A Fast Diet Without Too Many Sacrifices

Supplementation of Mg, P, K, and Ca should be initiated promptly. (Crit Care Med

2000; 28:2022-2125)

K EY W ORDS: head

Injury; neurologic trauma; hypomagnesemia; hypophosphatemia; electrolyte


Magnesium (Mg) is a cofactor in numerous enzymatic reactions, and Mg ions are

Important for regulation of the sodium/potassium (Na/K) transport across

Membranes through activation of a Na-K atpase pump [1][2] . Loss of

Cellular Mg results in depletion of intracellular K and changes in resting

Membrane potentials of various cells, including cardiac and vascular smooth

Muscle cells [1]

. Mg is a natural calcium channel blocking agent, and low levels of Mg are

Associated with hypocalcemia. Hypomagnesemia has been linked to cardiac

Arrhythmias associated with Q-T and P-R prolongation (including attacks of

Torsades de pointes), increased sensitivity to digoxin, sudden death, ischemic

Heart disease, hypertension, coronary vasoconstriction, transient ischemic

Attacks, strokes, seizures, neuromuscular irritability, preeclampsia-eclampsia,

And diabetes [1][2][3][4][5][6][7]

. Hypomagnesemia is associated with increased mortality both in the general ward

[8] and in the

Intensive care unit (ICU) [8][9] .

Hypomagnesemia may result from gastrointestinal or renal losses (the latter

Because of primary renal Mg wasting) or from cellular redistribution of Mg. The

Plasma Mg concentration (0.8-1.1 mmol/L) is only equivalent to 1% of total body

Content. Thus, a Mg deficit may exist while plasma Mg concentration is normal,

And the occurrence of a low Mg level usually indicates significant total body Mg

Deficiency [4] .

However, measurement of plasma Mg, perhaps in combination with urinary Mg

Excretion, is the simplest way of testing for possible Mg deficiency [6]


Phosphate (P) is a major intracellular anion and plays an important role in

Many biochemical pathways relating to normal physiologic functions, especially

In maintaining muscle tone [7][10] .

Hypophosphatemia has been shown to be associated with muscle weakness, including

Weakness of respiratory muscles [11][12] , and with

Respiratory infection [12]

. Aubier et al. [13]

Found that hypophosphatemia impairs the contractile properties of the diaphragm

In critically ill patients, leading to difficulties in weaning from the

Ventilator. Low P may also be associated with decreased cardiac output and with

Ventricular tachycardia after myocardial infarction [14]

. Patients with hypophosphatemia may be asymptomatic


Or may experience weakness, malaise, anorexia, bone pain, and respiratory arrest

[10] .


K is the major intracellular cation, with relatively low extracellular

Levels. Changes in K levels can affect muscle contraction and nerve conduction;

Hypokalemia is associated with cardiac arrhythmias (especially in patients with

Ischemic heart disease and left ventricular hypertrophy), muscle weakness

(including weakness of respiratory muscles), rhabdomyolysis, renal failure, and

Hyperglycemia. Hypocalcemia is associated with neuromuscular irritability and

Muscle spasms, seizures, delayed ventricular repolarization, and cardiac


Patients with severe head injury are at risk for developing polyuresis

Through a variety of mechanisms, including the syndrome of inappropriate

Antidiuretic hormone secretion, cerebral salt loss, and other, as yet unknown,

Mechanisms. In addition, patients with cerebral trauma are often treated with

Mannitol, which can induce or increase polyuresis. Thus, polyuresis is likely to

Occur in patients with severe head injury. We speculated that this excessive

Diuresis might lead to the loss of various important electrolytes, including Mg,

P, K, and calcium (Ca). In addition, neurologic trauma in itself can induce

Severe arrhythmias [15]

; therefore, clinical effects of electrolyte disorders might be enhanced in

These patients. Routine laboratory tests at admission in most hospitals and most

Icus do not include Mg and P; therefore, low levels of Mg and P are likely to

Remain undetected longer than frequently tested electrolytes, such as Na or K.

The aim of this study was to assess whether levels of the above-mentioned

Electrolytes were low in patients with severe head injury at admission to our

ICU and to compare these levels with patients with no or only mild head injury.METHODS

The hospital ethics committee approved the study. We measured plasma levels

Of Mg, P, K, Ca, and Na at admission in 18 consecutive patients with severe head

Injury (Glasgow Coma Scale [GCS] score, 12)

Admitted to our ICU (group 1). As controls, we used 19 trauma patients with two

Or more bone fractures, but no or only mild head injury (GCS 14-15, group 2). Of

19 controls, nine were admitted to the ICU and ten to the high-care unit

Adjacent to the ICU. We also assessed various clinical variables such as

Clinical outcome, duration of stay in the ICU, and Acute Physiology and Chronic.