Veno-venous ECMO: a synopsis of nine key potential challenges, considerations, and controversies.

BACKGROUND: Following the 2009 H1N1 Influenza pandemic, extracorporeal membrane oxygenation (ECMO) emerged as a viable alternative in selected, severe cases of ARDS. Acute Respiratory Distress Syndrome (ARDS) is a major public health problem. Average medical costs for ARDS survivors on an annual basis are multiple times those dedicated to a healthy individual. Advances in medical and ventilatory management of severe lung injury and ARDS have improved outcomes in some patients, but these advances fail to consistently "rescue" a significant proportion of those affected. DISCUSSION: Here we present a synopsis of the challenges, considerations, and potential controversies regarding veno-venous ECMO that will be of benefit to anesthesiologists, surgeons, and intensivists, especially those newly confronted with care of the ECMO patient. We outline a number of points related to ECMO, particularly regarding cannulation, pump/oxygenator design, anticoagulation, and intravascular fluid management of patients. We then address these challenges/considerations/controversies in the context of their potential future implications on clinical approaches to ECMO patients, focusing on the development and advancement of standardized ECMO clinical practices. SUMMARY: Since the 2009 H1N1 pandemic ECMO has gained a wider acceptance. There are challenges that still must be overcome. Further investigations of the benefits and effects of ECMO need to be undertaken in order to facilitate the implementation of this technology on a larger scale.

Persistent 2-for-1 Atrioventricular Node Anterograde Conduction During a Supraventricular Tachycardia.

We present a case of persistent dual AV node conduction during AV node reentry tachycardia as a new clinical manifestation of 2-for-1 AV node conduction. The interpretation of the complex physiology ponders the possibility of an accessory pathway mediated atrioventricular reentry existing with more ventricular than atrial events.

Diagnostic utility of early premature ventricular complexes in differentiating atrioventricular reentrant and atrioventricular nodal reentrant tachycardias.

BACKGROUND: His-refractory premature ventricular complexes perturbing a supraventricular tachycardia (SVT) establish the presence of an accessory pathway (AP). Earlier premature ventricular complexes (ErPVCs) may perturb SVTs but are considered nondiagnostic. OBJECTIVE: The purpose of this study was to test the hypothesis that an ErPVC will always show a difference >35 ms in its advancement of the next atrial activation during atrioventricular nodal reentrant tachycardia (AVNRT). During atrioventricular reentrant tachycardia (AVRT), a PVC delivered close to the circuit can result in greater advancement of atrial activation due to retrograde conduction via an AP. Thus, an AP response, defined as ErPVC (H1S2) advancing the subsequent atrial activation (A1-A2) more than this minimum difference (A1A2 ≤ H1S2+35 ms), establishes the presence of an AP. METHODS: Sixty-five consecutive patients with SVT were retrospectively evaluated. ErPVCs were defined when the ventricular pacing stimulus was >35 ms ahead of the His during tachycardia. RESULTS: Among the 65 cases, 43 were AVNRT and 22 AVRT. Fourteen AVRT cases had an AP response with a mean H1S2+35 ms of 336 ± 58 ms and A1A2 of 309 ± 51ms. No AVNRT cases had an AP response. The specificity of an AP response to ErPVC in predicting AVRT was 100%. CONCLUSION: An AP response to PVCs (A1A2 ≤ H1S2+35 ms) is 100% specific for the presence of an AP.