Effects of various factors on Doppler ultrasonographic measurements of radial and coccygeal arterial blood pressure in privately owned, conscious cats

Jacqueline C. Whittemore Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Michael R. Nystrom Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Dianne I. Mawby Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Abstract

OBJECTIVE To assess the effects of age, body condition score (BCS), and muscle condition score (MCS) on radial and coccygeal systolic arterial blood pressure (SAP) in cats.

DESIGN Prospective randomized trial.

ANIMALS 66 privately owned cats enrolled between May and December 2010.

PROCEDURES BCS and MCS of cats were assessed by 2 investigators; SAP was measured via Doppler ultrasonic flow detector, with cats positioned in right lateral or sternal recumbency for measurements at the radial or coccygeal artery, respectively, with order of site randomized. Associations among variables were assessed through correlation coefficients, partial correlation coefficients, and ANCOVA.

RESULTS Interrater reliability for BCS and MCS assessment was high (correlation coefficients, 0.95 and 0.83, respectively). No significant effect was identified for order of SAP measurement sites. Coccygeal and radial SAP were positively correlated (ρ = 0.45). The median difference in coccygeal versus radial SAP was 19 mm Hg, but differences were not consistently positive or negative. Radial SAP was positively correlated with age (ρ = 0.48) and negatively correlated with MCS (ρ = −0.30). On the basis of the correlation analysis, the association between radial SAP and MCS reflected the confounding influence of age. Coccygeal SAP was not significantly correlated with age, BCS, or MCS.

CONCLUSIONS AND CLINICAL RELEVANCE Use of the coccygeal artery is recommended to reduce the confounding effects of age and sarcopenia on Doppler ultrasonographic SAP measurements in cats. Additionally, monitoring for changes in MCS is recommended for cats undergoing serial SAP measurement.

Abstract

OBJECTIVE To assess the effects of age, body condition score (BCS), and muscle condition score (MCS) on radial and coccygeal systolic arterial blood pressure (SAP) in cats.

DESIGN Prospective randomized trial.

ANIMALS 66 privately owned cats enrolled between May and December 2010.

PROCEDURES BCS and MCS of cats were assessed by 2 investigators; SAP was measured via Doppler ultrasonic flow detector, with cats positioned in right lateral or sternal recumbency for measurements at the radial or coccygeal artery, respectively, with order of site randomized. Associations among variables were assessed through correlation coefficients, partial correlation coefficients, and ANCOVA.

RESULTS Interrater reliability for BCS and MCS assessment was high (correlation coefficients, 0.95 and 0.83, respectively). No significant effect was identified for order of SAP measurement sites. Coccygeal and radial SAP were positively correlated (ρ = 0.45). The median difference in coccygeal versus radial SAP was 19 mm Hg, but differences were not consistently positive or negative. Radial SAP was positively correlated with age (ρ = 0.48) and negatively correlated with MCS (ρ = −0.30). On the basis of the correlation analysis, the association between radial SAP and MCS reflected the confounding influence of age. Coccygeal SAP was not significantly correlated with age, BCS, or MCS.

CONCLUSIONS AND CLINICAL RELEVANCE Use of the coccygeal artery is recommended to reduce the confounding effects of age and sarcopenia on Doppler ultrasonographic SAP measurements in cats. Additionally, monitoring for changes in MCS is recommended for cats undergoing serial SAP measurement.

Systemic hypertension is an insidious problem with no initial overt clinical signs.1,2 In cats, it develops secondary to kidney disease and hyperthyroidism but can also be idiopathic.1,3,4 Sustained systemic hypertension can cause serious end-organ damage to the eyes, brain, kidneys, and heart1,3 and is associated with shorter long-term survival times than those for cats without hypertension.5 Therefore, routine surveillance for hypertension is recommended for cats with chronic kidney disease or hyperthyroidism or those of advanced age (≥ 11 years).1,4–6

Conversely, hypotension (Doppler ultrasonographic SAP < 90 mm Hg) in critically ill cats is associated with a decreased rate of survival to hospital discharge, compared with the rate for cats without hypotension.7,8 In those circumstances, an increase in SAP of > 20 mm Hg is associated with a marked increase in the likelihood of hypotensive cats surviving to hospital discharge.7 Given these findings, accurate monitoring for and aggressive treatment of derangements in blood pressure in critically ill cats are important for achieving a favorable long-term outcome.

Although direct measurement of arterial blood pressure remains the reference (gold) standard for blood pressure determination, it is technically demanding in cats and requires specialized equipment.1,9 Less invasive, indirect methods of blood pressure measurement involve fewer risks to cats and are preferred for outpatient evaluations.1,9 Indirect blood pressure measurement can be performed by use of Doppler ultrasonic flow detectors or automated oscillometric devices. The oscillometric method involves an automated system with a cuff that records the oscillations of the blood vessel wall at various pressures and computes systolic, diastolic, and mean arterial blood pressures. In contrast, the Doppler ultrasonographic method involves a piezoelectric crystal positioned over an artery distal to an inflatable cuff to detect reestablishment of blood flow during cuff deflation. Systolic and diastolic pressures can be measured, although diastolic pressures measured via Doppler ultrasonic flow detector are often inaccurate because of increased difficulty and subjectivity in detection of tonal shifts.10–13

More training is required for accurate collection of Doppler ultrasonographic blood pressure measurements than is needed for collection of oscillometric measurements. However, in a studya involving conscious cats, no significant difference in Doppler ultrasonographic measurements of SAP was identified on the basis of operator experience. Clipping of hair at the site of crystal application can be necessary to achieve adequate contact and generation of a tonal signal, which could increase the potential for a so-called white-coat effect, as has been documented after performance of other unfamiliar procedures in both dogs and cats.14–16 However, accuracy of oscillometric blood pressure measurements in anesthetized cats varies.12,17

Doppler ultrasonographic blood pressure measurements are reportedly more repeatable and more precise than oscillometric measurements in conscious and anesthetized cats and are less time-consuming to collect.11,18 Successful collection rates in conscious cats consistently approach 100% when the Doppler ultrasonographic method is used, compared with 50% to 56% when the oscillometric method is used.11,12 Additionally, less bias has been reported between direct versus Doppler ultrasonographic measurements of SAP when those measurements are obtained from anesthetized cats at the coccygeal versus radial artery,12 and conscious cats reportedly tolerate oscillometric blood pressure measurements better when the coccygeal versus radial artery is used.19

Body condition score and MCS are determined subjectively by means of observation and palpation criteria.20–22 Theoretically, variability in BCS or MCS could affect Doppler-derived blood pressure measurements because of interference from tissue surrounding the compressible artery.23 Although a study24 revealed no association between BCS and SAP measurements made via Doppler ultrasonic flow detector at the radial artery in conscious cats, results were not compared with those obtained at the coccygeal artery, and MCS was not assessed. In the authors’ experience, discordance between indirect radial and coccygeal SAP measurements is generally greater for cats with a low BCS or MCS than for cats with a higher BCS or MCS. Low fat stores might affect compression of the coccygeal artery against the caudal vertebrae, whereas low muscle mass could have a greater effect on radial pressure measurement than on coccygeal blood pressure measurement. To the authors’ knowledge, the impact of BCS and MCS on discordance in Doppler ultrasonographic measurements of SAP at the coccygeal and radial arteries in cats is unknown. The purpose of the study reported here was to assess the effects of age, BCS, and MCS on indirect Doppler ultrasonographic measurements of radial and coccygeal SAP in conscious cats. The null hypothesis was that there would be no effect of BCS or MCS on differences in SAP between measurement sites.

Materials and Methods

Animals

Privately owned cats belonging to faculty, staff members, and students at the University of Tennessee were eligible for enrollment in the study, as were cats evaluated at the university's Veterinary Medical Center. Cats were excluded when they were < 1 year of age, had no tail, had been sedated or anesthetized within the previous 12 hours, or became fractious during the study. Known medical conditions, medications, body weight, and heart rate were recorded for each cat.

Cats were enrolled between May and December 2010 on the basis of initial BCS determination by 1 investigator (MRN), who used a 5-point scale.22 Briefly a score of 1 indicated ribs visible with no palpable fat, 2 indicated ribs easily palpable with little palpable fat, 3 indicated well proportioned, 4 indicated ribs not easily palpable with moderate fat cover, and 5 indicated ribs not at all palpable with moderate to heavy fat cover.22 The enrollment goal was 20 cats/whole-integer BCS category for a total sample size of 100 cats. Once 20 cats had been enrolled within a given score category, no additional cats with that BCS were enrolled.

The study protocol was approved by the Institutional Animal Care and Use Committee of the University of Tennessee, Knoxville. Informed consent was obtained from cat owners as a condition for enrollment in the study.

BCS and MCS assessment

All investigators received BCS and MCS training by a board-certified nutritionist prior to initiation of the study. Body condition score22 and MCS were determined independently by each investigator. The MCS was assessed by use of a 4-point scale, by which a score of 3 represented normal muscle mass and a score of 0 indicated marked muscle wasting.21 The BCS scores from one of the investigators (MRN) were used for initial block randomization of cats to measurement groups. The mean of BCS and MCS scores from the other 2 investigators (DIM and JCW) was used for statistical analyses.

Randomization

Before the study began, a randomization table was generated by use of a commercially available statistics programb to determine the order of blood pressure measurement sites (radial artery vs coccygeal artery first) for the target number of cats within each BCS category to be enrolled in the study. Cats were allocated to measurement groups in accordance with the next available assignment in the randomization table for their BCS. If a cat became fractious and had to be excluded from the study after assignment in the randomization table, that randomization assignment was moved to the end of the sequence for the relevant BCS category.

Blood pressure measurement

Blood pressure measurements were performed by use of a Doppler ultrasonic flow detector and flat infant probe.c Briefly, each cat was taken into an examination room (with its owner, when possible) for blood pressure measurements by 1 investigator (MRN). A soft measuring tape was used to determine the circumference of the left mid antebrachium and the base of the tail. Hair was shaved on the palmar surface of the left foot between the carpal and metacarpal pads and on the ventral surface of the tail distal to the position of the blood pressure cuff. The cat was then allowed to acclimate to the examination setting and investigator for 5 minutes. Heart rate was recorded after acclimation.

For measurement of blood pressure at the left radial artery, cats were positioned in right lateral recumbency,18 and for measurements at the coccygeal artery, cats were positioned in sternal recumbency.25 An inflatable blood pressure cuffd was then selected to achieve a cuff width of approximately 30% to 40% of the measured circumference of the mid antebrachium or tail and applied to the appendage. Ultrasonic coupling gel was applied to the Doppler piezoelectric crystal, and the crystal positioned perpendicularly over the artery. The cuff was inflated with a sphygmomanometer to approximately 20 mm Hg above the point at which blood flow was no longer audible. Air was slowly released from the cuff, and SAP was recorded as the value at which blood flow could first be heard. Pressure was completely released from the sphygmomanometer, and the process was repeated 2 to 5 times to obtain 3 consistent SAP readings. These results were averaged for each cat to obtain the mean SAP at each measurement site. Cats were allowed to reacclimate for 5 minutes prior to blood pressure measurement at the second measurement site.

Statistical analysis

Descriptive statistics were computed for each variable. Data were analyzed for normality of distribution with the Shapiro-Wilk test and for the presence of outliers by means of the Tukey test for outliers and box-and-whisker plots. The intraclass correlation coefficient and Cohen κ were calculated to assess interrater reliability for BCS and MCS measurements, respectively. The means of BCS and MCS measurements were used for all further analyses. Mean SAP measurements > 150 mm Hg were considered consistent with hypertension in accordance with existing guidelines.1 Mean SAP measurements ≤ 90 mm Hg were considered consistent with hypotension.

Pearson product moment (r) and Spearman rank correlation (ρ) coefficients were calculated to investigate correlations between radial and coccygeal SAP measurements. Pearson partial correlation coefficients (r) were used to assess correlations between measurement sites and possible covariates (cat age, body weight, heart rate, BCS, MCS, and limb or tail circumference as appropriate).

A mixed-effects crossover design and corresponding ANCOVA was performed to determine whether mean SAP differed between radial and coccygeal measurement sites and to assess whether the washout period between treatment sites was adequate. Measurement order (first vs second reading) and site (radial vs coccygeal measurement) were included as fixed effects. Age, body weight, heart rate, BCS, MCS, and cuff size as a percentage of appendage circumference were initially included as covariates in the analysis. Cat nested within sequence was included as a random effect. A compound symmetry variance-covariance structure was incorporated into the model to account for constant covariates. Backward variable selection was performed on the full model to determine which covariates explained significant variability in mean SAP. Factors included in the final model were measurement order, site, and age. The Shapiro-Wilk test of normality of the residuals was performed to ensure the assumptions of the statistical method had been met. All analyses were performed and figures created by use of statistical software.b,e

Results

Seventy-one cats were initially enrolled in the study; however, 5 cats were excluded because of fractiousness (n = 2), intolerance of radial (1) or coccygeal (1) SAP measurement, or inadequate tail length (1). Of the remaining 66 cats, 45 (68%) were healthy and 21 (32%) had primary diagnoses of gastrointestinal (8), dermatologic (3), cardiovascular (2), kidney (2), or lower urinary tract disease (2); arthritis (1); cancer (1); and weight loss of unknown cause (1). Three cats with gastrointestinal disease had additional diagnoses: hyperthyroidism (n = 2), diabetes mellitus (1), kidney disease (1), and cardiovascular disease (1).

Age, sex, body weight, BCS, MCS, and mean SAP measurements at the radial and coccygeal arteries were summarized (Table 1). The intraclass correlation coefficient and Cohen κ for interrater reliability of BCS and MCS measurements were 0.95 (P < 0.001) and 0.83 (P < 0.001), respectively.

Table 1—

Characteristics of privately owned cats in which SAP was measured via Doppler ultrasonic flow detector at the radial and coccygeal arteries.

 Enrollment BCS
Variable1 or 2 (n = 9)3 (n = 20)4 or 5 (n = 37)All cats (n = 66)
Age (y)7(3–18)4 (1–15)6 (1–16)6 (1–18)
Female sex5 (56)11 (55)12 (32)28 (42)
Body weight (kg)3.31 (2.24–4.24)4.10 (2.90–5.22)5.71 (3.02–9.80)4.59 (2.24–9.80)
Mean BCS*2.0 (1–2.3)3.0 (2.7–3.3)4.0 (3.3–5.0)3.8 (1.0–5.0)
Mean MCS2.7 (0.9–3.0)3.0 (2.0–3.0)3.0 (2.3–3.0)3.0 (1.0–3.0)
Heart rate (beats/min)210 (162–258)222 (156–279)204 (174–264)207 (156–279)
Mean radial SAP (mm Hg)137 (90–187)126 (87–201)125 (91–181)126 (87–201)
Mean coccygeal SAP (mm Hg)181 (31–232)150 (90–212)140 (89–219)145 (31–232)

Values are reported as number (%) for female sex and as median (range) for all other variables.

Body condition was assessed by use of a 5-point scale, in which a score of 1 indicated ribs visible with no palpable fat, 2 indicated ribs easily palpable with little palpable fat, 3 indicated well proportioned, 4 indicated ribs not easily palpable with moderate fat cover, and 5 indicated ribs not at all palpable with moderate to heavy fat cover.22 The mean of scores for 2 investigators was used for statistical analyses.

Muscle condition was assessed by use of a 4-point scale, by which a score of 3 represented normal muscle mass and a score of 0 indicated marked muscle wasting. The mean of scores for 2 investigators was used for statistical analyses.

Mean SAP was measured indirectly via Doppler ultrasonic flow detector; values are based on 3 consistent measurements/site/cat. To convert kilograms to pounds, multiply by 2.2.

Mean SAP measured at the coccygeal and radial arteries by means of Doppler ultrasonic flow detector were significantly (P < 0.001) and positively correlated (ρ = 0.45; Figure 1). Differences in mean SAP between the 2 measurement sites were not consistently positive or negative (Figure 2). The mean of all mean SAP measurements was 19 mm Hg (15%) higher at the coccygeal artery than at the radial artery. On the basis of mean SAP measurements obtained at the coccygeal artery, 28 of 66 (42%) cats were categorized as hypertensive (> 150 mm Hg). Of these, 20 cats (71%) had radial artery measurements suggesting normotension (≤ 150 mm Hg) instead. Conversely, only 9 of 66 (14%) cats were categorized as hypertensive on the basis of radial artery measurements, 2 of which had coccygeal measurements suggesting normotension instead. Four cats had SAP measurements consistent with hypotension. One cat had marked hypotension as indicated by the mean coccygeal SAP (30 mm Hg) and less severe hypotension as indicated by the mean radial SAP (90 mm Hg). On the basis of mean coccygeal and radial SAPs, 2 and 1 other cats were hypotensive, respectively.

Figure 1—
Figure 1—

Individual values for mean SAP (3 consistent measurements/site/cat) measured via Doppler ultrasonic flow detector at the radial and coccygeal arteries of 66 privately owned cats.

Citation: Journal of the American Veterinary Medical Association 250, 7; 10.2460/javma.250.7.763

Figure 2—
Figure 2—

Individual values for mean SAP (3 consistent measurements/site/cat) measured via Doppler ultrasonic flow detector at the radial (circles) and coccygeal (inverted triangles) arteries of 66 privately owned cats, grouped by BCS (5-point scale). Nine cats had a BCS of 1 or 2 (ribs visible or easily palpable with no or little palpable fat), 20 had a BCS of 3 (well proportioned), and 37 had a BCS of 4 or 5 (ribs not easily or not at all palpable with moderate to heavy fat cover).22

Citation: Journal of the American Veterinary Medical Association 250, 7; 10.2460/javma.250.7.763

Mean SAP measured at the coccygeal artery was not significantly correlated with any other factor (age, body weight, heart rate, BCS, or MCS). Mean SAP measured at the radial artery was significantly and positively correlated with age (ρ = 0.48; P < 0.001) and negatively correlated with MCS (ρ = −0.30; P = 0.02). Mean radial SAP was not correlated with body weight, heart rate, or BCS. Age and MCS were significantly (P < 0.001) and negatively correlated (ρ = −0.57). On the basis of the results of Pearson partial correlation analysis, the association between radial SAP values and MCS reflected the confounding influence of age (r = 0.4; P = 0.001). No significant effect on mean SAP was identified for order of measurement site (radial vs coccygeal artery first), but age had a significant (P = 0.006) positive linear association with mean SAP.

Discussion

Mean SAP in cats was measured at the radial and coccygeal arteries via Doppler ultrasonic flow detector in the present study. Although values obtained at both sites were significantly correlated, that correlation was fairly low and differences between the 2 sites were not consistently positive or negative. Measurements obtained at the coccygeal artery had no correlation with age, BCS, or MCS. Although an association was identified between radial artery measurements and age, this association was attributable to the confounding effect of MCS. For these reasons, use of the coccygeal artery is recommended for Doppler ultrasonographic measurement of SAP in cats of advanced age or with identifiable sarcopenia.

Patient positioning and cuff size are important technical aspects of indirect measurement of blood pressure via oscillometric or Doppler ultrasonographic methods.1 The cuff should be positioned at the level of the heart to most accurately reflect the arterial blood pressure. Patient positioning can considerably affect indirect blood pressure measurements, even when the cuff is kept at the level of the heart.26 For this reason, standardization of both subject position and measurement site is important when monitoring blood pressure over time.

Sternal recumbency was chosen for coccygeal measurements in the present study to minimize the vertical distance from the cuff site to the heart.25 Although measurements at the radial artery can also be obtained with a cat in sternal recumbency, the forelimb must often be gently extended to do so by placing a hand behind the cat's elbow.23 During preliminary evaluations, we noticed a decrease in signs of stress and heart rate when cats were positioned in lateral recumbency rather than restrained in sternal recumbency with the measurer's hand behind the cat's elbow. Additionally, greater precision was achieved for Doppler ultrasonographic and oscillometric measurements when lateral recumbency was used in other studies.18,26 For these reasons, lateral recumbency was chosen for measurements involving the forelimb. It is possible that different results would have been obtained if forelimb measurements had been obtained with cats positioned in sternal recumbency.

Although mean SAP values measured at the radial and coccygeal arteries were correlated in the present study, this correlation was low. Acclimation of cats to measurement conditions can decrease the white-coat effect,16 and such acclimation could have led to differences in mean SAPs between those measured at the first and second site. However, no significant effect on mean SAP was identified for measurement site order, suggesting that any acclimation that occurred during measurements did not substantially affect the overall findings.

Similarly, low correlations have been reported between direct measurements and oscillometric (indirect) measurements of SAP in conscious and anesthetized dogs,27,28 with coccygeal measurements having a lower correlation in 1 study27 but a higher correlation and precision in another study.28 In a study12 involving anesthetized cats, Doppler ultrasonographic blood pressure readings at the tail were more accurate than readings at other sites. To the authors’ knowledge, similar data have not been published for conscious cats. Both cats and dogs appear to tolerate blood pressure measurements better when the coccygeal artery rather than radial artery is used with oscillometric methods.19,28 It is possible, therefore, that improved precision of indirect coccygeal versus radial artery measurements in conscious cats partially reflects a decrease in the white-coat effect due to improved tolerance of measurements obtained at the coccygeal artery.

Similar to the present study, previous studies12,19 have revealed higher indirect SAP measurements at the coccygeal versus radial artery in cats. Mean blood pressures at the coccygeal artery were 8.7% higher than at the radial artery in a study19 of oscillometric blood pressure measurements in conscious cats. Cat positioning during measurement was not standardized in that study, so the investigators could not rule out the impact of differences in distances between the heart and tail during measurements of different cats. Results of our study are also similar to those of a study12 involving anesthetized cats, although direct comparisons between tail and limb measurements were not made in that study.

In the present study, the mean of all mean SAP measurements was 19 mm Hg (15%) higher at the coccygeal artery than at the radial artery. If coccygeal artery measurements were considered the gold standard on the basis of their higher precision (vs radial artery measurements) in conscious and anesthetized cats in other studies,11,18 this difference would have resulted in miscategorization of 20 hypertensive cats as normotensive. Conversely, only 2 cats would have been miscategorized as normotensive if radial artery measurements were considered the gold standard. Differences between the 2 sites for individual cats were not consistently positive or negative, but differences in mean SAP values appeared greater for cats with a lower BCS (Table 1), although BCS was not significantly associated with coccygeal or radial artery measurements. Given the association identified between increasing radial SAP and decreasing MCS, this difference may have reflected a lower MCS in cats with low BCS, as has been reported.21

One cat with a low BCS had marked hypotension as indicated by the mean coccygeal SAP (30 mm Hg) and less severe hypotension as indicated by the mean radial SAP (90 mm Hg). Because of the severity of hypotension, blood pressures in this cat were remeasured after completion of the initial assessment and operator error was ruled out. Although the coccygeal value was quite low, it was not identified as an outlier during statistical analysis and so was retained in the dataset. Three other cats in the study were also classified as hypotensive on the basis of coccygeal (n = 2) or radial (1) SAP measurements.

Appropriate width of the inflatable cuff is also important for accurate blood pressure measurement.1 Cuffs that are larger than optimal can result in erroneously low readings, whereas smaller cuffs can result in excessively high readings. Because of the limited range of cuff sizes available, optimal cuff size might not be achievable for some small cats. In the present study, ideal cuff size for the radial and coccygeal sites was not always the same for individual cats, despite similar circumferences as judged on the basis of visual assessment. This finding supports the importance of measuring the circumference of any blood pressure measurement site prior to cuff selection for cats.

The BCS assessment system used in the present study involves subjective visual inspection and manual palpation to determine the nutritional status of a cat or dog.22 Both 5-point and 9-point systems have been described. In the 5-point system, a BCS of 3 indicates a well-proportioned cat with an observable waist, palpable ribs with a slight fat covering, and minimal abdominal fat pad.22 In the present study, no association was found between BCS and either coccygeal or radial mean SAP measurements. These results are consistent with those of a previous study,25 in which no association was identified between BCS and oscillometric blood pressure measurements obtained at the coccygeal artery in cats. Three other studies10,24,29 also revealed no association between body weight and indirect blood pressure measurements in cats, although BCS was not evaluated.

Muscle condition scoring is performed by visual inspection and palpation of muscles over bones to determine the extent of any muscle wasting.21,22 To the authors’ knowledge, the present study represents the first in which the potential association between MCS and indirect blood pressure measurements has been assessed in cats. A significant association was identified between MCS and mean radial SAP, but not mean coccygeal SAP. Muscle mass differs by anatomic region, which is the reason for assessing MCS at multiple anatomic sites.21,22 It is reasonable to surmise that sarcopenia could have differentially affected tissue mass at the coccygeal and radial artery measurement sites, resulting in these discordant findings.

The study reported here had several limitations. Headphones were not used for Doppler ultrasonographic measurements, although their use is highly recommended. The lack of a significant association between measurement site order and mean SAP readings suggested that changes in blood pressure attributable to the lack of headphone use had a similar impact at both sites. Despite the study design, unequal numbers of cats with various BCSs were enrolled, with only 9 of the 66 enrolled cats having a BCS of 1 or 2. This reflected the cat population from which subjects were recruited, most of which were privately owned healthy cats at an ideal BCS or obese.

The range in MCS in the present study was also limited, reflecting the high number of healthy cats. Similar challenges were identified in another study21 involving BCS and MCS assessment in cats. It is possible that diseases associated with hypertension, muscle wasting, and poor body condition, such as chronic kidney disease or hyperthyroidism, affected the accuracy of blood pressure measurement differently at 1 or both measurement sites; additional study of this possibility is warranted.

Another limitation of the present study was the limited enrollment of hypotensive cats. Because, in the authors’ experience, such cats often position themselves in lateral recumbency, we caution against extrapolating the results for SAP measurements at the coccygeal artery to ill cats. Finally, results obtained in the present study may not pertain to blood pressure measurements obtained by use of oscillometric techniques.

Given the findings of the study reported here, use of the coccygeal artery rather than the radial artery is recommended for Doppler ultrasonographic measurement of SAP in cats to avoid misdiagnosis of hypertension in normotensive cats. Muscle wasting appeared to affect radial artery measurements, but not coccygeal artery measurements. We therefore recommend monitoring and documenting MCS in cats undergoing repeated blood pressure measurement to ensure changes in this potential confounder are not overlooked. This is particularly important for cats with a temperament or conformation (eg, lack of a tail) that precludes use of the coccygeal artery site. Additional investigation is warranted into the interactions among SAP, MCS, BCS, and age in cats with diseases such as chronic kidney disease or hyperthyroidism.

Acknowledgments

Supported in part by the University of Tennessee College of Veterinary Medicine Center of Excellence in Livestock Diseases and Human Health Summer Research Program.

The authors thank Ann Reed for assistance with performance and interpretation of statistical analyses.

ABBREVIATIONS

BCS

Body condition score

MCS

Muscle condition score

SAP

Systolic arterial blood pressure

Footnotes

a.

Boiler M, Drobatz KJ, Silverstein DS. Evaluation of the influence of operator experience on blood pressure values measured by the Doppler technique in conscious cats (abstr). J Vet Emerg Crit Care 2003;13:160.

b.

MedCalc, version 15.8, MedCalc Software, Ostend, Belgium.

c.

Model 811-BTS, Parks Medical Electronics Inc, Aloha, Ore.

d.

Neonate disposable blood pressure cuff, sizes 1 to 3, Welch Allyn Inc, Skaneateles Falls, NY.

e.

SAS/STAT, version 9.2, SAS Institute Inc, Cary, NC.

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  • 16. Belew AM, Barlett T, Brown SA. Evaluation of the white-coat effect in cats. J Vet Intern Med 1999; 13: 134142.

  • 17. Caulkett NA, Cantwell SL, Houston DM. A comparison of indirect blood pressure monitoring techniques in the anesthetized cat. Vet Surg 1998; 27: 370377

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. Petric AD, Petra Z, Jerneja S, et al. Comparison of high definition oscillometric and Doppler ultrasonic devices for measuring blood pressure in anaesthetised cats. J Feline Med Surg 2010; 12: 731737

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Cannon MJ, Brett J. Comparison of how well conscious cats tolerate blood pressure measurement from the radial and coccygeal arteries. J Feline Med Surg 2012; 14: 906909.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. Bjornvad CR, Nielsen DH, Armstrong PJ, et al. Evaluation of a nine-point body condition scoring system in physically inactive pet cats. Am J Vet Res 2011; 72: 433437

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21. Michel KE, Anderson W, Cupp C, et al. Correlation of a feline muscle mass score with body composition determined by dual-energy X-ray absorptiometry. Br J Nutr 2011;106(suppl 1):S57S59.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22. Baldwin K, Bartges J, Buffington T, et al. AAHA nutritional assessment guidelines for dogs and cats. J Am Anim Hosp Assoc 2010; 46: 285296.

  • 23. Caney SMA. Non-invasive blood pressure measurement in cats. In Pract 2007; 29: 398403.

  • 24. Lin CH, Yan CJ, Lien YH, et al. Systolic blood pressure of clinically normal and conscious cats determined by an indirect Doppler method in a clinical setting. J Vet Med Sci 2006; 68: 827832.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25. Bodey AR, Sansom J. Epidemiological study of blood pressure in domestic cats. J Small Anim Pract 1998; 39: 567573.

  • 26. Rondeau DA, Mackalonis ME, Hess RS. Effect of body position on indirect measurement of systolic arterial blood pressure in dogs. J Am Vet Med Assoc 2013; 242: 15231527

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27. Bodey AR, Michell AR, Bovee KC, et al. Comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in conscious dogs. Res Vet Sci 1996; 61: 1721.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28. Bodey AR, Young LE, Bartram DH, et al. A comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in anaesthetised dogs, using tail and limb cuffs. Res Vet Sci 1994; 57: 265269.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29. Bijsmans ES, Jepson RE, Chang YM, et al. Changes in systolic blood pressure over time in healthy cats and cats with chronic kidney disease. J Vet Intern Med 2015; 29: 855861.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Individual values for mean SAP (3 consistent measurements/site/cat) measured via Doppler ultrasonic flow detector at the radial and coccygeal arteries of 66 privately owned cats.

  • Figure 2—

    Individual values for mean SAP (3 consistent measurements/site/cat) measured via Doppler ultrasonic flow detector at the radial (circles) and coccygeal (inverted triangles) arteries of 66 privately owned cats, grouped by BCS (5-point scale). Nine cats had a BCS of 1 or 2 (ribs visible or easily palpable with no or little palpable fat), 20 had a BCS of 3 (well proportioned), and 37 had a BCS of 4 or 5 (ribs not easily or not at all palpable with moderate to heavy fat cover).22

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    • Crossref
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  • 16. Belew AM, Barlett T, Brown SA. Evaluation of the white-coat effect in cats. J Vet Intern Med 1999; 13: 134142.

  • 17. Caulkett NA, Cantwell SL, Houston DM. A comparison of indirect blood pressure monitoring techniques in the anesthetized cat. Vet Surg 1998; 27: 370377

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. Petric AD, Petra Z, Jerneja S, et al. Comparison of high definition oscillometric and Doppler ultrasonic devices for measuring blood pressure in anaesthetised cats. J Feline Med Surg 2010; 12: 731737

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Cannon MJ, Brett J. Comparison of how well conscious cats tolerate blood pressure measurement from the radial and coccygeal arteries. J Feline Med Surg 2012; 14: 906909.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. Bjornvad CR, Nielsen DH, Armstrong PJ, et al. Evaluation of a nine-point body condition scoring system in physically inactive pet cats. Am J Vet Res 2011; 72: 433437

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21. Michel KE, Anderson W, Cupp C, et al. Correlation of a feline muscle mass score with body composition determined by dual-energy X-ray absorptiometry. Br J Nutr 2011;106(suppl 1):S57S59.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22. Baldwin K, Bartges J, Buffington T, et al. AAHA nutritional assessment guidelines for dogs and cats. J Am Anim Hosp Assoc 2010; 46: 285296.

  • 23. Caney SMA. Non-invasive blood pressure measurement in cats. In Pract 2007; 29: 398403.

  • 24. Lin CH, Yan CJ, Lien YH, et al. Systolic blood pressure of clinically normal and conscious cats determined by an indirect Doppler method in a clinical setting. J Vet Med Sci 2006; 68: 827832.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25. Bodey AR, Sansom J. Epidemiological study of blood pressure in domestic cats. J Small Anim Pract 1998; 39: 567573.

  • 26. Rondeau DA, Mackalonis ME, Hess RS. Effect of body position on indirect measurement of systolic arterial blood pressure in dogs. J Am Vet Med Assoc 2013; 242: 15231527

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27. Bodey AR, Michell AR, Bovee KC, et al. Comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in conscious dogs. Res Vet Sci 1996; 61: 1721.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28. Bodey AR, Young LE, Bartram DH, et al. A comparison of direct and indirect (oscillometric) measurements of arterial blood pressure in anaesthetised dogs, using tail and limb cuffs. Res Vet Sci 1994; 57: 265269.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29. Bijsmans ES, Jepson RE, Chang YM, et al. Changes in systolic blood pressure over time in healthy cats and cats with chronic kidney disease. J Vet Intern Med 2015; 29: 855861.

    • Crossref
    • Search Google Scholar
    • Export Citation

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