Hypomagnesemia in critically ill medical patients.

BACKGROUND: Hypomagnesemia is an important but underdiagnosed electrolyte abnormality in critically ill patients. There are many studies to find the prevalence of hypomagnesemia and its effects on mortality and morbidity in these patients. Most of these studies have been carried out in intensive care units caring for patients with medical and surgical conditions and postoperative patients or those in respiratory intensive care unit, or critically ill cancer patients. This study was carried out on patients admitted to the medical acute care unit in a major tertiary care hospital.

AIMS AND OBJECTIVES: To study serum magnesium levels in critically ill patients and to correlate serum magnesium levels with patient outcome considering the following parameters: length of stay in MICU, need for ventilatory support, duration of ventilatory support, APACHE score and mortality. To identify the primary medical conditions associated with abnormalities of serum magnesium. To identify the factors predisposing or contributing to hypomagnesemia in critically ill patients admitted in a medical intensive care unit. To detect other electrolyte abnormalities associated with hypomagnesemia, if any.

RESULTS: On admission to MICU 52% patients had hypomagnesemia, 7% patients had hypermagnesemia and 41% patients had normomagnesemia. The patients with hypomagnesemia had higher mortality rate (57.7% vs 31.7%), more frequent need for ventilatory support (73% vs 53%), longer duration of mechanical ventilation (4.27 vs 2.15 days), more frequently had sepsis (38% vs 19%), hypocalcemia (69% vs 50%) and hypoalbuminemia (80.76% vs 70.8%). Patients with diabetes mellitus had hypomagnesemia more frequently (27% vs 14%). The duration of stay in the MICU or APACHE score on admission did not vary in patients with low or normal magnesium.

CONCLUSIONS: There was a high prevalence of hypomagnesemia in the critically ill patients. Hypomagnesemia was associated with a higher mortality rate in critically ill patients. The need for ventilatory support was significantly higher in hypomagnesemic patients. Hypomagnesemic patients required ventilator support for longer duration. Hypomagnesemia was commonly associated with sepsis and diabetes mellitus. The duration of MICU stay and APACHE score on admission did not vary in patients with low magnesium and normal magnesium. Hypomagnesemia is more commonly seen in patients with hypocalcemia and hypoalbuminemia.