Metabolic and Endocrine Profiles in Sick Neonatal Foals Are Related to Survival

ECEIM consensus statement on equine kidney disease

The aim of this consensus statement is to summarize and appraise scientific evidence and combine this with the clinical experience of a panel of experts to optimize recommendations on how to recognize and manage kidney disease in horses.

Energy endocrine physiology, pathophysiology, and nutrition of the foal

Most homeostatic systems in the equine neonate should be functional during the transition from intra- to extrauterine life to ensure survival during this critical period. Endocrine maturation in the equine fetus occurs at different stages, with a majority taking place a few days prior to parturition and continuing after birth. Cortisol and thyroid hormones are good examples of endocrine and tissue interdependency. Cortisol promotes skeletal, respiratory, cardiovascular, thyroid gland, adrenomedullary, and pancreatic differentiation. Thyroid hormones are essential for cardiovascular, respiratory, neurologic, skeletal, adrenal, and pancreatic function. Hormonal imbalances at crucial stages of development or in response to disease can be detrimental to the newborn foal. Other endocrine factors, including growth hormone, glucagon, catecholamines, ghrelin, adipokines (adiponectin, leptin), and incretins, are equally important in energy homeostasis. This review provides information specific to nutrition and endocrine systems involved in energy homeostasis in foals, enhancing our understanding of equine neonatal physiology and pathophysiology and our ability to interpret clinical and laboratory findings, therefore improving therapies and prognosis.

The enteroinsular axis during hospitalization in newborn foals

The enteroinsular axis (EIA) is an energy regulatory system that modulates insulin secretion through the release of enteroendocrine factors (incretins). Despite the importance of energy homeostasis in the equine neonate, information on the EIA in hospitalized foals is lacking. The goals of this study were to measure serum insulin and plasma incretin (glucose-dependent insulinotropic polypeptide [GIP], glucagon-like peptide-1 [GLP-1] and glucagon-like peptide-2 [GLP-2]) concentrations, to determine the insulin and incretin association, as well as their link to disease severity and outcome in hospitalized foals. A total of 102 newborn foals ≤72 h old were classified into hospitalized (n = 88) and healthy groups (n = 14). Hospitalized foals included septic (n = 55) and sick non-septic (SNS; n = 33) foals based on sepsis scores. Blood samples were collected over 72 h to measure serum insulin and plasma GIP, GLP-1 and GLP-2 concentrations using immunoassays. Data were analyzed by nonparametric methods and univariate logistic regression. At admission, serum glucose and insulin and plasma GIP were significantly lower in hospitalized and septic compared to healthy foals (P < 0.01), while plasma GLP-1 and GLP-2 concentrations were higher in hospitalized and septic foals than healthy and SNS foals, and decreased over time in septic foals (P < 0.05). As a percent of admission values, GLP-1 and GLP-2 concentrations dropped faster in healthy compared to hospitalized foals. Serum insulin concentrations were lower in hospitalized and septic non-survivors than survivors at admission (P < 0.01). Hospitalized foals with serum insulin < 5.8 µIU/mL, plasma GLP-1 >68.5 pM, and plasma GLP-2 >9 ng/mL within 24 h of admission were more likely to die (OR = 4.2; 95% CI = 1.1-16.1; OR = 13.5, 95% CI = 1.4-123.7; OR = 12.5, 95% CI = 1.6-97.6, respectively; P < 0.05). Low GIP together with increased GLP-1 and GLP-2 concentrations indicates that different mechanisms may be contributing to reduced insulin secretion in critically ill foals, including impaired intestinal production (GIP, proximal intestine) and pancreatic endocrine resistance to enhanced incretin secretion (GLP-1, GLP-2; distal intestine). These imbalances could contribute to energy dysregulation in the critically ill equine neonate.

Peripheral blood markers of sepsis in foals born from mares with experimentally induced ascending placentitis

BACKGROUND

Neonatal sepsis is a leading cause of neonatal death during the first-week postfoaling. Despite recent advancements in the diagnosis and treatment of sepsis in the newborn foal, the non-specific clinical signs and subtle nature of this disease may result in delayed diagnosis until severe progression of the disease; thus, early detection of sepsis remains critical for a favourable outcome. This study aimed to identify early blood markers as predictive of sepsis on foals.

METHODS

Thirty-five foals were allocated into three groups: healthy control foals (n=7) and foals born from mares with placentitis: septic foals (n=9) and non-septic foals (n=19). Blood samples were obtained immediately after foaling and at 12, 24 and 48 hours. All samples were assessed for glucose, lactate, triglycerides, total cholesterol, urea, creatinine, total solids, fibrinogen, gamma-glutamyl transferase (GGT), serum amyloid A (SAA) and alpha-fetoprotein (AFP) concentrations.

RESULTS

At foaling, glucose and GGT concentrations were lower in septic foals (P<0.001). Of interest, SAA, AFP, creatinine and total cholesterol were higher in septic foals at parturition (P<0.05). At 12 hours, lactate, triglycerides and total cholesterol concentrations were higher in septic foals. When evaluated at 24 and 48 hours, higher concentrations of SAA and AFP were found in placentitis foals than in the control group.

CONCLUSIONS

Total cholesterol and lactate appear to be suitable markers for sepsis during the first 24 hours postpartum. Septic foals displayed altered energy metabolisms as determined by increased triglycerides and cholesterol concentrations, hypoglycaemia at birth and reduced activity of the GGT and increased lactate and urea concentrations. Sepsis was associated with high concentrations of SAA and AFP.

Comparison of a continuous indwelling glucometer with a point-of-care device in healthy adult horses

BACKGROUND

Blood glucose is tightly regulated in horses; however, since hypoglycaemia and hyperglycaemia are associated with poor prognosis, close monitoring is warranted. This study aimed at evaluating a continuous indwelling glucometer (CIG) by comparing performance with a point-of-care glucometer (POC).

METHODS

Ten horses were equipped with CIG and an intravenous catheter. Interstitial glucose concentrations were determined by CIG every 5 min at rest, during insulin-induced hypoglycaemia and dextrose-induced hyperglycaemia, and compared with blood glucose determined by POC. Glucose concentrations were compared by two-way repeated measures analysis of variance and weighted kappa with Bland-Altman plots to determine agreement between assays.

RESULTS

Horses tolerated CIG well; however, five devices had to be replaced. There were no statistically significant differences between assays at rest or during hyperglycaemia; however, during hypoglycaemia, glucose concentrations determined by CIG were significantly higher (P=0.01). The mean bias (95% limits of agreement) between assays ranged from -0.03 (-2.46 to 2.52) mmol/l (hyperglycaemia) to 0.97 (-1.23 to 3.16) mmol/l (hypoglycaemia). Assay agreement was 'good' with observed agreements of 87.04% (κ=0.67).

CONCLUSIONS OF THE STUDY

CIG has acceptable accuracy in horses as compared with POC but overestimates glucose concentrations during hypoglycaemia and requires frequent replacement, limiting its clinical application.

Insulin dysregulation in horses with systemic inflammatory response syndrome

BACKGROUND

Systemic inflammation is a cause of insulin dysregulation in many species, but the insulin and glucose dynamics in adult horses diagnosed with systemic inflammatory response syndrome (SIRS) are poorly documented.

HYPOTHESIS/OBJECTIVES

In SIRS in horses, insulin and glucose dynamics will be altered and associated with survival.

ANIMALS

Adult horses diagnosed with SIRS admitted to a referral hospital.

METHODS

Prospective study enrolling horses diagnosed with SIRS in which serum insulin and glucose concentrations were measured. Horses were grouped by outcome (survival, hyperinsulinemia, and hyperglycemia) and compared with P < .05 considered significant.

RESULTS

Fifty-eight horses were included in the study and 36 (62%) survived. At admission, 21 horses (36%) were hyperinsulinemic and 44 horses (88%) were hyperglycemic, with survivors having significantly higher serum insulin and a significantly lower serum glucose concentration. Horses diagnosed with hyperinsulinemia at any time during hospitalization were 4 times more likely to survive whereas horses that were hyperglycemic at any time during hospitalization were 5 times less likely to survive. Serum glucose concentration and presence of hyperglycemia both were associated with severity of disease. Insulin/glucose ratio, reflecting insulin secretion, was significantly higher in survivors whereas glucose/insulin ratio, reflecting peripheral tissue insulin resistance, was significantly lower in nonsurvivors. Only in survivors was there a significant correlation between serum insulin and glucose concentrations.

CONCLUSIONS AND CLINICAL IMPORTANCE

Hyperinsulinemia and hyperglycemia are common features of SIRS in horses, but those presenting with relative hypoinsulinemia and corresponding hyperglycemia suggestive of endocrine pancreatic dysfunction have a worse prognosis.

Triglyceride concentrations in neonatal foals: Serial measurement and effects of age and illness

Few studies have evaluated the effects of age and illness on serum triglyceride concentrations in neonatal foals. The objectives of this study were to evaluate triglyceride concentrations in neonatal foals and their dams through serial measurement immediately postpartum and at 1-2 days and 10-12 days of age, as well as to measure them in sick foals. Serially measured serum triglycerides in seven healthy foals varied with age. Median (range) triglyceride concentrations were 28mg/dL (12-50mg/dL), 89mg/dL (51-264mg/dL), and 60mg/dL (28-135mg/dL) immediately postpartum, at 1-2 days of age, and 10-12 days of age, respectively (P<0.001). Triglyceride concentrations varied hourly by up to 117mg/dL in individual foals. The dams had lower triglycerides (median, 20mg/dL; range, 12-49mg/dL) than the foals, once foals were >24h old. Sick foals <24h old had lower triglycerides than sick foals aged 1-7 days (median, 41mg/dL [range, 16-116]; median, 110mg/dL [range, 24-379mg/dL]; P<0.001). Age and triglyceride concentration showed a non-linear association independent of foal health status (P=0.01). Sick foals with positive bacterial cultures had higher triglycerides than those with negative cultures (median, 111mg/dL [range, 10-379mg/dL] and median 53mg/dL [range, 17-271mg/dL], respectively; P=0.033). Nonsurvivors had higher triglycerides than survivors (median, 116mg/dL [range, 41-379mg/dL] and median, 55mg/dL [range, 10-311mg/dL], respectively; P=0.04). In conclusion, triglycerides were highest in healthy neonatal foals aged 1-2 days, and in nonsurviving sick foals and those with positive bacterial cultures. Age was associated with triglyceride concentration regardless of health status.

Glucocorticoid receptor density and binding affinity in healthy horses and horses with systemic inflammatory response syndrome

BACKGROUND

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis occurs in horses with systemic inflammatory response syndrome (SIRS). Peripheral resistance to glucocorticoids has not been investigated in horses.

OBJECTIVE

To determine if glucocorticoid receptor (GR) function in horses can be measured using flow cytometry, and to use this information to evaluate HPA axis dynamics.

ANIMALS

Eleven healthy adult horses in parts 1 and 2. Ten horses with SIRS and 10 age and sex matched controls in part 3.

METHODS

Flow cytometry was used to evaluate GR density and binding affinity (BA) in 3 healthy horses in part 1. In part 2, exogenous ACTH was administered to eight healthy horses. Their cortisol response and GR properties were measured. In part 3, CBC, serum biochemistry, cortisol and ACTH, and GR properties were compared between controls without SIRS (n = 10) and horses with SIRS (n = 10), and between survivors and nonsurvivors (n = 4 and n = 6 respectively).

RESULTS

Flow cytometry can be used to measure GR properties in equine PBMCs. No correlation was observed between plasma cortisol concentration and GR density or BA in healthy horses (r = -0.145, P = .428 and r = 0.046, P = .802 respectively). Nonsurvivors with SIRS had significantly decreased GR BA (P = .008). Horses with triglyceride concentration > 28.5 mg/dL had increased odds of nonsurvival (OR=117; 95% CI, 1.94-7,060). GR BA <35.79% was associated with nonsurvival (OR = 30.33; 95% CI, 0.96-960.5).

CONCLUSIONS AND CLINICAL IMPORTANCE

Tissue resistance to glucocorticoids contributes to HPA axis dysfunction in adult horses with SIRS. These horses might benefit from treatment with exogenous glucocorticoids.

The clinical value of whole blood point-of-care biomarkers in large animal emergency and critical care medicine

OBJECTIVE

To summarize the current medical literature and provide a clinical perspective of whole blood point-of-care (POC) biomarkers in large animal emergency and critical care practice.

DATA SOURCES

Original studies, reviews, and textbook chapters in the human and veterinary medical fields.

SUMMARY

POC biomarkers are tests used to monitor normal or disease processes at or near the patient. In both human and veterinary medicine these tools are playing an increasingly important role in the management of critical diseases. The most important whole blood POC biomarkers available for veterinary practitioners include l-lactate, cardiac troponin I, serum amyloid A, triglyceride, creatinine, and glucose, although many other tests are available or on the horizon.

CONCLUSION

Whole blood POC biomarkers enable clinicians to provide improved management of critical diseases in large animals. These tools are especially useful for establishing a diagnosis, guiding therapy, and estimating disease risk and prognosis.

Controversies surrounding critical illness-related corticosteroid insufficiency in animals

OBJECTIVES

To describe the controversies surrounding critical illness-related corticosteroid insufficiency (CIRCI) and the use of hydrocortisone in critically ill patients, and to present published diagnostic and therapeutic strategies in companion veterinary species.

ETIOLOGY

Critical illness-related corticosteroid insufficiency may be due to hypothalamic-pituitary-adrenal (HPA) axis dysfunction, alterations in cortisol-plasma protein binding, target cell enzymatic changes, changes in glucocorticoid receptor (GR) function, or a combination of these or other factors present during critical illness.

DIAGNOSIS

Appropriate tests to diagnose CIRCI are unknown. The diagnosis in people is currently based on response to treatment with hydrocortisone. There is currently no consensus on appropriate diagnostic feature(s) in veterinary species.

THERAPY

Low-dose hydrocortisone is the treatment of choice for patients with CIRCI.

PROGNOSIS

If the patient survives the critical illness, prognosis for resolution of CIRCI and hydrocortisone dependence is very good.

Update on the management of neonatal sepsis in horses

Despite advances in neonatal intensive care sepsis, severe sepsis and septic shock remain the biggest killers of neonatal foals. Management of this severe syndrome remains difficult, requiring intensive intervention. Key aspects of management include infection control, hemodynamic support, immunomodulatory interventions, and metabolic/endocrine support. Infection control largely consists of early antimicrobial therapy, plasma transfusions, and local therapy for the infected focus. In cases with severe sepsis or septic shock, hemodynamic support with fluids, vasoactive agents, and respiratory support insuring oxygen delivery to vital organs is important. Nutritional support is important, but close monitoring is needed to avoid hyperglycemia and hypoglycemia.