Suspension syndrome: a potentially fatal vagally mediated circulatory collapse - an experimental randomized crossover trial
Dal Cappello T
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Suspension syndrome describes a potentially life-threatening event during passive suspension on a rope. The pathophysiological mechanisms are not fully understood and the treatment is unknown. We aimed to elucidate the pathophysiology and to give treatment recommendations. In this experimental randomized crossover trial, 20 healthy volunteers were passively suspended in a harness for a maximum of 60 minutes, with and without prior climbing. During the tests, heart rate (HR), blood pressure (BP), and stroke volume were monitored and left ventricular diameters were determined by transthoracic echocardiography. Venous pooling was assessed by measuring the diameter of the superficial femoral vein (SFV) with ultrasound and lower leg tissue oxygenation (StO2) with near infrared spectroscopy (NIRS) and localized bioelectrical impedance. Signs and symptoms of presyncope were recorded. Twelve (30%) out of 40 tests were prematurely interrupted due to presyncopal symptoms after a mean time of 44.7 minutes (minimum 13.4, maximum 59.7). An increase in SFV diameter and a decrease in StO2 indicate venous pooling during suspension. In addition, the capacitive resistance (Xc) of the cells decreased. However, HR and BP did not change in participants without presyncope, but suddenly decreased in participants with presyncope. All symptoms resolved and values returned to normal within 5 minutes with participants in supine position. During passive suspension in a harness, venous pooling takes place in lower legs. Yet, no effect on macrocirculation was observed and a vagal mechanism seems to lead to a presyncope. Persons suspended on a rope should be rescued and put into a supine position as soon as possible.