Quantitative evaluation of contrast enhanced transcranial Doppler signal using galactose based echo-contrast agent in dogs

Transcranial Doppler ultrasonography (TCD) is hindered by insufficient ultrasound penetration through the temporal bone. The use of echo-contrast agents to enhance the Doppler signal is an important step toward the solution of this problem. The aim of the present study was to investigate the tolerability and diagnostic value of the intravenous echo-contrast agent, Levovist. Levovist was administered intravenously in 8 dogs with two doses (0.2 and 0.3 ml/kg) at different concentrations (300 and 400 mg/ml). In right middle cerebral artery (RMCA), the duration and degree of the signal enhancement were measured by TCD. All 32 administrations of Levovist produced an increase in TCD signal of the RMCA without complications. The first assessable pulse curve could be seen on the screen after 4 to 7 seconds after injection. There was no significant difference of latency period between different concentration and dosage. The signal amplitude was increased homogeneously by more than 30 dB when 0.3 ml/kg with 300 mg/ml concentration of Levovist and 0.2 and 0.3 ml/kg with 400 mg/ml concentration were administered. There was no significant difference in the duration of optimal contrasting between 0.3 ml/kg with 300 mg/ml concentration of Levovist and 0.2 and 0.3 ml/kg with 400 mg/ml concentration. The duration of the signal enhancement was 144 to 422 seconds, depending on the degree of concentration and dose of administration. Optimal TCD signal enhancement of RMCA was obtained using 0.3 ml/kg with 300 mg/ml concentration of Levovist in dogs, which is considered to provide quality visualization.     

Effect of catheter size and injection rate of contrast agent on enhancement and image quality for triple‐phase helical computed tomography of the liver in small dogs

Rapid contrast injection is recommended for triple‐phase helical computed tomography (CT) of the liver. However, a large‐gauge catheter is needed for faster contrast injection and this is not practical for small breed dogs or cats. The purpose of this crossover group study was to evaluate applicability of a lower injection rate with a small‐gauge (G) catheter for triple‐phase hepatic CT in small dogs. Triple‐phase CT images were acquired for six beagle dogs using three protocols: an injection rate of 1.5 ml/s with a 24 G catheter, 3.0 ml/s with a 22 G catheter, and 4.5 ml/s with a 20 G catheter. Enhancement of the aorta, portal vein, and hepatic parenchyma was measured in each phase (arterial, portal, and delayed) and image quality was scored subjectively by two observers. Injection duration, time to scan delay, and time to peak enhancement were also recorded. Contrast injection duration decreased with a higher injection rate (n = 6, P ≤ 0.01), but time to peak enhancement and time to scan delay were not significantly affected by injection rates and catheter sizes. Contrast injection rate did not significantly affect aortic, portal, and hepatic enhancement. In addition, separation between each phase and quality of images was subjectively scored as good regardless of injection rate. Findings from the current study supported using an injection rate of 1.5 ml/s with a catheter size of 24 G for triple‐phase hepatic CT in small dogs (weight < 12 kg).     

EFFECT OF CONTRAST MEDIUM INJECTION DURATION ON PEAK ENHANCEMENT AND TIME TO PEAK ENHANCEMENT OF CANINE PULMONARY ARTERIES

Our goal was to investigate the effect of contrast medium injection duration on pulmonary artery peak enhancement and time to peak enhancement. Fourteen dogs were allocated into one of seven predefined weight categories, each category contained two dogs. Dogs in each weight category were assigned to group A or B. Animals in each group received a different contrast medium injection protocol. In group A, a fixed injection rate of 5 ml/s was used. In group B, the contrast injection rate was calculated as follows: flow rate=contrast volume/scan duration+10 s. Time to peak enhancement and peak enhancement of the main left and right pulmonary arteries were measured on single‐level, dynamic CT images for a fixed time of 30 s. Rank correlation (Spearman's) coefficients between injection duration and time to peak enhancement and between body weight and peak enhancement were calculated. For group A, there was a significant negative correlation between peak enhancement and weight (r=?0.94; P=0.005), while for group B, there was no significant correlation (r=?0.64 and P=0.18). There was a significant correlation between time to peak enhancement and injection duration in both groups (group A: r=0.99; P=0.006 and group B: r=0.85; P=0.02). In conclusion, injection duration is a key feature in a CT angiography injection protocol. A protocol with an injection duration adjusted to the scan duration seems to be particularly suitable for veterinary applications where a population with great weight variability is studied.     

EFFECTS OF TWO CONTRAST INJECTION PROTOCOLS ON FELINE AORTIC AND HEPATIC ENHANCEMENT USING DYNAMIC COMPUTED TOMOGRAPHY

This prospective study compared aortic and hepatic enhancement achieved using a contrast injection protocol with a fixed rate of 5 ml/s vs. that achieved using a protocol with fixed injection duration of 20 s in eight cats. Cats were assigned into two groups (Group 1, rate 5 ml/s; Group 2, duration 20 s). The dose of contrast was the same in both groups (740 mgI/kg). Regions of interest (ROI) were drawn in the aorta and liver for transverse scans acquired at the hepatic hilus. Time to peak aortic enhancement occurred significantly earlier in Group 1 (M = 11s, SD = 1.63) than in Group 2 (M = 25.5 s, SD = 2.51). Peak aortic enhancement was significantly higher in Group 1 (M = 1906.51 HU, SD = 368.64) than in Group 2 (M = 745.08 HU, SD = 201.84). Duration of aortic enhancement equal to or above 300 HU was statistically longer in Group 2 (M = 24.5 s, SD = 8.39) than in Group 1 (M = 10 s, SD = 1.63). There were no significant differences in time to peak liver enhancement, peak liver enhancement, or duration of hepatic arterial phase between groups. Findings supported the hypothesis that longer injection duration results in a broader bolus geometry with a longer time to peak and a lower peak aortic enhancement in cat. This strong influence of injection duration on timing of aortic enhancement may help future users optimize protocols for CT angiography of the aorta and multiphasic evaluation of the liver, pancreas, and small intestine.     

DYNAMIC COMPUTED TOMOGRAPHY OF THE NORMAL FELINE HYPOPHYSIS CEREBRI (GLANDULA PITUITARIA)

The purpose of this study was to describe normal feline hypophyseal mensuration and contrast enhancement characteristics using dynamic computed tomography (CT) imaging. An intravenous bolus of an ionic iodinated contrast medium was administered to eight cats using a pressure injector while dynamic CT images were obtained every 5 s for five cats and every 7 s for three cats for a total imaging time of 5 min. Each pituitary was measured at its maximum height and width on the peak contrast medium enhancement image. A hand-drawn region of interest was placed around each hypophysis cerebri and time attenuation curves were generated. The specific enhancement pattern of the hypophysis cerebri for each cat was recorded. The mean width and height of the hypophysis cerebri was 5.2 +/- 0.4 (average +/- SD) mm and 3.1 +/- 0.3 mm, respectively. The mean time to maximum contrast enhancement was 28.6 +/- 14.8 s (range 14-50 s) from the onset of contrast medium injection. Four cats had initial dorsal and peripheral contrast enhancement patterns of the hypophysis cerebri, while four cats had an initial central contrast medium enhancement pattern. The hypophysis cerebri had a homogenous appearance in all cats, 28-50 s after contrast medium injection. The average (+/- SD) clearance half-time was 292 (+/- 87) s. Normal hypophysis cerebri mensuration and contrast medium enhancement characteristics will help in clinical evaluation of the feline hypophysis cerebri.     

PULMONARY ANGIOGRAPHY USING 16 SLICE MULTIDETECTOR COMPUTED TOMOGRAPHY IN NORMAL DOGS

We report a canine computed tomography (CT) pulmonary angiography technique using multidetector CT (MDCT). CT pulmonary angiography using a 16 slice MDCT was performed on five healthy, anesthetized beagles. A helical acquisition with pitch of 1.4 was used. The time delay for the angiographic study was determined using a bolus‐tracking program. A dose of 400 mg I/kg of nonionic contrast medium (Iohexol 300 mg I/ml) was administered to each dog via a cephalic catheter using an angiographic power injector at a rate of 5 ml/s. In two dogs a second study, using a contrast medium dose of 200 and 600 mg I/kg was performed. Arterial enhancement of transverse and reformatted images was classified subjectively as excellent, good, or poor, and assessed objectively by measuring Hounsfield units at the right main pulmonary artery. Angiographic studies were evaluated by two radiologists to determine the number of subsegmental arterial branches visualized. The median number of subsegmental arterial branches identified was five (range: 2–7). Based on the time attenuation curve obtained by the bolus‐tracking program, there was consistent enhancement of the right main pulmonary artery beginning at 6 s and peaking at 8 s in 4/5 dogs. The contrast medium dose of 400 mg I/kg produced good to excellent vascular enhancement in the same 4/5 dogs. A dose of 200 mg I/kg resulted in poor enhancement. CT pulmonary angiography using MDCT and an automated bolus‐tracking program allows rapid, consistent evaluation of the pulmonary vasculature using a single dose of 400 mg I/kg of contrast medium.     

Comparison of varying injection rates of saline chasers on intravascular contrast enhancement for dynamic CT in cattle

Dynamic CT was performed in five normal Holstein calves to investigate the effect of saline chasers on intravascular contrast enhancement when administered at three different rates. The five calves were imaged using dynamic CT in a crossover study design. Group A was administered only contrast medium (600 mg iodine/kg, 4 ml/s), while groups B, C and D were administered contrast medium at 30 per cent reduction followed by saline chasers injected at 2, 4 and 8 ml/s, respectively. Attenuation values were obtained from the right and left maxillary arteries and dorsal sagittal sinus. Maximum enhancement value and mean value of the enhancement plateau obtained from the maxillary arteries were significantly lower in group B than in the other groups. The duration of the enhancement plateau was longer in group C than in groups B and D (P<0.05).     

THE COMPUTED TOMOGRAPHIC ENHANCEMENT PATTERN OF THE NORMAL CANINE PITUITARY GLAND

Dynamic computed tomography (CT) of the pituitary gland was performed on four healthy male dogs of similar size, weight and age. The pituitary gland region was first identified on lateral scout and transverse non-contrast images. After localization, water soluble iodinated contrast medium was administered intravenously as a bolus at a dose of 1 ml/lb using a pressure injector at an injection rate of 10 ml/sec and a total of 40 post contrast images of the pitutary gland were acquired. No images were made after 400 seconds. The same pituitary region was imaged in each slice. The slice thickness was 1.5 mm, with a two second scan time and an eight second delay between images (resulting in images every ten seconds). The contrast medium injection and initial image were acquired simultaneously, resulting in a non-contrast enhanced initial image. At the completion of the CT scan, a region of interest (ROI) was drawn around the pituitary gland and time density data were obtained. The mean pituitary Hounsfield number was plotted as a function of time. A bi-exponential least squares model was used to derive the best fitting line through the data. The mean relative peak increase in pituitary Hounsfield Units (HU) was 65.9% +/- 2.1%. After the initial increase there was a decrease in pituitary Hounsfield number with a half-time of 16.1 seconds, followed by a slower phase with a half-time of 16.5 minutes. The mean pituitary gland HU value during the period of gradual opacity decline was 35.0% +/- 4.4% above that of the pre-contrast image. Establishing the enhancement pattern in the canine pituitary gland is the precursor to the clinical application of dynamic CT of the pituitary gland to diagnose pituitary microadenomas and/or small macroadenomas before they become exceptionally large.     

COMPARISON OF TRANSPLENIC MULTIDETECTOR CT PORTOGRAPHY TO MULTIDETECTOR CT-ANGIOGRAPHY IN NORMAL DOGS

We evaluated transplenic injection of iodinated contrast medium for computed tomography (CT) assessment of the portal vasculature. Specific aims were to: (1) establish a protocol for transplenic transplenic CT portography using a 40-row multidetector scanner; (2) compare transplenic CT portography to dual-phase CT angiography in terms of image quality, opacification of the portal system, and contrast enhancement of the portal vasculature and liver; (3) compare personnel exposure during transplenic CT portography and transplenic portal scintigraphy. Seven juvenile dogs underwent transplenic portal scintigraphy, CT angiography, and transplenic CT portography. Transplenic portal scintigraphy and CT angiography were performed using previously established protocols. For transplenic CT portography, a 20- or 22 gauge needle attached to an extension set was placed into the splenic parenchyma using CT guidance. Iodinated contrast medium (175 mg I/ml) was administered, and CT acquisition was started at the time of the injection. Transplenic CT portography was simple, rapid and provided more intense enhancement of the splenic and portal veins, with a lower contrast medium dose (median dose: 525 mg I for transplenic CT portography, 7700 mg I for CT angiography), but caused inconsistent intrahepatic portal branches and parenchymal opacification due to streamlining and streak artifacts. Despite significantly lower attenuation values in the portal vein, CT angiography provided sufficient enhancement for vessel identification and more consistent parenchymal hepatic enhancement. Personnel radiation exposure rate was higher during transplenic CT portography (0.0725 mSv/min) compared with transplenic portal scintigraphy (0.000125 mSv/min). As transplenic CT portography requires an average injection time of 1 min per study; over 650 [corrected] studies must be performed before reaching the maximum permissible whole body dose of 0.05 [corrected] Sv.     

Anatomical study of the gastrointestinal tract of a pudu (Pudu puda) using contrast-enhanced abdominal computed tomography

The pudu (Pudu puda), which is the smallest deer in the world and inhabits central and southern Chile and Argentina, is a ruminant and a browsing herbivore. The aim of this study was to provide a reference for interpretation of the normal anatomy of the pudu's gastrointestinal tract as imaged by abdominal computed tomography (CT). For the study, one adult female pudu was used. After a 24-h fast, the pudu was anaesthetized and positioned in sternal recumbency at the CT table. Image acquisition began immediately after intravenous injection of contrast media (MD-76(?); 370 mgI/ml) into the cephalic vein. Injection of contrast material was administered as a biphasic protocol. First, a manual bolus of contrast material was injected at a rate of 4 ml/s. Then, an additional continuous infusion injection (0.1 ml/min) was performed for adequate opacification of vascular structures. Transverse images of 5 mm thickness and 5 mm interval were obtained with a fourth-generation CT scanner, from the ninth thoracic vertebra (T9) until the first sacral (S1) vertebrae. CT images were labelled and compared with anatomical reference images for ruminants. Structures that were identified in the abdominal cavity included the stomach with its four compartments (rumen, reticulum, omasum and abomasum), the small and large intestines, liver, spleen, kidneys and some major blood vessels (aorta, caudal vena cava). The distal loop of the ascending colon, the transverse colon, the pancreas and lymph nodes could not be identified. The resulting CT images provide a reference for normal cross-sectional abdominal anatomy of the adult pudu.     

A comparison between injection speed and iodine delivery rate in contrast-enhanced computed tomography (CT) for normal beagles

The purpose of this study was to compare between the injection speed and iodine delivery rate in order to establish a concept for reproducible contrast timing in contrast-enhanced computed tomography (CT) for small animals. Clinically healthy beagle dogs were administered a nonionic iodinate contrast medium at a dose of 800 mgI/kg; they were divided into 3 groups (n=5, crossover method): in one group, the injection speed was fixed at 1.0 ml/sec, and in the second and third groups, the iodine delivery rate was fixed (the injection durations were 30 and 60 sec, respectively). The variation in scatter of the time to aortic and hepatic peak enhancement in the fixed iodine delivery groups was lower than that in the fixed injection speed group. These results suggest that in contrast-enhanced CT for small animals, the contrast medium should be injected at a fixed iodine delivery rate in order to provide reproducible contrast timing.     

CONTRAST‐ENHANCED ULTRASONOGRAPHY OF THE NORMAL CANINE ADRENAL GLAND

Contrast‐enhanced ultrasonography is useful in differentiating adrenal gland adenomas from nonadenomatous lesions in human patients. The purposes of this study were to evaluate the feasibility and to describe contrast‐enhanced ultrasonography of the normal canine adrenal gland. Six healthy female Beagles were injected with an intravenous bolus of a lipid‐shelled contrast agent (SonoVue^®). The aorta enhanced immediately followed by the renal artery and then the adrenal gland. Adrenal gland enhancement was uniform, centrifugal, and rapid from the medulla to the cortex. When maximum enhancement was reached, a gradual homogeneous decrease in echogenicity of the adrenal gland began and simultaneously enhancement of the phrenicoabdominal vessels was observed. While enhancement kept decreasing in the adrenal parenchyma, the renal vein, caudal vena cava, and phrenicoabdominal vein were characterized by persistent enhancement until the end of the study. A second contrast enhancement was observed, corresponding to the refilling time. Objective measurements were performed storing the images for off‐line image analysis using Image J (ImageJ^©). The shape of the time–intensity curve reflecting adrenal perfusion was similar in all dogs. Ratios of the values of the cortex and the medulla to the values of the renal artery were characterized by significant differences from initial upslope to the peak allowing differentiation between the cortex and the medulla for both adrenal glands only in this time period. Contrast‐enhanced ultrasonography of the adrenal glands is feasible in dogs and the optimal time for adrenal imaging is between 5 and 90 s after injection.     

The effect of growth hormone-releasing peptide-2 (KP102) administration on plasma insulin-like growth factor (IGF)-1 and IGF-binding proteins in Holstein steers on different planes of nutrition

This study was conducted to investigate the nutrition-dependent changes in insulin-like growth factor (IGF)-1 and IGF-binding proteins (IGFBPs) with growth hormone releasing peptide-2 (D-Ala-D-betaNal-Ala-Trp-D-Phe-Lys-NH(2); GHRP-2 or KP102) treatment in growing Holstein steers. Eight 13 month-old Holstein steers were grouped on two levels of feed intake (high intake (HI); 2.43% body weight or low intake (LI); 1.22%) and each group was daily injected with KP102 (12.5 microg/kg body weight/day) or saline solution into the jugular vein during 6-day period. The concentration of plasma GH showed an increase after an i.v. bolus injection of KP102 on Day 1 and Day 6 in both the LI and HI groups. Plasma IGF-1 began to increase 10 hr following an i.v. bolus injection of KP102, but this was only observed in the HI group (P < 0.05). Also, the plasma IGF-1 in the HI group with daily injections was significantly greater than the LI group from Day 1 of KP102 administration (P < 0.05). It reached maximum values of 125.1 +/- 7.6 ng/ml after Day 2, and returned to pre-injection levels after Day 4, however, no change in plasma IGF-1 was observed in LI with administration of KP102. During 6 days of treatment, plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 were significantly higher in KP102 treated steers but only in the HI group (P < 0.05). Plasma 34 kDa IGFBP-2 decreased in the HI group and did not show any change following an injection of KP102. In conclusion, the effect of stimulated endogenous GH with KP102 administration increased plasma IGF-1, 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 levels in the HI group of growing Holstein steers, but not in the LI one. Thus, we strongly believe that the plasma IGF-1 and IGFBPs response to KP102 treatment is modulated by the nutritional status of growing Holstein steers and the increased plasma IGF-1 concentration with KP102 treatment may be regulated by plasma 38-43 kDa IGFBP-3 and 24 kDa IGFBP-4 in Holstein steers.     

Contrast harmonic imaging of canine hepatic tumors

Six adult healthy Beagles were used to investigate the hepatic perfusion dynamics of Levovist, a contrast agent used in contrast harmonic imaging (CHI). In addition, 8 dogs with hepatocellular carcinoma (HCC) and 2 dogs with metastatic hepatic hemangiosarcoma (HSA) were used to characterize both the CHI findings with Levovist. In the Beagles, the start of intravenously injected Levovist into the aorta between the cranial mesenteric and renal arteries and the portal vein at the hepatic hilum were 5.47 +/- 1.52 sec and 16.03 +/- 3.39 sec, respectively. As a characteristic CHI finding in the 8 dogs with HCC, the early arterial phase showed a fine network of blood flow enhanced at the surrounding region and within the tumor in all the 8 dogs (100%), and the post vascular phase demonstrated a defect in the whole tumor and an enhancement of the surrounding hepatic tissues in 7 dogs (87.5%). In the 2 dogs with HSA, characteristic finding in which the early arterial and late vascular phases showed a rim contrast enhancement pattern, and the post vascular phase revealed that the whole tumor lacked contrast enhancement and the surrounding hepatic tissues was clearly enhanced. In dogs, the start of the early arterial and late vascular phases, and the characterizations of the CHI findings in HCC and HSA were suggested to be similar to those in humans. Therefore, CHI is thought to be useful for the diagnosis of HCC and metastatic hepatic HSA in dogs as well as in humans.     

Serum activity/concentration profiles of a sustained-released formulation of sulphathiazole-trimethoprim (2.5:1) in calves

Thirty-six two-week-old healthy Holstein-Friesian calves weighing between 52 and 58 kg were divided at random into three groups of 12; group A calves were given a single oral bolus containing 2.5 g sulphathiazole and 1 g trimethoprim in a sustained-release formulation; group B received the same doses of the drugs but the trimethoprim was not in a sustained-release formulation; group C received a bolus containing 2.5 g sulphathiazole and 0.5 g conventional trimethoprim. Blood samples were collected at intervals for two days, the serum was separated and the composite antibacterial activity profiles of the mixture were analysed by an agar-diffusion microbiological method. The mean maximum activities in the serum of the three groups were 23.4 microg/ml in group A, 9.25 microg/ml in group B and 8.01 microg/ml in group C. The mean areas under the curves of the serum activity time curves were 838 microg/ml/hour in group A, 216 microg/ml/hour in group B and 182 microg/ml/hour in group C.     

Cardiopulmonary effects of continuous intravenous infusion of guaifenesin, ketamine, and xylazine in ponies

Eight ponies were anesthetized with a solution containing 50 mg of guaifenesin, 1 mg of ketamine, and 0.5 mg of xylazine X ml-1 of 5% dextrose in water. Anesthesia was induced by IV injection (1.1 ml X kg-1), followed by continuous IV infusion at 2.75 ml X kg-1 X hr-1. Heart rate, rate-pressure product, mean pulmonary artery pressure, and standard bicarbonate were not significantly changed throughout the study. Systolic, diastolic, and mean arterial pressures and left ventricular stroke work index were significantly decreased at 5 and 15 minutes after a bolus of the anesthetic solution was injected. Systolic blood pressure returned to within the base-line range at 30 minutes, but diastolic and mean arterial pressures were significantly decreased throughout the study. Cardiac index and arterial pH were decreased at 5 minutes only. Systemic vascular resistance was significantly decreased 60 minutes after bolus injection was given. Hypoventilation, as indicated by increased PaCO2, occurred 5 minutes after bolus injection was given.     

Optimal placement of the region of interest for bolus tracking on brain computed tomography angiography in Beagle dogs

This study aimed to determine the optimal placement of the region of interest (ROI) among four anatomical sites—pulmonary artery (PA), pulmonary vein (PV), aortic arch (AA), and carotid artery (CA)—in computed tomography (CT) brain angiography with automatic bolus tracking in healthy beagle dogs. Six beagles were included, and CT brain angiography was performed four times for each dog, to cover each ROI. The scan parameters, amount, and injection rate of the contrast medium were the same. The major intracranial arteries were selected for quantitative and qualitative evaluation: caudal cerebellar artery (CcA), basilar artery (BA), rostral cerebellar artery (RcA), caudal cerebral artery (CCA), middle cerebral artery (MCA), and rostral cerebral artery (RCA). Quantitative evaluation showed significantly higher CT attenuation values for the RcA, CCA, and MCA in the PA group and RcA and MCA in the PV group than in the CA group. Qualitative analysis revealed significantly higher scores for the BA, CCA, and MCA in the PA and PV groups than in the CA group. Venous contamination did not differ significantly among the ROIs, but the mean scores of the AA and CA groups were higher than those of the PA and PV groups. CT brain angiography using bolus tracking in the beagle dogs showed that the ROI should be placed at the PA or PV rather than at the CA for optimal images with strong contrast enhancement of the BA, RcA, CCA, and MCA and minimal venous contamination.     

Study of enteral versus parenteral application of the gonadotropin releasing hormone agonist Gonadorelin[6-D-Phe] (D-Phe6-LHRH) on LH secretion in Goettinger miniature pigs

With respect to the assessment of residue situation and as a part of preclinical trials to determine the biological activities of potential gonadotropin releasing hormone (GnRH) residues in porcine organisms the GnRH agonist Gonadorelin[6-D-Phe] (D-Phe(6)-LHRH) was administered either enterally or intramuscularly (i.m.) to female Goettinger miniature pigs in order to evaluate the GnRH-induced luteinizing hormone (LH) surge. Gilts received an (i) enteral application of 10 mg D-Phe(6)-LHRH via a probang (enteral group, n=7), (ii) i.m. injection of 0.1 mg D-Phe(6)-LHRH (parenteral group, n=5), or (iii) saline injection (control group, n=4). The GnRH and saline applications were repeated every second day with up to seven repetitions. Blood samples were collected via previously fitted jugular catheters immediately before injections, over an 8 h period in 1 h intervals beginning 2 h after injections, and at 24, 26, 28 and 30 h after applications. Enteral application of D-Phe(6)-LHRH induced an LH surge in 23 of 30 treatments. All gilts in the parenteral group exhibited LH release after each D-Phe(6)-LHRH application (P<0.05), whereas no LH surges were observed after saline injection in the control group. A significant (P<0.05) LH rise to mean maximum LH concentrations of 3.25 +/- 0.43 and 3.05 +/- 0.26 ng/ml occurred in both the enteral and parenteral groups, but there was no difference in the time interval after GnRH (2.6 +/- 0.3 vs. 2.3 +/- 0.3 h) and the mean duration of LH peak (6.5 +/- 0.4 and 6.8 +/- 0.3 h) between the treatment groups. In conclusion, (i) enteral application of 10 mg D-Phe(6)-LHRH induced LH release in a physiological range from the pituitary of female minipigs, and (ii) neither an accumulative effect nor a cumulative LH response were found after repeated GnRH application. Furthermore, (iii) in regard to consumer protection and gonadotropin secretion, D-Phe(6)-LHRH residues can be excluded from having long-term effects.     

Comparison of continuous infusion with intermittent bolus administration of cefotaxime on blood and cavity fluid drug concentrations in neonatal foals

Hewson, J., Johnson, R., Arroyo, L. G., Diaz‐Mendez, A., Ruiz‐López, J. A., Gu, Y., del Castillo, J. R. E. Comparison of continuous infusion with intermittent bolus administration of cefotaxime on blood and cavity fluid drug concentrations in neonatal foals. J. vet. Pharmacol. Therap.  36 , 68–77. Healthy neonatal foals were treated with cefotaxime by bolus (40 mg/kg IV q6h for 12 doses; n = 10) or by infusion (loading dose of 40 mg/kg IV followed by continuous infusion of a total daily dose of 160 mg/kg per 24 h for 3 days; n = 5). Population pharmacokinetics was determined, and concentrations in cavity fluids were measured at steady state (72 h). Highest measured serum drug concentration in the bolus group was 88.09 μg/mL and minimum drug concentration (C_min) was 0.78 μg/mL at 6‐h postadministration (immediately before each next dose), whereas infusion resulted in a steady‐state concentration of 16.10 μg/mL in the infusion group. Mean cefotaxime concentration in joint fluid at 72 h was higher (P = 0.051) in the infusion group (5.02 μg/mL) compared to the bolus group (0.78 μg/mL). Drug concentration in CSF at 72 h was not different between groups (P = 0.243) and was substantially lower than serum concentrations in either group. Insufficient data on pulmonary epithelial lining fluid were available to compare the methods of administration for cefotaxime in this cavity fluid. Results support continuous drug infusion over bolus dosing in the treatment for neonatal foal septicemia to optimize time that cefotaxime concentration exceeds the minimum inhibitory concentration of common equine pathogens.     

HELICAL COMPUTED TOMOGRAPHIC ANGIOGRAPHY OF THE NORMAL CANINE PANCREAS

Helical abdominal computed tomography (CT) was performed in nine normal beagle-mix dogs. Following cephalic vein injection of ionic iodinated contrast medium via power injector (rate 5 ml/s) dual-phase CT was performed in all dogs. A delayed scan was performed in five dogs between 5 and 13 min after the contrast medium injection. The median time of appearance of contrast medium in the aorta and gastroduodenal artery was 6.3 and 7 s, post start injection and 12 and 12.2 s in the gastroduodenal and portal vein, resulting in a purely arterial pancreatic time window of 5-6s. Pancreatic veins and parenchyma remained enhanced until the end of the dynamic scan (40s). The pancreatic parenchyma showed heterogeneous arterial and homogenous venous contrast enhancement which was slightly hypoattenuating compared to the liver. Delayed scans provided best delineation of the pancreas from the liver. The common bile duct could be identified ventral and to the right of the portal vein joining the dorsomedial aspect of proximal duodenum. Because of the very short time window and variable onset of pure arterial enhancement careful planning of dual-phase studies with previous dynamic CT is recommended. Dual-phase CT angiography enables assessment of the arterial supply, parenchymal perfusion and venous drainage of the canine pancreas.