Flow capabilities of arterial and drainage cannulae during venoarterial extracorporeal membrane oxygenation: A simulation model.

BACKGROUND: Large cannulae can increase cannula-related complications during venoarterial extracorporeal membrane oxygenation (VA ECMO). Conversely, the ability for small cannulae to provide adequate support is poorly understood. Therefore, we aimed to evaluate a range of cannula sizes and VA ECMO flow rates in a simulated patient under various disease states. METHODS: Arterial cannulae sizes between 13 and 21 Fr and drainage cannula sizes between 21 and 25 Fr were tested in a VA ECMO circuit connected to a mock circulation loop simulating a patient with severe left ventricular failure. Systemic and pulmonary hypertension, physiologically normal, and hypotension were simulated by varying systemic and pulmonary vascular resistances (SVR and PVR, respectively). All cannula combinations were evaluated against all combinations of SVR, PVR, and VA ECMO flow rates. RESULTS: A 15 Fr arterial cannula combined with a 21 Fr drainage cannula could provide >4 L/min of total flow and a mean arterial pressure of 81.1 mmHg. Changes in SVR produced marked changes to all measured parameters, while changes to PVR had minimal effect. Larger drainage cannulae only increased maximum circuit flow rates when combined with larger arterial cannulae. CONCLUSION: Smaller cannulae and lower flow rates could sufficiently support the simulated patient under various disease states. We found arterial cannula size and SVR to be key factors in determining the flow-delivering capabilities for any given VA ECMO circuit. Overall, our results challenge the notion that larger cannulae and high flows must be used to achieve adequate ECMO support.

Smaller Return Cannula in Venoarterial Extracorporeal Membrane Oxygenation Does Not Increase Hemolysis: A Single-Center, Cohort Study.

The aim of this study was to explore the association between arterial return cannula diameter and hemolysis during peripheral VA ECMO. We identified 158 adult patients who received peripheral VA ECMO at our institution from the national ECMO database (EXCEL) between January 2019 and July 2021. We classified patients into a small cannula group (15 Fr diameter, n = 45) and a large cannula group (≥17 Fr diameter, n = 113), comparing incidences of clinical hemolysis and plasma free hemoglobin ( pf Hb). Moderate hemolysis is defined as having pf Hb 0.05-0.10 g/L and severe hemolysis as having pf Hb >0.10 g/L sustained for at least two consecutive readings or leading to a circuit change. There were no significant differences in rates of moderate hemolysis between small and large cannula groups (1 vs . 6; p = 0.39) and severe hemolysis (0 vs . 3; p = 0.27), nor was the pf Hb level significantly different at 4 hours (0.086 ± 0.096 vs . 0.112 ± 0.145 g/L; p = 0.58) and at 24 hours (0.042 ± 0.033 vs . 0.051 ± 0.069 g/L; p = 0.99). There were no increased rates of hemolysis when comparing small versus large arterial return cannula diameter in peripheral VA ECMO.

A retrospective observational study of sarcopenia and outcomes in critically ill patients.

Frailty assessment in patients admitted to intensive care is often limited using traditional clinical frailty assessment tools. Opportunistic use of contemporary computed tomography (CT) can provide an objective estimate of low skeletal muscle mass (sarcopenia) as a proxy for frailty. The aim of this study was to establish the prevalence of sarcopenia in an Australian intensive care unit (ICU) population and to examine the relationship between sarcopenia and clinical outcomes. We undertook a single centre retrospective study of 1085 adult patients admitted to a single ICU over 12 months. Patients with a contemporary CT scan including the L3 vertebral body were included. Patients were categorised as sarcopenic or non-sarcopenic using previously published data. A total of 279 patients with a mean age of 67 years had an eligible CT scan; 163 (58%) were male. Higher 30-day mortality was associated with the use of CRRT (continuous renal replacement therapy) during the ICU admission (OR 6.84, P < 0.001) and also associated with lower cross-sectional muscle area (odds ratio (OR) 0.98, P = 0.004). Sarcopenia was found to be highly prevalent in this particular Australian ICU population (68%) and associated with older age (68 versus 55 years, P < 0.001), lower body mass index (27 versus 32 kg m-2, P < 0.001), more comorbidities (3 versus 2, P = 0.009), and longer stays in hospital (279 versus 223 h, P = 0.043). As a continuous predictor, lumbar muscle mass was associated with 30-day mortality with and without adjusting for other covariates.