Evaluation of accuracy and reliability of indirect calorimetry for the measurement of resting energy expenditure in healthy dogs.

OBJECTIVE: To assess accuracy and reliability of open-flow indirect calorimetry in dogs. ANIMALS: 13 clinically normal dogs. PROCEDURE: In phase 1, oxygen consumption per kilogram of body weight (VO2/kg) was determined in 6 anesthetized dogs by use of open-flow indirect calorimetry before and after determination of VO2/kg by use of closed-circuit spirometry. In phase 2, four serial measurements of VO2 and carbon dioxide production (VCO2) were obtained in 7 awake dogs by use of indirect calorimetry on 2 consecutive days. Resting energy expenditure (REE) was calculated. RESULTS: Level of clinical agreement was acceptable between results of indirect calorimetry and spirometry. Mean VO2/kg determined by use of calorimetry before spirometry was significantly greater than that obtained after spirometry. In phase 2, intraclass correlation coefficients (ICC) for REE and VO2 were 0.779 and 0.786, respectively, when data from all 4 series were combined. When the first series was discounted, ICC increased to 0.904 and 0.894 for REE and VO2, respectively. The most reliable and least variable measures of REE and VO2 were obtained when the first 2 series were discounted. CONCLUSIONS AND CLINICAL RELEVANCE: Open-flow indirect calorimetry may be used clinically to obtain a measure of VO2 and an estimate of REE in dogs. Serial measurements of REE and VO2 in clinically normal dogs are reliable, but a 10-minute adaption period should be allowed, the first series of observations should be discounted, multiple serial measurements should be obtained, and REE.     

Postoperative effects of anesthesia and surgery on resting energy expenditure in horses as measured by indirect calorimetry

In this study, we aimed to define the effects of anesthesia and surgery on the resting energy expenditure of horses in experimental conditions. Six horses were used in a longitudinal study with 2 study periods: before and after anesthesia and surgery. Every horse underwent a standard 90-min ventral midline exploratory laparotomy. Oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured, with the use of a closed-circuit spirometry system, on 5 consecutive days immediately before and after the surgery. In 3 consecutive 5-min periods each day, the expired air was collected in a Collins spirometer. Samples of the expired gas were drawn from the spirometer through a drying column into O2 and CO2 analyzers. Resting energy expenditure was calculated as [(VO2 STPD*3.94) + (VCO2 STPD*1.11)]*1.44. This study showed that anesthesia and ventral midline exploratory laparotomy in experimental conditions increase the postoperative caloric demand in horses by an average of 1.0 Mcal/d, which represents approximately a 10% increase (P = 0.03). Additional studies in critically ill horses after surgery are needed to determine their caloric needs and to optimize their nutritional management.     

Effect of aerosolized albuterol sulfate on resting energy expenditure determined by use of open-flow indirect calorimetry in horses with recurrent airway obstruction

OBJECTIVE: To evaluate effects of sedation on stability of resistance of the respiratory system (RRS) and measures of resting energy expenditure (REE) by use of open-flow indirect calorimetry (IC) and treatment with aerosolized albuterol on REE in horses with recurrent airway obstruction (RAO). ANIMALS: 9 clinically normal horses and 8 horses with RAO. PROCEDURE: In phase 1, RRS was measured by using forced oscillometry (FOT) in 5 clinically normal horses before and after sedation with xylazine. In phase 2, REE was measured in 4 clinically normal horses between 20 and 25 minutes and again 35 to 40 minutes after sedation with xylazine. In phase 3, IC was performed between 20 and 25 minutes and FOT was performed between 30 and 35 minutes after xylazine administration in 8 horses with RAO; after administration of 450 microg of albuterol, IC and FOT were repeated. RESULTS: In phase 1, RRS values were significantly lower 5 and 10 minutes after sedation. In phase 2, diminishing sedation did not significantly affect REE. In phase 3, there was a significant decrease in mean RRS (1.15 +/- 0.25 vs 0.84 +/- 0.14 cm H20/L/s) and REE (30.68 +/- 17.89 vs 27.46 = 16.54 kcal/kg/d) after albuterol administration. CONCLUSIONS AND CLINICAL RELEVANCE: FOT and IC are useful in obtaining repeatable measurements of RRS and REE, respectively, in sedated horses. Concurrent bronchodilation and decreased REE after albuterol administration suggest that increased work of breathing as a result of airway obstruction may contribute to increased energy demands in horses with RAO.     

Rate of carbon dioxide production and energy expenditure in fed and food-deprived adult dogs determined by indirect calorimetry and isotopic methods

OBJECTIVE: To evaluate energy expenditure (EE) in dogs by estimating rate of CO2 production (rCO2). ANIMALS: 15 Beagles. PROCEDURE: Food was withheld for 24 hours, and all dogs received an IV infusion of 13C sodium bicarbonate for 8 hours. Breath samples were collected before infusion and at 30-minute intervals from 4 to 8 hours, and 13C enrichment in breath CO2 was measured, using gas chromatography-isotopic ratio mass spectrometry. Food was withheld from 6 dogs, and rCO2 and O2 consumption were measured, using a conventional indirect calorimeter. The CO2 production and O2 consumption were measured by use of indirect calorimetry in 6 other fed dogs that were injected with 2H2O and H2(18)O. Blood samples were collected before tracer injection, 4 hours later, and on days 4, 7, and 11. Deuterium and 18O enrichments in plasma water were determined. RESULTS: Mean rCO2 measured by indirect calorimetry was 516 +/- 34 and 410 +/- 16 micromol/kg(0.75)/min in 6 fed and 6 food-deprived dogs, respectively. The rCO2 calculated from 13C-bicarbonate dilution was 482 +/- 30 micromol/kg(0.75)/min. Mean rCO2 determined by use of the double-labeled water method was 1,036 +/- 46 mmol/kg(0.75)/d. Mean energy expenditure calculated from rCO2 determined by infusion of 13C bicarbonate, indirect calorimetry in fed and food-deprived dogs, and infusion of double-labeled water was 386 +/- 39, 379 +/- 25, 338 +/- 14, and 552 +/- 25 kJ/kg(0.75)/d, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Energy expenditure calculated by indirect calorimetry in unfed dogs can be considered representative of basal metabolic rate.     

The C bicarbonate dilution technique to determine energy expenditure in young bulls validated by indirect calorimetry

We explored the applicability of the ¹³C bicarbonate dilution technique for determination of energy expenditure (EE) in young bulls in comparison to whole body indirect calorimetry (IC). Twelve bulls of a F2 German Holstein x Charolais cross (4.5 months, 332 ± 16 kg BM) received a diet providing 1000 kJ ME d^− 1 kg BM^− 0.75 and 4.3 g crude protein d^− 1 kg BM^− 0.75. Bulls were housed in respiration chambers and received an intravenous bolus of NaH¹³CO₃ (A: 3 μmol kg BM^− 1 (n = 2), B: 7 μmol kg BM^− 1 (n = 4), C: 17.5 μmol kg BM^− 1 (n = 6), 99 at.% ¹³C) into the jugular vein to measure EE. Simultaneously, EE was determined by IC. After the ¹³C administration blood samples and breath gas were collected from the animals in the respiration chamber during a 24-h period (7.00–7.00 h). The recovery of ¹³C in breath CO₂ (% of ¹³C dose) was irrespective of NaH¹³CO₃ dose (A: 69.7 ± 2.7%, B: 70.5 ± 4.5%, C: 75.0 ± 4.9%; P > 0.05). Only small amounts of ¹³C were excreted in urine (3.4 ± 2.6%) and feces (2.0 ± 1.3%). The EE determined by the ¹³C bicarbonate method using breath and blood ¹³C recovery rates as correction factors was not different from that measured by IC (816 ± 81 [blood] or 827 ± 101 [breath] vs. 820 ± 90 kJ d^− 1 kg BM^− 0.75). Bland–Altman analysis showed a 95% confidence interval for EE of ± 99 and ± 109 kJ d^− 1 kg BM^− 0.75 based on blood and breath ¹³C recovery, respectively. In conclusion, the ¹³C bicarbonate dilution method is appropriate to obtain reliable estimates of EE in young bulls using blood CO₂ or breath CO₂ under standardized experimental conditions, i.e. in the fasting state.     

Bioavailability of suppository acetaminophen in healthy and hospitalized ill dogs

To determine the plasma pharmacokinetics of suppository acetaminophen (APAP) in healthy dogs and clinically ill dogs. This prospective study used six healthy client‐owned and 20 clinically ill hospitalized dogs. The healthy dogs were randomized by coin flip to receive APAP orally or as a suppository in crossover study design. Blood samples were collected up to 10 hr after APAP dosing. The hospitalized dogs were administered APAP as a suppository, and blood collected at 2 and 6 hr after dosing. Plasma samples were analyzed by ultra‐performance liquid chromatography with triple quadrupole mass spectrometry. In healthy dogs, oral APAP maximal concentration (C_MAX=2.69 μg/ml) was reached quickly (T_MAX=1.04 hr) and eliminated rapidly (T1/2 = 1.81 hr). Suppository APAP was rapidly, but variably absorbed (C_MAX=0.52 μg/ml T_MAX=0.67 hr) and eliminated (T_1/2 = 3.21 hr). The relative (to oral) fraction of the suppository dose absorbed was 30% (range <1%–67%). In hospitalized ill dogs, the suppository APAP mean plasma concentration at 2 hr and 6 hr was 1.317 μg/ml and 0.283 μg/ml. Nonlinear mixed‐effects modeling did not identify significant covariates affecting variability and was similar to noncompartmental results. Results supported that oral and suppository acetaminophen in healthy and clinical dogs did not reach or sustain concentrations associated with efficacy. Further studies performed on different doses are needed.     

Maintenance energy requirement variations determined by indirect calorimetry and feeding trials in light horses

Ten Standardbred horses were fed a mixed diet (60% hay + 40% concentrate) at a maintenance and 1.2 times maintenance over 2 three-month-periods in winter and summer feeding trials. Energy expenditure was measured also by indirect calorimetry in 4 of these horses. The DE and ME requirements for maintenance were calculated for zero energy gain in both cases. Energy requirements measured by feeding trial and by indirect calorimetry were consistent: 129 ± 10 and 132 ± 10 kcal ME/W^0.75.Ts respectively. Individnal variability of requirements was 8% in both methods. ME requirements were 9% higher in summer than in winter and difference between young and adult horses ranged from −3% to +11%.     

Comparison of P-wave dispersion in healthy dogs,dogs with chronic valvular disease and dogs with disturbances of supraventricular conduction

Background

P-wave dispersion (P_d) is a new ECG index used in human cardiology and veterinary medicine. It is defined as the difference between the maximum and the minimum P-wave duration recorded from multiple different ECG leads. So far no studies were performed assessing the importance of P-wave dispersion in dogs.

Methods

The current study was aimed at determining proper value of P_d in healthy dogs (group I), dogs with chronic valvular disease (group II) and dogs with disturbances of supraventricular conduction (group III). The tests were carried out in 53 healthy dogs, 23 dogs with chronic valvular disease and 12 dogs with disturbances of supraventricular conduction of various breeds, sexes and body weight from 1,5 to 80 kg, aged between 0,5 and 17 years, submitted to the ECG examination. ECG was acquired in dogs in a standing position with BTL SD-8 electrocardiographic device and analyzed once the recording was enlarged. P-wave duration was calculated in 9 ECG leads (I, II, III, aVR, aVL, aVF, V1, V2, V4) from 5 cardiac cycles.

Results

The proper P-wave dispersion in healthy dogs was determined at up to 24 ms. P-wave dispersion was statistically significant increased (p < 0.01) in dogs with chronic valvular disease and dogs with disturbances of supraventricular conduction. In dogs with the atrial enlargement the P-wave dispersion is also higher than in healthy dogs, although no significant correlation between the size of left atria and Pd was noticed (p = 0.1, r = 0,17).

Conclusions

The P-wave dispersion is a constant index in healthy dogs, that is why it can be used for evaluating P wave change in dogs with chronic valvular disease and in dogs with disturbances of supraventricular conduction.     

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.     

Comparison between auricular and standard rectal thermometers for the measurement of body temperature in dogs

Although the rectal mucosa remains the traditional site for measuring body temperature in dogs, an increasing number of clinicians have been using auricular temperature to estimate core body temperature. In this study, 88 mature healthy dogs had body temperatures measured with auricular and rectal thermometers. The mean temperature and confidence intervals were similar for each method, but Bland-Altman plots showed high biases and limits of agreement unacceptable for clinical purposes. The results indicate that auricular and rectal temperatures should not be interpreted interchangeably.     

Comparison of direct and indirect blood pressure measurements in anesthetized dogs.

The precision and accuracy of an indirect oscillometric blood pressure measurement technique (Dinamap 8100) was assessed in 11 anesthetized Beagle dogs weighing 8 to 11.5 kg. Direct blood pressure measurements were made by catheterization of the lingual artery, and simultaneous indirect measurements were determined by placing a cuff over the median artery (midradial area). Blood pressure measurements at 2 different planes of anesthesia (light and deep) were recorded in triplicate. At a light plane of anesthesia, the Dinamap 8100 underestimated diastolic and mean arterial pressure, and at a deep anesthetic plane overestimated systolic pressure. The indirect technique had good repeatability of systolic pressures. Regression analysis for the 2 techniques showed excellent correlation (r = 0.93). The results indicate that the indirect oscillometric blood pressure measurement technique provides a good estimate of systolic, diastolic, and mean arterial pressure in dogs weighing 8-11.5 kg.     

Comparison of direct and indirect tests for small intestinal bacterial overgrowth and antibiotic-responsive diarrhea in dogs

Controversy exists over the diagnosis of idiopathic small intestinal bacterial overgrowth (SIBO) in dogs and some clinicians use the term antibiotic-responsive diarrhea (ARD) in preference. However, whether such terms are interchangeable is not clear. To examine the relationship between duodenal bacterial numbers and a clinical response to antibiotics, SIBO and ARD were defined by nonoverlapping criteria. Quantitative duodenal juice bacteriology and indirect serum biochemical tests were used to assess small intestinal bacterial populations in 30 dogs with gastrointestinal disorders, including 9 with ARD. Serum total unconjugated bile acid (TUBA) concentrations were measured in all dogs, serum folate and cobalamin concentrations were measured in 29 of 30 dogs, and quantitative culture of duodenal juice was performed in 22 of 30 dogs. Serum TUBA concentrations also were measured in samples from 38 control dogs. Twenty of 22 affected (clinical) dogs in which quantitative bacteriology was performed were classified as having SIBO (>10(5) colony-forming units of total bacteria per milliliter of duodenal juice), but bacterial numbers did not differ significantly between dogs with ARD and dogs with other disorders. Increased folate (19/29), decreased cobalamin (16/ 29), or a combination (9/29) were common, but increased TUBA concentrations were documented in only 5 of 30 clinical dogs. Again, no significant differences were observed between dogs with ARD and those with other disorders, and a similar proportion (5/38) of controls had abnormally high TUBA concentrations. Finally, no significant differences were noted when duodenal bacteriology and TUBA concentrations were assessed before and during antibiotic therapy. These results question the utility of quantitative duodenal juice bacteriology and indirect biochemical marker tests for SIBO in the investigation of canine gastrointestinal disorders.     

Integrative analysis of indirect calorimetry and metabolomics profiling reveals alterations in energy metabolism between fed and fasted pigs

Background: Fasting is a simple metabolic strategy that is used to estimate the maintenance energy requirement where the energy supply for basic physiological functions is provided by the mobilization of body reserves.However, the underlying metabolic components of maintenance energy expenditure are not clear. This study investigated the differences in heat production(HP), respiratory quotient(RQ) and plasma metabolites in pigs in the fed and fasted state, using the techniques of indirect calorimetry and metabolomics.Methods: Nine barrows(45.2 ± 1.7 kg BW) were fed corn-soybean based meal diets and were kept in metabolism crates for a period of 14 d. After 7 d adaptation, pigs were transferred to respiratory chambers to determine HP and RQ based on indirect calorimetry. Pigs were fed the diet at 2,400 k J ME/(kg BW0.6·d) during d 8 to 12. The last 2 d were divided into 24 h fasting and 48 h fasting treatment, respectively. Plasma samples of each pig were collected from the anterior vena cava during the last 3 d(1 d while pigs were fed and 2 d during which they were fasted).The metabolites of plasma were determined by high-resolution mass spectrometry using a metabolomics approach.Results: Indirect calorimetry analysis revealed that HP and RQ were no significant difference between 24 h fasting and 48 h fasting, which were lower than those of fed state(P 0.01). The nitrogen concentration of urine tended to decrease with fasting(P = 0.054). Metabolomics analysis between the fed and fasted state revealed differences in15 compounds, most of which were not significantly different between 24 h fasting and 48 h fasting. Identified compounds were enriched in metabolic pathways related to linoleic acid metabolism, amino acid metabolism,sphingolipid metabolism, and pantothenate and Co A biosynthesis.Conclusion: These results suggest that the decreases in HP and RQ of growing pigs under fasting conditions were associated with the alterations of linoleic acid metabolism and amino acid metabolism. The integrative analysis also revealed that growing pigs under a 24-h fasting were more appropriate than a 48-h fasting to investigate the metabolic components of maintenance energy expenditure.