Historically, it was felt that a platelet count below 50,000 or an INR>1.5 was a contraindication to thoracentesis because of an increased bleeding risk. These were arbitrary cut-offs that have since been challenged with newer kits and the use of ultrasound-guided thoracentesis. Previously, preprocedure transfusions with platelets or FFP were commonly performed prior to a thoracentesis for platelet levels below 50K or elevated INR levels >1.5. Recent data demonstrate that ultrasound-guided thoracentesis can be safely performed without preprocedure blood transfusions with moderate thrombocytopenia (platelet >25K) and/or INR<3 provided platelets function properly (concomitant use of thienopyridines like clopidogrel, ticagrelor or prasugrel or presence of uremia can cause platelet dysfunction).
The data to support this are based on the following studies. A prospective study of about 9100 thoracenteses over 12 years found that patients with an INR of 1.5-2.9 or platelets of 20,000 – 49,000/µL experienced rates of bleeding complications of only 0.5%.1 Another study of over 700 thoracenteses found that the overall risk of hemorrhage during thoracentesis in the setting of moderate coagulopathy (defined as an INR of 1.5 – 3 or platelets of 25,000-50,000/µL), was only 0.4%.2In 1 retrospective study of more than 1000 procedures, no differences in hemorrhagic events were noted in patients with bleeding diatheses that received prophylactic fresh frozen plasma or platelets vs. those who did not.3
Based on these data, it is now felt that an ultrasound-guided thoracentesis can be safely performed with a platelet count as low as 25K and/or an INR<3 provided no qualitative platelet dysfunction. To minimize the risk of bleeding, it is also advisable to perform the thoracentesis at least 6 cm lateral to the spine and use the ultrasound color mode to assure the intercostal artery is unprotected in the proposed thoracentesis insertion spot.4