EMedHome's Clinical Pearl
Emergency physicians are well familiar with the requirements for IV catheter size and location for pulmonary embolism CTPA studies to reduce the chance of inadequate filling, but clinical data are lacking to support these requirements. (West J Emerg Med. 2019;20:244; http://bit.ly/2X8YDVk.)
A recent retrospective chart review of 1500 patients who underwent CTPA for PE evaluated if the size or location of the IV catheter used for contrast was associated with an increased chance of suboptimal CTPA. (West J Emerg Med. 2019;20:244; http://bit.ly/2X8YDVk.) That occurred nearly 20 percent of the time in this study, more than half of which were from inadequate filling of the pulmonary vasculature. The study did not detect any statistically significant differences in the rate of inadequate filling when data were stratified by IV catheter location and size.
Patients with a 20-gauge or larger IV catheter placed in the antecubital fossa or forearm had inadequate filling nine percent of the time compared with 13 percent for patients who had smaller IVs or IVs in other locations. Even patients with ideally located 18-gauge IV catheters had inadequate filling of the pulmonary vasculature about one in 10 times, suggesting that factors other than the catheter size and location affect the quality of the contrast bolus.
The sample size for patients with 22-gauge IVs was small, but 10 of 13 patients had adequate filling of the pulmonary vasculature. The authors concluded that CTPA should not be delayed in a potentially unstable patient with difficult IV access just because the IV size or location does not meet policy. It is reasonable to proceed regardless of the IV size or location if the line is tested with a saline flush with no resistance before contrast injection and no other IV access sites can be easily obtained.
Some data suggest that even intraosseous lines can be used for CT angiography. A tibial intraosseous line has been used for successful administration of contrast for a CTPA study, with excellent opacification of the pulmonary arteries, and a humeral intraosseous line has been successfully used for a CT angiogram of the chest and abdomen. (West J Emerg Med. 2019;20:244; http://bit.ly/2X8YDVk; J Emerg Med. 2013;45:182; Emerg Radiol. 2017;24:105.)
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