1989 Volume 26 Issue 4 Pages 353-360
The circadian rhythm of the heart rate was assessed using 24 hour electrocardiographic recordings in 18 hospitalized elderly patients with wasting diseases receiving total parenteral nutrition. The nutrient solutions were administered at doses ranging from 360 to 1640kcal/day. To determine if the heart rate fluctuates rhythmically with a circadian period, the mean hourly heart rate on 24hour electrocardiographic recordings was used to fit cosine curves by the statistical technique of least squares, and three parameters of the rhythmdesignated the mesor, amplitude, and acrophase-were estimated. The cosine curves fitted with a P value of 0.01 or less in all patients before and after insertion of central venous catheters. The mesor represented the rhythmadjusted mean of the heart rate. The mesor increased significantly with increase in the energy infusion rate (p<0.01). The amplitude values were derived from one half of the total diurnal variation of heart rate and the acrophase indicated the time when heart rates were at their peak above the mean. Neither amplitude nor acrophase changed significantly with increase in the energy infusion rate. Furthermore, neigher norepinephrine nor epinephrine plasma levels changed with nutrient administration. There were no significant changes in thyroid hormone concentrations. There was a significant positive correlation between mesor changes and rectal temperature with increase in the energy infusion rate (r=0.76, p<0.01). In severely malnourished subjects, changes in the level of feeding can profoundly affect cardiac functions and thermogenic response.
