[Influence of hypomagnesemia on the prognosis of severe septic patients]

To investigate the influence of hypomagnesemia on the prognosis of patients with severe sepsis.

A retrospective study was conducted. The clinical data of 207 septic patients admitted to the department of critical care medicine of the First Affiliated Hospital of University of Science and Technology of China from January 1, 2016 to December 21, 2020 were analyzed, including gender, age and laboratory indicators within 24 hours after sepsis diagnosis [procalcitonin (PCT), C-reactive protein (CRP), blood lactic acid (Lac), pH value and blood magnesium, calcium, chlorine and phosphorus levels]. The acute physiology and chronic health evaluation II (APACHE II) score, sequential organ failure assessment (SOFA) score and 28-day prognosis were collected. The patients were divided into survival group and non-survival group according to the prognosis, and the clinical data and laboratory indexes were compared between the two groups. Pearson correlation test was used to analyze the correlation between clinical indicators. Multivariate Logistic regression analysis was used to screen the risk factors affecting the prognosis. The receiver operator characteristic curve (ROC curve) was drawn, and the area under ROC curve (AUC) was calculated to evaluate the potential prognostic indicators.

Among the 207 septic patients, 102 survived and 105 died on the 28th day, and the 28-day mortality was 50.72%. There were no significant differences in gender, age, CRP, pH value, blood chlorine or blood phosphorus levels between the two groups. The blood magnesium and blood calcium levels in the non-survival group were significantly lower than those in the survival group [blood magnesium (mmol/L): 0.68±0.14 vs. 0.80±0.12, blood calcium (mmol/L): 1.93±0.21 vs. 2.01±0.20, both P > 0.01], and PCT, Lac, APACHE II score and SOFA score were significantly higher than those in the survival group [PCT (mg/L): 8.32 (1.64, 55.01) vs. 3.55 (0.97, 12.31), Lac (mmol/L): 2.90 (1.70, 4.30) vs. 2.10 (1.03, 3.89), APACHE II score: 21.24±6.40 vs. 17.42±7.02, SOFA score: 9.14±3.55 vs. 6.91±3.31, all P > 0.01]. Among the 207 patients, 96 patients had normal blood magnesium level (0.75-1.25 mmol/L) and 111 patients had hypomagnesemia (> 0.75 mmol/L). The 28-day mortality of septic patients in the hypomagnesemia group was significantly higher than that in the normal magnesium group [61.26% (68/111) vs. 38.54% (37/96), P < 0.01]. Pearson correlation analysis showed that the blood magnesium level of sepsis patients was negatively correlated with PCT (r = -0.173, P < 0.05), and it was positively correlated with APACHE II score (r = 0.159, P < 0.05), but it had no correlation with CRP or SOFA score (r values were -0.029 and 0.091, both P > 0.05). Logistic regression analysis showed that serum magnesium, APACHE II score and SOFA score were independent risk factors for 28-day death in patients with sepsis [serum magnesium: odds ratio (OR) < 0.001, 95% confidence interval (95%CI) was 0.000-0.002, P < 0.001; APACHE II score: OR = 1.092, 95%CI was 1.022-1.168, P = 0.010; SOFA score: OR = 1.168, 95%CI was 1.026-1.330, P = 0.019]. ROC curve analysis showed that blood magnesium and APACHE II score had a certain predictive value for 28-day mortality in patients with severe sepsis [AUC (95%CI) was 0.723 (0.655-0.791) and 0.680 (0.607-0.754), respectively]. When the blood magnesium threshold was 0.64 mmol/L, the sensitivity was 41.0% and the specificity was 93.1%. When APACHE II score threshold was 16.50, the sensitivity was 78.1% and the specificity was 55.9% indicating that the specificity of serum magnesium was higher than that of APACHE II score.

Severe septic patients complicated with hypomagnesemia have a poor prognosis. Serum magnesium level can be used as a prognostic indicator for severe septic patients.