Epinephrine is a hypophosphatemic hormone in man. Physiological effects of circulating epinephrine on plasma calcium, magnesium, phosphorus, parathyroid hormone, and calcitonin

Serum Lactate Dehydrogenase to Phosphate Ratio as an Independent Predictor for Adverse Outcome of Microsurgical Clipping for Ruptured Intracranial Aneurysm: A Propensity-Score Matching Analysis

Objective: In this study, we assessed the correlation between the lactate dehydrogenase (LDH) to phosphate ratio and the prognosis of microsurgical clippings for ruptured intracranial aneurysm (rIA) to test the hypothesis that the serum LDH to phosphate ratio could be a predictor of the outcome of microsurgical clipping for rIA. Methods: Records of rIA patients between 2012 and 2018 were retrospectively collected. Age, sex, Hunt-Hess grade, Fisher grade, medical history, aneurysm location, hydrocephalus, laboratory data including serum LDH, phosphate, and LDH to phosphate ratio, related complications, and the outcomes in 3 months were recorded. Results: A total of 1608 rIA patients in our institution were collected, and 856 patients treated by microsurgical clipping were enrolled. On admission, a significantly higher LDH-phosphate ratio was observed in patients with poor outcomes at 3 months (median ± SD, 200.175 ± 107.290 for mRS 0−2 vs. 323.826 ± 219.075 for mRS score 3−6; p = 0.000). An LDH to phosphate ratio of 226.25 in the receiver operating characteristic (ROC) curve was the optimal cutoff value to discriminate between good and poor outcomes at 3 months. The LDH to phosphate ratio ≥ 226.25 on admission was independently correlated with poor outcomes in rIA patients. In addition, Hunt and Hess grade, Fisher grade, pneumonia, and DIND were also independently correlated with poor outcomes. After removing the bias in essential clinical variables between patients with LDH to phosphate, ratio ≥ 226.25 versus <226.25 by PSM, the number of patients with poor outcomes at 3 months increased in patients with an LDH to phosphate ratio of ≥226.25 (p = 0.005). Conclusions: The LDH to phosphate ratio was a potential biomarker and could predict the unfavorable outcome of microsurgical clipping for rIA in 3 months, related to neuronal damage, cerebral hypoxia, and early brain injury after aneurysm ruptures.

Association of urine phthalate metabolites, bisphenol A levels and serum electrolytes with 24-h blood pressure profile in adolescents

BACKGROUND

Among the possible causes of hypertension in adolescence, electrolyte imbalances and environmental pollutants are drawing increasing attention. We aimed to examine the relationship between bisphenol A (BPA), phthalate metabolites, and serum electrolytes and blood pressure.

METHODS

Eighty-six participants aged 12-15 years were included in the study. Body mass index (BMI), office blood pressure and 24-h ambulatory blood pressure measurements (ABPM), and carotid intima-media thickness were determined. Blood samples were taken for hemogram, renal function tests, and serum electrolytes. Free- and total-BPA and phthalate metabolites were analyzed from urine samples.

RESULTS

Of the participants, 34 were evaluated as normal blood pressure profile, 33 as white-coat hypertension (WCHT), and 19 as ABPM-hypertension. Adolescents in ABPM- hypertension groups had higher BMI-standard deviation score (SDS), leucocyte, platelet count; but lower serum chloride, compared to the normal blood pressure profile group. The percentage of adolescents with detectable urinary mono-benzyl phthalate (MBzP) was higher in ABPM-hypertension (42.1%) and WCHT groups (33.3%), compared to the normal blood pressure profile group (5.9%, p = 0.004). Associations between MBzP and ABPM- hypertension and WCHT were remained after confounding factor adjustment. Adolescents with detectable MBzP levels had also higher "albumin-corrected calcium" and lower serum phosphate and "albumin-corrected calcium x phosphate product" compared to others. Adolescents with detectable urinary MBzP levels had higher blood pressure profiles in some 24-h (mean arterial pressure-SDS, systolic blood pressure-SDS), daytime (systolic blood pressure-SDS), and night-time (mean arterial pressure-SDS, systolic blood pressure-SDS, and diastolic blood pressure-SDS) measurements, compared to others. WCHT was found to be associated negatively with monomethyl phthalate and the sum of dibutyl phthalate metabolites and ABPM-HT with MCPP. There was no significant association between blood pressure profiles and free- and total-BPA status.

CONCLUSION

MBzP was associated with adverse blood pressure profiles in adolescence. Additive follow-up studies are necessary for cause-effect relations.

Admission Lower Serum Phosphate Ion Levels Predict Acute Hydrocephalus of Aneurysmal Subarachnoid Hemorrhage

Introduction: The relationship between serum phosphate ion (sPi) and the occurrence of acute hydrocephalus (aHCP) in aneurysmal subarachnoid hemorrhage (aSAH) remains largely unknown and controversial. The primary aim of this study was to investigate the association between sPi on admission and aHCP following aSAH.

Methods: The study included 635 patients over the age of 19 years diagnosed with aSAH in our institution from September 2012 to June 2018. Data on clinical characteristics, laboratory parameters, treatments, and outcomes were collected and analyzed. The association between lower sPi levels and aHCP was assessed in univariate and multivariate analyses. Propensity-score matching (PSM) analysis was performed to reduce significant differences in baseline characteristics between the aHCP group and non-HCP group.

Results: The overall incidence of aHCP following aSAH was 19.37% (123/512). Lower sPi levels were detected in patients with aHCP compared with those without [0.86 (0.67–1.06) vs. 1.04 (0.84–1.21) mmol/L] in the univariate analysis. In the multivariate analysis, lower sPi level, high modified Fisher (mFisher) grade, and high Hunt-Hess grade were associated with aHCP [odds ratios (OR) 1.729, 95% confidence interval (CI) 1.139–2.623, p = 0.01; mFisher OR 0.097,95% CI 0.055–0.172, p < 0.001; Hunt-Hess, OR 0.555, 95% CI 0.320–0.961, P = 0.036]. After PSM, the matched aHCP group had a significantly lower sPi level than the matched non-aHCP group [0.86 (0.67–1.06) vs. 0.94 (0.76–1.12) mmol/L, p = 0.044]. The area under the curve (AUC) of the sPi level and the logistic regression model based on these predictors (sPi, Hunt-Hess grade, and mFisher grade) was 0.667 and 0.840 (sensitivity of 88.6% and specificity of 68.4%) for predicting aHCP, respectively.

Conclusions: Lower sPi levels predict the occurrence of aHCP, and the model constructed by sPi levels, Hunt-Hess grade, and mFisher grade markedly enhances the prediction of aHCP after aSAH.

Hypophosphataemia is common in patients with aneurysmal subarachnoid haemorrhage

INTRODUCTION

Hypophosphataemia is common in critically ill patients, but neither its prevalence nor its association with outcome have been investigated specifically in patients with aneurysmal subarachnoid haemorrhage (aSAH).

METHODS

Patients with aSAH and at least one phosphate measurement were included from two independent cohorts; an American cohort extracted from two open-access databases (Medical Information Mart for Intensive Care-III and eICU Collaborative Research Database v. 2.0) and a Danish cohort consisting of patients with aSAH admitted to Rigshospitalet, Denmark over a 4-year period. In each cohort, we calculated the prevalence of mild (0.32-0.80 mmol/L) and severe (<0.32 mmol/L) hypophosphataemia and their association with in-hospital mortality before and after propensity-score matching.

RESULTS

Hypophosphataemia occurred in 72.4% (95% CI: 68.1-76.3) of patients in the American cohort (n = 471) and 54.9% (50.0-59.7) in the Danish cohort (n = 419). However, it was not associated with mortality in neither full (American: Mild, Odds ratio (OR) 0.99 (0.91-1.07), Severe OR 1.20 (0.95-1.51); Danish: Mild, OR 1.01 (0.95-1.08), Severe OR 1.20 (0.95-1.51)) nor propensity-score matched cohorts (American (n = 168): Mild, OR 1.06 (0.88-1.28), Severe OR 1.46 (0.96-2.12); Danish (n = 44): Mild, OR 1.16 (0.82-1.65), Severe OR 0.45 (0.13-1.55)).

CONCLUSION

In this retrospective study of patients with aSAH, hypophosphataemia was common.

Modulating phosphate consumption, a novel therapeutic approach for the control of cancer cell proliferation and tumorigenesis

Phosphorus, often in the form of inorganic phosphate (Pi), is critical to cellular function on many levels; it is required as an integral component of kinase signaling, in the formation and function of DNA and lipids, and energy metabolism in the form of ATP. Accordingly, crucial aspects of cell mitosis - such as DNA synthesis and ATP energy generation - elevate the cellular requirement for Pi, with rapidly dividing cells consuming increased levels. Mechanisms to sense, respond, acquire, accumulate, and potentially seek Pi have evolved to support highly proliferative cellular states such as injury and malignant transformation. As such, manipulating Pi availability to target rapidly dividing cells presents a novel strategy to reduce or prevent unrestrained cell growth. Currently, limited knowledge exists regarding how modulating Pi consumption by pre-cancerous cells might influence the initiation of aberrant growth during malignant transformation, and if reducing the bioavailability or suppressing Pi consumption by malignant cells could alter tumorigenesis. The concept of targeting Pi-regulated pathways and/or consumption by pre-cancerous or tumor cells represents a novel approach to cancer prevention and control, although current data remains insufficient as to rigorously assess the therapeutic value and physiological relevance of this strategy. With this review, we present a critical evaluation of the paradox of how an element critical to essential cellular functions can, when available in excess, influence and promote a cancer phenotype. Further, we conjecture how Pi manipulation could be utilized as a therapeutic intervention, either systemically or at the cell level, to ultimately suppress or treat cancer initiation and/or progression.

α 1-Adrenergic Receptor Blockade by Prazosin Synergistically Stabilizes Rat Peritoneal Mast Cells

BACKGROUND

Adrenaline quickly inhibits the release of histamine from mast cells. Besides β 2-adrenergic receptors, several in vitro studies also indicate the involvement of α-adrenergic receptors in the process of exocytosis. Since exocytosis in mast cells can be detected electrophysiologically by the changes in the membrane capacitance (Cm), its continuous monitoring in the presence of drugs would determine their mast cell-stabilizing properties.

METHODS

Employing the whole-cell patch-clamp technique in rat peritoneal mast cells, we examined the effects of adrenaline on the degranulation of mast cells and the increase in the Cm during exocytosis. We also examined the degranulation of mast cells in the presence or absence of α-adrenergic receptor agonists or antagonists.

RESULTS

Adrenaline dose-dependently suppressed the GTP-γ-S-induced increase in the Cm and inhibited the degranulation from mast cells, which was almost completely erased in the presence of butoxamine, a β 2-adrenergic receptor antagonist. Among α-adrenergic receptor agonists or antagonists, high-dose prazosin, a selective α 1-adrenergic receptor antagonist, significantly reduced the ratio of degranulating mast cells and suppressed the increase in the Cm. Additionally, prazosin augmented the inhibitory effects of adrenaline on the degranulation of mast cells.

CONCLUSIONS

This study provided electrophysiological evidence for the first time that adrenaline dose-dependently inhibited the process of exocytosis, confirming its usefulness as a potent mast cell stabilizer. The pharmacological blockade of α 1-adrenergic receptor by prazosin synergistically potentiated such mast cell-stabilizing property of adrenaline, which is primarily mediated by β 2-adrenergic receptors.

Changes in Serum Electrolytes, ECG, and Baroreflex Sensitivity during Combined Pituitary Stimulation Test

The mechanisms by which hypoglycemia increases cardiovascular mortality remain unclear. The aim of the study is to investigate changes in serum electrolytes, norepinephrine concentrations, electrocardiography, and baroreflex sensitivity (BRS) and associations between corrected QT (QTc) intervals and the changes in serum electrolytes during combined pituitary stimulation test (CPST). We recruited the subjects who were admitted to the Gyeongsang National University Hospital to undergo CPST between September 2013 and December 2014. Participants were 12 patients suspected of having hypopituitarism. Among 12 patients, cardiac arrhythmia in two patients occurred during hypoglycemia. There were significant differences in serum levels of potassium (P < 0.001), sodium (P = 0.003), chloride (P = 0.002), and calcium (P = 0.017) at baseline, hypoglycemia, and 30 and 120 minutes after hypoglycemia. Also, there was a significant increase in heart rate (P = 0.004), corrected QT (QTc) interval (P = 0.008), QRS duration (P = 0.021), and BRS (P = 0.005) at hypoglycemia, compared to other time points during CPST. There was a positive association between QTc intervals and serum sodium levels (P < 0.001) in 10 patients who did not develop arrhythmia during CPST. This study showed that there were significant changes in serum levels of potassium, sodium, chloride, and calcium, as well as heart rate, QTc interval, QRSd, and BRS during CPST. It was revealed that QTc intervals had a significant association with concentrations of sodium.

Hypophosphatemia after nontraumatic intracranial hemorrhage

BACKGROUND

The aim of this study was to assess the incidence and contributing factors of hypophosphatemia and the association with poor long-term outcome after nontraumatic intracranial hemorrhage.

METHODS

This was a prospective, observational study of patients with nontraumatic intracranial hemorrhage (i.e., aneurysmal or perimesencephalic subarachnoid hemorrhage, or spontaneous intracerebral or intraventricular hemorrhage) treated in the intensive care unit (ICU) at our university hospital. Plasma phosphate concentrations were measured serially in 2-day sections during the 6 day study period. The ICU mortality was recorded, 3-month and 1-year outcomes were assessed using the Glasgow Outcome Scale.

RESULTS

One hundred patients were enrolled. The frequency of hypophosphatemia (Pi ≤ 0.65 mmol/l) was 70%. Chronic hypertension, acute hydrocephalus, and diffuse brain edema were more common in patients with hypophosphatemia compared with normophosphatemics (44% vs. 21%, P = 0.021; 59% vs. 33%, P = 0.021; and 43% vs. 13%, P = 0.004, respectively). Hypophosphatemic patients had higher maximum SOFA scores [10 (7-11) vs. 7.5 (5.75-10), P = 0.024]. Initial phosphate concentration correlated inversely with APACHE II score on admission (ρ = -0.304, P = 0.002) and SOFA score on the first ICU day (ρ = -0.269, P = 0.008). There was no difference in outcome between hypophosphatemic and normophosphatemic patients. In all five patients with severe hypophosphatemia (Pi < 0.32 mmol/l) the functional outcome was good.

CONCLUSION

Hypophosphatemia was common in this patient population. The outcome was similar between hypophosphatemic and normophosphatemic patients. Chronic hypertension, acute hydrocephalus, diffuse brain edema and higher SOFA scores were more common in patients with hypophosphatemia.

Treatment of phosphorus balance disorders

Phosphorus (P) homeostasis in ruminants has received increased attention over the past decades. Although environmental concerns associated with excessive P excretion in cattle manure have led to incentives to lower dietary P intake, hypophosphatemia-particularly in the periparturient dairy cow-has been associated with conditions, such as the downer cow syndrome or postparturient hemoglobinuria. The objective of this article is to revisit current understanding of P homeostasis in ruminants, to discuss the pathophysiology and clinical presentation of P balance disorders, and to review different treatment approaches to correct imbalances of the body's P equilibrium.

Disturbance of inorganic phosphate metabolism in diabetes mellitus: its relevance to the pathogenesis of diabetic retinopathy

Early in the progression of diabetes, a paradoxical metabolic imbalance in inorganic phosphate (Pi) occurs that may lead to reduced high energy phosphate and tissue hypoxia. These changes take place in the cells and tissues in which the entry of glucose is not controlled by insulin, particularly in poorly regulated diabetes patients in whom long-term vascular complications are more likely. Various conditions are involved in this disturbance in Pi. First, the homeostatic function of the kidneys is suboptimal in diabetes, because elevated blood glucose concentrations depolarize the brush border membrane for Pi reabsorption and lead to lack of intracellular phosphate and hyperphosphaturia. Second, during hyperglycemic-hyperinsulinemic intervals, high amounts of glucose enter muscle and fat tissues, which are insulin sensitive. Intracellular glucose is metabolized by phosphorylation, which leads to a reduction in plasma Pi, and subsequent deleterious effects on glucose metabolism in insulin insensitive tissues. Hypophosphatemia is closely related to a decrease in adenosine triphosphate (ATP) in the aging process and in uremia. Any interruption of optimal ATP production might lead to cell injury and possible cell death, and evidence will be provided herein that such cell death does occur in diabetic retinopathy. Based on this information, the mechanism of capillary microaneurysms formation in diabetic retinopathy and the pathogenesis of diabetic retinopathy must be reevaluated.

Dynamics of blood electrolytes in repeated hyper- and/or hypoglycaemic events in patients with type 1 diabetes

AIMS/HYPOTHESIS

Electrolyte disturbances are well-known consequences of the diabetic pathology. However, less is known about the cumulative effects of repeated changes in glycaemia, a characteristic of diabetes, on the electrolyte balance. We therefore investigated the ionic profiles of patients with type 1 diabetes during consecutive hyper- and/or hypoglycaemic events using the glucose clamp.

METHODS

In protocol 1, two successive hyperglycaemic excursions to 18 mmol/l were induced; in protocol 2, a hypoglycaemic excursion (2.5 mmol/l) was followed by a hyperglycaemic excursion (12 mmol/l) and another hypoglycaemic episode (3.0 mmol/l).

RESULTS

Blood osmolarity increased during hyperglycaemia and was unaffected by hypoglycaemia. Hyperglycaemia induced decreases in plasma Na(+) Cl(-) and Ca(2+) concentrations and increases in K(+) concentrations. These changes were faithfully reproduced during a second hyperglycaemia. Hypoglycaemia provoked rapid and rapidly reversible increases in Na(+), Cl(-) and Ca(2+). In sharp contrast, K(+) levels displayed a rapid and substantial fall from which they did not fully recover even 2 h after the re-establishment of euglycaemia. A second hypoglycaemia caused an additional fall.

CONCLUSIONS/INTERPRETATION

Repeated hyperglycaemia events do not lead to any cumulative effects on blood electrolytes. However, repeated hypoglycaemias are cumulative with respect to K(+) levels due to a very slow recovery following hypoglycaemia. These results suggest that recurring hypoglycaemic events may lead to progressively lower K(+) levels despite rapid re-establishment of euglycaemia. This warrants close monitoring of plasma K(+) levels combined with continuous glucose monitoring particularly in patients under intensive insulin therapy who are subject to repeated hypoglycaemic episodes.

TRIAL REGISTRATION

Clinicaltrial.gov NCT01060917.

Lifestyle diseases and cardiovascular risk factors are interrelated to deficiencies of major substrates in ATP synthesis

Recent studies on diabetes and metabolic syndrome indicate a common disturbance of inorganic phosphate (Pi) metabolism. Pi is an important substrate in the formation of adenosine triphosphate (ATP), and many lifestyle diseases and cardiovascular risk factors similarly show deficiencies in either 1 or 2 major components of ATP synthesis. Age, male gender, hypertension, obesity, hypertriglyceridemia, metabolic syndrome, and diabetes mellitus are all associated with hypophosphatemia. In addition, tobacco smoking, hyperchylomicronemia, hypertension, and diabetes may involve defects in tissue oxygen delivery. Hypophosphatemia may lead to a critical decrease in intracellular Pi and to mitochondrial dysfunction, which might be counter-acted by the pharmacological use of fructose 1,6-diphosphate.

Medication-induced hypophosphatemia: a review

Hypophosphatemia (serum phosphorus concentration <2.5 mg/dl, 0.8 mmol/l), although rare in the general population, is commonly observed in hospitalized patients and may be associated with drug therapy. In fact, hypophosphatemia frequently develops in the course of treatment with drugs used in every-day clinical practice including diuretics and bisphosphonates. Proper diagnostic approach of patients with low serum phosphorus concentrations should involve a detailed medical history with special attention to the recent use of medications. The clinical manifestations of drug-induced hypophosphatemia are usually mild but might also be severe and potentially life-threatening. This review aims at a thorough understanding of the underlying pathophysiological mechanisms and risk factors of drug therapy-related hypophosphatemia thus allowing prevention and effective intervention strategies.

Serum phosphate in white-coat hypertensive patients: focus on dipping status and metabolic syndrome

Recent studies indicate an association between serum phosphate levels and blood pressure in hypertensive patients. A growing body of evidence suggests that white-coat hypertension (WCH) is associated with target organ damage. Furthermore, metabolic syndrome (MS) and a non-dipping pattern are associated with increased cardiovascular risk. The purpose of this study was to explore the nocturnal blood pressure fall in patients with WCH according to their serum phosphate levels and number of MS components fulfilled. The study included 2600 patients with WCH who attended our outpatient clinics. All patients underwent repeated office blood pressure measurements, 24-h ambulatory blood pressure monitoring and full clinical and laboratory evaluation. The diagnosis of MS was made according to the Adult Treatment Panel III criteria. Dipping pattern was defined as follows: 'dippers' had a nocturnal systolic blood pressure (NSBP) fall > or =10% but <20%; 'non-dippers' had an NSBP fall <10%; 'extreme dippers' had an NSBP fall > or =20% and 'reverse dippers' had an NSBP increase. There were 314 extreme dippers, 1337 dippers, 734 non-dippers and 116 reverse dippers. Reverse dippers presented with significantly lower levels of serum phosphate, whereas extreme dippers had significantly higher levels (3.39+/-3.29 vs. 3.58+/-3.52 mg per 100 ml, P<0.0001). The patients were classified according to the number of MS components and the main observation was the inverse relationship of serum phosphate with MS components (3.53+/-0.36, 3.50+/-0.38, 3.49+/-0.38, 3.44+/-0.36 and 3.35+/-0.31 mg per 100 ml, respectively, P=0.003). Patients with WCH and low serum phosphate levels appear to have a higher incidence of a non-dipping NSBP profile and an impaired metabolic profile. This observation may be important for the stratification of the cardiovascular risk in WCH patients.

Influence of traumatic brain injury on potassium and phosphorus homeostasis in critically ill multiple trauma patients

OBJECTIVE

The intent of this study was to ascertain whether multiple trauma patients with traumatic brain injury (TBI) had lower serum concentrations of potassium and phosphorus and required more aggressive supplementation than multiple trauma patients without TBI.

METHODS

Ventilator-dependent adult patients without renal impairment who were admitted to the trauma intensive care unit or neurosurgical intensive care unit and who received enteral nutrition were evaluated for the first 14 d after hospital admission. Patients were grouped according to the presence or absence of TBI. Target serum concentrations for potassium and phosphorus were 4 mEq/L and 4 mg/dL, respectively. Electrolyte repletion therapy was given according to the nutritional support service guidelines.

RESULTS

Fifty trauma patients (25 with and without TBI) were studied. Daily serum potassium concentrations were consistently lower for those with TBI (P < or = 0.001), whereas the mean net potassium intake was greater (1.3 +/- 0.5 versus 0.7 +/- 0.3 mEq x kg(-1) x d(-1), respectively, P < or = 0.001). Serial serum phosphorus concentrations were similar between groups (P = NS) except for a significantly lower serum phosphorus concentration for trauma patients with TBI on day 3 after hospital admission (2.5 +/- 0.5 versus 2.9 +/- 0.7 mg/dL, respectively, P < or = 0.05). However, the mean net phosphorus intake was significantly greater for trauma patients with TBI (0.65 +/- 0.25 versus 0.45 +/- 0.17 mmol x kg(-1) x d(-1), P < or = 0.001).

CONCLUSION

Potassium and phosphorus requirements are greater for multiple trauma patients with TBI compared with those without TBI.

Serum phosphate and sympathetic tone in mild essential hypertension

Forty-year old, normocalcaemic men with mild essential hypertension (n = 35) had decreased serum phosphate (p less than 0.001) concomitant with elevated plasma adrenaline (p less than 0.03) and heart rate (p less than 0.001). All had unchanged serum immunoreactive parathyroid hormone concentrations compared to age-matched normotensive control men (n = 44). Serum phosphate levels correlated negatively with plasma adrenaline (p less than 0.05), plasma noradrenaline (p less than 0.05), mean blood pressure (p less than 0.001) and heart rate (p less than 0.05). Serum phosphate was significantly lowered by infusion of small amounts of adrenaline at all four infusion rates in a hypertensive group (n = 12) while a similar effect was obtained only at the two highest infusion rates in a normotensive group (n = 10). No change in serum calcium was observed in either group. Thus, hypophosphataemia appears to be inversely related to sympathetic tone in essential hypertension.

Serum phosphate increase during short-term beta-adrenoceptor blockade in thyrotoxicosis

We studied the changes in blood plasma electrolytes during acute and short-term treatment with four different beta-adrenergic-blocking agents in 31 patients with hyperthyroidism. Serum phosphate increased during the first four hours and remained elevated after one week both after cardioselective (acebutolol) and non-cardioselective (oxprenolol, pindolol and timolol) beta-blockade (p less than 0.05). Albumin decreased after four hours but no change was found after one week. Serum creatinine increased after one week in the acebutolol-treated group, while sodium, potassium and albumin-corrected calcium in serum did not change. The hyperphosphatemic effect may be due to blockade of beta 1-adrenoceptors, since the effect of the cardioselective acebutolol was no less than that of the non-cardioselective beta-adrenoceptor blockers.

Plasma potassium and phosphate concentrations--influence by adrenaline infusion, beta-blockade and physical exercise

Infusion of adrenaline into healthy male subjects reduced the plasma concentrations of both potassium and phosphate to a similar extent, in a dose-dependent manner, an effect which was prevented by the administration of propranolol. Ergometer bicycling until exhaustion, which caused marked accumulation of lactic acid in the blood and reduction of pH, induced great elevations of both plasma potassium and phosphate with close relationships between the raised plasma concentrations and the reduction in pH, also during beta-blockade. However, longer-term aerobic exercise, without acidosis, also caused some rise of the potassium and phosphate concentrations. During recovery from anaerobic, but not from aerobic, exercise there was a rapid decrease of the plasma potassium levels while the phosphate values normalized gradually together with pH. From measurements of the ion concentrations both in the femoral effluent of one leg, which carried out maximal isokinetic work, and in the opposite antecubital vein it could be calculated that there was for potassium, but not for phosphate, a post-exercise uptake both in the exercised muscle and in the entire organism, indicating the participation of systemic factors.

Serum phosphate, blood pressure, and the metabolic syndrome--20-year follow-up of middle-aged men

The authors investigated the relationship between serum phosphate (S-phosphate) and the metabolic syndrome in a group of middle-aged hypertensive and normotensive men during 20-year follow-up. Fifty-six men participated. Of the original 34 normotensive men, hypertension developed in 17. In the group as a whole and in those in whom hypertension developed, there was a significant negative relationship between S-phosphate at baseline and mean blood pressure (MBP) at follow-up. A significant relationship was observed between S-phosphate at baseline and components of the metabolic syndrome in the group as a whole, in individuals with hypertension, and in individuals with the lowest S-phosphate levels at follow-up. S-phosphate at baseline predicted MBP 20 years later in a group of hypertensive and normotensive men. When grouped according to the number of components of the metabolic syndrome, individuals with the lowest serum phosphate levels had the highest number of risk factors. These findings may suggest a role of low S-phosphate in the development of hypertension and the metabolic syndrome.

Electrolyte disturbances in the intensive care unit

The development of many electrolyte disturbances in the ICU can be prevented by attention to the use of intravenous fluids and nutrition. Hyponatremia is a relative contraindication to the use of hypotonic intravenous fluids and hypernatremia calls for the administration of water. Formulae have been devised to guide the therapy of severe hyponatremia and hypernatremia. All formulae regard the patient as a closed system, and none takes into account ongoing fluid losses that are highly variable between patients. Thus, therapy of severe hyponatremia and hypernatremia must be closely monitored with serial electrolyte measurements. The significance of hypocalcemia in the critically ill is controversial. Hypokalemia, hypophosphatemia, and hypomagnesemia should be corrected.

Risk factors for gastrointestinal complications in critically ill children with transpyloric enteral nutrition

OBJECTIVE

To study the risk factors for gastrointestinal complications related to enteral nutrition in critically ill children.

DESIGN

A prospective, observational study.

SETTING

Pediatric intensive care unit.

SUBJECTS

Five hundred and twenty-six critically ill children who received transpyloric enteral nutrition(TEN).

METHODS

Univariate and multivariate logistic regression analysis were used to identify risk factors for gastrointestinal complications.

RESULTS

Sixty six patients (11.5%) presented gastrointestinal complications, 33 (6.2%) abdominal distension and/or excessive gastric residue, 34 (6.4%) diarrhea, one gastrointestinal bleeding, three necrotizing enterocolitis and one duodenal perforation. Enteral nutrition was definitively suspended because of gastrointestinal complications in 11 (2.1%) patients. Fifty patients (9.5%) died. Gastrointestinal complications were more frequent in the patients who died. Death was related to complications of the nutrition in only one patient. The frequency of gastrointestinal complications was significantly higher in children with shock, acute renal failure, hypokalemia, hypophosphatemia and in those receiving dopamine, epinephrine and vecuronium. The stepwise multivariate logistic regression analysis showed that the most important factors associated with gastrointestinal complications were shock, epinephrine at a rate higher than 0.3 microg/kg/min and hypophosphatemia.

CONCLUSIONS

The tolerance of TEN in critically ill children is good, although the incidence of gastrointestinal complications is higher in patients with shock, acute renal failure, hypokalemia, hypophosphatemia, and those receiving epinephrine, dopamine, and vecuronium.

Serum biochemical abnormalities in goats with uroliths: 107 cases (1992–2003)

OBJECTIVE

To characterize serum biochemical abnormalities in goats with uroliths.

DESIGN

Retrospective case-control series.

ANIMALS

107 male goats with uroliths and 94 male goats with various nonrenal diseases (controls).

PROCEDURES

For male goats, results of serum biochemical analyses collected from 1992 through 2003 were retrieved from computerized records, as were signalment, clinical diagnoses, and discharge status. Results of analyses for BUN, creatinine, phosphorus, calcium, Na, K, Cl, total CO2, anion gap, and glucose were compared between goats with uroliths and control goats.

RESULTS

Goats with uroliths had higher mean BUN, creatinine, total CO2, K, and glucose concentrations and lower mean phosphorus, Na, and Cl concentrations than control goats, with no difference in mean calcium concentration and anion gap. Goats with uroliths had higher frequency of azotemia, hypophosphatemia, hypochloridemia, and increased total CO2 and lower frequency of decreased total CO2 than control goats. Urolithiasis occurred more frequently in castrated males than in sexually intact males and in dwarf African breeds than in other breeds.

CONCLUSIONS AND CLINICAL RELEVANCE

Goats with uroliths often had hypophosphatemia at admission. Hypochloridemic metabolic alkalosis was the most common acid-base disorder. Rupture in the urinary tract system was associated with increased prevalence of hyponatremia and hyperkalemia. Clinicians should be aware of these abnormalities when determining fluid therapy.

Hypophosphataemia causing profound cardiac failure after cardiac surgery

We report the case of a patient who developed severe cardiac failure after cardiac surgery and required high-dose inotrope infusion. The patient was found to have significant hypophosphataemia and high insulin requirements immediately after surgery. On giving intravenous phosphate, there was a rapid decrease in inotrope requirement and improved glycaemic control. This occurrence raises questions about the cause of hypophosphataemia after cardiac surgery, the possible need for pre-operative plasma phosphate measurement and whether phosphate replacement should be part of the standard management of postoperative hypophosphataemia.

Thyrotoxic periodic paralysis and anesthesia report of a case and literature review

Thyrotoxic periodic paralysis (TPP) is a disease characterized by recurrent episodes of paralysis and hypokalemia during a thyrotoxic state. The disease primarily affects people of Asian descent, but can affect other ethnic groups. In Asians, the symptoms of thyrotoxicosis are distinct and usually precede the first paralytic episode, whereas in non-Asian populations, paralysis is the presenting symptom. If TPP has not been diagnosed and the patient has a surgical procedure during general or regional anesthesia, symptoms of the disease may be confused with other adverse perioperative events such as delayed recovery from neuromuscular paralysis. No specific anesthetic regimen is superior. Current TTP treatment recommendations involve treating the underlying hyperthyroid state. Other modalities such as beta-blockade and potassium replacement are also important in the acute paralytic state. Future diagnostic and treatment innovations may lie in the genetic and molecular understanding of this disease. We present a case of an Asian male with known TPP undergoing general anesthesia, a brief case series involving 5 patients, and a review of the literature.

Diagnosing thyrotoxic periodic paralysis in the ED

Thyrotoxic periodic paralysis (TPP) and sporadic periodic paralysis (SPP) are the most common causes of hypokalemic periodic paralysis (HPP) in EDs in Asia. Their neuromuscular presentations are almost indistinguishable. We conducted this study to identify clinical clues that can help EPs distinguish between TPP and SPP. Thirty-four patients presenting to the ED with HPP were enrolled during a 3-year period. They did not have known hyperthyroidism before the attack and no family history of paralysis. They all had low K(+) excretion rates. Vital signs and blood biochemistry, including acid-base and electrolytes, were measured. TPP was subsequently established by thyroid function tests. Twenty patients had TPP and 14 patients had SPP. There was no significant difference in age and sex distribution between them. Systolic (SBP) but not diastolic blood pressure (SBP 145 +/- 4 vs 128 +/- 4 mm Hg, P < 0.001) and heart rate (106 +/- 3 vs 73 +/- 3 beats/min, P < 0.001) were significantly higher in those experiencing TPP than SPP. Among the biochemical factors, only plasma phosphate concentration (2.2 +/- 0.2 vs 3.2 +/- 0.2 mg/dL, P < 0.001) was significantly lower in those experiencing TPP than SPP. Systolic hypertension, tachycardia, and hypophosphatemia are clinical clues favoring the diagnosis of TPP.

Acute changes of bone turnover and PTH induced by insulin and glucose: euglycemic and hypoglycemic hyperinsulinemic clamp studies

Bone turnover is acutely suppressed after feeding or oral glucose. Insulin infusion suppresses bone turnover and might mediate this effect, but this is confounded by a possible direct effect of hypoglycemia. We examined the effect of euglycemic hyperinsulinemia and hypoglycemic hyperinsulinemia on bone turnover using an insulin clamp. Sixteen men participated in this double-blind crossover study. Clamp induction involved infusion of insulin (80 mU/m(2).min) while maintaining euglycemia (5 mmol/liter) for 40 min with a variable rate dextrose infusion. Glucose was lowered to 2.5 mmol/liter (hypoglycemic clamp) or maintained at 5 mmol/liter (euglycemic clamp) for a further 105 min. Nine controls received a matched saline infusion. Measurements included serum C-terminal telopeptide of type I collagen, procollagen type I N-terminal propeptide, osteocalcin, and PTH. Induction of hyperinsulinemia resulted in a reduction in PTH (27% +/- 5; P < 0.01), but no significant change in bone turnover from baseline. Hypoglycemic clamp resulted in suppression of serum C-terminal telopeptide of type I collagen by 34% +/- 3, procollagen type I N-terminal propeptide by 15% +/- 1, osteocalcin by 5% +/- 1, and PTH by a further 12% +/- 5 (all P < 0.05). By contrast, there was no significant change in any marker of bone turnover during euglycemic clamp. Postprandial hyperinsulinemia is unlikely to explain the acute suppression of bone turnover with feeding. The reduction in bone turnover during hypoglycemia may be related to hypoglycemia itself, acute changes in PTH, or other hormones released in response to hypoglycemia.

Phosphate supplementation for hypophosphataemia and parenteral nutrition

Routine detection and treatment of acute hypophosphataemia is important in intensive care unit and many other hospitalized patients, but metabolic bone disease and hypophosphataemia are still experienced as a result of parenteral nutrition. A significantly common problem that faces the compounding pharmacist when formulating parenteral nutrition regimens is the difficulty associated with the successful avoidance of calcium phosphate precipitation. Although incorporation of the normal calcium and phosphate requirements into regimens for metabolically stable adults is usually achievable, it can prove impossible in paediatric and neonatal mixtures when using the standard inorganic sources that are currently licensed for use in the UK and USA. In other countries, where organic compounds are routinely available, this problem does not exist.

Hypokalemic periodic paralysis associated with hypophosphatemia in a patient with hyperinsulinemia

A 34-year-old man was admitted to the hospital because of acute quadriplegia. On admission, serum potassium was 2.1 mEq/L and serum inorganic phosphate was 1.4 mg/dL. Thyroid function was normal. Serum levels of aldosterone, cortisol, and intact parathyroid hormone were normal. Fasting plasma glucose was 109 mg/dL, and fasting serum insulin was 25.0 U/mL. Shortly after intravenous supplementation of potassium, muscle strength was normalized. Oral glucose tolerance test revealed impaired glucose tolerance and hyperresponse of insulin. During the oral glucose tolerance test, serum potassium and phosphate decreased significantly. These findings suggest that hyperinsulinemia and insulin-induced transmembrane shift of extracellular potassium and phosphate may have been involved in the abnormalities of serum electrolytes and development of hypokalemic periodic paralysis in the present patient.

Hypophosphataemia. Pathophysiology, effects and management on the intensive care unit

Routine detection and treatment of hypophosphataemia on the intensive care unit is commonplace. Hypophosphataemia has been associated with a multitude of clinical effects and there are many associations between correction of hypophosphataemia and improvement in symptoms. However, there is no evidence at present to support the routine correction of hypophosphataemia in the absence of clinical symptoms or signs.

Effects of increased arterial epinephrine on insulin, glucose and phosphate

The relationship between sympathetic nervous system activity and glucose and insulin metabolism is not fully understood. In the present study we therefore investigated the effect of raising arterial plasma epinephrine within the lower pathophysiological concentration range on insulin, glucose and phosphate in blood. Arterial plasma epinephrine was raised over 60 min by a stepwise increasing intravenous infusion in healthy men aged 20-40 years (n = 40). Compared with infusion of saline, epinephrine caused a small but significant rise in serum insulin of 10 +/- 26 pmol/L (p = 0.016), more than 70% increase in serum glucose (p < 0.0001) and a decrease in serum phosphate (p < 0.0001). The changes in serum insulin during epinephrine infusion correlated negatively with the changes in arterial plasma epinephrine (r = -0.46, p = 0.003) and the changes in serum phosphate correlated negatively with the changes in serum glucose (r = -0.42, p = 0.007). Thus, arterial plasma epinephrine raised within the lower pathophysiological concentration range over a rather short period of time (60 min) has pronounced effects on insulin, glucose and phosphate in blood. These results suggest that epinephrine when infused acutely may suppress the insulin response to raised glucose, and that the acute hypophosphatemic effect of epinephrine is related to the glucose production. Thus, when epinephrine is released into the circulation during various forms of daily stress, e.g. mental stress, it may significantly affect insulin and glucose metabolism.

Effect of dextroamphetamine and methylphenidate on calcium and magnesium concentration in hyperactive boys

Levels of calcium in plasma, red blood cells, and mononuclear blood cells, levels of calcium in plasma, and the plasma calcium-to-magnesium ratio were measured at baseline and after 3 weeks of each drug phase of a double-blind, placebo-controlled study of methylphenidate and dextroamphetamine in hyperactive boys. Levels of magnesium in plasma were significantly higher after 3 weeks of dextroamphetamine treatment, and the calcium-to-magnesium ratio was significantly lower after 3 weeks of either drug compared with the baseline or placebo condition. There was no change in magnesium levels in red blood cells or mononuclear blood cells. These measures were obtained 30 minutes before the morning dose and at 9 a.m., 9:30 a.m., 10:30 a.m., 11:00 a.m., and noon on the last day of each 3-week phase. Analysis of variance revealed a drug effect on plasma magnesium and on the calcium-to-magnesium ratio but no drug x time interaction. Although these changes were not correlated with the time course of acute symptomatic response to stimulant therapy, the decrease in the ratio may be relevant to side effects and treatment resistance associated with stimulant use.

Parathyroid hormone in blood pressure and volume homeostasis in healthy subjects, hyperparathyroidism, liver cirrhosis and glomerulonephritis. A possible interaction with angiotensin II and atrial natriuretic peptide

In order to elucidate a participation of intact parathyroid hormone (PTH(1-84)) in blood pressure (BP) and body fluid homeostasis, we studied fluctuations of PTH(1-84) during manipulations of BP in hyperparathyroid and healthy subjects, and during manipulations of blood volume in patients with glomerulonephritis or liver cirrhosis and in controls. Angiotensin II induced BP elevation was associated with increased values of PTH(1-84) both in healthy subjects (12-25 ng l-1, medians, p < 0.01), in patients with primary hyperparathyroidism (94-125 ng l-1, p < 0.01), in patients with low calcium due to end stage renal disease before requirement of dialysis (95-151 ng l-1, p < 0.02), and in patients with tertiary hyperparathyroidism (221-264 ng l-1, p < 0.05), but not in dialysis patients without hypercalcaemia (126-174 ng l-1, NS). The changes could not be attributed to reduction of serum calcium, but probably to the increase of plasma angiotensin II, which was positively correlated to the increase of serum PTH(1-84) in the healthy subjects (p = 0.619, n = 15, p < 0.05) and in the patients with primary hyperparathyroidism (p = 0.549, n = 18, p < 0.05). Noradrenaline induced BP elevation did not have a similar effect on PTH(1-84), and changes of PTH(1-84) were not related to changes of BP. Volume depletion after furosemide injection, also accompanied by increased levels of angiotensin II, resulted in elevation of PTH(1-84) in controls, cirrhotics, patients with glomerulonephritis without the nephrotic syndrome, but not in nephrotic patients. Volume depletion induced by bolus injection of atrial natriuretic peptide (ANP) was associated with decreased PTH(1-84) in healthy subjects (20-18 ng l-1, p < 0.02), but not in patients with nephrotic syndrome and liver cirrhosis. Volume expansion induced by albumin infusion caused increased plasma levels of ANP, but PTH(1-84) was unaltered. Thus, angiotensin II may be able to stimulate, and ANP to inhibit release of PTH(1-84), and PTH(1-84) may be involved in the regulation of BP and body fluid homeostasis. BP changes or changes in blood volume per se do not seem to influence PTH(1-84) levels.

Sympathetic nervous system involvement in essential hypertension: increased platelet noradrenaline coincides with decreased beta-adrenoreceptor responsiveness

Platelet catecholamine content may reflect integrated plasma catecholamine concentrations over time. The present study aimed at examining sympathetic nervous system (SNS) involvement in essential hypertension by assessing platelet noradrenaline (NA) and typically beta-adrenoreceptor mediated responses to adrenaline (A) infusion as indices of sympathetic tone. Healthy white men were recruited by public advertising and screening (mean +/- SD): Hypertensives (n = 13, sitting blood pressure [BP] 153 +/- 13/106 +/- 7 mmHg, age 34 +/- 5 years, weight 83 +/- 10 kg) were compared to normotensives (n = 13, sitting BP 114 +/- 9/75 +/- 9 mmHg, age 30 +/- 6 years [n.s.], weight 82 +/- 9 kg [n.s.]). Loss of platelet granular contents (including NA) prior to analysis was minimized by studying young subjects (age range 20-40 years, minimal atherosclerosis), using arterial blood sampling, and processing blood immediately. These procedures resulted in plasma beta-thromboglobulin and platelet factor 4 levels which were not significantly different between groups. Sympathetic activation resulting from stress was minimized by not labelling subjects as either hypertensive or normotensive. Mean arterial platelet NA content was significantly higher in hypertensives (64 +/- 31 pg/mg of platelet weight) compared to normotensives (43 +/- 20 pg/mg, p < 0.05) both at baseline and following 35% expansion of the circulating platelet pool by A infusion (p < 0.05) and correlated with arterial NA in the hypertensives (r = 0.79, p < 0.002) but not in the normotensives (r = 0.04, n.s.). Similar increases in platelet and plasma A during infusion in both groups suggest unchanged platelet uptake capacity and plasma clearance in the hypertensive group.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug- and nutrition-induced hypophosphatemia: mechanisms and relevance in the critically ill

OBJECTIVE

To provide an outline of the drugs and nutritional therapy that could contribute to the development of hypophosphatemia in the critically ill patient.

DATA SOURCES

Computerized abstracting services, references to primary literature articles, and review publications were screened for references to drug- or nutrition-related hypophosphatemia.

STUDY SELECTION

Studies primarily describing responses in adults were selected. Animal research is described that illustrates findings in humans.

DATA EXTRACTION

Information was abstracted from the findings of individual case reports and clinical trials.

DATA SYNTHESIS

Data are organized by mechanism of possible effect on serum phosphate concentration. No reference is made to drugs that do not have an effect on phosphate metabolism.

CONCLUSIONS

Hypophosphatemia can have significant effects that would hinder recovery of the critically ill patient. Antacids, catecholamines, beta-adrenergic agonists, sodium bicarbonate, and acetazolamide are commonly used therapeutic agents that could contribute significantly to the development of hypophosphatemia. Provision of nutrition to the chronically malnourished individual or chronic administration of phosphate-depleted parenteral nutrition could produce symptoms associated with hypophosphatemia. Other drugs could have a mild effect on lowering serum phosphate concentrations, but would be unlikely to produce symptoms unless combined with other etiologies of hypophosphatemia.

Magnesium sulfate potentiates several cardiovascular and metabolic actions of terbutaline

beta-Adrenergic agonists are useful for the emergency treatment of asthma. Recently, magnesium sulfate (MgSO4) has also been shown to be efficacious in this situation. beta-Agonists have unwanted cardiovascular and metabolic actions: increased systolic blood pressure, corrected QT interval (QTc), serum glucose and insulin, and decreased RR interval, diastolic blood pressure, serum potassium, phosphate, and calcium. As beta-agonists and MgSO4 quite possibly will be used in combination, we sought to determine how MgSO4 would affect these actions. Healthy young male adults were administered two doses of terbutaline sulfate, 0.25 mg subcutaneously, 30 min apart on two separate occasions, in a randomized, double-blind fashion. On one occasion, 4 g of MgSO4 was administered intravenously over the same 30-min period. On the other, normal saline solution was given as a placebo. Cardiovascular and metabolic variables were measured sequentially for 2 h. Data at 60 min with p values given for a summation of all time points are as follows: MgSO4 increased terbutaline's effects on the RR interval by 0.09 s, p < 0.0001; QTc interval by 0.01 s, p < 0.0007; diastolic blood pressure by 8 mm Hg, p = 0.0001; serum calcium by 0.13 mg/dl, p = 0.01; and glucose by 9 mg/dl, p < 0.0001. MgSO4 also mitigated the systolic blood pressure elevating the effect of terbutaline by 5 mm Hg (p = 0.007). The magnitude of the response potentiations was modest. We conclude that combining terbutaline and MgSO4 is unlikely to result in serious short-term adverse events, if used acutely in patients with relatively normal cardiac and metabolic function. MgSO4 may act by potentiating the effect of beta-agonists on magnesium requiring enzymes such as adenyl cyclase.

Adrenergic modulation of extrarenal potassium disposal in men with end-stage renal disease

In normal subjects, beta-adrenergic stimulation lowers the serum potassium, whereas alpha-stimulation raises it. Epinephrine, a mixed alpha and beta agonist, acutely lowers the blood potassium in normal subjects, but not in patients with end-stage renal disease. This study was designed to determine whether the resistance to the hypokalemic effect of epinephrine in dialysis patients is due to a blunted beta-adrenergic response, or to an augmented alpha-adrenergic response. The infusion of epinephrine at low doses (0.01 microgram/kg/min) produced a significant increase in serum potassium in hemodialysis patients (+0.21 +/- 0.07 mmol/liter, P less than 0.05), as compared to a nonsignificant decrease (-0.06 +/- 0.04 mmol/liter) in normal subjects. Epinephrine at high physiologic doses (0.04 microgram/kg/min) failed to significantly change the serum potassium in the dialysis patients (-0.10 +/- 0.14 mmol/liter), but substantially lowered serum potassium in the controls (-0.64 +/- 0.10 mmol/liter, P less than 0.001). There was no significant correlation (r = 0.03) between the baseline serum potassium concentration and the magnitude of change during epinephrine infusion. Epinephrine infusion (0.04 microgram/kg/min) during beta-blockade with propranolol produced a greater rise in serum potassium in the dialysis patients as compared to the controls (+0.69 +/- 0.11 vs. +0.32 +/- 0.11 mmol/liter, P less than 0.05). Epinephrine infusion (0.01 microgram/kg/min) during alpha-blockade with phentolamine resulted in similar changes in serum potassium in dialysis patients and in normal control (-0.10 +/- 0.12 vs. -0.10 +/- 0.06 mmol/liter). Moreover, phentolamine reversed the increase in serum potassium observed in dialysis patients during the infusion of epinephrine following beta-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal phosphate transport in spontaneously hypertensive rats and genetically matched controls

Hypophosphatemia has been documented in patients with hypertension and in spontaneously hypertensive rats compared with genetically matched control Wistar-Kyoto rats. However, renal tubular reabsorption is increased in spontaneously hypertensive rats. Therefore, it was hypothesized that decreased serum phosphate levels in spontaneously hypertensive rats may be related to a decrease in the intestinal transport of phosphate. To test this hypothesis, sodium-dependent phosphate uptake by jejunal brush-border membrane vesicles of spontaneously hypertensive rats and genetically matched Wistar-Kyoto rats was determined. Phosphate uptake consisted of two components: sodium-independent passive diffusion across the brush border and sodium-dependent, carrier-mediated uptake. The initial rate of uptake in spontaneously hypertensive and Wistar-Kyoto rats was linear up to 20 seconds. The initial rate and time course of jejunal sodium-dependent phosphate uptake was decreased in adult spontaneously hypertensive rats compared with corresponding mean values in Wistar-Kyoto rats. This decrease was secondary to a decrease in Vmax rather than Km, suggesting tha the number and/or the activity of the sodium-phosphate transporters is decreased. Sodium-dependent phosphate uptake was pH dependent, with greater uptake at pH 6.0 than at pH 7.4. However, uptake values were lower in spontaneously hypertensive rats than in Wistar-Kyoto rats at all pH levels tested. In contrast, sodium-dependent phosphate uptake in weanling rats (prehypertensive state) was not significantly different between spontaneously hypertensive and Wistar-Kyoto rats. Vitamin D deficiency in both spontaneously hypertensive and Wistar-Kyoto rats decreased Vmax and Km of sodium-dependent phosphate uptake, whereas 1,25(OH)2 vitamin D3 administration increased Vmax and Km in both spontaneously hypertensive and Wistar-Kyoto rats. These results suggest that the hypophosphatemia seen in adult spontaneously hypertensive rats is secondary to a decrease in sodium-dependent phosphate uptake compared with controls. The sodium phosphate transporter in spontaneously hypertensive rats is responsive to vitamin D administration.

Platelet and plasma catecholamines in relation to plasma minerals and parathyroid hormone following acute myocardial infarction

Epinephrine has been shown to lower the plasma concentrations of several minerals and elevate those of parathyroid hormone (PTH). In order to evaluate the possible clinical importance of such experimental observations, 34 patients with acute myocardial infarction (AMI) were studied with daily determinations of plasma catecholamines, minerals, and PTH during the first week after AMI and at follow-up one month later. In addition, platelet catecholamines were determined as they fluctuate more slowly than plasma catecholamines. After infarction initial platelet epinephrine and norepinephrine levels were higher (p less than 0.05 for both) in nonsurvivors than survivors during a one year follow-up. Results suggested that activation of the sympathoadrenal system influences calcium homeostasis following AMI, but that the impact of sympathoadrenal activation on mineral metabolism is of minor clinical significance in the average AMI patient. High platelet catecholamine levels may predict a poor outcome after AMI.

Hypophosphatemia in course of chronic obstructive pulmonary disease. Prevalence, mechanisms, and relationships with skeletal muscle phosphorus content

Serum phosphorus levels (Ps), dietary intake of phosphorus, and renal phosphate handling indexes were evaluated in 158 patients with chronic obstructive pulmonary disease (COPD) of varying degrees of severity; moreover, skeletal muscle phosphorus content (Pm) was measured in muscle samples obtained by quadriceps femoris needle biopsy in 14 of the same patients. Hypophosphatemia (Ps less than or equal to 2.5 mg/dl) was found in 34 (21.5 percent) of 158 patients without differences between groups of COPD patients presenting increasing severity of respiratory illness. No relationship was found between serum levels and dietary intake of phosphorus; hypophosphatemia was associated with low renal phosphate threshold (TmPO4/GFR) values in 31 (91 percent) of 34 patients. The prevalence of hypophosphatemia was significantly higher among COPD patients taking one or more drugs commonly used in COPD and known as negatively influencing renal phosphate handling: xanthine derivatives, corticosteroids, loop diuretics, and beta 2-adrenergic bronchodilators. Short-term administration of therapeutic doses of these drugs in COPD patients previously not taking any drug reduced TmPO4/GFR values; phosphaturic effect of short-term theophylline administration on renal phosphate handling was additive to that of long-term assumption of the drug. Muscle phosphorus content was both reduced in COPD patients as compared with control subjects and significantly correlated to serum phosphorus levels and to TmPO4/GFR values. The present investigation revealed a high prevalence of hypophosphatemia among COPD patients as well as a defect in renal phosphate reabsorption secondary, at least in part, to pharmacologic therapy. Moreover, it also suggests that in COPD patients muscle phosphorus content is likely to be reduced in presence of hypophosphatemia.

Metabolic, electrocardiographic, and hemodynamic responses to increased circulating adrenaline: effects of selective and nonselective beta adrenoceptor blockade

Twelve healthy male volunteers were given adrenaline infusions, 0.05 microgram/kg body weight/minute over one hundred twenty minutes (min), in order to achieve serum adrenaline concentrations comparable with those seen in acute myocardial infarction. The infusions were given on three occasions, at intervals of at least four weeks. Before the infusions the subjects were given, in random order, two days' pretreatment with placebo, a beta-1-selective adrenoceptor blocker (atenolol), or a nonselective beta blocker (propranolol) with each subject receiving each pretreatment. Six of the volunteers also had a fourth adrenaline infusion, after two days' pretreatment with a beta-2-selective beta blocker, ICI 118551. Adrenaline increased heart rate by 11 beats/min, increased systolic blood pressure by 10 mmHg, and decreased diastolic blood pressure by 15 mmHg. These changes were partly prevented by atenolol. Propranolol and ICI 118551 partly prevented the rise in systolic blood pressure but differed from atenolol in their effects on heart rate and diastolic blood pressure, causing falls in heart rate by 7 beats/min and 12 beats/min respectively, secondary perhaps to increases in diastolic blood pressure by 13 mmHg and 17 mmHg respectively. Adrenaline caused a prolongation of QTc duration by 0.03 second and a flattening of the T-wave amplitude by 1.04 mm. These changes in cardiac repolarization were partly inhibited by atenolol, but the effects of propranolol and ICI 118551 were greater, each causing a reduction of QTc and an increase in T-wave amplitude. During adrenaline infusion S-potassium declined by 0.60 mmol/L, S-magnesium by 0.05, S-calcium by 0.10, and S-phosphate by 0.24, but S-free fatty acids increased nearly threefold. All these changes were statistically significant and were presumably mediated mainly by the beta-2-adrenoceptor, for they were blocked more effectively by the beta-2-adrenoceptor blockers than by the selective beta-1-adrenoceptor blocker. B-glucose increased by 4.1 mmol/L, the increase being practically unaffected by the different pretreatments. These adrenaline-induced hemodynamic, electrocardiographic, and metabolic changes may predispose to arrhythmias and impair cardiac performance after a myocardial infarction. Nonselective beta blockers may be more effective in blocking the electrocardiographic and metabolic effects, but beta-1-selective beta blockers may have hemodynamic advantages.

Effects of prolonged adrenaline infusion and of mental stress on plasma minerals and parathyroid hormone

The role of the sympatho-adrenal system for the secretion of PTH in humans is not established. Previous studies on the effects of adrenaline on plasma mineral homeostasis have focused on injections or short-term infusions of adrenaline, and conflicting results concerning calcium and parathyroid hormone (PTH) responses have been reported. We therefore infused adrenaline or placebo continuously for 3 h to 10 healthy volunteers and studied several plasma minerals, as well as PTH levels. Venous plasma adrenaline concentrations increased to the upper physiological range (5 nmol l-1) during adrenaline infusion. Another nine volunteers were exposed for 25 min to mental stress (a colour word conflict test; CWT), which causes marked circulatory changes and raises plasma catecholamine concentrations. Plasma ionized and total calcium, and magnesium concentrations were slowly and gradually reduced during infusion of adrenaline, but there was only a small increase in PTH. Plasma potassium was decreased by adrenaline within 30 min and thereafter did not change further during infusion. There was a marked but transient increase in the plasma free fatty acids concentration, which were not related to the reduction of the calcium or magnesium levels. The adrenaline-induced decrements in calcium, magnesium and potassium, and increases in heart rates persisted 30 min after the infusion, despite a rapid decrease in plasma adrenaline concentrations within 5 min of termination of the infusion. Plasma phosphate concentrations were lowered during the first 90 min of adrenaline infusion, but after 3 h they had returned to baseline despite continued infusion. CWT induced small increments of the plasma ionized calcium and PTH concentrations. Plasma potassium levels were raised despite increases in plasma adrenaline at the beginning of the stress test, while phosphate values were reduced at the end of the test. Thus, long-lasting elevations of circulating adrenaline lower plasma ionized and total calcium, phosphate, magnesium and potassium, but the time courses for these changes differed markedly. Despite the reduction of plasma ionized calcium there was only little increase in PTH and thus no indication that sustained elevations of circulating adrenaline stimulates the secretion of PTH in vivo in humans. Responses to acute mental stress and adrenaline infusion differed qualitatively, indicating that adrenaline responses to stress are of minor importance in this respect.