Magnesium and acute myocardial infarction. Transient hypomagnesemia not induced by renal magnesium loss in patients with acute myocardial infarction

Serum magnesium concentrations and the rate of urine magnesium excretion were studied in 24 patients with suspected acute myocardial infarction (AMI). Blood and urine samples were taken on admission, at three-hour intervals for the first 24 hours after admission, and every eight hours for the next 24 hours. Thirteen of the patients were found to have AMI, and the 11 who did not have AMI served as a control. During the first 32 hours, the AMI group had significantly low serum magnesium concentrations. The serum magnesium concentrations were unchanged in the control group. Results of the urine samples disproved our hypothesis that the drop in serum magnesium concentrations was due to an increased renal magnesium loss. These results indicate a magnesium migration associated with AMI, from extracellular to intracellular space.     

Relation of electrolytes to blood pressure in men. The Yi people study

The relations of sodium, potassium, calcium, and magnesium to blood pressure were investigated in four groups of men (119 high-mountain Yi farmers, 114 mountainside Yi farmers, 89 Yi migrants, and 97 Han people) with a wide range of electrolyte intake in Puge County, Sichuan Province, People's Republic of China. Electrolytes were measured in diet, serum, and urine. Sodium excretion was 73.9 mmol/24 hr in high-mountain Yi farmers, 117.9 mmol/24 hr in mountainside Yi farmers, 159.4 mmol/24 hr in Yi migrants, and 186.0 mmol/24 hr in the Han people. In ecological correlation analysis, dietary and urinary sodium were significantly and positively correlated with both systolic and diastolic pressure, whereas serum sodium showed no relation with blood pressure. In diet, serum, and urine, potassium was negatively related to systolic and diastolic pressure, whereas the sodium/potassium ratio showed a positive association. With regard to calcium, only urinary excretion was significantly and positively related to blood pressure. No relation was found between magnesium and blood pressure. Analyses at the individual level confirmed the results for sodium and potassium seen at the ecological level, but in addition, dietary calcium and magnesium were significantly and negatively correlated to both systolic and diastolic pressure, and urinary magnesium was inversely related to diastolic pressure. These relations persisted after controlling for age, body mass index (kg/m2), heart rate, alcohol, and total energy intake in multiple regression analysis performed separately for electrolytes in diet, serum, and urine. In multiple regression analysis, an increase in sodium intake of 100 mmol/day corresponded to an increase of 2.3 mm Hg systolic blood pressure and 1/8 mm Hg diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypomagnesemia in heart failure with ventricular arrhythmias. Beneficial effects of magnesium supplementation

OBJECTIVE: To assess the role of electrolyte imbalance in cardiac arrhythmias associated with congestive heart failure. DESIGN: Serum magnesium and potassium levels, urine magnesium excretion and the incidence of ventricular arrhythmias were assessed throughout the study. The patients who displayed complex arrhythmias after the first week of hospital medication were randomized 2:1 to double-blind magnesium supplementation or placebo. SETTING: The study was carried out in one municipal hospital, providing primary care. SUBJECTS: A total of 588 consecutive patients were screened for eligibility (clinical heart failure >/=6 months; NYHA class II-IV; left ventricular ejection fraction 相似文献   

The relationship between dietary intake and urinary excretion of sodium, potassium, calcium and magnesium: Belgian Interuniversity Research on Nutrition and Health

During an epidemiological survey, the dietary intake and urinary excretion of sodium, potassium, calcium and magnesium were measured by means of the 24 h food record method and a 24 h urine collection in 2,112 men and 1,943 women. Significant correlations (P less than 0.001) were found between dietary intake and urinary excretion of the above cations in men and women by univariate analysis and after adjustment for age, height, weight and total caloric intake. Taking into account the difficulty of estimating dietary cation intakes and obtaining complete 24 h urine collections, and the non-coincidence of the 24 h urine collection and the food recording periods, our findings point to a strong positive association between dietary intake and urinary excretion of sodium, potassium, calcium and magnesium. No significant relationship was found between these urinary cations and blood pressure.     

Renal, hemodynamic, and hormonal responses to atrial natriuretic peptide infusions in normal man, and effect of sodium intake

The effect of 60-min constant iv infusions of alpha-human atrial natriuretic peptide (alpha hANP; 200 micrograms), sufficient to increase the steady state venous plasma alpha hANP concentration to levels found in patients with some circulatory disorders, was studied in six normal men equilibrated on a high sodium diet (200 mmol daily) and again when equilibrated on a low sodium intake (10 mmol daily). In each instance, the responses to alpha hANP were compared to those to control infusions given on the preceding day. The mean steady state plasma immunoreactive ANP concentration during the infusions was 320 pmol/liter and was the same during both diets. Thus, the MCR of alpha hANP was unaffected by major changes in sodium intake. Compared to control day observations, infusions of alpha hANP induced a more than 3-fold increase in sodium excretion and at least a 2-fold increase in urine volume and calcium and magnesium excretion in subjects ingesting 200 mmol sodium daily. During the low sodium diet, alpha hANP was still diuretic and induced comparable magnesium excretion, but the natriuresis was only 11% of that during the high salt diet. No significant changes in blood pressure or heart rate occurred during alpha hANP infusions during either diet, although during both diets there was a significant rise in plasma norepinephrine (P less than 0.02), which persisted well beyond the disappearance of immunoreactive ANP from plasma. Despite this sympathetic activation, renin and aldosterone production was reduced by alpha hANP. During low salt intake, alpha hANP significantly decreased PRA (mean pretreatment, 1.79; posttreatment, 1.25 nmol/liter/h; P less than 0.03), angiotensin II (mean pretreatment, 49; posttreatment, 28 pmol/liter; P less than 0.008), and plasma aldosterone (mean pretreatment, 554; posttreatment 307 pmol/liter; P less than 0.007), whereas values during control infusions did not change. Similar percent decreases in PRA and aldosterone also occurred during the high salt diet. Plasma cortisol and arginine vasopressin did not change during the alpha hANP infusions on either diet. We conclude that steady state levels of alpha hANP in plasma, similar to those in patients with some circulatory disorders, significantly increase sodium excretion and inhibit all elements of the renin-angiotensin-aldosterone system. The natriuretic, but not the hormonal or chronotropic, effects of alpha hANP are reduced by sodium depletion in normal man.     

A comparison of the effects of semisynthetic human insulin and porcine insulin on transmembrane ion shifts and glucose metabolism during euglycaemic clamping

Disturbances of potassium, calcium, phosphate and magnesium homeostasis in diabetes mellitus are well documented. We have compared the effects of semisynthetic human and pancreatic porcine insulin on transmembrane shifts of these ions, and on glucose metabolism, at two insulin infusion rates, 20 and 50 mU/kg/h, during euglycaemic clamping for 2 h in 6 normal volunteers. The glucose requirements and the changes in blood metabolite concentrations were not significantly different during the porcine and human insulin infusions. Serum potassium levels, however, showed a significant greater decline with infusions of porcine insulin (4.2 +/- 0.1 to 3.5 +/- 0.1 mmol/l) compared with human insulin (4.2 +/- 0.1 to 3.7 +/- 0.1 mmol/l) at 50 mU/kg/h (P less than 0.05). Potassium levels were significantly lower during the porcine insulin infusion at 105 and 120 min and at 15 and 30 min after stopping the infusion. Electrocardiographic T-wave voltage decreased during the porcine and human insulin infusion by 0.13 +/- 0.02 and 0.10 +/- 0.01 mV, respectively (P less than 0.02). Changes in serum levels of magnesium, calcium, phosphate, and red blood cell concentrations of magnesium and 2,3-DPG, were not significantly different between the insulins. Thus a small but significant greater decline in potassium levels with similar glucose requirements was found during iv administration of porcine insulin compared with human insulin.     

Randomized,Double‐Blind,Placebo‐Controlled Trial of Spironolactone for Hypokalemia in Continuous Ambulatory Peritoneal Dialysis Patients

The incidence of hypokalemia in continuous ambulatory peritoneal dialysis (CAPD) patients is about 15–60%, leading to significant complications. There is no standard treatment other than potassium supplement in this setting. The aim of this study was to evaluate effect of spironolactone 25 mg/day in CAPD patients who have a history of hypokalemia. This is a randomized, double‐blind, placebo‐controlled, cross‐over study in CAPD patients who had a history of hypokalemia. Study intervention is 4 weeks of oral spironolactone 25 mg/day or placebo, cross‐over after a 2‐week wash‐out period. The primary outcome was the difference of serum potassium before and after 4 weeks of spironolactone treatment. Serum potassium was measured every 2 weeks, serum magnesium, urine and peritoneal fluid potassium measured before and after each treatment period. We enrolled 24 patients, and 20 completed the cross‐over study. Ten patients were anuric. The total doses of potassium supplement were the same during the study period. Serum potassium levels before and after study intervention were not significantly different in both groups (4.23 ± 0.64 vs. 3.90 ± 0.59 mEq/L for spironolactone P = 0.077 and 3.84 ± 0.62 vs. 3.91 ± 0.52 for placebo P = 0.551). Total 24‐h potassium, magnesium, sodium excretion, urine volume and ultrafiltration volume were not affected by spironolactone or placebo. There was one episode of hyperkalemia (5.6 mEq/L) during the spironolactone treatment period. Spironolactone 25 mg/day does not have a significant effect on serum potassium or urine and peritoneal excretion rate in CAPD patients who have a history of hypokalemia.     

Electrolyte disturbances in patients with chronic, stable asthma: effect of therapy

OBJECTIVE: To determine the prevalence of electrolyte disturbances in patients with chronic, stable asthma, and to assess whether the therapeutic agents used to treat chronic asthma have an effect on abnormal electrolyte levels. DESIGN: Prospective, hospital-based, cross-sectional study. SETTING: University teaching hospital in Jeddah, Saudi Arabia. PATIENTS: Patients with chronic, stable asthma. METHOD: Ninety-three consecutive patients with chronic, stable asthma were involved in the study. On the day of the visit to the asthma clinic, particulars such as age, sex, duration of asthma, and details of drug therapy were obtained from each asthmatic patient. Serum potassium, magnesium, phosphorus, calcium, and sodium levels were measured. Normal values were as follows: potassium, 3.5 to 5 mmol/L; magnesium, 0.74 to 1.2 mmol/L; phosphorus, 0.8 to 1.4 mmol/L; and calcium, 2.1 to 2.6 mmol/L. RESULTS: Electrolyte disturbances were found in 43% of the patients; 85% of the patients had one electrolyte disturbance, 10% had two electrolyte disturbances, and 5% had three electrolyte disturbances. The highest proportions were for magnesium (26.9%) and phosphorus (15.1%) [serum levels were 0.69 +/- 0.04 mmol/L and 0.64 +/- 0.09 mmol/L, respectively], the lowest proportions were for potassium (5.4%) and sodium (4.3%) [serum levels were 3.3 +/- 0.01 mmol/L and 133 +/- 0.01 mmol/L, respectively], and no patient had a calcium disturbance. Logistic regression analysis showed no statistically significant association between the therapy used and electrolyte disturbances. CONCLUSION: Hypomagnesemia and hypophosphatemia were found to be the two most common electrolyte disturbances in patients with chronic, stable asthma. Therapeutic agents used to treat patients with chronic asthma have no effect on abnormal electrolyte levels. The underlying cause still remains unclear.     

Magnesium infusion reduces the incidence of arrhythmias in acute myocardial infarction. A double-blind placebo-controlled study

In a double-blind placebo-controlled study, 130 patients with verified acute myocardial infarction were given magnesium or placebo treatment intravenously immediately upon admission to hospital. The incidence of arrhythmias requiring treatment during the initial week of hospitalization was registered. Serum magnesium concentrations were increased from 0.7 mmol/l to 1.3 mmol/l as a result of the magnesium infusions. This pharmacologically induced hypermagnesemia resulted in a reduction in the incidence of arrhythmias from 47% in the placebo group to 21% in the magnesium group (p = 0.003). In the magnesium-treated patients, increments in serum concentrations of magnesium and potassium correlated positively (r = 0.47, p less than 0.001). It is concluded that magnesium infusion in the postinfarct period reduces the incidence of supraventricular tachyarrhythmias, and possible pathophysiological mechanisms involved are discussed.     

Influence of increased adrenergic activity and magnesium depletion on cardiac rhythm in alcohol withdrawal.

OBJECTIVE--To investigate the prevalence of arrhythmias in alcoholic men during detoxification and its relation to neuroendocrine activation and electrolyte disturbances. DESIGN--Consecutive case-control study. SETTING--Primary and secondary care, detoxification ward. PATIENTS AND CONTROLS--19 otherwise healthy alcoholic men (DSM-III-R) with withdrawal symptoms necessitating detoxification in hospital. 19 age matched, healthy non-alcoholic men as controls for Holter recordings. INTERVENTIONS--Treatment with chlomethiazole; additional treatment with carbamazepine in patients with previous seizures. MAIN OUTCOME MEASURES--Computer based analyses of mean heart rate and arrhythmias from 24 hour Holter recordings, 24 hour urinary excretion of adrenaline and noradrenaline, magnesium retention measured by means of intravenous loading test, and serum concentrations of electrolytes. RESULTS--The 24 hour mean heart rate was higher in the alcoholic men (97.4 beats/minute, 95% confidence interval (CI) 91.2 to 103.6) than in the controls (69.6 beats/minute, 95% CI 65.4 to 73.8, P < 0.001). However, there was no difference in diurnal heart rate variation. The prevalence of premature supraventricular depolarisations was lower in the alcoholic men (P < 0.05). Neither atrial fibrillation nor malignant ventricular arrhythmias occurred. The sinus tachycardia in the alcoholic men correlated with the concomitant urinary excretion of catecholamines (P < 0.05). The mean serum magnesium concentration was 0.78 mmol/l (95% CI 0.73 to 0.83) in the alcoholic men and 0.83 mmol/l (95% CI 0.81 to 0.85) in a reference population of 55 men aged 40. Magnesium depletion (defined as magnesium retention > 30%) was detected in 10 alcoholic men (53%). Three alcoholic men had serum potassium concentrations < or = 3.3 mmol/l on admission. CONCLUSION--Increased adrenergic activity, magnesium depletion, and hypokalaemia are often seen after heavy drinking, but in alcoholic men without clinical heart disease these changes were not accompanied by arrhythmias other than sinus tachycardia during detoxification in hospital.     

低钾血症对急性心肌梗死患者预后的影响

目的探讨急性心肌梗死(AMI)患者低钾血症的发生情况及其对预后的影响。方法对929例ST段抬高的AMI患者于入院时抽血测定血钾、肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)、肌钙蛋白I(cTnI),根据血钾水平分为低血钾组(血钾<3.5 mmol/L)和正常血钾组(血钾3.5~5.5 mmol/L),同时观察住院期间严重不良事件(室性心动过速、心室颤动和猝死)的发生情况。结果低钾血症的发生率为13.7%,下壁+后壁AMI的发生率最低(10.4%),明显低于下后壁+右心室、前间壁和广泛前壁心肌梗死;发病至抽血时间≤3 h的低钾血症发生率为17.3%,明显高于发病时间>3 h者;低血钾组的CK、CK-MB和cTnI峰值明显高于正常血钾组;低血钾组总的严重不良事件发生率(23.8%)明显高于正常血钾组(15.8%)。结论低钾血症与AMI患者的梗死时间、部位和面积相关,并严重影响患者的预后。     

Hypokalemia,Arrhythmias and Early Prognosis in Acute Myocardial Infarction

ABSTRACT Serum potassium concentration was estimated on admission to hospital in 289 women and 785 men with acute myocardial infarction. The proportion of women in potassium subgroups was inversely related to serum potassium concentration, increasing from 8% at serum potassium ≥5.2 mmol/1 to 58% at ≤3 mmol/1. The frequency of diuretic therapy was also higher in women (35%) than in men (23%). The mortality rate was high at 3 months in patients with one or more arrhythmias (atrioventricular block grade 2, complete heart block, bundle branch block, atrial fibrillation, premature ventricular contractions, ventricular tachycardia) detected by conventional methods during the first 48 hours after admission. Hypokalemia (serum potassium ≤3.5 mmol/1) did not significantly predict increased occurrence of any of these arrhythmias. Small inhomogeneities of arrhythmias between the potassium groups may have been caused by digitalis therapy prior to admission. Hypokalemia on admission did not predict altered prognosis during the first 3 months.     

肝硬化顽固性腹水早期预测及相关因素分析

目的探讨肝硬化顽固性腹水的影响因素及早期预测腹水消退难易的方法。方法根据治疗后腹水消退的情况，将45例肝硬化大量腹水患者分为腹水消退组（A组）25例和腹水未消退组（B组）20例。分别回顾性分析腹水的消长与血清钠、尿比重、尿钠排泄量、24h尿量、血清醛固酮之间的关系。结果A组患者尿钠量（244．4±89．01mmol／24h）、尿比重（1．023±0．01）明显高于B组（114．7±30．54mmol／24h、1．012±0．003）；无论是腹水消退组还是腹水未消退组尿钠均较正常值低，治疗后B组尿钠量、尿钾、尿比重的改善幅度较A组明显减低，甚至达不到A组治疗前的水平；B组患者血清醛固酮水平（318．65±49．75pg／m1）明显高于A组（84．28±15．45pg／ml，P〈0．01）。各因素之间相关因素分析表明，血清醛固酮与尿钠排泄量、尿比重显著相关。血清醛固酮水平在治疗前和治疗后与尿钠、尿比重均呈显著负相关，相关系数分别为：治疗前，r=-0．717，-0．736，治疗后r=-0．926，-0．928（t9值均〈0．01）。结论血清醛固酮的升高，尿钠排泄量和尿比重的降低是腹水难以消退的主要因素。这些指标对腹水消退治疗的改善程度具有较好的预测作用。     

Vitamin D repletion in patients with primary hyperparathyroidism and coexistent vitamin D insufficiency

Vitamin D insufficiency is common in patients with primary hyperparathyroidism (PHPT) and may be associated with more severe and progressive disease. Uncertainty exists, however, as to whether repletion of vitamin D should be undertaken in patients with PHPT. Here we report the effects of vitamin D repletion on biochemical outcomes over 1 yr in a group of 21 patients with mild PHPT [serum calcium <12 mg/dl (3 mmol/liter)] and coexistent vitamin D insufficiency [serum 25 hydroxyvitamin D [25(OH)D] <20 microg/liter (50 nmol/liter)]. In response to vitamin D repletion to a serum 25(OH)D level greater than 20 microg/liter (50 nmol/liter), mean levels of serum calcium and phosphate did not change, and serum calcium did not exceed 12 mg/dl (3 mmol/liter) in any patient. Levels of intact PTH fell by 24% at 6 months (P < 0.01) and 26% at 12 months (P < 0.01). There was an inverse relationship between the change in serum 25(OH)D and that in intact PTH (r = -0.43, P = 0.056). At 12 months, total serum alkaline phosphatase was significantly lower, and urine N-telopeptides tended to be lower than baseline values (P = 0.02 and 0.13, respectively). In two patients, 24-h urinary calcium excretion rose to exceed 400 mg/d, but the group mean 24-h urinary calcium excretion did not change. These preliminary data suggest that vitamin D repletion in patients with PHPT does not exacerbate hypercalcemia and may decrease levels of PTH and bone turnover. Some patients with PHPT may experience an increase in urinary calcium excretion after vitamin D repletion.     

Effect of magnesium supplementation on the fractional intestinal absorption of 45CaCl2 in women with a low erythrocyte magnesium concentration

The cosupplementation of magnesium with calcium has been suggested to be beneficial in the prevention of osteoporosis. We investigated the effect of magnesium supplementation on parameters of bone resorption and fractional 45Ca absorption. Twenty apparently healthy women with a mean age of 39.2 +/- 9.2 years and an erythrocyte magnesium concentration less than 1.97 mmol/L were recruited into a controlled magnesium supplementation trial. During weeks 1 to 4, they received a daily control preparation, potassium/sodium citrate malate (PSCM). During weeks 5 to 8, the subjects received magnesium citrate malate (MCM) equivalent to 250 mg magnesium per day. During the fourth and eighth weeks, blood was collected for measurement of the serum intact parathyroid hormone (PTH) concentration and serum and erythrocyte magnesium concentration. Urine was collected for measurement of calcium, magnesium, creatinine, and deoxypyridinoline excretion. On the final day of each treatment period, 5 microCi45CaCl2 was administered orally, and the isotope was traced in the blood and urine over 7 hours. Urinary calcium, 45Ca, and deoxypyridinoline excretion, as well as serum intact PTH levels, showed no statistically significant changes as a result of magnesium supplementation. However, urinary magnesium excretion increased by 31.1% (P < .005) while fractional 45Ca absorption decreased by 23.5% (P < .001) as a result of magnesium supplementation. It is concluded that magnesium supplementation does not result in changes in bone resorption, while the fractional intestinal absorption of 45Ca appears to decrease.     

Persistent hyperglycemia is associated with left ventricular dysfunction in patients with acute myocardial infarction.

BACKGROUND: The relationship of changes in blood glucose concentrations after admission to left ventricular (LV) dysfunction in patients with recanalized anterior acute myocardial infarction (AMI) remains unclear. METHODS AND RESULTS: Blood glucose concentrations were measured on admission and 24 h after symptom onset in 210 patients with recanalized anterior AMI within 6 h of symptom onset. Of them, 142 had hyperglycemia on admission, defined as a blood glucose >or=8.9 mmol/L, and 68 patients did not. Among the patients with admission hyperglycemia, 49 had persistent hyperglycemia, defined as a blood glucose >or=8.9 mmol/L 24 h after onset, and 93 did not. The incidences of myocardial blush grade of 0/1 after recanalization indicating impaired myocardial perfusion (71%), and peak creatine kinase concentration (5,631+/-2,855 mU/ml) were higher and predischarge LV function (43+/-11%) was lower in patients with persistent hyperglycemia than in those without (p<0.01). Multivariate analysis showed that persistent hyperglycemia was independently associated with LV dysfunction, defined as a predischarge LV ejection fraction 相似文献   

Effects of alpha-human atrial natriuretic peptide in essential hypertension

Because there is little published information on the effects of atrial peptides in hypertensive humans, 100 micrograms of alpha-human atrial natriuretic peptide was injected intravenously into six patients with essential hypertension in a double-blind, placebo-controlled study under standardized conditions of body posture and dietary sodium and potassium intake. The peptide increased urine sodium excretion sixfold in the first 30 minutes. Smaller increments occurred in urine volume and in calcium, magnesium, and phosphorus excretion; the rise in urine potassium concentration was not statistically significant. Most of these indices returned to time-matched placebo values within 1 hour, but urine sodium excretion remained high for 2 1/2 hours. Arterial pressure fell within 2 minutes of alpha-human atrial natriuretic peptide injection, then returned to matching placebo levels by 10 minutes. Conversely, heart rate increased rapidly and remained elevated for 3 hours. The peptide induced a prompt, brief rise in plasma norepinephrine concentration and a more sustained fall in epinephrine and aldosterone levels, but it did not affect plasma renin activity or cortisol concentration. Compared with normotensive volunteers studied previously under the same conditions, the hypertensive subjects had a greater response in urine volume and sodium, calcium, and magnesium excretion but a less sustained fall in arterial pressure.     

Effect of parathyroid hormone administration in a patient with severe hypoparathyroidism caused by gain-of-function mutation of calcium-sensing receptor

Hypoparathyroidism caused by gain-of-function mutations of the calcium-sensing receptor (CaR) in the transmembrane domain is usually severe and difficult to manage. A patient with severe hypoparathyroidism, caused by CaR activating mutation F821L, was treated for 3 days (Day 1 to Day 3) with synthetic human parathyroid hormone 1-34 (teriparatide, PTH). An Ellsworth-Howard test of the patient revealed normal responses of urine phosphate and cyclic AMP excretion, indicating that the patient's renal tubules normally responded to extrinsic PTH. On Day 1 to Day 3, 0.9 microg/kg/day of PTH was administered subcutaneously twice daily at 0800 and 2000. On Day 1, the serum calcium level that was 1.8 mmol/l before PTH administration increased to 2.1 mmol/l at 1200, and gradually decreased to 1.8 mmol/l at 2000. On Days 2 and 3, the maximum calcium levels were 2.5 and 2.4 mmol/l, respectively, at 1200. At 2000, they returned to or below basal levels at 0800. On Day 4 without PTH administration, the calcium levels were maintained at the basal levels at Day 0. The urine calcium/creatinine (Ca/Cr) ratio that was high (>0.4) before PTH injection decreased after PTH administration (0.4>). Changes in the ionized calcium levels were almost parallel with the total calcium levels. The serum inorganic phosphate (IP) level decreased to 2.4 mmol/l at 1000, but gradually increased before the second PTH injection to the level at 0800 on Day 1. The minimum IP level on Days 2 and 3 was 2.1 mmol/l and 2.0 mmol/l, respectively. In contrast to the remarkable changes in the serum calcium level by PTH treatment, the serum magnesium levels showed few changes. These results indicate that PTH therapy could be effective in correcting serum and urine calcium and the phosphate levels in hypoparathyroidism caused by activating mutation of CaR.     

Clinical and metabolic features of thyrotoxic periodic paralysis in 24 episodes

BACKGROUND: Hypokalemia is a well-known, consistent finding in thyrotoxic periodic paralysis (TPP). It is less well known that hypophosphatemia and mild hypomagnesemia are often present in TPP and that rebound hyperkalemia can occur as a result of potassium therapy. OBJECTIVE: To report the prevalence of these electrolyte abnormalities in 24 episodes of TPP in 19 patients admitted to a single university-affiliated public hospital during a 15-year period. METHODS: The medical records of all patients admitted to the Santa Clara Valley Medical Center in San Jose, Calif, between August 1, 1982, and June 1, 1997, with any type of hypokalemic periodic paralysis were reviewed. In patients with TPP, serum potassium, phosphorus, and magnesium levels were evaluated during and after episodes of paralysis. The administered dose of potassium chloride, recovery time from hypokalemia, and prevalence of rebound hyperkalemia after recovery were also ascertained. Data are presented as mean +/- SD. RESULTS: Hypokalemia was present in all 24 initial episodes of TPP, with serum potassium levels ranging from 1.1 to 3.4 mmol/L (mean, 1.9+/-0.5 mmol/L). After recovery from hypokalemia, the maximum serum potassium level significantly increased, ranging from 4.0 to 6.6 mmol/L (mean, 4.9+/-0.5 mmol/L; P<.001). In 10 (42%) of 24 episodes, rebound hyperkalemia (serum potassium level >5.0 mmol/L) was present. Recovery time did not correlate with the potassium chloride dose administered (r = 0.17). Initial serum phosphorus levels ranged from 0.36 to 0.97 mmol/L (mean, 0.61+/-0.23 mmol/L) (1.1-3.0 mg/dL [mean, 1.9+/-0.7 mg/dL]), with hypophosphatemia present in 12 (80%) of 15 episodes. Serum phosphorus levels significantly increased (P<.01), to 1.26 to 1.74 mmol/L (mean, 1.48+/-0.16 mmol/L) (3.9-5.4 mg/dL [mean, 4.6+/-0.5 mg/dL]), with or without phosphorus replacement therapy. A slight increase in serum magnesium levels after paralysis resolved was observed in all patients (P<.07). No further episodes of paralysis occurred in any patients after they became euthyroid. CONCLUSIONS: Hypokalemia, hypophosphatemia, and mild hypomagnesemia are characteristic features of TPP. Hypokalemia occurred in 100% and hypophosphatemia in 80% of the episodes in our study. Rebound hyperkalemia is a potential hazard of potassium administration and occurred in 42% of 24 episodes.     

Nutritional dose of magnesium in hypertensive patients on beta blockers lowers systolic blood pressure: a double-blind,cross-over study

Abstract. Objectives. To evaluate if magnesium alters blood pressure in hypertensive patients treated with beta blockers and if such effect can be coupled to a change in potassium and magnesium levels in muscle, serum and urine. Design. A randomized double-blind, cross-over study with magnesium and placebo taken orally, each for 8 weeks. Setting. Outpatient clinic, University Hospital, Umeå, Sweden. Subjects. Thirty-nine patients aged 26–69 years with moderate essential hypertension, treated before entry and during the study with continuous, unchanged beta blockers completed the study. Interventions. Random allocation to receive magnesium aspartate or placebo. Daily magnesium dose was 15 mmol(365 mg) distributed three times a day over 8 weeks. Main outcome measures. Blood pressure, serum, urine and muscle magnesium and potassium. Measurements performed at the start, after 8 and 16 weeks. Results. Systolic supine and standing blood pressure significantly decreased when magnesium was supplemented following placebo but not when magnesium was given at start. When magnesium and placebo groups were independently compared there was no significant change in supine and standing systolic and diastolic pressure. Serum and urine magnesium and serum potassium were significantly higher after magnesium treatment, whilst no change was present in urine potassium or in muscle magnesium and potassium. Conclusions. This study showed that 15 mmol magnesium day^-1 given to mild to moderate hypertensive patients treated with beta blockers could be the cause of a significant decrease in supine and standing systolic blood pressure.