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CardioPulmonary Class > Test 4 Cardio > Flashcards

Test 4 Cardio Flashcards

1
Q

Describe how a weak acids behave in a solution such as blood?

A

Weak acids in solutions will act as an acid and donate a H+

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2
Q

Describe how a weak base behaves in solution such as blood?

A

Weak baes, like bicarbonate will reversibly bind H+ and accept H+

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3
Q

Compare the 3 mechanisms responsible for H+ regulation?

A
  1. Buffer systems (rapid, but incomplete)
  2. Ventilatory responses (less rapid)
  3. Renal responses (slow, but produces almonst near complete correct of pH)
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4
Q

ID 4 buffering systems the body uses in regulating acid-base balance

A
  1. Hemoglobin buffering system
  2. Protein buffering system
  3. Phosphate buffering system
  4. Bicarbonate buffering system
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5
Q

Describe the effect of O2 saturation on Hgb’s buffering capacity.

A
  • Buffering capacity will vary wtih oxygenation (reduced hemoglobin is a weak acid)
  • In the reduced form (carries less oxygen), more base is available to combine with H+ produced with the dissociation of carbonic acid in the tissues.
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6
Q

ID the most effective intracellular buffering system

A
  • Protein buffering system about 75% of all IC buffering occurs form IC proteins
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7
Q

Describe the role of bicarb as a buffering system in the blood

A
  • Bicarb accounts for over 50% of the total buffering capacity of the blood (EC)
  • It easiliy diffuses into the RBC’s so that 1/3 of all bicarb buffering occurs here
  • pKa is 6.1, so it’s a weak buffer.
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8
Q

Discuss rationale for why the bicarb system is the most important buffering system in the body

A

It can be regulated by both the kidneys and the lungs

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9
Q

Describe the role of ventilation in regulating H+ concentration

A
  • Via ventilation, the CO2 produced by the reaction of H+ and bicarb is easily removed from the body
  • Ability to maintain pH of 7.4 depends on:
    • Free movement of CO2 out of the body (requires ventilation and renal function)
  • Ventilatory responses occur within 1-5 minutes of a change in hydrogen ion concentration
  • Doubling alveolar ventilation eliminate sufficient CO2 to increase pH to 7.6
  • Decreasing alveolar ventilation to 1/4 of normal will decrease pH to 7.0
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10
Q

Describe renal regulation of H+ concentration

A
  • Renal responses that regulate ph = making urine more acid or alkaline
  • Via incomplete titration of H+ or bicarb, either enters the urine or gets excreted
  • In acidosis: H+ is excreted
  • In alkalosis: Bicarb is excreted
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11
Q

Describe how pH may be calculated by the HH equation using bicarb and CO2 concentrations in the blood

A
  • The H equation cites that pH is related to the ration of conjugate base to the undissociated acid
  • Equation is pH=6.1 + log of (Bicarb/(0.03xPaCO2))
  • Essentially, as long as Bicarb: CO2 remains 20:1, the pH will remain 7.4
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12
Q

Compare and contrast ventilator and renal response to acidosis in regard to efficacy and speed in ventilatory response

A

Ventilatory Response

  • Lungs excrete over 10K mEq of H2CO3 per day (kidneys are 50-500 mEq/day)
  • By altering alveolar ventilation and elimination of CO2, body compensates for pH change in a matter of minutes
  • Can buffer up to twice the amount of acid or base as all other buffers combined

Renal response:

  • Regulation occurs by allowing H+ or Bicarb to be removed from ECF (slow, but completely neutralizes)
  • Ordinarily, the kidneys can excrete up to 500 mEq of acid or alkaline each day (urine pH is 6.4)
  • High concentration of CO2 = excretion of.. while hyperventilation = retention of H+
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13
Q

List 5 anesthetic considerations with acidosis

A
  1. Potentiation of depressant effects of sedatives and anesthetic agents on CNS (increased non-ionized fraction and increased penetration into brain)
  2. Decreased sympathetic tone
  3. Increased arrhythmogenic of volatiles
  4. Increased K+ with succinylcholine
  5. Augmentation of NMBD
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14
Q

Categorize a provided arterial blood gas as either compensated/uncompensated and ither primary metabolic or respiratory

A
  • Look at the pH, and decipher from there.
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15
Q

ID the role of the medulla in regulating respiration

A

Medulla respiratory centers will

  1. Regulate the initiation of inspiration (dorsal)
  2. Regulate forced expiration (ventral)
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16
Q

ID the role of the pons in regulating respiration

A

Pons respiratory centers:

  • Apneustic center will prolong inspiration
  • Pneumotaxic center will regulate the respiratory rate
17
Q

Describe the effect on respiration of PCO2, O2, and pH on respiration

A

PaCO2

  • Increased PaCO2 will affect the alveolar ventilation within 1 minute
  • After several hours, the effect wanes due to the active transport of bicarb
  • Bicarb combines with H+ ions to return CSF to normal pH

PO2

  • Decreases PO2 increases sensitivity to PaCO2
  • Lowering the PO2 form 110 mmHg to 47 mmHg produces a higher ventilator response to PCO2
  • Lowering the PO2 to 37 mmHg increases both response and slope of response curve

pH

  • reduction in arterial pH stimulates ventilation
  • In pts with compensated metabolic acidosis, increased ventilation occurs in repsonse to low pH
  • Effect usually mediated by peripheral chemoreceptors with contribution from central receptors.
18
Q

Is the location of the central chemoreceptors and primary regulatory element

A
  • Is the region on the anterolateral surface of the medulla that is sensitive to chem changes (CO2)
  • CO2 readily crosses the BBB and forms carbonic acid, which dissociates into H+ ions; the CSF is poorly buffered, so pH changes rapidly
  • 75-80% of the ventilatory response to CO2 is due to central chemoreceptor activity
19
Q

Discuss the process which occurs in the medulla (central chemoreceptor) that occurs in the presence of chronic high PCO2

A

Process is called hypoxic drive, Raising the PaCO2 will increase the PaO2 response

20
Q

ID the two peripheral chemoreceptors and the primary regulatory elements

A
  1. Carotid bodies
  2. Aortic bodies
21
Q

Discuss the effects of PO2 on the carotid body chemoreceptor

A
  • They respond to changes in the PaO2, PaCO2, blood pressure, and pH
  • Respond mainly to low PaO2, but not high PaO2
  • Activation doesn’t occur until PaO2 is less than 50 mmHg
  • Not stimulated by O2 saturation abnormalities like CO poisoning
22
Q

ID the location and innervation of the pulmonary stretch receptors and how they are stimulated

A
  • Location: walls of bronchi and bronchioles
  • Activated when stretched, and tend to inhibit inspiration and causes shortening of exhalation when the lung is deflated
    • Herring-breur reflex is active when tidal volume is greater than 1.5L
  • Inhibitory signals are carried centrally by the vagus nerve and protects against over inflation
23
Q

ID the location and innervation of the irritant receptors and how they are stimulated

A
  • Located between the airway epithelial cells
  • Stimulated by: noxious gases (smoke, dust, cold air)
  • Travel up vagus – relfex effects include bronchoconstriction and hyperpnea
  • May play a role in bronchoconstriction during asthma attacks as a result of their response to released histamine
24
Q

ID the location and inervation of the J receptors and how they are stimulated

A
  • Location: Alvelolar walls close to the capillaries
  • Impulses pass up the vagus nerve and result in rapid shallow breathing
  • Engorgement of pulmonary capillaries and increased interstitial fluid volume of the alveolar wall activates these receptors
  • Might play a role in:
    • Rapid shallow breathing and dyspnea sensation assocaited wtih CHF and interstitial Dx
25
Q

Describe the effect of pH on respiration

A

pH will stimulate the respiration

26
Q

Describe the integrative effect of PCO2, PO2, and pH on respiration

A
  • A low pH will shift the reponse curves to the left
  • Exercise enhances the reponses to hypoxia (even if the PaCO2 is not raised) possibly due to lactic acidosis, afferents from the muscle, or catecholamine selection
27
Q

Describe the effects of different anesthetic agents on the PCO2 response curve

A
  • Decreases alveolar ventilation and increases PaCO2
28
Q

Describe the effects of different anesthetic agents on the PO2 response curve

A

All anesthetics will depress the ventilatory response to PaCO2 and PaO2

29
Q

Describe the effects of inhaled anesthetics on the control of ventilation

A
  • All volatiles will depress minute ventilation, which is comprised to a degree by increased RR
  • Inhalation anesthetics inhibit pulmonary irritatnt receptors and increase laryngeal receptors
30
Q

Compare the effects of inhalation anesthetics on the genioglossus, intercostals, and diaphragm

A

Anesthetics created a reduced control of genioglossus, intercostals, and diaphragm, creating an environment that is more difficult for a patient to naturally breate

  • Genioglossus doesnt hold tongue up as well
  • Intercostal muscles dont allow for better expansion
  • Diaphragm doesnt pull down as far and rest in a higher location

CardioPulmonary Class (6 decks)

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