Homeostasis I Revisit

Question 1

Openings and attachments of the diaphragm

Answer 1

Question 2

The neurovascular bundles associated with ribs are located ___ the associated rib.

Answer 2

The neurovascular bundles associated with ribs are located immediately below the associated rib.

Question 3

Below is a diagram of the superior mediastinum.

Label all of the indicated structures.

Answer 3

Question 4

Location of the oblique and transverse pericardial sinuses

Answer 4

Question 5

Sympathetic and parasympathetic innervation of the heart

Answer 5

The heart is innervated by the cardiac plexus, which consists of sympathetic (from the T1-T4 spinal cord segments), parasympathetic (from the vagus nerves) and afferent fibers and small ganglia. Their branches enter the pericardium, run along the coronary arteries to reach the myocardium (sinoatrial and atrioventricular nodes).

Question 6

Fick Equation

Answer 6

Question 7

“Lung recruitment”

Answer 7

In ARDS, lung recruitment describes the effect of PEEP that reverses atelectasis in certain regions of the lung.

However, this requires that there is a collapsed but undamaged section of lung that can be recruited. In patients without recruitable lung tissue, PEEP just increases the risk of complications such as pneumothorax.

Question 8

Full PAO₂ equation

Answer 8

PAO₂ = FiO₂ ( P_atm - 47 mmHg) - ( 1.25 * PaCO₂ )

Question 9

The equation for estimated A-a gradient does not apply when. . .

Answer 9

. . . the patient is on supplemental oxygen

Question 10

Delta ratio

Answer 10

Question 11

Urinary anion gap

Answer 11

Question 12

Estimated renal compensation for chronic CO₂ retention and respiratory acidosis

Answer 12

Δ[Bicarb] = 0.35 x (current pCO₂ - 40 mmHg)

This can be used to determine if renal compensation for a metabolic acidosis is appropriate or not

Question 13

Delta/Delta

Answer 13

The change (or increase) in the anion gap compared to the change (or fall) in the bicarbonate. This is a tool to determine if there is yet another underlying disorder.

Question 14

Renal toolbox

Answer 14

• Serum anion gap (Na - [Cl + HCO₃])
• Urine anion gap (Osm - 2[Na+K])
• Delta/delta (ΔAG / ΔHCO₃)

Question 15

Using the delta/delta

Answer 15

DD Ratio <1.0 = presence of concurrent non AG metabolic acidosis.

DD Ratio >2.0 = presence of concurrent metabolic alkalosis.

Question 16

Expected renal compensation for a respiratory acidosis

Answer 16

Acute: [HCO₃^2-] = (pCO₂ - 40)/10 +24

Chronic: [HCO₃^2-] = (pCO₂ - 40)/3.5 +24

Question 17

Expected respiratory compensation for metabolic acidosis and alkalosis

Answer 17

Acidosis: pCO_{2 expected} = 1.5 x [HCO₃^2-] + 8 +/- 2

Alkalosis: pCO_{2 expected} = 0.7 x [HCO₃^2-] + 21 +/- 1.5

Question 18

Correcting serum sodium for hyperglycemia

Answer 18

Measured sodium [mEq/L] + 0.016 * (Serum glucose [mg/dL] - 100)

Question 19

Hypertrophic cardiomyopathy progression

Answer 19

Question 20

Dilated cardiomyopathy progression

Answer 20

Question 21

Starling curves

Answer 21

Question 22

Effects of preload, afterload, and inotropy on a pressure-volume curve for the LV

Answer 22

Question 23

LV pressure volume curves in forward and backwards left-sided heart failure

Answer 23

Question 24

Starling equation

Answer 24

Question 25

Atelectrauma

Answer 25

Trauma associated with repeated opening and closing (recruitment/derecruitment) of alveoli by mechanical ventilation

Question 26

Preventing atelectrauma and barotrauma in mechanical ventilation

Answer 26

• To prevent atelectrauma, use PEEP (maintaining alveolar recruitment and end-expiration).
• To prevent barotrauma, limit tidal volume to 6mL/kg and alveolar distending plateau pressure to 30 cm water.
  
  • – note: barotrauma is a huge risk in ARDS, so ensure low tidal volume in ARDS patients especially

Question 27

Effects of PEEP on cardiovascular function

Answer 27

• Positive pressure conferred to the intrathoracic cavity by PEEP decreases the motive force for venous return, reducing net venous return
• Increased pressure within the lung also compresses pulmonary vasculature, increasing the right heart’s afterload
  
  • Note that both of these mechanisms decrease cardiac output. This may be addressed by careful and judicious administration of fluids

Question 28

Assessing mediastinal width

Answer 28

Question 29

Loss of aortic knob on CXR

Answer 29

Question 30

In order to be classified as pathologic Q waves, the waves must be. . .

Answer 30

. . . at least 25% the height of the QRS complex

Question 31

First symptom of COVID-19 vs influenza

Answer 31

For COVID, fever comes first

For Influenza, cough comes first

Question 32

Why does lying someone prone increase oxygenation in ARDS or severe pneumonia?

Answer 32

Anterior superior abdominal contents are not weighing down on the diaphragm and the lungs!

Thus, there is improved V/Q matching.

Question 33

Pathogenesis of diffuse alveolar damage

Answer 33

• Hyaline membrane formation
• Microvascular thrombosis
• Organization
• Fibrosis

Question 34

Plasma vs cell blood type compatibility

Answer 34

Question 35

Pain is ___.

Tenderness is ___.

Answer 35

Pain is subjective – it may be referred.

Tenderness is objective – you can be confident that the tender area is the source of the pain.

Question 36

Triangles of the biliary tree

Answer 36

Question 37

Most common sources for patients presenting with fever

Answer 37

• Respiratory
• Urinary
• Biliary
• Skin
• Fever RUBS people the wrong way

Question 38

Where EKG leads are relative to the heart

Answer 38

Question 39

Blood supply of the cardiac conduction system

Answer 39

Question 40

nt-proBNP

Answer 40

Lab to order as evidence for atrial stretch: when heart failure or fluid overload are suspected.

Note that there is wide patient-to-patient variability in nt-proBNP, and so to use it practically you need to know the patient’s “dry” nt-proBNP

Question 41

Airway sound summary

Answer 41

Remember: The ronchorous ronchi come from the bronchi (when they are surrounded by consolidation)

Question 42

Beck’s triad

Answer 42