Pulmonary Effects of Volatile Anesthetics

Question 1

All potent inhaled anesthetics: tidal volume

Answer 1

-decrease in a dose dependent manner

Question 2

All potent inhaled anesthetics: RR

Answer 2

less than adequate increase in RR

Question 3

All potent inhaled anesthetics: ETCO2

Answer 3

• increased resting

- enflurane>desflurane=isoflurane>sevoflurane=halothane>N2O

Question 4

All potent inhaled anesthetics: airway irritant

Answer 4

increase activity of laryngeal irritant receptors and decrease activity of pulmonary irritant receptors

Question 5

All potent inhaled anesthetics: FRC

Answer 5

• loss of intercostals
• altered respiratory pattern
• cephalad movement of diaphragm
• altered thoracic blood volume

Question 6

All potent inhaled anesthetics: smooth muscle in airway

Answer 6

• relax airway smooth muscle (bronchodilation) by directly depressing smooth muscle contractility
• direct effects on bronchial epithelium and airway smooth muscle cells
• indirect inhibition of reflex neural pathways

Question 7

All potent inhaled anesthetics: pulmonary vascular resistance

Answer 7

• lowest at the lung equivalent to FRC
• increase in PVR causes corresponding increase in pulmonary arterial pressure that promotes interstitial fluid transudation. PVR is increase by PEEP, alveolar hypoxia and hypercapnia, critical closing pressure
• inhaled agents reduce lung volume and indirectly effect PVR through that mechanism

Question 8

All potent inhaled anesthetics: hypoxic pulmonary vasoconstriction (HPV)

Answer 8

• regional alterations in PVR affect regional distribution of blood flow within the lung, produce changes in ventilation-perfusion matching, and simultaneously affect gas exchange
• HPV cause other vascular beds such as the cerebral, and coronary vessels to dilate in response to hypoxia

Question 9

Chemical control of respiration: central

Answer 9

• located near ventrolateral medulla and brainstem sites
• respond to changes in H ion concentration in the CSF
• NOT arterial CO2 tension or pH
• profoundly affected by respiratory than by metabolic alterations in arterial carbon dioxide tension

Question 10

Chemical control of respiration: peripheral

Answer 10

• located in the carotid bodies
• sensitive to changes in arterial CO2 tension, pH
• arterial oxygen tension

Question 11

Post-Op breathing effects: CO2 response curves

Answer 11

• all volatile anesthetics depress the ventilatory response to hypercapnia in a dose-depenedent fashion
• <0.2 MAC of volatile anesthetics may depress the peripheral chmoreflex loop and inhibit the ventilatory response to hypercapnia

Question 12

Post-Op breathing effects:hypexemia repsonse

Answer 12

-volatile anesthetics and N2O attenuate the ventilatory response to hypoxia in a dose-dependent manner at concentrations as low as 0.1 MAC

Question 13

Post-Op breathing effects: diffusion hypoxia may add to these complications

Answer 13

when using N2O