Acquired Bartter-Like Syndrome Associated with Gentamicin Administration

Acquired Bartter-like syndrome associated with colistin use in an adult patient: a case report

Colistin is an effective antibiotic utilized for the treatment of Gram-negative bacterial infections with coverage against a broad spectrum of bacteria. Despite the broad antibacterial coverage, this antibiotic can have serious complications such as acute kidney injury. Colistin also can have a toxic effect on the loop of Henle, causing tubulopathy, electrolyte imbalances, and the occurrence of Bartter-like syndrome (BLS) which is characterized by magnesium and calcium disturbances, polyuria, and metabolic alkalosis. We here report a 32-year-old male with a history of multiple trauma due to an accident that received colistin therapy for Pseudomonas isolation from wound culture on the 5th day of hospitalization. Polyuria, hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalcemia were developed on the first week of colistin administration. The patient received colistin until the 21st day of hospitalization. Serum calcium and magnesium levels became normal 1 day after stopping colistin, while urine volume and metabolic alkalosis resolved 6 days after colistin discontinuing. Therefore, it is crucial to adjust the dose of colistin to minimize its toxicity.

Polymyxin B-induced Bartter syndrome

Bartter syndrome is a genetic disorder characterised by chloride-unresponsive metabolic alkalosis, hypokalaemia, hypomagnesaemia and hypercalciuria. While it commonly presents antenatally or in early infancy, sometimes, drugs can induce a state similar to Bartter syndrome in any age group, called acquired Bartter syndrome. Polymyxins and aminoglycosides are the most commonly implicated drugs. Polymyxin B and polymyxin E (popularly known as colistin) are the two chemically similar polymyxins that are commonly used clinically. While colistin is frequently associated with nephrotoxicity, polymyxin B is generally considered less nephrotoxic. This difference is due to the way these two drugs are handled by the kidneys. In this case report, we discuss a middle-aged male who developed Bartter syndrome due to polymyxin B, which resolved on discontinuation of the drug, and re-appeared after its re-introduction later. This case exemplifies the nephrotoxicity caused by polymyxin B and the need for vigilance when using this drug.

Gentamicin Inhibits Ca2+ Channel TRPV5 and Induces Calciuresis Independent of the Calcium-Sensing Receptor-Claudin-14 Pathway

BACKGROUND

Treatment with the aminoglycoside antibiotic gentamicin can be associated with severe adverse effects, including renal Ca²⁺ wasting. The underlying mechanism is unknown but it has been proposed to involve activation of the Ca²⁺-sensing receptor (CaSR) in the thick ascending limb, which would increase expression of claudin-14 (CLDN14) and limit Ca²⁺ reabsorption. However, no direct evidence for this hypothesis has been presented.

METHODS

We studied the effect of gentamicin in vivo using mouse models with impaired Ca²⁺ reabsorption in the proximal tubule and the thick ascending limb. We used a Cldn14 promoter luciferase reporter assay to study CaSR activation and investigated the effect of gentamicin on activity of the distal nephron Ca²⁺ channel transient receptor potential vanilloid 5 (TRPV5), as determined by patch clamp in HEK293 cells.

RESULTS

Gentamicin increased urinary Ca²⁺ excretion in wild-type mice after acute and chronic administration. This calciuretic effect was unaltered in mice with genetic CaSR overactivation and was present in furosemide-treated animals, whereas the calciuretic effect in Cldn14^-/- mice and mice with impaired proximal tubular Ca²⁺ reabsorption (claudin-2 [CLDN2]-deficient Cldn2^-/- mice) was equivalent to that of wild-type mice. In vitro, gentamicin failed to activate the CaSR. In contrast, patch clamp analysis revealed that gentamicin strongly inhibited rabbit and human TRPV5 activity and chronic gentamicin administration downregulated distal nephron Ca²⁺ transporters.

CONCLUSIONS

Gentamicin does not cause hypercalciuria via activation of the CaSR-CLDN14 pathway or by interfering with proximal tubular CLDN2-dependent Ca²⁺ reabsorption. Instead, gentamicin blocks distal Ca²⁺ reabsorption by direct inhibition of the Ca²⁺ channel TRPV5. These findings offer new insights into Ca²⁺ wasting in patients treated with gentamicin.

Pathophysiology of Drug-Induced Hypomagnesaemia

Magnesium (Mg²⁺) is the second most abundant intracellular and fourth extracellular cation found in the body and is involved in a wide range of functions in the human cell and human physiology. Its role in most of the enzyme processes (ATP-ases)-stabilisation of nucleic acids (DNA, RNA), regulation of calcium and potassium ion channels, proliferation, glucose metabolism and apoptosis-make it one of the most important cations in the cell. Three pathogenetic mechanisms are mainly implicated in the development of hypomagnesaemia: reduced food intake, decreased intestinal absorption and increased renal excretion of Mg²⁺. This review presents the function of Mg²⁺, how it is handled in the kidney and the drugs that cause hypomagnesaemia. The frequency and the number of drugs like diuretics and proton-pump inhibitors (PPIs) that are used daily in medical practice are discussed in order to prevent and treat adverse effects by providing an insight into Mg²⁺ homeostasis.

Type-5 Bartter syndrome presenting with metabolic seizure in adulthood

Bartter syndrome is a very rare and heterogeneous disease with variable age of onset and symptom severity. Genotypically they have inherited disorders of the thick ascending limb in the renal tubular system, which manifest phenotypically as electrolyte imbalance due to loss of sodium, chloride and potassium. Gain of function mutations in the calcium-sensing receptor has been described in some patients with Bartter's syndrome (type-5 Bartter syndrome or autosomal dominant hypocalcaemia with Bartter syndrome) associated with hypocalcaemia and hypercalciuria differentiating it from Gitelman syndrome. This phenotype has been reported to present in adulthood with metabolic abnormalities. We present a case of a middle-aged woman who presented with metabolic seizures and on evaluation was found to have profound electrolyte abnormalities which were corrected with supplements and led to the resolution of symptoms.

Electrolyte and Acid-Base Disorders Triggered by Aminoglycoside or Colistin Therapy: A Systematic Review

Aminoglycoside or colistin therapy may alter the renal tubular function without decreasing the glomerular filtration rate. This association has never been extensively investigated. We conducted a systematic review of the literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Databases searched included United States National Library of Medicine, Excerpta Medica, and Web of Science. For the final analysis, we evaluated 46 reports, published after 1960, describing 82 cases. A total of 286 electrolyte and acid-base disorders were reported. Hypomagnesemia, hypokalemia, and hypocalcemia were reported in more than three quarter of cases. Further disorders were, in decreasing order of frequency, metabolic alkalosis, hyponatremia, hypophosphatemia, hypouricemia, hypernatremia, and metabolic acidosis. Six electrolyte and acid-base disorders were reported in seven cases, five in 12 cases, four in 16 cases, three in 31 cases, two in 11 cases, and one in five cases. Laboratory features consistent with a loop of Henle/distal tubular dysfunction were noted in 56 (68%), with a proximal tubular dysfunction in three (3.7%), and with a mixed dysfunction in five (6.1%) cases. The laboratory abnormality was unclassified in the remaining 18 (22%) cases. Treatment with aminoglycosides or colistin may trigger a proximal tubular or, more frequently, a loop of Henle/distal tubular dysfunction.

Pathophysiology, Evaluation, and Management of Metabolic Alkalosis

Metabolic alkalosis is an increase in blood pH to >7.45 due to a primary increase in serum bicarbonate (HCO3 -). Metabolic alkalosis results from alkali accumulation or acid loss, and it is associated with a secondary increase in carbon dioxide arterial pressure (PaCO2). Metabolic alkalosis is a common acid-base disorder, especially in critically ill patients. The pathogenesis of chronic metabolic alkalosis includes two derangements, generation of metabolic alkalosis via gain of alkali or loss of acid and maintenance of metabolic alkalosis by increased tubular HCO3 - reabsorption (failure of the kidneys to excrete excess alkali). Metabolic alkalosis is the most common acid-base disorder in hospitalized patients, particularly in the surgical critical care unit. Mortality increases as pH increases.

Differential diagnosis of perinatal Bartter, Bartter and Gitelman syndromes

The common finding of hypokalemic alkalosis in several unrelated disorders may confound the early diagnosis of salt-losing tubulopathy (SLT). Antenatal Bartter syndrome (BS) must be considered in idiopathic early-onset polyhydramnios. Fetal megabladder in BS may allow its distinction from third-trimester polyhydramnios that occurs in congenital chloride diarrhea (CCD). Fetal megacolon occurs in CCD while fecal chloride >90 mEq/L in infants is diagnostic. Failure-to-thrive, polydipsia and polyuria in early childhood are the hallmarks of classic BS. Unlike BS, there is low urinary chloride in hypokalemic alkalosis of intractable emesis and cystic fibrosis. Rarely, renal salt wasting may result from cystinosis, Dent disease, disorders of paracellular claudin-10b and Kir4.1 potassium-channel deficiency. Acquired BS may result from calcimimetic up-regulation of a calcium-sensing receptor or autoantibody inactivation of sodium chloride co-transporters in Sjögren syndrome. A relatively common event of heterozygous gene mutations for Gitelman syndrome increases the likelihood of its random occurrence in certain diseases of adult onset. Finally, diuretic abuse is the most common differential diagnosis of SLT. Unlike the persistent elevation in BS, urinary chloride concentration losses waxes and wanes on day-to-day assessment in patients with diuretic misuse.

Colistin-induced acquired Bartter-like syndrome: an unusual cause of meltdown

Colistin-induced nephrotoxicity is commonly associated with elevation of serum creatinine level or a reduction of urine output. Uncommonly, tubulopathy associated with colistin has been reported. Here we present a unique case of a 46-year-old man who developed polyuria, hypokalaemia, hypocalcaemia, hypomagnesemia and metabolic alkalosis after 3 days of therapy with intravenous colistimethate sodium. After ruling out other causes, a diagnosis of colistin-induced acquired Bartter syndrome was made. The patient required daily aggressive intravenous repletion of fluids and electrolytes. However, polyuria and metabolic abnormalities abated only after drug discontinuation.

The challenges of diagnosis and management of Gitelman syndrome

Gitelman syndrome is an inherited tubulopathy characterized by renal salt wasting from the distal convoluted tubule. Defects in the sodium chloride cotransporter (encoded by SLC12A3) underlie this autosomal recessive condition. This article focuses on the specific challenges of diagnosing and treating Gitelman syndrome, with use of an illustrative case report. Symptoms relate to decreased serum potassium and magnesium levels, which include muscle weakness, tetany, fatigue and palpitations. Sudden cardiac deaths have been reported. Making a diagnosis may be difficult given its rarity but is important. A knowledge of the serum and urine biochemical picture is vital to distinguish it from a broad differential diagnosis, and application of genetic testing can resolve difficult cases. There is a group of Gitelman syndrome heterozygous carriers that experience symptoms and electrolyte disturbance and these patients should be managed in a similar way, though here genetic investigations become key in securing a difficult diagnosis. Potassium and magnesium replacement is the cornerstone of treatment, though practically this can be hard for patients to manage and often does not fully relieve symptoms even when serum levels are normalized. Challenges arise due to the lack of randomized controlled trials focussing on treatment of this rare disease; hence, clinicians endorse strategies in line with correction of the underlying pathophysiology such as sodium loading or pharmacological treatments, which seem to help some patients. Focussed dietary advice and knowing the best tolerated preparations of potassium and magnesium medications are useful tools for the physician, as well as an awareness of the specific burdens that this patient group face in order to signpost appropriate support.

Effect of fatty acids from ethanol extract of Moringa oleifera seeds on kidney function impairment and oxidative stress induced by gentamicin in rats

Gentamicin, an aminoglycoside drug, used for the treatment of Gram-negative bacterial infections. Despite its potency against bacterial infections, its clinical use is limited owing to nephrotoxicity effect. However, the study investigated the nephroprotective effect of fatty acids from ethanolic extract of Moringa oleifera seeds (EEMOS) against gentamicin-induced kidney injury in rats. Forty-five male Wistar rats, 100-160 g, were divided into 5 groups as follows: Group 1 (control), 5 rats, received 0.2 ml/100 g/day of propylene glycol orally for 28 days. Group 2, 10 rats, received 100 mg/kg/day (i.p) of gentamicin (GENT) for 8 days. Group 3-5, 10 rats each, treated with EEMOS orally for 28 days at graded doses of 100, 200 and 400 mg/kg respectively after GENT treatment. Twenty four after treatment, five rats from each group were sacrificed. The remaining 5 rats were sacrificed after 2 weeks recovery period from the drugs. The result showed that GENT elicited polyuria, elevated plasma creatinine, urea, and lower plasma electrolytes and creatinine clearance levels. Measurements of 24 h urinary output demonstrated marked decrease in creatinine and potassium levels in the GENT-treated group, whereas sodium level remain unchanged. Also, GENT caused significant decrease in superoxide dismutase and an increase in malondialdehyde levels in the kidney of the rats. Histopathological examination revealed evidence of necrosis of the kidney. Treatment with EEMOS significantly ameliorated the alterations caused by GENT in the plasma, urine and kidney homogenate of the rats. Hence, the mono- and poly-unsaturated fatty acids present in EEMOS were responsible for its renoprotective ability.

Loss of Cystic Fibrosis Transmembrane Regulator Impairs Intestinal Oxalate Secretion

Patients with cystic fibrosis have an increased incidence of hyperoxaluria and calcium oxalate nephrolithiasis. Net intestinal absorption of dietary oxalate results from passive paracellular oxalate absorption as modified by oxalate back secretion mediated by the SLC26A6 oxalate transporter. We used mice deficient in the cystic fibrosis transmembrane conductance regulator gene (Cftr) to test the hypothesis that SLC26A6-mediated oxalate secretion is defective in cystic fibrosis. We mounted isolated intestinal tissue from C57BL/6 (wild-type) and Cftr^-/- mice in Ussing chambers and measured transcellular secretion of [¹⁴C]oxalate. Intestinal tissue isolated from Cftr^-/- mice exhibited significantly less transcellular oxalate secretion than intestinal tissue of wild-type mice. However, glucose absorption, another representative intestinal transport process, did not differ in Cftr^-/- tissue. Compared with wild-type mice, Cftr^-/- mice showed reduced expression of SLC26A6 in duodenum by immunofluorescence and Western blot analysis. Furthermore, coexpression of CFTR stimulated SLC26A6-mediated Cl^--oxalate exchange in Xenopus oocytes. In association with the profound defect in intestinal oxalate secretion, Cftr^-/- mice had serum and urine oxalate levels 2.5-fold greater than those of wild-type mice. We conclude that defective intestinal oxalate secretion mediated by SLC26A6 may contribute to the hyperoxaluria observed in this mouse model of cystic fibrosis. Future studies are needed to address whether similar mechanisms contribute to the increased risk for calcium oxalate stone formation observed in patients with cystic fibrosis.

Acquired Bartter syndrome following gentamicin therapy

Aminoglycoside nephrotoxicity may manifest as nonoliguric renal failure or tubular dysfunction, such as Fanconi-like syndrome, Bartter-like syndrome (BS), or distal renal tubular acidosis. We report a case who developed severe renal tubular dysfunction on the the 7^th day of gentamicin therapy, resulting in metabolic alkalosis, refractory hypokalemia, hypocalcemia, hypomagnesemia, and polyuria. The patient was diagnosed as a case of transient BS associated with gentamicin exposure. The patient recovered with conservative management.

Hypercalcemia-Induced Hypokalemic Metabolic Alkalosis in a Multiple Myeloma Patient: The Risk of Furosemide Use

Hypercalcemia is often seen in patients with malignancies, and in the past treatment for this has traditionally included loop diuretics. Clinically, patients with hypercalcemia frequently present with polyuria and volume contraction which may be further exacerbated by diuretic therapy. In the lab, hypercalcemia has been shown to activate the calcium-sensing receptor in the thick ascending limb of Henle and inactivate the 2 chloride sodium potassium co-transporter and induce a hypokalemic metabolic alkalosis, an effect similar to that of the loop diuretic furosemide. We now report what may well be the first clinical correlate of this laboratory finding in a patient who developed a hypokalemic metabolic alkalosis as a consequence of severe hypercalcemia due to multiple myeloma and whose metabolic derangement was corrected without the use of a loop diuretic which may have exacerbated the electrolyte abnormalities.

Hypomagnesemia: a clinical perspective

Although magnesium is involved in a wide spectrum of vital functions in normal human physiology, the significance of hypomagnesemia and necessity for its treatment are under-recognized and underappreciated in clinical practice. In the current review, we first present an overview of the clinical significance of hypomagnesemia and normal magnesium metabolism, with a focus on renal magnesium handling. Subsequently, we review the literature for both congenital and acquired hypomagnesemic conditions that affect the various steps in normal magnesium metabolism. Finally, we present an approach to the routine evaluation and suggested management of hypomagnesemia.

Acquired Bartter-like syndrome association with netilmicin therapy in an extremely low birth weight infant

Aminoglycosides are commonly used antibiotics with excellent renal parenchymal penetration. Their clinical effectiveness is counter balanced with the risk of renal toxicity, which develops in a dose-dependent fashion. Aminoglycoside-induced renal tubular dysfunction could result in diffuse damage or manifest as a Fanconi-like syndrome, Bartter-like syndrome (BLS), or distal renal tubular acidosis.(1-4) Although tubulopathy associated with amikacin and gentamicin was reported in adults and rarely children, to the best of our knowledge, netilmicin-associated BLS neither in adults nor in children has been reported in the literature. We here report a 30-week, 770 g male preterm infant who developed BLS just after netilmicin treatment for neonatal sepsis and recovered 6 weeks after the drug cessation.

Acquired bartter-like syndrome associated with colistin use in a preterm infant

Acquired Bartter-like syndrome (BLS), characterized by hypokalemic metabolic alkalosis, hypomagnesemia, hypocalcemia, and normal kidney function, can be induced by diuretics or antibiotics. It is a very rare condition and only anecdotal cases mostly in adults were reported. Although tubulopathy associated with colistin was reported in adults, to the best of our knowledge, colistin-associated BLS neither in adults nor in children has been reported in the literature. We here report a-28-week, 740 g female preterm infant who developed BLS just after colistin treatment for Acinetobacter baumannii infection and recovered few days after the drug cessation, and discuss the possible association of colistin and tubulopathy. More research on colistin pharmacokinetics and pharmacodynamics in critically ill patients and preterm infants is needed to guide adequate colistin dosing at the least toxicity.

Systematic review: hypomagnesaemia induced by proton pump inhibition

BACKGROUND

Proton pump inhibitors (PPIs) are a mainstay therapy for all gastric acid-related diseases. Clinical concerns arise from a small but growing number of case reports presenting PPI-induced hypomagnesaemia (PPIH) as a consequence of long-term PPI use. Current opinion is that reduced intestinal magnesium absorption might be involved, but nothing is known on the molecular mechanism underlying PPIH.

AIM

To investigate whether or not PPIH is a true, long-term drug-class effect of all PPIs and to scrutinise a possible role of comorbidity in its aetiology. Therefore, the primary objective in particular was to investigate serum magnesium dynamics in trials drug withdrawal and re-challenge. The secondary objective was to profile the 'patient at risk'.

METHODS

We reviewed systematically all currently available case reports on the subject and performed a statistical analysis on extracted data.

RESULTS

Proton pump inhibitor-induced hypomagnesaemia PPIH is a drug-class effect and occurred after 5.5 years (median) of PPI use, onset was broad and ranged from 14 days to 13 years. Discontinuation of PPIs resulted in fast recovery from PPIH in 4 days and re-challenge led to reoccurrence within 4 days. Histamine-2-receptor antagonists were the preferable replacement therapy in PPIH and prevented reoccurrence of hypomagnesaemia. In PPIH no specific risk profile was identified that was linked to the hypomagnesaemia.

CONCLUSIONS

The cases of PPIH show severe symptoms of magnesium depletion and identification of its causation was only possible through withdrawal of the PPI. Clinical awareness of PPIH is key to avoid putting patients at risk.

The influence of extracellular and intracellular calcium on the secretion of renin

Changes in plasma, extracellular, and intracellular calcium can affect renin secretion from the renal juxtaglomerular (JG) cells. Elevated intracellular calcium directly inhibits renin release from JG cells by decreasing the dominant second messenger intracellular cyclic adenosine monophosphate (cAMP) via actions on calcium-inhibitable adenylyl cyclases and calcium-activated phosphodiesterases. Increased extracellular calcium also directly inhibits renin release by stimulating the calcium-sensing receptor (CaSR) on JG cells, resulting in parallel changes in the intracellular environment and decreasing intracellular cAMP. In vivo, acutely elevated plasma calcium inhibits plasma renin activity (PRA) via parathyroid hormone-mediated elevations in renal cortical interstitial calcium that stimulate the JG cell CaSR. However, chronically elevated plasma calcium or CaSR activation may actually stimulate PRA. This elevation in PRA may be a compensatory mechanism resulting from calcium-mediated polyuria. Thus, changing the extracellular calcium in vitro or in vivo results in inversely related acute changes in cAMP, and therefore renin release, but chronic changes in calcium may result in more complex interactions dependent upon the duration of changes and the integration of the body's response to these changes.

Renal adaptation to gentamicin-induced mineral loss

BACKGROUND

Gentamicin, a well-known nephrotoxic drug, affects calcium and magnesium homeostasis. Although gentamicin induces urinary calcium and magnesium wasting immediately, it rarely causes significant hypocalcemia or hypomagnesemia clinically.

METHODS

We conducted an animal study to investigate the renal adaptation in calcium and magnesium handling after gentamicin treatment and effects on the expression of calcium and magnesium transport molecules in distal tubule. Gentamicin (40 mg/kg) was injected daily in male Sprague-Dawley rats (220-250 g) for up to 7 days.

RESULTS

This treatment did not affect serum creatinine, calcium, or magnesium levels. Gentamicin induced significant hypercalciuria (14-fold) and hypermagnesiuria (10-fold) in 6 h, which was associated with upregulation of TRPV5 (175 ± 3%), TRPV6 (170 ± 4%), TRPM6 (156 ± 4%) and calbindin-D28k (174 ± 3%; all p < 0.05 vs. control). This gene upregulation was maintained with daily injection of gentamicin for 7 days. The gentamicin-induced urinary calcium loss was reduced by 80% at days 3 and 7, while magnesium loss was reduced by 52 and 57% at days 3 and 7, respectively. On the other hand, urinary loss of potassium became worse on day 7 (2-fold), and phosphorus loss worse from day 3 to day 7 (3-fold).

CONCLUSION

There is a rapid adaptation to gentamicin-induced hypercalciuria and hypermagnesiuria. The upregulation of distal tubule transport molecules, TRPV5, TRPV6, TRPM6 and calbindin-D28k occurs within 6 h of gentamicin treatment. This renal adaptation prevents further mineral loss due to gentamicin treatment.

[Pharmacologically-induced neurocatastrophes]

Drug-induced adverse reactions represent a significant health problem in developed countries. These events cause 5% of hospital admissions and are one of the main causes of mortality. Neurological manifestations are among the most frequent. This article reviews catastrophic cerebrovascular situations and confusional syndromes, as well as epilepsy, structural encephalopathy, neuromuscular disorders, catastrophic movement disorders and infections, all of which can be drug-induced.

A practical approach to genetic hypokalemia

Mutations in genes encoding ion channels, transporters, exchangers, and pumps in human tissues have been increasingly reported to cause hypokalemia. Assessment of history and blood pressure as well as the K⁺ excretion rate and blood acid-base status can help differentiate between acquired and inherited causes of hypokalemia. Familial periodic paralysis, Andersen's syndrome, congenital chloride-losing diarrhea, and cystic fibrosis are genetic causes of hypokalemia with low urine K⁺ excretion. With respect to a high rate of K⁺ excretion associated with faster Na⁺ disorders (mineralocorticoid excess states), glucoricoid-remediable aldosteronism and congenital adrenal hyperplasia due to either 11β-hydroxylase and 17α-hydroxylase deficiencies in the adrenal gland, and Liddle's syndrome and apparent mineralocorticoid excess in the kidney form the genetic causes. Among slow Cl^- disorders (normal blood pressure, low extracellular fluid volume), Bartter's and Gitelman's syndrome are most common with hypochloremic metabolic alkalosis. Renal tubular acidosis caused by mutations in the basolateral Na⁺/HCO₃^- cotransporter (NBC1) in the proximal tubules, apical H⁺-ATPase pump, and basolateral Cl^-/HCO₃^- exchanger (anion exchanger 1, AE1) in the distal tubules and carbonic anhydroase II in both are genetic causes with hyperchloremic metabolic acidosis. Further work on genetic causes of hypokalemia will not only provide a much better understanding of the underlying mechanisms, but also set the stage for development of novel therapies in the future.

Cystic fibrosis, aminoglycoside treatment and acute renal failure: the not so gentle micin

Aminoglycosides have a wide spectrum of gram-negative anti-bacterial activities and are available at low cost, which makes them commonly used drugs, especially for patients with cystic fibrosis (CF), who often suffer from chronic lung infections from Pseudomonas aeruginosa. Unfortunately, this treatment seems to have resulted in an increased incidence of acute renal failure (ARF) in patients with CF. A recent case-control study investigated risk factors for ARF in CF patients and suggested intravenous use of gentamicin as the prime culprit. Moreover, in most cases, at least one other risk factor, such as CF-related diabetes, pre-existing renal failure, dehydration or concurrent use of other nephrotoxic drugs, was present. We comment on the renal handling of aminoglycosides and the possible mechanisms of toxicity, as well as strategies for risk minimisation.

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.

Drug-induced hypomagnesaemia : scope and management

Nearly 50 medications have been implicated as inducing hypomagnesaemia, sometimes based on insufficient data regarding clinical significance and frequency of occurrence. In fact, clinical effects attributed to hypomagnaesemia have been reported in only 17 of these drugs. A considerable amount of literature relating to individual drugs has been published, yet a comprehensive overview of this issue is not available and the hypomagnesaemic effect of a drug could be either overemphasised or under-rated. In addition, there are neither guidelines regarding treatment, prevention and monitoring of drug-induced hypomagnesaemia nor agreement as to what serum level of magnesium may actually be defined as 'hypomagnesaemia'. By compiling data from published papers, electronic databases, textbooks and product information leaflets, we attempted to assess the clinical significance of hypomagnesaemia induced by each drug. A practical approach for managing drug-induced hypomagnesaemia, incorporating both published literature and personal experience of the physician, is proposed. When drugs classified as inducing 'significant' hypomagnesaemia (cisplatin, amphotericin B, ciclosporin) are administered, routine magnesium monitoring is warranted, preventive treatment should be considered and treatment of hypomagnesaemia should be initiated with or without overt clinical manifestations. In drugs belonging to the 'potentially significant' category, among which are amikacin, gentamicin, laxatives, pentamidine, tobramycin, tacrolimus and carboplatin, magnesium monitoring is justified when either of the following occurs: clinical manifestations are apparent; persistent hypokalaemia, hypocalcaemia or alkalosis are present; other precipitating factors for hypomagnesaemia coexist; or treatment is with more than one potentially hypomagnesaemic drug. No preventive treatment is required and treatment should be initiated only if hypomagnesaemia is accompanied by symptoms or clinically significant relevant laboratory findings. In those drugs whose hypomagnesaemic effect is labelled as 'questionable', including furosemide and hydrochlorothiazide, routine monitoring and treatment are not required.