Total intravenous anesthesia with ketamine–medetomidine–propofol in horses

Propofol is a potentially useful intravenous anesthetic agent for total intravenous anesthesia (TIVA) in horses. The purpose of this study was to compare the anesthetic and cardiorespiratory effects of TIVA following the administration of propofol alone(P–TIVA) and ketamine–medetomidine–propofol (KM–P–TIVA) in adult horses. The carotid artery was translocated to a subcutaneous position during TIVA with P–TIVA (n = 6) or KM–P–TIVA (n = 6). All horses were premedicated with medetomidine [0.005 mg kg^–1, intravenously (IV)]. Anesthesia was induced with midazolam (0.04 mg kg^–1 IV) and ketamine (2.5 mg kg IV). All horses were orotracheally intubated and breathed 100% oxygen. The KM drug combination (ketamine 40 mg mL^–1 and medetomidine 0.05 mg mL^–1) was infused at a rate of 0.025 mL kg^–1 hour^–1. Subsequently, a loading dose of propofol (0.5 mg kg^–1, bolus IV) was administered to all horses; surgical anesthesia (determined by horse response to incision and surgical manipulation, positive response being purposeful or spontaneous movement of limbs or head) was maintained by varying the propofol infusion rate as needed. Arterial blood pressure and HR were also monitored. Both methods of producing TIVA provided excellent general anesthesia for the surgical procedure. Anesthesia time was 115 ± 17 (mean ± SD) and 112 ± 11 minutes in horses anesthetized with KM–P–TIVA and P–TIVA, respectively. The infusion rate of propofol required to maintain surgical anesthesia with KM–P–TIVA was significantly less than for P–TIVA (mean infusion rate of propofol during anesthesia; KM–P–TIVA 0.15 0.02 P–TIVA 0.23 ± 0.03 mg kg^–1 minute^–1, p = 0.004). Apnea occurred in all horses lasting 1–2 minutes and intermittent positive pressure ventilation was started. Cardiovascular function was maintained during both methods of producing TIVA. There were no differences in the time to standing after the cessation of anesthesia (KM–P–TIVA 62 ± 10 minutes versus P–TIVA 87 ± 36 minutes, p = 0.150). The quality of recovery was good in KM–P–TIVA and satisfactory in P–TIVA. KM–P–TIVA and P–TIVA produced clinically useful general anesthesia with minimum cardiovascular depression. Positive pressure ventilation was required to treat respiratory depression. Respiratory depression and apnea must be considered prior to the use of propofol in the horse.     

Astaxanthin Normalizes Epigenetic Modifications of Bovine Somatic Cell Cloned Embryos and Decreases the Generation of Lipid Peroxidation

Astaxanthin is an extremely common antioxidant scavenging reactive oxygen species (ROS) and blocking lipid peroxidation. This study was conducted to investigate the effects of astaxanthin supplementation on oocyte maturation, and development of bovine somatic cell nuclear transfer (SCNT) embryos. Cumulus–oocyte complexes were cultured in maturation medium with astaxanthin (0, 0.5, 1.0, or 1.5 mg/l), respectively. We found that 0.5 mg/l astaxanthin supplementation significantly increased the proportion of oocyte maturation. Oocytes cultured in 0.5 mg/l astaxanthin supplementation were used to construct SCNT embryos and further cultured with 0, 0.5, 1.0 or 1.5 mg/l astaxanthin. The results showed that the supplementation of 0.5 mg/l astaxanthin significantly improved the proportions of cleavage and blastulation, as well as the total cell number in blastocysts compared with the control group, yet this influence was not concentration dependent. Chromosomal analyses revealed that more blastomeres showed a normal chromosomal complement in 0.5 mg/l astaxanthin treatment group, which was similar to that in IVF embryos. The methylation levels located on the exon 1 of the imprinted gene H19 and IGF2, pluripotent gene OCT4 were normalized, and global DNA methylation, H3K9 and H4K12 acetylation were also improved significantly, which was comparable to that in vitro fertilization (IVF) embryos. Moreover, we also found that astaxanthin supplementation significantly decreased the level of lipid peroxidation. Our findings showed that the supplementation of 0.5 mg/l astaxanthin to oocyte maturation medium and embryo culture medium improved oocyte maturation, SCNT embryo development, increased chromosomal stability and normalized the epigenetic modifications, as well as inhibited overproduction of lipid peroxidation.     

Clinical evaluation of balanced anesthesia using infusion of midazolam–ketamine–medetomidine in combination with inhalation of sevoflurane (MKM–OS anesthesia) in horses

MKM–OS anesthesia provides general anesthesia with minimum cardiovascular depression in experimental horses. The purpose of this study was to evaluate the effect of MKM–OS anesthesia in clinical cases. Sixty‐eight horses were anesthetized with MKM–OS anesthesia for selective or emergency surgery. The horse physical status was categorized based upon the American Society of Anesthesiologists (ASA) classification scheme. Forty‐four horses were classified as ASA I or II (low‐risk; 30 soft tissue, eight ophthalmic, and six orthopedic surgeries) and 24 horses were classified as ASA III to V (high‐risk; 24 emergency colic surgeries). All horses were administered medetomidine (0.005 mg kg^–1 IV) as premedication and anesthetized with ketamine (2.5 mg kg^–1 IV) and midazolam (0.04 mg kg^–1 IV). The horses were orotracheally intubated and connected to a large animal breathing circuit that delivered oxygen‐sevoflurane and administered the midazolam (0.8 mg mL^–1)‐ketamine (40 mg mL^–1)‐medetomidine (0.05 mg mL^–1) drug combination at a rate of 0.025 mL kg^–1 hour^–1. Surgical anesthesia was maintained by controlling the dial setting of the sevoflurane vaporizer and achieved by delivering 1.6–1.8% of end‐tidal sevoflurane concentration. All horses were mechanically ventilated during anesthesia. Hypercapnia and hypoxia were not sufficiently improved in high‐risk horses (PaCO₂; low‐risk 45–53 mm Hg versus high‐risk 56–60 mm Hg, p < 0.01: PaO₂ low‐risk 248–388 mm Hg versus high‐risk 95–180 mm Hg, p < 0.01). Heart rate was significantly higher in high‐risk horses (low‐risk 37–42 bpm versus high‐risk 44–73 bpm, p < 0.01). Dobutamine infusion was required in five low‐risk (11%) and 17 high‐risk horses (68%) to maintain mean arterial blood pressure >70 mm Hg. Eleven high‐risk horses died during the perioperative period (three euthanized during surgery, two died during recovery, six died after recovery). The quality of recovery was good in low‐risk horses and good to satisfactory in high‐risk horses. MKM–OS anesthesia provided excellent surgical anesthesia with minimal to mild cardiovascular depression in low risk‐horses and mild to moderate cardiovascular depression in high risk‐horses. The possibility of preserve cardiovascular function could be the advantage of MKM–OS anesthesia in high‐risk horses.     

Long Chain Fatty Acids of Diet as Factors Influencing Reproduction in Cattle

Cattle are fed moderate amounts of long chain fatty acids (FA) with the objective to enhance lactation and growth; however, recent interest on lipid feeding to cows has focused on reproduction, immunity and health. Increasing the caloric density of the ration by fat feeding has generally improved measures of cow reproduction, but when milk yield and body weight losses were increased by fat supplementation, positive effects on reproduction were not always observed. Feeding fat has influenced reproduction by altering the size of the dominant follicle, hastening the interval to first postpartum ovulation in beef cows, increasing progesterone concentrations during the luteal phase of the oestrous cycle, modulating uterine prostaglandin (PG) synthesis, and improving oocyte and embryo quality and developmental competence. Some of these effects were altered by the type of FA fed. The polyunsaturated FA of the n-6 and n-3 families seem to have the most remarkable effects on reproductive responses of cattle, but it is not completely clear whether these effects are mediated only by them or by other potential intermediates produced during rumen biohydrogenation. Generally, feeding fat sources rich in n-6 FA during late gestation and early lactation enhanced follicle growth, uterine PG secretion, embryo quality and pregnancy in cows. Similarly, feeding n-3 FA during lactation suppressed uterine PG release, and improved embryo quality and maintenance of pregnancy. Future research ought to focus on methods to improve the delivery of specific FA and adequately powered studies should be designed to critically evaluate their effects on establishment and maintenance of pregnancy in cattle.     

Comparison of noninvasive cardiac output measurements by transthoracic bioimpedance, partial carbon dioxide rebreathing, and transesophageal echocardiography with the thermodilution technique in beagle dogs

Most methods for determining cardiac output (CO) have limited application in clinical practice due to the invasive techniques required. This study compared the thermodilution technique (TDCO) with three noninvasive methods for determining CO in anesthetized dogs: transthoracic bioimpedance (BICO), partial CO₂ rebreathing (NICO), and transesophageal echocardiography (TEECO). TDCO was compared to BICO, NICO, and TEECO in six adult sevoflurane anesthetized beagle dogs (9.1–13.0 kg). All dogs were administered midazolam [0.3 mg kg^?1, intravenously (IV)] and butorphanol (0.1 mg kg^?1 IV), followed by ketamine (5.0 mg kg^–1 IV) and sevoflurane in nitrous oxide (1 L minute^–1) and oxygen (1 L minute^–1) and mechanically ventilated. Dogs were maintained at 2.2% end‐tidal sevoflurane (ETsev) concentration for instrumentation and baseline measurements. Low (5.0% ETsev), intermediate (3.3% ETsev), and high cardiac output values were achieved by varying the end‐tidal sevoflurane concentration and the administration of dobutamine (3–10 g kg^–1 minute^–1 and 2.2% ETsev). A minimum of thirty data sets was obtained for each comparison. The correlation coefficients when compared to TDCO were 0.684 for BICO (p < 0.0001), 0.883 for NICO (p < 0.0001), and 0.991 for TEECO (p < 0.0001). Cardiac output values ranged 50–444 mL kg^–1 minute^–1 for TDCO, 100–253 mL kg^–1 minute^–1 for BICO, 64–214 mL kg^–1 minute^–1 for NICO, and 52–401 mL kg^–1 minute^–1 for TEECO. The differences when compared to TDCO ranged – 62–235 mL kg^?1minute^?1 for BICO, 18–220 mL kg^?1 minute^?1 for NICO, and – 35–32 mL kg^–1 minute^–1 for TEECO. Differences were maximum at the highest CO in BICO and NICO. In conclusion, this study demonstrated that BICO and NICO underestimate CO in sevoflurane anesthetized dogs. TEECO is a viable noninvasive method for determining CO in sevoflurane anesthetized dogs.     

牛磺酸对大鼠体内抗氧化系统的影响研究

观察牛磺酸（Taurine）对大鼠抗氧化酶系统的影响。给试验大鼠每日灌服牛磺酸，3周后处死，测定血清和肝匀浆的超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性、谷胱甘肽过氧化物酶（GSH-Px）活力、总抗氧化能力（T-AOC）、丙二醛（MDA）及还原型谷胱甘肽（GSH）含量。结果表明各牛磺酸给药组的大鼠血清和肝组织的SOD活性、GSH—PX活力及T-AOC上升，MDA含量降低，与空白组相比，差异显著（P〈0．05）。牛磺酸可以提高大鼠机体的抗氧化能力，抑制脂质过氧化。