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Depressor effects of ionized calcium infusion in essential hypertension
Insights
An acute increase in serum ionized calcium in hypertensive patients caused a significant drop in blood pressure and heart rate. This suggests calcium may play a role in regulating vascular tone.
Area of Science:
- Cardiovascular Physiology
- Nephrology
- Pharmacology
Background:
- Hypertension is a prevalent cardiovascular condition.
- Serum ionized calcium levels can influence cardiovascular function.
- The acute effects of calcium infusion on circulation in hypertensive individuals require further elucidation.
Purpose of the Study:
- To assess the circulatory effects of an acute increase in serum ionized calcium.
- To investigate the impact on mean arterial blood pressure and heart rate in patients with hypertension.
Main Methods:
- 27 patients with mild to moderate hypertension were enrolled.
- Calcium gluconate was infused intravenously over three minutes.
- Circulatory variables, including blood pressure and heart rate, were monitored before, during, and after infusion.
Main Results:
- Serum ionized calcium levels significantly increased post-infusion.
- A significant decrease in mean arterial blood pressure and heart rate was observed.
- A strong correlation was found between the change in ionized calcium and blood pressure reduction.
Conclusions:
- Acute elevation of serum ionized calcium induces a hypotensive and bradycardic effect in hypertensive patients.
- Potential mechanisms include enhanced membrane stabilization of vascular smooth muscle cells.
- Further research is warranted to explore the therapeutic potential of modulating calcium levels in hypertension.
Abstract:
The circulatory effects of an acute increase in serum ionized calcium were assessed in 27 patients with mild to moderate hypertension. Following a control period of fifteen minutes with confirmed circulatory variables, 1,375 mg calcium gluconate was infused over three minutes. Systemic mean arterial blood pressure and heart rate were recorded before, at one-minute intervals during, and for five minutes following the infusion. There was a brief increase of serum ionized calcium concentration (from 1.28 +/- 0.06 mmol/liter to 1.42 +/- 0.07 mmol/liter; p less than 0.001) maximum by one minute after infusion with return toward control by a further four minutes. This was accompanied by a significantly decreased mean arterial blood pressure (from 117 +/- 8 mmHg to 110 +/- 9 mmHg at three minutes; p less than 0.05) and heart rate (from 70 +/- 11 min-1 to 63 +/- 10 min-1 at three minutes; p less than 0.01). There was a significant correlation between the change in ionized calcium and that of the systemic arterial blood pressure (r = 0.68; p less than 0.01). No major side effects were recorded. The blood pressure reduction may theoretically be related to increased membrane stabilization of vascular smooth muscle cells, the acute increase in extracellular ionized calcium impairing calcium ions influx.