An ionized calcium regulated calcium clamp technique in man

Area of Science:

• Clinical Biochemistry
• Pharmacology
• Human Physiology

Background:

• Maintaining stable ionized calcium levels is crucial for various physiological processes.
• Previous methods for calcium infusion lacked precision in achieving steady-state whole blood ionized calcium (WB-Ca++) levels.
• Accurate control of WB-Ca++ is essential for therapeutic interventions and research.

Purpose of the Study:

• To describe and evaluate a new calcium clamp technique for precise control of WB-Ca++ in humans.
• To assess the safety and efficacy of achieving and maintaining a steady-state WB-Ca++ level.
• To determine the time course for reaching and sustaining target WB-Ca++ concentrations.

Main Methods:

• Development of a calcium clamp technique involving frequent WB-Ca++ monitoring.
• Administration of calcium chloride infusions at a standardized rate (17.55 mmol Ca++ per hour).
• Inclusion of normocalcemic patients (n=23), including postmenopausal females with osteoporosis, premenopausal females, and males.

Main Results:

• Hypercalcemia was achieved within 7-15 minutes, with target WB-Ca++ levels (1.45 mmol/l) reached in 15-35 minutes.
• Steady-state WB-Ca++ levels were maintained for 120 minutes with minimal individual variation (≤0.04 mmol/l).
• Low coefficients of variation (≤0.04) for WB-Ca++ during steady state indicated remarkable constancy of the ionized calcium fraction.

Conclusions:

• The described calcium clamp technique is safe and effective for achieving and maintaining precise WB-Ca++ levels in humans.
• This method offers a reliable approach for clinical situations requiring controlled ionized calcium concentrations.
• The technique's ability to maintain a steady state WB-Ca++ opens possibilities for new therapeutic strategies.