Plasma Electrolyte Concentrations Research Articles

Plasma Electrolytes Response in Mud Catfish, Clarias gariepinus (Burchell 1822) exposed to Different Regimes of Salinity and pH

Introduction: Aquatic organisms, especially fish, are highly sensitive to environmental changes that can profoundly affect their physiological processes essential for survival. Physico-chemical factors such as salinity and pH exert significant influences on osmoregulation and ion balance, which are critical for maintaining cellular homeostasis in fish. Aims: This study aims to explore how varying levels of salinity and pH affect plasma electrolyte concentrations in Clarias gariepinus, focusing on potassium (K+), sodium (Na+), chloride (Cl−), and bicarbonate (HCO3−) ions. The objective is to understand the physiological responses of C. gariepinus to these environmental factors and their potential as biomarkers for assessing aquatic ecosystem health. Materials and Methods: Juvenile C. gariepinus was exposed to different salinity levels (4 ‰, 6 ‰, 8 ‰) and pH levels (4, 6, 8) over 21 days. Plasma electrolyte concentrations were measured using an SFRI ISE 6000 Electrolyte Analyser. Statistical analysis included ANOVA and DMRT to identify significant differences (p < 0.05) among experimental groups. Results: The study found significant variations in K+, Cl−, Na+, and HCO3- concentrations in C. gariepinus across different salinity and pH conditions. K+ levels decreased with increasing salinity, indicating stress-induced responses, while pH variations had less pronounced effects on K+ regulation. Cl− concentrations increased with higher salinity levels, suggesting adaptive osmoregulatory strategies. Na+ levels showed significant fluctuations across salinity and pH conditions, whereas HCO3− levels responded uniquely to changes in these parameters, demonstrating adaptive mechanisms in acid-base balance. Conclusion: This research underscores the adaptive responses of C. gariepinus to fluctuations in salinity and pH, highlighting their ability to maintain plasma electrolyte balance under varying environmental conditions. These findings contribute to understanding the ecophysiological adaptations of C. gariepinus and suggest the potential utility of plasma electrolytes as biomarkers for assessing the health of aquatic ecosystems.

Biochemical test as an efficient system to improve safety in parenteral nutrition for premature infants

ObjectiveThe biochemical test validation process of parenteral nutrition bags is described to verify the correct composition of critical compounds before its administration, as well as its impact on safety after two years since its implantation in a population of premature infants. MethodFor the validation of the technique, 35 samples of parenteral nutrition without lipids were processed by the emergency laboratory, following the routine procedures used to measure the concentrations of glucose and electrolytes in plasma and urine. To analyze its impact on safety, pre-implantation and post-implantation risk analysis was carried out using failure mode, effects and criticality analysis (FMECA). Likewise, all out-of-range results and their potential repercussions on patient safety were evaluated. ResultsRegression analysis showed no systematic measurement error for glucose, calcium and potassium; however, there is a constant systematic error for sodium and magnesium, thus both were discarded for routine analysis. Failure mode, effects and criticality analysis results showed a decrease in the risk of the process of 11% for the biochemical test. We tested 1,734 parenteral nutritions from 218 premature neonates; 58 (3.3%) results were out of the acceptance range, and 7 were considered to be potentially dangerous compounding errors. ConclusionsThe biochemical test of glucose and electrolytes is an efficient and reproducible method that prevents possible compounding errors from reaching the patient.

Beneficial Effects of Hibiscus sabdariffa in Diabetic Wistar Rats

Hibiscus sabdariffa is a yearly shrub that is widely grown in some Asian and African countries including Nigeria where it is commonly prepared as a hot or cold beverage and also used as medicine. It is applied in folklore remedies in the treatment of some ailments. This study was aimed at investigating the effects of the aqueous calyx extract of Hibiscus sabdariffa on some biochemical parameters of diabetic male Wistar rats. The rats were divided into four (4) groups of five (5) rats each. Group one (1) which served as non diabetic (negative) control received distilled water only. Group 2 served as diabetic control and received distilled water after alloxan-induced diabetes. Group three (3) and group four (4) were diabetic rats that received 250mg/kg bw and 500mg/kg bw of the aqueous calyx extract of Hibiscus sabdariffa respectively, for a period of four (4) weeks. The Statistical Program for Social Sciences (SPSS version 21.0) was used for the analysis. Differences between group means was tested using analysis of variance (ANOVA) and compared using the post hoc test. P<0.05 was considered statistically significant. The results obtained showed that the higher dose of the extract caused a significant decrease in blood glucose level in 4 weeks of the study. The changes observed in the plasma concentrations of electrolytes indicated that the extract significantly improved diabetes induced decrease in Cl- level while changes in Na+, K+ and HCO3- were not statistically significant. It also significantly improved lipid profile and reduced oxidative stress in diabetic male Wistar rats. This study revealed that, the calyx extract of Hibiscus sabdariffa demonstrated anti-hyperglycemic effects in diabetic Wistar rats.

Individualising / personalizing hemodialysate composition

The effectiveness of the haemodialysis (HD) treatment directly affects the survival and quality of life of dialysis patients. In this regard, the composition of the dialysate, including the quality of the water, is very important. Normalizing the plasma electrolyte and mineral concentrations before to dialysis while reducing significant changes in the patient's intradialytic plasma concentrations is one of HD's main goals. For the purpose of avoiding intra- and interdialytic hypotension as well as pulmonary edoema, adequate sodium (Na) and water elimination is essential. The cardiovascular system and the bones may be protected by having the right amounts of calcium (Ca) and magnesium (Mg) in the dialysate. This will help to avoid extraskeletal calcifications, severe secondary hyperparathyroidism, and adynamic bone disease. A steady pH in body fluids is required for proper protein and membrane function as well as bone protection, and this is achieved by maintaining an adequate bicarbonate concentration [HCO3]. A sufficient dialysate glucose concentration prevents life-threatening hypoglycemia and severe hyperglycemia, which can cause serious cardiovascular problems and exacerbate diabetic comorbidities.

The in-vivo diuretic activity of methanolic extract of Quercus leucotrichophora A. Camus seeds

IntroductionTraditional healers' assertions that Quercus leucotrichophora A. Camus is a plant that has been used in traditional medicine to treat various urinary and renal diseases, thus the present study aims to investigate the diuretic activity of the methanolic extract of seeds in rats. MethodsDried course powder was extracted with methanol using soxhlet extraction. Male Wistar rats were given a control (normal saline, 15 ml), a reference medication (furosemide, 13 mg/kg), and three separate doses (250 mg/kg, 375 mg/kg, and 500 mg/kg) of the extract orally. Urine volume, urinary electrolytes, urine pH, and conductivity were measured to establish the extract's diuretic activity. The urine outflow was tested at 6, 12, and 24 h, as well as electrolyte content, pH, and conductivity. Creatinine, urea, aldosterone, and electrolyte concentrations in plasma and urine samples were also determined. The index kidney function was determined by analyzing kidney homogenate. One-way ANOVA was used to evaluate the data. ResultsThe findings demonstrated that the extract increased diuresis in a dose-dependent manner, i.e., at 500 mg/kg, the extract exhibited significant diuretic effects (p < 0.001) as compared to the reference medicine, furosemide. The urinary excretion of Na+, K+, and Cl− was also significantly increased (p < 0.001) at all doses. The effectiveness of the extract as a diuretic was further established by biochemical analysis. These results confirm the historic usage of the herb as a diuretic and the importance of maintaining indigenous knowledge. ConclusionCollectively, the data provided here indicated that using a methanolic extract of Quercus leucotrichophora seeds to cause diuresis is a viable option.

Pharmacokinetic and pharmacodynamic properties of orally administered torasemide in healthy cats.

BackgroundIn people and dogs, torasemide has higher bioavailability, longer half‐life, and longer duration of action than equivalent doses of furosemide but data regarding pharmacological properties of torasemide in cats are limited.ObjectiveTo assess pharmacokinetic and pharmacodynamic parameters of torasemide in healthy cats, and to investigate the effects of a single administration of torasemide on indicators of diuresis, plasma creatinine concentration, blood pressure, electrolyte concentrations and markers of the renin‐angiotensin‐aldosterone system (RAAS).AnimalsSix clinically healthy adult European shorthair cats.MethodsRandomized 4‐period crossover design with 3 groups and 4 treatments. Pharmacokinetic parameters were obtained using a noncompartmental analysis, and the clinically effective dose was assessed using a Hill model.ResultsMean absolute bioavailability was estimated at 88.1%. Mean total body clearance was 3.64 mL/h/kg and mean terminal half‐life was 12.9 hours. Urine output significantly increased after torasemide administration (P < .001). The urine sodium : potassium ratio (uNa : uK) paralleled and was statistically correlated to urine output (P < .001). Administration of a single torasemide dose led to a significant dose‐dependent increase in urine aldosterone : creatinine ratio (uAldo : C; P < .001) and a transient decrease in plasma potassium concentration (P < .001) but did not affect blood pressure or plasma creatinine concentration.Conclusions and Clinical ImportanceA single torasemide dose leads to a significant increase in diuresis and renin‐angiotensin‐aldosterone system (RAAS) activation in healthy cats, with high absolute bioavailability, and without clinically relevant adverse effects. Pharmacokinetic parameters indicate that once daily dosing of 0.27 mg/kg may be appropriate in a clinical setting.

Higher Parenteral Electrolyte Intakes in Preterm Infants During First Week of Life: Effects on Electrolyte Imbalances.

Objectives:This study aimed to investigate the effects of a higher intake of electrolytes from parenteral nutrition (PN) on plasma electrolyte concentrations in very low birth weight (VLBW, <1500 g) infants.Methods:This was a single-center cohort study including all VLBW infants born before (n = 81) and after (n = 53) the implementation of a concentrated PN regimen. Daily nutritional intakes and plasma concentrations of sodium, chloride, potassium, phosphate, and calcium were collected from clinical charts.Results:During the first postnatal week, electrolyte intakes were higher in infants who received concentrated PN compared with infants who received original PN. Infants who received concentrated PN had a lower incidence of hypokalemia (<3.5 mmol/L; 30% vs 76%, P < 0.001) and severe hypophosphatemia (<1.0 mmol/L; 2.2% vs 17%, P = 0.02). While the relatively high prevalence of severe hypophosphatemia in infants who received original PN can be explained by a phosphorus intake below the recommendation, the potassium intake during the first 3 postnatal days (mean ± SD: 0.7 ± 0.2 mmol/kg/d) was within the recommendation. The prevalence of early hypernatremia was not affected by the different sodium intake in the 2 groups.Conclusions:In VLBW infants, a sodium-containing PN solution (about 2.7 mmol/100 mL) does not cause hypernatremia during the first days of life. Furthermore, providing at least 1 mmol potassium/kg/d during the first 3 postnatal days might be necessary to prevent early hypokalemia.

ANALYSIS OF CHANGES IN ELECTROLYTE PARAMETERS IN WOMEN DURING IN VITRO FERTILIZATION PROGRAM

Aim of the research. To determine the concentration of basic plasma electrolytes in women in in vitro fertilization program who received more individualized medication correction on the basis of determination the clinical and pathogenetic role of disorders of the neuroendocrine regulation of water-salt metabolism, as well as to study data of the modern methods of prevention and correction of electrolyte disorders.&#x0D; Research materials. 110 patients in vitro fertilization program were examined.&#x0D; Conclusions. Thus, when using standard protocols for ovulation stimulation in in vitro fertilization program patients are more prone to have potassium and sodium imbalance.&#x0D; Ovarian hyperstimulation syndrome was detected only in patients of the main group with the standard ovulation induction protocols. This syndrome was not observed in patients receiving the combination therapy.

Изменения концентрации электролитов плазмы крови в условиях магнезиальной терапии у пациентов в состоянии травматического шока на фоне политравмы

Актуальность. Сроки выведения пациентов с политравмой из состояния травматического шока оказывают серьезное влияние на количество осложнений, длительность пребывания пациентов в отделении интенсивной терапии и стоимость лечения. Ранее показано, что применение гипертонического раствора магния сульфата способствует ускорению стабилизации гемодинамики у пациентов с политравмой. Цель исследования: определение концентрации основных электролитов в плазме крови в процессе применения гипертонического раствора магния сульфата у пострадавших с политравмой, которые находились в состоянии гиповолемического шока. Материалы и методы. У 24 пациентов с политравмой, поступивших в клинику в состоянии гиповолемического травматического шока, в условиях операционной проводилась коррекция гемодинамики гипертоническим раствором магния сульфата в физиологическом растворе. 25% раствор магния сульфата вводился внутривенно из расчета 0,35 ± ± 0,05 мл/кг массы тела с целью создания осмотического градиента между внутрисосудистой и интерстициальной жидкостью, а также с целью блокирования поступления натрия и кальция во внутриклеточное пространство. В процессе применения указанной методики изучены изменения содержания электролитов в плазме крови. Определяли концентрацию магния, калия, кальция, натрия и хлоридов. Кровь для изучения содержания электролитов забирали на следующих этапах: 1) перед применением гипертонического раствора магния сульфата; 2) через 5–10 минут после полного окончания инфузии магния сульфата в физиологическом растворе; 3) через 25–35 минут после полного окончания инфузии магния сульфата в физиологическом растворе; 4) через 1 час после полного окончания инфузии магния сульфата в физиологическом растворе; 5) через 2 часа; 6) через 6 часов; 7) через 24 часа. Результаты. Исследование показало, что применение этой методики не было ассоциировано с опасным повышением концентрации магния в плазме крови до уровня 4,0 ммоль/л и более. А значит, не возникала опасность угнетения сердечной деятельности. Высокое содержание магния в плазме крови наблюдали на 2-м этапе исследования — через 5–10 минут после полного окончания инфузии 25% раствора магния сульфата в физиологическом растворе. В среднем концентрация магния составила 2,15 ± 0,17 ммоль/л. Такое повышение концентрации магния в плазме крови было закономерно ассоциированное с угнетением сухожильных рефлексов и функции внешнего дыхания. К концу исследования содержание магния в плазме крови постепенно нормализовалось и составило 0,98 ± 0,09 ммоль/л. Выводы. Быстрое введение в организм высокой дозы ионизированного магния и сульфата приводило по принципу Гэмбла к временному уменьшению концентрации в плазме крови других электролитов. На определенных этапах исследования выявлено достоверное уменьшение содержания в плазме крови калия, натрия, хлоридов. Меньше всего изменялось содержание в плазме крови кальция.

Hemodynamic, renal and hormonal effects of lung protective ventilation during robot-assisted radical prostatectomy, analysis of secondary outcomes from a randomized controlled trial

BackgroundLung protective ventilation with low tidal volume (TV) and increased positive end-expiratory pressure (PEEP) can have unfavorable effects on the cardiovascular system. We aimed to investigate whether lung protective ventilation has adverse impact on hemodynamic, renal and hormonal variables.MethodsIn this randomized, single-blinded, placebo-controlled study, 24 patients scheduled for robot-assisted radical prostatectomy were included. Patients were equally randomized to receive either ventilation with a TV of 6 ml/IBW and PEEP of 10 cm H2O (LTV-h.PEEP) or ventilation with a TV of 10 ml/IBW and PEEP of 4 cm H2O (HTV-l.PEEP). Before, during and after surgery, hemodynamic variables were measured, and blood and urine samples were collected. Blood samples were analyzed for plasma concentrations of electrolytes and vasoactive hormones. Urine samples were analyzed for excretions of electrolytes and markers of nephrotoxicity.ResultsComparable variables were found among the two groups, except for significantly higher postoperative levels of plasma brain natriuretic peptide (p = 0.033), albumin excretion (p = 0.012) and excretion of epithelial sodium channel (p = 0.045) in the LTV-h.PEEP ventilation group compared to the HTV-l.PEEP ventilation group. In the combined cohort, we found a significant decrease in creatinine clearance (112.0 [83.4;126.7] ml/min at baseline vs. 45.1 [25.4;84.3] ml/min during surgery) and a significant increase in plasma concentrations of renin, angiotensin II, and aldosterone.ConclusionLung protective ventilation was associated with minor adverse hemodynamic and renal effects postoperatively. All patients showed a substantial but transient reduction in renal function accompanied by activation of the renin-angiotensin-aldosterone system.Trial registrationClinicalTrials, NCT02551341. Registered 13 September 2015.

Risk factors for new-onset atrial fibrillation during critical illness: A Delphi study.

New-onset atrial fibrillation (NOAF) is common during critical illness and is associated with poor outcomes. Many risk factors for NOAF during critical illness have been identified, overlapping with risk factors for atrial fibrillation in patients in community settings. To develop interventions to prevent NOAF during critical illness, modifiable risk factors must be identified. These have not been studied in detail and it is not clear which variables warrant further study. We undertook an international three-round Delphi process using an expert panel to identify important predictors of NOAF risk during critical illness. Of 22 experts invited, 12 agreed to participate. Participants were located in Europe, North America and South America and shared 110 publications on the subject of atrial fibrillation. All 12 completed the three Delphi rounds. Potentially modifiable risk factors identified include 15 intervention-related variables. We present the results of the first Delphi process to identify important predictors of NOAF risk during critical illness. These results support further research into modifiable risk factors including optimal plasma electrolyte concentrations, rates of change of these electrolytes, fluid balance, choice of vasoactive medications and the use of preventative medications in high-risk patients. We also hope our findings will aid the development of predictive models for NOAF.

Early onset of depression and treatment outcome in patients with major depressive disorder

Major depressive disorder (MDD) is a highly heterogeneous disorder, which may partly explain why treatment outcome using antidepressants is unsatisfactory. We investigated the onset of depression as a possible clinical marker for therapy response prediction in the context of somatic biomarkers blood pressure and plasma electrolyte concentration. 889 MDD patients were divided into early (EO, n = 226), intermediate (IO, n = 493), and late onset (LO, n = 169) patients and were analyzed for differences in socio-demographic and clinical parameters, comorbidities and treatment outcome as well as systolic blood pressure and electrolytes. EO patients more often suffered from a recurrent depression, had more previous depressive episodes, a higher rate of comorbid axis I and II disorders, and more often reported of suicidality (p < 0.001) compared to IO and LO patients. Treatment outcome was not different from IO and LO patients, although LO patients responded faster. EO patients who showed an early non-improvement of depression after 2 weeks of therapy (<20% improvement) had a 4.3-fold higher likelihood to become non-remitter as compared to LO patients with an early improvement. EO patients had significantly lower systolic blood pressure than patients with IO or LO and electrolytes in EO patients were significantly correlated with depression severity. Our results confirm other studies showing an association of an early onset of depression with a slower treatment response. The worse treatment outcome in patients with an additional early non-improvement to antidepressant therapy opens perspectives to develop and test individualized treatment approaches for EO and LO patients in the future, which may be based on differences in autonomic regulation.

Preoperative risk factors including serum levels of potassium, sodium, and creatinine for early mortality after open abdominal surgery: a retrospective cohort study

BackgroundIn hospitalized patients, abnormal plasma electrolyte concentrations are frequent and have been linked to poor outcomes following acute surgery. The aim of this study was to assess whether preoperative plasma levels of potassium, sodium, and creatinine at the time of admission were associated with 30-day mortality in patients following open abdominal surgery.MethodsThis was a single-center register-based retrospective study. By means of electronic search in a maintained surgery database, all patients (n = 4177) aged ≥ 60 years old undergoing open surgery in our department from January 2000 to May 2013 were identified. Plasma was assessed within 30 days prior to surgery. The primary endpoint was 30-day postoperative mortality. The association between mortality and plasma levels of potassium, sodium, and creatinine were examined using Cox proportional hazard models.ResultsA total of 3690 patients were included in the study cohort. The rates of abnormal preoperative plasma levels were 36, 41, and 38% for potassium, sodium, and creatinine, respectively. The overall 30 day mortality was 20%. A predictive algorithm for 30 day mortality following abdominal surgery was constructed by means of logistic regression showing excellent distinction between patients with and without a fatal postoperative outcome.ConclusionApart from demographic factors (age, sex, and emergency surgery), preoperative imbalance in potassium, sodium and creatinine levels were significant independent predictors of early mortality following open abdominal surgery.

Electrolyte Concentrations and Liver Enzymes in Car Spray Painters Exposed to Car Spray Paints within Port Harcourt Metropolis, Rivers State, Nigeria

Aim: To determine the effect of car spray paint on electrolyte concentrations (sodium, potassium, bicarbonate and chloride), Anion gap, Total Protein, Albumin, liver enzymes (Alanine amino transferase and Aspartate amino transferase) of car spray painters.&#x0D; Place of Study: The study was conducted within Port Harcourt metropolis, Rivers State Nigeria.&#x0D; Methodology: Twenty (20) male car spray painters age range between 25 and 61 years with 7- 28 years work experience in car spray painting (test subjects) and twenty (20) apparently healthy male individuals aged between 25 and 61 years who work within an office setting far away from car spray painting garage (non-exposed individuals) were used as control for the study. Plasma electrolyte concentrations were estimated using Ion selective electrode method while Liver Enzymes Alanine amino transferase and Aspartate amino transferase were estimated using spectrophotometric method. Results obtained from the experiment were expressed as Mean ± Standard Deviation. P &lt; .05 were considered statistically significant.&#x0D; Results: Sodium, Potassium, Bicarbonate and Chloride concentrations in plasma of car spray painters when compared to non-car spray painters did not showed any significant difference (P&gt; .05). However, Anion gap was significantly increased (P&lt;.05) in plasma of car spray painters when compared to non-car spray painters. Alanine amino transferase activity were significantly higher in plasma of Car spray painters (P &lt; .05) when compared to non-car spray painters while Aspartate amino transferase activity, Total protein and Albumin concentrations remained relatively unchanged when compared between the studied groups. However, Aspartate amino transferase and Alanine amino transferase activities were affected by years of exposure to car paints.&#x0D; Conclusions: This study suggest that car spray paint affects Anion gap and Alanine amino transferase activity in car spray painters hence safety apparatus should be worn while working. However further test on other liver enzymes should be done to validate the effect of spray paint on the liver.

Intravascular albumin loss is strongly associated with plasma volume withdrawal in dialysis patients.

Low circulating albumin closely predicts mortality in end-stage renal disease (ESRD) patients. The cause(s) of hypoalbuminemia (hALB) in ESRD patients remains to be elucidated. The aim of the present study was to determine the role of plasma volume (PV) withdrawal in the reduction of total circulating albumin and essential blood solutes induced by hemodialysis (HD). PV determined with high-precision automated carbon monoxide-rebreathing, total circulating as well as concentration of plasma albumin and electrolytes were assessed prior to and after 4-hour HD in 10 ESRD patients. Baseline PV ranged from 3.5 to 6.2 l. After HD, PV was decreased by 689 ± 566 mL (-16%) (P = 0.004). Total circulating albumin was largely reduced after HD (170.8 ± 35.1 vs. 146.1 ± 48.9 g, P = 0.008), while albumin concentration was unaltered. According to a strong linear relationship (r = 0.91, P < 0.001), one-third of total circulating albumin is lost from the intravascular compartment for every liter of PV removed. Similar results were found regarding Na+ and Ca2+ electrolytes. Total circulating albumin, but not albumin concentration, is substantially reduced by HD in proportion to the amount of PV removed from the circulation. This study highlights the potential contributing role of PV withdrawal to hALB in ESRD patients.

Proof-of-concept study: Evaluation of plasma and urinary electrolytes as markers of response to L-asparaginase therapy in dogs with high-grade lymphoma.

Response to chemotherapy is one of the most important prognostic factors in dogs with lymphoma. The objective of this feasibility study was to evaluate if clinical responses to a specific cytotoxic agent (L-asparaginase) could be anticipated by measuring analyte concentrations in plasma and urine concentrations of lymphoma-bearing dogs. We hypothesized that potassium and phosphate concentrations in plasma and urine would be higher in dogs that completely responded to therapy. Plasma and urine samples of dogs with lymphoma were obtained before 12 and 24hours after intramuscular L-asparaginase injections. Peripheral lymph node volumes were evaluated according to the Veterinary Cooperative Oncology Group standardized criteria. Plasma and urine electrolyte, calcium, phosphate, creatinine, urea, total protein, and albumin concentrations were measured, and the fractional excretions of each electrolyte were calculated. Statistical analyses compared complete vs partial responders using a linear regression model. Contrast analyses were also performed to differentiate the mean of each group, with adjustments made with the Benjamini-Hochberg procedure. Fourteen dogs were included, eight with complete responses, and six with partial responses. Plasma phosphate concentrations were significantly higher at 12hours (P=.0003) and 24hours (P=.009) after complete responses to therapy. This study demonstrates the potential use of plasma and urine analyte monitoring after chemotherapy induction. Plasma phosphate measurements represent a potential indicator of early responses to L-asparaginase therapy. Larger population studies are warranted to confirm these preliminary results.

Niche partitioning between river shark species is driven by seasonal fluctuations in environmental salinity

Abstract Tropical rivers and estuaries are highly dynamic environments, where environmental conditions change dramatically over spatial and temporal scales. This creates both physiological and ecological challenges for euryhaline elasmobranchs, where fluctuations in salinity can impact not only osmoregulatory function but also the ability to find and acquire prey. We investigated how spatial and temporal variation in environmental salinity influences physiological homoeostasis, habitat utilization and migration timing in two euryhaline carcharhinid sharks within a tropical river in northern Australia. Neonate and juvenile bull sharks Carcharhinus leucas and speartooth sharks Glyphis glyphis were tracked over a 4‐year period using implanted acoustic tags and an array of hydrophone receivers. Tissue samples were also collected from captured sharks and analysed for interspecific differences in plasma osmolarity, urea and electrolyte (Na+ and K+) concentrations and the stable isotopes δ13C and δ15N. We discovered that immature C. leucas and G. glyphis segregate spatially along a salinity gradient between September and December, where the mean volume of intersection between species dropped as low as 0.01. While G. glyphis used higher salinity environments (mean salinity = 19.22) located between 30 and 70 km from the mouth of the estuary, C. leucas occupied freshwater reaches (mean salinity = 1.98) between 60 and 110 km upstream. Plasma osmolarities of both species were always hyperosmotic to the environment, with electrolyte concentrations maintained within a narrow range independent of environmental osmolarities. At the onset of the wet season, both C. leucas and G. glyphis undertook a coordinated downstream migration towards the lower estuary before returning upstream. Carcharhinus leucas blood tissues were more enriched in δ15N and δ13C than samples collected from similar size G. glyphis, suggesting that these species not only spatially segregate within low salinity habitats but also prey on different dietary resources. Furthermore, a loss of enriched isotopic values in fin tissue with increasing body length provides further support for marine use by adult sharks in conjunction with dependence on rivers as important nursery habitat. Our results illustrate the importance of long‐term integrative studies into resource competition and the significance of discrete brackish habitats for threatened euryhaline elasmobranchs. A free Plain Language Summary can be found within the Supporting Information of this article.

Pharmacokinetics of magnesium and its effects on clinical variables following experimentally induced hypermagnesemia.

The objectives of this study were to describe pharmacokinetic and pharmacodynamic changes as a result of a single intravenous administration of magnesium sulfate (MgSO4 ) to healthy horses. MgSO4 is a magnesium salt that has been used to calm horses in equestrian competition and is difficult to regulate because magnesium is an essential constituent of all mammals. Six healthy adult female horses were administered a single intravenous dose of MgSO4 at 60mg/kg of body weight over 5min. Blood, urine, and cerebrospinal fluid (CSF) samples were collected, and cardiovascular parameters were monitored and echocardiograms performed at predetermined times. Noncompartmental pharmacokinetic analysis was applied to plasma concentrations of ionized magnesium (Mg2+ ). Objective data were analyzed using the Wilcoxon rank-sum test with p<.05 used as a determination for significance. Plasma concentrations of Mg2+ increased nearly fivefold, ionized calcium (Ca2+ ) decreased by nearly 10%, and the Ca2+ to Mg2+ ratio declined more than 3.5-fold and remained different than baseline until 24hr (p<.05). Significant changes were seen with urinary fractional excretion of electrolytes, cardiovascular parameters, and echocardiographic measurements. No changes were detected in CSF electrolyte concentrations. The decrease in Ca2+ result of hypermagnesemia supports the interaction between these cations. Alterations detected in plasma electrolyte concentrations and urinary fractional excretion of electrolytes may serve as biomarkers for regulatory control for the nefarious administration of MgSO4 .

Reducing the risk of intradialytic hypotension by altering the composition of the dialysate.

Hypotension is the most common complication of outpatient hemodialysis sessions, with a reported prevalence of 4% to 31%, depending on which definition has been used and whether patients are symptomatic and nursing interventions were required. Dialysis centers which mix the dialysate in the dialysis machine have the opportunity to individualize the composition of the dialysate for patients. This permits a choice of dialysate sodium, potassium, calcium, magnesium, bicarbonate, acetate, and citrate concentrations and temperature. Studies have reported a higher intradialytic systolic blood pressure and fewer episodes of intradialytic hypotension when using a higher dialysate sodium, calcium, magnesium concentrations and lower temperature, but no clinical advantage for changing the potassium, bicarbonate, or citrate for acetate concentrations. The introduction of newer technology allowing real time measurements of plasma electrolyte concentrations will potentially allow changing the dialysate composition to reduce the risk of intradialytic hypotension without increasing the risk of positive electrolyte balances.

Isoflurane attenuates carbogen-induced blood-brain barrier disruption independent of body temperature in mice and rats.

Isoflurane protects the blood-brain barrier (BBB) against cerebral extravasation of Evans blue dye (EBD), a commonly used serum protein tracer, in animals subjected to BBB disruption. As such, it has been implicated as a therapeutic agent that can prevent brain edema and damage caused by a number of brain insults, including focal ischemia and subarachnoid hemorrhage. Recently, it has been shown that isoflurane inhibits the cerebral extravasation of EBD following ischemic stroke chiefly by inducing hypothermia, raising the intriguing possibility that isoflurane protected against other causes of BBB disruption also through hypothermia. To test this hypothesis, we subjected mice and rats to inhalation of 20-30% carbogen, an inducer of BBB disruption, in the presence or absence of isoflurane while measuring their rectal temperature. In mice, carbogen inhalation on its own decreased rectal temperature from 36.4 ± 0.4 to 26.2 ± 0.6°C over a period of 60 minutes, and under this condition, isoflurane had no additional effect on body temperature. Nevertheless, isoflurane protected against carbogen-induced cerebral extravasation of EBD. In addition, when the body temperature was maintained in the normothermic range using an automated heating pad, isoflurane remained protective against cerebral extravasation of EBD. In rats, isoflurane also protected against cerebral extravasation of EBD, while having no effect on plasma pH, electrolyte concentrations, or osmolarity. In conclusion, isoflurane protected against BBB disruption caused by carbogen inhalation in mice and rats, but unlike isoflurane-mediated protection against ischemic BBB disruption, the effect could not be explained by anesthesia-induced hypothermia.