Retrospective Study: Assessment of Anesthetic Risk of Obese Patients
World Small Animal Veterinary Association World Congress Proceedings, 2009
C. Petry; A.L.B. Pereira; J.L. Lemos; A. Mira
Curitiba, PR, Brazil


Emerging disease in the clinic for small animals, obesity is considered a disease of multifactorial origin, which involve several factors: genetics, neuroendocrine, environmental and social (Jericó et al. 2006). The obesity can be defined as the body weight from 10 to 20% above ideal weight for a particular race, sex and species (Wolfsheimer 2004). Considering the evil role of obesity, it can be viewed as an excessive accumulation of body fat enough to compromise the normal physiological function or predispose the metabolic problems or surgical (Tilley & Smith 2003). It is also known that obesity and yours abnormalities increases in the risks and therefore anesthetics on mortality. Considering the importance of obesity in clinical medicine and surgery of small animals and the need for more detailed investigations, it is proposed that this study, the purpose of obtaining information about local anesthetic risks surrounding the obesity in animals subjected to various surgical techniques.

Materials and Methods

This was a retrospective study of 266 sheets of anesthetic dogs and cats undergoing general inhalational anesthesia for various surgical procedures. The chips have, in addition to the weight of the animal, data about age, sex and race, as well as control of heart rate, respiratory rate, rectal temperature, oxygen saturation, systolic blood pressure, diastolic blood pressure, mean arterial pressure and the presence of complications during the anesthetic procedure. The drugs used for the induction of anesthesia were etomidate or propofol and the maintenance were halothane or isoflurane. The animals were initially assessed for their body score and classified as obese and overweight were those who score 5 and 4, respectively, adopting the classification in which score 1 corresponds to the animal too lean and obese animal 5. Having made the measurement of body score, animals with scores 4 and 5 were evaluated for the presence of race and anesthetic complications during induction, maintenance and / or recovery, according to notes made in the schedule of anesthetic patient. The remaining animals were evaluated only with respect to the presence of anesthetic complications. The complications were divided into six subgroups: occurrence of hypotension, incidence of hypertension, occurrence of atrio-ventricular block (AVB) and / or premature ventricular contractions (PVC), respiratory complications (cyanosis, bronchoconstriction, pulmonary edema, hypoxia and / or laryngospasm), other events (tachycardia and / or bradycardia) and no complications. The results were analyzed using the chi-square method with Yates correction / Fischer, when necessary, considering the level of significance where p < 0.1.


Of the 266 chips analyzed, 19 to dogs and cats were obese or overweight, resulting in 7.14% of animals that were submitted to general anesthesia inhalation. Regarding breeds of dogs that were overweight or obesity, the most expressive were Beagle and Labrador, with 26% and 21% of the animals respectively. For dogs and cats and evaluated with body score 4 or 5, about 47.4% had hypotension during the anesthetic procedure. In other animals the percentage of occurrence of hypotension was 43.3%. Already the occurrence of hypertension was higher in overweight or obese animals (31.6%). Hypertension occurred in only 6.1% of animals with body score less than or equal to 3. The presence of AVB and PVC was also higher in the group of obese patients (10.5% and 3.2% in obese animals in the other), and respiratory complications (21.1% in obese patients and 7.3% in the other). Other complications (bradycardia and / or tachycardia) occurred in 10.5% of those considered obese and 18.6% of non-obese. Animals that have not suffered any anesthetic complications amounted to only 15.8% in patients with overweight, while in animals with body score 1, 2 or 3 this number was 40.5%, suggesting, in general, more risk of complications in animals that have some degree of overweight or obese. Followed by the percentage change in estimates that this risk is approximately 1.42 times more of an overweight or obese patients present some anesthetic complications that a patient with a body score less than or equal to 3. Considering the statistical analysis method based on chi-square there was statistical significance in the data related to respiratory complications (p = 0.0955), incidence of hypertension (p = 0004) and no complications (p = 0.0594). Other data showed no statistical significance.

Discussion and Conclusions

The proportion of obese animals in this study was lower than epidemiological data published both in North America (Crystal 2004) and in Brazil (Jericó & Scheffer 2002). However, this result is only the animals that underwent surgical procedures, not resulting in an overall value of the obese animals who attend the routine veterinary clinic. The Beagle and Labrador breeds as the most prone to obesity and overweight have corroborated with published work by Markwell & Butterwick (1994) and Jericó et al. (2006). The values found in the occurrence of hypotension approximate present themselves between the two groups, suggesting that this may be caused by the anesthetic used. The halothane and isoflurane may cause hypotension in greater and lesser degree, respectively. According Fantoni et al. (1999), the halothane depresses the sensitivity of baroreceptors and heart rate has little change in the duration of hypothermia and hypertension. Already a hypertension, according to August (1991), can occur in obese individuals because of the increase in preload thus leading to an increase in diastolic pressure of the left ventricle. Cardiorespiratory complications can be understood due to the restriction of ventilation and consequent respiratory depression and hypoxemia secondary to the accumulation of mediastinal fat and / or the extra weight on the chest wall and diaphragm. Moreover, the increase faringeanos tissue can cause upper airway obstruction during the premedication and / or induction (Ambrósio 2002). As assessment of the same chips and analysis found that the data suggest a greater risk of abnormalities in the patient anesthetic overweight or obese, the risk is estimated at approximately 1.42 times more of an overweight or obese patients present some anesthetic complications that a patient with a body score less than or equal to 3. It is also considered that the obese patients were at risk of developing hypertension and respiratory changes during the anesthetic procedure.


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Speaker Information
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C. Petry
Curitiba, PR, Brazil