Pre-operative stress in dogs - a preliminary investigation of behavior and heart rate variability in healthy hospitalized dogs

OBJECTIVE: To assess pre-operative behavioral and physiological characteristics of healthy dogs hospitalized for elective surgery. STUDY DESIGN: Open clinical observational study. ANIMALS: Forty-one bitches hospitalized for elective ovariohysterectomy. METHODS: While undisturbed in a hospital cage, the behavior of the dog was recorded using a video camera and recorder. From the video recordings, various behavioral variables were registered. Simultaneous measurements were made on heart rates and heart rate variability (HRV) by use of an ambulatory electrocardiogram. In addition, the dog's response to human approach was noted. RESULTS: Different behavioral patterns were found in the dogs studied. Thirteen individuals were regarded as highly active, and were seen to bark or howl, manipulate the environment or attempt to flee vigorously. In 13 dogs (passive dogs) none of these activities occurred. Panting and displacement behaviors, such as snout licking, were observed in nearly all the animals monitored. In general, heart rates were higher and HRV lower with the most active individuals; however, the presence of physiological arousal could not be excluded in two animals with passive behaviors. To some extent, the behavior of the dog while undisturbed in the cage was reflected in the responses to a person entering the cage. CONCLUSIONS AND CLINICAL RELEVANCE: The different individual responses detected in this study raise an important question concerning their role and existence throughout the entire peri-operative period, especially during the post-anesthetic recovery phase when behavioral characteristics are commonly used to assess patient welfare. The results also emphasize the need for further investigations to explore the effects of pre-operative stressors on canine surgical patients, and the factors contributing to them.     

Behavioral and cardiac responses by dogs to physical human–dog contact

Measures of behavioral responses and cardiovascular parameters to evaluate and assess animal well-being are well established. A major aspect of companion animal well-being seems to originate from direct human–animal interaction. For pet dogs, the manner in which they obtain and respond to petting and hugs could interfere with the development of a pleasant human–dog companionship. Therefore, the purpose of this study was to evaluate cardiovascular responses by dogs to physical human–dog contact and to assess these physiological responses in relation to the dogs' behavioral responses. Noninvasive measurements of privately owned dogs' (N = 28) cardiovascular parameters and behavioral responses were carried out during 9 physical human–dog interactions (e.g., petting the dog on its back, holding a forepaw of the dog). The behavioral responses were grouped in categories, for example, redirected behavior, displacement activity, and appeasement gesture. The mean heart rate (HR) and 2 cardiac activity parameters, standard deviation of normal-to-normal R–R intervals (SDNN) and root mean square of successive heartbeat interval differences/SDNN (RMSSD/SDNN) ratio, differed significantly among the human–dog interactions. Petting and holding the dog around the head was associated with an increased SDNN. An increased vagal tone was the dogs' responses to being petted at the chest. Displacement activities correlated negatively with all cardiovascular parameters (HR, SDNN, RMSSD, and RMSSD/SDNN ratio). Appeasement gestures were positively correlated with HR and occurred less under an increased vagal tone. The behavioral strategies, that is, freezing (standing motionless with all legs on the floor) and withdrawal (moving backward without any agonistic display) were negatively associated with the cardiac activity parameters, RMSSD and RMSSD/SDNN ratio. The dogs' behavioral and physiological responses suggest that some common physical human–dog interactions perceived as unpleasant by dogs. Emphasis on human signaling in human–dog interactions encourages development of recommendations for pleasant and safe human–dog contact to enhance dogs' well-being and the human–dog relationship.     

Evaluation of the nociception–antinociception balance using the Parasympathetic Tone Activity index in dogs anaesthetized for castration

ObjectiveTo evaluate the performance of the Parasympathetic Tone Activity (PTA) index in assessing the nociception–antinociception balance in anaesthetized dogs undergoing castration.Study designProspective clinical study.AnimalsA group of 22 healthy client-owned dogs.MethodsThe dogs underwent general anaesthesia, with continuous monitoring of mean and instantaneous PTA (PTAm, PTAi), mean arterial pressure and heart rate. The values of these variables were divided according to the occurrence or absence of a haemodynamic reaction (HDR) at different time points: during surgical preparation, cutaneous incision, testicles extraction, cutaneous suture, after fentanyl administration, and after dexmedetomidine administration during recovery. Data were collected initially and 1, 3 and 5 minutes after each time point. The performance of the dynamic variation of the PTA (ΔPTA) to predict HDR or its resolution within 3 or 5 minutes was assessed using receiver operating characteristic (ROC) curves analysis. A p value < 0.05 was considered significant.ResultsDuring HDR, a decrease in PTAi (–34% and –31%) and PTAm (–26% and –30%) occurred at 3 (p = 0.005; p = 0.004) and 5 minutes (p = 0.001), respectively. After fentanyl administration, a decrease in haemodynamic variables occurred with a 45% increase in PTAi (p = 0.004). The ROC curve analysis of pooled data of the ΔPTAi for the prediction of HDR within 3 minutes indicated an area under the curve (AUC) of 0.70 (p = 0.0016) (threshold value: –16%). After fentanyl administration, the ROC curve analysis of ΔPTAi for the prediction of resolution of HDR within 3 minutes indicated an AUC of 0.69 (threshold value: +12%).Conclusions and clinical relevanceThe PTAi appears to be an interesting tool to assess the nociception–antinociception balance. However, further studies with a variety of clinical scenarios and anaesthesia protocols are required to conclude on its performance.     

Exposure to a dog elicits different cardiovascular and behavioral effects in pregnant and lactating goats

Background

Heart rate and plasma cortisol concentration are often used in evaluation of physiological reactions to stress and fear, but arterial blood pressure is rarely measured in farm animals. Goats are prey animals and can be expected to react strongly to a predator, especially when they have kids. We hypothesized that exposure to a dog elicits a flight response during pregnancy and a fight response when goats have kids to defend. Arterial blood pressure and heart rate should increase in both these cases, due to a synchronized discharge of the sympathetic nervous system.

Methods

Seven goats were exposed to a dog for 15 minutes at 12 ± 3 days before, and again at 10 ± 1 days after, parturition. Arterial blood pressure, heart rate, and activity were registered by telemetry. Behavioral data were collected during 5 minute sessions, followed by blood samples obtained via intrajugular catheters. Plasma cortisol concentration was analyzed by radioimmunoassay.

Results

At the appearance of the dog, the mean arterial blood pressure of the goats increased from 90 ± 8 to 111 ± 8 mmHg (p < 0.001) during pregnancy and from 96 ± 8 to 108 ± 8 mmHg during lactation (p < 0.001). Heart rate did not change at dog exposure during lactation, but increased from 117 ± 6 to 126 ± 10 beats/min (p < 0.01) during pregnancy. Dog exposure resulted in plasma cortisol concentration increasing from 17 ± 1 to 43 ± 7 nmol/l (p < 0.01) during pregnancy and from 21 ± 1 to 49 ± 6 nmol/l (p < 0.01) during lactation. In response to the dog, goats vocalized at a higher frequency and started to ruminate later during lactation compared to pregnancy.

Conclusions

When goats were exposed to a dog during pregnancy, their heart rate, blood pressure, and plasma cortisol increased, in contrast to lactation when only their blood pressure and plasma cortisol increased. However, when they were lactating, goats vocalized more and started to ruminate later compared to when they were pregnant.     

The effects of L-659,066, a peripheral alpha2-adrenoceptor antagonist, on dexmedetomidine-induced sedation and bradycardia in dogs

Objective  To investigate the influence of L-659,066, a peripheral α2-adrenoceptor antagonist, on dexmedetomidine-induced sedation and reduction in pulse rate (PR) in dogs.
Study design  Randomized, cross-over.
Animals  Six healthy laboratory Beagles.
Methods  All animals received dexmedetomidine (5 μg kg⁻¹ IV, DEX) alone or in combination with L-659,066 (250 μg kg⁻¹ IV, DEX + L) with a 7-day rest period between treatments. Sedation was assessed using a composite sedation score and PRs were recorded. Atipamezole (50 μg kg⁻¹ IM, ATI) was administered to reverse the sedation. Overnight Holter-monitoring was carried out to obtain a minimum heart rate (MHR) at rest.
Results  Bioequivalence was shown for clinical sedation between DEX and DEX + L. Heart rate was significantly higher with DEX + L during the period of sedation. Bioequivalence was demonstrated between MHR and PR in the DEX + L group during the period of sedation. Recoveries after ATI were uneventful.
Conclusions  L-659,066 did not affect the quality of dexmedetomidine-induced sedation whilst it attenuated the reduction in PR. Thus, L-659,066 could prove a useful adjunct to reduce the peripheral cardiovascular effects attributed to dexmedetomidine in dogs.
Clinical relevance  The clinical safety of α2-adrenoceptor agonists could be markedly improved with less peripheral cardiovascular effects.     

64‐MULTIDETECTOR COMPUTED TOMOGRAPHIC ANGIOGRAPHY OF THE CANINE CORONARY ARTERIES

Canine coronary artery angiography (CTA) was performed in four anesthetized healthy dogs using 64‐multidetector computed tomography. Esmolol, a β‐1 adrenergic receptor antagonist, and sodium nitroprusside, an arteriolar and venous dilator, were administered to enhance visualization of the coronary arteries by reducing heart rate and creating vasodilation. The left main coronary artery with its three main branches and the right coronary artery were visualized and subdivided in 13 segments for evaluation. Optimal reconstruction interval, expressed as percentage of the R‐to‐R interval, was determined at 5% in 2.9%, 35% in 1%, 75% in 21.2%, 85% in 43.3%, and 95% in 31.7% of the segments. Overall image quality was good in 41.3% of the segments and excellent in 14.4%. There was blur in 98.1%, motion in 17.3%, and stair step in 6.7% of the evaluated segments, but these artifacts did not interfere with anatomic depiction of the arteries. Cross‐sectional anatomy of the coronary arteries as evaluated from the coronary CTA agreed well with gross anatomic evaluation and published information. The use of esmolol did not lead to the target heart rate of 60–65 beats/min. Nitroprusside had no significant effect on visualized length or diameter of the coronary artery branches. Coronary CTA is useful for the anatomic depiction of coronary artery branches in the dog.