Vasopressor Resistance clinical trials

Evaluation of the Effect of Dexmedetomidine on Phenylephrine Response During Refractory Septic Shock

Septic shock is common in patients admitted to intensive care and hospital mortality occurs in close to 50% of these patients. In half of the cases, death occurs within the first 72 hours in a context of multiple organ failure that does not respond to conventional therapies, particularly circulatory therapies, despite increasing doses of catecholamines. Vasopressor resistance in septic patients defines refractory septic shock. In one study (Conrad et al. 2015), the increase in blood pressure observed with an infusion of increasing doses of phenylephrine (dose-response curve) made it possible to quickly and clearly identify patients resistant to vasopressors at a high risk of death by refractory shock (ROC AUC 0.92). This resistance is due in particular to a downregulation of α1 adrenergic receptors, linked to sympathetic hyper activation associated with septic shock. To date, there is no validated therapy in this situation. However, experimental data have shown that the administration of α2 agonists, usually used for their sedative (dexmedetomidine) or anti-hypertensive (clonidine) effect, normalizes sympathetic activity towards basal values. In animals, α2 agonists restore the sensitivity of alpha1 adrenergic receptors, resulting in improved vasopressor sensitivity and survival. In humans, a beneficial effect on mortality was suggested in the first trial testing dexmedetomidine in septic patients in 2017. This effect was observed especially in the most severe patients, suggesting a restoration of sensitivity to vasopressors. The hypothesis is that the administration of dexmedetomidine in patients in refractory septic shock may improve response to phenylephrine and decrease resistance to vasopressors. This pilot study could lay the foundation for a randomized controlled trial.