Associated Veterinary Specialists - Advanced Veterinary Care - St. Louis, MO
AVS Veterinary News

How to perform aThoracentesis

My first case of a pleural effusion was during my internship at the Animal Medical Center in New York City. It was an Afghan Hound and you guessed it, she had a chylothorax. I took her from the exam room back to the surgery prep area to do a thoracentesis and lucky for me, Dr. John Parks, one of the senior surgeons was standing there. I started to clip the animal’s ventral thorax and he looked at me and said “What are you doing?” His tone of voice was such that he had rarely encountered such a stupid intern. I replied that I was going to do a thoracentesis. He said “You’re doing it wrong.” I said “OK how do I do it?” “Move out of the way and I’ll show you” The best thoracentesis catheter is a bovine teat cannula. The end is blunt but sharp enough to go through the intercostal muscles. It also has side holes. You also need an extension set, a 3-way valve and a large syringe. The secret is to perform the thoracentesis with the animal on its side, with the needle penetrating dorsally on the chest wall at about the 8th interspace. The needle should be just slightly below the angle of the rib. After entry into the chest, aspirate all the fluid you can then roll the animal onto its back and continue aspirating as it goes from its side to its back. A trough is formed between the spine and the rib and there isn’t anything in the trough you can hit with the needle except the fluid. You can almost completely empty the chest with this method. Sometimes you will have to do both sides. Now, I know you are thinking that fluid gravitates downward and therefore this is a ridiculous method! But, you will find that if there is free fluid in the pleural space, the lungs collapse fairly uniformly and finding fluid on the upside is much easier than on the downside. You also will not hit the heart or the internal thoracic artery with this method. I perform a thoracentesis on a cat after they have spent 5 to 10 minutes in the induction chamber receiving only oxygen before the Sevo is turned on. I often do dogs with local anesthesia only but it depends on the dog’s nature. Remember you are much more likely to kill a pet by fighting with it than anesthetizing it!! After you perform the thoracentesis, have a full fluid analysis performed. You removed the fluid not only to relieve the respiratory distress but also to find out why it is there. Post thoracentesis radiographs should be taken which will be much easier to evaluate since the fluid has been removed.