Popliteal artery cannulation as a saviour during prone positioning

The cannulation of the peripheral artery is a prerequisite for invasive blood pressure monitoring and repeated arterial blood gas sampling. Radial artery is commonly used site for inserting an arterial cannula. Many times, either during the change of posture or during prone ventilation, the arterial cannula gets displaced, and it is challenging to reinsert the arterial cannula in the lateral or prone position. In such circumstances, an alternative site of arterial cannulation needs to be looked into; we report a case in which the popliteal artery was used for arterial cannulation while the patient was in a prone position.

An experimental model of veno-venous arterial extracorporeal membrane oxygenation

Introduction: Veno-venous arterial extracorporeal membrane oxygenation is a hybrid-modality of extracorporeal membrane oxygenation combining veno-venous and veno-arterial extracorporeal membrane oxygenation. It may be applied to patients with both respiratory and cardio-circulatory failure. Aim: To describe a computational spreadsheet regarding an ex vivo experimental model of veno-venous arterial extracorporeal membrane oxygenation to determine the return of cannula pairs in a single pump–driven circuit. Methods: We developed an ex vivo model of veno-venous arterial extracorporeal membrane oxygenation with a single pump and two outflow cannulas, and a glucose solution was used to mimic the features of blood. We maintained a fixed aortic impedance and physiological pulmonary resistance. Both flow and pressure data were collected while testing different pairs of outflow cannulas. Six simulations of different cannula pairs were performed, and data were analysed by a custom-made spreadsheet, which was able to predict the flow partition at different flow levels. Results: In all simulations, the flow in the arterial cannula gradually increased differently depending on the cannula pair. The best cannula pair was a 19-Fr/18-cm arterial with a 17-Fr/50-cm venous cannula, where we observed an equal flow split and acceptable flow into the arterial cannula at a lower flow rate of 4 L/min. Conclusion: Our computational spreadsheet identifies the suitable cannula pairing set for correctly splitting the outlet blood flow into the arterial and venous return cannulas in a veno-venous arterial extracorporeal membrane oxygenation configuration without the use of external throttles. Several limitations were reported regarding fixed aortic impedance, central venous pressure and the types of cannulas tested; therefore, further studies are mandatory to confirm our findings

A simulation study of left ventricular decompression using a double lumen arterial cannula prototype during a veno-arterial extracorporeal membrane oxygenation

Background: Veno-arterial extracorporeal membrane oxygenation can be vital to support patients in severe or rapidly progressing cardiogenic shock. In cases of left ventricular distension, left ventricular decompression during veno-arterial extracorporeal membrane oxygenation may be a crucial factor influencing the patient outcome. Application of a double lumen arterial cannula for a left ventricular unloading is an alternative, straightforward method for left ventricular decompression during extracorporeal membrane oxygenation in a veno-arterial configuration. Objectives: The purpose of this article is to use a mathematical model of the human adult cardiovascular system to analyze the left ventricular function of a patient in cardiogenic shock supported by veno-arterial extracorporeal membrane oxygenation with and without the application of left ventricular unloading using a novel double lumen arterial cannula. Methods: A lumped model of cardiovascular system hydraulics has been coupled with models of non-pulsatile veno-arterial extracorporeal membrane oxygenation, a standard venous cannula, and a drainage lumen of a double lumen arterial cannula. Cardiogenic shock has been induced by decreasing left ventricular contractility to 10% of baseline normal value. Results: The simulation results indicate that applying double lumen arterial cannula during veno-arterial extracorporeal membrane oxygenation is associated with reduction of left ventricular end-systolic volume, end-diastolic volume, end-systolic pressure, and end-diastolic pressure. Conclusions: A double lumen arterial cannula is a viable alternative less invasive method for left ventricular decompression during veno-arterial extracorporeal membrane oxygenation. However, to allow for satisfactory extracorporeal membrane oxygenation flow, the cannula design has to be revisited.

Quantitative assessment of peripheral limb perfusion using a modified distal arterial cannula in venoarterial ECMO settings

In cases of severe cardiopulmonary deterioration, quick establishment of venoarterial extracorporeal membrane oxygenation (ECMO) represents a support modality. After successful arterial peripheral cannulation, a certain grade of peripheral limb malperfusion is a fairly common phenomenon. Detection of peripheral malperfusion is vital, since it can result in compartment syndrome or even loss of the affected limb. To prevent or resolve emerging lower limb ischaemia, a newly designed perfusion catheter is placed into the superficial femoral artery, distal to the arterial cannula via ECMO. The aim of our study was to evaluate flow and haemodynamic characteristics of this novel distal limb perfusion cannula for ECMO therapy and present these important findings for the first time. The distal perfusion cannula blood flow increases in linear correlation with ECMO blood flow The variability of distal perfusion cannula blood flow with a 15 Fr cannula ranges between 160 ± 0.40 mL min−1 at 1.5 L min−1 ECMO flow rate and 480 ± 80 mL min−1 at 5.0 L min−1 ECMO blood flow, respectively. Comparatively, the 17-Fr-sized cannula performs on a scale of 140 ± 20 to 390 ± 60 mL distal perfusion cannula blood flow at 1.5-5.0 L min−1 ECMO blood flow, respectively. The quantitative assessment of the distal perfusion cannula blood flow has revealed that distal perfusion cannula blood flow can measure up to 10% of the ECMO blood flow. Furthermore, it has been also well demonstrated that the novel distal perfusion cannula is sufficient to compensate peripheral limb ischaemia.