Western Journal of Emergency Medicine: Integrating Emergency Care with Population Health

Introduction: Computed tomography pulmonary angiography (CTPA) is the test of choice for diagnosis of pulmonary embolism (PE) in the emergency department (ED), but this test may be indeterminate for technical reasons such as inadequate contrast filling of the pulmonary arteries.  Many hospitals have requirements for intravenous (IV) catheter size or location for CTPAs to reduce the chances of inadequate filling, but there is a lack of clinical data to support these requirements. The objective of this study was to determine if a certain size or location of IV catheter used for contrast for CTPA is associated with an increased chance of an indeterminate CTPA.

Methods: This was a retrospective chart review of patients who underwent CTPA in the emergency department.  A CTPA was considered indeterminate if the radiology report indicated it was inadequate to exclude a pulmonary embolism.  The reason for the study being indeterminate, and the size and location of the IV catheter were abstracted. The rate of inadequate contrast filling of the pulmonary vasculature was calculated and compared for various IV catheter sizes and locations.  In particular, 20-gauge or larger IV catheters in the antecubital fossa or forearm were compared to all other sizes and locations.

Results: A total of 19.3% of the 1500 CTPA reports reviewed met our criteria as indeterminate, and 51.6% of those were due to inadequate filling.  Patients with a 20-gauge IV catheter or larger placed in the antecubital fossa or forearm had inadequate filling 9.2% of the time compared to 13.2% for patients who had smaller IVs or IVs in other locations (difference:  4.0% [95% CI -1.7% to 9.7%]).  There were also no statistically significant differences in the rates of inadequate filling when data were further stratified by IV catheter location and size.

Conclusion: We did not detect any statistically significant differences in the rate of inadequate contrast filling based on IV catheter locations or sizes.  While small differences not detected in this study may exist, it seems prudent to proceed with CTPA in patients with difficult IV access who need emergent imaging even if they have a small or distally located IV.