Page 3 of 3Pearls & Pitfalls for Ultrasound-Guided Paracentesis
1. Position the Patient: After the patient empties his or her urinary bladder, have them lie supine with the head of the bed elevated 45-60°. This angle allows the bowel to float up and the ascites to collect in the lower abdomen.
2. Find the Best Fluid Pocket: Using the curvilinear probe, check both lower quadrants and the midline to find the largest pocket of anechoic (black) ascites fluid. DO NOT reposition the patient after this step until the procedure has been completed. Fluid pockets may move with patient repositioning. Any free flowing fluid within the peritoneal fluid will appear black. Urine, liquid stool, inflammatory fluid and unclotted blood may all appear similar to ascites so correlate your scan results clinically.
3. Do the Tap: Most practitioners will localize a fluid pocket with ultrasound and then complete the procedure in a “blind” fashion. You can use ultrasound to localize the best fluid pocket and then mark the puncture site with a marker before you prep and drape the patient. Alternatively, you can prep your probe in a sterile fashion and complete the procedure with real-time ultrasound guidance. If you choose the latter, you may want to have an assistant hold the ultrasound probe for you so that you have use of both of your hands.
4. Practice Makes Perfect: With bedside ultrasound, there is no substitute for experience. The more ultrasounds you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is. An image library of normal and abnormal ultrasounds helps immensely, and EPM can help. Just go to EPMonthly.com and click the ultrasound library link within the Real-Time-Readings department.
5. Caution should be taken removing too much fluid too quickly. Some patients with as little as 1.5 L removed too quickly have experienced hypotension.
Brady Pregerson manages a free online EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more information visit ERPocketBooks.com
Teresa Wu is the EM Ultrasound Director and Co-Director for Simulation Based Training for the Maricopa Emergency Medicine Program in Phoenix, Arizona.