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Introduction

As the canine population is extremely heterogeneous, the values of blood pressure (ABP) are dependent on breed, age and sex, noting a significant difference in blood pressure among different breeds and groups of breeds (Sanan & Arslan 2007, Bright & Dentino 2002, Bodey & Michell 1996). Bodey & Michell (1996), shows that hunting dogs present higher values of ABP comparing to giant breeds that present lower values. The Irish Wolfhounds dogs, show systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures less when compared with other hunting dogs or other groups of breeds (Bright & Dentino 2002). It is still known that giant breed dogs are predisposed to cardiovascular disease (Sanan & Arslan 2007). The use of sedatives allows the accomplishment of the pressure examination in agitated dogs (Coulter & Keith 1984). For Hamlin et al. (1982), tranquilized dogs present reduction of the blood pressure in relation to those nonsedated, however, for a correct indirect evaluation, many times it is necessary to use chemical containment. The pressures standard in different breeds allows to identification cases of hypertension and arterial hypotension, beyond to be important its measurement in the cases of acute bleeding and for the diagnosis and treatment of cardiovascular and renal diseases (Sanan & Arslan 2007). The arterial hypertension is recognized currently as an illness in dogs and generally is associated with some systemic alteration as renal disease, hyperadrenocorticism, hypothyroidism and diabetes mellitus (Haberman et al. 2005, Littman 2004). Amongst the complications of the arterial hypertension, we can report the blindness, cardiovascular and neurologic complications, and progressive renal injury (Haberman et al. 2005). However, according to Rabelo et al. (2005), the casuistic of small animals with hypotensives alterations is frequent in the clinic, higher than hypertensives alterations. The main causes of hypotension are the hypovolemic shock, cardiac and renal diseases, hypoadrenocorticism, serious dehydration, sepsis, anaphylaxis and acidosis (Macintire 2004). The measurement of the ABP can be achieved through direct methods or through indirect methods: by Doppler and oscillometric methods (Bright & Dentino 2002, Vincent et al. 1993, Coulter & Keith 1984). Although the direct method is the gold standard of measurement of the pressure, the indirect methods can be carried through in the clinic and present good correlations with direct method (Haberman et al. 2005, Mano et al. 2002, Hamlin et al. 1982). The Boxer is a brachiocephalicus breed of medium size without blood pressure study in consulted literature. In such a way, the objective of this work is to evaluate and compare the measures of ABP in forelimb (FL) and hindlimb (HL) in healthy dogs of this breed, before and after the acepromazine administration, using the oscillometric method.

Materials and Methods

The study was conducted in 40 healthy Boxer. There were 19 males and 21 females, ranging from one to six years old and average weight of 27.18 ± 4.28 kg. The selected animals had been submitted to three consecutive measurements of SAP, DAP and MAP using the oscillometric Dixtal® DX 2010 device. The dogs were positioned in right lateral recumbency and the cuffs were placed in the tibial distal region and proximal regions of the radius and ulna, both in the left members. The width of the used cuffs corresponded 40% of the circumference of the member of the animal, as suggested for Valtonen & Eriksson (1970). After these procedures, each dog received acepromazine (Acepran 0.2% - Univet SA), in the dose of 0.03 mg/kg, intravenously. After ten minutes, new measures of ABP were collected in the same way described above. For evaluation of the data we used the analysis of the variance (ANOVA) and the test Tukey (p < 0.05%) for comparing the averages SAP and DAP before and after application of acepromazine. Moreover, the averages of the MAP between FL and HL had been compared before and after the application of the drug, for ANOVA (5%).

Results and Discussion

Although in the present study the pressure values are considered normal for the species (Table 1), we observed that when they was compared with other breeds usually used as classical models for studies of the hypertension, the Boxer dogs presented pressure values differentiated, presenting ABP lower than dogs of small breed. That is confirmed in a study with conscientious Beagle dogs, that used the oscillometric method for measurement of the ABP. These dogs had presented SAP of 150.2mmHg, DAP of 86.3mmHg and MAP of 109.2mmHg, when measures was performed in the HL. They had still presented SAP of 151.7mmHg, DAP of 88.4mmHg and MAP of 110.9mmHg, when the measurement was carried through in the tail (Haberman et al. 2005). In both places, SAP and MAP had been higher than the gotten ones in FL and HL before the application of the acepromazine, in this present study. Bodey & Michell (1996), affirms that because the canine population was highly heterogeneous, significant difference in the blood pressures between different groups of breeds is observed. The MAP of giant dogs of the Kangal breed, measures with oscillometric and Doppler methods in FL, is considered similar or higher when compared with the other giant breeds. However, this breed presents lower values of ABP comparing to those used as standard for canine hypertension (Sanan & Arslan 2007). Bodey & Michell (1996) had measured the ABP of some breeds of dogs of different size, using the oscillometric method, from the tail, FL or HL. As result, they described higher arterial pressures for those dogs of hunting, especially the Sight Hounds (SAP of 146.7mmHg, DAP of 83.8mmHg and MAP of 108mmHg). As the majority of dogs with hypertension presents high SAP (Stepien et. 2003), a evaluation of the ABP for Doppler method was made with healthy dogs of English Bull Terrier breed, obtained mean of SAP of 105mmHg, less than that observed in our study. In this study with English Bull Terriers, the measurements of the ABP had been below of the waited one, because SAP can vary according to breed and the presence of their owners (O'Leary et al. 2003). After the use of the tranquilizer was possible mild manual restraint for the accomplishment of the pressure examination, occurring less interference in the execution, like described for Coulter & Keith (1984), however had significant difference in the systolics, diastolics and means values pressures before and after the use of the acepromazine. Cavalcanti et al. (2005), had evaluated the peripheral arterial pressures and venous central pressure in dogs that had received acepromazine and also gotten a significant reduction. This can be explained by the main hemodynamic effect of the acepromazine that is the resultant arterial hypotension of the blockade of α-1-peripheral adrenergics receptors.

The average of arterial pressures in HL and FL, before the acepromazine, were statistical similar. The values were 104.84 and 105.87mmHg, respectively. However, after the administration of the drug the arterial pressures had diminished, (90.70mmHg and 95.66mmHg, respectively). Kallet et al. (1997) observed significant difference between measurements of FL and HL, when this procedure was carried through healthy dogs evaluated in veterinary clinical. However, this occurred probably for the adaptation of the dogs to the procedures of measure and not for differences of ABP in these regions (FL, HL). Therefore, when the measurements were carried through the dogs inside their houses, it was not observed. In a study developed by Haberman et al. (2005) using conscious Beagle dogs, the accuracy of different indirect methods for ABP measurements, compared with the direct method, was conducted and it was observed that the measures of the ABP for the oscillometric method in HL and tail, had been close to the direct method when comparing to the measures in FL. The same was observed when the Doppler method was used. In contrast of the human being, in dogs, the clinical signals associate to hypertension are difficult to be determined, being of great importance the correct measurement of blood pressure values for a more precise diagnosis and identification of subclinical hypertension (Sanan & Arslan 2007, Haberman et al. 2005, Remillard et al. 1991). Stepien et al. (2003) had evaluated different indirect methods of identification of hypertension in dogs from values obtained for invasive method. They observed that the measurement of the ABP of hypertensive dogs (considered from 180mmHg), using the oscillometric method performed in the HL was higher when compared to the measurement at the base of the tail. It still revealed superior when carried through Doppler method in FL. The identification of hypertension and the hypotension must be based, beyond the pressure evaluation, in the clinical signals and the presence or absence of other associated diseases (Stepien et al. 2003).

Table 1. Comparison between the systolics and diastolics arterial pressures, in Boxer dogs, before and after the administration of the acepromazine.

SPHL = average of the systolics pressures in the left hindlimb
SPFL = average of the systolics pressures in the left forelimb
DPHL = average of the diastolics pressures in the left hindlimb
DPFL = average of the diastolics pressures in the left forelimb
* Averages followed for same small letter, in the same column do not differ between itself for the test of Tukey, with a nominal level of significance of 5%.

Conclusion

The standardization of the ABP in the different breeds under mild sedation and in different places of measurement is an important foundation to identify alterations, mainly subtle, values obtained in clinical practice.

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