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The effect of graded calcium infusions on rhythmic blood pressure oscillations in normal man
M Munakata1, Y Imai, K Mizunashi
1Second Department of Internal Medicine, Tohoku University, School of Medicine, Sendai, Japan.
Insights
Calcium levels influence blood pressure rhythms. This study shows that increasing plasma calcium concentrations (hypercalcemia) alters blood pressure oscillations, specifically affecting the Mayer wave, a marker of sympathetic vascular tone.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
- Biomedical Engineering
Background:
- Blood pressure exhibits complex rhythmic oscillations.
- The role of calcium in regulating these oscillations is not fully understood.
- Sympathetic vascular tone influences blood pressure variability.
Purpose of the Study:
- To investigate the effect of graded hypercalcemia on blood pressure oscillations in humans.
- To determine if calcium modulates specific frequency bands of blood pressure variability.
- To assess the impact of calcium on the Mayer wave, a marker of sympathetic activity.
Main Methods:
- Six healthy subjects underwent continuous blood pressure monitoring using Finapres.
- Sequential 1-hour infusions of calcium gluconate were administered at increasing doses (1.5, 3.0, 4.5 mg/kg/h).
- Plasma ionized calcium concentrations and power spectrum analysis of blood pressure oscillations (low, mid, and high frequencies) were performed.
Main Results:
- Infusion led to a significant increase in plasma ionized calcium levels.
- The power spectrum of diastolic blood pressure's mid-frequency band (Mayer wave) initially decreased then significantly increased with higher calcium doses.
- The high-frequency power spectrum of systolic blood pressure decreased significantly after the initial dose.
Conclusions:
- Graded hypercalcemia significantly affects blood pressure oscillations in humans.
- Calcium plays a role in modulating the amplitude of the Mayer wave.
- These findings suggest calcium influences sympathetic vascular tone regulation.
Abstract:
This study was designed to determine whether calcium contributes to the regulation of rhythmic oscillations in blood pressure. Six normal subjects received sequential 1-h infusions of calcium gluconate (1.5, 3.0 and 4.5 mg calcium/kg/h) during continuous blood pressure (Finapres) monitoring. The plasma ionized calcium ([Ca2+]) concentration increased from 4.6 +/- 0.07 mg/dl to 5.97 +/- 0.20 mg/dl (p < 0.01) with infusion. The mid-frequency (0.07-0.14 Hz, Mayer wave) power spectrum of diastolic blood pressure was depressed slightly following the first dose but increased significantly following the final dose (p < 0.05). The high-frequency (0.15-0.40 Hz) power spectrum of systolic blood pressure decreased following the first dose (p < 0.05) and subsequently remained low. The low-frequency (0.02-0.6 Hz) power spectrum was not affected. These results demonstrate that graded hypercalcaemia affects blood pressure oscillations in man. Our data suggest that the amplitude of the Mayer wave, a clinical marker of sympathetic vascular tone, is modulated in part by calcium.