Non cardiogenic pulmunary edema

Question 1

What are the two reported primary neurologic causes of neurogenic pulmonary edema in dogs?

Answer 1

seizures
traumatic brain injury

Question 2

What are the proposed causes of neurogenic pulmonary edema in hunting dogs?

Answer 2

• severe sympathetic drive from exercise and excitement
• excessive barking leading to postobstructive type pulmonary edema
• Physical exertion with resultant hypoglycemic effects on the brain

Question 3

explain the proposed pathophysiological mechanism of NPE

Answer 3

Both theories are on the basis of brain injury causing fulmonant sympathetic stimulation

• vasoconstriction –> increaed arterial and venous pressures –> increased left ventricular afterload –> overwhelmed LV –> left sided congestion + vasoconstriction –> shunting of blood to the central organs –> increased pulmonary capillary hydrostatic pressure –> endothelial damage –> exudation of protein-rich fluid
• sympathetic stimulation directly causes increased capillary permeability –> edema independent of pulmonary capillary pressure changes
• Production of reactive oxygen species may also play a role

Question 4

How does NPE present of rads?

Answer 4

NPE most commonly showed a bilateral, symmetric, multifocal, mixed alveolar to interstitial lung pattern, focused in the caudal lung lobes or distributed throughout all lung fields.

Question 5

What side of the lung is most commonly affected in case of unilateral distribution?

Answer 5

For the few animals with unilateral distribution, the changes were found
on the right side of the lung.

Question 6

what is the proposed pathophysiology of electrocution induced neurogenic pulmonary edema?

Answer 6

suspected to the same as from TBI or seizures –> nervous tissue has a high tendency to conduct electricity –> CNS damage –> sympathetic surgery

Question 7

What is the prognosis for NPE in general?

Answer 7

Good. Resolve within a few days with minimal support.

Question 8

T/F: in NPE caused by electrocution, most of the patients develop resp sign even if face of clear rads

Answer 8

F: respiratory signs after electrocution were only observed in about 30% of cases in 1 report, even in the face of radiographic changes.

Question 9

What is the pathophys of NPE caused by electrocution?

Answer 9

same pathophysiologic mechanism as
NPE. Nervous tissue has a high tendency to conduct electricity, predisposing the CNS to damage by electrical current, which then is believed to cause a sympathetic discharge similar to other types of
NPE.

Question 10

What do you expect to see in rads performed on dogs after after electrical injury?

Answer 10

Diffuse alveolar or mixed interstitial and alveolar pattern with a concentration
in the caudodorsal fields.

Question 11

Name at least 6 causes of post obstructive
pulmonary edema.

Answer 11

• tracheal collapse
• strangulation including
  excessive pulling on a leash
• brachycephalic airway syndrome
• pharyngeal obstruction by a foreign body
• laryngeal edema
• laryngeal paralysis
• laryngeal polyp
• pharyngeal fibrosarcoma
• excitement while being manually restrained.

Question 12

Explain the pathophysiology of postobstructive pulmonary edema

Answer 12

forcible inspiration against a closed epiglottis-» drastically decreased intrathoracic pressure
-» decreases pulmonary interstitial hydrostatic prex
-» increases venous return to the RA/RV and lungs
-» compination causes an increased transcapillary prex gradient-» pulmonary edema
-» negative intrathoracic prex increases LV afterload –> further increases pulmonary capillary prex

additional sympathetic surge from dyspnea (similar to neurogenic pulmonary edema mechanism)

Question 13

What are the two types of postobstructive pulmonary edema?

Answer 13

Type 1: acute onset during obstruction from marked sudden negative intrathoracic pressure

Type 2: chronic airway obstruction –> exhalation against obsutrction causes intrinsic PEEP
* when the obstruction is relieved –> the PEEP abades –> sudden drop in pressure –> mechanism similar to Type 1

Question 14

How does post-obstructive pulm edema appear on CXR?

Answer 14

symmetric, alveolar–interstitial focal to
multifocal pulmonary pattern with a bilateral distribution usually in
the caudodorsal lung fields. In animals with a unilateral distribution
(39%), the pulmonary edema was found almost exclusively on the right
side.

Question 15

What is the most common reported causes of re-expansion pulmonary edema in dogs and cats? Which species is more commonly affected?

Answer 15

• correction of a traumatic diaphragmatic hernia
• cats more common than dogs

Question 16

How soon after re-expansion does pulmonary edema typically happen?

Answer 16

within 24 hours after atalectasis - but can occur as instantly as within 1 minute

Question 17

Explain the pathophysiology of re-expansion pulmonary edema

Answer 17

No completely understood. Theories include:
* re-expansion causes significant negative interstitial pressure –> favor fluid shift from capillaries into interstitium
* pressure changes may cause capillary endothelial damage
* inflammatory mediators and ROS from ischemia-reperfusion injury

Question 18

T/F: to avoid re-expansion pulmunary edema in a pt with pleural effusion, the rate of fluid removal is more important than the quantity removed

Answer 18

T

Question 19

What drugs have been reported as cause of pulmunary edema in dogs and cats?

Answer 19

Dogs: cytarabine, ingested tetrahydrocannabinol, treatment with IV
lipid emulsion
Cat: vincristine overdose

Question 20

Explain the phatophys of lung injury due to drowning.

Answer 20

• aspiration of liquid –> alterations/wash away surfactant –> alveolar collapse, ventilation–perfusion mismatch, and pulmonary hypertension.
• aspiration of liquid –> damaging the alveolocapillary barrier and pneumocytes –> can later on lead to ARDS
• Severe sympathetic surge as a response to stress and hypoxia may lead to a neurogenic-type edema
• breathing against a vagally mediated laryngospasm –> similar to postobstructive pulmoanry edema

Question 21

Describe your ideal setting for HFNO (including cannulae size)

Answer 21

• choose a cannula size that does not occludemore
  than 50% of the nostril diameter in order to avoid excessive pressure
  build-up and re-breathing of CO2
• starting flow rate of 0.4–2 L/kg/min; alternatively, the
  flow rate can be based on the patient’s minute ventilation (TV of 10ml/kg x RR)
• FiO2 should initially be set to 100% with the goal of decreasing it to the lowest concentration that will maintain an SpO2
  of 95% or higher.
• T 37–38◦C (98.6–100.4◦F)

Question 22

What is lung protective ventilation?

Answer 22

ventilation with lower TV and higher PEEP in order to avoid lung overdistension and cyclic
collapse and re-opening of alveoli, both of which can exacerbate inflammation
in the lung

Question 23

What are the only 2 drugs recommended in people with ARDS?

Answer 23

neuromuscular blocking agents and glucocorticoids
+ negative fluid balance

Question 24

What is the proposed mechanism by which furosemide helps in noncardiogenic pulmonary edema?

Answer 24

direct pulmonart vasodilatory properties