Acute Kidney Injury and Renal Failure in Horses

Clinical Examination of the Muscle System

The equine muscle system is complex and prone to a large range of hereditary and acquired diseases that often have overlapping clinical signs with orthopedic, neurologic, and other disorders. Obtaining a clinical history that fully outlines the client concerns and any known information about the disorder and following with a comprehensive physical examination and screening clinical pathology tests are fundamental to achieve definitive diagnosis. A methodical and comprehensive approach aids accurate diagnosis and development of an optimal treatment and management plan. This article describes the clinical examination approach and clinical pathology relevant to evaluating muscle disease in horses.

Effect of furosemide on comprehensive renin-angiotensin-aldosterone system activity of Thoroughbred horses

BACKGROUND

Furosemide, a commonly used diuretic, activates the renin-angiotensin-aldosterone system (RAAS) in other species. Little is known about RAAS peptide activation in horses.

HYPOTHESIS/OBJECTIVES

To evaluate equilibrium analysis as a practical method for RAAS quantification in horses and describe the RAAS response to a single dose of furosemide. We hypothesize that furosemide would cause transient increase in RAAS peptides in horses.

ANIMALS

14 healthy adult thoroughbreds from a university teaching herd.

METHODS

Horses received either furosemide (1 mg/kg IV) or saline IV in a crossover study design. Protease-inhibited samples were compared with equilibrium analysis samples with Deming regression analysis. Renin-angiotensin-aldosterone system hormones were evaluated at 0, 0.25, 0.5, 4, and 24 hours postadministration, via equilibrium analysis. Values were compared with a mixed effects model.

RESULTS

Correlation between protease inhibition and equilibrium analysis was high for angiotensin I peptide (AngI) and angiotensin II peptide (AngII) (r = .92 and .95, respectively). Baseline RAAS peptide concentrations were below the limit of detection except AngII (median, 7.5 [range, 3.5-14.0] pmol/L). Furosemide administration resulted in an increase in AngI (8.0 [0.5-15.5] pmol/L, P = .03), AngII (33.7 [9.6-57.9] pmol/L, P = .0008), angiotensin III peptide (AngIII) (2.9 [0.9-4.9] pmol/L, P = .0005), angiotensin IV peptide (AngIV) (2.0 [0.6-3.4] pmol/L, P = .0005), and angiotensin 1-5 peptide (Ang1-5) (5.6 [1.2-5.9] pmol/L, P = .003) at 4 hours. Differences are reported as difference in the mean (95% confidence interval [CI]).

CONCLUSIONS AND CLINICAL IMPORTANCE

Furosemide produced an increase in hormones associated with both the classical and alternative RAAS pathways. Serum equilibrium analysis is practical for RAAS analysis in horses.

Successful hemodialysis treatment of a Quarter Horse mare with silver maple leaf toxicity and acute kidney injury

An adult American Quarter Horse mare presented for pigmenturia and lethargy of 12 hours' duration and was diagnosed with silver maple leaf toxicity. The mare had intravascular hemolysis and azotemia. The mare was treated with a transfusion of whole blood, fluids administered IV, antibiotics, oxygen insufflation, and supportive care. The azotemia persisted despite conventional medical management and hemodialysis was elected. After 2 intermittent hemodialysis treatments over 3 days, the azotemia almost resolved, clinical signs improved, and the mare was discharged. The blood urea nitrogen, creatinine, and electrolyte concentrations remained normal 6 months later after examination by the referring veterinarian. Hemodialysis treatment can be feasible in horses if equipment and expertise are available and should be considered as a treatment option if indicated.

Survival of formalin intoxication in a 13-year-old Thoroughbred gelding

BACKGROUND

Formalin intoxication via the gastrointestinal route has not been previously reported in the horse. Whereas ingestion of formalin in humans, although rare, is well documented. Majority of human cases are either accidental, suicidal or homicidal and often lead to fatality, with a reported lethal formaldehyde dose equating to 0.12 - 0.16 g/kg bwt.

OBJECTIVES

To describe a single case report of the clinical management of an adult horse referred to a veterinary teaching hospital following accidental administration of 10% formalin via nasogastric tube.

METHODS

A 13-year-old Thoroughbred gelding originally presented to the referring veterinarian for colic where 1.8 L of 10% formalin was accidentally administered instead of mineral oil via nasogastric intubation, a potentially lethal dose of formaldehyde (0.12 g/kg bwt). Approximately 20-hours following 10% formalin administration the horse was admitted to the referral hospital with moderate tachycardia, occasional ectopic beats, tacky and hyperaemic mucous membranes, delayed capillary refill time, reduced borborygmi, and pronounced digital pulses. Diagnostic investigations included laboratory blood analysis, urinalysis, electrocardiogram, abdominal ultrasound, palpation per rectum and gastroscopy.

RESULTS

Patient assessment found evidence of toxicity to the gastrointestinal tract, hypovolaemia and risk for laminitis. Intensive care included fluid and electrolyte therapy, anti-inflammatories and analgesia, continuous digital cryotherapy, gastro-protectants and other methods of gastrointestinal support. The horse was discharged from hospital on day 14 with no long-term complications and the client-veterinarian relationship was preserved.

DISCUSSION

In human cases of ingestion, gastrointestinal injury is typically accompanied by severe metabolic acidosis and multiple organ dysfunction syndrome due to toxicity of other body systems that can contribute to non-survival. Formaldehyde toxicity in the present case predominantly affected the gastrointestinal tract, most likely a direct result of the route of administration. Aside from gastrointestinal injury, primary toxicity of other body systems was not confirmed. To prevent this medical error recurring, the referring veterinary clinic revised their labelling and storage of 10% formalin.

CONCLUSION

This is the first report of systemic formalin intoxication in the horse. Following a high dose of 10% formalin (0.12 g/kg bwt formaldehyde) enterally, the horse survived having received intensive supportive care based on human guidelines for ingested formalin.

Longitudinal assessment of adrenocortical steroid and steroid precursor response to illness in hospitalized foals

Sepsis is a major cause of morbidity and mortality in neonatal foals. Relative adrenal insufficiency (RAI), defined as an inadequate cortisol response to stress, has been associated with sepsis, prematurity, and poor outcome in newborn foals. In addition to cortisol, the adrenal gland synthesizes several biologically important steroids and steroid precursors, including aldosterone, androgens, and progestogens. However, concentration of these hormones during hospitalization and their association with the severity of disease and mortality in critically ill foals have not been completely evaluated. We hypothesized, that in addition to cortisol and aldosterone, concentration of steroid precursors (progestogens and androgens) will be altered in critically ill foals. We also proposed that septic foals will have higher concentrations of steroid precursors than healthy foals, and steroid concentrations will be persistently increased during hospitalization in non-surviving septic and premature foals. Foals <4 days of age were categorized as healthy, septic, sick non-septic, and premature based on physical exam, medical history, and laboratory data. Blood samples were collected on admission (0 h), 24 h, and 72 h after admission. Concentrations of steroids and ACTH were measured by immunoassays. The area under the curve over 72 h (AUC0-72h) of hospitalization was calculated for each hormone. Serum cortisol, aldosterone, progesterone, pregnenolone, dehydroepiandrosterone sulfate (DHEAS), and 17 α-hydroxyprogesterone concentrations were higher in septic and premature foals compared to healthy foals at 0 h and throughout 72 h of hospitalization (P < 0.05). Plasma ACTH concentrations were higher in septic and premature foals on admission compared to healthy controls (P < 0.05). The progesterone (AUC0-72h) cut-off value above which non-survival could be reliably predicted in hospitalized foals was 1,085 ng/mL/h, with 82% sensitivity and 77% specificity. Critically ill neonatal foals had an appropriate response to stress characterized by increased concentrations of cortisol and steroid precursors on admission. A rapid decline in steroid concentration was observed in healthy foals. However, persistently elevated progestogen and androgen concentrations were associated with a lack of improvement in the course of disease and poor outcome.