Week 9 - Effusions and Edema

Describe the steps for a thoracocentesis.

1) Go between - 6, 7, 8 makes you breathe great (6-7 ICS; Upper ⅓ for air, lower ⅓ for fluid)

2) Shave and aseptically prep using dirty and clean scrub (chlorhex, alcohol)

3) Lidocaine 2%

4) Cranial to rib (caudal contain nerve and artery)

5) Use butterfly needle (cats) or catheter (16-22g; 1-1.5 inches), extension set, 3-way stopcock, 30-60 mL syringe, collection tubes (LTT and RTT) and container, graduated cylinder

6) Advance slowly with the stylet (bevel up!) until you feel a "pop" — this is you entering the pleural space. Withdraw on the syringe to confirm you are in the proper place.

7) Once in the pleural space, advance a tiny bit more and withdraw the stilet. Aim catheter downwards to avoid touching lung tissue

Describe the steps for a pericardiocentesis.

1) Shave and aseptically prep

2) 2% lidocaine

3) Heavy sedation! Oxygen and ECG

4) Use right hemithorax at the point of the elbow (4-5th ICS; Less likely to hit coronary vessels and has cardiac window)

5) Using large catheter (14-18g) or angiocatheter, and same supplies

What is the potentially fatal complication of pericardial effusion?

- Tamponade

During a gross evaluation of fluid (i.e., from a centesis) what should be assessed?

- Color

- Clarity

- Viscosity

What are the components of a complete fluid analysis?

- Gross evaluation (color, clarity, viscosity)

- Automated cell count

- Protein by refractometry

- Cytologic evaluation

- Effusion clasisifcation

What is the cellularity and protein level of a low-protein transudate?

- Low cellularity (< 5k cells/microliter)

- Low protein (< 2.5 g/dL)

Describe the gross appearance of a low-protein transudate.

- Clear

- Transparent

What are causes of pleural low-protein transudate?

- Increased hydrostatic pressure (lymphatics or venous - Organ torsion, Non-exfoliating neoplasia, Clot, Cardiac disease)

What are causes of peritoneal low-protein transudate?

- Portal hypertension

- Severe hypoalbuminemia (<1.5 g/dL) secondary to things like PLE/PLN

- Increased hydrostatic pressure (lymphatics or venous - Organ torsion, Non-exfoliating neoplasia, Clot, Cardiac disease)

When performing a centesis, one should never remove more fluid than is ______________________ necessary.

- Therapeutically

What is the cellularity and protein level of a high-protein transudate?

- Low cellularity (< 5k cells/microliter)

- High protein (> 2.5 g/dL)

What are causes of a pleural high-protein transudate?

- Neoplasia

- Cardiac disease

- Lung lobe torsion

- Clot

What are causes of a peritoneal high-protein transudate?

- Neoplasia

- Cardiac disease

- Sinusoidal hypertension

- Vasculitis

- FIP

- Pancreatitis

What are causes of a pericardial high-protein transudate?

- Cardiac disease

- Idiopathic

What is the cellularity and protein level of an exudate?

- High cellularity (> 5k cells/microliter)

- High protein (> 2.5 g/dL)

What causes exudate formation?

- Lots of inflammation resulting in egress of cells from vasculature (i.e., pancreatitis, pneumonia)

What are the types of exudates?

- Hemorrhagic

- Chylous

- Uroperitoneum

- Biliary peritonitis

- GIT rupture/septic peritonitis

- Pyothorax

- Neoplastic

How can one determine if fluid from an abdominocentesis is truly hemorrhagic or if they simply hit a blood vessel?

- Hemorrhagic effusions will not clot because the parietal lining has fibrinolytic properties

- Blood from a vessel will clot

What are some defining characteristics of a hemorrhagic effusion?

- PCV is measurable (>1%)

- Cytology: Hemosiderin in macrophages, many RBCs

What are some causes of hemorrhagic effusions?

- Mass rupture (⅔ neoplastic - i.e., HSA; ⅓ hematoma)

- Trauma

- Cancer-associated

- Coagulopathy (i.e., rodenticide - secondary hemostatic defect)

- Anaphylaxis

- Left atrial tear

What are some defining characteristics of a chylous effusion?

- Cytology: Small lymphocytes predominate +/- reactive lymphocytes, lipid laden macrophages and neutrophils

- White to pink grossly and will form a "cream" layer if left standing

- Fluid Triglycerides > 2X serum triglycerides (Can be > 100 mg/dL in the fluid)

What is the primary mechanism behind a chylous effusion?

- Increased lymphatic pressure

What are some causes of chylous effusions?

- Cardiac disease

- Idiopathic

- Neoplasia (mediastinal mass)

- Clot

- HW

- Trauma

- Fungal

Describe the gross appearance of fluid from a uroperitoneum.

- Yellow, transparent to flocculent

What are some defining characteristics of a uroperitoneum?

- Initially low cell count and proteins but can become exudative over time (because urine is irritating/caustic and calls inflammatory cells to the site)

- Creatinine in fluid is over 2x the creatinine in serum

- Potassium in fluid is over 1.4 times (dogs) or over 1.9 times (cats) the potassium in the serum

What are some causes of urinary rupture?

- Trauma

- Urinary obstruction (urolithiasis, neoplasia, cystitis)

What are some defining characteristics of a biliary peritonitis?

- Can be low cell and low protein initially but can become exudative over time (because bile is irritating/caustic and calls inflammatory cells to the site)

- Cytology: Yellow-brown to green-brown bile extracellularly and within macrophages

- Bilirubin in fluid is over 2 times the bilirubin in serum

What are some causes of biliary rupture?

- Trauma

- Gallbladder mucocele

- Cholelithiasis

- Neoplasia

- Severe inflammation

- Complication of cholecystocentesis

What are some defining characteristics of a GIT rupture/septic peritonitis?

- Usually flocculent (invariably an exudate)

- Cytology: Lots of degenerative neutrophils +/- intra/extracellular bacteria

What are some defining characteristics of a "septic" body cavity?

- Lactate in the fluid minus lactate in the serum is over 2 mmol/L (Lactate higher in the fluid as it is produced by bacteria)

- BG in serum minus BG in fluid is over 38 mg/dL (Glucose lower in the fluid because it is used by bacteria)

What are some causes of GIT rupture?

- Trauma

- Severe inflammation

- Obstruction

- Torsion

- Intussuception

- Neoplasia

A pyothorax usually looks like __________ grossly.

- Pus

What are some defining cytologic characteristics of a pyothorax?

- Degenerative neutrophils

- +/- intra/extracellular bacteria

What are some causes of a pyothorax?

- FB (If you seen filamentous bacteria, more likely a FB as these are environmental pathogens)

- Bite wounds

- Pneumonia

- Exudate that is chronic can become infected

- Esophageal/tracheal rupture

Describe how well the following types of cancers exfoliate.

A. Sarcomas

B. Round cell tumors

C. Carcinomas

- Round cell tumors > Carcinomas > Sarcomas

What may be seen on cytology of a neoplastic effusion?

- May see neoplastic cells and concurrent inflammation

What is edema?

- Fluid within the interstitium

What are the forces involved in movement of fluid from the vessels to the interstitial space?

- Capillary pressure (hydrostatic)

- Plasma colloid osmotic pressure

- Interstitial fluid pressure (hydrostatic)

- Interstitial fluid colloid osmotic pressure

What are the 2 most important questions to consider regarding edema?

- What is the distribution?

- Is it pitting vs. non-pitting?

What does the distribution of edema indicate?

- Widespread = systemic involvement more likely or multicentric disease (sepsis, angioedema, fluid overload, etc.)

- Localized = More likely to be from venous or lymphatic abnormalities -> Look for external wounds (vasculitis (i.e., secondary to a catheter), mass occluding venous/lymphatic draininge

What is the difference between pitting vs. non-pitting edema?

- Pitting = displacement of fluid within interstitial space

- Non-pitting = intracellular swelling or chronic interstitial fluid

What are some causes of pitting edema?

- Increased vascular permeability (SIRS/sepsis)

- Increased hydrostatic pressure/venous obstruction (mass, torsion, clot, fluid overload)

- Lymphatic obstruction (mass, torsion, clot)

- Hypoalbuminemia (decreased plasma colloid oncotic pressure)

What are some causes of non-pitting edema?

- True "swelling" = cellulitis (Post-surgical, traumatic, wound-related)

- Angioedema ("Allergic reaction" - similar to urticaria, envenomation)

- Myxedema (hypothyroidism)

- Chronic pitting edema (i.e., chronic lymphedema - Essentially, enough collagen comes in to where it is not longer elastic/pitting)

- Lymphangiosarcoma (rare)