Comparison of temperature readings from a percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer in equids

OBJECTIVE: To compare temperature readings from an implantable percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer, to identify factors that affect microchip readings, and to estimate the sensitivity and specificity of the microchip for fever detection. DESIGN: Prospective study. ANIMALS: 52 Welsh pony foals that were 6 to 10 months old and 30 Quarter Horses that were 2 years old. PROCEDURES: Data were collected in summer, winter, and fall in groups 1 (n = 23 ponies), 2 (29 ponies), and 3 (30 Quarter Horses), respectively. Temperature readings from a digital rectal thermometer and a percutaneous thermal sensing microchip as well as ambient temperature were recorded daily for 17, 23, and 19 days in groups 1 through 3, respectively. Effects of ambient temperature and rectal temperature on thermal sensor readings were estimated. Sensitivity and specificity of the thermal sensor for detection of fever (rectal temperature, >or= 38.9 degrees C [102 degrees F]) were estimated separately for data collection at ambient temperatures 15.6 degrees C. RESULTS: Mean ambient temperatures were 29.0 degrees C (84.2 degrees F), -2.7 degrees C (27.1 degrees F), and 10.4 degrees C (50.8 degrees F) for groups 1 through 3, respectively. Thermal sensor readings varied with ambient temperature and rectal temperature. Rectal temperatures ranged from 36.2 degrees to 41.7 degrees C (97.2 degrees to 107 degrees F), whereas thermal sensor temperature readings ranged from 23.9 degrees (75 degrees F) to 42.2 degrees C (75 degrees to 108 degrees F). Sensitivity for fever detection was 87.4%, 53.3%, and 58.3% in groups 1 to 3, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The thermal sensor appeared to have potential use for initial screening of body temperature in equids at ambient temperatures > 15.6 degrees C.     

Physiologic responses in healthy Labrador Retrievers during field trial training and competition

Ten healthy Labrador Retrievers (4 females and 6 males aged 3-6.5 years [mean, 4.5 years]) training with a professional trainer were studied. The dogs were in training during the entire study. Dogs were monitored within 5 minutes after retrieving birds on land and in water on 2 consecutive days during training and on 2 consecutive days at the Atlanta Retriever Club Fall Field Trial. Baseline samples were taken in the morning on a separate day before the dogs were loaded onto a truck. Venous samples were analyzed with a portable blood analyzer. Measurements included hematocrit, sodium, potassium, chloride, blood urea nitrogen (BUN), glucose, lactate, blood pH, Pco2, Po2, HCO3, and TCO2 plus rectal temperature, pulse rate, and respiratory rate. Ambient temperatures were recorded. Distances and times were estimated. Compared to baseline, significant increases occurred in rectal temperature, pulse rate, respiratory rate, chloride, lactate, and pH postexercise (P < .05): sodium, potassium, BUN, Pco2, and TCO2 were significantly decreased postexercise. Blood pH was markedly higher after retrieves on land than after retrieves in water. Estimated mean speeds were 11.4 mph (18.3 km/h) during a triple retrieve on land and 5.6 mph (9.0 km/h) during a retrieve in water. Maximal ambient temperatures were 84-86 degrees F (29-30 degrees C). In summary, Labrador Retrievers training with a professional trainer had evidence of hyperthermia, respiratory alkalosis, hypocapnia, and mild metabolic acidosis monitored within 5 minutes postexercise during training and field trial competition when maximal ambient temperatures were 85 degrees F (29 degrees C). The results provide a baseline against which physiologic responses of dogs with poor performance can be compared.     

Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high-ambient-temperature conditions

OBJECTIVE: To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures. ANIMALS: 16 Labrador Retrievers. PROCEDURES: At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2 degrees to 29.4 degrees C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (< or = 21 degrees C and > 21 degrees C) on each variable. RESULTS: Compared with findings at ambient temperatures < or = 21 degrees C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21 degrees C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29 degrees C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs. CONCLUSIONS AND CLINICAL RELEVANCE: When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21 degrees C.     

Hoof and distal limb surface temperature in the normal pony under constant and changing ambient temperatures.

Forelimb surface temperatures were continuously monitored in four clinically normal ponies exposed to: (i) constant ambient temperature; (ii) a biphasic change in ambient temperature; and (iii) an incremental increase in ambient temperature. Limb surface temperatures were recorded at the hoof, metacarpus and forearm, and rectal temperature was also measured. Under constant ambient temperature, limb surface temperatures remained relatively constant. A pyrexic episode occurred in one pony under constant ambient temperature conditions and was characterised by an onset phase in which rectal temperature gradually increased while limb surface temperatures concurrently decreased; a plateau phase in which rectal temperature was elevated but essentially constant although limb surface temperatures rose dramatically; and a febrilytic phase in which limb surface temperatures remained elevated while rectal temperature gradually decreased. A biphasic change in ambient temperature produced corresponding changes in limb surface temperature, but limb surface temperatures were less stable at the lower ambient temperatures. Surface temperature responses to incremental increases in ambient temperature were dependent on the baseline ambient temperature (before increase), and dramatic, spontaneous increases in limb surface temperatures were observed. Rectal temperatures in the normal animals remained relatively constant under all three ambient temperature regimens. It was concluded that clinical interpretation of limb surface temperatures in ponies required an awareness of ambient temperature conditions. For evaluation of vasodilator agents, constant ambient temperatures of at least less than 18 degrees C are suggested, and constant ambient temperatures exceeding 20 degrees C are recommended for the evaluation of vasoconstrictor agents.     

Adaptability of buffaloes to climatic stress, as assessed by physiological reactions

Among the physiological reactions to climate, the haematocrit value had a tendency to increase in the hotter months, though the increase observed was within physiological limits. Rectal temperature did not change to significantly higher levels, during the months with average ambient temperatures in the region of 25.1-31.6 degrees C. Similarly, pulse rates, too, increased in parallel to rising ambient temperatures.     

Post-anesthetic hyperthermia in cats

OBJECTIVE: To assess whether administration of hydromorphone and, or ketamine are associated with post-anesthetic hyperthermia in cats undergoing routine surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Forty healthy, adult cats undergoing ovariohysterectomy (OVH), castration, or declaw surgery. MATERIALS AND METHODS: Each cat was assigned randomly to one of four groups (n = 10). For pre-anesthetic medication, all cats received subcutaneous (SC) glycopyrrolate (0.01 mg kg(-1)) and acepromazine (0.02 mg kg(-1)) and either hydromorphone (0.1 mg kg(-1) SC) or medetomidine (7.5 microg kg(-1) SC). Anesthesia was induced with either diazepam (0.1 mg kg(-1)) and ketamine (5 mg kg(-1)) or propofol (6 mg kg(-1) injected to effect). Group 1 (HDK) received hydromorphone and diazepam-ketamine. Group 2 (HP) received hydromorphone and propofol. Group 3 (MDK) received medetomidine and diazepam-ketamine. Group 4 (MP) received medetomidine and propofol. Rectal temperature was measured before drugs were given, at tracheal extubation and at hourly intervals for 5 hours thereafter. RESULTS: During the 5 hours after anesthesia and surgery, at least one cat in every group had a rectal temperature >39.2 degrees C (102.5 degrees F). The percentage of observations for which a cat's temperature exceeded its pre-anesthetic temperature in groups HDK, HP, MDK, and MP were 86%, 80%, 25%, and 34%, respectively. Maximum temperatures in groups HDK, HP, MDK, and MP were 41.6 degrees C (107.0 degrees F), 40.3 degrees C (104.2 degrees F), 39.2 degrees C (102.6 degrees F), and 40.1 degrees C (104.1 degrees F), respectively. By 5 hours after tracheal extubation there were no differences in temperature between the treatment groups. CONCLUSION: For up to 5 hours following anesthesia and surgery, cats might have body temperatures that exceed their pre-anesthesia body temperatures. The use of hydromorphone is associated with post-anesthetic hyperthermia. However, hyperthermia may occur when other drugs are used. CLINICAL RELEVANCE: Cats given hydromorphone should be closely monitored for hyperthermia following anesthesia and surgery.     

Resting rectal temperature of Vietnamese potbellied pigs.

OBJECTIVE: To determine resting rectal temperatures of Vietnamese potbellied pigs. DESIGN: Prospective clinical trial. ANIMALS: 85 potbellied pigs on a single farm and 27 potbellied pigs examined at a veterinary teaching hospital for routine veterinary care. PROCEDURE: Rectal temperatures of the potbellied pigs on a farm were measured during the morning, afternoon, and evening. Rectal temperatures at the time of initial examination were obtained from medical records for the potbellied pigs examined at the hospital. RESULTS: Mean rectal temperatures for both groups of potbellied pigs were the same. Overall unadjusted mean +/- SD rectal temperature was 37.6 +/- 0.8 C (99.7 +/- 1.5 F; range, 35.1 to 39.6 C [95.2 to 103.3 F]). However, diurnal variation in rectal temperature was found among the farm population of potbellied pigs. After adjustment for age and repeated sampling, rectal temperatures recorded during the morning were found to be significantly lower than temperatures recorded during the afternoon and evening (mean difference, 0.5 and 0.9 C [0.9 and 1.6 F], respectively), and rectal temperatures recorded during the afternoon were found to be significantly lower than temperatures recorded during the evening (mean difference, 0.4 C [0.7 F]). There was a significant inverse linear relationship between age and rectal temperature. CONCLUSIONS AND CLINICAL RELEVANCE: Rectal temperatures of Vietnamese potbellied pigs may be lower than the lower limit of the reference range reported for domestic pigs. Because of diurnal variation in rectal temperatures, it is important to compare temperatures obtained at the same time of day when assessing patients.     

Effects of ear type, sex, age, body weight, and climate on temperatures in the external acoustic meatus of dogs.

OBJECTIVE: To investigate effects of ear type, sex, age, body weight, and ambient climatic conditions on external acoustic meatus (external ear canal) temperatures in dogs. ANIMALS: 650 dogs without clinical signs of ear disease. PROCEDURE: Dogs were assigned to 5 groups on the basis of auricular conformation and amount of hair in the external ear canal and 4 groups on the basis of body weight or age. External ear canal temperatures (EECT) were measured, using an infrared thermometer. Mean EECT determined for each group were compared to evaluate effects of ear type, age, weight, and sex, and EECT measured at different ambient temperatures and humidities were compared to determine climatic effects. RESULTS: Dogs with hirsute ear canals had significantly lower EECT than dogs with hairless ear canals, whereas significant differences were not detected between dogs with erect and pendulous auricles. Dogs < 6 years old had higher EECT than older dogs, and dogs that weighed < 6 kg had lower EECT than larger dogs. External ear canal temperatures measured when ambient temperatures were < 25 C were less than those measured at warmer temperatures. Sex and relative humidity did not affect EECT CONCLUSIONS AND CLINICAL RELEVANCE: EECT of dogs without ear disease were affected by weight and age, amount of hair in the external ear canal, and ambient temperature. However, hirsute ears had lower, not higher, EECT than hairless ears, suggesting that EECT may play less of a role in the development of otitis externa than believed.     

Responses to heat stress in commercial and local broiler stocks. 1. Performance traits.

1. This study investigated effects of conditioning at 5 d of age and food restriction during a hot period on responses to prolonged heat stress of two fast (G1 and G2) and one slower-growing (G3) broiler stocks. 2. Chicks from each stock were divided into 3 groups: control, conditioned (chicks exposed to 36 degrees C for 24 h at 5 d of age) and food restricted (during the heat stress food was withdrawn 2 h before the hot period and chicks were fed between 17.00 and 08.00 h). Prolonged heat stress was induced daily from 28 to 49 d by heating until the ambient temperature reached 32 degrees to 35 degrees C between 10.00 and 17.00 h. 3. Body weights, mortality and rectal temperatures were lower and food conversion higher for stock G3 than G1 or G2. 4. Management procedures used in this study improved food conversion and lowered mortality without affecting body weight. Rectal temperatures of the treated groups were similar to those of the controls.     

Effects of storage time and temperature on pH,specific gravity,and crystal formation in urine samples from dogs and cats

OBJECTIVE: To determine effects of storage temperature and time on pH and specific gravity of and number and size of crystals in urine samples from dogs and cats. DESIGN: Randomized complete block design. ANIMALS: 31 dogs and 8 cats. PROCEDURE: Aliquots of each urine sample were analyzed within 60 minutes of collection or after storage at room or refrigeration temperatures (20 vs 6 degrees C [68 vs 43 degrees F]) for 6 or 24 hours. RESULTS: Crystals formed in samples from 11 of 39 (28%) animals. Calcium oxalate (CaOx) crystals formed in vitro in samples from 1 cat and 8 dogs. Magnesium ammonium phosphate (MAP) crystals formed in vitro in samples from 2 dogs. Compared with aliquots stored at room temperature, refrigeration increased the number and size of crystals that formed in vitro; however, the increase in number and size of MAP crystals in stored urine samples was not significant. Increased storage time and decreased storage temperature were associated with a significant increase in number of CaOx crystals formed. Greater numbers of crystals formed in urine aliquots stored for 24 hours than in aliquots stored for 6 hours. Storage time and temperature did not have a significant effect on pH or specific gravity. CONCLUSIONS AND CLINICAL RELEVANCE: Urine samples should be analyzed within 60 minutes of collection to minimize temperature- and time-dependent effects on in vitro crystal formation. Presence of crystals observed in stored samples should be validated by reevaluation of fresh urine.     

Postanesthetic hyperthermia in cats: a retrospective comparison between hydromorphone and buprenorphine

OBJECTIVE: To determine the prevalence of postanesthetic hyperthermia [rectal temperature >40 degrees C (104 degrees F)] in a clinical population of cats. STUDY DESIGN: Retrospective study. ANIMAL POPULATION: One hundred and twenty-five cats with an age range of 2 months to 16.1 years, and weighing 3.9 +/- 1.5 kg. MATERIALS AND METHODS: Data were obtained from the medical records of 125 cats that underwent general anesthesia. Information on perioperative rectal temperatures, breed, sex, weight, surgical procedure, anesthetic time, surgery time, anesthetic and analgesic drugs were retrieved. STATISTICAL ANALYSES: Five groups of cats were compared; group 1 (n = 15) received acepromazine and no opioids; group 2 (n = 17) received acepromazine and buprenorphine; group 3 (n = 19) received acepromazine, buprenorphine and ketoprofen; group 4 (n = 45) received acepromazine and hydromorphone and group 5 (n = 29) received acepromazine, hydromorphone and ketoprofen. Data conformed to a split-plot repeated measures analysis of variance and was analyzed using SAS PROC MIXED. Post hoc tests were by means of Bonferroni t-test; < or = 0.05 was considered significant. RESULTS: Rectal temperature was significantly decreased in all groups at the end of anesthesia. Rectal temperature was significantly elevated at 1, 1.5, 2, 3, 4 and 5 hours after the end of anesthesia in group 4, and at 2, 3 and 4 hours in group 5. Sixty-four percent of cats in group 4 and 69% in group 5 had rectal temperatures >40 degrees C (104 degrees F) at one or more times in the postanesthetic period. The highest temperature recorded was 42.5 degrees C (108.5 degrees F) in one cat in group 4. Mean rectal temperature did not exceed the preoperative temperature at any time during the postanesthetic period in group 1, 2 and 3 animals. CONCLUSIONS: This study indicates an association between hyperthermia and perioperative administration of hydromorphone in cats. CLINICAL RELEVANCE: When hydromorphone is used in cats their body temperature should be closely monitored.     

Effect of dietary amino acids and metabolisable energy on the performance of broilers kept at high temperatures

Increasing dietary metabolisable energy (ME) at particular amino acid: ME ratios significantly improved growth and food utilisation of broilers kept at moderate (18 to 26 degrees C) and high (25 to 35 degrees C) ambient temperatures during the finishing period from 22 d of age. The optimum amino acid: ME ratio varied with dietary ME concentration in the hot, but not in the moderate environment. Relatively greater increases in food intake and growth rate occurred in the hot environment when dietary ME was increased and the amino acid: ME ratio was reduced. The minimum rate of food intake did not coincide with the period of maximum temperature. Increasing the dietary protein at particular ME concentrations had little or no effect on the food intake and growth rate of birds kept at high temperatures. Supplementation with dietary fat had no beneficial effect on performance at high temperatures. The rectal temperatures of birds in the hot environment increased with age and, towards the end of the finishing period, when higher energy diets were fed.     

Effects of air velocity on convective and radiant heat transfer from domestic fowls at environmental temperatures of 20 degrees and 30 degrees C

The effects of air movement upon sensible heat loss from individual birds at ambient temperatures of 20 degrees and 30 degrees C were determined by partitional calorimetry using a newly developed wind tunnel calorimeter. The relationship between area specific convective heat loss (W/m2) and air velocity (in the range 0.3 to 1.05 m/s) was described by y = 56.5 + 16.9 log x at an air temperature of 20 degrees C, but at 30 degrees C convective heat loss increased linearly with air speed (y = 11.8 + 40.1 x). At 20 degrees C sensible heat exchange (W/m2) was related to air velocity by y = 70.6 exp (0.099 x) and by y = 41.4 + 25.9 x at 30 degrees C, the proportional increase with air speed being greater at the higher temperature. The differences in the effects of air movement on convective cooling and sensible heat loss at 20 degrees and 30 degrees C reflect the thermoregulatory responses of the birds, induced by the thermal demands of the environment.     

Effect of two thermal regimes on the muscle growth dynamics of sea bass larvae,Dicentrarchus labrax L

Muscle growth was studied in larvae of sea bass, Dicentrarchus labrax L., reared at two temperatures: real ambient temperature ( congruent with 15 degrees C during vitelline phase and increased gradually) and 19 degrees C from fertilization until the end of larval development. Muscle cellularity, body length and body weight were measured. Early temperature influenced larval development and so, pre-larval phase finished earlier at 19 degrees C than at ambient temperature (4 and 6 days, respectively). Temperature also affected muscle growth such that at hatching and at mouth opening hypertrophy of muscle fibres was greater at 19 degrees C (P < 0.05), whereas hyperplasia was similar in both groups. After 25 days, the cross-sectional area of the white muscle was greater at 19 degrees C (P < 0.05), which was mainly associated with a higher proliferation of new white muscle fibres. At this stage the body length was also higher at 19 degrees C. Metamorphosis finished earlier in fish reared at 19 degrees C (52 days) than at natural temperature (82 days). At this developmental stage body length and cross-sectional area of the myotome were similar in both groups. However, muscle cellularity differed between groups. Thus, hypertrophy of muscle fibres was higher in fish reared at ambient temperature (P < 0.05), whereas proliferation of new muscle fibres was higher at 19 degrees C (P > 0.05).     

Temperature effect on muscle growth of the axial musculature of the sea bass (Dicentrarchus labrax L.)

In order to determine the temperature effect on the axial muscle growth of sea bass, a stock of larvae was subjected to the following incubation and cultivation temperatures, respectively: 15 degrees C/ambient, 15/17 degrees C, 17 degrees C/ambient and 17/17 degrees C. In all groups the cross-sectional area of white and red muscles and the number and average area of the white and red muscle fibres were quantified. Results showed that the embryonic period, pre-larval phase and the end of metamorphosis were accelerated at higher temperatures. During the endogenous feeding period, muscle growth took place by fibrillar hypertrophy, and was not influenced by the temperature. Thereafter (external feeding) muscular hyperplasia began, and growth of all the muscular parameters was favoured by the effect of high incubation and cultivation temperatures, with the latter having higher influence. High incubation temperature had an slight effect on muscle growth and body length, which was only observed from 15 days. Metamorphosis finished at 3 +/- 0.4 cm in all the larvae, but this length was earlier reached at higher temperatures. At 120 days, the largest growth was obtained in the larvae maintained at a higher temperature.     

Acid-base status in the blood of domestic pigs during exhausting locomotor stress of small and medium intensity]

Twenty-two fattening pigs were stressed until their rectal temperatures had reached 42 degrees C. The means of stress included walking on moving conveyor belt at ambient temperatures between 22 degrees C and 27 degrees C and relative humidities between 69 and 98%, belt speeds of 0.7 m/s, 1.3 m/s or 0.7 m/s, and stimulation by means of a forcing rod. Rectal temperature, respiratory frequency, lactic acid level in blood plasma, pH, as well as pCO2 and base excess in the blood were measured prior to, during, and after stressing. Gasping was strongly pronounced due to severe alkalisis, but it was somewhat mitigated on running on the belt with exposure to additional stress on account of lactic acid accumulation in the plasma.     

Comparison of peripheral and core temperatures in anesthetized horses.

OBJECTIVE: To examine temporal patterns of rectal, nasal, groin, and skin temperatures measured in adult horses undergoing general anesthesia and to determine accuracy and precision of temperatures at these sites, compared with core temperature. ANIMALS: 5 healthy adult horses. PROCEDURE: Induction, maintenance of, and recovery from general anesthesia were performed in an air-conditioned surgical suite. Room temperature and relative humidity were approximately 21 C and 40%, respectively. Anesthesia was maintained for 2.5 hours, and body temperatures were measured and recorded every 5 minutes. Mean values were compared by use of ANOVA for repeated measures. Correlation coefficients for linear regressions of site temperature versus core temperature at 30-minute intervals were used to evaluate precision. RESULTS: Rectal temperature decreased in a linear manner, similar to core temperature. Nasal, groin, and skin temperatures followed a biphasic pattern; they sharply increased initially, peaked, then decreased at a rate similar to that of core temperatures. Rectal temperature always accurately reflected core temperature. Initial significant differences between core temperature and nasal, groin, or skin temperature disappeared as peripheral site temperatures approached peak values. Precision of core temperature estimation was generally poor for rectal, groin, and skin temperatures but was high (r > 0.90) after the first hour of anesthesia. CONCLUSION: Anesthesia-induced core heat redistribution develops with minimal effect on core temperature. Rectal temperature can accurately reflect core temperature.     

Evaluation of thermographic imaging of the limbs of healthy dogs

OBJECTIVE: To describe a thermographic imaging protocol, identify normal thermographic patterns (ie, color map reflecting the skin temperature distribution) for various regions of interest (ROIs) of dog limbs, and evaluate effects of clipping the coat on thermographic patterns and limb temperature in healthy dogs. ANIMALS: 10 healthy dogs. PROCEDURES: Each dog was thermographically evaluated in the same room (ambient temperature, 21 degrees C) via ROIs that included cranial and caudal views of the body, full lateral body views, full views of the limbs, and views of various limb regions. After initial imaging, the coat was clipped on the forelimbs and hind limbs only. Each dog was then evaluated 15 and 60 minutes and 24 hours after clipping by use of the same protocol. RESULTS: For each ROI within a category (intact coat and each time point after clipping), mean temperatures were similar among the 10 dogs. Pairwise comparisons for 15 and 60 minutes and 24 hours established patterns of temperature stabilization among the 3 time points. Temperatures did not differ significantly between the left and right limbs. There was a mean success rate of 75% for use of image pattern analysis for recognition of similar thermographic patterns in the forelimbs and hind limbs. CONCLUSIONS AND CLINICAL RELEVANCE: Thermography can be a viable, noninvasive imaging modality that provides consistent images with reproducible thermal patterns in ROIs examined in healthy dogs. Although the coat had a predictable influence to decrease the mean temperature, thermal patterns remained fairly consistent after the coat was clipped.     

Seasonal acclimatisation in the hen

1. The oxygen consumption and body temperature of White Leghorn x Rhode Island Red laying hens, which were being kept in a semi-natural climate, were periodically measured for short periods at ambient temperatures between 2 and 32 degrees C in a suitable chamber. 2. A seasonal shift was observed in lower critical temperature (Tc) and thermoneutral oxygen consumption. The slope of the relationship between oxygen consumption and air temperature at less than Tc was not discernibly affected by season. 3. The seasonal shifts correlated best with mean daily outside temperature Ta) during the experimental periods; a seasonal decrease of 10 degrees C in Ta was associated with a decrease of 8.5 degrees C in Tc and a 12% increase in thermoneutral oxygen consumption. 4. The capacity to maintain body temperature stability at extremes of environmental temperature was improved by acclimatisation to heat.     

Effect of transdermally administered fentanyl on minimum alveolar concentration of isoflurane in normothermic and hypothermic dogs

OBJECTIVE: To determine whether the minimum alveolar concentration (MAC) of isoflurane was altered by transdermal administration of fentanyl in normothermic and hypothermic dogs. DESIGN: Randomized complete block crossover design. ANIMALS: 6 mature healthy dogs. PROCEDURE: Dogs received each of 4 treatments in random order. Following induction of anesthesia, normothermia was maintained in dogs that were treated with a fentanyl patch (F-NORM) or sham patch (C-NORM), or hypothermia was maintained in dogs that were treated with a fentanyl patch (F-HYPO) or sham patch (C-HYPO). The appropriate patch was applied 24 hours prior to induction of anesthesia. Anesthesia was induced with isoflurane in oxygen; the dogs were intubated and mechanically ventilated. Target esophageal temperatures were maintained within 1 degrees C of baseline values (normothermia) or at 34.5 degrees C (94.1 degrees F; hypothermia) for 1 hour prior to starting MAC determinations. Supramaximal stimulation was achieved with an electrical stimulator attached to needle electrodes placed in the buccal mucosa of the lower jaw of the dog. RESULTS: Mean MAC +/- SEM of isoflurane during C-NORM, C-HYPO, F-NORM, and F-HYPO treatments were 1.20 +/- 0.17, 0.89 +/- 0.18, 0.76 +/- 0.10, and 0.81 +/- 0.17, respectively. The mean MAC during C-NORM was significantly higher than values for the other treatments. There was no significant difference in mean MAC among the C-HYPO, F-NORM, and F-HYPO treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Data suggest that transdermal administration of fentanyl significantly reduces isoflurane requirements in normothermic dogs. The isoflurane MAC-sparing effects of transdermal fentanyl are not apparent in hypothermic dogs.