Vasopressors for treating shock.

Shock must be treated by correcting the cause for any treatment of hypotension or shock as such is only an adjunctive measure; but the hemodynamic manifestations also need treatment. Vasopressors are helpful and effective under the right circumstances. Unless the blood volume is normal the use of drugs that block the sympathetic nervous system (e.g. phenoxybenxamine) can be extremely hazardous and hasten death. However the effect of adrenergic blocking drugs in endotoxic shock and other types of toxic shock is still to be determined; use of such drugs should be considered experimental until the results have been studied more extensively. Clinically the most common forms of vascular shock are associated with blood loss myocardial infarction and endotoxemia. Characteristic hemodynamics of each situation are presented tabularly and the physicians need to understand the differences is emphasized. The pharmacology of vasopressors relating primarily to hemodynamic considerations and the response to vasopressors when severe reduction in blood pressure is associated with the shock syndrome is discussed. Drugs that stimulate the adrenergic receptors in the heart and blood vessels with the exception of isoproteronol are commonly referred to as vasopressors. The adrenergic stimulators may be classified into 3 groups: alpha (phenylephrine hydrochloride) beta (epinephrine) and alpha-beta (l-norepinephrine). Because alpha stimulators do not usually increase cardiac output alpha-beta and beta-adrenergic stimulators are generally the most useful for treating shock. Routine use of adrenergic stimulators with the exclusion of other therapies however is generally unwarranted.