Electrolyte disturbances in foals with severe rhabdomyolysis

Methodology-related pseudohyperkalemia associated with marked muscle enzyme leakage in a dog

BACKGROUND

As hyperkalemia may be life-threatening, it is critical to recognize artifactually increased potassium concentrations. Pseudohyperkalemia may occur in myopathies when using the VetScan2 analyzer (VS2), but the degree of pseudohyperkalemia and relationships relative to creatine kinase activity (CK) are unknown.

OBJECTIVES

We aimed to determine what degree of muscle enzyme leakage, as reflected by increased serum CK activity, results in cases with falsely elevated potassium concentrations when measured by the VS2. We also sought to establish if a linear relationship exists between potassium concentrations measured by the VS2 and CK activity.

METHODS

Serum samples from dogs with increased CK activity and with CK activity within the reference interval and without clinically relevant biochemical alterations were used to create diluted samples having various CK activities. Potassium concentrations and CK activities were determined on VS2 and Cobas c501 (Cobas) analyzers. Wilcoxon signed rank, Bland-Altman, and Passing-Bablok analyses were used to compare potassium concentrations generated by the VS2 and Cobas analyzers. Least squares regression analysis was performed to evaluate if a linear relationship exists between VS2 potassium concentrations and Cobas CK activities.

RESULTS

Potassium concentrations from the VS2 were higher (median and standard deviation (SD) = 5.2 +/- 0.46 mmol/L) than those from the Cobas analyzer (4.4 +/- 0.35 mmol/L; P < 0.000), and a positive mean bias was found (mean difference = 0.774 mmol/L; 95% Confidence Interval (CI) = 0.706-0.842; limits of agreement = 0.21-1.34). Passing-Bablok regression showed a positive proportional bias for potassium concentrations on the VS2 compared with paired Cobas results (Slope = 1.328; 95% CI = 1.100-1.500) but did not reveal systematic bias (Intercept = -0.714; 95% CI = -1.46-0.265). Least squares regression analysis showed a poor non-significant relationship (R2  = 0.19) between potassium measured by the VS2 and CK measured by the Cobas analyzer.

CONCLUSIONS

A defined threshold value of CK activity at which potassium concentration begins to falsely increase when measured on the VS2 was not established as data widely varied. A poor non-significant relationship between potassium concentrations and CK activities did not allow prediction of the threshold at which falsely increased potassium concentrations would be expected on the VS2.

Suspected vagal reflex and hyperkalaemia inducing asystole in an anaesthetised horse

A 10‐year‐old 466 kg mustang gelding presented to an equine referral hospital for surgical repair of nasal, frontal and lacrimal bone fractures from an unknown trauma. Surgical repair was performed under general anaesthesia, including a right‐sided maxillary regional anaesthetic block with mepivacaine hydrochloride. Progressive hyperkalaemia was documented perianaesthetically (T‐3 mins; 134 mins after induction; potassium 6.4 mmol/L (ref 3.5‐5.1 mmol/L). Perianaesthetic bradycardia was attributed to alpha −2 agonist infusion administration, and other characteristic ECG changes (flattened P waves, narrow T waves of increased amplitude, prolonged QRS complex) were not documented. Asystole occurred 137 min after induction of anaesthesia; however, a review of the available literature suggests the degree of hyperkalaemia documented was unlikely to be the primary cause of asystole but may have been a contributing factor. It is hypothesised that a trigeminocardiac reflex was the primary contributory factor to asystole in the described case, and may represent a maxillomandibulocardiac reflex that has not been previously described in the horse.

Rhabdomyolysis and Acute Renal Failure Associated with Oxytetracycline Administration in Two Neonatal Foals Affected by Flexural Limb Deformity

Oxytetracycline (OTC) administration has become a frequent practice in equine neonatology for the treatment of flexural limb deformity. The cause of this condition remains unclear but clinical studies revealed that following IV administration of OTC a relaxation of the metacarpophalangeal joint occurs in foals affected by flexural deformity. Studies concluded that OTC administration in neonatal foals did not adversely affect the kidneys. Other adverse effects of OTC have never been reported. This report presents two cases with different outcomes of 3-day-old foals which presented acute collapse and progressive depression after OTC administration. The clinical aspects, the increased activity of serum enzymes indicative of muscular damage, the presence of myoglobin in urine were clear diagnostic indicators of severe rhabdomyolysis, and the gross and histological findings confirmed a myopathy associated with renal damage in one case. Adverse effects on the musculoskeletal and urinary systems in healthy foals were first reported and were probably associated with multiple doses administered to foals less than 24–48 h old and/or at dosing intervals less than 24–48 h. The risk of development of rhabdomyolysis and nephrotoxicity in neonatal foals treated with OTC for flexural deformity from now on should be considered.

Retrospective evaluation of the association between hyponatremia and neurological dysfunction in hospitalized foals (2012-2016): 109 cases

OBJECTIVE

Hyponatremia and rapid correction of hyponatremia can lead to neurological abnormalities. The objective of the study was to determine whether plasma sodium concentrations (Na⁺ ) and speed of correction of hyponatremia are significantly associated with neurological abnormalities in foals.

DESIGN

Retrospective cohort study 2012 to 2016.

SETTING

Equine hospital.

ANIMALS

One hundred and nine foals <6 months old with hyponatremia (Na⁺ concentration ≤125 mmol/L).

INTERVENTIONS

Case records were reviewed for any foal with hyponatremia. Clinicopathological findings, presence or absence of neurological signs on the day of the lowest Na⁺ concentration measured and the following 5 days, diagnosis and outcome were recorded, and changes in Na⁺ concentration per hour were calculated for up to 5 subsequent days. Logistic regression was used to assess the association between presence or absence of neurological signs, Na⁺ concentration, other known risk factors for neurological dysfunction in foals, and possible confounders.

MEASUREMENTS AND MAIN RESULTS

In the final multivariable model, only Na⁺ (odds ratio [OR]: 0.86; 95% CI 0.79-0.95; P = 0.002) and BUN concentrations (OR: 1.04; 95% CI: 1.02-1.06; P = 0.001) were significantly associated with neurological signs. Changes in Na⁺ concentrations per hour were not associated with neurological signs on any day after the lowest Na⁺ concentration had been measured (P = 0.18-0.82), and development of new neurological signs following correction of hyponatremia was not reported in any foal.

CONCLUSIONS

Na⁺ concentrations were associated with the development of neurological signs in hyponatremic foals. Increased BUN concentrations might contribute to neurological dysfunction, but further studies are necessary to confirm or refute these findings.

Acute kidney injury secondary to traumatic rhabdomyolysis in a dog

OBJECTIVE

To describe the clinical course and successful management of a dog with crush syndrome, rhabdomyolysis, myoglobinuria, and associated acute kidney injury (AKI).

CASE SUMMARY

An 8-year-old female, neutered, mixed-breed dog was referred to the Veterinary Teaching Hospital due to crush injury and suspected AKI. Blood tests and urinalysis showed markedly increased serum creatine kinase activity, myoglobinuria, and AKI. The dog was managed successfully with intermittent hemodialysis, and completely recovered.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first report of a dog with crush syndrome with secondary myoglobinuria and AKI.

Rhabdomyolysis and Artifactual Increase in Plasma Bicarbonate Concentration in an Amazon Parrot (Amazona species)

A 7-year-old male Amazon parrot housed outdoors presented with acute collapse, marked lethargy, and open-mouth breathing. The patient had stiffness of the pectoral muscles, and petechiation and ecchymosis noted around the eyes and beneath the mandible. Laboratory data revealed markedly increased aspartate aminotransferase, creatine kinase, and lactate dehydrogenase activity consistent with rhabdomyolysis, as well as markedly increased plasma bicarbonate concentration. Marked clinical improvement and resolution of laboratory abnormalities occurred with fluid therapy, administration of a nonsteroidal anti-inflammatory medication, and husbandry modifications, including indoor housing and dietary alteration. A spurious increase in bicarbonate measurement as documented in equine and bovine cases of rhabdomyolysis also occurred in this avian patient and must be considered for accurate interpretation of acid-base status in exotic species presenting with consistent clinical signs.

Severe hyponatraemia in foals: clinical findings, primary diagnosis and outcome

OBJECTIVE

To evaluate severe hyponatraemia in foals presenting as medical emergencies to an intensive care unit (ICU) in order to determine the prevalence, clinical findings, primary diagnosis and outcome.

DESIGN

Retrospective case study of records from Thoroughbred foals aged less than 3 months presenting to an ICU as medical emergencies in 2002-12; foals with severe hyponatraemia (serum sodium <122 mmol/L) on admission laboratory data were identified. Data retrieved included signalment, clinical findings, laboratory results, primary diagnosis, treatment and outcome.

RESULTS

Severe hyponatraemia was identified in 69/1718 Thoroughbred foals (4%) presenting to the ICU during the study period. Of the 69 foals, 11 (15.9%) presented with neurological signs attributable to hyponatraemic encephalopathy and 7 of these foals had seizures; other neurological signs included obtundation, ataxia and apparent blindness. The three most common primary diagnoses of the 69 foals with severe hyponatraemia were renal disease (18/69, 26.1%), enterocolitis (16/69, 23.2%) and uroperitoneum (15/69, 21.7%). Treatment was directed at the primary disease and correction of the hyponatraemia. A total of 50 of the 69 foals (72.5%) with severe hyponatraemia survived to hospital discharge and 38 of them (76%) survived at least 12 months following discharge.

CONCLUSION

The prevalence of severe hyponatraemia in this study population was 4%. The majority of foals with severe hyponatraemia did not demonstrate direct clinical manifestations as a result of the low serum sodium concentration. The outcome of foals with severe hyponatraemia was mostly favourable.

Surgical Removal of a Canine Aortic Thromboembolism Secondary to Pancreatitis

A 7-year-old castrated male Pomeranian was evaluated on emergency for diagnostic work-up and treatment for acute nonpainful paraparesis. The neurologic examination suggested a L4-S3 myelopathy, but physical examination revealed lack of femoral pulses and rectal hypothermia, as well as a grade II/VI systolic heart murmur, so ischemic neuromyopathy was suspected. Clinicopathologic analysis revealed increased muscle enzymes and proteinuria. Abdominal ultrasonography confirmed aortic thromboembolism (ATE), and surgical histopathology diagnosed necrotizing pancreatitis. Surgical aortic thrombectomy was performed, and antithrombotic therapy was instituted. Pancreatitis was treated supportively. The dog was discharged to the owners after 10 days of hospitalization. Recheck examination 6 weeks after initial presentation revealed a normal neurologic examination and normal femoral pulses. The patient has had no further bouts of pancreatitis and remains neurologically normal 5 years after initial presentation. Canine ATE is relatively rare compared to the feline counterpart. Directed therapy for feline ATE is often not recommended, as underlying conditions are oftentimes ultimately fatal. Underlying etiologies for canine ATE include cardiovascular disease and endocrinopathies, but canine ATE secondary to pancreatitis has not yet been reported. Surgical removal of aortic thromboembolus should be considered as curative for pelvic limb dysfunction in the canine patient without a terminal underlying disease.

Traditional and quantitative assessment of acid-base and shock variables in horses with atypical myopathy

BACKGROUND

Descriptions of acid-base disturbances in atypical myopathy (AM) are limited.

OBJECTIVES

Describe and compare traditional and quantitative acid-base abnormalities and cardiovascular shock status in horses with AM at admission.

ANIMALS

34 horses with AM, 15 healthy controls.

METHODS

Retrospective case-control study. Records were searched for shock variables (packed cell volume [PCV], blood urea nitrogen [BUN], heart and respiratory rate) and acid-base variables (venous blood gas analysis, electrolytes, total protein, lactate) on admission. Base excess (BE) of free water (BEfw), chloride (BEcl), total protein (BEtp), and unidentified anions (BEua), anion gap (AG), measured strong ion difference (SIDm), and concentration of total nonvolatile weak acids ([Atot]) were calculated. Acid-base classifications, using simplified strong ion model and traditional approach, and shock grades were assigned. A 2-sample Wilcoxon rank-sum test and Bonferroni correction compared variables in AM cases versus control horses. Significance was P < .05/16 for acid-base and P < .05/5 for shock variables.

RESULTS

Tachycardia, tachypnea, and normal to increased PCV and BUN were common in AM cases. Respiratory, metabolic acid-base alterations, or both were mainly caused by respiratory alkalosis, lactic acidosis, and SIDm alkalosis, alone or in combination. Evaluated variables (except pH, potassium concentration, total protein, and related calculations) were significantly different (P < .001) between AM cases and control horses. The strong ion model provided a more accurate assessment than the traditional approach and identified mixed derangements.

CONCLUSIONS AND CLINICAL IMPORTANCE

Acid-base derangements should be evaluated in horses with AM and this preferably with the strong ion model.

The absorption of natural vitamin C in horses and anti-oxidative capacity: a randomised, controlled study on trotters during a three-month intervention period

The primary aim of the present study was to assess whether low dose vitamin C supplemented in its natural form, as a dried powder from selected subspecies of rosehip (Rosa canina), would result in a detectable increase in the concentration of blood vitamin C in horses supplemented daily for three months. In a secondary part of the study, the anti-oxidant capacity of the present treatment was also tested. Sixteen horses were randomly allocated to two groups and supplemented with either 25 g rosehip powder daily (equal to 125 mg natural vitamin C), or with 50 gram rosehip powder daily (equal to 250 mg vitamin C). Serum vitamin C was analysed both prior to supplementation and then again 14, 28 and 84 days following supplementation. Anti-oxidative capacity was assessed as the release of oxidative anions from polymorph-nucleated leucocytes prior to supplementation and after 14 and 84 days, respectively. Whilst there was a trend towards an increase in serum vitamin C concentration following 84 days of supplementation with 125 mg of natural vitamin C, this was not statistically significant. However, a significant increase in serum vitamin C concentration was observed following 14 days of supplementation with 250 mg vitamin C (P<0.02). The magnitude of this increase was greater following 28 and 84 days of supplementation (P<0.02 and P<0.02), respectively. Additionally, serum vitamin C concentration was significantly higher following supplementation with 250 versus 125 mg of vitamin C daily (P<0.03). The higher dose of natural vitamin C also resulted in a significant reduction in the release of oxidative anions (P<0.001). These results suggest that natural vitamin C from rosehip is absorbed sufficiently to raise serum vitamin C concentration and to reduce the liberation of oxidative anions in horses supplemented with less than 500 mg daily.

Acute necrotizing myopathy in a dog

A 9 yr old spayed female cocker spaniel presented for an acute onset of weakness. Rhabdomyolysis and myoglobinuria were found 36 hr after presentation. The dog was managed for several electrolyte and mineral abnormalities and rhabdomyolysis-induced acute renal failure. The diagnosis of idiopathic necrotizing myopathy was determined by histopathology and by the exclusion of underlying infectious agents and metabolic defects. The dog recovered completely from the acute crisis and acute renal failure.

Nutritional muscular dystrophy in a four-day-old Connemara foal

This report describes a four-day-old, full-term Connemara colt, presented for the evaluation of a progressive inability to rise unassisted. A diagnosis of nutritional muscular dystrophy was made based on muscular weakness, elevated muscle enzymes and low vitamin E, selenium and glutathione peroxidase activity. The foal was treated with intramuscular vitamin E-selenium and made a full recovery.

Equine metabolic myopathies with emphasis on the diagnostic approach comparison with human myopathies A review

This review gives an overview of the presently known human and equine metabolic myopathies with emphasis on the diagnostic approach. Metabolic myopathies are muscle disorders caused by a biochemical defect of the skeletal muscle energy system, which results in inefficient muscle performance. Myopathies can arise in different levels of the metabolic system. In this review the metabolic myopathies are categorized in disorders of the carbohydrate metabolism, lipid metabolism, mitochondrial myopathies (other than those described in lipid metabolism), disorders of purine metabolism, primary disorders involving ion channels and electrolyte flux and secondary or acquired metabolic myopathies.

Relationship between markers of blood oxidant status and physiological variables in healthy and heaves-affected horses after exercise

Exercise-induced oxidative stress is investigated as a potential performance-limiting factor in human sports medicine. Therefore, the present study aimed to assess whether physiological variables that change with exercise intensity were correlated with blood oxidant markers in healthy and heaves-affected horses. Seven healthy horses, 8 heaves-affected in remission and 7 heaves-affected in crisis performed a standardised exercise test (SET) of stepwise increasing intensity. Variables monitored during exercise were heart rate (HR), venous plasma lactate (LA), packed cell volume (PCV) and arterial oxygen tension (PaO2). Oxidant markers (uric acid [UA], 8-iso-PGF2alpha and reduced [GSH] and oxidised glutathione [GSSG]) were analysed in venous peripheral blood sampled at rest (R), at peak-exercise intensity (Emax), 15 (E15) and 60 (E60) min after SET. There was a significant effect of heaves on oxidant markers and, therefore, correlation analyses between physiological variables and oxidant markers were performed separately per horse group. In healthy horses, UA analysed at Emax was positively correlated with LA. Furthermore, GSH analysed at Emax and E15 was positively correlated with PaO2. In healthy and heaves-affected horses in remission, GSH and GSSG determined at Emax were negatively correlated with HR. There was no significant correlation between 8-iso-PGF2alpha and physiological variables. In conclusion, a correlation between the physiological response to exercise and some oxidant markers exists in healthy horses. However, in heaves-affected horses the blood oxidant status is probably more dependant on airway disease than on exercise. Future studies should be undertaken to assess whether antioxidant supplementation might positively influence the oxidant-antiodidant balance in exercising horses.