Parathyroid hormone and ionized calcium levels are related to the severity of illness and survival in critically ill patients.

BACKGROUND: The present study explores serum parathyroid hormone (PTH) and blood ionized calcium (Ca2+) levels in relation to the severity of disease and mortality in the intensive care unit (ICU).

METHODS: In a pilot study, 37 consecutive critically ill patients admitted to the ICU were studied with determinations of serum PTH and total serum calcium within the first 24 h. In a following prospective study, patients suffering from sepsis (n = 13) or subjected to major surgery (n = 13) were investigated daily for 1 week with determinations of serum PTH and ionized calcium (Ca2+). Severity of disease was assessed by the APACHE II score and hospital mortality was recorded.

RESULTS: In the pilot study, serum PTH levels were elevated (> 55 ng L-1) in 38% of the patients and were not related to serum calcium but showed a significant relationship to the APACHE II score (r = 0.39, P < 0.05). In the prospective study, serum PTH was elevated in 69% of the patients in both groups at inclusion, and 6 days later 87% of the septic and 37% of the surgery patients still showed elevated levels. Hypocalcaemia was more commonly seen in the septic patients [mean Ca2+ 1.03 +/- 0.08 (SD) mmol L-1] than in the surgical patients (1.14 +/- 0.06 mmol L-1) at inclusion. Both PTH and Ca2+ levels were significantly related to the APACHE II score (r = 0.46, P < 0.03, and r = -0.54, P < 0.009, respectively). Furthermore, PTH levels were significantly increased in non-survivors (n = 5) compared with survivors (mean 161 +/- 51 vs. 79 +/- 51 ng L-1, P < 0.005).

CONCLUSION: Hypocalcaemia and increased levels of PTH were common findings in critically ill patients. These alterations in calcium homeostasis were related to the severity of disease and increased PTH levels were associated with a poor outcome.