Haemodynamic determinants of the arterial blood pressure rise during growth in conscious puppies

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Abstract
The circulatory events determining the physiological rise of arterial blood pressure (BP) from infantile to adult levels were investigated in five unanaesthetised healthy puppies. Monthly haemodynamic studies were performed during the development of the animals from the age of one month (infancy) to the age of 9 months (maturity). During the follow-up, body weight (W) increased by 730%, heart rate (HR), cardiac output (CO/W), plasma volume/W (PV/W) and mean central venous pressure (CVP), decreased respectively by 58%, 44%, 27%, 75%. Stroke volume/W (SV/W), mean arterial pressure (MAP), and total peripheral vascular resistance (TPR) increased respectively 37%, 91%, 308%. MAP almost doubled its initial value in spite of the drop in CO /W indicating the presence of arteriolar constriction during growth. Upon the dogs reaching maturity the following sequence of events based on their different rate of change (from the highest to the lowest) was found: W increase → TRP rise → MAP rise → CO/W drop. Significant correlations were found between W increase and TPR and MAP rise, and between MAP rise and CO/W reduction. We thus conclude that TRP increase is the haemodynamic factor responsible for MAP rise during growth. We advance the hypothesis that the growth of the tissues and reduction of their metabolic needs represents the natural stimulus determining precapillary constriction and consequently a remodelling of the circulatory dynamics during development.

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