Influencing factors and clinical significance of severe hypocalcemia in patients with extremely severe burns in early stage

Objective To analyze the influencing factors and clinical significance of severe hypocalcemia in patients with extremely severe burns in early stage. Methods Clinical data of 142 patients with extremely severe burns admitted to our wards from January 2010 to July 2015, conforming to the study criteria, were retrospectively analyzed. (1) The incidence of hypocalcemia and severe hypocalcemia on admission were calculated. (2) Patients were divided into the male group (n=113) and the female group (n=29) according to gender. The levels of serum calcium of patients whose age more than 55 years old and less than or equal to 55 years old in the two groups were compared with t test. (3) Patients were divided into severe hypocalcemia group (n=52) and non-severe hypocalcemia group (n=90) according to the level of serum calcium on admission. The data including gender, age, flame burn, total burn area, inhalation injury, admission time, the pH value, and the albumin level of patients on admission between two groups were compared with chi-square test or t test. Indexes with P<0.1 between two groups were selected, and multivariate logistic regression analysis was conducted to screen the influencing factors of severe hypocalcemia in patients with extremely severe burns in early stage. (4) According to the prognosis, patients were divided into survival group (n=112) and non-survival group (n=30). The data including gender, age, flame burn, total burn area, inhalation injury, admission time, the level of serum calcium, the pH value, and the albumin level of patients on admission between two groups were compared with chi-square test or t test. Indexes with P<0.1 between two groups were selected, and multivariate Cox regression analysis was conducted to screen the influencing factors of prognosis of patients with extremely severe burns. Results (1) The incidence of hypocalcemia on admission was 97.2% (138/142), and patients diagnosed as severe hypocalcemia accounted for 36.6% (52/142). (2) In the male group, the level of serum calcium of patients with age more than 55 years old was (1.84±0.19) mmol/L, which was close to (1.88±0.21) mmol/L of patients with age less than or equal to 55 years old within the same group and (1.96±0.13) mmol/L of patients with age more than 55 years old in the female group (t=0.833, 1.560, P>0.05). In the female group, the level of serum calcium of patients with age less than or equal to 55 years old was (1.78±0.19) mmol/L, which was significantly lower than that of patients with age less than or equal to 55 years old in the male group and that of patients with age more than 55 years old in the female group (t=-2.197, -2.472, P<0.05). (3) Compared with those of patients in severe hypocalcemia group, the total burn area and the proportion of inhalation injury of patients in non-severe hypocalcemia group were obviously smaller (t=2.379, χ² =13.410, P<0.05 or P<0.01), and the admission time was obviously earlier (t=2.675, P<0.01), while the albumin level was obviously higher (t=-6.163, P<0.01). There were no statistically significant differences between patients of the two groups in gender, flame burn, age, and the pH value on admission (χ²=1.869, 2.850, t=-0.578, 0.645, P>0.05). Multivariate logistic regression analysis showed that only the albumin level on admission was the independent influencing factor of severe hypocalcemia in patients with extremely severe burns (with odds ratio 1.179, 95% confidence interval 1.092-1.273, P<0.01). (4) Compared with those of patients in non-survival group, the total burn area and the proportion of inhalation injury in survival group were smaller (t=-5.515, χ²=27.573, P<0.05 or P<0.01), while the pH value and the albumin level on admission were higher (t=2.208, 3.321, P<0.05 or P<0.01). There were no statistically significant differences between patients of the two groups in gender, flame burn, age, admission time, and the level of serum calcium on admission (χ²=0.198, 2.545, t=-1.316, -1.397, 1.857, P>0.05). Multivariate Cox regression analysis showed that total burn area and inhalation injury were the independent risk factors to predict prognosis of patients with extremely severe burns (with relative risk 1.066 and 4.081, 95% confidence interval 1.023-1.110 and 1.144-14.559, P<0.05 or P<0.01), but the pH value and levels of albumin and serum calcium were not independent risk factors to predict prognosis of patients with extremely severe burns (with relative risk 0.003, 1.025, and 0.634, 95% confidence interval <0.001-1.183, 0.956-1.099, and 0.055-7.321, P>0.05). Conclusions The level of serum calcium of the majority of patients with extremely severe burns on admission is decreasing significantly, especially the female patients less than or equal to 55 years old. Compared with non-severe hypocalcemia patients, patients with severe hypocalcemia are with larger total burn area, higher proportion of inhalation injury, later admission time, and lower albumin level on admission. However, only the albumin level on admission is the independent influencing factor of severe hypocalcemia in patients with extremely severe burns. And the level of serum calcium on admission can not predict the prognosis of patients with extremely severe burns.