Ch 105 - Thoracic Cavity Flashcards
What is normal plural fluid volume in dogs and cats?
- Dog - 0.1ml/kg
- Cats: 0.3ml/kg
What cells make up normal plueral fluid?
- mesothelial cells 9-30%
- Monocytes/macrophages 61-77%
- Lymphocytes 7-11%
- Neutrophils under 2%
1500-2500 cells/mcL
Protein less than 2.5g/dL
What % of dogs have a dorsal thoracic lymph centre?
25%
Which parts of the body are NOT drained by the thoracic duct?
- Right thoracic limb
- Right shoulder
- Cervical regions
Drained by the right lymphatic duct
What is the cisterna chyli and where is it located?
- Bipartite, dilated, retroperitoneal lymph channel, ventral to L1-L4 along cranial abdominal aorta
- Most commonly sits ventral to L3, caudal to coeliac and cranial mesenteric arteries
What is the major difference in the thoracic duct anatomy in dogs and cats?
- Dogs - travel on right sife through caudal thorax, dorsolateral to aorta. Crosses to left at T5/6
- Cats: On the left!
Where does the thoracic duct drain?
Left external jugular vein or jugulosubclavian vein
(Significant anatomical variation - some branches may terminate in azygous)
What embryonic structure forms the thymus?
At what age does it stop growing and starts to involute?
- Arises from the 3rd pharyngeal pouch
- Grows until 4-5mo
What is the normal functional residual capacity (volume of air remaining in lung at end of expiration)
45ml/kg
What fluid dynamics favour pleural fluid production and absorption?
- Increased hydrostatic pressure of systemic and pulmonary capillaries compared to pleural fluid favours pleural fluid production
- Increased osmotic pressure of systemic and pulmonary vascular beds are greater than pleural fluid, favouring absorption
Tends to enter pleural space from parietal pleura and be absorbed by visceral pleura
What are the functions of the thymus?
Cell mediated immunity
- maturation and selection of T-cells
- Termination of defective or autoreactive thymocytes
Endocrine
- Secretion of thymosin, thymic humoral factor, thymopoietin, thymostimulin, thymulin
- Involved in T-cell enhancement and maturation
How do you classify pleural transudate, modified transudate and exudate?
List causes of a pleural transudate
- Hypoproteinaemia
- Increased hydrostatic pressure as with CHF (NT-proBNP significantly higher in cats with effusion from heart disease)
List DDx for a serosanguinous (modified transudate) effusion
- Lung lobe torsion
- D-hernia with liver entrapment
- Pericardial effusion
- Right sided heart failure
- Neoplasia (diffuse mesothelioma or carcinomatosis)
- Idiopathic pleuritis
List DDx for a sanguinous effusion
- Trauma
- Coagulopathy
- Acute lung lobe torsion
- Iatrogenic
- Tumours (chemodectoma, right atrial HSA)
List DDx for chylous effusion
- Any condition that increases hydrostatic pressure in the cranial vena cava
- Trauma
- Idiopathic
How do you confirm chylothorax?
- Triglycerides higher and cholesterol lower than serum
- Chylomicrons in the fluid can be stained with Sudan black
- Positive ether clearance test
- Modified transudate (protein 2.5-4g/dL, cell count less than 7000/mcL, specific grav leass than 1.032
Pseudochylus has higher cholesterol and lower triglycerides, and absent chylomicrons.
List DDx for inflammatory effusion
- D-hernia
- Neoplasia
- Chronic chylothorax
- Lung lobe torsion
- Infectious disease
- Pancreatitis
- Penetrating FB
- Oesophageal trauma
- Repeat thoracocentesis
- Surgery
Oropharyngeal flora are most commonly isolated from cats
What is the reported rate of pneumothorax and haemorrhage after a CT-guided lung FNA?
- Pneumothorax 0-27%
- Haemorrhage up to 30%
Usually minimal and require no treatment
What is the most realiable way to differentiate transudates and exudates in cats?
- Pleural fluid lactate dehydrogenase
- Ratio of pleural fluid to serum TP.
Senstivity, specificity and accuracy 100% with a cut off for lactate at 226IU/L
Accuracy of TP ratio 95% with a cutoff greater than 0.56
What is a reliable measurement to differentiate transudate and exudate in dogs?
C-Reactive Protein
- Greater than 4mcg/ml 100% sensitive and 94% specific
- 11mcg/ml 88% sensitive and 100% specific for differentiating modified transudate and exudate
What intercostal space is used for thoracocentesis?
7th-9th
What effect does mechanical ventilation have on the lungs and heart?
- In closed chest, increases intrapulmonary pressures to 3-5cmH2O
- This decreases coronary circulation, pulmonary circulation and venous return to the heart
- Inspiratory:expiratory phases should be kept between 1:2 to 1:3
In which intercostal space is a thoracostomy tube placed?
7th or 8th
