Influence of twenty-five per cent human serum albumin on total and ionized calcium concentrations in vivo

Abstract

. The purpose of this investigation was to determine the interaction (if any) between exogenous 25% albumin administration (100 ml given over < 30 min) and calcium concentrations in patients, all but one of whom were in an intensive care unit. There were no significant differences in the ionized calcium concentrations obtained before, at the end and 6 h after the administration of albumin (1.09 ± 0.23, 1.06 ± 0.22, 1.06 ± 0.21 mmol/l, respectively). Similarly, there were no significant differences in the total calcium concentrations between these same time periods (2.03 ± 0.18, 2.05 ± 0.20, 2.08 ± 0.23 mmol/l, respectively). In patients receiving infusions of 25% albumin, it appears that circulating calcium concentrations are well regulated by homeostatic mechanisms. Albumin infusions had no effect on calcium concentrations, although it is possible that temporary changes of questionable clinical importance may have occurred between measurement periods.

Background:

. The purpose of this investigation was to determine the interaction (if any) between exogenous 25% albumin administration (100 ml given over < 30 min) and calcium concentrations in patients, all but one of whom were in an intensive care unit.

Results:

There were no significant differences in the ionized calcium concentrations obtained before, at the end and 6 h after the administration of albumin (1.09 ± 0.23, 1.06 ± 0.22, 1.06 ± 0.21 mmol/l, respectively). Similarly, there were no significant differences in the total calcium concentrations between these same time periods (2.03 ± 0.18, 2.05 ± 0.20, 2.08 ± 0.23 mmol/l, respectively).

Conclusions:

In patients receiving infusions of 25% albumin, it appears that circulating calcium concentrations are well regulated by homeostatic mechanisms. Albumin infusions had no effect on calcium concentrations, although it is possible that temporary changes of questionable clinical importance may have occurred between measurement periods.

Introduction

]. Theoretically, the addition of exogenous albumin to the bloodstream would increase the number of binding sites for calcium, which could result in a lower ionized calcium concentration. Total calcium concentrations would not be expected to change as a result of this increased binding by albumin, assuming there were no concomitant changes in calcium distribution or elimination.

might be corrected by compensatory mechanisms involving parathyroid hormone, calcitriol, and calcitonin. How quickly and to what degree this compensation is effective has not yet been elucidated.

]. Therefore, fluctuations in ionized calcium concentrations due to exogenous albumin administration could place these patients at risk for symptomatic hypocalcemia. Although clinical features of hypocalcemia are often non-specific and may go undetected in milder forms, signs and symptoms of deficiency may include tetany, muscle weakness, parasthesias, adverse cardiovascular effects, bronchospasm, and confusion.

. Because high concentrations of albumin infused as a bolus are more likely to result in a precipitous drop in ionized calcium concentrations, this study only included patients receiving infusions of 25% albumin 100 ml (25 g), over a period of less than 30 min.

Statistical analysis

< 0.05. Data are expressed as means ± standard deviation, unless otherwise noted.

Results

contains the patient demographics and the patients' primary problems. The majority of enroled patients received the albumin infusions within 5days of major surgery.

). There was no obvious pattern to the changes that did occur in calcium concentrations. The largest decrease in ionized calcium concentrations that occurred in any of the patients was 0.23 mmol/l (1.06 mmol/l before and 0.83 mmol/l at the end of albumin infusion). The 6-h ionized calcium concentration in this patient was 0.96 mmol/l. In contrast, another patient had a baseline ionized calcium concentration of 0.91 mmol/l, which then increased to 0.93 and 0.99 mmol/l at the end of albumin infusion and 6 h after, respectively.

There were no changes detected in other parameters that might have influenced calcium concentrations. For example, there were no substantial changes in other laboratory variables such as phosphorus and magnesium. Although all but one of the patients was in the intensive care unit during the study, there were no acute events during the 6-h monitoring period that could potentially have interfered with the calcium measurements.

), although the increase was not statistically significant.

Ionized calcium concentrations before and after albumin infusions.

Total calcium concentrations before and after albumin infusions.

Albumin concentrations before and after albumin infusions.

Demographics and primary problems of patients in prospective study

Pt, patient.

Discussion

] found that 62% of prescriptions for albumin were inappropriate, with an associated cost of US$124939. In addition to efficacy and cost, adverse effects should be considered when discussing therapeutic options.

].

], the most important question not answered by this investigation was whether normal in-vivo compensatory mechanisms (ie stimulation of parathyroid hormone secretion, increased production of vitamin D precursors, decreased calcitonin production) would offset the changes induced by albumin.

Our study was unable to find any effects of 25% albumin on either total or ionized calcium concentrations in patients, all but one of whom were in the intensive care unit. It is possible that larger doses of albumin may have an effect on ionized calcium concentrations, although the lack of substantial changes at these concentrations in the present study argues against this. Another study limitation was the relatively small number of enrolled patients and their associated illnesses. It is possible that significant changes in ionized calcium concentrations would be found if more patients were studied, but again the minor fluctuations in concentrations noted in this investigation seem to make this unlikely. We did not exclude patients on the basis of disease states that might affect calcium concentrations, unless the disease state directly affected the body's ability to compensate for hypocalcemia as might occur in patients with parathyroid or renal dysfunction. Despite differing primary diagnoses and secondary problems such as infection that commonly occur in intensive care unit patients, both the total and ionized calcium concentrations were remarkably stable over the measurement period.

]. It is possible that 100 ml infusions of 25% solution given very rapidly (eg < 5 min) might cause clinically important decreases in ionized calcium concentrations. Furthermore, if a more intensive blood sampling strategy had been used in this investigation, it is possible that substantial decreases in ionized calcium concentrations may have been observed. These hypotheses require further investigation. With regard to this study, it is suspected that transient decreases in the ionized calcium concentrations found with more intensive blood sampling would be of questionable clinical importance.

] have had disparate results.

In conclusion, this investigation did not find a significant interaction between 25% albumin administration and calcium concentrations. It is possible that significant decreases in ionized calcium concentrations could occur in populations not studied, and that these decreases could be clinically important in patients predisposed to suboptimal compensatory responses (eg in neonates). Such populations require further study. In adult patients, intensive monitoring of calcium concentrations does not appear warranted during administration of human serum albumin in doses of 25 g or less.

Keywords

• albumin
• albumin administration
• calcium concentrations
• adverse effects