OBJECTIVES
The aim of the study is to compare a technique of pump-controlled retrograde trial off (PCRTO) to insertion of an arterio-venous (AV) bridge to conduct a trial from venoarterial extracorporeal membrane oxygenation (VA ECMO).
METHODS
We studied all patients who were weaned from VA ECMO using either PCRTO or AV bridging from November 2014 to April 2018. Demographic data, indications for ECMO, duration of ECMO, duration of trial period off ECMO and survival were compared between the 2 groups.
RESULTS
Seventy-nine patients were placed on VA ECMO from November 2014 to April 2018, of whom, 51 (65%) patients met the study inclusion criteria: 31 (61%) patients who had a trial period from VA ECMO using PCRTO and 20 (39%) patients who were weaned using an AV bridge. The indications for ECMO included cardiac (n = 16 and 11, respectively) and non-cardiac aetiologies (n = 15 and 9, respectively). There was 1 death in each group. The duration of the trial off VA ECMO was significantly shorter in the PCRTO group (median = 88.0 vs 196.6 min, P < 0.001). There were 2 conversions from PCRTO to AV bridging during the trial period off ECMO (2.9-kg neonate following a Norwood procedure and 2.2-kg patient following repair of ectopia cordis).
CONCLUSIONS
PCRTO is a safe, simple and reproducible approach for enabling a trial period while preserving the circuit during weaning from VA ECMO. In our study, the duration of the trial period off VA ECMO was significantly shorter in the PCRTO group. PCRTO avoids manipulation of the ECMO circuit, provides a ‘stress test’ to evaluate cardiorespiratory reserve during the trial period off ECMO, is applicable for a wide variety of cardiac and non-cardiac indications and facilitates multiple attempts at weaning from ECMO.
Pump controlled retrograde flow trial off is an easy to use and easily reversible technique to assess patient readiness for separation from extracorporeal membrane oxygenation. Given pump controlled retrograde flow trial off can easily be stopped and-in our experience-is not associated with complications, it lowers the threshold to attempt coming off extracorporeal membrane oxygenation and facilitates accurate assessment of whether a patient will need further ongoing extracorporeal membrane oxygenation support.
A retrospective study was performed to describe the impact of merging two pediatric intensive care units on the overall and neurocognitive outcomes of children who required extracorporeal cardiopulmonary resuscitation (ECPR). Results from three cohorts were compared: 2008 to 2014: premerge, 2014 to 2017: initial time period postmerge, and 2018 to 2019: established merge. Survival to hospital discharge (and with good neurological outcome) was of 68% (61%), 46% (36%), and 79% (71%), respectively, for the three time periods. Merging two hospitals resulted in a nonsignificant trend toward temporary worse outcomes in pediatric patients requiring ECPR.
We read Ling's report with interest and commend the authors for creating more awareness that pump-controlled retrograde trial off (PCRTO) is an elegant and feasible way to assess readiness for decannulation. 1 The authors describe that PCRTO leads to a reduction in afterload on the left ventricle (LV) and an increase in volume load on the right ventricle. While this is correct, PCRTO is more complex than this: assuming a fixed VO 2 , the LV has to perform additional work to drive the retrograde flow through the ECMO circuit while maintaining systemic DO 2 . PCRTO almost serves as a cardiac "stress test".While Westrope described PCRTO for the first time in a small series of children, we have demonstrated the use and limitations of PCRTO in a larger cohort of children. 2,3 We showed that the use of PCRTO depends on the minimum permitted flow through the oxygenator and the patient weight. In small infants, the cardiac output might be insufficient to drive the retrograde flow through the circuit, particularly if clinicians aim for an oxygenator flow of greater 100 ml/min (pediatric oxygenator). Equally, in adults, a patient with impaired LV function having to drive (up to) 500 ml/min of oxygenator flow may experience insufficient systemic oxygen delivery. In our patients, we saw a trend to a blood pressure increase and heart rate decrease after decannulation (and removal of the effective left to right shunt), reflecting the reversal of the "stress test" setup during PCRTO.Clinicians should be aware of the limitations of PCRTO, monitor end-organ function carefully during PCRTO, limit the duration of PCRTO and consider lower oxygenator flows (for a limited period of time) than mandated by the manufacturers during the time of PCRTO.
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