Basic considerations on magnesium in the management of neurocritical patients

The Impact of Chronic Magnesium Deficiency on Excitable Tissues-Translational Aspects

Neuromuscular excitability is a vital body function, and Mg2+ is an essential regulatory cation for the function of excitable membranes. Loss of Mg2+ homeostasis disturbs fluxes of other cations across cell membranes, leading to pathophysiological electrogenesis, which can eventually cause vital threat to the patient. Chronic subclinical Mg2+ deficiency is an increasingly prevalent condition in the general population. It is associated with an elevated risk of cardiovascular, respiratory and neurological conditions and an increased mortality. Magnesium favours bronchodilation (by antagonizing Ca2+ channels on airway smooth muscle and inhibiting the release of endogenous bronchoconstrictors). Magnesium exerts antihypertensive effects by reducing peripheral vascular resistance (increasing endothelial NO and PgI2 release and inhibiting Ca2+ influx into vascular smooth muscle). Magnesium deficiency disturbs heart impulse generation and propagation by prolonging cell depolarization (due to Na+/K+ pump and Kir channel dysfunction) and dysregulating cardiac gap junctions, causing arrhythmias, while prolonged diastolic Ca2+ release (through leaky RyRs) disturbs cardiac excitation-contraction coupling, compromising diastolic relaxation and systolic contraction. In the brain, Mg2+ regulates the function of ion channels and neurotransmitters (blocks voltage-gated Ca2+ channel-mediated transmitter release, antagonizes NMDARs, activates GABAARs, suppresses nAChR ion current and modulates gap junction channels) and blocks ACh release at neuromuscular junctions. Magnesium exerts multiple therapeutic neuroactive effects (antiepileptic, antimigraine, analgesic, neuroprotective, antidepressant, anxiolytic, etc.). This review focuses on the effects of Mg2+ on excitable tissues in health and disease. As a natural membrane stabilizer, Mg2+ opposes the development of many conditions of hyperexcitability. Its beneficial recompensation and supplementation help treat hyperexcitability and should therefore be considered wherever needed.

Effect of perioperative magnesium sulfate on neurological outcome in neurosurgical patients: a randomized double-blind controlled trial

BACKGROUND

Supplemental magnesium sulfate has a potential neuroprotective role in acute brain injury. It is safe, widely available, and inexpensive. This study evaluated the effect of perioperative intravenous administration of magnesium sulfate on brain damage caused by neurosurgery.

METHODS

Prospective randomized double-blind controlled study. Fifty adult patients undergoing supratentorial neurosurgery (25 were assigned to magnesium sulfate group and 26 to the control group). On arrival to the operating room, the intervention group received intravenous magnesium sulfate, 4 g bolus in 100 mL of 0.9% saline solution lasting 20 min followed by 20 g in 1000 mL saline lasting 24 h. The control group received the same volume of saline. Serum S100B-protein levels 2 h after surgery was the primary outcome. Secondary outcomes were neuron-specific enolase, magnetic resonance imaging (MRI) parameters, neuropsychological testing, Glasgow Outcome Scale, and mortality, during hospital stay and at six and 12 months after surgery.

RESULTS

Statistically significant differences in the primary outcome were not found. At six months, MRI showed a mean surgical cavity volume of 10.0 cm3 (95% confidence interval [CI] 4.4-15.6) in the magnesium group vs. 26.9 cm3 (95% CI 13.8-39.9) in controls (P=0.02), gliosis/edema in 55% vs. 90.5% (P=0.014), and contrast enhancement around the cavity in 33.3% vs. 80% (P=0.041), respectively. Patients in the magnesium group showed better scores in some neuropsychological tests. There were no relevant adverse effects in magnesium group.

CONCLUSIONS

Neurosurgical patients treated with supplemental magnesium sulfate showed macroscopic improvement in some MRI parameters related to blood-brain barrier permeability and better performance in some focal cognitive domain.

Main Cations and Cellular Biology of Traumatic Spinal Cord Injury

Traumatic spinal cord injury is a life-changing condition with a significant socio-economic impact on patients, their relatives, their caregivers, and even the community. Despite considerable medical advances, there is still a lack of options for the effective treatment of these patients. The major complexity and significant disabling potential of the pathophysiology that spinal cord trauma triggers are the main factors that have led to incremental scientific research on this topic, including trying to describe the molecular and cellular mechanisms that regulate spinal cord repair and regeneration. Scientists have identified various practical approaches to promote cell growth and survival, remyelination, and neuroplasticity in this part of the central nervous system. This review focuses on specific detailed aspects of the involvement of cations in the cell biology of such pathology and on the possibility of repairing damaged spinal cord tissue. In this context, the cellular biology of sodium, potassium, lithium, calcium, and magnesium is essential for understanding the related pathophysiology and also the possibilities to counteract the harmful effects of traumatic events. Lithium, sodium, potassium-monovalent cations-and calcium and magnesium-bivalent cations-can influence many protein-protein interactions, gene transcription, ion channel functions, cellular energy processes-phosphorylation, oxidation-inflammation, etc. For data systematization and synthesis, we used the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) methodology, trying to make, as far as possible, some order in seeing the "big forest" instead of "trees". Although we would have expected a large number of articles to address the topic, we were still surprised to find only 51 unique articles after removing duplicates from the 207 articles initially identified. Our article integrates data on many biochemical processes influenced by cations at the molecular level to understand the real possibilities of therapeutic intervention-which must maintain a very narrow balance in cell ion concentrations. Multimolecular, multi-cellular: neuronal cells, glial cells, non-neuronal cells, but also multi-ionic interactions play an important role in the balance between neuro-degenerative pathophysiological processes and the development of effective neuroprotective strategies. This article emphasizes the need for studying cation dynamics as an important future direction.

Magnesium Sulfate and Cerebral Oxygen Saturation in Mild Traumatic Brain Injury: A Randomized, Double-Blind, Controlled Trial

Perioperative cerebral hypoperfusion/ischemia is considered to play a pivotal role in the development of secondary traumatic brain injury (TBI). This prospective randomized, double-blind, controlled study investigated whether magnesium sulfate (MgSO4) infusion was associated with neuroprotection in maintaining regional cerebral oxygen saturation (rSO2) values in patients with mild TBI undergoing general anesthesia. Immediately after intubation, we randomly assigned patients with TBI to receive either intravenous MgSO4 (30 mg/kg for 10 min, followed by a continuous infusion of 15 mg/kg/h) or a placebo (saline) during surgery. We also implemented an intervention protocol for a sudden desaturation exceeding 20% of the initial baseline rSO2. The intraoperative rSO2 values were similar with respect to the median (left. 67% vs. 66%, respectively; p = 0.654), lowest, and highest rSO2 in both groups. The incidence (left 31.2% vs. 24.3%; p = 0.521) and duration (left 2.6% vs. 3.5%; p = 0.638) of cerebral desaturations (the relative decline in rSO2 < 80% of the baseline value) were also similar for both groups. Although the patients suffered serious traumatic injuries, all critical desaturation events were restored (100%) following stringent adherence to the intervention protocol. Intraoperative remifentanil consumption, postoperative pain intensity, and fentanyl consumption at 6 h were lower in the MgSO4 group (p = 0.024, 0.017, and 0.041, respectively) compared to the control group, whereas the satisfaction score was higher in the MgSO4 group (p = 0.007). The rSO2 did not respond to intraoperative MgSO4 in mild TBI. Nevertheless, MgSO4 helped the postoperative pain intensity, reduce the amount of intraoperative and postoperative analgesics administered, and heighten the satisfaction score.