Incidence, Severity and Prognosis Associated with Hyponatremia in Dogs and Cats

International Renal Interest Society best practice consensus guidelines for the diagnosis and management of acute kidney injury in cats and dogs

Acute kidney injury (AKI) is defined as an injury to the renal parenchyma, with or without a decrease in kidney function, as reflected by accumulation of uremic toxins or altered urine production (i.e., increased or decreased). AKI might result from any of several factors, including ischemia, inflammation, nephrotoxins, and infectious diseases. AKI can be community- or hospital-acquired. The latter was not previously considered a common cause for AKI in animals; however, recent evidence suggests that the prevalence of hospital-acquired AKI is increasing in veterinary medicine. This is likely due to a combination of increased recognition and awareness of AKI, as well as increased treatment intensity (e.g., ventilation and prolonged hospitalization) in some veterinary patients and increased management of geriatric veterinary patients with multiple comorbidities. Advancements in the management of AKI, including the increased availability of renal replacement therapies, have been made; however, the overall mortality of animals with AKI remains high. Despite the high prevalence of AKI and the high mortality rate, the body of evidence regarding the diagnosis and the management of AKI in veterinary medicine is very limited. Consequently, the International Renal Interest Society (IRIS) constructed a working group to provide guidelines for animals with AKI. Recommendations are based on the available literature and the clinical experience of the members of the working group and reflect consensus of opinion. Fifty statements were generated and were voted on in all aspects of AKI and explanatory text can be found either before or after each statement.

Suspected cerebral salt wasting syndrome secondary to traumatic brain injury in a dog

OBJECTIVE

To describe a dog with suspected cerebral salt wasting syndrome (CSWS) secondary to traumatic brain injury (TBI).

CASE SUMMARY

A 2-month-old intact male Chihuahua-American Pitbull Terrier mix weighing 1.94 kg presented to a veterinary teaching emergency room after suffering bite wound-penetrating trauma to the head. Treatment was initiated with hyperosmotic agents, fluid resuscitation, and analgesia. The dog's neurologic dysfunction warranted hospitalization and continuous monitoring. Within 24 hours, the dog developed hyponatremia (133 mmol/L compared to 143 mmol/L on presentation [reference interval 142-149 mmol/L]). As the dog had concurrent tachycardia, increase in urine sodium concentration, polyuria, and weight loss, a diagnosis of cerebral salt wasting was suspected. A 2% hypertonic saline constant rate infusion was administered for volume replacement, and the patient showed improvement in clinical signs and blood sodium concentration. The dog was discharged on Day 5. Recheck examination showed significant neurologic improvement with sodium just below the low end of the reference range (141 mmol/L [reference interval 142-149 mmol/L]).

NEW OR UNIQUE INFORMATION PROVIDED

This is the first description of suspected CSWS in veterinary medicine. Hyponatremia is a common finding in critically ill neurologic people, including those with TBI, and is typically associated with either syndrome of inappropriate antidiuretic hormone or CSWS. As treatment recommendations for syndrome of inappropriate antidiuretic hormone and CSWS are diametrically opposed, identifying the presence of hyponatremia and distinguishing between these 2 clinical entities is critical for improving patient care for those with TBI. This case highlights the characteristics and clinical progression regarding the diagnosis and management of suspected CSWS.

Syndrome of inappropriate antidiuretic hormone secretion secondary to trauma in a dog

OBJECTIVE

To describe a case of inappropriate antidiuretic hormone (ADH) secretion in a dog secondary to trauma.

CASE SUMMARY

A 14-year-old neutered female mixed breed dog presented for evaluation of bite wounds. The dog sustained multiple puncture wounds to the cervical area, stifle, and elbow. Treatment was initiated with isotonic crystalloid fluids, analgesia, broad-spectrum antimicrobials, and gastroprotectants. The dog developed hyponatremia with concurrent serum hypoosmolality and inappropriate urine hyperosmolality and urine sodium secretion, leading to a diagnosis of the syndrome of inappropriate ADH secretion. The hyponatremia improved, and the dog improved clinically and was discharged 3 days after admission.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first case description of the syndrome of inappropriate ADH secretion in a dog suffering from trauma. Inappropriate ADH secretion is largely under-recognized in veterinary patients. Increased awareness of this syndrome can lead to initiation of appropriate treatment and improved outcomes.

Novel Diagnostic Tools for Identifying Cognitive Impairment in Dogs: Behavior, Biomarkers, and Pathology

Canine cognitive dysfunction syndrome (CCDS) is a progressive neurodegenerative disorder in senior dogs that is mainly associated with decreased ability to learn and respond to stimuli. It is commonly under-diagnosed because behavioral changes are often attributed to the natural process of aging. In the present study, we used for the first time a comprehensive approach enabling early diagnosis of canine patients with mild cognitive disorders (MiCI). We included CAnine DEmentia Scale (CADES) questionnaires, biochemical parameters, and biomarkers in blood serum, and correlated them with post-mortem histopathological changes. The CADES questionnaires enabled us to identify MiCI dogs developing changes mainly in domains corresponding to social interaction and spatial orientation, which seems to be crucial for delineating early cognitive disorders. Biochemical analyses in these dogs showed slightly elevated liver enzyme parameters (AST and ALT) and significantly decreased sodium and chloride levels in blood serum. Furthermore, we describe for the first time a significant increase of neurofilament light chain (NFL) in blood serum of MiCI dogs, compared to normal aging seniors and young controls, but no changes in TAU protein and amyloid-β (Aβ42) peptide levels. In canine brains with cognitive impairment, amyloid plaques of mainly diffuse and dense types were detected. Furthermore, activated microglia with amoeboid body and dystrophic processes occurred, in some cases with spheroidal and bulbous swellings. On the other hand, no TAU pathology or neurofibrillary tangles were detected. These results suggest that a combination of CADES questionnaire mainly with CNS injury biomarker (NFL) and with biochemical parameters (ALT, AST, Na, and Cl) in blood serum may predict CCDS in senior dogs.

Mineral Composition of Cereal and Cereal-Free Dry Dog Foods versus Nutritional Guidelines

The aims of the present work are to estimate the nutritional value and to evaluate and compare the levels of macroelements (Ca, P, K, Na, Mg), microelements (Fe, Zn, Mn, Cu), heavy metals (Co, Cd, Pb, Mo, Cr, Ni), and their ratios in extruded complete foods for adult dogs, their compatibility with nutritional guidelines, as well as food profile similarity. Basic composition was determined according to Association of Official Analytical Chemists (AOAC). Analyses for elements were performed using an atomic absorption spectrometer. All the evaluated dry dog foods met the minimum recommended levels for protein and fat. Eighteen tested dog foods (60%) did not meet at least one recommendation of nutritional guidelines. Four dog foods exceeded the legal limit of Fe and five foods exceeded the legal limit of Zn; in one of them, Zn level was almost twice higher. Dog foods with insect protein exceeded the legal limit for Mn content. Eight dog foods had an inappropriate Ca:P ratio. Heavy metals were below detection limit in all analyzed dog foods. The results seem to show the need for regular feed analyses of the elemental composition in raw materials before introducing supplementation and for the monitoring of the mineral composition of finished pet food.

Incidence and risk factors for neurological signs after attenuation of a single congenital portosystemic shunt in 50 cats

OBJECTIVE

To determine the incidence, outcome, and risk factors for postattenuation neurological signs (PANS) in cats treated for single congenital portosystemic shunts (CPSS).

STUDY DESIGN

Retrospective cohort study.

ANIMALS

Cats (n = 50) with a single CPSS.

METHODS

Medical records of cats treated by surgical attenuation of a single CPSS between 2003 and 2017 were reviewed for signalment, surgical technique, preoperative management and postoperative clinical outcomes. Binary logistic regression was performed to investigate risk factors for occurrence of PANS and seizures.

RESULTS

Congenital portosystemic shunts in 50 cats included 40 extrahepatic and 10 intrahepatic shunts. Postattenuation neurological signs were recorded in 31 (62%) cats and graded as 1 in 10 cats, 2 in nine cats, and 3 in 12 cats. Postattenuation neurological signs included seizures in 11 cats. Five of 31 cats with PANS did not survive to discharge. No association was detected between PANS or seizures and the type of CPSS (intrahepatic or extrahepatic), degree of attenuation, age, or the use of perioperative levetiracetam or hepatic encephalopathy immediately preoperatively. Osmolality at a median 24 hours postoperatively was lower in cats with PANS (P < .049, Wald 3.867, odds ratio [Exp(B)] 0.855, CI 0.732-0.999).

CONCLUSION

Postattenuation neurological signs are common complications in cats treated for CPSS. Preoperative levetiracetam did not prevent the occurrence of PANS or seizures. The only risk factor for PANS detected was lower postoperative Osmolality in cats with PANS at 24 hours.

CLINICAL SIGNIFICANCE

Postattenuation neurological signs including seizures occur frequently in cats undergoing surgical attenuation of a CPSS. Preoperative levetiracetam did not protect against the development of PANS.

Multi-Level Safety Studies of Anti Fel d 1 IgY Ingredient in Cat Food

Chickens exposed to antigens produce IgY antibodies, similar in structure to mammalian IgG. Hens exposed with an allergen produced by cats (Fel d 1) results in production of anti-Fel d 1 specific IgY (AFD1), which is naturally concentrated in egg yolk. A chicken egg product ingredient containing AFD1 was evaluated for safety in a 26-week randomized, controlled, blinded tolerance study in cats and in vitro for mutagenic and genotoxic effects. The in vivo study was conducted with groups fed kibble containing 0, 7, 39, or 66 ppm AFD1. Parameters examined included: clinical observations, body weights, food consumption, serum chemistry, hematology, blood coagulation, urinalyses, and mortality and morbidity checks. AFD1 was evaluated for potential mutagenic effects utilizing the bacterial reverse mutation assay at concentrations of up to 2.78 ppm and for potential structural chromosomal aberrations at up to 3 ppm using human peripheral blood lymphocytes (HPBL). After 6-months of feeding to cats, there were no significant differences between control and any test groups in any parameters analyzed. No significant increases in mutations or chromosomal aberrations were observed in tests with or without metabolic activation (S9). These studies show AFD1 was well-tolerated in cats at levels tested and does not induce mutagenic or chromosomal aberrations under study conditions.

Of Mice and Men-The Physiology, Psychology, and Pathology of Overhydration

The detrimental effects of dehydration, to both mental and physical health, are well-described. The potential adverse consequences of overhydration, however, are less understood. The difficulty for most humans to routinely ingest ≥2 liters (L)-or "eight glasses"-of water per day highlights the likely presence of an inhibitory neural circuit which limits the deleterious consequences of overdrinking in mammals but can be consciously overridden in humans. This review summarizes the existing data obtained from both animal (mostly rodent) and human studies regarding the physiology, psychology, and pathology of overhydration. The physiology section will highlight the molecular strength and significance of aquaporin-2 (AQP2) water channel downregulation, in response to chronic anti-diuretic hormone suppression. Absence of the anti-diuretic hormone, arginine vasopressin (AVP), facilitates copious free water urinary excretion (polyuria) in equal volumes to polydipsia to maintain plasma tonicity within normal physiological limits. The psychology section will highlight reasons why humans and rodents may volitionally overdrink, likely in response to anxiety or social isolation whereas polydipsia triggers mesolimbic reward pathways. Lastly, the potential acute (water intoxication) and chronic (urinary bladder distension, ureter dilation and hydronephrosis) pathologies associated with overhydration will be examined largely from the perspective of human case reports and early animal trials.

Hypernatremia and Coagulopathy May or May Not Be Useful Clinical Biomarkers in Dogs with Head Trauma: A Retrospective Study

This study was performed to evaluate clinical biomarkers as prognostic values in dogs with traumatic brain injury (TBI) based on findings in human patients. Sodium levels of 158 dogs with TBI and 169 patients with trauma without involvement of the head except head trauma (EHT) were examined. TBI patients with hypernatremia had a slightly higher risk of dying (22.03 %) than dogs with normal sodium levels (19.76%). However, there was no significant correlation between sodium levels and outcome in TBI patients (p = 0.6357). Dogs with sodium levels >160 mmol/L were non-survivors. In dogs with late-onset post-traumatic epilepsy (PTE) more often hyponatremia was measured, and in dogs with immediate PTE mild hypernatremia or normal sodium levels were measured after the trauma. Evaluation of coagulation parameters in a subpopulation of dogs showed a strong correlation between partial thromboplastin time/prothrombin time (PTT/PT) and the Modified Glasgow Coma Scale (MGCS) (p = 0.0006; p = 0.0306). In conclusion, unlike in human patients, sodium levels displayed no significant correlation with survival in dogs with TBI in the current study. However, in cases with severe TBI, dog owners often elect euthanasia before severe hypernatremia can be measured. Late PTE was observed in cases with initial hyponatremia. Because of a significant correlation between PTT/PT and MGCS, coagulopathy might be considered as a prognostic clinical biomarker in canine TBI patients.

Desmopressin acetate-induced water intoxication in a dog with psychogenic polydipsia

A 21-month-old male Border Collie presented to emergency service after a generalised tonic–clonic seizure. He received desmopressin acetate (1-Desamino-8-D-Arginin-Vasopressin, DDAVP) intraconjunctivally and intranasally for treatment of suspected central diabetes insipidus (DI) for a year, but water intake had recently increased again to 120–150 ml/kg/day. History, physical examination and clinicopathological findings, especially marked hyponatraemia, were consistent with water intoxication. The condition was stabilised by discontinuation of DDAVP and fluid restriction. Hyponatraemia resolved with frequent adjustments of fluid management according to physical parameters and electrolyte status. After exclusion of other causes for polyuria and polydipsia (PD), a modified water deprivation test led to diagnosis of psychogenic PD. Long-term outcome was excellent with water restriction and intensified dog training.

Desoxycorticosterone Pivalate Duration of Action and Individualized Dosing Intervals in Dogs with Primary Hypoadrenocorticism

Background

Clinicians alter dosing for desoxycorticosterone pivalate (DOCP) to mitigate costs, but this practice has not been critically evaluated in a prospective clinical trial.

Hypothesis/Objectives

The duration of action of DOCP is longer than 30 days in dogs with primary hypoadrenocorticism (PH).

Animals

A total of 53 client‐owned dogs with PH. Twenty‐four dogs with newly diagnosed PH (Group 1) and 29 dogs with treated PH (Group 2).

Methods

Prospective, multicenter, clinical trial. For phase I, DOCP was administered and plasma sodium and potassium concentrations were measured until the dog developed hyponatremia or hyperkalemia at a planned evaluation, or displayed clinical signs with plasma electrolyte concentrations outside of the reference interval independent of a planned evaluation, thus defining DOCP duration of action. Plasma electrolyte concentrations then were assessed at the end of the individualized dosing interval (IDI; i.e., DOCP duration of action minus 7 days, phase II and at least 3 months after concluding phase II, phase III).

Results

The duration of action of DOCP in dogs in phase I with naïve PH (n = 24) ranged from 32 to 94 days (median, 62 days; 95% confidence interval [CI], 57, 65) and previously treated PH (n = 29) from 41 to 124 days (median, 67 days; CI, 56, 72). Overall, the final DOCP dosing interval for all dogs that completed phase II (n = 36) ranged from 38 days to 90 days (median, 58 days; CI, 53, 61). No dog that completed phase III (n = 15) required reduction in the IDI. The DOCP duration of action, independent of group, was not significantly associated with several baseline variables. The median drug cost reduction using IDI was approximately 57.5% per year.

Conclusion and Clinical Importance

The duration of action of DOCP in dogs with PH is >30 days, and plasma sodium and potassium concentrations can be maintained with an IDI >30 days long term.

A Quick Reference on Hyponatremia

The article focuses on causes of hyponatremia, including hypovolemia, diabetes mellitus and others. Hypovolemia is a major cause of hyponatremia in veterinary medicine. Hypovolemia causes a decrease in effective circulating volume, triggering antidiuretic hormone (ADH) secretion and free water retention, and develops after gastrointestinal losses, renal losses, hemorrhagic shock, hypoadrenocorticism, and other causes of hypovolemia. The article reviews the clinical approach to diagnosing the cause of hyponatremia in critically ill patients, including recognition of the syndrome of inappropriate ADH secretion (SIADH).