Minimal Anesthetic Concentration and Cardiopulmonary Dose Response of Isoflurane in Ducks

The minimal anesthetic concentration (MAC) for isoflurane was determined during spontaneous ventilation in nine male Peking ducks (7 to 12 weeks of age; 3.0 +/- 0.4 kg). While each bird was awake, arterial blood was collected for analysis of pH, PaCO2, and PaO2. After anesthesia was induced with isoflurane in oxygen, MAC was determined for isoflurane in each bird during spontaneous ventilation in a manner similar to MAC determinations in mammals. Pulmonary dose-response data were collected at 1 MAC and 1.5 MAC. Anesthetic index (Al; an index of anesthetic-induced apnea) was calculated from ducks that became apneic. The MAC for isoflurane was 1.30 +/- 0.23% (mean +/- SD). There was a dose-dependent decrease in ventilation as evidenced by a statistically significant increase in PaCO2. Apnea or unacceptable hypercarbia (PaCO2 greater than 110 mm Hg), or both, were common occurrences at end-tidal isoflurane concentrations greater than 1.5 MAC. Anesthetic index calculated from four ducks was 1.65 +/- 0.13 (mean +/- SEM). There was no significant difference between the means of either heart rate or mean arterial blood pressure in birds at 1.0 and 1.5 MAC.     

Acute noncardiogenic pulmonary edema in an anesthetized Nubian goat kid

ObservationsA 1-month-old Nubian goat presented for sialocyst resection. Physical examination and bloodwork were unremarkable. While pre-oxygenating, the goat was sedated with midazolam and morphine (0.1 mg kg^?1 each) intravenously (IV). General anesthesia was induced 5 minutes later with 1.7 mg kg^?1 propofol. Sevoflurane was administered in oxygen without assisted ventilation via a cuffed orotracheal tube. Throughout the first 85 minutes of anesthesia, the goat was well-oxygenated (SpO₂, ≥97%), ventilating adequately (Pe′CO₂, 36–48 mmHg), and had normal mean arterial blood pressure (MAP, 60–85 mmHg). Blood-gas values at 45 minutes were consistent with adequate ventilation on oxygen. At 75 minutes, the goat moved in response to surgical stimulation, requiring additional propofol (0.4 mg kg^?1). After 10 minutes, MAP dropped precipitously to 40 mmHg and frequent multiform premature ventricular contractions (PVCs) were observed. Crystalloids, hetastarch, and dopamine (5 μg kg^?1 minute^?1) were administered to correct the hypotension. Arterial blood-gas analysis revealed that the goat had become hypoxemic (PaO₂, 50 mmHg). Intermittent positive pressure ventilation (IPPV) was initiated. Subsequent blood-gas analysis did not show significant improvement in PaO₂ (53 and 56 mmHg, respectively). Occasional PVCs were observed thereafter. Surgery ended, and sevoflurane and IPPV were discontinued. The goat was extubated within 7 minutes and received 100% oxygen by mask. Diffuse crackles were ausculted over both hemithoraces. Suspecting pulmonary edema, furosemide (1 mg kg^?1) was administered IV. Radiographs taken immediately post-operatively revealed a severe, caudodorsal airspace (alveolar) pattern, confirming the diagnosis. Respiration improved considerably within an hour with nasal oxygen and two additional doses of furosemide.ConclusionsThe goat developed acute, drug-induced, noncardiogenic pulmonary edema in response to the second dose of propofol.     

DIAGNOSIS OF URINARY TRACT OBSTRUCTION IN DOGS USING DUPLEX DOPPLER ULTRASONOGRAPHY

The ability of duplex Doppler ultrasonography to assist with the diagnosis of urinary tract obstruction was investigated in a study of 5 dogs with surgically induced, unilateral ureteral obstruction. The resistive index (RI) of obstructed kidneys was compared to that of controls and to the contralateral unobstructed kidneys. The RI was also evaluated following relief of obstruction. On the basis of an RI measurement ≥0.70 indicating obstruction, a sensitivity of 73% and a specificity of 77% was determined for the diagnosis of obstruction with Doppler ultrasonography. Although mean RI was elevated in obstructed kidneys compared to controls, it was concluded that a high false-negative rate (27%) limits the clinical usefulness of Doppler ultrasonography for the detection of urinary obstruction in dogs. The RI difference between obstructed and nonobstructed kidneys was also evaluated within individual animals, but the magnitude of difference between kidneys did not significantly improve the detection rate for obstruction.     

Determination of cardiac output in neonatal foals by ultrasound velocity dilution and its comparison to the lithium dilution method

Objective – To compare cardiac output (CO) measured by use of lithium dilution (LiDCO) and ultrasound velocity dilution (UDCO) in conditions of high, intermediate, and low CO in anesthetized foals.
Design – Original prospective study.
Setting – University teaching hospital.
Animals – Six foals 1–3 days of age (38–45 kg).
Interventions – Neonatal foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, and CO. The CO was measured by use of LiDCO and UDCO techniques. Measurements were obtained from each foal at baseline and during low, intermediate, and high CO states. Measurements were converted to cardiac index (cardiac index=CO/body weight) values for statistical analysis. Agreement between the 2 methods was determined using Bland and Altman analysis and concordance correlation coefficients.
Measurements and Main Results – LiDCO determinations of CO ranged between 4.0 and 14.0 L/min resulting in cardiac index ranging between 75.5 and 310 mL/kg/min. There was no significant effect of blood pressure variation on bias or relative bias ( P =0.62 and 0.93, respectively). The mean bias and relative bias of UDCO (±SD) compared with LiDCO were −20.1±39.2 mL/kg/min and −7.7±23.4%, respectively. Concordance correlation coefficient between LiDCO and UDCO was 0.833.
Conclusions – When compared with LiDCO, the UDCO technique has acceptable clinical utility for measuring CO in healthy anesthetized newborn foals.     

Ultrasound appearance of the palmar metacarpal soft tissues of the horse

Using real-time ultrasound imaging, the normal anatomy of the soft tissues of the palmar aspect of the equine forelimb was examined. Sections of frozen specimens were prepared which correlated well with the ultrasound images. The superficial and deep digital flexor tendons, tendon sheaths, inferior check ligament (accessory ligament of the deep digital flexor tendon), suspensory ligament, contours of the apices of the proximal sesamoids and the intersesamoidean ligament, were identified.     

Benefits to foals of feeding soybean meal to lactating broodmares

In order to test the hypothesis that an improvement in the quality of the dietary protein fed lactating mares would improve the growth of their nursling foals, Thoroughbred mares were fed approximately isonitrogenous diets differing slightly in their amino acid compositions during the last 2 weeks of gestation and the first 7 weeks of lactation. The differences in the diets resulted from the substitution of a portion of the complete pelleted feed with soybean meal (SBM). The crude protein content of mares' milk was significantly increased by SBM substitution during the first 5 weeks of lactation. However, SBM did not prevent the gradual decline in protein content typical of mares' milk during the course of lactation. The relative amino acid composition of mares' milk was not changed by SBM substitution, suggesting that more growth-limiting amino acids were provided to the foals suckling from SBM-supplemented mares. The plasma concentrations of lysine, methionine, leucine, phenylalanine, histidine and valine were significantly greater in the foals of SBM-supplemented mares. Those foals grew in withers height about 10% more rapidly during their first 7 weeks of life. These findings indicate that the growth of nursing foals is responsive to the amino acid composition of their dams' diets.     

USE OF TRANSCOLONIC 123I-IODOAMPHETAMINE TO DIAGNOSE SPONTANEOUS PORTOSYSTEMIC SHUNTS IN 18 DOGS

Transcolonic ¹²³I-Iodoamphetamine is rapidly absorbed across the colonic mucosa and binds to amine receptors in the liver and lungs. During the first ten minutes following colonic administration, a simple ratio of lung counts to lung counts plus liver counts provides an accurate estimate of the fraction of portal blood that bypasses hepatic sinusoids in dogs with portosystemic shunts. Studies were performed on 24 dogs with suspect portosystemic shunt. Shunt fraction values for 18 dogs with surgically confirmed portosystemic shunt were obviously higher than published values for normal dogs, and also significantly higher than values for the other six dogs, later confirmed to lack shunts. Postoperative studies were repeated on ten dogs with single shunt vessels 1–2 days after shunt closure. Total shunt ligation resulted in normal postoperative shunt fraction, whereas partial shunt ligation resulted in persistant elevation of shunt fraction. Transcolonic iodoamphetamine scintigraphy is noninvasive, easy to perform, and provides an accurate method to diagnose dogs with portosystemic shunt.     

Comparison of Various Extenders for Storage of Cooled Stallion Spermatozoa for 72 Hours

Multiple extenders have been developed to preserve cooled stallion semen. Comparisons of some extenders have been made but there is need for further research in this area. Extenders tested included EZ Mixin (Animal Reproduction Systems, Chino, CA), Kenney's, Universal (NASCO, Fort Atkinson, WI), EquiPro, EquiPro CellGuard (Minitube of America, Verona, WI), and INRA 96 (IMV, Maple Grove, MN). Semen was collected and each ejaculate was divided and extended in each of the aforementioned extenders and stored at 4°C. Motility measures were determined using computer-assisted sperm analysis at 0, 24, 48, and 72 hours after collection. Samples were evaluated for total motility, progressive motility (PM), straight-line velocity, curvilinear velocity, straight-line distance, and curvilinear distance. Total motility and PM decreased over time in storage (P < .05). Sperm stored in INRA 96, EquiPro, and EquiPro Cell Guard retained the most total motility and PM over the 72 hour period (P < .05). Universal, EquiPro, and EquiPro Cell Guard had the highest measurements for curvilinear velocity, straight-line velocity, and curvilinear distance (P < .05). There were no significant differences among the extenders for straight-line distance.