Effects of a medetomidine-midazolam-butorphanol combination on renal cortical, intestinal and muscle microvascular blood flow in isoflurane anaesthetized dogs: a laser Doppler study

Objective To obtain renal cortical, ileal, colonic and skeletal muscle microvascular blood flow measurements in dogs using the laser Doppler technique and to characterize the effects of medetomidine‐midazolam‐butorphanol combination on these flows. Study Design Prospective randomized experimental study. Animals Fourteen clinically normal beagles (two groups of seven), aged 1–4 years and weighing 13.2 ± 1.8 kg. Methods All dogs were anaesthetized with 1.7% end‐tidal isoflurane in oxygen. In the treatment group, after instrumentation and when anaesthesia was considered stable, medetomidine (1 mg m^?2 body surface area (BSA)) was administered intramuscularly (time 0). Midazolam (1 mg kg^?1) and butorphanol (0.1 mg kg^?1) were administered intravenously 20 minutes later. Atipamezole (2.5 mg m^?2 BSA) was administered intramuscularly 60 minutes after medetomidine. In the control group, saline (0.5, 2.5 and 0.25 mL) was administered at the corresponding times. Heart rate, systolic, diastolic and mean arterial pressures, body temperature, renal cortical, ileal, colonic and skeletal muscle microvascular blood flows were measured before time 0, and 5, 15, 25, 40, 60, 65, 70 and 90 minutes thereafter. Results Heart rate, ileal and skeletal muscle blood flows decreased in the treatment group, while no changes were observed in the control group. Conclusions Laser Doppler flowmetry allowed the measurement of microvascular blood flow in different organs. The medetomidine‐midazolam‐butorphanol combination decreases intestinal and skeletal muscle microvascular blood flows, while renal cortical blood flow is maintained. Clinical relevance Medetomidine‐midazolam‐butorphanol combination can be used to induce a short duration anaesthesia in dogs, but it will induce cardiovascular depression. This depression appears to be accompanied by a redistribution of blood flow.     

Sources of variation in splanchnic blood flow in steers

Data from six experiments were used to describe sources of variation in blood flow through portal-drained viscera and liver of 33 steers that were fed equal-sized meals every 2 h. The experiments were designed to create "steady-state" conditions under which response to various dietary or physiological treatments was assessed. Sums of squares for blood concentration of blood flow marker, venoarterial differences in blood flow marker, and blood flow were divided into variation attributable to steer; period (or time); the steer x period interaction; sampling days within steer and period; and replications (or samplings) within day, steer, and period. Steer was the largest single source of variation in arterial concentration of blood flow marker, accounting for from 42 to 80% of sums of squares among the experiments. However, replication within day, steer, and period accounted for more variation than steer in portal or hepatic blood flow in four of the six experiments. When balanced for treatment effects, steer accounted for 59%, period and the steer x period interaction accounted for 14%, and replication accounted for 27% of variation in portal blood flow. Corresponding percentages for hepatic blood flow were 45, 20, and 35%. I conclude that steer and replication within steer x period cells in a matrix of treatments are the two largest sources of variation and that there is more variation among samples on a given day within steer x period cells than among days in the same cells.     

Evaluation of aging on muscle blood flow in conscious healthy dogs by duplex Doppler ultrasonography

According to a study conducted on a population of 9,248 subjects, cardiac diseases are the second most prevalent cause of death in the dog. During the last decades, a common scenario has been the increase on life expectancy of dogs. The exact relationship between the negative modifications of cardiovascular function and the development of specific cardiovascular diseases is difficult to ascertain, and also, the effect of age per se on vascular impedance is important. It may result in limited cardiovascular reserve under conditions of increase demand in senescent animals. To evaluate the effect of age on the peripheral vasculature specifically, the objective of this study was to compare parameters of the regional blood flow as well as compliance and resistance indexes in the femoral arterial system of younger and older conscious healthy dogs by duplex Doppler ultrasonography. The data were collected from 16 mixed-breed dogs divided into two groups: young and old healthy dogs. In all dogs Doppler spectra blood flow patterns of the femoral artery were triphasic. Significant differences were not found between the parameters measured for young and old groups. Despite this, the average value of femoral flow volume in the older group was approximately 50% lower than the younger group. This finding could play an important role in limiting exercise response with age. In order to validate these speculations, further studies should be performed in aged dogs.     

Pulsed-wave Doppler evaluation of intracardiac blood flow in 30 clinically normal Standardbred horses

Pulsed-wave Doppler echocardiography was performed on 30 clinically normal 1- to 6-year-old racing Standardbreds. There were 13 females, 13 geldings, and 4 stallions. Cardiac disease was not detected with M-mode, 2-dimensional real-time or pulsed-wave Doppler echocardiography. Normal flow velocities for right and left atrial outflow, right and left ventricular outflow, the aorta, and pulmonary artery were determined. Peak flow velocities for right and left atrial outflow occurred during the rapid filling phase and were higher toward the mitral valve (mean, 0.70 +/- 0.24 m/s) than toward the tricuspid valve (mean, 0.49 +/- 0.17 m/s). Peak flow velocities in the right and left ventricular outflow tracts were similar (means, 0.81 +/- 0.10 m/s and 0.75 +/- 0.39 m/s, respectively). Peak flow velocities in the pulmonary artery (mean, 1.09 +/- 0.42 m/s) and aorta (mean, 1.01 +/- 0.29 m/s) were similar, although flow peaked earlier in systole in the aorta than in the pulmonary artery.     

Evaluation of laser Doppler flowmetry for measurement of capillary blood flow in the stomach wall of dogs during gastric dilatation-volvulus

OBJECTIVES: To validate laser doppler flowmetry (LDF) for measurement of blood flow in the stomach wall of dogs with gastric dilatation-volvulus (GDV). ANIMALS: Six purpose-bred dogs and 24 dogs with naturally occurring GDV. STUDY DESIGN: Experimental and clinical. METHODS: Capillary blood flow in the body of the stomach and pyloric antrum was measured with LDF (tissue perfusion unit (TPU) before and after induction of portal hypertension (PH) and after PH plus gastric ischemia (GI; PH + GI) and compared with flow measured by colored microsphere technique. Capillary flow was measured by LDF in the stomach wall of dogs with GDV. RESULTS: PH and PH+GI induced a significant reduction in blood flow in the body of the stomach (P = .019). A significant positive correlation was present between percent changes in capillary blood flow measured by LDF and colored microspheres after induction of PH + GI in the body of the stomach (r = 0.94, P = .014) and in the pyloric antrum (r = 0.95, P = .049). Capillary blood flow measured in the body of the stomach of 6 dogs that required partial gastrectomy (5.00+/-3.30 TPU) was significantly lower than in dogs that did not (28.00+/-14.40 TPU, P = .013). CONCLUSIONS: LDF can detect variations in blood flow in the stomach wall of dogs. CLINICAL RELEVANCE: LDF may have application for evaluation of stomach wall viability during surgery in dogs with GDV.     

Plasma and whole blood taurine in normal dogs of varying size fed commercially prepared food

The objective of the present study was to examine the effect of signalment, body size and diet on plasma taurine and whole blood taurine concentrations. A total of 131 normal dogs consuming commercially prepared dog food had blood drawn 3-5 h post-prandially to be analysed for plasma amino acids and whole blood taurine. Body weight and morphometric measurements of each dog were taken. Plasma and whole blood taurine concentrations were 77 +/- 2.1 nmol/ml (mean +/- SEM) and 266 +/- 5.1 nmol/ml (mean +/- SEM), respectively. No effect of age, sex, body weight, body size, or diet was seen on plasma and whole blood taurine concentrations. Mean whole blood taurine concentrations were lower in dogs fed diets containing whole grain rice, rice bran or barley. The lowest whole blood concentrations were seen in dogs fed lamb or lamb meal and rice diets. Plasma methionine and cysteine concentrations were lower in dogs fed diets with animal meals or turkey, and whole grain rice, rice bran or barley. Fifteen of 131 dogs had plasma taurine concentrations lower than, or equal, to the previously reported lowest mean food-deprived plasma taurine concentration in normal dogs of 49 +/- 5 nmol/ml (mean +/- SEM) (Elliott et al., 2000). These findings support the theory that taurine deficiency in dogs may be related to the consumption of certain dietary ingredients. Scientific and clinical evidence supports the hypothesis that dilated cardiomyopathy is associated with low blood taurine concentration in dogs; therefore, further work is indicated to determine the mechanism by which diet can affect taurine status in dogs.     

Pulsed Doppler ultrasonographic evaluation of portal blood flow in dogs with experimental portal vein branch ligation

Portal blood flow was measured using pulsed Doppler ultrasound in 6 dogs before and after left portal vein branch ligation. Mean portal vein blood flow velocity and mean portal vein blood flow were significantly reduced after ligation and the congestion index was increased (p < 0.01). Pulsed Doppler ultrasound studies provide valuable physiological information which may assist the clinician with the diagnosis of canine hepatic circulatory disorders.     

Assessment of renal blood flow in dogs: analysis of 131I-hippuran blood clearance in healthy dogs and in dogs with proteinuria

In 30 clinically healthy dogs (weights 7.5 to 57 kg) and in 41 proteinuric dogs the 131I-hippuran blood disappearance curve after single injection was determined (0 to 90 minutes), described by a bi-exponential function and analysed according to a two compartment model. The dependence of the blood clearance (C), representing an effective renal blood flow, on the bodyweight (W) (kg) could be described with both a linear function (C = 61 + 13.2 W ml min-1) and a power function (C = 30.56 W0.79 ml min-1) in the healthy dogs. The results of the regression between blood clearance and bodyweight were reproducible (r = 0.92, n = 10 residual error 12 per cent, P less than 0.01).     

Influence of normovolemic anemia on Doppler characteristics of the abdominal aorta and splanchnic vessels in Beagles

OBJECTIVE: To ultrasonographically evaluate hemodynamics in the abdominal aorta (AAo) and splanchnic vessels in dogs with experimentally induced normovolemic anemia. ANIMALS: 11 healthy Beagles. PROCEDURE: The AAo, cranial mesenteric artery (CMA), celiac artery (CA), hilar splenic artery (HSA), and main portal vein (MPV) were evaluated in conscious dogs immediately before and after experimental induction of severe normovolemic anemia (Hct, 16%) and during recovery from moderate and mild anemia (Hct, 26% and 34%, respectively). Peak systolic velocity (PSV) or peak velocity (PV), time-averaged mean velocity (TAVmean), pulsatility index (PI), resistive index (RI), blood flow, congestion index (CI), and heart rate (HR) were recorded. Results were compared for anemic and control states. RESULTS: Severe anemia caused significant increases in HR (25% to 70%), PSV (AAo, 45.8%; CMA, 56.1%; and CA, 41.9%), PV (MPV, 84.2%), and TAVmean, (AAo, 69.4%, CMA, 64.3%; CA, 29.7%; and MPV, 76.9%) and significant decreases in PI (AAo, 26.1%; HSA, 19.3%) and Cl (MPV, 45.2%).There was no significant change in PI of the CMA or CA, portal blood flow, or RI of any artery. Significantly higherTAVmean persisted in all vessels during moderate anemia, but higher PSV persisted only in the CMA; PI (CMA and CA) and RI (CA) decreased significantly, but portal blood flow increased significantly. Significant increase in TAVmean (AAo and CMA) persisted during mild anemia, and PI (AAo, CMA, and HSA) and RI (CMA) were significantly lower. CONCLUSIONS AND CLINICAL RELEVANCE: Doppler ultrasonography revealed hyperdynamic circulation in the AAo and splanchnic vessels in dogs with experimentally induced normovolemic anemia.     

Use of pulsed-wave Doppler echocardiography to determine aortic and pulmonary velocity and flow variables in clinically normal dogs

Transcutaneous pulsed-wave Doppler echocardiography was used to obtain velocity signals from the aortic and pulmonary roots of clinically normal adult dogs tranquilized with acepromazine. Doppler-derived variables included peak ejection velocity, ejection time, and velocity-time integral. The cross-sectional areas of the left and right ventricular outflow tracts were estimated from diameters of the respective orifices measured from two-dimensional echocardiographic images. These data were used to calculate stroke volume and cardiac output for each ventricle. Linear, single variable regressions of ejection time, velocity-time integral, and peak velocity with body weight showed no significant correlations. Significant correlations existed between body weight and estimated left and right ventricular stroke volume and cardiac output. A close correspondence existed between pulmonary and aortic determinations of velocity-time integral, stroke volume, and cardiac output. These results provide an initial framework for interpretation of clinical data by veterinary cardiologists.     

Influence of food intake on the absorption of lysine-acetylsalicylate in dogs

The influence of food intake on the absorption of a water-soluble aspirin, lysine-acetylsalicylate, was examined in six healthy adult mongrel dogs. Single-dose kinetics were determined following ingestion of 90 mg/kg of lysine-acetylsalicylate in dogs either fasted for 12 h or following a standard meal of either dry food or the same meal containing 20% of olive oil. Concurrent intake of food both reduced the serum salicylate concentration for 3 h after administration, and reduced the total amount of drug absorbed as reflected by the area under the plasma concentration/time curve(AUC). The effects were more pronounced following the fatty meal. Data from this investigation suggest that lysine-acetylsalicylate is therapeutically effective, without side effects when taken at the rate of 80 mg/kg at 12 h intervals, during or after feeding rather than before feeding.     

Evaluation of a canine total-elbow arthroplasty system: a preliminary study in normal dogs

OBJECTIVE: Short-term, in vivo evaluation of a total-elbow arthroplasty (TEA) system in normal dogs. STUDY DESIGN: Prospective evaluation comparing pre- and postoperative findings. ANIMALS: Six normal, skeletally mature, large-breed dogs. METHODS: Physical, radiographic, and force-plate gait examinations were performed on all dogs before surgery. TEA was performed in the dogs using a canine TEA system. Examinations were repeated every 8 weeks for 24 weeks, with an additional examination at 52 weeks. Pre- and postoperative findings were compared. RESULTS: The TEA led to an excellent outcome in 3 of 6 dogs. Force-plate gait examination found that the dogs continued to improve over time and had a peak vertical force (PVF) in the surgical limb that was 99.6% of normal (range, 95.8% to 106.4%) 52 weeks after surgery. Major problems encountered during the postoperative time period were non-weight-bearing lameness (1 dog), osteomyelitis (1 dog), and fracture of the ulna (1 dog). CONCLUSIONS: TEA can be successfully performed in dogs. CLINICAL RELEVANCE: Based on 1-year data, TEA can be successfully performed in dogs and could be considered as a treatment alternative for adult dogs with severe osteoarthritis and lameness of the elbow joint.     

Influence of food restriction during rearing on the body composition of layer-strain pullets and hens

The influence of two methods of food restriction during rearing on the body and liver composition of layer-type birds was investigated during and after restriction. In each of two experiments groups of birds were reared on one of three treatments: ad libitum food intake (A), time-limited food restriction (TR) or proportional food restriction (PR). All birds were fed ad libitum during the laying phase. In experiment 1, six birds from each treatment were selected at random for estimation of body and liver composition and killed at 70, 101, 162, 218 and 337 d of age. In experiment 2 four birds were selected from each treatment at 280 and 467 d of age. Body composition was predicted in experiment 2 at various times such as sexual maturity, using equations based on deuterium oxide dilution techniques. Body composition changes caused by food restriction were related to the length of restriction. Towards its end the major changes were: decreased body fat, increased total body water and increased water content of the fat-free mass for TR and PR birds compared to A birds. Some changes were not due to a reduced liveweight. Food restriction during rearing did not change body composition permanently, although predicted body fat at sexual maturity (experiment 2) was lower and protein content higher for TR and PR than for A birds. There was no demonstrable relationship between the body fat content predicted at sexual maturity and subsequent rate of lay (experiment 2).     

Comparison of ultrasonic Doppler flow monitor,oscillometric, and direct arterial blood pressure measurements in ill dogs

Objective – To compare blood pressure measurements obtained via ultrasonic Doppler flow monitor (DOP) and 2 oscillometric noninvasive blood pressure monitors (CAR and PAS) to invasive blood pressure (IBP) in hospitalized, conscious dogs with a range of blood pressures. Design – Prospective clinical study. Setting – University teaching hospital. Animals – Eleven client‐owned dogs aged between 4 months and 11.5 years (median 6 y), and weighing between 5.8 and 37.5 kg (median 30.2 kg). Interventions – Blood pressure measurement. Measurements and Main Results – Three consecutive measurements of systolic, diastolic, and mean arterial pressure (MAP) were recorded for each of the 3 indirect devices (only systolic for DOP), along with concurrent IBP measurements. The data were categorized into 3 groups: hypotensive (direct MAP<80 mm Hg), normotensive (80 mm Hg≤direct MAP≥100 mm Hg), and hypertensive (direct MAP>100 mm Hg). Each indirect method was compared with the corresponding direct arterial pressure using the Bland‐Altman method. Within the hypotensive group, each indirect method overestimated the corresponding IBP. Within the normotensive group all indirect systolic measurements and the PAS diastolic measurements underestimated the corresponding IBP. The remaining indirect measurements overestimated the corresponding IBP. Within the hypertensive group, DOP and CAR systolic measurements underestimated the corresponding IBP, and the remaining indirect measurements overestimated the corresponding IBP. In hypertensive dogs oscillometric systolic measurements were more accurate than MAP. In hypotensive dogs MAP measurements were more accurate than systolic measurements. All indirect measurements were most accurate in hypertensive dogs. Conclusions – The noninvasive blood pressure monitors in our study did not meet the validation standards set in human medicine. However, CAR diastolic and MAP measurements within the normotensive group, CAR MAP measurements within the hypertensive group, and PAS diastolic measurements in all groups were close to these standards. All indirect measurements showed greater bias during hypotension. Precision was poorer for all indirect systolic measurements than for MAP.     

Descending thoracic aortic blood flow parameters during emergent surgery in anesthetized critically ill dogs

Objective: To explore the potential value of transesophageally‐determined descending thoracic aortic blood flow parameters in critically ill dogs undergoing surgery. Design: Observational case series. Setting: Private small animal referral hospital. Animals: Ten anesthetized critically ill dogs that underwent emergent surgery. Interventions: Placement of the ultrasonic transesophageal probe. Measurements and main results: Transesophageally‐determined descending thoracic aortic blood flow, stroke volume, blood velocity, blood acceleration, left ventricular ejection time interval, and heart rate parameters were recorded every minute. Systolic and mean arterial blood pressures were non‐invasively determined and recorded at 1–5 minute intervals. The anesthetist and surgeon were blinded to the descending thoracic aortic blood flow parameters. All dogs received fluid challenges as part of their management, and 2 dogs received dopamine. The variability of the descending thoracic aortic blood flow parameters within each dog was greater than has been reported in non‐critically ill anesthetized dogs. Consistent trends in descending thoracic aortic blood flow parameters after fluid challenges were not found. An escalating dopamine infusion was, however, accompanied by increasing aortic blood flow, stroke volume, acceleration, and peak velocity. Conclusions: Descending thoracic aortic blood flow parameters may eventually be useful for evaluating the responses to and suggesting the need for cardiovascular interventions during emergent surgeries in anesthetized critically ill canine patients. For this to occur, more experience with this technology will be required.     

Activated coagulation times of whole blood in normal dogs and dogs with coagulopathies

The activated coagulation time (ACT) of whole blood was determined at 37C and at room temperature for 42 normal dogs and eight dogs with naturally–occurring or experimentally–induced coagulation defects.
Normal ACT values ranged from 64 to 95 seconds at 37C, and 83 to 129 seconds at room temperature. In abnormal dogs, ACT was increased on 14 of 17 occasions that a prolonged activated partial thromboplastin time (APTT) was recorded: the ACT failed to detect an abnormality on three occasions the APTT was slightly increased. ACT determination at 37C correlated better with APTT than did ACT testing at room temperature.
The ACT test is simple, inexpensive and convenient. It is a useful screening test for intrinsic coagulation defects in the dog. It is suggested that the test be performed at 37C: at this temperature an ACT of 95 seconds or more in a dog warrants further investigation.     

Duplex Doppler measurements of renal blood flow in a dog widi Addison's disease

Abnormal intrarenal flow In a seven-year old female Tibetan terrier with Addison's disease was demonstrated by duplex Doppler examination. Abnormal flow may reflect renal vasoconstriction due to increased activity of the renin-anglotensln system. Although not pathognomonic, an Increased resistive Index (< 0 - 70) In an otherwise ultrasonographically normal kidney can be due to Addison's disease and the technique may prove valuable as a quick non-Invasive tool In the management of this disease.