RESUMO
Vasoplegia is considered as a key factor responsible for the death of patients with septic shock, due to persistent and irreversible hypotension. The latter associated with vascular hyporeactivity to vasoconstrictors is a significant independent prognostic factor of mortality in severe sepsis. Loss of control of the vascular tone occurs through the complex, multifactorial mechanism and implicates deeply disrupted balance between vasoconstrictors and vasodilators. The aim of this review is to discuss in detail the recent suggested alternative mechanisms of vasoplegia in severe sepsis: Overproduction of nitric oxide (NO) by activation of inducible form of nitric oxide synthase (iNOS); up-regulation of prostacyclin (PG12); vasopressin deficiency; significantly elevated levels of circulating endothelin; increased concentrations of vasodilator peptides such as adrenomedulin (AM) and calcitonin gene-related peptide (CGRP); oxidative stress inducing endothelial dysfunction and vascular hyporeactivity to vasoconstrictors; inactivation of catecholamines by oxidation; over-activation of ATP-sensitive potassium channels (KATP channels) during septic shock and their involvement in vascular dysfunction. The review also discusses some therapeutic approaches based on pathogenetic mechanisms of severe sepsis and their efficacy in treatment of patients with septic shock. The loss of vascular tone control occurs through the complex, multifactorial mechanism and implicates deeply disrupted balance between vasoconstrictors and vasodilators in the pathogenesis of septic shock. Overproduction of nitric oxide (NO) by the inducible form of nitric oxide synthase (iNOS); up-regulation of prostacyclin (PG12); vasopressin deficiency; elevated levels of circulating endothelin; increased concentrations of vasodilator peptides such as adrenomedulin (AM) and calcitonin gene-related peptide (CGRP); oxidative stress inducing endothelial dysfunction and vascular hyporeactivity to vasoconstrictors; inactivation of catecholamines by oxidation; over-activation of ATP-sensitive potassium channels (KATP channels) and their involvement in vascular dysfunction - all these factors combined together lead to steady refractory shock with the lethal outcome in patients.
