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Anesthesia 2 > Blood Gas Analysis > Flashcards

Blood Gas Analysis Flashcards

1
Q

Effects of pH

A

Changes effect enzyme function and excitability of nerve and muscle cells
-Acidosis
-Alkolosis

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2
Q

Acidosis signs

A

-alteration in cardiac contractions
-decreased vascular response to catecholamines
-can lead to loss of consciousness

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3
Q

Alkolosis signs

A

-impaired neurological function
-impaired muscular function
-tingling sensations, nervousness, muscle twitches

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4
Q

Metabolic acidosis/alkalosis

A

caused by an imbalance in production and excretion of acids and bases by KIDNEYS

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5
Q

Causes of acidosis/ too much acid build up (metabolic)

A

-shock
-DKA
-renal failure
-diarrhea
-diuretics
-lactic acidosis
-ethylene glycol poisoning

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6
Q

Clinical signs of acidosis (metabolic)

A

-headache
-lethargy
-nausea
-anorexia
vomiting
-diarrhea
-coma
-death

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7
Q

Causes of metabolic alkalosis/ excess loss of acid in blood

A

-excessive vomiting
-GI obstruction

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8
Q

Clinical signs of metabolic alkalosis

A

-dizziness
-lethargy
-weakness
-muscle twitching
-cramps
-tetany
-coma
-death

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9
Q

Respiratory acidosis/alkalosis

A

-caused by LUNGS or breathing abnormalities

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10
Q

Cause of respiratory acidosis

A

HYPOVENTILATION
-obstruction of gas exchange
-respiratory depression

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11
Q

Clinical signs of respiratory acidosis

A

-dyspnea
-resp distress
-shallow respirations
-tachycardia
-dysrhythmias
-headache
-restlessness
-confusion

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12
Q

Respiratory alkalosis cause

A

HYPERVENTILATION
-pain
-fear
-anxiety
-fever

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13
Q

Clinical signs of alkalosis

A

-dyspnea
-nausea
-vomiting
-headaches
-restlessness
-lethargy
-coma

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14
Q

Chemical buffers

A

-bicarbonate, phosphate, sodium

-potassium/hydrogen ion exchange

-bones

-proteins (albumin, hemoglobin, plasma globulins)

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15
Q

Respiratory buffer

A

-CO2

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16
Q

Renal buffer

A

Bicarbonate

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17
Q

Chemical buffering timing

A

Immediate response to changes in acid/base balance

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18
Q

Chemical buffering for acidosis

A

H+ moves into the cell while K moves out of the cell
*Results in Hyperkalemia

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19
Q

Chemical buffering for alkalosis

A

H+ moves out of the cell while K+ moves into the cell
*Results in hypokalemia

20
Q

Respiratory buffering

A
  1. A normal byproduct of cell metabolism is CO2
    -CO2 travels in blood and excess CO2 combines with H2O= H2CO3
  2. Blood pH changes according to levels of carbonic acid (H2CO3)
21
Q

Respiratory buffering timing

A

Responds in seconds to minutes

22
Q

Chemoreceptors

A

-detect changes of CO2, pH and O2 in the blood
-stimulate respiratory rate

23
Q

Central chemoreceptors

A

Located on the ventral surface of the medulla and respond to changes in the pH of CSF

24
Q

Peripheral chemoreceptors

A

Located in the carotid and aortic arches

25
Q

Renal Buffering

A

Maintains blood pH. Kidneys retain or excrete bicarbonate to compensate
-hours to days! (Chronic process)

  1. pH decreases, kidneys retain bicarbonate
  2. pH increases, kidneys excrete HCO3-
26
Q

Blood Gases

A

-O2
-CO2
*the sum of all partial pressures=atmospheric pressure

Others
-N2
-H2O
-Argon
-other trace gases

27
Q

Normal Atmospheric pressure

A

760 mmHg

-O2: 160mmHg
-CO2: Negligible in atmosphere but we breath out 38-45 mmHg

28
Q

Gas transport

A

Oxygen: bound to hemoglobin. Inhale 21%, exhale 15%

CO2: transported as bicarbonate ion, byproduct of metabolism with H
Exhale 5-6%; negligible inhaled from atmosphere

29
Q

FiO2

A

Fraction of inhaled gas that is O2
-need to interpret arterial blood sample

30
Q

Partial pressure O2

A

Amount of O2 dissolved in plasma
-lung function affects this because determines what amount of O2 passes through alveoli
-driving force to get O2 onto hemoglobin molecule

31
Q

Saturation of Hb with O2 (sO2)

A

How well saturated hemoglobin are
-measured by pulse oximeter
-saturation related to partial pressure

Exercise: graph shifts right

32
Q

Oxygen content (O2Ct)

A

Total number of mls O2 per L of blood

33
Q

Normal lung function: FIO2 and PaO2

A

FIO2 x5= PaO2

34
Q

arterial blood PaO2 is not equal to atmospheric pO2

A

Atmospheric: 160mmHg
PaO2: 80-100mmHg

Due to:
-some alveoli are not well ventilated (DEAD SPACE)
-some blood moves through the lung without picking up oxygen (SHUNT)

35
Q

O2 delivery

A

O2 delivery= O2 content x CO

*O2 content= O2 in Hb + dissolved O2

*CO= HR x SV

36
Q

Factors affecting O2 delivery

A

-PaO2
-HB concentration
-CO
-Diffusion from capillaries to mitochondria
-Oxygen affinity of Hb
-local blood flow

37
Q

5 causes of hypoxemia

A
  • decreases FIO2
    -hypoventilation
    -shunt
    -V/Q mismatch
    -diffusion impairment
38
Q

Hypoxic drive

A

Takes over if PaO2 is less than 60mmHg
-may result in hypocapnia
-built in safety mechanism

39
Q

Sampling

A
  1. Take sample, and run through blood gas analyser (expensive wet units or less expensive dry units)
  2. Lung function assessment
    -take arterial blood gas sample because it has left lungs but not passed through tissues
  3. Assess body pH
    -can take a mixed venous sample from pulmonary artery (or can use jugular vein because 30% CO goes to head and neck)
40
Q

Sampling errors

A
  1. Taking sample from wrong site
  2. Air bubble
    -results give values in ait
  3. blood clots
  4. Arterial and venous mixed samples
  5. Run samples immediately or put on ice (not longer than 2 hrs)
41
Q

What do blood gas analyser electrodes measure?

A

-pH- through bicarbonate
-partial pressure O2 (recalculated with patient temperature)
-partial pressure CO2 (recalculated with patient temperature)
-electrolytes (glucose, lactate, anion gap)

**Do not measure nitrogen or nitrous oxide

42
Q

What does co-oximeter measure?

A

-hemoglobin content
-saturation of hemoglobin molecule with O2

43
Q

Print off

A

-You put in arterial sample, inspired O2 (FIO2), operator ID, patient ID, temperature

-analyzer gives the rest

44
Q

Evaluating blood gas printoff

A
  1. Look at pH
  2. Does pCO2 explain change in pH? If not what does?
  3. Define metabolic or respiratory acidosis (alkalosis not common)
  4. Look at p)2, sO2, O2Ct
  5. Hypoxemic? concentration of O2 that patient is breathing? Is there enough Hb? How is oxygen delivery to tissues maintained?
45
Q

How to determine hypoxemia or anemia?

A

Hypoxemia
-pulmonary dysfunction,but good CO
-low PaO2
-low O2 saturation
-oxygen content is low

Anemia, but good CO
-normal O2 saturation
-normal PaO2
-oxygen content is low

Anesthesia 2 (17 decks)

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