By Tami Lind, BS, RVT, VTS (ECC)

There are many indications for placing a chest tube, or thoracic tube, in a patient. Chest tubes can be placed because of a pneumothorax, pleural effusion, chest injury, or after thoracic surgery. Most of the time, chest tubes are placed when evacuation of air or fluid needs to be done more than once in a short period of time. Chest tubes can prevent the veterinary staff from needing to perform multiple thoracocentesis on the patient causing unnecessary pain and discomfort.

Patients in need of a thoracocentesis usually come into the hospital in respiratory distress. A thorough physical exam is needed upon presentation. Lung sounds are usually decreased in the dorsal region when there is a pneumothorax and in the ventral region when there is effusion (air floats and fluid sinks). Other findings on physical exam can include a heart murmur, tachycardia, coughing, or distended jugular veins.

The most important thing to remember is these patients can get stressed easily. Breaking up physical exams into short increments will help keep patient stress levels down. Oxygen therapy will help these patients improve oxygen perfusion to their organs. Light sedation may be needed to help keep the patient calm. Often, when these patients are stressed, they will go into respiratory arrest if no intervention is done. A quick thoracic ultrasound can be a good diagnostic tool when diagnosing thoracic effusion.

Removal of the fluid or air is needed in these patients for multiple reasons. When there is fluid or air in the thoracic cavity, the lungs are unable to expand. If there is minimal air intake because the lungs cannot expand, the alveoli are unable to take in oxygen; there is not enough air pressure to keep them open to take in that oxygen and transfer it to the blood stream.

Thoracocentesis can help alleviate the pressure on the lungs, allowing them to expand and deliver oxygen to the rest of the body. Performing a thoracocentesis on pleural effusion will also help collect the fluid to determine the origin and aid in diagnosis. Cytology can be performed, and a source may be determined. Multiple types of fluid can collect in the thoracic cavity.

A patient can have a pyothorax, chylothorax, hemothorax, or unknown effusion that can be classified even further into transudate, modified transudate, or exudate. Pyothorax fluid is a purulent material that is usually milky white or lightly pink in color. Upon cytology, white blood cells and bacteria are found.

Pyothorax can happen because of foreign material in the thoracic cavity or bite wounds to the chest that have gone undetected. Chylothorax is an accumulation of chyle from lymphatic cells. This fluid will also have a milky appearance to it due to fat cells that accumulate. Chylothorax can happen by trauma or blockage of the thoracic lymphatic duct.

Finally, hemothorax is an accumulation of red blood cells. This can be due to trauma or a bleeding disorder. It is important to quickly do more diagnostics if a bleeding disorder is suspected. Other types of effusion are transudate, modified transudate, and exudate. Upon cytology, transudates have low total protein (<3g/dl) and low nucleated cell counts (<500 cell/mcL).

Transudates are most associated with hypoalbuminemia. Modified transudates have a total protein of 3-5g/dl and a nucleated cell count of less than 5000cells/mcL. When a modified transudate is found, it is most commonly due to heart failure, neoplasia, or torsions. Exudates have high total protein, (3-7 g/dl), and a total cell count of over 100,000 cells/mcL. Exudates are blood, chyle, or purulent fluid. Neoplasia is a very common cause of any effusion in the thoracic cavity.

The procedure

Performing a thoracocentesis is a simple procedure. Materials needed include: clippers, sterile scrub, sterile gloves, lidocaine, hypodermic needle or butterfly catheter or intravenous catheter, an extension set, a three-way stopcock, a syringe, a bowl, a red-top tube, a purple-top tube, and slides. It is imperative not to stress the patient during this procedure. Light sedation may be needed.

Clip and scrub the area to be tapped. The landmark for a thoracocentesis is between the seventh and ninth rib spaces. If a pneumothorax is expected, clip more dorsally. If fluid is expected, clip the hair ventrally.

Whomever is performing the thoracocentesis should wash their hands and don sterile gloves. There should be a person restraining and another person to suction off the fluid. The sterile person will be handed the needle and extension set or butterfly catheter. The person who will be suctioning will take the syringe, three-way stopcock, and one end of the extension set. The sterile person will then find their landmark and insert the needle cranial to the rib. The arteries and nerves run caudal to the rib. Significant hemorrhage can occur if an artery is punctured.

Once the needle is in the thoracic cavity, suction can be applied to the syringe. A three-way stopcock can help push fluid into a bowl without disconnecting the syringe. Place the fluid in a red-top tube, a purple-top tube, and on a slide to perform cytology. Suction can be stopped once negative pressure is achieved or lung tissue is felt at the end of the needle. A quick thoracic ultrasound scan can help to determine if enough fluid or air was removed from the pleural cavity to allow proper lung expansion.

A pneumothorax can be a complication of a thoracocentesis if the lung tissue is punctured. A chest or thoracic tube is warranted if there is continuous suction with no negative pressure or if fluid builds up too quickly causing the patient distress.

Different tubes

There are multiple types of chest tubes. The most common types are over-the-wire tubes, trocar tubes, and red rubber catheter tubes. Over-the-wire tubes are a small-bore tube made commercially. It uses the Seldinger technique for placement. Trocar tubes are large-bore tubes that use a metal rod with a piercing end on it. These tubes are used less commonly because of increased risk of further thoracic trauma.

A red rubber tube can be used when the other options are not available. With a red rubber tube, the technician will need to also have a catheter adapter, a three-way stopcock, and injection caps. The red rubber tube will also need to be outfitted with more fenestrations at the distal end to ensure fluid will be able to be suctioned out from the cavity.

When placing a chest tube, the patient must be heavily sedated or under general anesthesia. Administer pain medications to the patient before the procedure. Clip and scrub the area where the chest tube will be placed. The materials needed are: surgical instruments needed to cut into skin, clamps, suture scissors, hemostats and forceps, scalpel blades, catheter adaptors, three-way stopcocks, the chest tube, sterile scrub, gloves, and suture.

Placing an over-the-wire chest tube is quite simple. A small incision is made over the area that the chest tube should be placed. Trocar tubes can be very traumatic to a patient and can cause more trauma if not placed properly. Red rubber catheters can be placed just like the trocar tube, but blunt dissection of the muscle will be needed. A catheter adapter, three-way stopcock, and injection caps will be needed once the tube is in place. A finger trap suture technique can be used to secure the chest tube in.

Suctioning the chest tube after placement is required. Then a radiograph can ensure proper placement. Complications can arise when placing a chest tube. One of those complications is the chest tube can become kinked inside the thoracic cavity. Another complication of placement is a pneumothorax, if the chest tube was placed because the patient had fluid in the thoracic cavity. The chest tube should be facing the cranial. Care must be ensured to not place the chest tube caudally. Placing a chest tube the wrong way can possibly pierce the diaphragm, creating more complications for the patient.

An adhesive covering of the chest tube insertion site should be placed to keep the site clean and dry. A stockinette or t-shirt can help keep the chest tube in place. Suction of the chest tube should occur every two to four hours, or as needed for the patient. There is a proper procedure to suction air and fluid from a chest tube. The technician must wear gloves. Obtain a syringe and bowl. The syringe is then attached to the three-way stopcock. The chest tube is opened to the syringe and fluid or air can be aspirated.

The technician must ensure they do not push air or fluid back into the chest tube. This can introduce bacteria from the outside area or create a pneumothorax. Suction is finished when negative pressure is achieved. If negative pressure is not achieved, then continuous suction may have to be used. Chest tubes are considered foreign objects in the body. There will be fluid produced around the chest tube that will be normal. It is assumed the chest tube can be removed once the tube is only producing ~2mls/kg/day of fluid. Minimal to no air must be suctioned off if the patient had the chest tube placed because of pneumothorax.

Chest tubes cause discomfort to the patient so it is important to keep these patients on pain medication until the chest tube is removed. Cleaning of the chest tube insertion site should be done every eight to 12 hours or as needed. The insertion site should be checked every 24 hours for inflammation or swelling. The patient's kennel should be kept clean and dry. These patients should never go home with a chest tube still in place.

Continuous suction can help a patient that has a continuous pneumothorax or fluid that keeps building up in the thoracic cavity. There are multiple types of commercially made continuous suction devices. These systems must be hooked to a vacuum device. One chamber is to collect fluid, collection chamber. The middle chamber is the water seal chamber, and the third chamber is the suction control chamber. The water seal chamber is a barrier between the thoracic cavity and the outside world. Bubbles will be present in this chamber if the patient has a pneumothorax. Each commercially made suction unit is made differently. Please see the instruction manual for set up. Just remember, this is a sterile procedure, so keep everything as sterile as possible. The water seal chamber is the same in all continuous suction units. The water level must be maintained at 20 cm. There is no real evidence showing why 20 cm H₂O is the best for patients. Slow steady bubbling in the suction control chamber also must be maintained; this is the speed at which suction is occurring. Too high a rate of suction can cause faster evaporation of water from this chamber which then creates faulty suction. It can also collapse flexible chest tubing which defeats the purpose of suction. Slow, steady bubbling can be achieved by using a suction regulator. If a suction regulator is not available, an adjustable C-clamp can be used on the suction tubing.

There are multiple nursing concerns when a patient is on continuous suction. The suction chamber must not tip over. This can be quite difficult when you have a rambunctious patient. This can cause the sterile water to go into other chambers and cause suction problems and inadequate suction.

If there are bubbles in the water seal chamber and your patient does not have a pneumothorax, the patient may be disconnected from the suction unit. If this happens, quickly clamp the chest tube and suction manually until negative pressure is achieved. The chest tube insertion site must be checked frequently for drainage or inflammation. Suction should occur every two to four hours or as directed by a clinician. Remember, gloves must be worn with any patient with a chest tube.

Chest tubes can be kept in-place until the drainage or air has decreased. Remember, a chest tube will always produce at least 2mls/kg/day of fluid because it is a foreign object in the body. To remove the chest tube, the sutures can be cut and removed, and the chest tube should be taken out in a swift, fluid motion.

Tami Lind, BS, RVT, VTS (ECC), is the current ICU and ER supervisor at Purdue University Veterinary Teaching Hospital. Lind has been at the university for 10 years. She went to veterinary technology school at Purdue and graduated in 2010 with her bachelor's degree in veterinary technology and has never left. She started as a veterinary technician in the ICU and has been the supervisor at Purdue since 2012.

References

1. Burknoff M., Respress M. Thoracocentesis. In: Drobatz K, Hopper K, Rozanski E, Silverstein D, editors. Textbook of Small Animal Emergency Medicine. Hoboken NJ: Wiley; 2019, pp. 1195-1198.
2. Lynch A, Campos S. Thoracostomy Tube Placement. In: Drobatz K, Hopper K, Rozanski E, Silverstein D, editors. Textbook of Small Animal Emergency Medicine. Hoboken NJ: Wiley; 2019, pp. 1199-1201.
3. Sigrist N. Thoracostomy Tube Placement and Drainage. In: Silverstein DC, Hopper K, editors. Small Animal Critical Care Medicine. 2nd ed. St. Louis: Saunders; 2015, pp. 1032-1035.
4. Sigrist N. Thoracocentesis. In: Silverstein DC, Hopper K, editors. Small Animal Critical Care Medicine. 2nd ed. St. Louis: Saunders; 2015, pp. 1029-1031.