[Diagnosis of magnesium deficiency in intensive care patients]

AIM

Magnesium deficiency was investigated in critically ill patients, comparing measurements of plasma concentrations with the results obtained by the magnesium tolerance test.

DESIGN AND METHODS

20 critically ill patients (5 females, 15 males) between the ages of 27 and 86 were investigated. Magnesium plasma concentrations were determined before the magnesium tolerance test according to Ryzen was performed. For this purpose, magnesium sulfate (0.1 mmol/kg) was infused intravenously over four hours. Renal magnesium excretion was measured in the 24 h urine beginning at the start of the infusion. Magnesium concentrations in plasma and urine were determined using atomic absorption spectrophotometry.

MAIN RESULTS

In 12 patients magnesium plasma concentrations were decreased to 0.58-0.79 mmol/l. 6 patients showed values within the normal range of 0.80 to 1.0 mmol/l. In 2 patients the plasma concentration was increased to 1.07 and 1.27 mmol/l. Parenteral magnesium tolerance testing revealed a considerable magnesium deficiency by retention of 65-100% of the loading dose in 14 of the 20 patients. The remaining 6 patients retained 23-48% of the loading dose, thus demonstrating a moderate magnesium deficiency.

CONCLUSION

Determination of magnesium plasma concentration appears suitable as an informative preliminary survey, since low values are reliable indicating a magnesium deficiency. However, this study confirms that normal magnesium plasma concentrations do not exclude a considerable magnesium deficiency, which is more sensitively determined by the magnesium tolerance test.

Magnesium and calcium concentration in the pregnant and non-pregnant myometrium

OBJECTIVES

To investigate the effect of labor on the magnesium and calcium concentrations in the human myometrium and to compare them with the concentrations in the non-pregnant uterus.

METHOD

Samples of the isthmic part of the uterus were taken from 42 patients not in labor, 31 patients in regular labor during a cesarean section, and 37 premenopausal patients on whom a hysterectomy was performed.

RESULTS

(i) The magnesium concentration dropped significantly during labor; (ii) the calcium concentration in the tissue showed no significant changes during labor; (iii) the magnesium and calcium concentrations were significantly higher during pregnancy; (iv) the distribution of electrolytes in the myometrium differed significantly in the corpus, isthmus and cervix uteri.

CONCLUSIONS

The electrolyte concentration in the myometrium depends on the place of removal. A low magnesium concentration in the pregnant human myometrium could be a cause of premature labor.

Comparison of the determination of magnesium by methylthymol blue spectrophotometry and atomic absorption spectrophotometry

Plasma samples (n = 155) of 30 patients on an intensive ward were analysed for magnesium simultaneously by atomic absorption spectrophotometry (AAS) and methylthymol blue spectrophotometry. Methylthymol blue spectrophotometry was performed at the bedside, using two different multianalysers, Easy ST 1 and Easy ST 2, Merck, D-Darmstadt. Precision was 12.2% (Easy ST 1) and 17.1% (Easy ST 2), and the average value was 0.89 mmol/l, which was above the expected range (0.72-0.88 mmol/l). Accuracy was 16.25% (Easy ST 1) and 8.75% (Easy ST 2). Analyser 2 was more accurate (8.75% versus 6.25%) but less precise (17.1% versus 12.2%) than analyser 1. Precision of AAS was between the expected values of 0.69 and 0.84 mmol/l. Easy ST and AAS gave significantly different values (p < 0.0001) for 155 measurements. Comparison of AAS and methylthymol blue spectrophotometery showed that methylthymol blue spectrophotometry produced higher values than AAS (mean difference 0.186 mmol/l). Furthermore, analyses of 40 samples of a standardized plasma concentration with methylthymol blue spectrophotometry showed a very low precision (15.3%). Easy ST cannot be assigned for urinary measurements of magnesium. Experimentally measured samples gave unaccountable results.

Effects of meal on the pharmacokinetics of fluoride from oral monofluorophosphate

A two-treatment cross-over study was conducted on 8 Caucasian male healthy volunteers aged between 26 and 32 years in order to determine the influence of a standard meal on the bioavailability and pharmacokinetics of fluoride after a single oral administration of tablets containing the equivalent of 10 mg fluoride as sodium monofluorophosphate (Na-MFP, CAS 10163-15-2) in a fixed combination with 300 mg Ca as calcium gluconate and calcium citrate. The meal provoked a significant delay of the appearance of fluoride in blood (from 4 to 11 min), a slowing of the absorption rate, a prolongation of tmax (from 34 to 146 min), a decrease of Cmax (from 369 to 122 ng/ml) and a prolongation of the Mean Residence Time (from 7.1 to 9.1 h). However, the amount of fluoride entering in the systemic circulation was not affected by the meal, as shown by the ANOVA on the AUC and on the cumulated urinary excretion of fluoride in the 48 h following the administration of Na-MFP. It is concluded that appropriate meals do not influence the amount of absorbed fluoride from Na-MFP, and that they modify the rate of absorption with pattern that may improve the safety and possibly also the efficacy of Na-MFP.

Bioavailability and pharmacokinetics of fluoride from two glutamine monofluorophosphate preparations

A two-way cross-over study was conducted on 12 Caucasian male healthy volunteers aged between 25 and 38 years in order to determine the bioavailability and pharmacokinetics of fluoride after single oral administration in fasting conditions of two products (tablets and powder for oral use) of L-glutamine monofluorophosphate (G-MFP, CAS 116420-36-1). The two products contained the equivalent of 10 mg F and the equivalent of 300 mg CA as calcium gluconate and calcium citrate. The two products were found bioequivalent with regard to the release of fluoride, both on the basis of the AUC and Cmax of fluoride in plasma and of the urinary excretion of fluoride during the 48 h following the administration. The pharmacokinetics of fluoride in plasma is characterized by a short lag time (< 6 min), a rapid absorption, a peak which is reached 0.5-1.0 h after administration, followed by a biphasic elimination. The first phase with a k alpha of 1.8 h-1 is followed by a slower phase with a K beta of 0.14 h-1. Probably the terminal elimination rate is slower, about 0.05 h-1. The urinary excretion of fluoride during the 48 h after administration accounted for 40-50% of the administered dose of fluoride. The results are consistent with those found in previous studies after administration in fasting conditions of sodium fluoride or sodium monofluorophosphate alone or in combination with calcium salts.

Comparison of the antihypertensive efficiency of nitrendipine, metoprolol, mepindolol and enalapril using ambulatory 24-hour blood pressure monitoring

In a randomized 6-month study of 201 patients, the antihypertensive efficiency of the calcium antagonist nitrendipine, the beta 1-selective blocker metoprolol, mepindolol, the beta blocker with intrinsic activity and the angiotensin-converting enzyme inhibitor enalapril were compared as monitored by 24-hour ambulatory blood pressure (BP) measurements. The study was designed so that a comparable decrease in casual BP values was obtained with all 4 drugs. If normotension was not achieved with monotherapy, a diuretic also was administered. Pretreatment casual BP and mean 24-hour ambulatory BP values did not differ between the 4 groups. Normotension as assessed by casual BP measurements was observed in all 4 groups after 6 months of therapy, there being no significant differences between the groups. However, significantly more diuretics were required in the mepindolol (n = 14) and in the enalapril (n = 20) groups compared to the nitrendipine (n = 5) and metoprolol (n = 7) groups. Despite comparable casual BP control, the 4 groups differed significantly in their mean 24-hour measurements. The greatest systolic and diastolic BP decreases were seen in the metoprolol group. Metoprolol was also the most effective drug in decreasing the frequency of systolic pressure peaks greater than 180 mm Hg. Both beta blockers and enalapril significantly decreased the morning BP increase compared to the values before treatment, while nitrendipine did not. These data show that casual BP measurement is not a good predictor of 24-hour BP in patients taking hypertensive therapy. Despite an equal degree of "office" BP control, different antihypertensive regimens do not confer the same degree of "nonoffice" BP control.

[Plasma endothelin in normal probands and patients with nephrologic-rheumatologic and cardiovascular diseases]

Plasma concentrations of the recently isolated potent vasoconstrictory peptide endothelin were measured in 382 patients. The investigations were performed by means of a sensitive radioimmunoassay specific for Endothelin-1, 2. The results from 110 healthy volunteers displayed a normal range of 44.67 +/- 3.51 pg/ml. Significantly raised levels were found in 33 patients with chronic end-stage renal failure both before and after hemodialysis. In contrast, 35 patients with compensated renal insufficiency did not differ from the normals. Sixty-five patients after kidney transplantation revealed significantly elevated levels, as did 27 patients with acute myocardial infarction, 8 after coronary bypass surgery, and 5 with liver cirrhosis. The mean values of 27 patients with untreated hypertension, 22 with secondary hypertension, of various causes and 16 with coronary artery disease were comparable to the normal population. The values were significantly decreased in 9 pregnant women with hypertension and proteinuria. A marked decline was found in 5 patients with systemic lupus erythematodes, while 20 patients with rheumatoid arthritis demonstrated only a slight decrease. The pathophysiological role of endothelin as a local or circulating hormone in regulating systemic blood pressure or release of other hormones remains to be determined.

Low molecular weight heparin versus standard heparin. A long-term study in hemodialysis and hemofiltration patients

The influence of low molecular weight (LMW) heparin (Braun 21-23, Mulsungen, West Germany) and unfractionated standard heparin (SH) on blood clotting and other routine laboratory parameters was investigated in a 30 week cross-over study in 30 hemodialysis patients. The LMW heparin dose necessary (anti FXa-activity) for effective anticoagulation was two thirds of the standard heparin dose. Using these doses, both substances displayed identical antithrombotic effects. Complications were not seen in either group. PTT and thrombin time were only marginally effected by LMW heparin, whereas they were markedly prolonged by SH heparin. Factor VIII activity was significantly lower in the LMW heparin group as compared to the standard heparin group after 18, 24, and 30 weeks. Antithrombin III, fibrinogen, fibrin monomers, plasminogen, and alpha 2-antiplasmin were comparable in both groups. Creatinine, urea, hemoglobin, and hematocrit were also unchanged, excluding differences in dialysis efficacy or occult blood loss. Equal numbers of blood transfusions were necessary, but bleeding complications did not occur in either group. In conclusion, safe and effective dialysis can be performed using this low molecular weight heparin for anticoagulation in hemodialysis and hemofiltration. The possible benefits of LMW heparin (reduced frequency of bleeding, alleviation of hypertriglyceridemia) were not, however, apparent, possibly because of the short observation period and the low incidence of hemorrhagic complications in routine dialyses.

[24-hour blood pressure behavior in patients with untreated and treated hypertension in comparison with normotensive patients]

Blood pressure was continuously monitored over 24 h in 201 patients with mild to moderate essential hypertension using a noninvasive method. Measurements were made both before and after 6 months of antihypertensive treatment and the data were compared to results from 100 normotensive patients. The frequency with which blood pressure values above 140/90 mm Hg occurred during the 24-h period proved to be the most reliable parameter for distinguishing between hypertensive and normotensive profiles. The blood pressures of all patients could be normalized (less than 140/90 mm Hg) on single or combined drug therapy as assessed by casual measurement. However, significant differences were observed between the 24-h profiles of the treated patients and the control group. The mean 24-h blood pressure, the mean day and nighttime blood pressures, the mean hourly pressure, and the frequency of increased blood pressure values were all significantly higher in the patients on medication as compared to the normotensive controls. This would suggest that normotension, as defined by the control group, cannot be attained with antihypertensive medication. In conclusion, 24-h continuous blood pressure monitoring allows a better evaluation of blood pressure profiles and consequently, will be of greater value in assessing cardiovascular risk than occasional random measurements.

[Absence of nocturnal decrease in blood pressure in 24-hour blood pressure monitoring: an indication of secondary hypertension]

Non invasive 24 hours ambulatory blood pressure monitoring was performed in 81 patients with secondary hypertension (renoparenchymatous nephropathy n = 15, diabetic nephropathy n = 10, Conn's disease n = 4, renal artery stenosis n = 15, pheochromocytoma n = 2, hemodialysis patients n = 15 and patients after kidney transplantation n = 20). The results were compared to 201 patients with essential hypertension. The results showed that 98.5% of patients with essential hypertension have a nightly decline in blood pressure of at least 15 mmHg (systolic + diastolic), whereas 69% of patients with secondary hypertension showed either an attenuated circadian rhythm or no circadian rhythm. Patients with pheochromocytoma who had a night time increase in blood pressure demonstrated the greatest difference to the essential hypertension collective followed by patients with diabetic nephropathy, Conn's disease and the group of patients after kidney transplantation. After successful treatment of the condition leading to hypertension circadian periodicity returned in some patients. In summary these results suggest that the absence of a night time decline in blood pressure during 24-hour-ambulatory monitoring is an indication of secondary hypertension.

Treatment of reperfusion injury with intracoronary calcium channel antagonists and reduced coronary free calcium concentration in regionally ischemic, reperfused porcine hearts

The effect of intracoronary diltiazem, EGTA (ethylene-bis-(beta-aminomethylether)-N,N'-tetraacetic acid), nifedipine, verapamil and isotonic saline solution as placebo on reperfusion injury was investigated in regionally ischemic, reperfused porcine hearts. The left anterior descending coronary artery was distally occluded for 45 min and was reperfused for 3 days. Intracoronary infusion was started immediately before reperfusion and continued during 45 min of reperfusion. Infarct size was determined as the ratio of infarcted (tetrazolium stain) to ischemic myocardium (dye technique). Regional systolic shortening was assessed by sonomicrometry. Apart from left ventricular end-diastolic pressure before ischemia and during 45 min of reperfusion, global hemodynamic values in the five treatment groups did not differ; in particular, calculated left ventricular oxygen consumption before and during ischemia was equally low. Intracoronary EGTA decreased coronary venous free calcium concentration to about 70% of baseline value. Infarct size was reduced from 76 +/- 10% (control group, n = 8) to 60 +/- 10% (p less than 0.01) by intracoronary diltiazem (n = 8) and to 55 +/- 15% (p less than 0.01) by intracoronary EGTA (n = 8). Insignificant reductions in infarct size were found after treatment with intracoronary verapamil (63 +/- 18%, n = 8) and intracoronary nifedipine (68 +/- 9%, n = 7). Regional systolic shortening of the risk region, which did not differ among the groups before occlusion and during ischemia, recovered to the greatest extent in the EGTA-treated pigs (p less than 0.01 compared with values in the control group). Treatment with intracoronary calcium antagonists resulted in only marginal improvement of systolic shortening.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of CAPD and residual diuresis on the serum levels of alpha-1-microglobulin in end-stage renal disease

The chronic retention of proteins of low molecular weight (LMWP) seems to be connected with some unsolved problems of end-stage renal disease (e.g. reduced immune function, AB amyloidosis, hormonal imbalances), irrespective of the type of renal replacement therapy. Therefore, several recently discovered LMWPs such as alpha 1-microglobulin have to be evaluated concerning their contribution to the uremic syndrome. Although we observed a considerable daily loss of total protein into the CAPD dialysate, no differences were found in the removal of small proteins (MW less than 68 kilodaltons) when compared to conventional hemodialysis. Maintenance of renal function (residual diuresis greater than 100 ml/day) seems to be more potent keeping the serum concentrations of LMWP low than CAPD or hemodialysis.

[Ambulatory continuous 24-hour blood pressure monitoring in the diagnosis and therapy of arterial hypertension and modification by the antihypertensive agents enalapril, metoprolol, mepindolol and nitrendipine]

After improvement of technical equipment continuous ambulatory blood pressure monitoring is more and more used in the diagnosis of hypertension. New fully automatic systems permit a reliable registration and evaluation of 24-h blood pressure profiles. Typical circadian rhythmics of blood pressure, independent of a variability with different grades of activity, can be demonstrated in normotensive persons and also in patients with essential hypertension. Patients with secondary forms of hypertension show a nivellation or offset of circadian blood pressure rhythmics. A study was performed to examine the antihypertensive efficacy of the calcium antagonist Nitrendipine, the beta 1-adrenoceptor-selective blocker Metoprolol, the beta-blocker with intrinsic activity Mepindolol and the angiotensin converting enzyme inhibitor Enalapril in patients with mild to moderate hypertension over a period of 6 month. Continuous ambulatory blood pressure monitoring was performed before and after 6 month of therapy. 98 of 299 included patients broke off therapy, 47 of those because of side effects. Hydrochlorothiazide was given additionally if the antihypertensive effect of monotherapy was not sufficient after a period of 4 weeks. Morning blood pressure controls at the end of the treatment period showed normotensive values in all groups without significant differences between the groups before and at the end of the treatment period. The number of prescriptions of diuretics necessary to achieve normotension differed between the four treatment groups: Nitrendipine (n = 5), Metoprolol (n = 7), Mepindolol (n = 14), Enalapril (n = 20). In contrast to the morning blood pressure values the continuous 24-h blood pressure monitoring demonstrated significant differences between the therapy groups. Metoprolol turned out as most effective in lowering blood pressure and in reducing the number of systolic blood pressure peaks above 180 mmHg, but on the other hand showed the highest incidence of relative hypotension (less than 100 mmHg systolic, less than 80 mmHg diastolic). Mepindolol demonstrated a significant lower efficacy. In the Nitrendipin group least of all prescriptions of diuretics were necessary and the lowest number of hypotensive systolic blood pressure values occurred. Enalapril showed the most significant reduction of diastolic values above 100 mmHg and the lowest number of diastolic values below 80 mmHg, but the highest number of prescription of diuretics was necessary in the Enalapril group. In none of the four therapy groups a neutralisation of circadian blood pressure rhythmics was demonstrable.

[Primary hyperparathyroidism with acute pancreatitis during pregnancy]

During her second pregnancy a 27-year-old woman had recurrent acute pancreatitis, in the course of which primary hyperparathyroidism was diagnosed. After regression of the acute signs and under conservative treatment a parathyroid tumour was removed in the 26th week of pregnancy. Comparison of surgical and conservative treatment of primary hyperparathyroidism during pregnancy has indicated that the risk of complications in the neonate is much lower after surgical removal of the adenoma than with an attempt to postpone by symptomatic drug treatment the parathyroidectomy until after delivery.

Parameters of the kallikrein-kinin, coagulation and fibrinolytic systems as early indicators of kidney transplant rejection

In order to find early indicators of kidney transplant rejection before clinical symptoms were noticed, parameters of the coagulation, fibrinolytic and kallikrein-kinin systems were measured. Nineteen patients were followed before and daily after kidney transplantation during the first week and every second day in the following weeks. All patients received immunosuppressive therapy with cyclosporin and corticoids. Ten patients suffered from transplant rejection. The first rejection occurred on the 7th day after transplantation. Of all the parameters measured, kallikrein inhibition, beta-FXIIa inhibition, plasminogen and antithrombin III were early indicators of kidney transplant rejections. A rise in these parameters could be demonstrated 2-3 days before clinical signs were noticed. In the other 9 patients no significant rises in antithrombin III, plasminogen, kallikrein inhibition and beta-FXIIa inhibition could be found.

Functional organization of the spinal reflex pathways from forelimb afferents to hindlimb motoneurones in the cat. II. Conditions of the interneuronal connections

The interneuronal conditions of the descending pathways from forelimb afferents to hindlimb motoneurones were investigated by testing spatial interactions in these pathways and between these pathways and segmental lumbar reflex pathways. In high spinal unanaesthetized cats hindlimb motoneurones were intracellularly recorded and spatial interactions were tested between effects evoked by stimulation of pairs of ipsi- and contralateral forelimb nerves or pairs of a forelimb and an ipsilateral hindlimb nerve. The excitatory and late inhibitory pathways from forelimb afferents projecting to most of the hindlimb motoneurone pools, showed an interactive pattern which was distinctly different to the fast inhibitory pathway projecting specifically from ipsilateral forelimb afferents to flexor digitorum and hallucis longus (FDHL) motoneurones. Stimulation of homonymous or heteronymous pairs of two forelimb nerves of both sides evoked generally a distinct spatial facilitation of the excitatory and late inhibitory effects, while the specific early IPSPs to FDHL motoneurones were not facilitated. Paired stimulation of two forelimb nerves of one side only produced spatial facilitation of EPSPs or late IPSPs if low strength stimuli were used, using higher strength which induced larger effects, generally caused occlusion instead. In case of large IPSPs this may be due to the vicinity to the equilibrium potential. Except for an inhibition of cutaneous reflex pathways, the spatial interaction of the excitatory and late inhibitory pathways onto segmental lumbar reflex pathways was weak and variable. The fast inhibitory pathway to FDHL motoneurones showed a partial spatial facilitatory interaction with lumbar reflex pathways from cutaneous and group II muscle afferents. The second IPSP wave evoked by this pathway was inhibited by antidromic stimulation of the ventral root L7S1 and of the alpha-efferents of the antagonistic peroneal nerve. From the results conclusions are drawn on the interneuronal organization of the descending pathways from forelimb afferents to hindlimb motoneurones.