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BPT09 - lectures > ABGA > Flashcards

ABGA Flashcards

1
Q

H+: definition, values

A

D: concentration of free hydrogen ions, measure of how acidic & alkaline solution is

V: between 35-45 nmol/L
If <35 = alkalaemia
If >45 = acidemia

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2
Q

pH: defintion, values

A

D: Negative log of H+ concentration, common representation of H+ concentration because log nature of scale, small changes in pH actually represent large changes in H+ concentration

V: between 7,35 & 7,45
If < 7,35 = acidemia
If >7,45 = alkalaemia

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3
Q

PO2: defintion & values

A

D: Partial pressure of O2 thought of as drive for O2 molecules to move from one place to another. PO2 not measure of O2 content but determine extent to which haemoglobin saturated with O2. PaO2 refers specifically to partial pressure of O2 in arterial blood

V: >10,6kPa or >80mmHg in arterial blood on room air

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4
Q

PCO2: defintion & values

A

D: Partial pressure of CO2- thought of as drive for CO2 molecules to move from one place to another & proportional to amount of CO2 in blood. PaCO2 refers specifically to partial pressure of CO2 in arterial blood

V: 4,7-6,0kPa or 35-45mmHg in arterial blood

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5
Q

SO2: defintion & values

A

D: O2 saturation of haemoglobin: percentage of O2 binding sites on haemoglobin proteins occupied by O2 molecules. Measure of how much of blood O2 carrying capacity used. SaO2 refers specifically to O2 saturation of arterial blood

V: >96% on room air

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6
Q

HCO3 act: defintion & values

A

D: Actual bicarbonate: plasma bicarbonate concentration calculated from actual PCO2 & pH measurements in arterial blood sample. High bicarbonate levels signify metabolic alkalosis & low levels signify metabolic acidosis

V: 22-28 mmol/L

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7
Q

HCO3 st: defintion & values

A

D: Standard bicarbonate: plasma bicarbonate concentration calculated from PCO2 & pH measurements in arterial blood sample after PCO2 in sample corrected to 5,3kPa (40mmHg). Authors recommend using measurement of bicarbonate in ABG analysis

V: 22-28 mmol/L

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8
Q

BE: definition & values

A

D: Base excess: calculation of amount of base needed to be added to or removed from sample of blood to achieve neutral pH at 37°C, after PCO2 corrected to 5,3kPa. Positive BE indicates there is more base than normal (metabolic alkalosis) & negative BE indicates there is less base than normal (metabolic acidosis)

V: -2 to +2

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9
Q

Lactate: defintion & values

A

D: Indirect measure of lactic acid: high levels of lactic acid are sign of tissue hypoxia

V: 0,4 - 1,5 mmol/L

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10
Q

Hb: definition & values

A

D: Plasma haemoglobin concentration: effectively determines blood’s capacity to carry O2

V: 13-18g/dL for men, 11,5-16g/dL for women

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11
Q

Na: defintion & values

A

D: Plasma sodium concentration

V: 135-145 mmol/L

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12
Q

K: definition & values

A

D: Plasma protein concentration

V: 3,5-5 mmol/L

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13
Q

Clinical indications for ABGA: signs, indicatioms & monitoring

A

S: - Sudden unexplained dyspnea
- Cyanosis
- Abnormal breath sounds
- Severe, unexplained tachypnea - Heavy use of accessory muscles - Changes in ventilator settings
- Cardiopulmonary resuscitation
- New appearance or progression of cardiac arrhythmias - Acute Hypotension
- Acute deterioration in neurologic function

Indications:
- Need to evaluate ventilation (PaCO2) acid-base balance (pH & PaCO2), oxygenation status (PaO2 & SaO2) & oxygen carrying capacity of blood (PaO2, HbO2, total Hb & dyshemoblobins)
- Need to assess patient’s response to therapy or diagnostic tests (oxygen or exercise testing)
- Need to monitor severity & progression of documented disease process

Monitoring
Following should be monitored as part of arterial blood sampling:
- FiO2 or prescribed flow
- Patient’s respiratory rate
- Proper application of oxygen device
- Patient’s temperature
- Mode of ventilatory support & settings
- Appearance of puncture site (for haematoma) after application of pressure & before dressing

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14
Q

Characteristics pH values

A
  • Body’s pH → acid-base balance
  • pH scale: 0 (most acidic) – 14 (most basic/alkalic)
  • Maintaining Blood pH between 7.35 - 7.45 → human survival
  • Large deviations of pH → detrimental effects on metabolism & membrane permeability
  • Blood pH values < 7.0 and > 7.8: not compatible with life
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15
Q

ASSESSMENT ABGA

A
  • Collect arterial blood gas information
  • Often tested in ICU
    -Blood test: take sample from radial artery - Femoral (brachial artery less common)
  • Venous blood gases: less reliable O2 data
    -Lung/kidney failure
  • If pH imbalance additional tests to determine exact cause
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16
Q

Normal values of ABGA

A

Tableau

17
Q

Equation buffer system: characteristics

A

Bicarbonate/Carbon dioxide buffer system: CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+

Both buffer components (acid-base) modified largely independent of each other : - [CO2] (more acidic):
* RESPIRATION (=> exhalation)
* Quick method
* Slow breathing (↑ CO2 => ↓ pH) vs faster breathing (↓ CO2 => ↑ pH)

  • [HCO3-] (more alkaline):
  • KIDNEY (+ LIVER) (=> excretion)
  • Slower method
  • Excretion (↓ HCO3- => ↓ pH) vs reabsorption (↑ HCO3- => ↑ pH)
18
Q

pH disturbances p: 2 ≠ cases

A

Alkalosis: pH > 7,45
- When CO2 blood concentration is too low: Hyperventilation → hypocapnia → respiratory alkalosis
- When HCO3- blood concentration is too high:
Causes: Hypovolemia – Vomitting – diuretic use (°loss fluids) → metabolic alkalosis

Acidosis: pH < 7.35
- When CO2 blood concentration is too high: Hypoventilation → hypercapnia → respiratory acidosis
- When HCO3- blood concentration is too low:
Causes: diarrhea, toxic ingestions, kidney damage, liver failure → metabolic acidosis

19
Q

Interpretation of ABG

A

1) Alkalosis or acidosis: pH
- pH < 7,35 => more acidic = acidosis - pH > 7,45 => more base = alkalosis

2) Respiratory or metabolic: CO2 vs HCO3-
- If PaCO2 abnormal & HCO3- normal (22-26 mmol/L) => respiratory condition
- If PaCO2 normal (35-45 mmHg) & HCO3- abnormal => metabolic condition

3) Compensated or not or only partially
- If respiratory pb => metabolic compensate by increase or decrease HCO3- depending on whether there is acidosis / alkalosis If compensation not out of normal range => uncompensated
- If metabolic pb => respiratory compensate by decrease of increase PaCO2 depending on whether there is acidosis / alkalosis If compensation not out of normal range => uncompensated

BPT09 - lectures (13 decks)

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