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

Background The present study explores serum parathyroid hormone (PTH) and b lood ionized calcium (Ca2+) levels in relation to the severity of disease a nd mortality in the intensive care unit (ICU). Methods In a pilot study, 37 consecutive critically ill patients admitted t o the ICU were studied with determinations of serum PTH and total serum cal cium within the first 24 h. In a following prospective study, patients suff ering from sepsis (n = 13) or subjected to major surgery (n = 13) were inve stigated daily for 1 week with determinations of serum PTH and ionized calc ium (Ca2+). Severity of disease was assessed by the APACHE II score and hos pital 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 sig nificant relationship to the APACHE II score (r = 0.39, P < 0.05). In the p rospective study, serum PTH was elevated in 69% of the patients in both gro ups at inclusion, and 6 days later 87% of the septic and 37% of the surgery patients still showed elevated levels. Hypocalcaemia was more commonly see n in the septic patients [mean Ca2+ 1.03 +/- 0.08 (SD) mmol L-1] than in th e 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 (mea n 161 +/- 51 vs. 79 +/- 51 ng L-1, P < 0.005). Conclusion Hypocalcaemia and increased levels of PTH were common findings i n critically ill patients. These alterations in calcium homeostasis were re lated to the severity of disease and increased PTH levels were associated w ith a poor outcome.