Myoglobinuria

Methylglyoxal-induced modification of myoglobin: An insight into glycation mediated protein aggregation

Post-translational modification of proteins by Maillard reaction, known as glycation, is thought to be the root cause of different complications, particularly in diabetes mellitus and age-related disorders. Methylglyoxal (MG), a reactive α-oxoaldehyde, increases in diabetic condition and reacts with the proteins to form advanced glycation end products (AGEs) following a Maillard-like reaction. In a time-dependent reaction study of MG with the heme protein myoglobin (Mb), MG was found to induce significant structural alterations of the heme protein, such as heme loss, changes in tryptophan fluorescence, and decrease of α-helicity with increased β-sheet content. These changes were found to occur gradually with increasing period of incubation. Incubation of Mb with MG induced the formation of several AGE adducts, including, carboxyethyllysine at Lys-16, carboxymethyllysine at Lys-87, carboxyethyllysine or pyrraline-carboxymethyllysine at Lys-133, carboxyethyllysine at Lys-42 and hydroimidazolone or argpyrimidine at Arg-31 and Arg-139. MG induced amyloid-like aggregation of Mb was detected at a longer period of incubation. MG-derived AGEs, therefore, appear to have an important role as the precursors of protein aggregation, which, in turn, may be associated with pathophysiological complications.

Venlafaxine-Associated Rhabdomyolysis: A Literature Review

PURPOSE

This systematic review aimed to investigate the clinical manifestations and characteristics of venlafaxine-associated rhabdomyolysis.

METHODS

A systematic search was conducted in PubMed, Elsevier, Science Direct, Embase, Springer Link, Wiley Online Library, CNKI, and Wanfang databases from the date of database inception to January 2023. Previously reported cases of venlafaxine-associated rhabdomyolysis were identified, and relevant data from these cases were collected for descriptive statistical analysis. Cases that met the inclusion criteria were evaluated to determine the correlation between adverse reactions and venlafaxine.

RESULTS

A total of 12 patients with venlafaxine-associated rhabdomyolysis were included. None of these patients had a history of muscle pain or discomfort. Of the 12 patients, 5 patients received venlafaxine at doses of ≤225 mg/d, whereas the remaining 7 patients received doses exceeding 225 mg/d. The main clinical symptoms included myalgia, muscle weakness, and renal injury. All 12 patients discontinued venlafaxine and received symptomatic care.

CONCLUSIONS

Venlafaxine, used either as a monotherapy or in combination with other drugs, may be associated with rhabdomyolysis. Creatine kinase levels may normalize or significantly decrease after discontinuation of venlafaxine and symptomatic treatment.

Cefiderocol-associated brown chromaturia

Cefiderocol is a novel siderophore cephalosporin antibiotic. In the present case report, a woman in her 70s presented with a 1-week history of altered mental status and progressive purulent discharge from a non-healing diabetic foot ulcer on her right heel. MRI of the right foot revealed chronic osteomyelitis of the calcaneum. Surgical debridement was performed, and the tissue cultures grew extensively drug resistant (XDR) Pseudomonas aeruginosa, XDR Acinetobacter baumannii and Enterococcus faecalis The patient received ampicillin-sulbactam and cefiderocol. The antibiotic treatment course was complicated by brown urine discolouration. Investigations were unrevealing for haemoglobinuria, myoglobinuria and bilirubinuria. A side effect from cefiderocol was suspected and subsequently discontinued. Her urine colour returned to its normal colour within 3 days of discontinuation of cefiderocol.

NGS-Based Genetic Analysis in a Cohort of Italian Patients with Suspected Inherited Myopathies and/or HyperCKemia

Introduction/Aims HyperCKemia is considered a hallmark of neuromuscular diseases. It can be either isolated or associated with cramps, myalgia, weakness, myoglobinuria, or rhabdomyolysis, suggesting a metabolic myopathy. The aim of this work was to investigate possible genetic causes in order to help diagnose patients with recurrent hyperCKemia or clinical suspicion of inherited metabolic myopathy. Methods A cohort of 139 patients (90 adults and 49 children) was analyzed using a custom panel containing 54 genes associated with hyperCKemia. Results A definite genetic diagnosis was obtained in 15.1% of cases, while candidate variants or variants of uncertain significance were found in a further 39.5%. Similar percentages were obtained in patients with infantile or adult onset, with some different causative genes. RYR1 was the gene most frequently identified, either with single or compound heterozygous variants, while ETFDH variants were the most common cause for recessive cases. In one patient, mRNA analysis allowed identifying a large LPIN1 deletion missed by DNA sequencing, leading to a certain diagnosis. Conclusion These data confirm the high genetic heterogeneity of hyperCKemia and metabolic myopathies. The reduced diagnostic yield suggests the existence of additional genes associated with this condition but also allows speculation that a significant number of cases presenting with hyperCKemia or muscle symptoms are due to extrinsic, not genetic, factors.

Integration of transcriptomics and metabolomics reveals the molecular mechanisms underlying the effect of nafamostat mesylate on rhabdomyolysis-induced acute kidney injury

Objective: To investigate the role and mechanisms of action of nafamostat mesylate (NM) in rhabdomyolysis-induced acute kidney injury (RIAKI). Methods: RIAKI rats were assigned into control group (CN), RIAKI group (RM), and NM intervention group (NM). Inflammatory cytokines and proenkephalin a 119-159 (PENKID) were assessed. Cell apoptosis and glutathione peroxidase-4 (GPX4) were detected using TUNEL assay and immunohistochemical staining. Mitochondrial membrane potential (MMP) was detected by JC-1 dye. The expression of genes and metabolites after NM intervention was profiled using transcriptomic and metabolomic analysis. The differentially expressed genes (DEGs) were validated using qPCR. The KEGG and conjoint analysis of transcriptome and metabolome were used to analyze the enriched pathways and differential metabolites. The transcription factors were identified based on the animal TFDB 3.0 database. Results: Serum creatinine, blood urea nitrogen, and PENKID were remarkably higher in the RM group and lower in the NM group compared to the CN group. Pro-inflammatory cytokines increased in the RM group and notably decreased following NM treatment compared to the CN group. Tubular pathological damages were markedly attenuated and renal cell apoptosis was reduced significantly in the NM group compared to the RM group. The expression of GPX4 was lower in the RM group compared to the CN group, and it increased significantly after NM treatment. A total of 294 DEGs were identified in the RM group compared with the NM group, of which 192 signaling pathways were enriched, and glutathione metabolism, IL-17 signaling, and ferroptosis-related pathways were the top-ranking pathways. The transcriptional levels of Anpep, Gclc, Ggt1, Mgst2, Cxcl13, Rgn, and Akr1c1 were significantly different between the NM and RM group. Gclc was the key gene contributing to NM-mediated renal protection in RIAKI. Five hundred and five DEGs were annotated. Compared with the RM group, most of the upregulated DEGs in the NM group belonged to Glutathione metabolism, whereas most of the downregulated DEGs were related to the transcription factor Cytokine-cytokine receptor interaction. Conclusion: NM protects the kidneys against RIAKI, which is mainly associated with NM mediated regulation of glutathione metabolism, inflammatory response, ferroptosis-related pathways, and the related key DEGs. Targeting these DEGs might emerge as a potential molecular therapy for RIAKI.

Exertional hemolysis and hematuria in a Labrador Retriever dog

A 7-y-old male Labrador Retriever dog was presented because of acute onset of dark-colored urine after a hunting session the day prior. Moderate hemoglobinemia was observed, associated with transient hemoglobinuria and hematuria with no concurrent evidence of underlying urinary tract disease. The patient’s clinical signs resolved within 36 h post-exercise without specific treatment. The concurrent occurrence of exertional hemolysis and hematuria in a dog is uncommon; these conditions are commonly reported separately in human athletes.

Capacity of extracellular globins to reduce liver fibrosis via scavenging reactive oxygen species and promoting MMP-1 secretion

Background & aims

Hepatic stellate cells (HSCs) are the primary cell type in liver fibrosis, a significant global health care burden. Cytoglobin (CYGB), a globin family member expressed in HSCs, inhibits HSC activation and reduces collagen production. We studied the antifibrotic properties of globin family members hemoglobin (HB), myoglobin (MB), and neuroglobin (NGB) in comparison with CYGB.

Approach & results

We characterized the biological activities of globins in cultured human HSCs (HHSteCs) and their effects on carbon tetrachloride (CCl₄)-induced cirrhosis in mice. All globins demonstrated greater antioxidant capacity than glutathione in cell-free systems. Cellular fractionation revealed endocytosis of extracellular MB, NGB, and CYGB, but not HB; endocytosed globins localized to intracellular membranous, cytoplasmic, and cytoskeletal fractions. MB, NGB, and CYGB, but not HB, scavenged reactive oxygen species generated spontaneously or stimulated by H₂O₂ or transforming growth factor β1 in HHSteCs and reduced collagen 1A1 production via suppressing COL1A1 promoter activity. Disulfide bond-mutant NGB displayed decreased heme and superoxide scavenging activity and reduced collagen inhibitory capacity. RNA sequencing of MB- and NGB-treated HHSteCs revealed downregulation of extracellular matrix–encoding and fibrosis-related genes and HSC deactivation markers. Upregulation of matrix metalloproteinase (MMP)-1 was observed following MB and NGB treatment, and MMP-1 knockdown partially reversed globin-mediated effects on secreted collagen. Importantly, administration of MB, NGB, and CYGB suppressed CCl₄-induced mouse liver fibrosis.

Conclusions

These findings revealed unexpected roles for MB and NGB in deactivating HSCs and inhibiting liver fibrosis development, suggesting that globin therapy may represent a new strategy for combating fibrotic liver disease.

Myoglobin, neuroglobin, and cytoglobin, but not hemoglobin:•

Internalize into human hepatic stellate cells via endocytosis pathway.

•

Scavenge intracellular reactive oxidative species.

•

Suppress COL1A1 promoter activity and promote matrix metaloproteinase-1 secretion.

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Suppress carbon tetrachloride-induced mouse liver fibrosis.

Relation between Serum Creatine Phosphokinase Levels and Acute Kidney Injury among ST-Segment Elevation Myocardial Infarction Patients

Background: Among patients with rhabdomyolysis, the leakage of intracellular skeletal muscle content such as creatine phosphokinase (CPK) into the bloodstream has been associated with an increased risk of acute kidney injury (AKI). We evaluated the possible relationship between serum CPK levels and AKI occurrence among patients with myocyte injury secondary to ST-elevation myocardial infarction (STEMI). Methods: We retrospectively included 2794 patients with STEMI. Patients were stratified according to peak serum CPK levels into mild (<1000 U/L, n = 1603), moderate (1000–5000 U/L, n = 1111), and severe (>5000 U/L, n = 80) categories. The occurrence of AKI was defined by the KDIGO criteria as an increase in serum creatinine (sCR) ≥0.3 mg/dL within 48 h following PCI. The predictive value of CPK for the risk of AKI occurrence was assessed using multivariate logistic regression models. Results: The overall occurrence of AKI was 10.4%. Incidence of AKI showed a gradual increase between patients with mild, moderate, and severe serum CPK level elevations (7.8% vs. 11% vs. 26% respectively; p < 0.001). In multivariate logistic regression models, both moderate or higher (OR 1.6, 95% CI 1.1–2.2; p = 0.01) and severe (OR 2.8 95% CI 1.4–5.6; p = 0.004) serum CPK level elevations were independently associated with AKI. Conclusions: Among STEMI patients, elevated CPK levels were associated with AKI. This association is presumably independent; however, it remains unclear whether it is due to direct toxic (myoglobin-related) or hemodynamic effects (poor left ventricular function). Further studies are required to reveal the underlying mechanism.

Biophysical and mass spectrometry based characterization of methylglyoxal-modified myoglobin: Role of advanced glycation end products in inducing protein structural alterations

Methylglyoxal (MG) is a highly reactive α-dicarbonyl compound which reacts with proteins to form advanced glycation end products (AGEs). MG-induced AGE (MAGE) formation is particularly significant in diabetic condition. In the current study, we have undertaken a time-dependant characterization of MG-modified myoglobin following incubation of the heme protein with the α-dicarbonyl compound for different time periods. Interestingly, mass spectrometric studies indicated modifications at two specific lysine residues, Lys-87 and Lys-133. The AGE adducts identified at Lys-87 were carboxymethyllysine and carboxyethyllysine, while those detected at Lys-133 included pyrraline-carboxymethyllysine and carboxyethyllysine, respectively. Far-UV CD studies revealed a decrease in the native α-helical content of the heme protein gradually with increasing time of MG incubation. In addition, MG modification was found to induce changes in tertiary structure as well as surface hydrophobicity of the heme protein. MG-derived AGE adducts thus appear to alter the structure of Mb considerably. Considering the increased level of MG in diabetic condition, the current study appears physiologically relevant in terms of understanding AGE-mediated protein modification and subsequent structural changes.

Fatal Case of Rhabdomyolysis Post-COVID-19 Vaccine

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or COVID-19 pandemic has taken away the lives of many people (>4 million per WHO) around the world as of July 2021. With the advancement of the vaccine against COVID-19, in less than a year since the start of the pandemic, the infection rate has come under control in certain regions but is still rising in many more. However, with time, we are also learning a lot more about the adverse events related to the vaccine. This report documents the first fatal case of rhabdomyolysis potentially associated with the COVID-19 vaccine and supports the possibility that autoimmunity is a major risk factor for covid vaccine-related rhabdomyolysis.

Does melamine exposure during infancy cause rhabdomyolysis?

We investigated the possible toxic effects of melamine on muscle tissue in rats using biochemical, hematological and histopathological methods. We used three groups of female albino Wistar rats. The first group was given 0.1 ml saline. The second and third groups were given 50 and 75 mg/kg melamine dissolved in 0.1 ml saline, respectively, daily for 21 days. On day 45, all rats were sacrificed, and whole blood and plasma were analyzed for hematologic and biochemical characteristics. Muscle samples were stained with hematoxylin and eosin for histopathological investigation. Other sections were immunostained for matrix metalloproteinase-9 (MMP-9) and type IV collagen. We found a significant increase in the lymphocytosis-compliant leukocyte number in the 75 mg/kg melamine group compared to the other groups. We also found significant decreases in the hemoglobin levels and hematocrit values in the 75 mg/kg compared to the other groups. We found that the 75 mg/kg melamine group exhibited a significant increase in plasma aspartate aminotransferase (AST) activity compared to the other groups. Changes in plasma creatine kinase and lactate dehydrogenase activity were not statistically significant. Plasma AST activity and mean corpuscular hemoglobin levels were correlated with the lymphocyte:neutrophil ratio. We found mononuclear cell infiltration at the periphery of muscle bundles and in the connective tissue bundles in the melamine treated group. We found MMP-9 expression in muscle cell membranes and type IV collagen expression in degenerative connective tissue fibers. Whole blood, plasma and muscle tissue analysis indicated that the 75 mg/kg melamine group exhibited rhabdomyolysis that was associated with lymphocytosis and anemia. The underlying mechanisms by which melamine causes rhabdomyolytic effects remain unclear.

Growth differentiation factor 15 (GDF-15) is a potential biomarker of both diabetic kidney disease and future cardiovascular events in cohorts of individuals with type 2 diabetes: a proteomics approach

Background: Diabetic kidney disease (DKD) is a leading risk factor for end-stage renal disease and is one of the most important risk factors for cardiovascular disease in patients with diabetes. It is possible that novel markers portraying the pathophysiological underpinning processes may be useful.Aim: To investigate the associations between 80 circulating proteins, measured by a proximity extension assay, and prevalent DKD and major adverse cardiovascular events (MACE) in type 2 diabetes.Methods: We randomly divided individuals with type 2 diabetes from three cohorts into a two-thirds discovery and one-third replication set (total n = 813, of whom 231 had DKD defined by estimated glomerular filtration rate <60 mg/mL/1.73 m² and/or urinary albumin-creatinine ratio ≥3 g/mol). Proteins associated with DKD were also assessed as predictors for incident major adverse cardiovascular events (MACE) in persons with DKD at baseline.Results: Four proteins were positively associated with DKD in models adjusted for age, sex, cardiovascular risk factors, glucose control, and diabetes medication: kidney injury molecule-1 (KIM-1, odds ratio [OR] per standard deviation increment, 1.65, 95% confidence interval [CI] 1.27-2.14); growth differentiation factor 15 (GDF-15, OR 1.40, 95% CI 1.16-1.69); myoglobin (OR 1.57, 95% CI 1.30-1.91), and matrix metalloproteinase 10 (MMP-10, OR 1.43, 95% CI 1.17-1.74). In patients with DKD, GDF-15 was significantly associated with increased risk of MACE after adjustments for baseline age, sex, microalbuminuria, and kidney function and (59 MACE events during 7 years follow-up, hazard ratio per standard deviation increase 1.43 [95% CI 1.03-1.98]) but not after further adjustments for cardiovascular risk factors.Conclusion: Our proteomics approach confirms and extends previous associations of higher circulating levels of GDF-15 with both micro- and macrovascular disease in patients with type 2 diabetes. Our data encourage additional studies evaluating the clinical utility of our findings.

Volume Resuscitation in Patients With High-Voltage Electrical Injuries

Volume resuscitation of patients with high-voltage electrical injuries (>1000 V) is a more complex challenge than standard burn resuscitation. High voltages penetrate deep tissues. These deep injuries are not accounted for in resuscitation formulae dependent on percentage of cutaneous burn. Myonecrosis occurring from direct electrical injury and secondary compartment syndromes can result in rhabdomyolysis, compromising renal function and urine output. Urine output is the primary end point, with a goal of 1 mL/kg/h for adult patients with high-voltage electrical injuries. As such, secondary resuscitation end points of laboratory values, such as lactate, base deficit, hemoglobin, and creatinine, as well as hemodynamic monitoring, such as mean arterial pressure and thermodilution techniques, can become crucial in guiding optimum administration of resuscitation fluids. Mannitol and bicarbonates are available but have limited support in the literature. High-voltage electrical injury patients often develop acute kidney injury requiring dialysis and have increased risks of chronic kidney disease and mortality. Continuous venovenous hemofiltration is a well-supported adjunct to clear the myoglobin load that hemodialysis cannot from circulation.

Value and Use of Urinalysis for Myoglobinuria

Context.—

Urine myoglobin testing is primarily indicated for diagnosis and risk assessment of kidney injury in patients with rhabdomyolysis. However, its utility is limited by a lack of rapid and reliable results. Myoglobin reacts positively for blood by urine dipstick, which can serve as an indicator of myoglobinuria.

Objective.—

To evaluate the performance and value of blood and red cell measurements by urinalysis as a surrogate test for myoglobinuria in routine clinical practice.

Design.—

This study is a retrospective observational study involving analysis of hemoglobin and red blood cell results by urinalysis in patients tested for urine myoglobin.

Results.—

A total of 13 139 urine myoglobin results from 88 Veterans Affairs facilities during a 15-year period ending in October 2014 were evaluated. Among methods used by each laboratory, qualitative urine myoglobin tests declined from 25 of 53 (47.1%) in 2000 to 5 of 77 (6.4%) in 2013. Of 7311 tests (55.6%) performed by quantitative methods with concomitant urinalysis, 3915 (53.5%) showed negative to trace blood results, of which myoglobin was 1000 μg/L or greater in 17 (0.4%). Among 1875 (25.5%) with 3+ (large) blood results, urine myoglobin was ≥1000 μg/L in 273 of 1533 (17.8%) with hematuria (≥5 red blood cells per microliter) and 109 of 342 (31.9%) without hematuria.

Conclusions.—

Urinalysis results reliably predicted the absence of myoglobinuria and could be used to avert overtesting for urine myoglobin while also providing useful diagnostic information when urine myoglobin test results are not immediately available.

Australian elapid snake envenomation in cats: Clinical priorities and approach

Practical relevance: No fewer than 140 species of terrestrial snakes reside in Australia, 92 of which possess venom glands. With the exception of the brown tree snake, the venom-producing snakes belong to the family Elapidae. The venom of a number of elapid species is more toxic than that of the Indian cobra and eastern diamondback rattle snake, which has earned Australia its reputation for being home to the world's most venomous snakes. Clinical challenges: The diagnosis of elapid snake envenomation is not always easy. Identification of Australian snakes is not straightforward and there are no pathognomonic clinical signs. In cats, diagnosis of envenomation is confounded by the fact that, in most cases, there is a delay in seeking veterinary attention, probably because snake encounters are not usually witnessed by owners, and also because of the tendency of cats to hide and seek seclusion when unwell. Although the administration of antivenom is associated with improved outcomes, the snake venom detection kit and antivenom are expensive and so their use may be precluded if there are financial constraints. Evidence base: In providing comprehensive guidance on the diagnosis and treatment of Australian elapid snake envenomation in cats, the authors of this review draw on the published veterinary, medical and toxicology literature, as well as their professional experience as specialists in medicine, and emergency medicine and critical care.

Risk factors for exertional rhabdomyolysis with renal stress

Background

Exercise-induced rhabdomyolysis denotes the exertional damage of myocytes with leakage of sarcoplasmic content into the circulation. The purpose of this study was to determine important risk factors for the development of exertional rhabdomyolysis in a temperate climate and to study the renal effects of myoglobinuria.

Methods

A cluster of eight military recruits was admitted to hospital due to exertional rhabdomyolysis with myoglobinuria. The patients were treated according to current guidelines with isotonic saline and alkalinisation of the urine. The eight patients were compared with a randomly selected control group of 26 healthy fellow recruits. All subjects responded to a standardised questionnaire.

Results

There were little differences in baseline characteristics between patients and controls. In the present study, exercise intensity, duration and type were all significant determinants of exertional rhabdomyolysis in univariate models. However, in a multivariate model, high exercise intensity on day −1 was the only significant predictor of rhabdomyolysis (p=0.02). All patients had a stable serum creatinine and cystatin C. There was a significant increase in serum neutrophil gelatinase-associated lipocalin (NGAL) in the patients, suggesting renal stress.

Conclusions

Sustained maximal intensity exercise is a crucial risk factor for rhabdomyolysis with gross pigmenturia. Elevated serum NGAL concentrations indicate the presence of renal stress. It appears to be possible to quantify the risk of rhabdomyolysis by means of a simple questionnaire. In the future, this may be used as a tool to prevent rhabdomyolysis.

Nephrotoxicity of methadone: a systematic review

Background

Methadone is commonly administered for chronic pain relief and treatment of opioid dependence. Concurrent with its increased consumption, toxicities and fatalities have increased. One of the adverse effects of opioid analgesics, including methadone, is that of nephrotoxicity. Opioids can have an effect on renal function through several different mechanisms.

Methods

We searched common bibliographical databases for the terms methadone, toxicity, poisoning, kidney, renal, and nephrotoxicity and summarize our findings in this review.

Results

Methadone can have both direct and indirect effects on the kidney. These effects include rhabdomyolysis (leading to acute kidney injury), volumetric changes, renal lipidosis and amyloidosis, kidney growth during pregnancy, and kidney transplant rejection.

Conclusion

Improved understanding of the effects of methadone on kidney function can promote safer and more confident use of the drug.

Primary Myoglobinuria: Differentiate Myoglobinuria from Hemoglobinuria

Myoglobin is dark red colour heme containing protein, stored in muscle. Change in permeability of myolemma causes myoglobin leak in plasma, which is cleared by kidney swiftly. Differentiating myoglobinuria from hemoglobinuria is important. Clinicians concern over myoglobinuria is to protect the patient from acute renal disease. We present a case of primary myoglobinuria, its clinical symptoms, diagnosis and treatment.

Olanzapine overdose is associated with acute muscle toxicity

Olanzapine is an atypical antipsychotic that is reported to cause myopathy and raised creatine kinase (CK) levels. The prevalence and severity of acute myopathy after deliberate olanzapine ingestion are unclear. Therefore, we reviewed casenotes from 64 consecutive patients admitted to our institution after olanzapine overdose. Overall, serum CK was higher than five times the upper limit of normal in 17% of patients. The prevalence of raised CK values was positively correlated with the stated quantity of olanzapine ingested, suggesting a dose-dependent relationship for acute muscle toxicity. There was an apparent delay of 12 hours or more between olanzapine ingestion and the occurrence of maximum CK. Despite the high prevalence of acute muscle toxicity after olanzapine ingestion, none of the patients developed renal failure.

Rhabdomyolysis among acute human poisoning cases

Rhabdomyolysis is a clinical and biochemical syndrome occurring when skeletal muscle cells erupt and result in release of creatine phosphokinase (CPK), lactate dehydrogenase (LDH) and myoglobin into the interstitial space and plasma. Mechanical trauma, compression, excessive muscle activity and ischemia are frequent causes, but non-traumatic rhabdomyolysis is usually caused by a toxic reaction to drugs.

In this study, 181 patients suspected of rhabdomyolysis were admitted to the poisoning center of Loghman-Hakim Hospital in Tehran during one year (September 2004 to September 2005) were studied. Patients were included on the basis of physical examination and blood analysis for CPK and LDH. Rhabdomyolysis was confirmed if CPK level has been greater than 975 U/L. Out of 181 patients, 64 were female and 117 were male with an age range between 13—78 years. One-hundred and forty-three (79%) patients had CPK greater than 975 U/L. In 6% of the cases, multiple drug poisoning were observed. Two patients (1.1%) had muscle pain, five patients (2.8%) had rigidity and five patients (2.8%) had muscle inflammation. One-hundred and nineteen patients (65.7%) were febrile. The most common cause of rhabdomyolysis was opium. Blood ALT showed an increase in 109 patients (60.9%), AST in 80 patients (44.7%), and LDH in 144 patients (79.6%). Fifty patients (28.2%) had higher blood direct bilirubin and 64 patients (36.4%) showed higher total bilirubin. Six percent of patients had been diagnosed as ARF by indication of creatinine greater than 1.4 mg/dL. Five percent of patients had hypernatremia and 1.1% of patients had hyperkalemia.

It is concluded that rhabdomyolysis is a matter of concern in human poisonings and needs special approach to attend. Human & Experimental Toxicology (2007) 26: 557—561.

Methylglyoxal-induced modification causes aggregation of myoglobin

Post-translational modification of proteins by Maillard reaction, known as glycation, is thought to be the root cause of different complications, particularly in diabetes mellitus and age-related disorders. Methylglyoxal (MG), a reactive α-oxoaldehyde, increases in diabetic condition and reacts with proteins to form advanced glycation end products (AGEs) following Maillard-like reaction. We have investigated the in vitro effect of MG (200μM) on the monomeric heme protein myoglobin (Mb) (100μM) in a time-dependent manner (7 to 18days incubation at 25°C). MG induces significant structural alterations of the heme protein, including heme loss, changes in tryptophan fluorescence, decrease of α-helicity with increased β-sheet content etc. These changes occur gradually with increased period of incubation. Incubation of Mb with MG for 7days results in formation of the AGE adducts: carboxyethyllysine at Lys-16, carboxymethyllysine at Lys-87 and carboxyethyllysine or pyrraline-carboxymethyllysine at Lys-133. On increasing the period of incubation up to 14days, additional AGEs namely, carboxyethyllysine at Lys-42 and hydroimidazolone or argpyrimidine at Arg-31 and Arg-139 have been detected. MG also induces aggregation of Mb, which is clearly evident with longer period of incubation (18days), and appears to have amyloid nature. MG-derived AGEs may thus have an important role as the precursors of protein aggregation, which, in turn, may be associated with physiological complications.

Rhabdomyolosis and its pathogenesis

BACKGROUND

Rhabdomyolysis may cause severe damage to the human body because of acute renal failure, fatal heart rhythm disturbances, hypovolemic shock, disturbances of electrolyte balance, metabolic acidosis, hyperthermia, disseminated intravascular coagulation, etc. Drugs and toxins are the most common factors for the disease. This article aimed to review the prognosis of rhabdomyolysis.

DATA SOURCES

Based on the reported studies of cell and molecular biology, we reviewed the clinical presentations, laboratory findings, and mechanisms of rhabdomyolysis in the Pubmed.

RESULTS

The clinical symptoms of rhabdomyolysis were dependent on the severity of the condition and whether kidney failure develops. Since the necrosis and dissolution of muscle cells, entocytes such as myoglobin, creatine phosphokinase (CPK), electrolytes, proteins and non-protein substances were released into the plasma, the detection of the entocytes may contribute to the early diagnosis of rhabdomyolysis.

CONCLUSION

Despite the etiology of the disease is multifactorial, the potential causes of rhabdomyolysis share the same pathophysiological pathway involving an increase in intracellular calcium.

Myoglobinuria in Autopsy Pathology: Relevant and Potentially Unrecognized

Background

Myoglobin-related renal injury (MRRI) is a significant cause of acute renal injury and may result in death. Common etiologies in forensic pathology include trauma and drug abuse. This study sought to determine the prevalence and causes of MRRI at autopsy and discuss diagnostic challenges.

Methods

The institutional autopsy archives were queried for cases in which a myoglobin (MG) immunohistochemical stain was performed or MRRI was diagnosed or considered. The clinicopathological characteristics of this population were described.

Results

Of 9996 cases over a period of 19.5 years, 17 cases (0.2%) fulfilled the criteria. Patient age ranged from 15 to 74 years; 11 were men. The MG stain was performed in 13 cases. In 11 (65%) cases, MRRI was diagnosed with or without immunohistochemistry. The clinical backgrounds were varied; sepsis and liver injury predominated. Time between original insult and death ranged from seven hours to four months. Patterns of MRRI included cast formation or fine brush border staining in the proximal tubules.

Discussion

MRRI is infrequently considered in the autopsy setting. Many causes of MRRI identified in this series involved circumstances placing the death into medical examiner jurisdiction; the MG stain contributed to understanding the mechanism of death. Acute tubular injury with cast formation was observed in the majority of cases.

Conclusion

MRRI is common in a select group of autopsies but may be underappreciated. The MG stain is a useful and inexpensive tool to aid in the diagnosis of MRRI in autopsy pathology.

Acute kidney injury due to rhabdomyolysis and renal replacement therapy: a critical review

Rhabdomyolysis, a clinical syndrome caused by damage to skeletal muscle and release of its breakdown products into the circulation, can be followed by acute kidney injury (AKI) as a severe complication. The belief that the AKI is triggered by myoglobin as the toxin responsible appears to be oversimplified. Better knowledge of the pathophysiology of rhabdomyolysis and following AKI could widen treatment options, leading to preservation of the kidney: the decision to initiate renal replacement therapy in clinical practice should not be made on the basis of the myoglobin or creatine phosphokinase serum concentrations.

Myoglobinuria as first clinical sign of a primary alpha-sarcoglycanopathy

Myoglobinuria is a frequent complication of metabolic myopathies and may also occur in Duchenne and Becker dystrophies but is not a typical sign of limb-girdle muscular dystrophy. We describe an unusual presentation of alpha-sarcoglycanopathy with myoglobinuria at the onset of the disease. The boy presented an episode of dark urine, identified as presence of blood by a urine dipstick, occurred 10 days after an episode of fever and sore throat treated with antibiotics. He was admitted to the hospital and investigated for post-infectious nephritis, but further analysis revealed the presence of myoglobinuria. Immunohistochemistry on muscle tissue revealed absent expression of α-sarcoglycan confirmed by detection of a homozygous mutation in the alpha-sarcoglycan gene. Myoglobinuria has been previously reported four times in sarcoglycanopathies but only once in alpha-sarcoglycanopathy.

CONCLUSION

The present observation reinforces the idea that the myoglobinuria should be considered a manifestation of a primary sarcoglycanopathy even as the only recognizable sign at the debut of the disease.

Drug induced rhabdomyolysis

Rhabdomyolysis is a clinical condition of potential life threatening destruction of skeletal muscle caused by diverse mechanisms including drugs and toxins. Given the fact that structurally not related compounds cause an identical phenotype pinpoints to common targets or pathways, responsible for executing rhabdomyolysis. A drop in myoplasmic ATP paralleled with sustained elevations in cytosolic Ca²⁺ concentration represents a common signature of rhabdomyolysis. Interestingly, cardiac tissue is hardly affected or only secondary, as a consequence of imbalance in electrolytes or acid–base equilibrium.

This dogma is now impaired by compounds, which show up with combined toxicity in heart and skeletal muscle. In this review, cases of rhabdomyolysis with novel recently approved drugs will be explored for new target mechanisms in the light of previously described pathomechanisms.

Management of critical illness polyneuropathy and myopathy

A syndrome of generalized weakness, areflexia, and difficulty with weaning from a ventilator is a common clinical presentation in the critically ill patient, especially in the setting of sepsis, multiorgan failure, and hyperglycemia. At first believed to be a manifestation of nerve (critical illness neuropathy, CIN) or muscle (critical illness myopathy, CIM) dysfunction, our current conceptualization is as a spectrum (critical illness neuromuscular abnormalities, CINMA) that varies in extent and site(s) of involvement, but often a similar clinical presentation. Signs and symptoms of CINMA must be identified early to foster recovery and limit morbidity and mortality. The medical history is crucial in excluding preexisting neuromuscular conditions and electrodiagnostic testing helps to establish the diagnosis and prognostication. A stepwise approach to the management of a patient with CINMA is outlined, but avoiding potential medications, and ensuring supportive care are the primary interventions to consider. Recently intensive insulin therapy for hyperglycemia has been shown to lower the risk of CINMA and decrease the time of ventilatory support, but with a greater risk of hypoglycemia. Future therapeutic interventions will require a better understanding of disease pathogenesis, but may target proinflammatory cytokine and free-radical pathways, muscle gene expression, ion channel function, or proteolytic muscle protein mechanisms. Rehabilitation is an equally essential component in a patient's management. Although prognosis depends on the extent of the underlying muscle and nerve damage, mild persistent deficits are common and severe disability may be persistent.

Rhabdomyolysis

Rhabdomyolysis is a syndrome involving the breakdown of skeletal muscle causing myoglobin and other intracellular proteins and electrolytes to leak into the circulation. The development of rhabdomyolysis is associated with a wide variety of diseases, injuries, medications and toxins. While the exact mechanisms responsible for all the causes are not fully understood, it is clear that muscle damage can occur from direct injury or by metabolic inequalities between energy consumption and energy production. Rhabdomyolysis is diagnosed by elevations in serum creatine phosphokinase (CPK), and while there is no established serum level cut-off, many clinicians use five times the upper limit of normal ( approximately 1000 U/l). Rhabdomyolysis can be complicated by acute renal failure (occurring in 4%-33% of patients), compartment syndrome, cardiac dysrhythmias via electrolyte abnormalities, and disseminated intravascular coagulopathy. The mainstay of treatment is hospitalisation with aggressive intravenous fluid (IVF) resuscitation with the correction/prevention of electrolyte abnormalities. There are additional adjunctive therapies to IVF, such as alkalinisation of the urine with sodium bicarbonate, diuretic therapy or combinations of both; however the lack of large randomised control studies concerning the benefits of these treatments makes it difficult to make strong recommendations for or against their use in the treatment of rhabdomyolysis. Regardless of these controversies, the overall prognosis for rhabdomyolysis is favourable when treated with early and aggressive IVF resuscitation, and full recovery of renal function is common. Irrespective of the cause of rhabdomyolysis the mortality rate may still be as high as 8%. This is a comprehensive review of the pathophysiology, diagnosis, complications and treatment options for rhabdomyolysis.

Diagnostic potential for urinary proteomics

Urine represents a modified ultrafiltrate of plasma, with protein concentrations typically approximately 1000-fold lower than plasma. Urine’s low protein concentration might suggest it to be a less promising diagnostic specimen than plasma. However, urine can be obtained noninvasively and tests of many urinary proteins are well-established in clinical practice. Proteomic technologies expand opportunities to analyze urinary proteins, identifying more than 1000 proteins and peptides in urine. Urine offers a sampling of most plasma proteins, with increased proportions of low-molecular-weight protein and peptide components. Urine also offers enriched sampling of proteins released along the urinary tract. Although urine presents some challenges as a diagnostic specimen, its diverse range of potential markers offers great potential for diagnosis of both systemic and kidney diseases. Examples of clinical situations where this may be of value are for more sensitive detection of kidney transplant rejection or of renal toxicity of medications.

Anuric renal failure in a dog after Red-bellied Black snake (Pseudechis porphyriacus) envenomation

A case of Red-bellied Black snake envenomation resulting in intravascular haemolytic anaemia, rhabdomyolysis and anuric renal failure is described in the dog. A 12-year-old female desexed Golden Retriever was presented with a 15 hour history of profuse salivation, progressive lethargy, obtundence, inappetence and collapse. Significant findings on clinical examination were pallor, icterus, tachypnoea and dyspnoea with increased respiratory sounds and crackles in all lung fields. Generalised abdominal and muscular pain was apparent and dark red-brown urine was present around the perineal region. A diagnosis of Red-bellied Black snake (Pseudechis porphyriacus) envenomation was made and the dog was treated with intravenous fluid therapy, Tiger/Brown snake antivenom, packed red cell transfusions and Intermittent Positive Pressure Ventilation. Continued clinical deterioration occurred and a diagnosis of acute renal failure secondary to myohaemoglobinuric pigmenturia was made 12 hours after admission. Intensive treatment was attempted with diuresis and volume expansion. Oliguria and subsequent anuria ensued and the dog was euthanased due to a grave prognosis and lack of clinical response to treatment. Necropsy examination revealed muscular necrosis, accumulation of fluid in the thoracic and peritoneal cavities, and marked renal tubular necrosis with intraluminal occlusion secondary to pigmentary casts.

Rhabdomyolysis in patients with west nile encephalitis and meningitis

Since 1999, more than 6,500 cases of West Nile virus neuroinvasive disease (WNND) have been reported in the United States. Patients with WNND can present with muscle weakness that is often assumed to be of neurological origin. During 2002, nearly 3,000 persons with WNV meningitis or encephalitis (or both) were reported in the United States; in suburban Cook County, Illinois, with 244 persons were hospitalized for WNV illnesses. The objective of this investigation was to describe the clinical and epidemiological features of identified cases of WNV neuroinvasive disease and rhabdomyolysis. Public health officials investigated patients hospitalized in Cook County, and identified a subset of WNV neuroinvasive disease patients with elevated creatine kinase levels. Cases were defined as hospitalized persons with a WNV infection, encephalitis or meningitis, and rhabdomyolysis. Retrospective medical record reviews were conducted and data was abstracted with a standardized data collection instrument. Eight patients with West Nile encephalitis and one with West Nile meningitis were identified with rhabdomyolysis. Median age of the nine patients was 70 years (range, 45-85 years), and eight were men. For all nine patients, the peak CK level was documented a median of 2 days after hospitalization (range, 1-24 days). Median CK level during hospitalization for all case-patients was 3,037 IU (range, 1,153-42,113 IU). Six patients had history of recent falls prior to admission. Although the temporal relationship of rhabdomyolysis and neurological WNV illness suggested a common etiology, these patients presented with complex clinical conditions which may have led to development of rhabdomyolysis from other causes. The spectrum of WNV disease requires further investigation to describe this and other clinical conditions associated with WNV infection.

Pathophysiology and clinical presentations of rhabdomyolysis

Rhabdomyolysis has sparked new interest in recent years. The causes of rhabdomyolysis include drugs and other toxic agents, infections, physical exertion, crush injury, and muscle diseases (dystrophinopathies and metabolic myopathies). Prompt identification of the pathophysiological mechanism is the key to rapid control of the acute episode and to prevention of recurrences. In this update, we discuss the pathophysiological mechanisms and nosology of rhabdomyolysis, as well as diagnostic investigations, with special emphasis on noninvasive methods.

Neuromuscular manifestations of critical illness

Critical illness, more precisely defined as the systemic inflammatory response syndrome (SIRS), occurs in 20%-50% of patients who have been on mechanical ventilation for more than 1 week in an intensive care unit. Critical illness polyneuropathy (CIP) and myopathy (CIM), singly or in combination, occur commonly in these patients and present as limb weakness and difficulty in weaning from the ventilator. Critical illness myopathy can be subdivided into thick-filament (myosin) loss, cachectic myopathy, acute rhabdomyolysis, and acute necrotizing myopathy of intensive care. SIRS is the predominant underlying factor in CIP and is likely a factor in CIM even though the effects of neuromuscular blocking agents and steroids predominate in CIM. Identification and characterization of the polyneuropathy and myopathy depend upon neurological examination, electrophysiological studies, measurement of serum creatine kinase, and, if features suggest a myopathy, muscle biopsy. The information is valuable in deciding treatment and prognosis.

Protein reabsorption in renal proximal tubule-function and dysfunction in kidney pathophysiology

The endocytic receptors megalin and cubilin are highly expressed in the early parts of the endocytic apparatus of the renal proximal tubule. The two receptors appear to be responsible for the tubular clearance of most proteins filtered in the glomeruli. Since cubilin is a peripheral membrane protein it has no endocytosis signaling sequence. Cubilin binds to megalin and it appears that megalin is responsible for internalization of cubilin and its ligands, in addition to internalizing its own ligands. The importance of the receptors is underscored by the proteinuria observed in megalin-deficient mice, in dogs lacking functional cubilin, and in patients with distinct mutations of the cubilin gene. In this review we focus on the role of megalin- and cubilin-mediated endocytosis in renal pathophysiology. Association between disorders characterized by tubular proteinuria, such as megaloblastic anemia type-1, Dent disease, cystinosis, and Fabry disease and the dysfunction of proximal tubular endocytosis is discussed. The correlation between the high capacity of endocytosis in the proximal tubule and progressive renal disease in overload proteinuria is considered.

Renal uptake of myoglobin is mediated by the endocytic receptors megalin and cubilin

Nephrotoxicity of myoglobin is well recognized as playing a part in the development of acute renal failure in settings of myoglobinuria. However, the molecular mechanism of myoglobin uptake in renal proximal tubules has not been clarified. Here, we report that the endocytic receptors megalin and cubilin are involved in renal reabsorption of myoglobin. Both receptors were captured from solubilized renal brush-border membranes by affinity chromatography using myoglobin-Sepharose. Myoglobin bound to purified megalin and cubilin with Kd values of 2.0 and 3 microM, respectively, as evaluated by surface plasmon resonance analysis. Apomyoglobin bound to megalin with the same affinity, and the affinity of apomyoglobin to cubilin was reduced (Kd = 5 microM). Radioiodinated myoglobin could be displaced by apomyoglobin in inhibition studies using isolated renal brush-border membranes (Ki approximately 2 microM). Receptor-associated protein as well as antibodies directed against megalin and cubilin markedly inhibited the uptake of fluorescent-labeled myoglobin by cultured yolk sac BN-16 cells. The significance of megalin- and cubilin-mediated endocytosis for myoglobin uptake in vivo was demonstrated by use of kidney-specific megalin knockout mice. Injected myoglobin was extensively reabsorbed by megalin-expressing proximal tubular cells, whereas there was very little uptake in the megalin-deficient cells. In conclusion, this study establishes the molecular mechanism of myoglobin uptake in the renal proximal tubule involving the endocytic receptors megalin and cubilin. Identification of the receptors for tubular uptake of myoglobin may be essential for development of new therapeutic strategies for myoglobinuric acute renal failure.

Pyruvate attenuates myoglobin in vitro toxicity

Myoglobinuria is a complication of crush injury as well as substance abuse. This study examined whether pyruvate modified myoglobin in vitro renal toxicity. Renal slices from Fischer-344 rats were incubated for 120 min with 0-12 mg/ml myoglobin. In an initial study, gluconeogenesis was stimulated by the addition of 10 mM pyruvate during the final 30 min. In all other studies, renal slices were incubated with myoglobin in the presence of 0 or 10 mM pyruvate for 120 min. Myoglobin increased lactate dehydrogenase (LDH) release and this was not modified by the presence of pyruvate for the last 30 min of the incubation. Myoglobin toxicity was reduced by coincubation of myoglobin with pyruvate for 120 min. LDH leakage was increased 1.2-, 1.7-, and 1.8-fold above control by 4, 10, and 12 mg/ml myoglobin, compared to 1.2, 1.3, and 1.3 fold in slices coincubated with 10 mM pyruvate, respectively. Myoglobin diminished adenosine triphosphate (ATP) levels but pyruvate maintained a 5x higher level of ATP within the slices. Glucose (10 mM) provided protection only for the low concentration (4 mg/ml) of myoglobin. Myoglobin induced oxidative stress while pyruvate prevented the rise in lipid peroxidation and glutathione disulfides by myoglobin. Myoglobin diminished total glutathione levels in pyruvate-treated tissue, but glutathione levels remained higher than tissues incubated in the absence of pyruvate. These results indicate that pyruvate reduced toxicity by preventing oxidative stress and via a supply of an energy substrate.

Serum creatine kinase as predictor of clinical course in rhabdomyolysis: a 5-year intensive care survey

OBJECTIVE

To evaluate the risk factors for the development of acute renal failure (ARF) in severe rhabdomyolysis.

DESIGN

Observational historical cohort study.

SETTING

General intensive care unit of a university hospital.

PATIENTS

Twenty-six patients with severe rhabdomyolysis, who were admitted between July 1996 and July 2001.

MEASUREMENTS AND RESULTS

Clinical and laboratory data were reviewed and groups were stratified according to presence or absence of acute renal failure. The underlying cause of rhabdomyolysis was ischemia by vascular obstruction (50%), crush injury by trauma (23%), sepsis (11.5%), heatstroke/hyperthermia (11.5%) and hyponatremia in a single patient. Mean creatine kinase (CK) level was 38,351+/-35,354 U/l on admission and rose further in all patients (mean: 59,747+/-67,514 U/l). Renal failure developed in 17 patients (65%). Serum CK levels correlated with onset of ARF, as these patients had significantly higher admission and peak serum CK concentrations. Patients with ARF had a higher mortality (59% vs 22%).

CONCLUSION

In our cohort of patients with severe rhabdomyolysis the level of serum CK predicted the development of ARF. Although our results suggest that series of CK determination might be beneficial for the evaluation of the effect of therapy, the value of CK determination as a prognostic tool is limited, given the wide range of CK levels.

[Rhabdomyolysis and myoglobinuria]

Rhabdomyolysis is a disorder characterized by acute damage of the sarcolemma of the skeletal muscle leading to release of potentially toxic muscle cell components into the circulation, most notably creatine phosphokinase (CK) and myoglobin, and is frequently accompanied by myoglobinuria. Therefore, the term myoglobinuria is often used interchangeably with the term rhabdomyolysis. This disorder may result in potential life-threatening complications such as acute myoglobinuric renal failure, hyperkalemia and cardiac arrest, disseminated intravascular coagulation, and compartment syndrome. The condition is etiologically heterogeneous and may result from a large variety of diseases affecting muscle membranes, membrane ion channels, and muscle energy supply including acquired causes (e.g., exertion, crush injury and trauma, alcoholism, drugs, and toxins) and hereditary causes (e.g., disorders of carbohydrate metabolism, disorders of lipid metabolism, or diseases of the muscle associated with malignant hyperthermia). In many patients with idiopathic recurrent rhabdomyolysis, specific inherited metabolic defects have not been recognized up to now.

Characterization of myoglobin toxicity in renal cortical slices from Fischer 344 rats

Rhabdomyolysis is associated with acute renal failure. The following study first characterized myoglobin in vitro toxicity using renal cortical slices isolated from male Fischer 344 rats. This model provided interaction between various cells within the nephron and provides myoglobin access predominantly through the basolateral membrane. Second, this study examined the effect of deferoxamine (DFX) and glutathione on myoglobin toxicity to determine the role of radicals and iron. Renal cortical slices were incubated for 30-120 min with 0, 4, 10 or 12 mg/ml myoglobin. Myoglobin was pretreated with 4 mM ascorbic acid prior to addition to the slices to ensure that myoglobin was in its reduced state. In other experiments tissues were pretreated for 15 min with 0.1 mM of the iron chelator DFX or 30 min with 1 mM glutathione prior to co-incubation with myoglobin. Finally, slices were pretreated with 1 mM glutathione for 30 min, rinsed and incubated only with myoglobin. Early event changes occurred within a 60 min exposure and included a decline in pyruvate-stimulated gluconeogenesis, increased lipid peroxidation levels and decreased glutathione levels. Loss of ATP levels and increased lactate dehydrogenase (LDH) release required a 120 min exposure to myoglobin. DFX reduced myoglobin induced effects on LDH leakage but had no effect on gluconeogenesis suggesting that myoglobin toxicity had an iron dependent (LDH) and independent (gluconeogenesis) pathway. Pretreatment with glutathione provided complete protection and was mediated by intracellular events.

Cyproheptadine for intrathecal baclofen withdrawal

OBJECTIVE

To evaluate the efficacy of cyproheptadine in the management of acute intrathecal baclofen (ITB) withdrawal.

DESIGN

Descriptive case series.

SETTING

University hospital with a comprehensive in- and outpatient rehabilitation center.

PARTICIPANTS

Four patients (3 with spinal cord injury, 1 with cerebral palsy) with implanted ITB infusion pumps for treatment of severe spasticity, who had ITB withdrawal syndrome because of interruption of ITB infusion.

INTERVENTIONS

Patients were treated with 4 to 8mg of cyproheptadine by mouth every 6 to 8 hours, 5 to 10mg of diazepam by mouth every 6 to 12 hours, 10 to 20mg of baclofen by mouth every 6 hours, and ITB boluses in some cases.

MAIN OUTCOME MEASURES

Clinical signs and symptoms of ITB withdrawal of varying severity were assessed by vital signs (temperature, heart rate), physical examination (reflexes, tone, clonus), and patient report of symptoms (itching, nausea, headache, malaise).

RESULTS

The patients in our series improved significantly when the serotonin antagonist cyproheptadine was added to their regimens. Fever dropped at least 1.5 degrees C, and heart rate dropped from rates of 120 to 140 to less than 100bpm. Reflexes, tone, and myoclonus also decreased. Patients reported dramatic reduction in itching after cyproheptadine. These changes were associated temporally with cyproheptadine dosing.

DISCUSSION

Acute ITB withdrawal syndrome occurs frequently in cases of malfunctioning intrathecal infusion pumps or catheters. The syndrome commonly presents with pruritus and increased muscle tone. It can progress rapidly to high fever, altered mental status, seizures, profound muscle rigidity, rhabdomyolysis, brain injury, and death. Current therapy with oral baclofen and benzodiazepines is useful but has variable success, particularly in severe cases. We note that ITB withdrawal is similar to serotonergic syndromes, such as in overdoses of selective serotonin reuptake inhibitors or the popular drug of abuse 3,4-methylenedioxymethamphetamine (Ecstasy). We postulate that ITB withdrawal may be a form of serotonergic syndrome that occurs from loss of gamma-aminobutyric acid B receptor-mediated presynaptic inhibition of serotonin.

CONCLUSION

Cyproheptadine may be a useful adjunct to baclofen and benzodiazepines in the management of acute ITB withdrawal syndrome.