The role of histamine release in shock

More than 80 years after its discovery and nearly 70 years after its first being implicated in the mechanism of shock, the precise role of histamine (H) in the pathophysiology of the condition remains to be determined. The prevailing view over the decades has been that H is a noxious mediator contributing to the fatal outcome of shock. An adequate assessment of its role has long been hampered by the lack of a sufficiently sensitive and specific method for the measurement of H and by deficiencies of design in many studies. We now know that H is released in all types of shock. In low-output, high-resistance states, as in hypovolemic and cardiogenic shock, its effect (contrary to previous notions) appears to be beneficial, probably through the inhibition of excessive vasoconstriction and through a positive inotropic effect. In endotoxin shock the results are conflicting, but seem to indicate that H is not a lethal factor. In human septic shock, patients who died had higher H levels. The role of H release in the various forms of shock, both experimental and human, clearly needs an adequate, critical reevaluation, in carefully designed and executed studies using satisfactory methodology.