Hyperthermia In Dogs Research Articles

Voluntary head dunking after exercise-induced hyperthermia rapidly reduces core body temperature in dogs.

To evaluate field-applicable cooling methods for treatment of exercise-induced hyperthermia in dogs. In this randomized, crossover study from June 27, 2023, to July 24, 2023, 12 working dogs exercised for 10 minutes until core body temperature reached 40.6 °C or above or ≥ 2 signs of heat stress were observed. Four different cooling protocols were evaluated: (1) neck chemical ice packs (2), (2) a wet (22 °C) neck towel, (3) wet (22 °C) axillae towels, or (4) voluntary head immersion ("dunking") into (22 °C) water. After intervention, dogs rested and were monitored for 40 minutes. The dunking protocol, which included limited water ingestion, produced the lowest mean core temperature in the initial 5 minutes after exercise, in the subsequent 35 minutes during which dogs cooled to baseline temperature and was the only protocol to prevent the initial postexercise temperature rise. All methods resulted in return to baseline temperature. Trained voluntary head dunk with limited water ingestion results in rapid cooling in field situations of exercise-induced hyperthermia in dogs with normal mental status and ability to pause panting. "Cool first, transport second" reduces morbidity and mortality of acute heat injury. When whole-body water immersion is not an option, the trained voluntary head dunk in mentally appropriate dogs prevents postexercise rise and rapidly reduces core body temperature within the first 5 minutes. Alternatively, allowing the dog to drink controlled amounts of cool water and pouring water on the dog's head may provide some benefit but warrants further study.

Post-exercise management of exertional hyperthermia in dogs participating in dog sport (canicross) events in the UK

Exercise is a common trigger of heat-related illness (HRI) events in dogs, accounting for 74% of canine HRI cases treated under primary veterinary care in the United Kingdom. However, few empirical studies have evaluated the effectiveness of differing cooling methods for dogs with exertional hyperthermia or HRI. This study aimed to prospectively evaluate effects of ambient conditions and post-exercise management practices (cooling methods and vehicular confinement) on the post-exercise temperature change of dogs participating in UK canicross events. Canine temperature was recorded at three intervals post-exercise: as close as possible to 0- (immediately post-exercise), 5-, and 15-min post-exercise. Ambient conditions and post-exercise management were recorded for 115 cooling profiles from 52 dogs. In 28/115 (24.4%) profiles, the dog's temperature increased during the first 5-min post-exercise. Overall, 68/115 (59.1%) profiles included passive cooling (stood or walked outside), 35 (30.4%) active cooling (cold-water immersion or application of a cooling coat), and 12 (10.4%) involved no cooling and were immediately housed in vehicles. No dogs developed hypothermia during the study and no adverse effects were observed from any cooling method. In hyperthermic dogs, overall post-exercise body temperature change was significantly negatively associated (i.e. the dogs cooled more) with 0-min post-exercise body temperature (β = −0.93, p < 0.001), and not being housed in a vehicle (β = −0.43, p = 0.013). This study provides evidence cold-water immersion (in water at 0.1–15.0 °C) can be used to effectively and safely cool dogs with exertional hyperthermia. Progressive temperature increases in many dogs - even after exercise has terminated - supports the message to “cool first, transport second” when managing dogs with HRI. When transporting dogs post-exercise or with HRI even after active cooling, care should be taken to cool the vehicle before entry and promote air movement around the dog during transport to facilitate ongoing cooling and prevent worsening of hyperthermia during travel.

Prevalence of Blood Parasites in Dogs of Kathmandu Valley

Study in blood parasitic diseases in dog was carried out from August 2014 to November 2014 to find out the prevalence of haemoparasites in clinical cases of hyperthermia in dogs. Blood sample from 50 cases of hyperthermia were collected and examined for any blood parasites by the smear method. The haematological parameter (RBC, WBC, PCV, Hb, &amp; DLC) of each sample was also assessed and analyzed. Data was analyzed to determine prevalence of various species of blood parasites to establish the correlation of the infections with age, sex and breed. Out of 50 samples examined, blood parasites were determined in 12 percent samples of which 2(4%) were positive for Babesia canis and 4 (8%) were positive for Ehrlichia spp. The percentage of infection was greater in female 4(16.67%) than male 2(7.14%). The prevalence of blood parasite was higher in German shepherd. The prevalence of blood parasite was higher in 2-4 years of dogs. To determine significant difference between the hematological parameter of infected and non-infected cases, t-test was need (R, version 3.0.3). The confidence level for the analysis was set at 95percent with significance level assessed at p&lt; 0.05. The study between the infected and non-infected host revealed statistically significant difference in PCV, Neutrophil and Eosinophil. Whereas other parameters did not have any significant difference. The mean PCV was significantly low (P &lt;0.05) in infected dog than in non-infected dog. Mean Neutrophil was significantly decreased whereas Eosinophil was increased in infected dogs than in non-infected dogs.

Malignant hyperthermia in dogs during general anaesthesia

Malignant hyperthermia is a pharmacogenetic disorder of skeletal muscles developing as a hypermetabolic response to inhalation anaesthetics such as halothane, sevoflurane or isoflurane and depolarizing muscle relaxants such as succinylcholine. It is produced by mutation of the RYR1 gene in dogs. In anaesthetised dogs, regardless of the anaesthetic drugs used, calcium ion channel activity may change and malignant hyperthermia may develop. Clinical features are hyperthermia, tachypne, hypercarbia, increased oxygen consumption, severe metabolic acidosis, hyperkalemia, cardiac arrhytmias and muscle rigidity. For a diagnosis of malignant hyperthermia to be made, at least 3 of the clinical findings must be determined. Dantrolene sodium is specific antagonist of malignant hyperthermia. However, it is not usually preferred by veterinary practitioners due to its high cost as well as the low incidence of the occurence of this complication. Therefore it is useful for alternative drugs such as acepromazine, diazepam and alfentanil to be used for the treatment of clinical findings manifested during malignant hyperthermia. The purpose of this review is to share with colleagues the latest information regarding the treatment of canine malignant hyperthermia occurring in relation to general anaesthesia.

Effect of Short‐Term Scrotal Hyperthermia on Spermatological Parameters, Testicular Blood Flow and Gonadal Tissue in Dogs

The objective was to assess the effect of a short-term scrotal hyperthermia in dogs on quantitative and qualitative ejaculate parameters, testicular blood flow and testicular and epididymal histology. After a control period, the scrotum of seven normospermic adult beagle dogs was insulated with a self-made suspensory for 48h. Nine weeks later, two animals were castrated, while in five animals, scrotal hyperthermia was repeated. Dogs were castrated either 10 or 40days thereafter. In each phase of scrotal insulation, average scrotal surface temperature increased by 3.0°C. Semen was collected twice weekly throughout the experiment. Total sperm count did not change after the first hyperthermia, but it slightly decreased after the second (p<0.05). Profiles of sperm morphology and velocity parameters (CASA) rather indicated subtle physiological variations in sperm quality than effects of a local heat stress. Chromatin stability of ejaculated spermatozoa as indicated by SCSA remained constant throughout the experiment. Perfusion characteristics of the gonads, that is, systolic peak velocity, pulsatility and resistance index at the marginal location of the testicular artery, did not change due to hyperthermia (p>0.05). Histological examination of excised testes and epididymides for apoptotic (TUNEL and activated caspase-3) and proliferating cells (Ki-67 antigen) indicated only marginal effects of scrotal insulation on tissue morphology. In conclusion, a mild short-term scrotal hyperthermia in dogs does not cause substantial changes in sperm quantity and quality. In contrast to other species, canine testes and epididymides may have a higher competence to compensate such thermal stress.

Effects of colon hydrotherapy on liver injury induced by hyperthermia in dogs

Effects of colon hydrotherapy on liver injury induced by hyperthermia in dogs

Late Response to Whole-Lung Irradiation Alone and with Whole-Body Hyperthermia in Dogs

The late effects of whole-lung irradiation with and without whole-body hyperthermia were studied in beagle dogs. The reference doses ranged from 18 to 49.5 Gy given in 1.5-Gy fractions over 6 weeks. Whole-body hyperthermia was given in three 2-h treatments to a deep rectal temperature of 42.0 degrees C. Radiation was given simultaneously with hyperthermia on those days. Physiological and histopathological responses were evaluated. Physiological changes included decreases in cardiac output, systemic blood pressure, dynamic compliance and serotonin uptake. Early changes included an increase in extravascular water and total protein in the lavage. These changes were considered mild, were compensated for and occurred only in dogs receiving doses of 40.5 Gy or greater given in 1.5-Gy fractions over 6 weeks. Histopathological changes were typical of irradiated lung and included pleural fibrosis, interstitial fibrosis, fibrotic foci, and peribronchial and perivascular fibrosis. There was no enhancement of late injury to lung by hyperthermia seen in this study.

Hyperthermia in dogs left in cars.

Hyperthermia in dogs left in cars.

人為的高体温のイヌ皮膚, 筋の血流量および代謝に及ぼす影響

人為的高体温のイヌ皮膚, 筋の血流量および代謝に及ぼす影響

人為的高体温時の腎皮質, 及び腎髄質組織血流

人為的高体温時の腎皮質, 及び腎髄質組織血流

Phase I study of melphalan alone and melphalan plus whole body hyperthermia in dogs with malignant melanoma

The maximum tolerated dose of melphalan combined with whole body hyperthermia (WBH) in dogs with spontaneous malignant melanoma was lower than in dogs not receiving WBH by a factor of 1.9 +/- 0.71. Thirty-three dogs were treated monthly with escalating doses of melphalan and followed weekly for toxicity and, when possible, tumour response. Toxicity was manifested as myelosuppression with nadir neutrophil and platelet counts occurring at 7-10 days post-treatment. The TD50 (+/- S.E.), defined by logistic regression analysis, was 0.63 (+/- 0.07) mg/kg and 0.33 (+/- 0.10) mg/kg for melphalan alone and combined with WBH, respectively. Objective tumour response in this limited series occurred in three of fourteen evaluable dogs (three of eleven treated with melphalan alone and none of three treated with WBH plus melphalan). It is concluded that melphalan combined with WBH can be safely administered, although a reduction in dose is necessary. A randomized clinical trial is required to investigate the possibility of achieving therapeutic benefit from combined melphalan and WBH.

Whole body hyperthermia in dogs using a radiant heating device: effect of surface cooling on temperature uniformity.

Rectal and subcutaneous temperatures were measured during a total of 10 whole body hyperthermia treatments conducted in six dogs. During five of the treatments skin cooling, by means of initiating air flow through the radiant heating device, was necessary during the plateau phase because rectal temperature exceeded the target value. Skin cooling was not necessary in the other five treatments. Although the rectal temperatures were similar in all 10 treatments, extensive and rapid subcutaneous temperature non-uniformity, of approximately 4 degrees C, developed during treatments where skin cooling was necessary. During the treatments where skin cooling was not necessary, the subcutaneous temperature remained approximately equal to the rectal temperature. These data indicate that the environment in the radiant heating device during the plateau phase can have a profound effect on the temperature at superficial sites, which is not reflected by the temperature measured at deeper sites. The temperature at superficial sites should be measured during whole body hyperthermia to assure that the prescribed heat dose is administered to the largest percentage of body mass possible. Active skin cooling during whole body hyperthermia should be avoided if possible.

Perioperative Hyperthermia in Dogs and Cats

One of the most common physiological alterations associated with anaesthesia and surgery is hypothermia. Anaesthetic agents alter the ability of the animal to regulate its body temperature and since the environment is usually colder than the animal the end result is usually hypothermia. Rarely animals will become hyperthermic during anaesthesia and an operation. This may be due to a gain of heat from the environment, an inhibition of the normal mechanisms for heat loss or due to an increased production of heat by the animal. When dealing with a small animal patient, exhibiting a sudden rise in body temperature during anaesthesia and an operation, it is important to understand the cause of the change in order to apply the appropriate therapy.

Enhanced glucose availability for working muscles reduces exercise hyperthermia in dogs

Body temperature and metabolic responses to 2 h treadmill exercise in dogs given glucose intravenously (25-30 mg.kg-1 X min-1 throughout the run) were compared with those measured in the same animals with elevated plasma FFA concentrations (soya bean oil ingestion + intravenous heparin) and in control experiments (24 h fasting). In comparison with control conditions enhanced glucose availability for the working muscles caused a reduction in the exercise-induced increases in both rectal (by 0.9 +/- 0.11 degree C) and muscle (by 0.9 +/- 0.16 degree C) temperatures, a lower rate of oxygen uptake (by 16%) and an elevated respiratory exchange ratio. A tendency towards enhanced body temperature responses to exercise, accompanied by increases in VO2 and cardiac frequency was noted in dogs with elevated plasma FFA concentrations as compared with the control animals. The estimated amount of heat effectively dissipated from the body, expressed as a fraction of heat load (thermoregulatory efficiency) was significantly higher in dogs infused with glucose (0.962 +/- 0.0035), than in the controls (0.947 +/- 0.0043) and those with elevated plasma FFA concentrations (0.931 +/- 0.0029). It is concluded that the increased contribution of carbohydrates to the energy yield during exercise results in a marked attenuation of hyperthermia, associated with a reduced metabolic rate and improved thermoregulatory efficiency.

Intraperitoneal approach to regional hyperthermia--possible anticancer applications.

AbstractInduction of hyperthermia in dogs by irrigation of the peritoneal cavity via a closed circuit system was evaluated for possible use in the management of cancer patients. Dogs were subjected to lavage of the peritoneal cavity with crystalloid solution at 41°–43°C in a closed circuit system. Temperatures of the liver and hollow viscera were maintained at 40°–42°C for 4 hours. The animals tolerated the procedure, and the parietal incisions and intestinal anastomoses healed without difficulty. Evidence of toxicity was minimal. Plans for studies of this modality in patients with cancer are underway.

Cerebral temperature and epidural pressure during whole body hyperthermia in dogs.

Whole body hyperthermia was performed on 13 anaesthetized and intubated dogs. Cerebral temperature and epidural pressure were measured and related to rectal and oesophageal temperatures. The brain temperature was significantly higher than that of the rectum at normotemperature. The temperature gradients lessened during heating. At maximum rectal temperature (plateau) small differences between the left and right hand sides of the brain were seen, the temperatures being 0.4 degrees C and 0.3 degrees C higher than the rectal temperature, respectively. During the 2-h plateau period the difference between brain and oesophageal temperature became progressively smaller. The mean epidural pressure decreased slightly during the course of the treatment, but remained within the normal range of 1.2 +/- 0.4 KPa (8.7 +/- 2.5 mm Hg). From this investigation may be concluded that (1) the cerebral temperature is reflected better by the oesophageal than by the rectal temperature and (2) the epidural pressure does not increase during whole body hyperthermia for 2 h at a rectal temperature of up to 42.5 degrees C.

Circulatory failure during severe hyperthermia in dog.

The effect of acute hyperthermia on circulatory function was studied in 6 mongrel dogs. At a core temperature of about 40 degrees C, central venous pressure and stroke volume were maintained at almost normal level. Cardiac output significantly increased (26 ml/(kg . min)) while systemic vascular resistance significantly decreased (1.2 mmHg . sec/ml). In addition, significant decrease in vascular compliance by 40% was observed. When body temperature was raised further (severe hyperthermia), an abrupt fall of arterial pressure was observed at the rectal temperature of about 41-42 degrees C. Concomitant decreases in central venous pressure (3 mmHg), stroke volume (2.1 ml/beat) and cardiac output (29 ml/(kg . min)) were observed while heart rate increased (48 beats/min). These results suggest that the decrease in cardiac output during severe hyperthermia is due to the fall of central venous pressure, and the fall was attributed to the increase in unstressed vascular volume of systemic circulation due to the heat-induced cutaneous vasodilation. The observed decrease in systemic vascular compliance is considered to have a significant role in the maintenance of central venous pressure under hyperthermia.

Systemic hyperthermia in dogs

Systemic hyperthermia in dogs

Stereotyped behavior and hyperthermia in dogs: correlation with the levels of amphetamine and p-hydroxyamphetamine in plasma and CSF.

A gas-chromatographic method for simultaneously measuring p-hydroxyamphetamine (pOA) against amphetamine (A) in plasma and CSF is presented. The time course of body temperature (Tb), stereotyped behavior (St), and A and pOA levels in plasma and CSF were studied after administration of 0.6 and 1.5 mg/kg p.o. of A to dogs. Stereotyped behavior reached maximal value 2.5 h after A, as did levels of A in CSF. The A levels in CSF decreased steadily in the following hours and simultaneously with the levels of A in plasma. St remained elevated and began to decrease after 6.5 h. The relationship between St and amounts of A was not linear but exponential. This suggest that both A and its metabolite contributed to this effect. In fact, a linear relationship was found between St and the amounts of pOA in CSF. Body temperature had a time course similar to A plasma levels, reaching peak value after 1.5 h and declining thereafter simultaneously with A. A linear relationship was found between Tb and the amounts of A in plasma. Thus Tb seems to be a peripheral A effect related to the presence of the drug in plasma.

Lactate and pyruvate levels in brain and skeletal muscle during hyperthermia in dogs.

Tissue hypoxia, as shown by an increase of the arterial concentration of lactate and of the lactate–pyruvate (L/P) ratio, has been observed during hyperthermia in free-breathing animals with high arterial [Formula: see text]. The effect of raising body temperature to 41.9 °C for 2 h on lactate and pyruvate concentrations in arterial, muscle venous, and sagittal sinus blood and cerebrospinal fluid was studied in anesthetized dogs. The animals were paralyzed with gallamine, and arterial pH and [Formula: see text] maintained at normal levels by artificial ventilation with 50% O2[Formula: see text]. A slight increase in lactate and pyruvate took place in the arterial blood and parallel changes were observed both in the muscle venous and sagittal sinus blood. The L/P ratio did not change. Lactate and pyruvate increased markedly in the CSF, without a change in the L/P ratio. Therefore hyperthermia, in the absence of respiratory alkalosis, does not appear to induce tissue hypoxia associated with an increase in L/P ratio. The lack of correlation between lactate and pyruvate concentrations in sagittal sinus blood and cerebrospinal fluid confirms the fact that the A–V differences of these substrates across the brain are not a good index of cerebral metabolism.