Podcast
Questions and Answers
What does an AST/ALT ratio greater than 1 indicate?
What does an AST/ALT ratio greater than 1 indicate?
- Normal liver function
- Wilson & Alcoholic liver disease (correct)
- Hepatic injury
- Cholestatic disease
What does a bilirubin level increase in urine typically indicate?
What does a bilirubin level increase in urine typically indicate?
- Increased conjugated bilirubin (correct)
- Increased unconjugated bilirubin
- Hemolytic anemia
- Normal liver function
Which of the following accurately describes the role of albumin in liver function evaluation?
Which of the following accurately describes the role of albumin in liver function evaluation?
- Reflects acute changes in synthetic function
- Long half-life limits its usefulness in acute situations (correct)
- Elevated levels indicate liver regrowth
- Short half-life makes it a reliable early indicator
What is true regarding AFP levels greater than 1000 ng/mL?
What is true regarding AFP levels greater than 1000 ng/mL?
What is the effect of body position on ventilation distribution in the lungs?
What is the effect of body position on ventilation distribution in the lungs?
What occurs in Zone I of the West zones in the lung during the respiratory cycle?
What occurs in Zone I of the West zones in the lung during the respiratory cycle?
How does aging affect closing capacity (CC) and functional residual capacity (FRC)?
How does aging affect closing capacity (CC) and functional residual capacity (FRC)?
What is the primary factor determining ventilation distribution at high airflow rates?
What is the primary factor determining ventilation distribution at high airflow rates?
What happens to functional residual capacity (FRC) in a supine 70-year-old patient?
What happens to functional residual capacity (FRC) in a supine 70-year-old patient?
What is the effect of anesthesia on airway resistance (RAW)?
What is the effect of anesthesia on airway resistance (RAW)?
In what scenario does diffusion, rather than convection, occur in the lungs?
In what scenario does diffusion, rather than convection, occur in the lungs?
What factor does NOT influence the distribution of ventilation in the lungs?
What factor does NOT influence the distribution of ventilation in the lungs?
What condition is associated with an increased risk of developing atelectasis during anesthesia?
What condition is associated with an increased risk of developing atelectasis during anesthesia?
How does the application of PEEP affect pulmonary shunt and flow during ventilation?
How does the application of PEEP affect pulmonary shunt and flow during ventilation?
Which factor does NOT contribute to an increase in atelectasis?
Which factor does NOT contribute to an increase in atelectasis?
What is the relationship between age and the V/Q mismatch during anesthesia?
What is the relationship between age and the V/Q mismatch during anesthesia?
During which type of lung recruitment maneuver is pressure typically applied?
During which type of lung recruitment maneuver is pressure typically applied?
What commonly contributes to hypoxemia other than hypoventilation?
What commonly contributes to hypoxemia other than hypoventilation?
What observation is true for infants compared to adults regarding atelectasis?
What observation is true for infants compared to adults regarding atelectasis?
What occurs in regions of the lung that have a R→L shunt?
What occurs in regions of the lung that have a R→L shunt?
What is the primary difference between explicit and implicit memory inhibition at lower concentrations of inhalational anesthetics?
What is the primary difference between explicit and implicit memory inhibition at lower concentrations of inhalational anesthetics?
Which receptors are primarily responsible for the sedative effect of inhalational anesthetics like N2O and Xenon?
Which receptors are primarily responsible for the sedative effect of inhalational anesthetics like N2O and Xenon?
What is required for the activation of NMDA receptors?
What is required for the activation of NMDA receptors?
Which GABA subunit is associated with the sedative and amnesic effects of benzodiazepines?
Which GABA subunit is associated with the sedative and amnesic effects of benzodiazepines?
What mechanism primarily inhibits excitatory postsynaptic depolarization through non-NMDA receptors?
What mechanism primarily inhibits excitatory postsynaptic depolarization through non-NMDA receptors?
What is the main pathophysiologic event associated with widespread inflammation and increased permeability?
What is the main pathophysiologic event associated with widespread inflammation and increased permeability?
What is the effect of an epidural block on postoperative ileus?
What is the effect of an epidural block on postoperative ileus?
Which fibers are involved in the visceral innervation that can amplify symptoms in a 'vicious cycle'?
Which fibers are involved in the visceral innervation that can amplify symptoms in a 'vicious cycle'?
What is the role of sympathetic innervation in the functions of the GI tract?
What is the role of sympathetic innervation in the functions of the GI tract?
Which statement about visceral pain blocks is correct?
Which statement about visceral pain blocks is correct?
Which nerve is primarily responsible for parasympathetic innervation of the upper GI organs?
Which nerve is primarily responsible for parasympathetic innervation of the upper GI organs?
Which section of the GI tract is NOT innervated by the vagus nerve?
Which section of the GI tract is NOT innervated by the vagus nerve?
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Study Notes
Ventilation and Inertia
- Tissue inertia is most pronounced during rapid ventilations.
- Pleural pressure (PPL) gradient contributes to a less negative PPL at the lung base compared to the apex, affecting ventilation dynamics.
- A 1 cm vertical expansion leads to a PPL increase of 0.3 cm H2O, lessened but not negated by weightlessness.
- Ventilation distribution shifts with body position; the apex has greater PPL but lower compliance during inspiration, leading to reduced aeration compared to basal regions.
Ventilation Distribution by Flow Rates
- At low flow (rest), ventilation distribution is compliant, favoring the base over the apex.
- High airflow leads to resistance-determined distribution where base equals apex.
Closing Capacity and Age
- Closing Capacity (CC) is defined as the sum of Residual Volume (RV) and Closing Volume (CV); it remains unchanged with body position.
- Aging is associated with increased CC and Functional Residual Capacity (FRC), linked to decreased oxygenation.
- Airway closure occurs at FRC = CC, decreasing in upright individuals over age 65 and supine individuals over age 45.
- COPD and airway edema further increase CC, leading to common closure issues.
Pulmonary Blood Flow and Zones
- Blood flow (Q̇) is higher at the lung base than the apex due to hydrostatic pressure variations.
- West's zones describe lung perfusion:
- Zone I: No perfusion; alveolar pressure (PALV) exceeds pulmonary arterial pressure (PPA).
- Zone II: Intermittent perfusion; PPA exceeds PALV during systole.
- Zone III: Continuous perfusion throughout the respiratory cycle, unaffected by gravity.
- Zone IV: Reduced perfusion due to extra-alveolar vessel compression.
Anesthesia Effects on Lung Function
- Anesthesia increases airway resistance (RAW) and decreases FRC by approximately 20%.
- Static compliance of the total respiratory system is significantly reduced during anesthesia.
- Atelectasis occurs in 90% of anesthetized patients, often evident even prior to surgery.
- High body mass index (BMI) and increasing FiO2 correlate with greater atelectasis incidence.
- Oxygenation impairment is primarily due to atelectasis and airway closure.
Preventive Measures for Atelectasis
- Use of PEEP around 7 cm H2O can help reverse hypoxemia, but the effect is not proportional.
- Recruitment maneuvers entail high-pressure breaths to re-open collapsed alveoli.
- Increased FiO2 is associated with improved oxygenation post-operatively, particularly with gas resorption.
V/Q Mismatch and Gas Exchange Impairment
- At the apex, ventilation exceeds blood flow (V > Q), while at the base, blood flow exceeds ventilation (Q > V).
- Anesthesia exacerbates shunting and V/Q mismatch, particularly in older populations.
- V/Q mismatches arise from preexisting lung disease, hypoventilation, and impaired diffusion.
Visceral Innervation and Autonomic Functions
- Visceral innervation comprises myelinated A-δ fibers and unmyelinated C fibers, influencing autonomic control.
- Sympathetic innervation to upper GI organs occurs from T5-L2, while parasympathetic control is mediated via the Vagus nerve.
- Lower GI organ innervation occurs from T9-L3 through pelvic nerves influencing motility and autonomic vasoregulation.
Hepatic Function and Enzymatic Markers
- The AST/ALT ratio is key in determining hepatic injury severity; values > 1 suggest conditions like Wilson's or alcoholic liver disease.
- Bilirubin measurements indicate acute liver disease when conjugated forms are elevated; hemolysis causes both conjugated and unconjugated elevations.
- In liver disease, pre-albumin serves better than albumin to reflect protein nutrition status.
Sedation and Anesthetic Interactions
- The effects of inhalation anesthetics (IA) on memory include inhibiting explicit recall due to hippocampal impairment.
- Sedation observed from N2O and Xenon relates to antagonism of NMDA receptors.
- Structural interactions between anesthetic agents and neural receptors involve various binding dynamics, crucial for both sedative and anesthetic action.
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