24. Trauma of the chest wall and lungs. Neoplasia of the lungs. Pneumothorax. Diagnosis and therapy. Lobectomy. Thoracic drainage. Thoracocentesis.

How many ribs do dogs have?

13 (9 true ribs attached to the sternum)

How many thoracic vertebrae do dogs have?

13

How many sternebrae do dogs have?

9 (manubrium, body, xiphoid process)

Which organs are found in the thorax?

1. GIT (oesophagus)

2. Cardiovascular (heart, aorta, pulmonary arteries, vena cava, pulmonary vein)

3. Respiratory (trachea, bronchi, bronchioles, lungs)

Where does the oesophagus run in relation to the trachea?

Dorsally

Where is the heart located in the thoracic cavity?

Middle, tilted slightly left

How does the aorta travel from the heart?

From the left ventricle, it arches dorsally and travels caudally

What are the two main parts of the aorta?

Ascending and descending aorta

What is the function of the pulmonary arteries?

Carry deoxygenated blood from the right ventricle to the lungs

Which vessels carry deoxygenated blood to the right atrium?

Cranial and caudal vena cava

Which vessels carry oxygenated blood from the lungs to the left atrium?

Pulmonary veins

What is the path of airflow in the respiratory system?

Trachea → bronchi → smaller bronchi → terminal bronchioles → alveoli

What are the pleural membranes?

Visceral pleura (covering lungs) and parietal pleura (lining thoracic cavity)

How many lobes does the left lung have?

Two (cranial and caudal)

How many lobes does the right lung have?

Four (cranial, middle, caudal, and accessory)

Where is the accessory lobe of the right lung located?

Dorsal to the caudal vena cava and medial to the plica vena cava

What is crucial for stabilising trauma patients?

Ensuring ABCs (Airway, Breathing, Circulation) are monitored

What is a contraindication for premedication in respiratory patients?

Drugs that cause hypoventilation. Use butorphanol + acepromazine

What is often required for animals with open chest cavities?

Intermittent positive pressure ventilation (IPPV)

What is advantageous about inhalation anaesthesia?

Rapid recovery and precise control of anaesthetic depth

When is an intercostal nerve block *not* appropriate?

In patients with lung disease

Where is the needle inserted for an intercostal nerve block?

Insert needle on dorsal surface of rib, keeping as caudal as possible, till you hit bone surface. Then direct caudally along surface of rib until it reaches soft tissue. 2-3 intercostal nerves are blocked before & after planned target area

Which nerves are blocked in an intercostal nerve block?

Intercostal nerves (2-3 before and after target area)

What is the typical volume of local anaesthetic used for an intercostal nerve block?

0.25-1ml of 0.5% bupivacaine + 4% articaine

What are some common causes of chest wall and lung trauma?

Traffic accidents, bites, gunshot wounds, falls, kicks, blunt force → pneumothorax, fractured rib, wounds of pleura/lungs

What are some clinical signs of chest wall and lung trauma?

Dyspnoea, pain, shock, emphysema, pneumothorax, haemothorax

Animals should be evaluated for flail chest, pulmonary contusions or lacerations & diaphragmatic rupture.

What is flail chest?

Multiple segmental rib fractures resulting in a free-floating segment of the thoracic wall → severe respiratory distress, pain & hypoventilation

What are some diagnostic methods for chest wall and lung trauma?

History, clinical signs, thoracocentesis, X-ray (thorax and abdomen), ultrasound

What lab finding from a thoracocentesis suggests internal bleeding?

> 5 g/dl protein

What is the radiological finding of pneumothorax?

Heart is elevated from the sternum

What are some initial treatments for chest wall and lung trauma?

Stabilisation (fluids, oxygen, compress bleeding, cover wounds), thoracocentesis, blood transfusion, analgesia (fentanyl, buprenorphine)

What are some surgical treatments for chest wall and lung trauma?

1. Debridement

2. Rib fracture repair (pins, cerclage wire)

3. Flail chest stabilisation (external splints for 4 weeks; fastened with percutaneous sutures and aluminium frame)

What is a pneumothorax?

Presence of air in the pleural space, causing lung collapse

What is a crucial initial step before further clinical exam if pneumothorax is suspected?

Immediate thoracocentesis

What are some causes of pneumothorax?

Traumatic, spontaneous (neoplasia, abscess), iatrogenic, infectious

What are the types of pneumothorax?

Open (pleurocutaneous) or closed (pleuropulmonal, pleuroesophageal)

What is a tension pneumothorax?

One-way valve effect trapping air in the pleural space → decreases ventilation and venous return → a life-threatening emergency

What is the result of pneumothorax?

Compromise intrapleural pressure → partial lung collapse → low tidal volume → hypoxia, hypercapnia & CV compromise

What are some clinical signs of pneumothorax?

Respiratory distress, shallow, rapid breathing, cyanosis, tachycardia, dull/absent lung sounds

How is pneumothorax diagnosed?

History, clinical signs, X-ray (elevated heart from sternum)

What are some treatments for pneumothorax?

Thoracocentesis, wound closure, thoracostomy tube and drainage

How common are primary lung tumours?

Uncommon

How common are secondary/metastatic lung tumours?

Extremely common

What are some examples of tumours that commonly metastasise to the lungs?

Mammary carcinoma, thyroid carcinoma, hemangiosarcoma, osteosarcoma, squamous cell carcinoma

What are some clinical signs of lung tumours?

Non-specific; non-productive cough, dyspnoea, pyrexia, lethargy, exercise intolerance, dysphagia

How are lung tumours diagnosed?

History, X-ray, ultrasound, biopsy, cytology

What are differential diagnoses of lung neoplasia?

Pneumonia, bronchitis, brochiectasis, pulmonary fibrosis, congestive heart failure

What is the treatment for lung tumours?

Thoracotomy, lobectomy (partial or total), removal of affected thoracic wall

What are examples of surgical procedures of the thorax?

1. Lobectomy

2. Thoracic drainage/thoracostomy tube

3. Thoracocentesis

4. (Thoracotomy)

What is a lobectomy?

Surgical removal of a whole or part of a lung lobe via intercostal thoracotomy or median thoracotomy

What are the steps involved in a partial lobectomy?

1. Clamp it: place two crushing forceps proximal to lesion

2. Suture it: Place continuous, overlapping suture pattern proximal to each forceps

3. Cut it: between the clamp and suture.

4. Over-sew the lung in a simple continuous pattern

What are the steps involved in a complete lobectomy?

1. Ligate & transect the vasculature to the affected lobe

2. Clamp the main bronchus with crushing forceps

3. Sever the bronchus between the clamps & remove the lung

4. Suture the bronchus in a continuous horizontal pattern

5. Over-sew the bronchus end in a simple continuous pattern

What is the purpose of a thoracostomy tube?

Allows intermittent or continuous pleural drainage

Where are intercostal nerve blocks typically performed for thoracic drainage?

7th, 8th, and 9th intercostal spaces, dorsally and caudal to each rib

What is the procedure for putting in a thoracostomy tube?

1. Intercostal nerve blocks at 7th-9th ICS

2. Skin incision in 9th/10th ICS

3. Make subcutaneous tunnel from 10th to 8th ICS, inserting tube through 8th ICS towards opposite shoulder

4. Suture drain to skin with Chinese finger trap

What is thoracocentesis?

Surgical puncture of the thoracic wall to remove air or fluid from the pleural space

When is thoracocentesis indicated?

Should be performed on any animal that has evidence of pleural effusion on physical examination or thoracic radiograph

What instruments are needed for thoracocentesis?

Needle, three-way stopcock, extension tube, syringe

Where is thoracocentesis typically performed?

6th, 7th, or 8th intercostal space

What is the procedure for a thoracocentesis?

1. Insert needle at cranial portion of rib (avoids vessels and nerves at the caudal portion), just below the rib-cartilage junction. More dorsally if pneumothorax, more ventrally if fluid is suspected in pleural space.

2. Advance needle in 45 degree angle, downwards, parallel to body wall (avoids stabbing the lung)

3. While entering the body, have a small amount of negative pressure in the syringe as the needle passes the thoracic wall – when in pleural space sucks in the air in the syringe and you know that you are in the right place (the pleural cavity).

4. Aspirate fluid/air. Stopcock allows for removal of fluid w/o possibility to let air get sucked into the cavity through the tube

What is a thoracotomy?

Surgical procedure to access the thoracic cavity

What are some indications for thoracotomy?

Lobectomy, tracheotomy, oesophagotomy, persistent aortic arch repair, lung surgery

What are the two main types of thoracotomy approaches?

Median thoracotomy/sternotomy and intercostal thoracotomy

What does a median thoracotomy/sternotomy provide exposure to?

Both sides of the thoracic cavity

What are the steps involved in a median thoracotomy/sternotomy?

1. Transect sternebrae longitudinally on the midline with a sternal saw, chisel and osteotome, or bone cutters

2. Add drainage tube subcostal & lateral to midline before closure.

3. Closure: depend on animal size; close with wires or heavy sutures places around sternebrae

Which structures are easily manipulated through a median thoracotomy/sternotomy?

Caudal vena cava, main pulmonary artery, pericardial sac

What is an intercostal thoracotomy?

Incision between two ribs

What muscle layers are incised during an intercostal thoracotomy?

Latissimus dorsi, serratus ventralis, scalenus, external and internal intercostal muscles

Which intercostal spaces are typically used for different thoracic procedures?

• Cranial oesophagus (3rd-4th)

• Heart (4th-5th)

• Lungs (5th-6th)

• Thoracocentesis (6th-8th)

• Caudal oesophagus (7th-9th)

• Thoracostomy tube (10th-12th)

What is important to keep out of the suture line during closure of an intercostal thoracotomy?

Fat

Where is the drainage tube placed after an intercostal thoracotomy?

Two ribs away from the incision, dorsally

How are the ribs closed during an intercostal thoracotomy?

Preplace 4-8 sutures around two ribs either side of the incision, criss-cross arrangement for easy organisation of sutures, tied during inspiration. Start from centre suture.

Which muscle layers are sutured during closure of an intercostal thoracotomy?

All except the intercostal muscles

What is the final step after closure of the chest cavity?

Thoracocentesis

Is a thoracotomy painful, and what should be given?

Yes, opioids.