THE INFLUENCE OF SERUM MAGNESIUM LEVELS ON BRAIN TISSUE OXYGENATION AFTER SEVERE TRAUMATIC BRAIN INJURY

Traumatic brain injury is one of the leading causes of morbidity and mortality in the United States. A number of different pharmacological and therapeutic based clinical trials have proven to not be efficacious for reversing these trends. In fact, many of these clinical trials have had deleterious effects on patient outcome. Clinical trials with magnesium supplementation are included in this group. The routine use of magnesium may increase the likelihood of secondary hypoxic and anoxia events in these patients, therefore leading to increases in morbidity and mortality in a number of patient populations. The purpose of this study was to investigate the effects of magnesium supplementation on cerebral oxygen tension levels after closed head injury. Nineteen severe head injury patients, who had both cerebral oxygen probe placement and magnesium supplementation within the first 48 hours after injury were included in this study. All interventions were performed under patient consent and Institutional Review Board approval. The cerebral vascular response to magnesium varied by patient, with some patients having dramatic loses or gains in oxygen levels, while others were unaffected. Since only two female patients were included in this group, statistical analysis of data was restricted to the males of the study group. Overall cerebral oxygen levels were clinically unchanged during magnesium infusion periods (27.698 mmHg versus 24.886mmHg) using a mixed model regression adjusting for cerebral perfusion pressure, time after a magnesium infusion and percent of inspired oxygen (p<0.0001). An additional model was constructed controlling for the same variables to investigate the impact of the magnesium dose on tissue oxygenation. Only doses of two or four grams of magnesium improved brain tissue oxygenation (B=8.980 and 8.500 respectively p< 0.001). In conclusion magnesium infusions are not adversely affecting tissue oxygen levels after head injury and a dose of four grams or less during actually improve oxygen levels. The public health significance of this study is that the routine use of intravenous magnesium supplementation may exacerbate tissue injury in patients with impaired blood flow to the brain. The resulting increases in the mortality and morbidity to brain injury patients would have an enormous economic and social cost