CS: Respiratory distress

Question 1

What system dysfunction does cyanosis suggest?

Answer 1

Respiratory system problem (not cardiovascular)

Question 2

What should you do with every respiratory case?

Answer 2

Map it out - i.e. localise it to either: URT, LRT, lung parenchyma, pleural space or diaphragm

Question 3

List methods of oxygen supplementation - 8

Answer 3

• Flow-by tube of oxygen
• Masks
• Hoods
• Nasal catheter
• Cages
• Intubation and positive pressure ventilation
• Nebuliser
• Future - IV oxygen and microparticles

Question 4

Outline flow-by oxygen supplementation

Answer 4

tube of oxygen held by patient head, cheap, easy, short term, animal needs restraining

Question 5

Outline mask and hood oxygen supplementation

Answer 5

– improves effectiveness, masks well tolerated usually, not hoods. Can reach 40% oxygen delivery. Problem with a dog that is panting – poorly tolerated. A hood is a cone (post-surgery) which is covered and an oxygen tube is placed under this to deliver oxygen. Probably better than flow-by in terms of efficacy but hard to quantify. Dog will get hot and won’t be able to see.

Question 6

Outline nasal catheter oxygen supplementation

Answer 6

2 openings in nostrils, deliver a constant stream of oxygen, red rubber catheter higher percentage of oxygen delivered, ideal for restless or panting patients, LA (won’t fit in cage), long term, less waste, may be uncomfortable (the cold oxygen causes jet lesions with haemorrhage). Measure to medial canthus of eye and place this amount down the nose. Bupivicaine local anaesthetic to reduce irritation. Point in a ventro-medial direction. Suture in place (tape round first then suture it) OR use super glue.

Question 7

Outline cages for oxygen supplementation

Answer 7

box with constant oxygen supply, less stressful, accurate O2 delivery, can be humidified, no restraint, high oxygen flow BUT expensive and wasteful when door is opened. Small animals.

Question 8

Outline intubation and positive pressure ventilation for oxygen supplementation

Answer 8

may be required to stabilise the animal but may need to sedate or anaesthetise and specialist training/equipment.

Question 9

What are problems with oxygen supplementation?

Answer 9

avoid over 24 hours (oxygen toxicity  free radicals), damage to cell membranes, alveolar collapse, retinal detachment, seizures.

Question 10

Equipment for thoracocentesis

Answer 10

butterfly needle, 3 way tap, syringe, local anaesthetic

Question 11

How do you prepare to do a thoracocentesis?

Answer 11

manual restraint, sedation (don’t with dyspnoea), sternal recumbency, aspectic preparation of the skin, LA in SC tissue, muscles at proposed sites of needle injection

Question 12

How do you perform thoracocentesis?

Answer 12

attach butterfly needle to 3 way tap and syringe, ensure tap is turned off, 7th of 9th ICS half way up thoracic wall or in dorsal third of wall if only air presence is suspected, insert at cranial border of rib to avoid intercostal vessels and nerves. Advance needle lowly in a slightly ventral direction. Turn tap so gentle suction can drain space. Drainage is complete when no further air can be pulled into syringe. Turn tap off. Withdraw needle. Drainage of both sides recommended. Radiography should be performed afterwards (not really necessary if dyspnoea corrects and no other pathology is suspected).

Question 13

List 3 possible complications of thoracocentesis

Answer 13

lung laceration, pneumothorax (maintain closed system), pyothorax (maintain sterility)

Question 14

Define thoracostomy

Answer 14

surgical opening of the chest cavity (e.g. for drainage).

Question 15

When are drains indicated rather than thoracocentesis?

Answer 15

used for neoplasia and serious levels of effusion, allows continuous drainage unlike thoracocentesis (transient, e.g. sampling).

Question 16

Method - thoracic drain placement

Answer 16

Closed technique, lateral recumbency, affected side uppermost, GA necessary, clipped and prepped. Typically skin incision at 10th ICS to allow SC tunnel to be placed for 2 ICS length so drain enters 8th ICS. Local anaesthetic recommended for patients under GA (bupivicaine). Lift trocar and stap into chest wall. Chinese finger trap suture to secure in place. Monofilament nylon or propylene. AIM = to have the tube lying along sternum and stop at 1st rib. Always radiograph - check placement and that all fenestrations are in chest cavity. Cover incision with non-adherent dressing.

Question 17

How/when do you remove a chest drain?

Answer 17

• Pneumothorax - removed 24 hours after no air is aspirated. Excess fluid - remove once the daily fluid volume has declined to around 2ml/kg/day (thought to be the amount of fluid produced from the tube irritation itself). Perform without GA, cut sutures, gently pull, close skin incision. Take chest radiography before and 12-24 hours after to check for excessive fluid/air.

Question 18

Can you send an animal home with a chest drain?

Answer 18

NO - risk of pneumothorax if patient removes the chest drain.

Question 19

Why is traumatic pneumothorax often bilateral?

Answer 19

due to the fenestrated mediastinum in dogs/cats

Question 20

2 causes of pneumonthorax

Answer 20

TRAUMATIC - open or closed

SPONTANEOUS

Question 21

Define open traumatic penumothorax

Answer 21

pneumothorax due to direct communication between atmosphere and pleural space.

Question 22

Define closed traumatic pneumothorax

Answer 22

pneumothorax due to damaged pulmonary parenchyma within enclosed chest cavity.

Question 23

Outline spontaneous pneumothorax

Answer 23

– always closed, usually caused by blebs or bullae which come from air filled lesions in pleura/lung parenchyma and rupture causing pneumothorax. Especially deep chested dogs. Bleb = air from parenchyma trapped between layers of visceral pleura. Bullae = air filled space between pleura and lung surface following destruction of alveolar wall.

Question 24

Radiographic signs of pneumothorax

Answer 24

elevation of heart from sternum in lateral view due to collapsed lung lobes, radiolucent area of free air where no pulmonary vasculature, flattened diaphragm maybe.

• TRAUMATIC radiograph– any fractures/ haemorrhage, pleural effusion, pulmonary contusions.
• SPONTANEOUS radiograph – blebs/bullae appear as circular lucent cavities with thin walls at margins of lung lobes.

Question 25

Prognosis - pneumthorax

Answer 25

TRAUMATIC - good depending on other complications.

SPONTANEOUS – depends on underlying cause severity of damage.

Question 26

Other supplementary tx (to thoracocentesis and chest drain) for pneumothorax

Answer 26

Only if necessary: systemic analgesia, cage rest with sedation, supplemental oxygen, fluids.