based review

Shock may be defined as an im-pairment of the normal rela-tionship between oxygen de-mand and oxygen supply. As a consequence, there are detrimental alter-ations in tissue perfusion, resulting in a reduction in the delivery of oxygen and other nutrients to tissue beds and caus-ing cellular and then organ dysfunction. In hypovolemic, cardiogenic, and ob-structive forms of shock, the primary de-fect is a fall in cardiac output, leading to hypoperfusion, hypotension, and anaero-bic metabolism. In septic shock, however, there is a complex interaction between pathologic vasodilatation, relative and ab-solute hypovolemia, direct myocardial depression, and altered blood flow distri-bution, which occur as a consequence of the inflammatory response to infection. Even after the restoration of circulating volume, maldistribution of a normal or increased cardiac output typically persists as a consequence of microvascular abnor-malities. In addition, cellular and organ injury also occur as direct consequences of the inflammatory response in sepsis and as a consequence of hypoperfusion. Making recommendations about the choice of individual vasopressor agents in septic shock is made difficult by the pau-city of controlled trials and by the clinical reality that agents are frequently used in combination. In modern practice, norepi-nephrine and dopamine are the vasopres-sors used most frequently, although do-pamine has more marked inotropic effects. The relatively small inotropic ef-fect of norepinephrine, and concerns about regional blood flow, mean that it is frequently used in combination with do-butamine. Epinephrine may also be used as an alternative and, again, combines vasopressor and inotropic effects. Phen-ylephrine, which has virtually only vaso-pressor actions, is also sometimes used. Dopamine and epinephrine in particular have important metabolic and endocrine effects that may complicate their use and be potentially detrimental. This review of the literature enables recommendations to be established and graded according to the strength of the available evidence