Objective—To compare the diagnostic performance of a point-of-care (POC) analyzer with that of established methods for the measurement of plasma IgG, total protein, and albumin concentrations in neonatal foals.
Animals—100 neonatal foals < 7 days of age.
Procedures—Plasma IgG, total protein, and albumin concentrations were measured with a POC analyzer via an immunoturbidimetric method. Corresponding measurements of plasma IgG, total protein, and albumin concentrations were measured by means of automated biochemical analyzers via automated immunoturbidimetric, biuret, and bromocresol green dye–binding assays, respectively (standard laboratory methods).
Results—The sensitivity and specificity of the POC analyzer for detection of failure of passive transfer of immunity (FPTI) in foals were 80.7% and 100%, respectively, when FPTI was defined as a plasma IgG concentration < 400 mg/dL and were 75.9% and 100%, respectively, when FPTI was defined as a plasma IgG concentration < 800 mg/dL. The POC analyzer overestimated plasma albumin concentrations and, to a lesser extent, plasma total protein concentrations, compared with values determined with the standard laboratory methods.
Conclusions and Clinical Relevance—Results suggested the POC analyzer was acceptable for determination of plasma IgG and total protein concentrations in ill foals. The POC analyzer overestimated plasma albumin concentration such that its use was clinically unacceptable for the determination of that concentration. The POC analyzer provided timely measurements of plasma IgG concentrations, which is necessary information for the assessment of passive transfer of maternal antibodies to neonatal foals.
OBJECTIVE To assess multiple central venous and arterial blood variables that alone or in conjunction with one another reflect global oxygenation status in healthy neonatal foals.
ANIMALS 11 healthy neonatal foals.
PROCEDURES Central venous and arterial blood samples were collected from healthy neonatal foals at 12, 24, 36, 48, 72, and 96 hours after birth. Variables measured from central venous and arterial blood samples included oxygen saturation of hemoglobin, partial pressure of oxygen, lactate concentration, partial pressure of carbon dioxide, and pH. Calculated variables included venous-to-arterial carbon dioxide gap, estimated oxygen extraction ratio, ratio of partial pressure of oxygen in arterial blood to the fraction of inspired oxygen, bicarbonate concentration, base excess, and blood oxygen content.
RESULTS Significant differences between arterial and central venous blood obtained from neonatal foals were detected for several variables, particularly partial pressure of oxygen, oxygen saturation of hemoglobin, and oxygen content. In addition, the partial pressure of carbon dioxide in central venous blood samples was significantly higher than the value for corresponding arterial blood samples. Several temporal differences were detected for other variables.
CONCLUSIONS AND CLINICAL RELEVANCE Results of this study provided information about several variables that reflect global oxygenation in healthy neonatal foals. Values for these variables in healthy foals can allow for comparison with values for critically ill foals in future studies. Comparison of these variables between healthy and ill foals may aid in treatment decisions and prognosis of clinical outcome for critically ill foals.
Objective—To evaluate baseline plasma cortisol and ACTH concentrations and responses to low-dose ACTH stimulation testing in ill foals.
Animals—58 ill foals.
Procedures—Baseline cortisol and ACTH concentrations and cortisol concentrations after administration of a low dose of cosyntropin were determined within 6 hours after admission. Foals were assigned to 4 groups on the basis of age (≤ 24 hours vs 1 to 56 days) and presence of septicemia (yes vs no). Values were compared among groups and with values previously reported for healthy foals.
Results—Plasma cortisol concentrations 30 and 60 minutes after cosyntropin administration in foals ≤ 24 hours old were significantly higher than corresponding cortisol concentrations in older foals. In all 4 groups, plasma cortisol concentration 30 minutes after cosyntropin administration was significantly higher than baseline cortisol concentration or concentration 60 minutes after cosyntropin administration. No differences in baseline cor-tisol or ACTH concentration or in the ACTH-to-cortisol ratio were detected between groups or when ill foals were compared with healthy foals. A small number of ill foals had low baseline cortisol and ACTH concentrations or low responses to cosyntropin administration, compared with healthy foals.
Conclusions and Clinical Relevance—Results indicated that most ill foals in the present study population had adequate responses to cosyntropin administration. However, a small subset of ill foals appeared to have dysfunction of the hypothalamic-pituitary-adrenal axis.
Objective—To investigate tissue diffusion of anesthetic agent following administration of low palmar nerve blocks (LPBs) in horses.
Design—Randomized clinical trial.
Animals—12 adult horses.
Procedures—In 9 horses, mepivacaine hydrochloride–iohexol (50:50 dilution) injections were administered bilaterally (2 or 4 mL/site) to affect the medial and lateral palmar and palmar metacarpal nerves (4 sites). Lateral radiographic views of both metacarpal regions were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after block administration; proximal and distal extents of contrast medium (and presumably anesthetic agent) diffusion from palmar and palmar metacarpal injection sites were measured and summed to determine total diffusion. Methylene blue solution was injected in forelimbs of 3 other horses that were subsequently euthanized to determine the potential route of anesthetic agent diffusion to the proximal suspensory ligament region.
Results—Mean extents of proximal and total contrast medium diffusion were 4.0 and 6.6 cm, respectively, for the palmar metacarpal nerves and 4.3 and 7.1 cm, respectively, for the palmar nerves. Subtle proximal diffusion secondary to lymphatic drainage was evident in 17 of the 18 limbs. Contrast medium was detected in the metacarpophalangeal joint or within the digital flexor tendon sheath in 8 and 7 limbs, respectively. In the cadaver limbs, methylene blue solution did not extend to the proximal suspensory ligament region.
Conclusions and Clinical Relevance—In horses, LPBs resulted in minimal proximal diffusion of anesthetic agent from the injection sites. Limbs should be aseptically prepared prior to LPB administration because inadvertent intrasynovial injection may occur.
To determine the accuracy of 2 interstitial glucose-monitoring systems (GMSs) for use in horses compared with a point-of-care (POC) glucometer and standard laboratory enzymatic chemistry method (CHEM).
8 clinically normal adult horses.
One of each GMS device (Dexcom G6 and Freestyle Libre 14-day) was placed on each horse, and blood glucose concentration was measured via POC and CHEM at 33 time points and compared with simultaneous GMS readings. An oral glucose absorption test (OGAT) was performed on day 2, and glucose concentrations were measured and compared.
Glucose concentrations were significantly correlated with one another between all devices on days 1 to 5. Acceptable agreement was observed between Dexcom G6 and Freestyle Libre 14-day when compared with CHEM on days 1, 3, 4, and 5 with a combined mean bias of 10.45 mg/dL and 1.53 mg/dL, respectively. During dextrose-induced hyperglycemia on day 2, mean bias values for Dexcom G6 (10.49 mg/dL) and FreeStyle Libre 14-day (0.34 mg/dL) showed good agreement with CHEM.
Serial blood glucose measurements are used to diagnose or monitor a variety of conditions in equine medicine; advances in near-continuous interstitial glucose monitoring allow for minimally invasive glucose assessment, thereby reducing stress and discomfort to patients. Data from this study support the use of the Dexcom G6 and Freestyle Libre 14-day interstitial glucose-monitoring systems to estimate blood glucose concentrations in horses.
Objective—To evaluate the precision of intradermal
testing (IDT) in horses.
Animals—12 healthy adult horses.
Procedure—IDT was performed on the neck of each
horse by use of 2 positive control substances (histamine
and phytohemagglutinin [PHA]) and a negative
control substance. An equal volume (0.1 mL) for each
injection was prepared to yield a total of 20 syringes
([4 concentrations of each positive control substance
plus 1 negative control substance] times 2 positive
control substances times 2 duplicative tests) for each
side of the neck. Both sides of the neck were used for
IDT; therefore, 40 syringes were prepared for each
horse. Hair was clipped on both sides of the neck, and
ID injections were performed. Diameter of the skin
wheals was recorded 0.5, 4, and 24 hours after ID
Results—Intra- and interhorse skin reactions to ID
injection of histamine and PHA resulted in wheals of
uniform size at 0.5 and 4 hours, respectively.
Significant intra- and interhorse variation was detected
in wheals caused by PHA at 24 hours.
Conclusions and Clinical Relevance—ID injection of
histamine and PHA caused repeatable and precise
results at 0.5 and 4 hours, respectively.
Concentrations of 0.005 mg of histamine/mL and
0.1 mg of PHA/mL are recommended for use as positive
control substances for IDT in horses. This information
suggests that consistent wheal size is evident
for ID injection of control substances, and variation in
wheals in response to ID injection of test antigens
results from a horse's immune response to specific
antigens. (Am J Vet Res 2005;66:1341–1347)