alkalemia?• Primary respiratory or metabolic?• Acute or chronic?

– Acute CO2 by 18 would pH by 0.144

• What is the anion gap?AG = 135 – (109 + 22) = 4

Page 53: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 4

• Acute respiratory alkalosis (panic attack)

Page 54: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 5• 72 year old woman admitted from

a nursing home with one week history of diarrhea and fever.

133 1185

7.11/16/94

Page 55: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 5• What is the A-a gradient?

A-a = [150 – 16/.8] – 94 = 36• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 133 – (118 + 5) = 10• Is respiratory compensation

adequate?PCO2 = (1.5 x 5) + 8 ± 2 = 16 ± 2

Page 56: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 5

• Non anion gap metabolic acidosis (diarrhea)

• Compensatory respiratory alkalosis

Page 57: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 6

• A 27 year old pregnant alcoholic with IDDM is admitted one week after stopping insulin and beginning a drinking binge. She has experienced severe nausea and vomiting for several days.

Page 58: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 6

136 70

19

7.58/21/104

Page 59: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 6• What is the A-a gradient?

A-a = [150 – 21/.8] – 104 = 20• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 136 – (70 + 19) = 47• What is the gap?

Gap = 47-12 = 35

Gap + HCO3 = 54

Page 60: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 6

• Primary respiratory alkalosis (pregnancy)

• Anion gap metabolic acidosos (ketoacidosis)

• Nongap metabolic alkalosis (vomiting)

Page 61: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 7• 35 year old male presents to the

ER unconscious.

145 70

23

7.61/24/78

Creat 6.1

Page 62: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 7• What is the A-a gradient?

A-a = [150 – 24/.8] – 78 = 42• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 145 – (70 + 23) = 52

Page 63: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 7

• What is the gap?

Gap = 52 - 12 = 40

Gap + HCO3 = 63–Nongap metabolic alkalosis

Page 64: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case 7

• Respiratory alkalosis• Anion gap metabolic acidosis

(renal failure)• Nongap metabolic alkalosis

Page 65: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #1

• 51 year old man with polysubstance abuse, presented to ER with 3-4 day h/o N/V and diffuse abdominal pain. Reports no EtOH or cocaine in 2 weeks. He has been taking “a lot” of aspirin for pain. Denies dyspnea, but has been tachypneic since arrival.

Page 66: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #1

• Afebrile, P 89, R 20, BP 142/57. Lethargic but arrousable, easily aggitated. Lungs clear, and abdomen is soft with mild tenderness in LUQ and LLQ.

Page 67: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #1126

3.4

93

11

58

1.8218

UA 1+ ketones

Acetone negative

Lactate 6.9

EtOH 0

Osm 272

7.46/15/107

Page 68: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #1• What is the A-a gradient?

A-a = [150 – 15/.8] – 107 = 25• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 126 – (93 + 11) = 22Anion gap metabolic acidosis

Page 69: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #1• What is the gap?

Gap = 22 - 12 = 10

Gap + HCO3 = 21Nongap metabolic acidosis

• What is the osmolar gap?Calc Osm = 2x126 + 218/18 +

58/2.8Calc Osm = 265

Osm gap = 272 – 265 = 7

Page 70: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #1

• Respiratory alkalosis (aspirin)• Anion gap metabolic acidosis

(aspirin)• Nongap metabolic acidosis

Page 71: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case # 2

• 20 year old college student brought to the ER by his fraternity brothers because they cannot wake him up. He had been in excellent health until the prior night.

Page 72: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #2

• Afebrile, P 118, R 32, BP 120/70. Anicteric sclerae, pupils 8mm and poorly responsive to light. Fundoscopic exam with slight blurring of discs bilaterally and increased retinal sheen. Remainder of exam unremarkable.

Page 73: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #2142

4.3

98

10

14 108

UA negative

EtOH 45

Osm 348 7.22/24/108

Page 74: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #2• What is the A-a gradient?

A-a = [150 – 24/.8] – 108 = 12• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 142 – (98 + 10) = 34Anion gap metabolic acidosis

Page 75: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #2• What is the gap?

Gap = 34 - 12 = 22

Gap + HCO3 = 32

Nongap metabolic alkalosis

Page 76: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #2• What is the osmolar gap?

Calc Osm = 2x142 + 108/18 + 14/2.8 + 45/4.6

Calc Osm = 305Osm gap = 348 - 305 = 43

• Is the respiratory compensation adequate?

PCO2 = (1.5 x 10) + 8 ± 2 = 23 ± 2

Page 77: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #2

• Anion gap metabolic acidosis with elevated osmolar gap (methanol)

• Nongap metabolic alkalosis• Compensatory respiratory

alkalosis

Page 78: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #3

• A 23 year old man presents with confusion. He has had diabetes since age 12, and has been suffering from an intestinal flu for the last 24 hours. He has not been eating much, has vague stomach pain, stopped taking his insulin, and has been vomiting. His glucose is high.

Page 79: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #3

130 80

10

7.20/25/68

Page 80: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #3

• What is the A-a gradient?A-a = [150 – 25/.8] – 68 = 51

• Acidemia or alkalemia?• Primary respiratory or metabolic?• What is the anion gap?

AG = 130 – (80 + 10) = 40Anion gap metabolic acidosis

Page 81: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #3

• What is the gap?

Gap = 40 - 12 = 28

Gap + HCO3 = 38

Nongap metabolic alkalosis

• Is the respiratory compensation adequate?

PCO2 = (1.5 x 10) + 8 ± 2 = 23 ± 2

Page 82: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Bonus Case #3

• Anion gap metabolic acidosis (DKA)

• Metabolic metabolic alkalosis (emesis)

• Compensatory respiratory alkalosis

Page 83: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD
Page 84: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Pulmonary Artery CathetersSuneel Kumar MD

Page 85: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

History

• In 1929, German surgical trainee Werner Forssman experimented on human cadavers

• Found that it was easy to guide a urologic catheter from arm veins into the right atrium

Page 86: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

History

• Forssmann went as far as to dissect the veins of his own forearm and guided a urologic catheter into his right atrium

• Used fluoroscopic control and a mirror

• Was able to walk to get a chest x-ray

• For his trouble, he was fired

• Eventually was awarded the Nobel Prize in 1956

Page 87: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

History

• Jeremy Swan and William Ganz from Cedars-Sinai developed a balloon-guided catheter placement

• Published in NEJM in August 1970• Idea came to Swan while watching sail

boats moving quickly on a calm day• Neither the physicians nor the

manufacturer were able to patent the balloon catheter

Page 88: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Functional Cardiac Anatomy

Page 89: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Uses of PA and Arterial Catheters• Allows assessment of both RV and LV

during diastolic and systolic phases

• Allows use of PCWP which is used to reflect the degree of pulmonary congestion

• Allows in assessment of blood flow (CO) and tissue oxygenation (SvO2)

Page 90: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Use of PA Catheter

• To establish diagnosis

• To guide therapy

• To monitor response to therapy

• To assess determinants of tissue oxygenation

Page 91: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Indications • Diagnosis of shock• Differentiate high vs

low pressure pulmonary edema

• Diagnosis of PPH • Assessment of

response to medications for PPH

• Diagnosis of valvular heart disease, intracardiac shunts, cardiac tamponade, and PE

• Monitoring and management of complicated AMI

• Assessing hemodynamic response to therapies

• Management of MOF and/or severe burns

• Management of hemodynamic instability after cardiac surgery

• Aspiration of air emboli

Page 92: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Indications

Page 93: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Contraindications

• Tricuspid or pulmonic valve mechanical protheses

• Right heart mass (thrombus or tumor)

• Tricuspid or pulmonic valve endocarditis

Page 94: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Approaches to Access

Page 95: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Approaches to Access

Page 96: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Approaches to Access

Page 97: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Approaches to Access

Page 98: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Insertion Technique

Page 99: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Proper Position

Page 100: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Coiled PA Catheter

Page 101: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Distal Cath Tip

Page 102: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Lung Zones of West

Page 103: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Lung Zones of West

PA > Pa > Pc

Pa > PA > Pc

Pa > Pc > PA

Page 104: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Static Column of Blood to LA

Page 105: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

During Diastole:

• Tricuspid and mitral valves are open

• Blood leaves the atria and fill the ventricles

• Pressure between the atria and ventricles equalize

Page 106: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

At End-Diastole:

• Mean RA pressure equalizes with the RV end-diastolic pressure

• PA diastolic and PCWP equalize with the LV end-diastolic pressure

Page 107: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Mean RA = RV EDP

Page 108: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

PA EDP and PCWP = LV EDP

Page 109: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

CVP/RA Waveform

• Three positive waves:– a wave (usually

largest)– c wave (may not be

seen)– v wave

Page 110: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

CVP/RA Waveform

• a wave is with atrial contraction• c wave is with closure of tricuspid valve• v wave is with blood filling atrium with tricuspid valve

is closed

Page 111: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

CVP/RA Waveform

Page 112: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

CVP/RA Waveform and EKG

• a wave in PR interval• c wave at end of QRS,

in RST junction• v wave after T wave

Page 113: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Measuring Mean CVP

• Final filling of the ventricle occurs during atrial contraction (a wave)

• Therefore, average the a wave on the CVP/RA waveform

Page 114: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Measuring the Mean CVP

Page 115: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

RV Waveform

• Sharp upstroke during systole, and downstroke during diastole

Page 116: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

RV Waveform

Page 117: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

RV Waveform

Page 118: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

RV to PA

• As the catheter goes past the pulmonic valve:– The systolic pressure is about the same

and now has a dicrotic notch (from closure of pulmonic valve)

– The diastolic pressure increases

Page 119: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

RV to PA

Page 120: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

PA Waveform

• PA systole within T wave• PA diastole at end of QRS

Page 121: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

PCWP Waveform

• Inflation of the balloon stops forward blood flow

• Creates a static column of blood between the catheter tip and the LA

Page 122: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

PCWP Waveform

• Has a waveform characteristic of the RA, primarily with a waves and v waves

• Mean PCWP is close to PA diastolic pressure

Page 123: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

PCWP Waveform and EKG

• a wave near end or after QRS

• v wave well after T wave

Page 124: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Mean PCWP Measurement

• Final filling of the left ventricle occurs during atrial contraction

• Therefore, measure the average of the a wave

• Measure at the end of expiration

Page 125: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Mean PCWP Measurement

12 + 6 / 2 = 9

Page 126: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

PCWP at End Expiration

Page 127: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Waveform Review

Page 128: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD
Page 129: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD
Page 130: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Calculating Cardiac Output

• Cardiac output done by thermodilution

• Known saline bolus (5-10 mL) at known temperature (usually < 25oC) injected via the proximal lumen

• Thermistor at end of SC catheter measures the change in temperature

• Change in temperature is inversely proportional to the CO

Page 131: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Calculating Cardiac Output

Page 132: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Calculating Cardiac Output

• Stewart-Hamilton formula:

CO = (vol of injectate) x (blood temp – injectate temp) x (computation constant) / (change in blood temp as a function of time, or AUC)

Page 133: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Types of Shock

CO PCWP SVR

Cardiogenic

Hypovolemic /

Septic / Distributive N/

Page 134: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Cardiogenic Shock

• Severely decreased cardiac output

• Extracardiac obstructive shock (e.g. cardiac tamponade) has equalization of pressures

• RAP = RV diastolic = PA diastolic = PCWP

• RA with minimal x and y descents, and elevation in mean RAP

• Loss of PA respiratory variations

Page 135: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Constrictive Pericarditis

• Limited early diastolic filling

• Causes a plateau in the RV pressure

• “Square root sign”

• RAP has a “M” or “W” configuration

• a and v waves accentuated with rapid x and y descents

• Due to rheumatic disease, TB, metastatic carcinoma, prior chest XRT, or open heart surgery

Page 136: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Constrictive Pericarditis

Page 137: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Hypovolemic Shock

• Due to decreased blood volume

• Usually from hemorrhage or volume depletion

Page 138: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Distributive / Septic Shock

• Due to peripheral vasodilation

• Other causes include anaplylaxis, neurogenic shock, Addisonian crisis, toxic shock syndrome, cirrhosis, and myxedema coma

Page 139: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Information from PA Catheter

• Directly:– CVP– PA pressure– PCWP– CO

– SvO2

• Calculated:– Stoke volume/

index– Cardiac index– Systemic vascular

resistance (SVR)– Pulmonary vascular

resistance (PVR)– Oxygen delivery

Page 140: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Formulas

• SVR = (MAP – CVP) / CO

• PVR = (MPAP – PCWP) / CO

• SV = CO / HR

• CaO2 = (1.39 x Hb x SaO2) + (0.003 x PaO2)

• DO2 = CaO2 x CO

Page 141: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Normal Values

• SvO2• Stoke volume• Stroke index• Cardiac output• Cardiac index• MAP• CVP• PCWP• PA pressures• SVR• PVR

60-75%

50-100 mL/beat

25-45 mL/beat/m2

4-8 L/min

2.5-4.0 L/min/m2

70-110 mmHg

2-6 mmHg

8-12 mmHg

15-30 / 0-10 mmHg

900-1400 dynes.sec/cm5

40-150 dynes.sec/cm5

Page 142: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 1

• A 65 year old man with COPD required intubation for respiratory failure. He was placed on AC.

• Shortly after intubation, he developed hypotension and a SG catheter was placed, but a PCWP could not be obtained.

Page 143: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 1

• RA 4, sat 76%

• RV 45/0, sat 76%

• PA 45/20, mean 28, sat 77%

• PCWP ???

• BP 90/60, mean 70

• CO 5.7

• SVR 928

• 7.44 / 34 / 110, sat 99%

• Mixed venous 7.38 / 42 / 44, sat 77%

Page 144: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 2

• A 58 year old male is admitted to the CCU as a r/o MI.

• Developed respiratory distress.

Page 145: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 2

• RA 6, sat 65%

• RV 55/0, sat 66%

• PA 55/30, mean 45, sat 66%

• PCWP ???, sat 91%

• BP 110/80, mean 90

• CO 5.0

• SVR 1,344

• 7.44 / 35 / 80, sat 91%

• Mixed venous 7.40 / 40 / 36, sat 66%

Page 146: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 2

Page 147: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 3

• A 55 year old female is admitted with chest pain and shock.

• The EKG shows acute ischemic changes in the inferior limb leads.

• What is the diagnosis, and how would you treat her?

Page 148: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 3

• RA 14, sat 55%• RV 30/15, mean 20, sat 55%• PA 30/11, mean 20, sat 55%• PCWP • BP 90/60, mean 70• CO 2.5• SVR 1,792• 7.38 / 35 / 85, sat 90%• Mixed venous 7.34 / 41 / 32, sat 55%

Page 149: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 4

• A 50 year old male presents with syncope and shock.

• Room air ABG is obtained.

Page 150: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 4

• RA 15, sat 48%• RV 45/0, sat 48%• PA 45/20, mean 28, sat 49%• PCWP 7• BP 50/50, mean 60• CO 2.5• SVR 1,440• 7.32 / 32 / 59, sat 89%• Mixed venous 7.28 / 38 / 28, sat 49%

Page 151: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 5

• A 65 year old male with a two day history of weakness, dizziness, and dyspnea on exertion.

• On physical, noted to have a resting tachycardia.

• Chest x-ray shows a mediastinal mass.

Page 152: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 5

• RA 20, sat 71%• RV 45/19, sat 71%• PA 45/20, mean 28, sat 72%• PCWP 20, sat 96%• BP 90/70, mean 77• CO 4.0• SVR 1,140• 7.39 / 38 / 85, sat 96%• Mixed venous 7.38 / 40 / 40, sat 72%

Page 153: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 6

• A 112 year old male presents with tachypnea, confusion, and hypotension.

Page 154: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 6

• RA 2, sat 69%

• RV 42/0, sat 69%

• PA 45/15, mean 25, sat 70%

• PCWP 8, sat 85%

• BP 70/40, mean 50

• CO 6.5

• SVR 592

• 7.55 / 32 / 50, sat 85%

• Mixed venous 7.40 / 38 / 37, sat 70%

Page 155: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 7

• A 45 year old alcoholic with abdominal pain and hypotension.

• Chest x-ray shows a large, globular heart and a left pleural effusion.

• The Hct 45%.

Page 156: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 7

• RA 1, sat 49%

• RV 20/0, sat 49%

• PA 20/10, mean 13, sat 49%

• PCWP 4

• BP 80/50, mean 60

• CO 3.0

• SVR 1,576

• 7.34 / 30 / 80

• Mixed venous 7.31 / 38 / 28, sat 49%

Page 157: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 8

• 24 hours later, the prior patient in Case #7 becomes tachypneic.

• What complication has occurred?

Page 158: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 8

• RA 4, sat 64%• RV 45/0, sat 64%• PA 45/25, mean 32, sat 65%• PCWP 12• BP 110/70, mean 85• CO 6.1• SVR 1,064• 7.46 / 32 / 55, sat 89%• Mixed venous 7.40 / 31 / 35, sat 65%

Page 159: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 9

• A 98 year old male with confusion and hypotension.

• What kind of shock does he have?

Page 160: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 9

• RA 12, sat 47%• RV 40/12, sat 48%• PA 40/30, mean 33, sat 49%• PCWP 29, sat 90%• BP 80/50, mean 60• CO 2.5• SVR 1,536• 7.30 / 45 / 60, sat 90%• Mixed venous 7.26 / 50 / 28, sat 49%

Page 161: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 10

• 35 year old female with an abnormal chest x-ray and dyspnea on exertion.

• What is the diagnosis?

Page 162: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 10

• RA 8, sat 84%

• RV 60/0, sat 85%

• PA 45/20, mean 28, sat 86%

• PCWP 10, sat 99%

• BP 120/80, mean 95

• CO 9.4

• SVR 744

• 7.40 / 40 / 99, sat 99%

• Mixed venous 7.38 / 42 / 54, sat 86%

Page 163: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 11

• A 38 year old female presents with chest pain and dyspnea.

Page 164: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 11

• RA 8, sat 65%

• RV 110/10, sat 66%

• PA 90/50, mean 63, sat 67%

• PCWP 12, sat 98%

• BP 110/70, mean 83

• CO 3.2

• SVR 1,872

• 7.41 / 30 / 90, sat 98%

• Mixed venous 7.37 / 33 / 37, sat 67%

Page 165: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 12

• 18 year old female presents with exertional syncope.

Page 166: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD

Case # 12

• RA 15, sat 78%

• RV 110/27, sat 90%

• PA 80/40, mean 60, sat 91%

• PCWP 28

• BP 120/80, mean 95, sat 99%

• CO 20

• SVR 800

• 7.40 / 40 / 99, sat 99%

• Mixed venous 7.38 / 42 / 79, sat 91%

Page 168: Interpreting ABGs (or the ABCs of ABGs) Suneel Kumar MD