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.     

Resistance to gentamicin and amikacin of gram-negative organisms isolated from horses

Resistance of gram-negative bacteria to gentamicin has become an increasingly common problem among clinical isolates from human beings. Susceptibility of isolates from horses to gentamicin and amikacin was evaluated for the period from July, 1983 to June, 1985. All isolates of Escherichia coli, and species of Enterobacter, Klebsiella, Proteus, and Pseudomonas examined were susceptible to amikacin, except 2 of the 46 Pseudomonas isolates. In contrast, 13 to 50% of isolates were resistant to gentamicin. Escherichia coli, and Klebsiella, Proteus, and Enterobacter species isolates were highly significantly more susceptible to amikacin (P less than 0.01) than to gentamicin. Pseudomonas spp (P = 0.13) were not significantly different in susceptibility to the 2 drugs. There was significant variation among genera in their susceptibility to gentamicin (P = 0.002), primarily because of the frequency of resistance in isolates of Klebsiella spp and Proteus spp, compared with the other 3 organisms (E coli, Enterobacter spp, and Pseudomonas spp). There was no significant difference of susceptibility to amikacin among the genera studied (P = 0.06).     

Sources of tolerance to low soil nitrogen in some Striga resistant and quality protein maize (Zea mays L.) varieties

Journal of Crop Science and Biotechnology - Low soil nitrogen (N) is one of the major abiotic stresses reducing maize yield in Africa. Twenty-five maize varieties which included quality protein...     

The role of food consumption factors in establishing drug tolerances

The Center for Veterinary Medicine's food consumption policy was adopted in 1978 before suitable data were available on the consumption of organ meats. Consumption is expressed in terms of amounts expected to be consumed daily by an adult human. Before the Center for Veterinary Medicine (Center) can choose a suitable database to develop a new guideline, the Center must resolve a number of difficult policy choices. After the policy issues are resolved, the Center could use the 1977-78 USDA National Food Consumption survey or an approach based on carcass yield to develop the new guideline.     

Hemodynamic effects of ionized calcium in horses anesthetized with halothane or isoflurane

OBJECTIVES: To evaluate the effects of halothane and isoflurane on cardiovascular function and serum total and ionized calcium concentrations in horses, and to determine whether administration of calcium gluconate would attenuate these effects. ANIMALS: 6 clinically normal adult Thoroughbreds. PROCEDURE: Catheters were inserted for measurement of arterial blood pressures, pulmonary arterial blood pressures, right ventricular pressure (for determination of myocardial contractility), right atrial pressure, and cardiac output and for collection of arterial blood samples. Anesthesia was then induced with xylazine hydrochloride and ketamine hydrochloride and maintained with halothane or isoflurane. An i.v. infusion of calcium gluconate was begun 75 minutes after anesthetic induction; dosage of calcium gluconate was 0.1 mg/kg of body weight/min for the first 15 minutes, 0.2 mg/kg/min for the next 15 minutes, and 0.4 mg/kg/min for an additional 15 minutes. Data were collected before, during, and after administration of calcium gluconate. RESULTS: Halothane and isoflurane decreased myocardial contractility, cardiac index, and mean arterial pressure, but halothane caused greater depression than isoflurane. Calcium gluconate attenuated the anesthetic-induced depression in cardiac index, stroke index, and maximal rate of increase in right ventricular pressure when horses were anesthetized with isoflurane. When horses were anesthetized with halothane, a higher dosage of calcium gluconate was required to attenuate the depression in stroke index and maximal rate of increase in right ventricular pressure; cardiac index was not changed with calcium administration. CONCLUSIONS AND CLINICAL RELEVANCE: I.v. administration of calcium gluconate may support myocardial function in horses anesthetized with isoflurane.     

THE PATH OF CARBON IN PHOTOSYNTHESIS. XXIX. GLASS MICROBEADS

Glass microbeads are introduced as convenient and applicable mechanical supports for hydroponics that can be released from roots to exhibit visually discernible responses. Moreover, glass microbeads refract light, effectively redistributing light toward the phylloplane. The smallest beads, <300 μm diameter, rose from neutral to ～pH 9 in water and the rise was attributable the raw materials source, sodalime glass. The largest 700 μm diameter beads were relatively stable in buffered nutrients. Photography of unobstructed roots was aided by release of microbeads from ryegrass, coleus, corn, and narcissus. Propagation of ‘Ninsei’ was undertaken in containers constructed with inflow and drainage ports. Photodocumentation of responses to indoxylglucopyranoside exhibited consistent differences as compared to controls when cultured in glass microbeads; and further investigations into increased light intensity by refraction may lead to enhanced photosynthetic efficiency.     

The Path of Carbon in Photosynthesis. XXV. Plant and Algal Growth Responses to Glycopyranosides

Substituted glycopyranosides were applied to various plant species as foliar and root treatments, with and without nutrient supplements, and growth was compared to untreated or nutrient controls. When formulated with specific fertilizers, particularly available nitrogen, methyl and ethyl glycopyranosides significantly enhanced the overall growth of vascular plants compared to controls provided with the same nutrients. In contrast, vascular plants treated with alkylglycopyranosides without nutrients showed growth equivalent to that of untreated controls. Nitrogen-supplemented alkylglycopyranosides provided as foliar applications of 100 mM, or as root treatments between 35 and 50 mM, consistently enhanced root and shoot productivity. In addition to the vascular plant species tested, the brown alga Laminaria saccharina exhibited significant growth enhancement over nutrient controls when treated with alkylglycopyranosides supplemented with nutrients, especially under low irradiance. Overall, these results indicate that growth of photosynthetic organisms is enhanced by exogenous alkylglycopyranosides supplemented with nitrogen and micronutrients, but not by alkylglycopyranosides alone.     

Anesthetic potency of nitrous oxide in young swine (Sus scrofa)

Determination of nitrous oxide (N2O) potency was accomplished by extrapolation using the concepts of minimum alveolar concentration (MAC) and additivity among inhalation anesthetics. Halothane and isoflurane anesthetic requirement (alveolar concentration) necessary to achieve MAC in 9 pigs decreased with each successive increase in the percentage of inspired N2O (25%, 50%, 75%). Halothane and isoflurane MAC was determined to be 0.94 +/- 0.03 and 1.75 +/- 0.01 volumes percent, respectively. Halothane and isoflurane requirements decreased to 0.74 +/- 0.02, 0.66 +/- 0.02, and 0.58 +/- 0.02; and to 1.56 +/- 0.02, 1.38 +/- 0.02, and 1.08 +/- 0.03 volumes percent with 25%, 50%, and 75% N2O, respectively. The line of best fit derived from regression analysis of the combined data (isoflurane and halothane MAC values) had a correlation coefficient of 0.987 and an X intercept equivalent to 195% N2O. The potency of N2O in pigs was similar to that of other domesticated mammals and reduced halothane and isoflurane anesthetic requirements by approximately 50% of the reduction observed in human beings.