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Access: Acid-Base, Fluids, and Electrolytes - part 10

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Phương pháp tiếp cận cho các bệnh nhân với Hypomagnesemia. Nếu chẩn đoán là không rõ ràng từ lịch sử, hoặc là một nước tiểu 24 giờ cho Mg2 + hoặc nước tiểu tại chỗ cho tính toán của sự bài tiết phân đoạn của Mg2 là thu được +. Sự bài tiết phân đoạn của Mg2 + tính từ phương trình | FIGURE 11-4 Approach to the Patient with Hypomagnesemia. If the diagnosis Is not readily apparent from the history either a 24-hour urine for Mg2 or spot urine for calculation of the fractional excretion of Mg2 is obtained. The fractional excretion of Mg2 Is calculated from equation 11.1. Serum Mg2 is multiplied by 0.7 since only 70 of Mg2 Is freely filtered across the glomerulus 435 I Decreased serum magnesium Low 1Ơ-30 mg day 4 High 30 mg day 4 Increased renal losses Shift from ECF to ICF Increased Gl losses Primary Drugs Toxins Hungry bone syndrome Decreased oral intake Miscellaneous tubular injury Genetic disorders Refeeding syndrome Malabsorption Hyperthyroidism Diarrhea Secondary Osmotic diuresis Diuretics Hypercalcemia 436 DISORDERS OF SERUM MAGNESIUM TABLE 11-14 Treatment General principles The route of Mg2 repletion varies depending on the severity of associated symptoms Since renal Mg2 excretion is regulated by the concentration sensed at the basolateral surface of the TALH an acute infusion results in an abrupt increase in serum concentration and often a dramatic increase in renal Mg2 excretion for this reason much of intravenously administered Mg2 is quickly excreted Attempts are made to correct the underlying condition Drugs that result in renal Mg2 wasting should be minimized or discontinued Life threatening symptoms present The acutely symptomatic patient with seizures tetany or ventricular arrhythmias related to hypomagnesemia should be administered Mg2 intravenously In the life-threatening setting 4 mL 2 ampules of a 50 solution of magnesium sulfate diluted in 100 mL of normal saline 16 mEq of Mg2 1 gm MgSO4 8 m Eq Mg2 can be administered over 10 min this is followed by 50 mEq of Mg2 given over the next 12-24 h The goal is to increase serum Mg2 concentration above 1.0 mg dL Mg2 is administered cautiously in patients with impaired renal function and serum concentration monitored frequently DISORDERS OF SERUM MAGNESIUM 437 TABLE 11-14 Continued In .