Why do the kidneys and salt balance matter so much for long-term blood pressure?

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This abstract discusses the contribution of Guyton’s large mathematical computer model of circulatory control. Published in 1972, the model by Guyton and colleagues challenged the prevailing views of how blood pressure and cardiac output were controlled. At the time, the widely accepted view was that the heart controlled cardiac output and peripheral resistance controlled arterial blood pressure.

Guyton and colleagues incorporated two empirically demonstrated concepts into their mathematical model: blood flow autoregulation and the pressure–natriuresis relationship, which links blood pressure with sodium excretion. This enabled them to develop a number of revolutionary concepts.

The circulatory model was particularly important for exploring the link between blood pressure and sodium balance and for demonstrating the overriding importance of renal salt and water balance in setting long-term blood pressure. In both the model and experimental data, any long-lasting imbalance between salt intake and salt excretion progressively changes the degree of filling of the vascular system, producing parallel changes in blood pressure. In turn, changes in blood pressure alter sodium excretion, opposing the initial salt imbalance.

Although Guyton’s model does not include the most recent cardiovascular discoveries, its concepts of basic cardiovascular functioning can provide a well-built foundation for developing new, large, integrative cardiovascular models.