Thermodilution cardiac output determination in the guinea pig

Thermodilution cardiac output was compared with simultaneously determined aortic flow in 5 guinea pigs during thoracotomy. Total cardiac output was affected by volume expansion, adrenergic stimulation, and the volume of hemorrhage. For the equation y = mx, where y is aortic flow, x is thermodilution cardiac output, and m is the slope of the regression line, m = 0.88 +/- 0.02 (95% confidence interval). The SE of the regression was 27.8 ml/min. Thermodilution may have been overestimated because the aortic flow measurement did not take into account the coronary arterial blood flow, which is approximately 4% of total cardiac output in the guinea pig. Indicator loss (ie, temperature) also may be an important factor in the calculation of cardiac output, as determinations of thermodilution cardiac output were affected by sampling site in the guinea pig. Thermodilution appears to be a useful and reliable means of determining cardiac output in the guinea pig.     

Accuracy of thermodilution measurement of cardiac output in low flows applicable to feline and small canine patients.

A model system of feline or small canine cardiac output was used to produce known liquid flow rates in the range of 100 to 750 mL/min for comparison against a thermodilution technique of flow measurement. Thermal indicator size was decided by the thermal time concentration curve detected by the Edwards 9520A cardiac output computer. Ten consecutive readings for each flow were made. Regression analysis and Student's t-test were used to evaluate the results. The computer was found to give good correlation with the accurate flow measured by a graduated cylinder over a period of time (r = 0.99). An error of less than 7% overestimation of flow by thermodilution was found with flows greater than 200 mL/min (p less than 0.05). A significant error of more than 20% overestimation of the actual flow occurred with flows less than 200 mL/min (p less than 0.05). The Edwards 9520A computer was compared to the older Edwards 9510A model by averaged triplicate measurements at six different cardiac outputs in an anesthetized cat. The measurements were not significantly different (p less than 0.01). Thermodilution using an Edwards computer proves to be a promising tool in the measurement of low flows applicable to feline and small canine cardiac outputs.     

Comparison of three methods for cardiac output determination in cats

Cardiac output (CO) was measured in sodium pentobarbital-anesthetized cats over a wide range of blood flow rates. In 10 cats, CO was measured simultaneously, using Fick determination and thermodilution techniques. Echocardiography was used to estimate contractility of the heart by measuring percentage change in minor diameter and velocity of circumferential fiber shortening. These indices were compared with CO by the other techniques. Echocardiographic equations used for CO determination in man were evaluated for reliability in the cat. Thermodilution and Fick determination correlated best with low CO (r = 0.89) and less with intermediate (r = 0.69) and high (r = 0.75) CO. Percentage change in minor diameter and velocity of circumferential fiber shortening correlated with thermodilution measurements of the cardiac index (r = 0.71 and r = 0.84, respectively). The value of echocardiography for CO estimation was questionable, using existing equations. Fick determination of CO was more inconsistent and was more prone to technical error than was thermodilution.     

Rate of change of oxygen concentration for a large animal circle anesthetic system

OBJECTIVE: To describe the effects of changes in circuit volume and oxygen inflow rate on inspired oxygen concentration for a large animal circle anesthetic system. STUDY POPULATION: A large animal circle anesthetic system, a 10 L/min flowmeter, and 20- and 40-L breathing bags. PROCEDURE: Circuit volume was determined by a carbon dioxide dilution technique. Oxygen flow rates of 3, 6, and 10 L/min were delivered to the circuit with the large breathing bag, and a flow rate of 6 L/min was used with the small bag. Gas samples were collected during a 20-minute period. The time constant (tau) and half-time (T1/2) were calculated and compared with measured values. RESULTS: Mean +/- SEM volume of the breathing circuit with a 20- and 40-L breathing bag was 32.97 +/- 0.91 L and 49.26 +/- 0.58 L, respectively. The tau from measurements was 11.97, 6.10, and 3.60 minutes at oxygen flow rates of 3, 6, and 10 L/min, respectively, for the large breathing bag and 3.73 minutes at a flow rate of 6 L/min for the small breathing bag. The T1/2 was 8.29, 4.22, and 2.49 minutes at oxygen flow rates of 3, 6, and 10 L/min, respectively, for the large breathing bag and 2.58 minutes for the small breathing bag. CONCLUSIONS AND CLINICAL RELEVANCE: This study emphasizes that there are delays in the rate of increase in the inspired oxygen concentration that accompany use of conventional large animal circle anesthetic systems and low rates of inflow for fresh oxygen.     

Clearance of para-aminohippuric acid in wethers consuming locoweed

AIM: To validate the use of para-aminohippuric acid (PAH) as a marker for measuring blood flow in wethers consuming a mixed diet of locoweed and blue grama hay.

METHODS: Fourteen sheep, stratified by bodyweight (BW), were assigned to one of three treatments: 0.8 mg swainsonine (SW)/kg BW (HI), 0.2 mg SW/kg BW (LO), and no SW (Control). Sheep were fed various ratios of locoweed and blue grama hay to deliver SW treatments, for 28 days prior to infusion of PAH. Concentrations of SW and activities of alkaline phosphatase (Alk-P) and aspartate aminotransferase (AST) in serum were measured to confirm exposure to SW and subclinical intoxication. A single 20-ml injection of 5% PAH was delivered into the jugular vein after subclinical intoxication had been achieved. Blood samples were collected and serum analysed for PAH immediately prior to injection, then every 5 min from 5–30 min, and every 10 min from 30–60 min, following injection of PAH.

RESULTS: Effective delivery of SW was evident from the greater concentrations of SW measured in the serum of HI compared with LO animals (p<0.05). No significant differences were detected in the rate of elimination (range 0.097–0.108 L/min), elimination half-life (range 6.62–7.24 min), apparent volume of distribution for the central compartment (range 7.14–9.72 L), and clearance (range 0.73–0.92 L/min) of PAH, between treatments.

CONCLUSIONS: Subclinical intoxication with SW did not affect the pharmacokinetics of PAH. Thus, use of downstream dilution of PAH is a valid method to determine the rate of blood flow in nutrient flux experiments that involve consumption of locoweed.     

Overberg Research Project. IX. First stage larvae per gram [L1p.g.] of faeces; an efficient method of diagnosing nematode parasites of sheep ante mortem

Nematode eggs were collected by mixing the faeces with a sugar solution, filling a flat-sided medicine bottle (100 ml), and allowing eggs to float and adhere to the upper surface for 30 min. After discarding the faeces, eggs hatched within 24 h at 20-30 degrees C. Each genus was counted in a counting chamber and the L1p.g. estimated. The morphology of L1 of Haemonchus, Teladorsagia, Trichostrongylus, Oesophagostomum and Strongyloides is briefly described.     

Effects of human pancreatic and rat hypothalamic growth hormone-releasing factors on growth hormone secretion in steers

Potencies of human pancreatic growth hormone-releasing factor [hpGRF(1–40)-OH] and of a peptide corresponding to the N-terminal 29 residues of rat hypothalamic GRF, [rGRF(1–29)-NH₂] were compared in two experiments. Eight Angus steers averaging 297 days of age and 290 kg in February 1984 were used in Exp. 1. Five months later six of the steers, weighing 391 kg, were used in Exp. 2.In Exp. 1, hpGRF(1–40)-OH and rGRF(1–29)-NH₂ were infused for 5 min at rates of 0, 1.3, 2.6, 5.2, 7.8 and 13.3 pmol/min/kg. Two steers were infused simultaneously, one received hpGRF(1–40)-OH and the other the equivalent dose of rGRF(1–29)-NH₂. Four pairs of steers received each dose. Both peptides elicited rapid GH release. Plasma GH concentrations peaked 15 to 20 min following onset of GRF administration, and returned to baseline levels 60 to 90 min later. Minimum effective doses, the lowest dose tested that resulted in a statistically significant GH reponse, were 5.2 pmol/min/kg hpGRF(1–40)-OH and 13.3 pmol/min/kg rGRF(1–29)-NH₂. Magnitudes of GH responses to 5.2, 7.8 and 13.3 pmol/min/kg hpGRF(1–40)-OH and 13.3 pmol/min/kg rGRF(1–29)-NH₂ were similar; corresponding to respective peak concentrations of 79, 66, 57 and 56 ng/ml. Growth hormone levels before GRF administration averaged 16 ng/ml.Experiment two was designed like the first except steers were infused for 6 hr with hpGRF(1–40)-OH and rGRF(1–29)-NH₂ at rates of 0, .5 and 1 pmol/min/kg. Both peptides at both rates raised (P<.05) GH concentrations during the 6 hr infusion period. Mean GH levels were 7 ng/ml during saline infusion, 30 and 23 ng/ml during infusion of .5 pmol/min/kg hpGRF(1–40)-OH and rGRF(1–29)-NH₂, and 41 and 27 ng/ml during infusion of 1 pmol/min/kg of the respective peptides. The initial GH response was biphasic, after which GH levels decreased temporarily and then one or two more GH surges occurred during the latter portion of the infusion period. Results demonstrate that hpGRF(1–40)-OH and rGRF(1–29)-NH₂ are potent GH secretagogues in steers. Potency of rGRF(1–29)-NH₂ is about 40% of hpGRF(1–40)-OH. Intrinsic activities, their ability to stimulate maximum GH secretion, appear to be similar. Both peptides are effective in raising GH levels over a 6 hr constant infusion period.     

Evaluation of isoflurane and sevoflurane vaporizers over a wide range of oxygen flow rates

OBJECTIVE: To examine the accuracy and precision of isoflurane and sevoflurane anesthetic vaporizers. SAMPLE POPULATION: 5 identical isoflurane and 5 identical sevoflurane vaporizers. PROCEDURES: Oxygen flow rates from 0.02 to 10 L/min were used with different vaporizer dial settings. Agent concentrations were measured at the common gas outlet by use of a refractometer. Accuracy was defined as the difference between measured agent concentrations, and dial settings were expressed as a percentage of the applied dial settings. Precision was defined as SD of the measured agent concentrations for each combination of dial setting and flow. RESULTS: Isoflurane values were generally greater than the dial settings. Accuracy of the isoflurane vaporizer was > 20% when 0.6% and 1% was dialed. Accuracy of the sevoflurane vaporizer was always within +/- 20% but decreased at 0.02 L/min flow and at combinations of high flow and high dial settings. Overall precision of the isoflurane vaporizer was better than that of the sevoflurane vaporizer. CONCLUSIONS AND CLINICAL RELEVANCE: A possible explanation for the inaccuracy of the isoflurane vaporizer may be that it was manufactured to be accurate with air but not oxygen, which must be accounted for when using the vaporizer with oxygen, especially with nonrebreathing systems. The sevoflurane vaporizer may not deliver accurate agent concentrations at high flow and high dial settings. Both vaporizers are suitable for clinical use with a wide range of oxygen flow rates if these precautions are properly addressed.     

小鼠卵母细胞氯化锶激活条件

以昆明小鼠为试验对象，研究了氯化锶（SrCl2)浓度，激尖处理时间以及卵龄对卵母细胞SrCl2孤雌活化的影响。hCG注射后18h的小鼠卵母细胞在1.6,5.0,10,20mmol/L SrCl2的激活液中处理10min，各组间的激活率（原核期卵母细胞的比例）无显著性差异（P＞0．05）。10，20mmol/L SrCl2组发育至2－，4－细胞期比率（59．26％，20．37％，63．79％，20．69％）同于1．6，5．0mmol/L 组（20．63％，9．26％，47．06％，7．84）（P＜05）。只有20mmol/L组的少数激活卵母细胞（3．45％）发育至桑椹胚阶段。10，20mmol/L SrCl2组处理20，40，60min，2组间的活化率无显著性差异。处理40min,20mmol/L组的桑椹胚和囊胚发育率（64．44％，22．22％）均显著高于10mmol/L组（30．36％，11．61％），处理60min,10mmol/L组的桑椹胚和囊胚发育率（84．68％，46．77％）均显著高于20mmol/L组（67．46％，28．57％），10mmol/L SrCl2处理，20，40，60，180，360min，其活化率和2－细胞的发育率无显著性差异。60，180min处理组的囊胚发育率（49．58％，47．59％）差异不显著，但2者均显著高于20，40，360min组（4．50％，12．24％和35．53％），后3者组间差异显著。随卵龄的增加，活化率显著增加。hCG注射后16h卵母细胞的活化率（77．78％）显著高于14h的卵母细胞（29．63％），而hCG注射后18h卵母细胞的活化率（49．19％）又显著高于16h的卵母细胞，hCG注射后18，20h卵母细胞的活化率差异不显著（94．19％，85．90％）。hCG注射后14，16，18h卵母细胞激活后的囊胚发育率（6．71％，27．78％，47．67％），各组间差异显著。但hCG注射后20h卵母细胞激活后的囊胚发育率（39．74％）显著低于18h的卵母细胞。     

Pharmacokinetics of single-dose administration of moxalactam in unweaned calves

Twenty-nine healthy 17- to 29-day-old unweaned Israeli-Friesian male calves were each given a single IV or IM injection of 10 or 20 mg of moxalactam disodium/kg of body weight. Serum concentrations were measured serially during a 12-hour period. Serum concentration vs time profiles were analyzed by use of linear least-squares regression analysis and the statistical moment theory. The elimination half-lives after IV administration were 143.7 +/- 30.2 minutes and 155.5 +/- 10.5 minutes (harmonic mean +/- SD) at dosages of 10 and 20 mg of moxalactam/kg of body weight, respectively. Corresponding mean residence time values were 153.1 +/- 26.8 minutes and 169.9 +/- 19.3 minutes (arithmetic mean +/- SD). Mean residence time values after IM administration were 200.4 +/- 17.5 minutes and 198.4 +/- 19.9 minutes at dosages of 10 and 20 mg/kg, respectively. The volumes of distribution at steady state were 0.285 +/- 0.073 L/kg and 0.313 +/- 0.020 L/kg and total body clearance values were 1.96 +/- 0.69 ml/min/kg and 1.86 +/- 0.18 ml/min/kg after administration of dosages of 10 and 20 mg/kg, respectively. Moxalactam was rapidly absorbed from the IM injection site and peak serum concentrations occurred at 1 hour. The estimated bioavailability ranged from 69.8 to 79.1%. The amount of serum protein binding was 53.4, 55.0, and 61.5% when a concentration of moxalactam was at 50, 10, and 2 micrograms/ml, respectively. The minimal inhibitory concentrations of moxalactam ranged from 0.01 to 0.2 micrograms/ml against Salmonella and Escherichia coli strains and from 0.005 to 6.25 micrograms/ml against Pasteurella multocida strains.     

DISPERSAL PATTERN OF INJECTATE FOLLOWING CT‐GUIDED PERINEURAL INFILTRATION IN THE CANINE THORACOLUMBAR SPINE: A CADAVER STUDY

An increasing proportion of canine patients are presented with chronic thoracolumbar back pain and without compressive spinal lesions. In humans, spinal perineural infiltrations have been reported to have a favorable effect on pain control. The purpose of this prospective cadaver study was to describe the dispersal pattern of injectate following CT‐guided spinal perineural infiltration in the canine thoracolumbar region. Seven fresh canine cadavers were first scanned using multislice CT and then CT‐guided spinal perineural infiltration was performed at 42 sites from T13/L1 to L6/L7. The injectate for each site was a mixture of new methylene blue and iodinated contrast medium. Immediately following CT‐guided injection, cadavers were frozen, cut, and dissected macro‐ and mesoscopically (using a magnifying glass) to identify anatomic structures that were infiltrated. In the majority of sites (64.3%), complete epidural and hypaxial staining of spinal nerve components (including the spinal ganglion, trunk, and ventral branch) was successfully achieved. However, no (11.9%) or unpredictable staining (9.5%) of nervous tissue occurred in some sites despite careful CT guidance and the application of relatively large volumes of injectate. Optimal results were achieved when the needle tip was positioned periforaminally ventral to the cranial contour of the cranial articular process. Findings from this ex vivo study indicated that CT‐guided spinal perineural infiltration is feasible for testing in the canine thoracolumbar region and that successful nerve tissue infiltration would likely occur in the majority of sites. Future in vivo studies are needed to determine the safety and efficacy of this technique.     

Ultrasound-guided rectus sheath block injections in miniature swine cadavers: technique description and distribution of two injectate volumes

ObjectiveTo describe a technique for ultrasound-guided rectus sheath block in pigs and the distribution of two injectate volumes.Study designExperimental study.AnimalsA group of 11 Hanford miniature pig cadavers.MethodsThe lateral border of each rectus abdominis muscle in 10 freshly euthanized pigs was visualized with a 6-15 MHz linear ultrasound probe. A spinal needle was inserted 1 cm cranial to the umbilicus, in-plane and medial to the probe, and advanced dorsal to lateral until the tip was ventral to the internal rectus sheath. Pigs were injected bilaterally with high volume (treatment HV; 0.8 mL kg^–1) or low volume (treatment LV; 0.5 mL kg^–1) of 1:1 solution of 1% methylene blue and 0.5% bupivacaine (1 mg kg^–1) diluted with 0.9% saline. Nerve staining ≥ 1 cm circumferentially was determined by dissection 15 minutes postinjection. The Clopper–Pearson method was used to calculate 95% confidence intervals (CIs) for proportions of stained nerves. In another pig, a 1:1 solution of 1% methylene blue and 74% ioversol contrast was injected, and computed tomography performed at 15 minute intervals after injection.ResultsNerve staining for thoracic (T) spinal nerves T9, T10, T11, T12, T13 and T14 occurred 20%, 60%, 90% 100%, 100% and 50%, and 0%, 20%, 90%, 100%, 100% and 50% of the time in treatments HV and LV, respectively. More nerves were stained in treatment HV in 4/10 animals (40%, 95% CI: 12%–74%) than in treatment LV (0%, 95% CI: 0%–31%). The greatest spread of injectate occurred within the first 15 minutes after injection.Conclusions and clinical relevanceStaining of T11–T14 nerves was the same in both treatments but the higher volume stained more T9–T10 nerves. Based on dye distribution, a rectus sheath block may only provide ventral abdominal analgesia cranial to the umbilicus in pigs.     

Disinfection of the causative agent of contagious equine metritis by Nolvasan and Roccal II

Haemophilus equigenitalis, the proposed name for the bacterium that causes contaginous equine metritis (CEM) was tested for sensitivity to the disinfectant solutions Nolvasan® (2% chlorhexidine diacetate) and Roccal II® (10 alkyldimethylbenzylammonium chloride).Bacteria (10⁶) suspended in medium were inactivated in 10–20 min at 0°–2°C and in 2.5 min at 20°–22°C by a 3 : 128 dilution of Nolvasan. Roccal II, diluted 1 : 128, inactivated 10⁶ bacteria in 2.5 min at 0°–2°C and 20°–22°C.These dilutions of the disinfectants inactivated H. equigenitalis (titers of 0.1–11.0 × 10⁷/ml) in vaginal exudates from infected mares and pure cultures suspended in medium (titers of 1–5 × 10⁹/ml) in 10 min at 0°–2°C and 20°–22°C when the exudates and cultures were dried on metal carriers. The limit of detection of survivors was 3–32 bacteria/ml.It is recommended that contaminated instruments and other metal surfaces encountered during CEM infections should be decontaminated with either disinfectant for 10 min before rinsing.     

Evaluation of a minimally invasive non-calibrated pulse contour cardiac output monitor (FloTrac/Vigileo) in anaesthetized dogs

ObjectiveTo evaluate the accuracy of a new cardiac output monitor (FloTrac/Vigileo), originally designed for humans, in dogs. This pulse contour cardiac output monitoring system cannot be calibrated and measures cardiac output (

t) from a standard arterial catheter.Study designProspective experimental trial.AnimalsEight adult Beagle dogs weighing 13.1 (9.8–17.1) kg [median (range)].MethodsAnaesthesia in the dogs was maintained using isoflurane. A pulmonary artery catheter and a metatarsal arterial catheter (22 gauge) were placed. Cardiac output was measured simultaneously 331 times by thermodilution and FloTrac technique. A broad spectrum of

t measurements was achieved through alterations of isoflurane concentration, administration of propofol boluses and dobutamine infusions. Agreement between the methods was quantified with Bland Altman analysis and disagreement was assessed with linear mixed models.ResultsMedian (10th and 90th percentile) cardiac output as measured with thermodilution was 2.54 (1.47 and 5.15) L minute^?1 and as measured with FloTrac 8.6 (3.9 and 17.3) L minute^?1. FloTrac measurements were consistently higher with a mean bias of 7 L minute^?1 and limits of agreement of ?3.15 to 17.17 L minute^?1. Difference between the methods was most pronounced in high

t measurements. Linear mixed models showed an estimated difference between the two methods of 8.05 (standard error 1.18) L minute^?1 and a significant interaction between mean arterial pressure and method. Standard deviation (4.45 higher) with the FloTrac method compared to thermodilution was increased.ConclusionCompared to thermodilution measurements, the FloTrac system was influenced to a higher degree by arterial blood pressure, resulting in consistent overestimation of cardiac output.Clinical RelevanceThe FloTrac monitor, whose algorithms were developed based on human data, cannot be used as an alternative for thermodilution in dogs.     

Precorneal retention time of ocular lubricants measured with fluorophotometry in healthy dogs

Objective

Determine the precorneal retention time of five different ocular lubricants commonly used in dogs.

Animals Studied

Six healthy Beagle dogs (n = 12 eyes).

Procedures

Five ocular lubricants were studied: Artificial Tears Solution® (1.4% polyvinyl alcohol), I-Drop® Vet Plus (0.25% hyaluronate), Optixcare® Eye Lube Plus (0.25% hyaluronate), Systane® Ultra (0.4% polyethylene glycol 400 and 0.3% propylene glycol), and Artificial Tears Ointment® (mineral oil/white petrolatum). Each lubricant was mixed with 10% sodium fluorescein to achieve 1% fluorescein formulations. Following topical administration of 35 mg in each eye, tear fluid was collected with capillary tubes at selected times (0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 180 min) and fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer.

Results

Tear fluorescence was significantly greater with Artificial Tears Ointment® compared with other lubricant formulations from 1 to 20 min post-administration. Median (range) precorneal retention times were significantly different among the 5 lubricants, ranging from 40 minutes (20–90 min) for Artificial Tears Ointment®, 35 min (20–90 min) for Systane® Ultra, 30 min (10–60 min) for I-Drop® Vet Plus, 25 min (10–60 min) for Optixcare® Eye Lube Plus, and 10 min (10–20 min) for Artificial Tears Solution®. Precorneal retention time was significantly lower for Artificial Tears Solution® compared with the other 4 formulations.

Conclusions

This study established normative data for the retention time of common lubricants on the ocular surface of dogs, which may be used to guide clinicians with their choice of lubricant and frequency of administration.     

Effects of hypothyroidism on the skeletal muscle blood flow response to contractions

Hypothyroidism is associated with impaired blood flow to skeletal muscle under whole body exercise conditions. It is unclear whether poor cardiac and/or vascular function account for blunted muscle blood flow. Our experiment isolated a small group of hindlimb muscles and simulated exercise via tetanic contractions. We hypothesized that muscle blood flow would be attenuated in hypothyroid rats (HYPO) compared with euthyroid rats (EUT). Rats were made hypothyroid by mixing propylthiouracil in their drinking water (2.35 x 10-3 mol/l). Treatment efficacy was evidenced by lower serum T3 concentrations and resting heart rates in HYPO (both P<0.05). In the experimental preparation, isometric contractions of the lower right hindlimb muscles at a rate of 30 tetani/min were induced via sciatic nerve stimulation. Regional blood flows were determined by the radiolabelled microsphere method at three time points: rest, 2 min of contractions and 10 min of contractions. Muscle blood flow generally increased from rest ( approximately 5-10 ml/min per 100 g) through contractions for both groups. Further, blood flow during contractions did not differ between groups for any muscle (eg. red section of gastrocnemius muscle; EUT, 59.9 +/- 14.1; HYPO, 61.1 +/- 15.0; NS between groups). These findings indicate that hypothyroidism does not significantly impair skeletal muscle blood flow when only a small muscle mass is contracting. Our findings suggest that impaired blood flow under whole body exercise is accounted for by inadequate cardiac function rather than abnormal vascular function.     

Pharmacokinetics of midazolam administered concurrently with ketamine after intravenous bolus or infusion in dogs

Brown, S.A., Jacobson, J.D., Hartsfield, S.M. Pharmacokinetics of midazolam administered concurrently with ketamine after intravenous bolus or infusion in dogs. J. vet. Pharmacol. Therap. 16 , 419–425. Midazolam, a water-soluble benzodiazepine tranquilizer, has been considered by some veterinary anaesthesiologists to be suitable as a combination anaesthetic agent when administered concurrently with ketamine because of its water solubility and miscibility with ketamine. However, the pharmacokinetics of midazolam have not been extensively described in the dog. Twelve clinically healthy mixed breed dogs (22.2–33.4 kg) were divided into two groups at random and were administered ketamine (10 mg/kg) and midazolam (0.5 mg/kg) either as an intravenous bolus over 30 s (group 1) or as an i.v. infusion in 0.9% NaCl (2 ml/kg) over 15 min. Blood samples were obtained immediately before the drugs were injected and periodically for 6 h afterwards. Serum concentrations were determined using gas chromatography with electron-capture detection. Serum concentrations were best described using a two-compartment open model and indicated a t_½α of 1.8 min and t_½β.p of 27.8 min after i.v. bolus, and t_½α f 1–35 min and t_½β of 31.6 min after i.v. infusion. The calculated pharmacokinetic coefficient B was significantly smaller after i.v. infusion (429 ± 244 ng/ml) than after i.v. bolus (888 ± 130 ng/ml, P = 0.004). Furthermore, AUC was significantly smaller after i.v. infusion (29 800 ±6120 ng/h/ml) than after i.v. bolus (42 500 ± 8460 ng/h/ml, P < 0.05), resulting in a larger Cl_B after i.v. infusion (17.4 ± 4.00 ml/min/kg than after i.v. bolus (12.1 ± 2.24 ml/min/kg, P < 0.05). No other pharmacokinetic value was significantly affected by rate of intravenous administration.     

Assessment of lithium dilution cardiac output as a technique for measurement of cardiac output in dogs

OBJECTIVES: To determine agreement of cardiac output measured by use of lithium dilution cardiac output (LiDCO) and thermodilution cardiac output (TDCO) techniques in dogs and to determine agreement of low- and high-dose LiDCO with TDCO. ANIMALS: 10 dogs (7 males, 3 females). PROCEDURE: Cardiac output was measured in anesthetized dogs by use of LiDCO and TDCO techniques. Four rates of cardiac output were induced by occlusion of the caudal vena cava, changes in depth of anesthesia, or administration of dobutamine. Lithium dilution cardiac output was performed, using 2 doses of lithium chloride (low and high dose). Each rate of cardiac output allowed 4 comparisons between LiDCO and TDCO. RESULTS: 160 comparisons were determined of which 68 were excluded. The remaining 92 comparisons had values ranging from 1.10 to 12.80 L/min. Intraclass correlation coefficient (ICC) between low-dose LiDCO and TDCO was 0.9898 and between high-dose LiDCO and TDCO was 0.9896. When all LiDCO determinations were pooled, ICC was 0.9894. For determinations of cardiac output < 5.0 L/min, ICC was 0.9730. Mean +/- SD of the differences of TDCO minus LiDCO for all measurements was -0.084+/-0.465 L/min, and mean of TDCO minus LiDCO for cardiac outputs < 5.0 L/min was -0.002+/-0.245 L/min. CONCLUSIONS AND CLINICAL RELEVANCE: The LiDCO technique is a suitable substitute for TDCO to measure cardiac output in dogs. Use of LiDCO eliminates the need for catheterization of a pulmonary artery and could increase use of cardiac output monitoring, which may improve management of cardiovascularly unstable animals.     

Drug Efficacy of Terbinafine Hydrochloride (Lamisil®) During Oral Treatment of Cats,Experimentally Infected with Microsporum canis

Cats represent a primary source of Microsporum canis infections in humans. Terbinafine hydrochloride (Lamisil^®) is commonly used in the treatment of microsporosis in humans as its fungicidal action permits short periods of treatment. The aim of the present study was to estimate the efficacy of the drug in cats. Nine cats were experimentally infected with M. canis and treated with terbinafine hydrochloride at a dose of 10–20 mg/kg (once daily, SID; low‐dose group, LDG). Another nine cats were similarly infected and treated with 30–40 mg/kg SID (high‐dose group, HDG) and a further nine cats were also infected and left untreated (control group, CG). The general condition of the cats was observed daily and their clinical symptoms evaluated weekly. The cats recovery was monitored using the Wood's lamp illumination test and microscopic and fungal culture examinations. The general condition of the cats during the study was good. The cure rates of the LDG were not significantly different from the CG at any period during the treatment. However, the HDG cure rates differed significantly from the other two groups. After 109 days of treatment, when all nine cats of the HDG were healed, seven cats of the LDG and all the cats in the CG were still M. canis‐positive. This study shows that dosages of 10–20 mg/kg SID of terbinafine hydrochloride are not sufficient to terminate an experimental M. canis infection in cats within an acceptable period of time. Terbinafine hydrochloride can be used to treat dermatophytosis in cats, but a higher dosage, 30–40 mg/kg SID, should be used to achieve a cure.     

The Minimum Alveolar Concentration of Desflurane in Cats

Eight adult cats, 4 male and 4 female, (3.5 ± 0.9 [SD] kg) were used to determine the minimum alveolar concentration (MAC) of desflurane. Desflurane (DES) anesthesia was induced in a 20 L chamber with an oxygen inflow of 10 L/min and the DES vaporizer set at 18%. After 3.5 ± 0.5 min, the cats were removed from the chamber and anesthesia was maintained via mask (14% DES, 3L/min O₂) until successful intubation. Anesthesia was maintained with DES in oxygen at a flow of at least 200 mL/kg/min through a nonrebreathing circuit. The time from the start of induction to completion of intubation was 6.2 ± 1.1 min. Esophageal temperature was maintained between 37.8°C and 38.6°C. Hand-collected end-tidal gas samples were obtained from a catheter positioned inside the lumen of the endotracheal tube. Inspired and end-tidal DES concentrations were measured with a Biochem 8100 anesthetic agent monitor that was calibrated with known gas standards and modified to accept hand-collected samples. A constant alveolar concentration of DES was maintained for at least 15 minutes, then a clamp was applied to the tail and the cat observed for gross purposeful movement. The end-tidal DES was then increased (if a positive response) or decreased (if a negative response) by 20% and the test repeated after 15 minutes of constant conditions. The final iteration was 10%. The MAC of DES in these cats was 9.79 ± 0.70 vol %. The F_A/F_I ratio for desflurane was always greater than 0.97.