RESUMO
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.
RESUMO
BACKGROUND: Peripheral venous cannulation is one of the most common procedures in medicine. A larger cannula allows higher rates of fluid to be provided if needed in a deteriorating patient; however, it is also perceived that larger-gauge cannula placement is associated with increased pain and procedural difficulty. OBJECTIVE: This study aimed to compare the pain and procedural difficulty experienced during insertion between 18-gauge (18G) and 20-gauge (20G) cannulas. METHODS: We conducted a single-blinded, randomized controlled trial on adult patients who required peripheral IV cannulation within a tertiary hospital emergency department between April and October 2018. Patients were randomized to either the 18G or 20G cannula group. The primary outcomes of the study-pain experienced by patients and procedural difficulties experienced by clinical staff-were recorded on two separate 10-cm visual analog scales. Other outcomes include first-attempt success rate, operator designation, complications, and the intent and actual use of the IV cannula were documented on preformatted questionnaires. RESULTS: Data from 178 patients were included in the analysis. Eighty-nine patients were allocated to each cannula group. There were no statistically or clinically significant differences between mean pain score (0.23; 95% CI 0.56-1.02; p = 0.5662) and mean procedural difficulty score (0.12; 95% CI 0.66-0.93; p = 0.7396). between the two groups. There was no difference in first-attempt success rate (73 of 89 vs. 75 of 89; p = 0.1288), complications (2 of 89 vs. 1 of 89) between the 20G group and 18G group, respectively. CONCLUSIONS: There was no significant difference between the 18G or 20G cannula for either pain experienced by patients or procedural difficulty experienced by clinicians.