From the Guidelines
If your ionized calcium is low but your total serum calcium is normal, you should administer calcium chloride to correct hypocalcaemia, as recommended by the European guideline on management of major bleeding and coagulopathy following trauma: sixth edition 1. This approach is based on the latest evidence from 2023, which emphasizes the importance of maintaining ionized calcium levels within the normal range, especially during massive transfusion.
- The guideline recommends monitoring and maintaining ionized calcium levels within the normal range following major trauma and during massive transfusion 1.
- It also recommends the administration of calcium chloride to correct hypocalcaemia, with a Grade 1C recommendation 1.
- Ionized calcium is the physiologically active form of calcium in your blood, so a low level can affect nerve and muscle function even when total calcium appears normal.
- Additional testing may be necessary to determine the underlying cause of the low ionized calcium level, including checking parathyroid hormone (PTH), vitamin D levels, kidney function, and magnesium levels.
- Treatment depends on the underlying cause and symptoms, but correcting the low ionized calcium level with calcium chloride is a crucial step in management, as supported by the highest quality and most recent evidence 1.
From the FDA Drug Label
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action Intravenous administration of calcium gluconate increases serum ionized calcium level. Calcium gluconate dissociates into ionized calcium in plasma. Ionized calcium and gluconate are normal constituents of body fluids.
The answer to the question of what to do about a low ionized calcium but normal serum is to consider administering calcium gluconate (IV), as it increases serum ionized calcium level.
- Key points:
- Low ionized calcium can be addressed by increasing serum ionized calcium level
- Calcium gluconate (IV) is a potential treatment option 2
From the Research
Low Ionized Calcium but Normal Serum Calcium
- A low ionized calcium level with a normal serum calcium level can be an indication of hypocalcemia, which is a common condition in hospitalized patients, occurring in 15% to 88% of cases 3.
- The measurement of ionized calcium is crucial in determining the true serum calcium status, especially in critically ill patients, as total plasma calcium concentration can be affected by hypoalbuminemia and disorders of acid-base balance 4.
- Hypocalcemia can be caused by various factors, including vitamin D deficiency, and symptomatic patients with calcium levels less than 7.6 mg/dL should be treated with intravenous calcium gluconate, while also addressing concomitant magnesium deficiency 5.
- In patients with acute renal failure, ionized serum calcium levels can be affected by the type of renal replacement therapy used, with continuous veno-venous hemodiafiltration (CVVHDF) more likely to lower serum calcium concentrations, while intermittent hemodialysis (IHD) is more likely to induce hypercalcemia 6.
- The use of albumin-corrected calcium (cCa) is recommended over ionized calcium (iCa) in hemodialysis patients, but the choice of albumin assay can produce differing results, and uncorrected serum calcium may have a better predictive value when using the BCP assay 7.