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.     

The effect of relaxing massage on heart rate and heart rate variability in purebred Arabian racehorses

The objective of this study was to assess the effect of relaxing massage on the heart rate (HR) and heart rate variability (HRV) in young racehorses during their first racing season. In the study, 72 Purebred Arabian racehorses were included. The study was implemented during the full race season. The horses from control and experimental groups were included in regular race training 6 days a week. The horses from the experimental group were additionally subject to the relaxing massage 3 days a week during the whole study. HR and HRV were assumed as indicators of the emotional state of the horses. The measurements were taken six times, every 4‐5 weeks. The HRV parameters were measured at rest, during grooming and saddling the horse and during warm‐up walking under a rider. The changes of the parameters throughout the season suggest that the relaxing massage may be effectively used to make the racehorses more relaxed and calm. Moreover, the horses from the experimental group had better race performance records.     

Comparison of heart rate and heart rate variability obtained by heart rate monitors and simultaneously recorded electrocardiogram signals in nonexercising horses

Heart rate (HR) and heart rate variability (HRV) are often determined with Polar heart rate monitors (HRMs; S810i; Polar, Kempele, Finland). The aims of this study were to compare data from horses obtained by Polar HRMs and a portable Televet electrocardiogram (ECG; 100 version 4.2.3; Kruuse, Marslev, Denmark) device and to determine appropriate recording times in horses (n = 14). Correlations were calculated and a Bland-Altman analysis was carried out to examine agreement between recording systems. For beat-to-beat (RR) interval, uncorrected and corrected data were highly correlated irrespective of the recording system and recording time (r > 0.99, P < 0.001). For HRV variables, standard deviation of RR interval and root mean square of successive RR intervals, correlations higher than 0.9 were obtained between uncorrected and corrected ECG but not Polar data. The RR interval, HR, and HRV from corrected Televet and Polar data at no time differed between the recording systems. However, with the increase in recording time, the RR interval decreased (P < 0.001). Thus, for comparisons, recording intervals of similar length should be chosen. Correlations among RR interval, HR, and HRV variables obtained by ECG and HRMs were highly significant at all recording times (r > 0.9, P < 0.001). Correlations increased with increasing recording time. Bland-Altman graphs showed a strong agreement between HRMs and ECG and mean RR intervals, HR, and HRV variables were close to identical. In conclusion, Polar HRMs are as adequate as ECG recordings in horses. Owing to a low HR in stationary horses, recording times below 2 minutes will underestimate changes in HR and HRV.     

Using heart rate to predict energy expenditure in large domestic dogs

The aim of this study was to establish heart rate as a measure of energy expenditure in large active kennel dogs (28 ± 3 kg bw). Therefore, the heart rate (HR)–oxygen consumption () relationship was analysed in Foxhound‐Boxer‐Ingelheim‐Labrador cross‐breds (FBI dogs) at rest and graded levels of exercise on a treadmill up to 60–65% of maximal aerobic capacity. To test for effects of training, HR and were measured in female dogs, before and after a training period, and after an adjacent training pause to test for reversibility of potential effects. Least squares regression was applied to describe the relationship between HR and . The applied training had no statistically significant effect on the HR– regression. A general regression line from all data collected was prepared to establish a general predictive equation for energy expenditure from HR in FBI dogs. The regression equation established in this study enables fast estimation of energy requirement for running activity. The equation is valid for large dogs weighing around 30 kg that run at ground level up to 15 km/h with a heart rate maximum of 190 bpm irrespective of the training level.     

Cortisol release,heart rate,and heart rate variability in transport-naive horses during repeated road transport

Domestic animals are often repeatedly exposed to the same anthropogenic stressors. Based on cortisol secretion and heart rate, it has been demonstrated that transport is stressful for horses, but so far, changes in this stress response with repeated road transport have not been reported. We determined salivary cortisol concentrations, fecal cortisol metabolites, cardiac beat-to-beat (RR) interval, and heart rate variability (HRV) in transport-naive horses (N = 8) transported 4 times over a standardized course of 200 km. Immunoreactive salivary cortisol concentrations always increased in response to transport (P < 0.001), but cortisol release decreased stepwise with each transport (P < 0.05). Concentrations of fecal cortisol metabolites increased from 55.1 ± 4.6 ng/g before the first transport to 161 ± 17 ng/g the morning after (P < 0.001). Subsequent transport did not cause further increases in fecal cortisol metabolites. In response to the first transport, mean RR interval decreased with loading of the horses and further with the onset of transport (1551 ± 23, 1304 ± 166, and 1101 ± 123 msec 1 d before, immediately preceeding, and after 60–90 min of transport, respectively; P < 0.05). Decreases in RR interval during subsequent transports became less pronounced (P < 0.001). Transport was associated with a short rise in the HRV variable standard deviation 2 (P < 0.001 except transport 1), indicating sympathetic activation. No consistent changes were found for other HRV variables. In conclusion, a transport-induced stress response in horses decreased with repeated transport, indicating that animals habituated to the situation, but an increased cortisol secretion remained detectable.     

Intratesticular and subcutaneous lidocaine alters the intraoperative haemodynamic responses and heart rate variability in male cats undergoing castration

ObjectiveTo evaluate the usefulness of intratesticular and subcutaneous lidocaine in alleviating the intraoperative nociceptive response to castration, measured by pulse rate (PR) and mean arterial pressure (MAP), and to test the applicability of heart rate variability (HRV) analysis in assessing this response.Study designRandomized, controlled, observer-blinded experimental trial.AnimalsThirty-nine healthy male cats admitted for castration.MethodsOne group received general anaesthesia and served as control group (GA), while the treatment group (LA) additionally received local anaesthesia (lidocaine 2 mg kg^?1) intratesticularly and subcutaneously. PR and MAP were recorded at anaesthesia baseline (T0), treatment (T1), incision left testicle (T2), traction on spermatic cord (T3), tightening of the autoligature and resection of the cord (T4), incision on the right side (T5), traction on spermatic cord (T6), and tightening of the autoligature and resection of cord (T7). HRV analysis was divided into three 5-minute intervals: baseline (H0), treatment (H1), and surgery (H2).ResultsThere were significant increases in PR and MAP for both groups during surgery from T3 onwards; however, the increase in the treatment group (LA) was significantly lower than for the control group (GA). For HRV analysis, significant differences were found between groups in the following parameters during surgery: TP (total power), VLF (very low frequency), SDNN (standard deviation of NN intervals [=the interval between two consecutive R-waves in the ECG]), and TI (triangular index), which were lower in the LA group. Mean NN was significantly lower in the GA group, whereas LF (low frequency) and LFn (low frequency, normalized value) were lower in the LA group. HF (high frequency) and HFn (high frequency, normalized value) decreased significantly from H1 to H2 in both groups.Conclusions and clinical relevanceThe study showed that the nociceptive response to surgery was alleviated by the use of intratesticular and subcutaneous lidocaine and that HRV analysis is a promising research tool to estimate intraoperative nociception in cats during general anaesthesia.     

Heart rate variability after horse trekking in leading and following horses

Horse trekking (HT) is having a stroll on a horse along a walking trail in a forest, field, and/or sandy beach. Generally in HT, horses exercise in tandem line outside the riding facilities. Because the leading horse will be confronted with stressors in the forefront, we hypothesized that the leading horse shows higher stress responses than the following one. In order to verify the hypothesis, we compared short‐term stress responses between each position in six horses. Exercise consisted of 15 min of ground riding and 45 min of HT with walking and trotting. Heart rate variability was analyzed for 5 min at 30, 60, and 90 min after the exercising period. There was no significant difference in heart rate during exercise between leading and following positions. The high frequency / low frequency power band of heart rate variability, an index of sympathetic nervous activity, after exercise, tended to be higher in the leading position than following one (P < 0.1). The result in this study can suggest that the leading horse was in a higher stressed state than the following horse after HT.     

Physiological effects of interactions between female dog owners with neuroticism and their dogs

The aim of this study was to investigate the physiological effects of the relationship between dog owners with neuroticism and their dogs using noninvasive procedures to measure urinary cortisol and heart rate variability (HRV). Owner personalities were tested via the NEO Five-Factor Inventory and this study focused only on the dimension of neuroticism with 12-item scales. The 24 participating owners and their dogs were randomly divided into experimental and control groups. Each participant and their dog stayed in the test room for 80 minutes. The behavioral test included 2 resting times (R1 and R2, respectively), 2 command-communication times, a separation time, and a free time. In the control group, the command-communication times were changed to noncommunication times. Each participant wore a chest heart rate transmitter and a wrist watch monitor (RS800CX; Polar Electro) during the experiment. HRV is a quantitative parameter of autonomic activity. The spectral analysis of HRV is divided into 2 major oscillatory components: the high-frequency (HF) domain, which reflects parasympathetic activity and the low-frequency (LF) domain, which reflects both sympathetic and parasympathetic activities. The LF to HF ratio reflects sympathetic activity. In the experimental group, the neuroticism scores showed a positive significant correlation with a change in the HF power and a negative correlation with the ratio of the change in the LF to HF ratio. No correlations were found in the control group. Next, all participants were divided into 2 groups according to the HRV in R1 and R2. One group included participants whose HF increased in R2, and the other included participants whose HF decreased in R2. The neuroticism scores were significantly higher in the experimental subjects whose HF increased in R2 than in those whose HF decreased in R2. High neuroticism scores indicate individuals that may be sensitive to daily stresses. Our results showed that a parasympathetic activation occurred in owners with high neuroticism scores 10 minutes after a command-communication interaction with their dogs. This suggests that daily command communication–based interactions with their dogs could improve the owner's health for the better.     

Evaluation of a technique to measure heart rate variability in anaesthetised cats

Analysis of heart rate (HR) and heart rate variability (HRV) are powerful tools to investigate cardiac diseases, but current methods, including 24-h Holter monitoring, can be cumbersome and may be compromised by movement artefact. A commercially available data capture and analysis system was used in anaesthetised healthy cats to measure HR and HRV during pharmacological manipulation of HR. Seven healthy cats were subjected to a randomised crossover study design with a 7 day washout period between two treatment groups, placebo and atenolol (1 mg/kg, IV), with the efficacy of atenolol to inhibit β₁ adrenoreceptors challenged by epinephrine. Statistical significance for the epinephrine challenge was set at P < 0.0027 (Holm–Bonferroni correction), whereas a level of significance of P < 0.05 was set for other variables.Analysis of the continuous electrocardiography (ECG) recordings showed that epinephrine challenge increased HR in the placebo group (P = 0.0003) but not in the atenolol group. The change in HR was greater in the placebo group than in the atenolol group (P = 0.0004). Therefore, compared to cats pre-treated with placebo, pre-treatment with atenolol significantly antagonised the tachycardia while not significantly affecting HRV. The increased HR in the placebo group following epinephrine challenge was consistent with a shift of the sympathovagal balance towards a predominantly sympathetic tone. However, the small (but not significant at the critical value) decrease in the normalised high-frequency component (HF_norm) in both groups of cats suggested that epinephrine induced a parasympathetic withdrawal in addition to sympathetic enhancement (increased normalised low frequency component or LF_norm). In conclusion, this model is a highly sensitive and repeatable model to investigate HRV in anaesthetised cats that would be useful in the laboratory setting for short-term investigation of cardiovascular disease and subtle responses to pharmacological agents in this species.     

Changes in cortisol release and heart rate variability in sport horses during long-distance road transport

It is widely accepted that transport is stressful for horses, but only a few studies are available involving horses that are transported regularly and are accustomed to transport. We determined salivary cortisol immunoreactivity (IR), fecal cortisol metabolites, beat-to-beat (RR) interval, and heart rate variability (HRV) in transport-experienced horses (N = 7) in response to a 2-d outbound road transport over 1370 km and 2-d return transport 8 d later. Salivary cortisol IR was low until 60 min before transport but had increased (P < 0.05) 30 min before loading. Transport caused a further marked increase (P < 0.001), but the response tended to decrease with each day of transport. Concentrations of fecal cortisol metabolites increased on the second day of both outbound and return transports and reached a maximum the following day (P < 0.001). During the first 90 min on Day 1 of outbound transport, mean RR interval decreased (P < 0.001). Standard deviations of RR interval (SDRR) decreased transiently (P < 0.01). The root mean square of successive RR differences (RMSSD) decreased at the beginning of the outbound and return transports (P < 0.01), reflecting reduced parasympathetic tone. On the first day of both outbound and return transports, a transient rise in geometric HRV variable standard deviation 2 (SD2) occurred (P < 0.01), indicating increased sympathetic activity. In conclusion, transport of experienced horses leads to increased cortisol release and changes in heart rate and HRV, which is indicative of stress. The degree of these changes tended to be most pronounced on the first day of both outbound and return transport.     

Efficacy of the Parasympathetic Tone Activity monitor to assess nociception in healthy dogs anaesthetized with propofol and sevoflurane

ObjectiveTo compare a Parasympathetic Tone Activity (PTA) monitor with cardiovascular changes in invasive mean arterial pressure (IMAP) and heart rate (HR) when evaluating the response to nociceptive stimuli in anaesthetized dogs.Study designProspective experimental study.AnimalsA group of nine (seven male and two female) adult Beagle dogs weighing 13.4 ± 1.5 kg (mean ± standard deviation).MethodsAnaesthesia was induced with propofol and maintained with sevoflurane in oxygen. Electrical stimuli of different nociceptive intensities were applied for 30 seconds. Stimuli were classified in each patient according to the response obtained (relevant change ≥ 20%) as low (no response), medium (PTA only) or high (PTA and IMAP/HR). Immediate and averaged values of PTA, IMAP and HR were recorded every second from 60 seconds before to 120 seconds after application of the nociceptive stimulus. Time to nociceptive response and peak response were evaluated with analysis of variance and t test.ResultsImmediate PTA baseline values did not differ significantly before application of the low, medium and high stimuli (73 ± 15, p = 0.966). Immediate PTA response was observed with the medium stimulus at 33 ± 7 seconds with a maximum decrease of 57 ± 13% at 69 ± 5 seconds. With the high stimulus, the immediate PTA response was of a similar magnitude to the medium stimulus with a response at 28 ± 7 seconds (p = 0.221) and a maximum decrease of 68 ± 15% (p = 0.115) at 72 ± 7 seconds (p = 0.436). The cardiovascular change occurred (22 ± 8 seconds) prior to the immediate PTA response (p = 0.032).Conclusions and clinical relevanceThe PTA monitor detected nociceptive stimuli at lower intensities than those eliciting cardiovascular changes. However, nociceptive stimuli of higher intensities provoked cardiovascular changes that occurred before a PTA response was observed.     

Influence of sickness condition on diurnal rhythms of heart rate and heart rate variability in cows

Parameters of heart rate variability would explain changes in heart rate during the disease status in cows and to evaluate whether such changes might provide a more sensitive and quantitative indicator of these conditions than crude indices. For this purpose, we recorded electrocardiograms for 24 hr using a Holter-type electrocardiograph and applied power spectral analysis of heart rate variability in both five clinically healthy and four hospitalized cows. The significant findings of the current investigation were that the diurnal variations of autonomic nervous function are abolished in cows that are sick. This abnormal rhythm was induced by predominant parasympathetic inhibition in these cows. Therefore, the heart rate variability may be a useful indicator of sickness condition in cows.     

Effect of restraint inside the transport vehicle on heart rate and heart rate variability in Thoroughbred horses

This study aimed to investigate the effect of transportation and restraint in a van on heart rate (HR) and HR variability in Thoroughbreds. Eight healthy Thoroughbreds were exposed to four conditions, each for a duration of 30 min: stall rest (REST), restraint inside a van (VAN), restraint inside a van with the engine running (V + E), and road transportation (TRANS). Electrocardiograms were recorded to determine HR, low-frequency (LF) power, high-frequency (HF) power, and LF/HF ratio. During TRANS, HR was significantly greater than during REST and V + E. There was a significant increase during VAN compared with REST. These results demonstrated that restraint inside the transport vehicle was one of the major stressors that may cause physiological changes during transportation.     

Assessment of glomerular filtration rate with dynamic computed tomography in normal Beagle dogs

The objective of our study was to determine individual and global glomerular filtration rates (GFRs) using dynamic renal computed tomography (CT) in Beagle dogs. Twenty-four healthy Beagle dogs were included in the experiment. Anesthesia was induced in all dogs by using propofol and isoflurane prior to CT examination. A single slice of the kidney was sequentially scanned after a bolus intravenous injection of contrast material (iohexol, 1 mL/kg, 300 mgI/mL). Time attenuation curves were created and contrast clearance per unit volume was calculated using a Patlak plot analysis. The CT-GFR was then determined based on the conversion of contrast clearance per unit volume to contrast clearance per body weight. At the renal hilum, CT-GFR values per unit renal volume (mL/min/mL) of the right and left kidneys were 0.69 ± 0.04 and 0.57 ± 0.05, respectively. No significant differences were found between the weight-adjusted CT-GFRs in either kidney at the same renal hilum (p = 0.747). The average global GFR was 4.21 ± 0.25 mL/min/kg and the whole kidney GFR was 33.43 ± 9.20 mL/min. CT-GFR techniques could be a practical way to separately measure GFR in each kidney for clinical and research purposes.     

The effect of anesthesia and surgery on heart rate variability in dogs

Heart rate variability (HRV) may be useful for objective assessment of stress and pain in animals. The objective of this study was to describe the effect of anesthesia and surgery on HRV in dogs. We hypothesized that surgery would decrease HRV to a greater degree and for a longer duration than anesthesia alone. Four healthy male dogs (29 ± 2 kg) were instrumented for ambulatory ECG monitoring. Continuous ECG data was obtained for 1 day prior to, and 6 days following anesthesia alone (ANES) or anesthesia plus unilateral stifle arthrotomy (ANSX). The anesthetic protocol included xylazine (0.5 mg kg^–1 IM), morphine (0.5 mg kg^–1 IM), atropine (0.04 mg kg^–1 IM), thiopental (10 mg kg^–1 IV) and isoflurane in oxygen. A single dose of morphine (0.5 mg kg^–1 IM) was administered at extubation. Time domain analysis of HRV was performed on 5 minutes epochs of artefact‐ and arrhythmia‐free ECG data obtained at 12 noon and 12 midnight on each of the seven experimental days. Mean RR interval, standard deviation of normal R‐R intervals (SDNN), and the standard deviation of successive differences in RR intervals (SDSD) were compared to baseline for ANES and ANSX. Pain scores obtained during the day were also evaluated. Significance was set at p < 0.01. There were no differences between groups for any baseline data. Mean RR interval did not differ from baseline on days 1–6 in ANES or ANSX. SDNN and SDSD values at noon were not different from baseline on days 1–6 in ANES or ANSX. At midnight on days 1 and 2, SDNN was significantly decreased from baseline in ANSX, and on day 1 a significant difference between groups existed. ANSX values of SDSD at midnight were significantly decreased from baseline and ANES on day 1. Pain scores for ANSX were significantly greater than baseline on days 1–3, and different from ANES on days 1–5. These results suggest that HRV is decreased following anesthesia plus surgery, and that changes in HRV may be associated with pain.