Introduction
Propofol (Diprivan®, AstraZeneca) is a reliable sedative frequently used in critically ill patients (pts). The modified formulation contains 0.005% disodium edetate (EDTA) as an antimicrobial agent. EDTA is also a chelating agent and may impact calcium balance; therefore, three clinical trials were performed in which ionized calcium (Ca2+) and parathyroid hormone (PTH) levels were assessed. PTH plays a major role in calcium homeostasis but is generally not considered to be a stress hormone.
Purpose
Evaluate PTH levels in critically ill pts sedated with propofol or propofol EDTA.
Methods
Serum intact PTH, total Mg, Ca2+, and total Ca were measured in 212 pts in 3 randomized, double-blind, controlled trials (85 medical ICU, 37 renal impaired ICU, and 90 cardiac surgical pts).
Results
See Table. For the medical ICU pts, baseline PTH levels were unexpectedly increased above the normal range (unrelated to propofol and Ca2+). Baseline PTH levels in pts undergoing elective cardiac surgery were normal. Pts with impaired renal function had high PTH values presumably secondary to hyperparathyroidism.
Table.
Intact PTH levels in pg/ml (mean ± SEM; normal range: 9–46 pg/ml)
| Medical ICU pts | Renal impaired pts | Cardiac surgery pts | ||||
|---|---|---|---|---|---|---|
| 24 h after | 48 h after | 1 h after | ||||
| Baseline | sedation | Baseline | sedation | Baseline | extubation | |
| Propofol | 84.9 ± 15.1 | 69.2 ± 19.2 | 126.3 ± 23.6 | 119.9 ± 44.7 | 40.6 ± 2.4 | 62.3 ± 5.3 |
| (n = 26) | (n = 22) | (n = 19) | (n = 15) | (n = 46) | (n = 46) | |
| Propofol EDTA | 92.0 ± 18.6 | 72.1 ± 26.4 | 234.4 ± 52.2 | 141.1 ± 33.6 | 40.0 ± 2.9 | 67.6 ± 5.5 |
| (n = 21) | (n = 14) | (n = 18) | (n = 13) | (n = 44) | (n = 44) | |
Conclusion
PTH levels were elevated at baseline in critically ill medical ICU pts without renal failure. This finding was not related to propofol or low Ca2+ levels. The explanation is unknown, but perhaps PTH should be reconsidered as being a stress hormone. Patients with impaired renal function had high PTH values, presumably secondary to decreased Ca2+levels and/or hyperparathyroidism.