Cardiac Effects of Hypomagnesemia and Drugs Related to Anesthesia.

• Project/Area Number: 11470327
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Anesthesiology/Resuscitation studies
• Research Institution: Jichi Medical School
• Principal Investigator: INOUE Soichiro (2000-2001) Jichi Medical School. Dept. of Medicine, Assistant Lecture, 医学部, 助手 (20322399); 清水 禮壽 (1999) 自治医科大学, 医学部, 教授 (60010253)
• Co-Investigator(Kenkyū-buntansha): IKENO Shigeo Dept. of Medicine, Assistant Lecture, 医学部, 助手 (60265270) ; NAKAIGAWA Yasushi Dept. of Medicine, Lecture, 医学部, 講師 (40245056) ; AKAZAWA Satoshi Dept. of Medicine, Associate Professor, 医学部, 助教授 (10184079) ; SEKIGUCHI Masato Dept. of Medicine, Assistant Lecture, 医学部, 助手 (80322395) ; 石井 良介 自治医科大学, 医学部, 講師 (50222956) ; 井上 荘一郎 自治医科大学, 医学部, 助手
• Project Period (FY): 1999 – 2000
• Project Status: Completed (Fiscal Year 2001)
• Budget Amount: ¥2,700,000 (Direct Cost: ¥2,700,000); Fiscal Year 2000: ¥2,700,000 (Direct Cost: ¥2,700,000)
• Keywords: magnesium / hypomagnesemia / furosemide / halothane / epinephrine / arrhythmia / cardiac surgery / fractional excretion of magnesium / 吸入麻酔薬 / ラット

Research Abstract

In the study I, an experimental rats model for hypomagnesemia was developed with continuous intravenous infusion of furosemide (3mg・day^<-1>) for 7 days.
In the study II, the arrhythmogenic thresholds of epinephrine during hypomagnesemia and mild hypokalemia under halothane anesthesia were evaluated in the rat developed in the study I. Adult male Sprague-Dawley rats which had received continuous intravenous infusion of lactate Ringer's solution 48ml・day^<-1> (control group, n = 10) or the combined solution with lactate Ringer's solution and furosemide (3mg・day^<-1>) (hypomagnesemia group, n = 10) for 7 days were anesthetized with halothane (1.5 %), and the arrhythmogenic thresholds of epinephrine were determined with logarithmically spaced increasing does of intravenous epinephrine. The arrhythmogenic dose of epinephrine and plasma concentration of epinephrine at the thresholds in the hypomagnesemia group were significantly decreased. We concluded that hypomagnesemia and mild hypokalemi a induced by furosemide significantly decreased the arrhythmogenic threshold of epinephrine under halothane anesthesia.
In the Study III, changes in serum total and ionized magnesium concentrations ([tMg] and [Mg^<2+>], respectively) and correlated factors during cardiac surgery were examined. Both [tMg] and [Mg^<2+>] decreased significantly from the prebypass period and remained so thereafter, though transient increases compared with the preceding values were observed during CPB. Hematcrit decreased significantly following the induction of anesthesia and remained so throughout the study period. Although significant changes were observed in [Ca^<2+>] and PTH concentrations, Ca-PTH relation was kept during the study period. Fractional excretion of Mg remained less than 6 % in the prebypass period, and increased significantly from the aortic cross-clamp to the postbypass period. It is concluded that hemodilution was main reason of hypomagnesemia during the prebypass period, and renal magnesium loss was also involved in hypomagnesemia during CPB and the postbypass period.