Evaluation of the effects of hospital visit stress on physiologic variables in dogs.

OBJECTIVE: To evaluate differences in pulse rate, rectal temperature, respiratory rate, and systolic arterial blood pressure in dogs between the home and veterinary hospital environments. DESIGN: Prospective observational study. ANIMALS: 30 client-owned healthy dogs. PROCEDURES: Study dogs had respiratory rate, pulse rate, rectal temperature, and systolic arterial blood pressure measured in their home environment. Dogs were then transported to the veterinary hospital, and measurements were repeated. RESULTS: Significant differences in blood pressure, rectal temperature, and pulse rate were observed between measurements obtained in the home and hospital environments. Mean blood pressure increased by 16% (95% confidence interval [CI], 8.8% to 24%), rectal temperature increased by < 1% (95% CI, 0.1% to 0.6%), and pulse rate increased by 11% (95% CI, 5.3% to 17.6%). The number of dogs panting in the hospital environment (19/30 [63%]) was significantly higher than the number of dogs panting in the home environment (5/30 [17%]) CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study suggested that practitioners should consider stress from transportation and environmental change when canine patients have abnormalities of vital signs on initial examination, and the variables in question should be rechecked before a definitive diagnosis of medical illness is reached or extensive further workup is pursued.

Changes in blood pressure following escalating doses of phenylpropanolamine and a suggested protocol for monitoring.

This prospective, cross-over, blinded study evaluated the effect of various doses of phenylpropanolamine (PPA) on blood pressure in dogs. Dogs were randomized to receive a placebo or 1 of 3 dosages of immediate release PPA, q12h for 7 days [1 mg/kg body weight (BW), 2 mg/kg BW, or 4 mg/kg BW] in a cross-over design. Blood pressure was recorded every 2 h, for 12 h, on days 1 and 7. There were significant increases in systolic, diastolic, and mean blood pressure following administration of PPA at 2 mg/kg BW and 4 mg/kg BW. A significant decrease in heart rate was also noted at all PPA dosages, but not in the placebo. Administration of PPA was associated with a dose response increase in blood pressure. Dosages of up to 2 mg/kg BW should be considered safe in healthy dogs.

Changements de la pression artérielle après des doses progressives de phénylpropanolamine et suggestion d'un protocole de surveillance. Cette étude prospective à l'insu et à plan d'étude croisée a évalué l'effet de diverses doses de phénylpropanolamine (PPA) sur la pression artérielle des chiens. Les chiens ont reçu au hasard un placebo ou 1 de 3 doses de PPA à action immédiate, q12h pendant 7 jours (1 mg/kg de poids corporel [PC], 2 mg/kg PC ou 4 mg/kg PC) dans un plan d'étude croisé. La pression artérielle a été consignée toutes les 2 h, pendant 12 h, aux jours 1 et 7. Il n'y a pas eu de hausses significatives de la pression artérielle systolique et diastolique ni de la pression artérielle moyenne après l'administration de PPA à 2 mg/kg PC et à 4 mg/kg PC. Une baisse significative de la fréquence cardiaque a aussi été notée dans toutes les doses de PPA, mais non avec le placebo. L'administration de PPA a été associée à une hausse de la pression artérielle en fonction de la dose. Des doses jusqu'à 2 mg/kg PC devraient être considérées sûres chez des chiens en santé.(Traduit par Isabelle Vallières).

Measurement of hyper- and hypotension during repeated dose toxicity studies in either freely moving or physically restrained cynomolgus monkeys.

INTRODUCTION: The measurement of cardiovascular endpoints in standard toxicology studies remains a challenge as the routinely used non-invasive methods require physical restraint, causing an increase of sympathetic neural activity, leading to excitement and potentially hypertension in the experimental animals. In this study, a miniature telemetry blood pressure transmitter was used to evaluate if the acute hyper- and hypotension could be detected in free moving cynomolgus monkeys as well as physically restrained animals using positive control drugs. Furthermore, as a comparator, routine high definition oscillometry (HDO) was performed in restrained animals. METHODS: Hemodynamic parameters were monitored continuously from conscious, freely moving animals following oral administration of vehicle (water) or 1 and 10mg/kg of etilefrine, and 1 and 4mg/kg of dihydralazine as positive control articles. A second dose session was performed to confirm the reproducibility of results and a third dose session combined with physical restraint procedures for blood collection and HDO measurements. RESULTS: There was a dose-dependent, statistically significant increase in the systolic blood pressure following oral doses of etilefrine at all 3 dose sessions. This effect was less apparent during session 3, probably due to the physical restraint applied for the blood sampling and HDO measurement. No differences in the blood pressure were measured using HDO. On all three dose sessions following oral doses of dihydralazine the expected statistically significant decrease in the diastolic pressure could be clearly measured even when the telemetric data recordings were combined with physical restraint. DISCUSSION: Due to the advantages of the minimally invasive telemetry technique compared to HDO and the possibility of prolonged measurement periods, it is an invaluable tool for blood pressure measurement in freely moving animals in toxicology studies.

Comparison of high-definition oscillometry -- a non-invasive technology for arterial blood pressure measurement -- with a direct invasive method using radio-telemetry in awake healthy cats.

This study compared indirect blood pressure measurements using a non-invasive method, high-definition oscillometry (HDO), with direct measurements using a radio-telemetry device in awake cats. Paired measurements partitioned to five sub-ranges were collected in six cats using both methods. The results were analysed for assessment of correlation and agreement between the two methods, taking into account all pressure ranges, and with data separated in three sub-groups, low, normal and high ranges of systolic (SBP) and diastolic (DBP) blood pressure. SBP data displayed a mean correlation coefficient of 0.92 ± 0.02 that was reduced for low SBP. The agreement level evaluated from the whole data set was high and slightly reduced for low SBP values. The mean correlation coefficient of DBP was lower than for SBP (ie, 0.81 ± 0.02). The bias for DBP between the two methods was 22.3 ± 1.6 mmHg, suggesting that HDO produced lower values than telemetry. These results suggest that HDO met the validation criteria defined by the American College of Veterinary Internal Medicine consensus panel and provided a faithful measurement of SBP in conscious cats. For DBP, results suggest that HDO tended to underestimate DBP. This finding is clearly inconsistent with the good agreement reported in dogs, but is similar to outcomes achieved in marmosets and cynomolgus monkeys, suggesting that this is not related to HDO but is species related. The data support that the HDO is the first and only validated non-invasive blood pressure device and, as such, it is the only non-invasive reference technique that should be used in future validation studies.

Comparison of indirect and direct blood pressure monitoring in normotensive swine.

The gold standard for blood pressure measurement in pigs is direct monitoring of arterial pressure, but this is an invasive technique adding complexity to surgical procedures. We sought to compare direct measurements obtained via catheterization to more easily-obtained indirect measurements using a sphygmomanometer with an automated cuff. Simultaneous measurements via an arterial pressure transducer and a child-size cuff were performed in pigs undergoing abdominal surgical procedures under normotensive conditions. Correlation between direct and indirect measurements was good (r=0.881). Systolic blood pressures for the cuff were higher than those for arterial measurements, while diastolic pressures were lower for the cuff than arterial. A Bland-Altman analysis confirmed this bias at the extremes of the normotensive range. For highly accurate readings, especially under stressed conditions, direct arterial catheterization remains the preferred method of measuring blood pressure. When monitoring surgical procedures, the more convenient blood pressure cuff can provide reliable measurements.

Importância da monitorização da pressão arterial em animal com trauma crânio encefálico – relato de caso / Importance of monitoring blood pressure with head trauma – case report

A pressão intracraniana (PIC) determina a perfusão encefálica, pois a pressão de perfusão encefálica (PPE) é resultante do gradiente entre a pressão arterial média (PAM) e a PIC. Além disso, o fluxo sanguíneo encefálico é constante dentro de determinados valores (pressão média entre 50 e 150 mmHg), pois está sob controle do fenômeno de auto regulação vascular do encéfalo (GRAY & ROSNER, 1987). O objetivo desse trabalho é descrever um caso de um animal com trauma crânio encefálico e mostrar a importância da monitorização da pressão arterial.

Simultaneous pulmonary and systemic blood pressure and ECG Interval measurement in conscious, freely moving rats.

Here we evaluated the ability of a new, dual blood-pressure telemetry transmitter to simultaneously measure pulmonary and systemic blood pressure and the electrocardiogram in rats. The transmitter was implanted in normotensive and monocrotaline-induced pulmonary hypertensive Wistar rats, with sensing catheters placed in the pulmonary artery (channel 1) and descending aorta (channel 2). Biopotential electrodes were positioned to record an apex-based lead II electrocardiogram. Pulmonary and systemic arterial blood pressure and electrocardiographic waveforms were recorded between 2 and 12 wk after implantation of the transmitter. During this period, pulmonary arterial pressure progressively increased in monocrotaline-treated compared with saline-treated rats. The pharmacologic response of rats to reference compounds was measured by using the transmitter to validate the technique and to evaluate the ability of the device to transmit changes in blood pressure and the electrocardiogram. Validation against 2 Millar high-fidelity blood-pressure catheters confirmed the accuracy of the blood pressure data recorded with the transmitter. In addition, local tolerance of the associated catheters was confirmed by histologic examination.

Percutaneous, ultrasonographically guided technique of catheterization of the abdominal aorta in calves for serial blood sampling and continuous arterial blood pressure measurement.

The study describes a technique of ultrasonographically guided transcutaneous catheter implantation into the abdominal aorta of 29 6- to 8-week-old German Holstein calves. Catheters were implanted between the left transverse processes of L3 and L4, left in place for 2 days and used for serial blood sampling and continuous measurement of blood pressure. Complete cell counts and clinical examination were performed before, as well as 1 and 5 days after implantation. Catheterization was successful in all calves. The catheter was patent for blood sampling and pressure recordings at all times. A significant decrease in red blood cells was found in all animals after catheterization, which remained reduced for 5 days. Clinical signs of anaemia were absent. In conclusion, ultrasonographically guided catheterization of the abdominal aorta provides a continuous arterial access in calves, whereby the minimal invasive technique and the ultrasonographical guidance reduces accidental tissue trauma and pain for the animal.

Direct blood pressure monitoring in laboratory rodents via implantable radio telemetry.

The ability to monitor and record precise blood pressure fluctuations in research animals is vital to research for human hypertension. Direct measurement of blood pressure via implantable radio telemetry devices is the preferred method for automatic collection of chronic, continuous blood pressure data. Two surgical techniques are described for instrumenting the two most commonly used laboratory rodent species with radiotelemetry devices. The basic rat procedure involves advancing a blood pressure catheter into the abdominal aorta and placing a radio transmitting device in the peritoneal cavity. The mouse technique involves advancing a thin, flexible catheter from the left carotid artery into the aortic arch and placing the telemetry device under the skin along the animal's flank. Both procedures yield a chronically instrumented model to provide accurate blood pressure data from an unrestrained animal in its home cage.

Evaluation of noninvasive oscillometric blood pressure monitoring in anesthetized boid snakes.

OBJECTIVE: To determine the accuracy of a noninvasive oscillometric monitor in the measurement of arterial blood pressure in anesthetized boid snakes. DESIGN: Evaluation study. ANIMALS: 4 boa constrictors (Boa constrictor), 2 carpet pythons (Morelia spilota), and 2 reticulated pythons (Python reticulatus). PROCEDURES: After induction of anesthesia with isoflurane, each snake was instrumented with an arterial catheter connected to a pressure transducer and oscilloscope to obtain invasive measurements of systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressure as well as a pressure waveform. A cuff connected to an oscillometric device was placed on the tail immediately distal to the vent for noninvasive measurements. Heart rate, respiratory rate, and invasive and noninvasive measurements of SAP, DAP, and MAP were obtained every 5 minutes for 45 minutes. Delivered isoflurane concentration was increased in 15-minute increments to induce hypotension. Repeatability of each device and fixed and proportional biases between devices were calculated. RESULTS: Throughout most of the measured ranges of blood pressures, the oscillometric unit overestimated the SAP and underestimated the DAP and MAP, compared with respective direct measurements. When the invasively determined SAP was > 100 mm Hg, the oscillometric unit underestimated all 3 variables. Fixed bias was significant for SAP and DAP, and proportional bias was significant for SAP and MAP. CONCLUSIONS AND CLINICAL RELEVANCE: When using an oscillometric blood pressure monitor on anesthetized boid snakes, veterinarians can potentially monitor changes in blood pressure, although the displayed readings may underestimate DAP and MAP and overestimate SAP. Indirect measurements of blood pressure made with the oscillometric device cannot substitute for direct measurements.

Long term assessment of blood pressure transducer drift in rhesus monkeys chronically instrumented with telemetry implants.

INTRODUCTION: The accurate assessment of blood pressure is often a key component of preclinical cardiovascular disease/efficacy models and of screening models used to determine the effects of test agents on cardiovascular physiology. Of the many methods utilized in large animals, telemetry is becoming more widely used throughout preclinical testing, and non-human primates are playing an ever increasing role as a large animal model to evaluate the cardiovascular effect of novel test agents. Therefore, we sought to characterize pressure transducer drift of a telemetry implant in primates over an extended duration. METHODS: We instrumented ten rhesus monkeys with a Konigsberg T27F implant and a chronic indwelling arterial catheter and cross calibrated the diastolic pressure recorded by the implant to the diastolic pressure that was simultaneously recorded through the arterial catheter using a calibrated external transducer/amplifier system. RESULTS: While all implanted pressure transducers experienced drift to some degree, magnitude of drift varied across animals (range of average drift 0.7-20.5 mmHg/month). Specifically, we found that all implants could be calibrated within the voltage range of the instrument up to 6 months after implantation despite the drift observed. Between 6 and 12 months, 3 of the 10 implants studied drifted outside the defined voltage range and were unusable, two more drifted off scale within 2 years, while the remainder remained within the operating voltage range. DISCUSSION: Given that pressure transducer drift was not consistent across implants or time, these data suggest careful assessment and quantitative correction for in vivo drift of telemetry blood pressure transducers implanted for extended duration should be considered.

Direct blood pressure monitoring.

Veterinary care has continued to advance by implementing more of the equipment and techniques that are commonly used in human medicine. This includes the placement of arterial catheters and pulmonary artery catheters and continuous monitoring of arterial pressure, central venous pressure, and pulmonary artery pressure. This article describes the technique for placement of appropriate catheters, the equipment that is needed, and the waveforms that are obtained when measuring direct arterial pressures, central venous pressures, and pulmonary arterial pressures.

Radiotelemetry catheter implantation: surgical technique and results in cats.

Arterial blood pressure in cats can be measured by direct or indirect techniques. Most direct measurement techniques require sedation or anesthesia, which decreases blood pressure. The restraint and human intervention needed for indirect techniques cause blood pressure to increase. These limitations make the accurate assessment of blood pressure and the response to antihypertensive medications difficult to interpret. Radiotelemetry allows for direct measurement of the arterial blood pressure and heart rate without sedation, anesthesia, or animal handling during measurement. A surgical technique for the placement of radiotelemetry catheters and the complications associated with the technique have not been described in cats. Our purpose is to provide a detailed description of the placement of the modified implant model TA11PA-C40 (Data Sciences International), with accompanying illustrations, and to discuss complications associated with the procedure. Radiotelemetry catheters were surgically placed in the left femoral artery of 12 cats. The surgical procedure was completed within 50 min, and no surgical complications occurred in any cat. The radiotelemetry catheters were used for an average of 6.5 weeks (range, 5.5 to 9.5 weeks). This technique allows for long-term monitoring of ambulatory blood pressure and heart rate in the research setting. This methodology is especially useful for studies of the pathophysiology of hypertension and assessment of the efficacy of antihypertensive medications.

Evaluation of the white-coat effect in cats.

The diagnosis and management of systemic hypertension in cats requires a reliable method for measurement of systemic arterial blood pressure (BP) in clinical patients. Unfortunately, the setting of a clinical practice and the act of measuring BP might raise BP and heart rate (HR), an effect referred to as the white-coat effect in human patients. The purpose of the present study was to determine if a white-coat effect was experienced by cats. Radiotelemetric implants were used to measure BP and HR in 13 conscious cats in a research colony while undisturbed in their cages and while subjected to simulated visits to a veterinarian's office. The white-coat effect was taken to be the difference between the overall 24-hour average value for parameters of BP and HR and the corresponding value during the simulated office visit. A white-coat effect was observed in cats. In healthy cats, the systolic BP measured during the examination period of the simulated office visit exceeded the 24-hour average systolic BP by 17.6+/-1.5 mm Hg. However, marked heterogeneity occurred in the pattern and magnitude of the increase in systolic BP above the 24-hour baseline and the increase varied between 75.3 and -27.2 mm Hg for the healthy cats. Variation in response to the simulated office visit was observed among cats and among visits by the same cat. During an office visit, the magnitude of the white-coat effect tended to decrease, but not disappear, over time. The magnitude of the white-coat effect varied when cats were subjected to 5 repeat office visits, but did not diminish in the group as a whole. The mean increase in systolic BP during the examination (22.3+/-0.9 mm Hg) was greater (P < .05) in cats with renal insufficiency. Although the heterogeneity of response expected from companion animals might be greater than that observed in these colony cats, these results indicate that veterinarians should carefully consider the white-coat effect in evaluation of BP in cats. A quiet, undisturbed environment and adequate time for acclimation should be included in the standard protocol for measurements of BP. Because of day-to-day variation in the white-coat effect in individual cats, multiple serial measurements following a standard protocol should provide the best estimate of BP in cats.

Evaluation of noninvasive monitoring techniques in domestic ferrets (Mustela putorius furo).

OBJECTIVE: To evaluate instrument placement and accuracy of indirect physiologic monitoring techniques in anesthetized domestic ferrets. ANIMALS: 10 healthy adult female ferrets (Mustela putorius furo). PROCEDURE: Direct arterial blood pressure measurement and arterial blood sample collection were performed in ferrets. A pulse oximeter probe was clipped to a forefoot or hind foot; an airway adaptor for capnography was attached to the endotracheal tube; and a sphygmomanometer cuff and Doppler flow probe were positioned on the tail. Isoflurane and nitrous oxide concentrations were varied to induce episodes of hypotension or hypoxia, respectively. Aforementioned noninvasive techniques were compared with direct methods of arterial blood gas analysis, hemoximetry, and arterial blood pressure measurement. Simultaneously obtained direct and indirect measurements were statistically evaluated for mean and SD of the differences, and SEM, and subjectively, for ease of use and relevance to the clinical situation. RESULTS: Values obtained from pulse oximetry were closely related to oxygen saturation measured by blood gas analysis (O2sat). The mean (+/- SD) difference for all results was -0.49 (+/- -4.09)%. The most precise measurements were obtained when O2sat was between 90 and 100%. Capnography measurements varied between ranges. The most accurate measurements were obtained when PaCO2 was < 25 mm of Hg, when the mean difference was 1.6 (+/- -3.01) mm of Hg. Indirect blood pressure measurement consistently underestimated the direct blood pressure value. CONCLUSIONS AND CLINICAL RELEVANCE: Pulse oximetry is a convenient and accurate method for monitoring oxygen saturation in domestic ferrets. Capnography is useful for monitoring respiratory rate and pattern, but may present difficulties in interpretation of actual PaCO2. Indirect blood pressure monitoring is not accurate by use of current methods in ferrets.

Measurement of blood pressure and heart rate by telemetry in conscious unrestrained marmosets.

A system is described for the continuous measurement of blood pressure, heart rate and motor activity by telemetry in conscious marmosets freely moving in their home cages. Consistent diurnal variations in these parameters were observed under standard conditions. However these parameters were sensitive to changes in the environment. Blood pressure values were similar to those measured by non-telemetric methods in conscious restrained marmosets while heart rate values were significantly lower.