Critical illness is associated with elevated parathyroid hormone

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)

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.