K.G. Magdesian

Blood Glucose Concentrations in Critically Ill Neonatal Foals

REASONS FOR PERFORMING STUDY Critical illness is associated with hyperglycemia in humans, and a greater degree and duration of hyperglycemia is associated with nonsurvival. Hypoglycemia is also seen in critically ill humans, and is associated with nonsurvival. This might also be true in the critically ill foal. OBJECTIVES To investigate the association of blood glucose concentrations with survival, sepsis, and the systemic inflammatory response syndrome (SIRS). METHODS Blood glucose concentrations at admission (515 foals) and 24 hours (159 foals), 36 hours (95), 48 hours (82), and 60 hours (45) after admission were analyzed. Logistic regression analyses were performed to investigate the association of glucose concentrations with survival, sepsis, a positive blood culture, or SIRS. RESULTS 29.1% of foals had blood glucose concentrations within the reference range (76-131 mg/dL) at admission, 36.5% were hyperglycemic, and 34.4% were hypoglycaemic. Foals that did not survive to hospital discharge had lower mean blood glucose concentrations at admission, as well as higher maximum and lower minimum blood glucose concentrations in the 1st 24 hours of hospitalization, and higher blood glucose at 24 and 36 hours. Foals with blood glucose concentrations <2.8 mmol/L (50 mg/dL) or >10 mmol/L (180 mg/dL) at admission were less likely to survive. Hypoglycemia at admission was associated with sepsis, a positive blood culture, and SIRS. CONCLUSIONS AND POTENTIAL RELEVANCE Derangements of blood glucose concentration are common in critically ill foals. Controlling blood glucose concentrations may therefore be beneficial in the critically ill neonatal foal, and this warrants further investigation.

Bacteraemia in neonatal foals: clinicopathological differences between Gram-positive and Gram-negative infections, and single organism and mixed infections

REASONS FOR PERFORMING STUDY Treatment for bacteraemia in foals must be started before the identity of the causative organism is known. Information aiding selection of effective antimicrobials should improve outcome. OBJECTIVES To describe differences in clinical and clinicopathological data and outcome in foals with bacteraemia due to different classes of bacteria. METHODS Records of foals with a positive blood culture, age < 10 days and presenting to a university hospital 1995-2004, were reviewed. Bacterial culture results, subject details, historical information, physical examination findings at admission and clinicopathological data generated during the first 48 h of hospitalisation were analysed. Results from foals with Gram-positive or Gram-negative organisms, single or mixed organism bacteraemias, and with bacteraemia due to 3 commonly isolated organisms were compared. RESULTS Eighty-five foals met the inclusion criteria. Gram-negative organisms (n = 59) Gram-positive organisms (n = 13) or multiple organisms (n = 19) were cultured from individual foals. Foals with Gram-negative bacteraemia had lower total white blood cell and lymphocyte counts at admission than did those from which only Gram-positive bacteria were cultured. Mixed organism bacteraemia was associated with tachycardia, increased serum concentrations of sodium, chloride and urea nitrogen, acidosis, respiratory distress, recumbency on admission and nonsurvival. Actinobacillus spp. infections were associated with leucopenia, neutropenia, lymphopenia and depression on hospital admission. CONCLUSIONS AND POTENTIAL RELEVANCE Recognising particular patterns of clinical and clinicopathological findings associated with infection with specific groups of bacteria may, in the future, aid antimicrobial selection and influence prognosis in bacteraemic foals.

Malignant hyperthermia associated with ryanodine receptor 1 (C7360G) mutation in Quarter Horses.

BACKGROUND Anesthetic-induced malignant hyperthermia (MH) has been documented in Quarter Horses with a single point mutation in the ryanodine receptor 1 gene (RyR1) at nucleotide C7360G, generating a R2454G amino acid substitution. However, there have been no reports of nonanesthetic manifestations of MH in horses with the C7360G mutation. OBJECTIVE To describe clinical manifestations of Quarter Horses with the C7360G mutation. ANIMALS Eleven Quarter Horses with the RyR1 C7360G mutation. METHODS This prospective study included horses with suspected MH, undetermined etiology of sudden death, death within hours of onset of rhabdomyolysis, muscle rigidity, stiffness, intermittent sweating, and persistent increases in serum muscle enzyme activities. Whole blood in EDTA and skeletal muscle were processed for genetic and histochemical analysis. Medical records and pedigrees were collected when available. RESULTS Both anesthetic- and non-anesthetic-associated myopathic manifestations of MH occurred in halter Quarter Horses with mutation of RyR1. The disease is inherited as an autosomal dominant trait. Clinical and laboratory abnormalities were similar in both forms. Rhabdomyolysis was a common finding in both groups of horses. Skeletal muscle histochemical findings were nonspecific and compatible with a noninflammatory myopathic process. CONCLUSIONS AND CLINICAL IMPORTANCE MH is a potentially fatal disease of Quarter Horses that could be triggered by halogenated anesthetics and other nonanesthetic factors that may include exercise, stress, breeding, illnesses, and concurrent myopathies.

A Comparison of Hypertonic (7.2%) and Isotonic (0.9%) Saline for Fluid Resuscitation in Horses: A Randomized, Double-blinded, Clinical Trial

BACKGROUND Hypertonic saline solution (7.2%) (HSS) can quickly replace intravascular volume deficits. HSS more recently has been advocated in the treatment of traumatic brain injury, but its use in dehydrated patients remains controversial. HYPOTHESIS Hypertonic saline solution will show a significant improvement in both clinical and laboratory hydration parameters as compared to isotonic (0.9%) saline solution (ISS). ANIMALS Endurance horses eliminated from the 2009 Western States 100-mile (220-km) endurance ride and requiring IV fluid therapy were eligible for enrollment in the study. METHODS Twenty-two horses were randomly assigned to receive 4 mL/kg of either HSS or ISS along with 5 L lactated Ringers solution (LRS). After this bolus, horses were treated with additional LRS in varying amounts. Blood and urine samples were collected before, during, and after treatment. Data were compared using 2-way ANOVA with repeated measures. RESULTS As compared to ISS, HSS horses showed greater decreases in PCV (P = .04), total protein (P = .01), albumin (P = .01), and globulin (P = .02) concentrations. HSS horses showed greater increases in sodium and chloride (P < .001) as compared to ISS horses. Horses receiving HSS had a shorter time to urination (P = .03) and lower specific gravity (P < .001) than those receiving ISS. CONCLUSIONS Results of this study indicate that HSS may provide faster restoration of intravascular volume deficits than ISS in endurance horses receiving emergency medical treatment. More marked electrolyte changes should be expected with HSS, however, and additional fluids after HSS administration likely are needed.

Suspected protozoal myeloencephalitis in a two-month-old colt

A two-month-old Appaloosa colt developed neurological signs shortly after birth involving deficits affecting cranial nerves IV, VIl, Vil, IX, X and XII, and possibly nerve VI. The most likely differential diagnoses were congenital anomalies, meningoencephalitides, trauma or nutritional causes. The foal was investigated by the analysis of cerebrospinal fluid (CSF), electromyelography (EMG), brain auditory evoked responses, magnetic resonance imaging (MRI), peripheral nerve biopsy, and Western blot analysis for the presence of intrathecal antibodies to Sarcocystis neurona, the causative agent of equine protozoal myeloencephalitis. Significantly abnormal EMG findings included spontaneous electrical activity of the tongue, suggesting denervation. The MRI was useful in ruling out masses, congenital anomalies and focal abscessation. The cytology of CSF revealed mild mononuclear reactivity. Western blot testing of CSF was positive, indicating the intrathecal presence of antibodies to S neurona. The foal was treated with pyrimethamine and trimethoprim-sulphadiazine for two months and returned to nearly normal neurologic status.

Serial Measurement of Lactate Concentration in Horses with Acute Colitis

BACKGROUND Serial measurement of lactate concentration is utilized for therapeutic and prognostic purposes in human critical care. The prognostic value of serial lactate measurement in equine acute colitis warrants investigation. HYPOTHESIS Serial lactate concentrations are predictive of outcome in horses with colitis. ANIMALS A total of 101 horses with colitis. METHODS Retrospective study. Plasma L-lactate concentrations were measured at admission and at 4-8 and 24 hours after admission. Associations between admission, early (4-8 hours) and late (24 hours) lactate concentrations, and survival status were determined. The percent reduction in lactate concentration between admission and the early time point, and between admission and the late time point, was calculated. Using a cutoff value, associations between percent reduction in lactate and survival status and associations between percent reduction in lactate and clinical and clinicopathologic data were determined. RESULTS There was no association between admission plasma lactate concentration and survival status (P = .26). The 4-8 and 24 hour after admission lactate concentrations were associated with survival status (P = .023, .013, respectively). Lactate cutoffs of ≤2.3 and ≤1.5 mmol/L had the maximum sensitivity and specificity for predicting survival at the 4-8 and 24 hour time points, respectively. When lactate reduction ≥30% at 4-8 hours and ≥50% at 24 hours after admission were used as the cutoffs, the percent reduction of lactate concentration was significantly associated with survival (P = .012 and .019, respectively). CONCLUSION AND CLINICAL IMPORTANCE The prognostic ability of serial measurement of blood lactate concentration warrants prospective study as a measure of therapeutic response in horses with colitis.

Idiopathic granulomatous pneumonia in seven horses.

The history, clinical signs and pathological findings in seven adult horses with histologically confirmed idiopathic granulomatous disease, primarily of the lungs, are reviewed. They ranged in age from eight to 21 years, five were geldings and two were females, they belonged to five breeds and there were no seasonal or geographical associations. The primary clinical signs were chronic weight loss, exercise intolerance and respiratory distress which did not respond to conventional treatment. The most consistent physical findings were depression, anorexia, tachycardia, tachypnoea and adventitious lung sounds. Thoracic radiographs revealed a diffuse, structured, nodular, interstitial pulmonary pattern in each horse. Haematological measurements suggested a chronic inflammatory process and the cytology of transtracheal washes was consistent with a mild suppurative inflammation. Idiopathic granulomatous pneumonia was confirmed histologically in each of the horses, either postmortem or by a lung biopsy. The horses responded poorly to medical treatment and only one of three treated horses is still alive.

Minimum Inhibitory Concentrations of Equine Corynebacterium pseudotuberculosis Isolates (1996–2012)

Background Few studies report the minimum inhibitory concentrations for antimicrobials against equine Corynebacterium pseudotuberculosis isolates. Hypothesis/Objectives To evaluate trends in the in vitro activities of 20 antimicrobials against equine Corynebacterium pseudotuberculosis isolates from 1996 to 2012 and to determine if a relationship exists between the minimum inhibitory concentration (MIC) and location of the abscess. Animals Corynebacterium pseudotuberculosis isolates from 196 horses with naturally occurring disease. Methods Retrospective and cross‐sectional design. Medical records were reviewed to obtain clinical and MIC data. Minimum inhibitory concentrations were determined by the microdilution technique. The MIC results over 3 periods were compared (1996–2001, 2002–2006, 2007–2012). Results The MIC90 values for clinically relevant antimicrobials were as follows: chloramphenicol ≤4 μg/mL, enrofloxacin ≤0.25 μg/mL, gentamicin ≤1 μg/mL, penicillin =0.25 μg/mL, rifampin ≤1 μg/mL, tetracycline ≤2 μg/mL, trimethoprim‐sulfamethoxazole (TMS) ≤0.5 μg/mL, ceftiofur =2 μg/mL, and doxycycline ≤2 μg/mL. There were no significant changes in MIC results over the study period. There was no relationship between MIC patterns and abscess location. Conclusions and Clinical Importance The MIC 50 and MIC 90 values of antimicrobials evaluated in this study for equine isolates of C. pseudotuberculosis did not vary over time. Abscess location was not associated with different MIC patterns in cultured isolates. Several commonly used antimicrobials are active in vitro against C. pseudotuberculosis in vitro.

Repetitive Stimulation of the Common Peroneal Nerve as a Diagnostic Aid for Botulism in Foals

BACKGROUND Botulism is a potentially fatal paralytic disorder for which definitive diagnosis is difficult. OBJECTIVES To determine if repetitive stimulation of the common peroneal nerve will aid in the diagnosis of botulism in foals. ANIMALS Four control and 3 affected foals. METHODS Validation of the test in healthy foals for its comparison in foals with suspected botulism. Controls were anesthetized and affected foals were sedated to avoid risks of anesthesia. The common peroneal nerve was chosen for its superficial location and easy access. Stimulating electrodes were placed along the common peroneal nerve. For recording, the active and reference electrodes were positioned over the midpoint and distal end of the extensor digitorum longus muscle, respectively. Repeated supramaximal stimulation of the nerve was performed utilizing a range of frequencies (1-50 Hz). Data analysis consisted of measuring the amplitude and area under the curve for each M wave and converting these values into percentages of decrement or increment based on the comparison of subsequent potentials to the initial one (baseline) within each set. RESULTS A decremental response was seen at all frequencies in control foals. Decremental responses also were observed in affected foals at low frequencies. An incremental response was seen in all affected foals at 50 Hz. CONCLUSIONS AND CLINICAL IMPORTANCE Decreased baseline M wave amplitudes with incremental responses at high rates are supportive of botulism. Repetitive nerve stimulation is a safe, simple, fast, and noninvasive technique that can aid in the diagnosis of suspected botulism in foals.

Assessment of quantitative polymerase chain reaction for equine herpesvirus-5 in blood, nasal secretions and bronchoalveolar lavage fluid for the laboratory diagnosis of equine multinodular pulmonary fibrosis.

Reasons for performing study: The ante mortem diagnosis of equine multinodular pulmonary fibrosis (EMPF) relies on histopathological results and polymerase chain reaction (PCR)‐positive equine herpesvirus (EHV)‐5 testing of lung tissue. Polymerase chain reaction detection of EHV‐5 in bronchoalveolar lavage fluid (BALF) is commonly used to support a diagnosis of EMPF. However, the diagnostic power of EHV‐5 testing on BALF and other biological samples such as blood and nasal secretions has yet to be shown to support a diagnosis of EMPF. Objectives: To determine the frequency of detection and the viral loads of EHV‐5 by quantitative PCR (qPCR) in blood, nasal secretions and BALF from horses confirmed with EMPF, healthy horses and horses with non‐EMPF pulmonary diseases. Study design: Prospective study. Methods: The study population consisted of 70 adult horses divided into 4 groups based on a combination of clinical findings, cytology of BALF, imaging studies of the thoracic cavity and histopathology of pulmonary tissue: control group (n = 14), EMPF group (n = 11); inflammatory airway disease group (n = 32); and non‐EMPF interstitial lung disease group (n = 13). For each horse, whole blood, nasal secretions and BALF were available for EHV‐5 qPCR testing. Sensitivities, specificities and their respective 95% confidence intervals were calculated for viral loads from blood, nasal secretions and BALF. In addition, these measures were calculated for combined use of blood and nasal secretions. Results: The detection of EHV‐5 in BALF was strongly associated with EMPF (sensitivity 91%, specificity 98.3%). Detection of EHV‐5 in blood was, independent of the viral loads, strongly associated with EMPF with a sensitivity of 91% and specificity of 83.1%. The detection of EHV‐5 in nasal secretions displayed the highest sensitivity (72.7%) and specificity (83.1%) at a level of >245,890 glycoprotein B target genes/million cells to support a diagnosis of EMPF. Dually positive blood and nasal secretions at any viral loads in support of EMPF yielded a sensitivity and specificity of 90% and 89.8%, respectively. Conclusions: Although histopathological confirmation (lung biopsy) is considered the gold standard for EMPF diagnosis, results of qPCR testing of BALF or a combination of whole blood and nasal secretions should be regarded as clinically useful in support of this diagnosis. The latter testing may be relevant when dealing with horses in respiratory distress, for which invasive procedures such as BALF collection or lung biopsies may be detrimental to their health.