Strategies for appropriate positioning and repositioning the Avalon ECMO cannula in a 17-year-old with left hepatic vein malposition

INTRODUCTION

Extracorporeal membrane oxygenation (ECMO) is a well-recognized therapy in children with refractory hypoxia. Different cannulas have been used with reported complications with placement, such as cardiac perforation, and multiple reports focusing on avoiding this. However, strategies to avoid hepatic vein cannulation and reposition when it occurs are not well described.

CASE REPORT

Here, we report a case where a 27-Fr Avalon bicaval double lumen cannula in the left hepatic vein was successfully repositioning using serial chest X-rays (CXR) and transthoracic echocardiography (TTE) in a 17-year-old female.

DISCUSSION

While venovenous (VV) ECMO is preferred by many, placement of the Avalon catheter, a cannula available for VV ECMO, may be challenging due to migration or positioning issues. Specific techniques of wire and catheter advancement as well as confirming wire position in the infra-hepatic inferior vena cava can help ensure appropriate positioning while avoiding hepatic vein cannulation and enabling successful repositioning when it occurs.

CONCLUSION

Wire position in the infra-hepatic inferior vena cava helps ensure safe and appropriate Avalon cannula position and placement. The Avalon cannula can be successfully repositioned from the left hepatic vein by retracting the cannula, reinserting the wire and introducer together, and then manipulation techniques using serial CXR and TTE.

Cervical spine flexion-extension radiography versus magnetic resonance imaging in pediatric patients following blunt traumatic injury

Background

In pediatric trauma patients, 60-80% of spinal cord injuries involve the cervical vertebrae. While the American College of Radiology offers guidelines for best imaging practices in the setting of acute pediatric trauma, there is a lack of uniformity in imaging-decision protocols across institutions. MRI has been shown to demonstrate high sensitivity for both bony and ligamentous injuries while also avoiding unnecessary radiation exposure in the pediatric patient population. However, the efficacy of flexion-extension (FE) radiography following initial MRI has not been evaluated in children. Our hypothesis is that FE radiography conducted following an initial MRI does not contribute significant diagnostic information or reduce time to cervical collar removal and thus can be removed from institutional protocols in order to avoid unnecessary testing and reduce pediatric radiation exposure.

Methods

Trauma data were collected for pediatric patients presenting with suspected acute cervical spine injury from 2014 to 2021. A total of 108 patients were subdivided into 41 patients who received "MRI Only" and 67 patients who received both "MRI and FE" diagnostic cervical spine imaging. Chi-square testing and t-tests were performed to determine differences between MRI and FE radiographic detection rates of bony and ligamentous injuries in the subgroups.

Results

In patients for whom FE did not find any injury, MRI detected bony and ligamentous injuries in 9/63 and 12/65 cases, respectively. In 3/21 (14.3%) cases in which MRI detected a bony and/or ligamentous injury and FE did not, patients eventually required surgical intervention for c-spine stabilization. No patients required surgical fixation when FE radiography showed an abnormality and MRI was normal. Addition of follow-up FE radiography after initial MRI did not have a significant effect on overall hospital length of stay (MRI Only vs MRI+FE: 9.2±12.0 days vs 8.6±13.5 days, p=0.816) or on rates of collar removal at discharge or greater than 48 hours after imaging (MRI Only vs MRI+FE: 41.5% vs 56.7%, p=0.124).

Conclusions

FE radiography following initial MRI did not have a significant effect on reducing time to cervical collar removal or overall hospital length of stay. In addition, in 3 of 6 cases (50.0%) in which surgical fixation was required, MRI detected ligamentous and/or bony injury while FE radiography was normal.

Level of Evidence

This study contributes Level 2b scientific evidence consistent with a well-designed cohort or case-control analytic study.