Magnesium supplementation and the potential association with mortality rates among critically ill non-cardiac patients

OBJECTIVE: Recent literature showed that development of hypomagnesemia is associated with higher mortality. The objective of this study is to evaluate the impact of magnesium supplementation on mortality rates of critically ill patients.

METHODS: All patients admitted to the Intensive Care Unit (ICU) of King Abdul-Aziz Medical City, Riyadh, Saudi Arabia since September 2003 were included. We recorded the demographics data, APACHE score, daily magnesium levels and magnesium supplementation. We collected the data for 30 days or until discharge from ICU. Statistical analysis was performed using the student t-test for continuous data and the Fischers exact test for categorical data. Nothing was carried out to influence the behavior of intensivists in replacing magnesium.

RESULTS: During the study period, 71 patients (45 males and 26 females) were admitted to the ICU, the mean age was 54 ± 18 years for males and 56 ± 19.2 years for females. The mean magnesium level on admission was 0.78 ± 0.2 mmol/L and the majority of the patients were medical admissions. Approximately 39.4% had hypomagnesemia on admission and the overall mortality rate was 31%. In able to standardize the supplementation of magnesium among groups, the daily magnesium supplementation index (DMSI = total magnesium supplement in grams/length of stay in days) was calculated. The mortality rates for DMSI with <1 grm/day (low groups) was statistically significant higher than that of DMSI with >1 grm/day (high group) (43.5% versus 17%, p=0.035). There was no statistically significant differences between magnesium levels of both groups of DMSI except at admission where DMSI group had higher magnesium levels (<1 grm/day).

CONCLUSION: Daily magnesium supplementation index higher than 1 grm/day is associated with lower mortality rates for critically ill patients. This effect was not found to be independent and may be related to severity of illness. Given that magnesium levels were similar between the 2 groups of DMSI at almost all points of the study, magnesium supplementation per se may be beneficial in lowering mortality rates. The exact cause of this effect is unknown. An aggressive magnesium supplementation protocol may be warranted. A larger scale randomized study is necessary to evaluate this effect.