Abstract
Introduction:
The Crescent® is a recently introduced dual lumen cannula by which veno-venous extracorporeal membrane oxygenation (VV ECMO) is delivered. It has a number of features that enhance its ease of placement, pressure-flow dynamics and may reduce catheter-related complication rates.
Methods:
We present the first case series of its kind analysing this device by means of a retrospective observational study of prospectively collected data from the first year of its use in a high volume severe acute respiratory failure centre (Glenfield, UK). We compare complication rates of the Crescent®, with data from the international ELSO database and our own historic centre data and discuss subjective clinician experience of introducing this device.
Results:
Over the first 12 months of its use (23/09/2019–23/09/2020), 54 patients were cannulated using a Crescent® catheter. There were no serious/life-threatening adverse events and a low number of minor cannula-related complications. Subjectively users found it has a number of advantages over other devices and configurations, not captured within current data collection frameworks.
Conclusion:
The Crescent® is a safe and effective device by which to deliver VV ECMO support to patients with severe acute respiratory failure.
Keywords
Introduction
Veno-venous extracorporeal membrane oxygenation (VV ECMO) improves survival in selective patients with reversible severe acute respiratory failure (SARF) when conventional strategies fail. 1 The provision of VV-ECMO involves the drainage of deoxygenated blood from the central venous system, where oxygenation and decarbonatation occurs before its return to the patient at a point prior to entry into the pulmonary circulation. This is traditionally achieved by the use of a drainage cannula inserted into the distal inferior vena cava (IVC) via the femoral vein, and a return cannula inserted into the superior vena cava (SVC) via either the internal jugular vein (IJV), subclavian vein or alternatively the proximal IVC via the other femoral vein. Efficiency of gas exchange due to recirculation, especially at high blood flow rates can be an issue with this configuration.2,3 Dual-lumen single cannula techniques were later introduced and were initially primarily used in babies and infants but rapidly adopted into adult populations4,5 (see Figure 1).6,7
Cannulation strategies for VVECMO.
The Crescent® is a wire-reinforced (prevents kinking and collapse with patient movement) bicaval-right atrial (RA) dual-lumen cannula conventionally inserted via the right IJV. Its namesake refers to the shape of the lumens which allow maximisation of pressure-flow dynamics, delivering consistent blood flow rates at low pressures (see Figure 2). 8 This may reduce both haemolysis and recirculation rates. 9 Its extended and tapered tip, permits ease of insertion without the need for use of a tracheal dilator as with other cannulas 10 whilst minimising cannula migration out of the IVC. A gold ring around the shaft enables its safe securing. Three tantalum markers along the shaft of the cannula, identifying drainage and return sites, tip as well as axial orientation allow easy identification of correct placement under image intensifier. Crescent® cannulae are inserted using a Seldinger percutaneous technique under fluoroscopic guidance. Insertion and positioning is performed under image intensifier and adequate position can be re-confirmed at any time with ease by readily available chest radiography (see Figure 3) or echocardiography.
The Crescent® cannula and internal view showing the crescent shaped lumen.
Chest radiograph demonstrating Crescent® cannula with tantalum markers identifying SVC and IVC drainage (blue arrows) and RA return (red arrow) sites.
In September 2019 the Glenfield Hospital (UK) introduced the Crescent® to its armamentarium of devices for delivering VV ECMO. We present the first ever case series in the literature evaluating this device at an experienced SARF centre. We report quantitative and qualitative data of the complications alongside clinician experiences of introducing this novel device.
Methods
We performed a single centre retrospective analysis of prospectively collected data from all adult (⩾18 years) patients admitted to the Glenfield Adult Intensive Care Unit (GAICU) in England, receiving VV ECMO for SARF cannulated with a Crescent® cannula between 23rd September 2019 (its first use) and 23rd September 2020.
Analysis of our local ECMO database identified all patients fulfilling the inclusion criteria.
The Extracorporeal Life Support Organisation (ELSO) database data was used to identify recognised (or possible) cannula-related complications. Clinical notes were reviewed to clarify unanswered qualitative queries. ECMO intensivists were informally asked to comment on their experiences over the first year of use.
Baseline demographic data including age, gender, weight, body mass index (BMI), primary diagnosis, duration of ECMO support, successful wean from ECMO and survival to decannulation was collected. As was cannula size and site of insertion. We collected data regarding complications potentially related to the cannula, namely; need for repositioning or additional drainage cannulae, haemolysis, cardiac tamponade, bleeding from insertion site and oxygenator failure. Pneumothorax was intentionally excluded due to potential disease specific risk (e.g. more common in COVID19). 11 Furthermore we felt any configuration requiring IJV access (whether single or dual catheter technique) poses the same theoretical risk of pneumothorax related to cannulation. Bleeding from the cannula site, which is often multifactorial, may be less with a single puncture technique and so was included for verification. We compared our data to published international Extracorporeal Life Support Organisation (ELSO) registry data as a baseline comparator of expected/acceptable complication rates.
We express our demographic and clinical data as a median and interquartile range (IQR) for continuous variables and frequency and percentage for categorical variables.
Results
In 1 year, 99 referred SARF patients were admitted to GAICU for consideration of ECMO. Of these, 22 patients did not receive ECMO, 5 required veno-arterial (VA) ECMO, 54 received VV ECMO via a Crescent® cannula and 18 VV ECMO via alternative devices (8 Avalon® and 10 multisite) (see Figure 4).
Referrals to our unit.
In-depth analysis of Crescent data showed a male preponderance (68.5%) with a median age of 48 years and a body mass index (BMI) of 30. The principal diagnosis was COVID-19. The median ECMO run was 9 days with 72.2% successfully separating from VV ECMO and 68.5% surviving discharge from GAICU. Other demographic data can be found in Table 1.
Demographic and outcome data.
Where n is number, IQR is interquartile range, COPD is chronic obstructive pulmonary disease.
As per ELSO data registry, significant bleeding includes that which requires transfusion.
Oxygenator failure may or may not be related to cannula-related issue.
Either discharge to ward or repatriation back to referring centre (ICU).
All insertions were via the right IJV with the majority (57.4%) of insertions using the larger 32Fr cannula. Tendency towards the use of the crescent (and in larger sizes) was more marked in the latter part of the year, suggesting increased up-skilling, confidence in size selection as well as increasing clinician preference for the device. Three patients (5.6%) required cannula repositioning and three patients (5.6%) required an additional drainage cannula. There were no incidences of cardiac tamponade or haemolysis. A single patient had clinically significant bleeding from the cannula site (defined by ELSO as necessitating blood transfusion). Oxygenator failure (cannula and non-cannula related) numbers were low with only two patients (3.7%) experiencing this issue.
Compared with the ELSO registry data (June 2020), we identified lower rates of cannula site bleeding, haemolysis (both unrelated to procedure), cardiac tamponade and oxygenator failure (more nuanced and related to cannula insertion time), with a small increase in cannula related problems (need for repositioning) 12 (Figure 5).
Graphical representation of complications associated with the Crescent® from first year of use at GAICU compared to ELSO registry (adult respiratory data, July 2020). 1
Conclusions
Integration of the Crescent® into clinical practice has been smooth, with minimal additional training (in our experience an estimated 7–10 insertions are required for acquisition of expertise in a clinician already familiar with insertion of other devices). The increased uptake throughout the year has led to it becoming the first-choice cannula for patients requiring VV ECMO at our institution. This is due to advantages previously discussed and the low perceived complication rate. Whilst the numbers in our study seem small, in comparison to other centres, our cannulation rates were well above average. As such, this review of our first year of practice confirms that no serious adverse events occurred as result of the Crescent® cannula insertion, with few minor complications, at rates comparable with that of other cannula configurations. The slight increase in need for repositioning is likely as a result of increased upskilling (need for more precise positioning as compared to single lumen cannula techniques, which improved with time) and increased early patient mobilisation, which the cannula allows. Whilst active mobilisation increases likelihood of cannula movement, we subjectively feel the benefit-risk ratio favours this once a period of stability has been reached in many cases. Clinicians reported other practical benefits such as increased speed of insertion, avoidance of femoral vessels (potential increased risk for infection and thromboses as well as limited mobility), improved flows compared to other dual lumen cannulae and very low recirculation rates. Whilst cannulation is preferred via the RIJV, case reports exist of subclavian vein 13 and left IJV 14 insertion and we echo this experience in our more recent practice. In addition to patient specific factors, availability of radiographic versus echocardiographic support, cost, historical use (centre preference) may influence catheter and configuration choices. However both individual patient and situational needs reinforce the ongoing need for multiple options to be available and an adaptable, patient-centred approach despite an inevitable clinician and centre preference.
Although our numbers are small, this cohort comes from the first year of use with this device, where complication rates are expected to be highest due to lack of familiarity. In summary this is the first case series of its kind reporting complication rates associated with the Crescent® double-lumen cannula. We report no serious/life-threatening adverse events and a low minor complication rate amongst 54 patients over the first year of use in our intensive care unit (Glenfield AICU, UK).
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
