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. The dotted line tracks the temperature set on the built-in TS, while the TS target was 29.4 °C for the first 30 minutes and 35 °C for the final 40 minutes. The solid line indicates 41.1 °C, above which rapid organ failure occurs due to hyperthermia

Free access
in Journal of the American Veterinary Medical Association

, 100 mm Hg) and hyperthermia (40.3°C [104.5°F]). The dog's HR was 130 beats/min, SAP was 145 mm Hg (reference range, 100 to 130 mm Hg), DAP was 80 mm Hg (reference range, 60 to 80 mm Hg), MAP was 95 mm Hg (reference range, 80 to 100 mm Hg), and RR was

Full access
in Journal of the American Veterinary Medical Association

Summary

Malignant hyperthermia (mh) is an anesthetic agent-induced hypermetabolic state. Human beings and several other animal species, including dogs, have been described to be genetically predisposed to development of mh. The halothane-triggered mh syndrome was characterized in genetically predisposed dogs, and in vitro contracture sensitivity of biopsied gracilis muscle exposed to halothane and caffeine was quantitated. Within 1 hour of halothane administration, each mh-susceptible dog developed rapid increases in CO2 production and rectal temperature. Reversal of the hypermetabolic state was achieved when halothane was discontinued and dantrolene sodium was given iv. Biopsied gracilis muscle from mh-susceptible dogs had abnormal in vitro contracture responses to halothane and caffeine. These findings were consistent with those observed for mh-susceptible human beings and pigs in which a loss in regulation of muscle cell Ca++ is believed to be the primary etiologic event for induction of mh.

Free access
in Journal of the American Veterinary Medical Association

T he partial mu-receptor agonist buprenorphine is a commonly used opioid during the perioperative period in cats. 1 , 2 Its use, as that of several other opioids, has been associated with the development of hyperthermia in this species. 3 A

Open access
in American Journal of Veterinary Research

SUMMARY

The effect of a passive heat and moisture exchanger on tracheal and large airway temperature, as reflected by esophageal temperature at the thoracic inlet, was determined for 12 anesthetized and ventilated tumor-bearing dogs undergoing whole-body hyperthermia at 42 C. Delivered thermal dose to the esophagus and rectum during 120 minutes of whole-body hyperthermia was quantified as the thermal dose summary measure EQ43. The heat and moisture exchanger significantly increased esophageal EQ43 from 7.3 minutes to 12.1 minutes. Esophageal EQ43, however, remained lower than rectal EQ43. Although use of a heat and moisture exchanger improved esophageal temperature during whole-body hyperthermia, presumably through improved airway temperature, additional methods will be necessary to increase esophageal and airway temperature to the target value of 42 C.

Free access
in American Journal of Veterinary Research

SUMMARY

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (mh) had calcium extrusion activity higher than unaffected swine. Cytoplasmic concentration of ionized calcium was determined by use of dual emission spectrofluorometry and measurement of the ratio of free to calcium-bound form of the fluorescent calcium dye indo-1. Net calcium accumulation and unidirectional calcium extrusion rate were dependent on intracellular calcium concentration. Calcium extrusion from calcium-loaded lymphocytes was monitored while calcium influx was inhibited by suspending the cells in calcium-free medium with a calcium chelator. Net calcium accumulation of untreated lymphocytes was monitored in calcium-replete medium. A novel method of calculation of ionized calcium was used. This method confirmed our previous findings of lower ionized calcium concentration (86 ± 40 and 370 ± 216 nmol/L; P < 0.01) and slower rates of calcium accumulation 39 ± 16 and 127 ± 52 nmol/L/min) in untreated lymphocytes from mh-susceptible swine compared with controls. These changes were attributable to calcium extrusion activity two- to three-fold higher in lymphocytes of mh-susceptible swine (154 ± 36 and 408 ± 47 nmol/L/min at 175 nmol/L; 972 ± 111 and 1,690 ± 505 nmol/L/min at 425 nmol/L). These data were compatible with our model of higher calcium extrusion activity being a compensatory adaptation of mh-susceptible swine lymphocytes to their hypersensitivity to stimuli that increase cytoplasmic calcium concentration.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine influences of breed, sex, and susceptibility to malignant hyperthermia on composition of skeletal muscle and adipose tissue in swine.

Animals

35 male and female swine of German Landrace and Pietrain breeds and of 2 genotypes, normal (MHN) and susceptible to malignant hyperthermia (MHS).

Procedure

Pigs were fed a standard diet ad libitum. After attaining body weight of approximately 100 kg, pigs were slaughtered and skeletal (longissimus thoracis and supraspinatus) muscle and adipose tissue (3 sites) specimens were removed. For each specimen, lipids were extracted by chloroform/methanol and fatty acid (FA) pattern, and cholesterol concentration was determined by gas chromatography.

Results

The overall lipid contents differed significantly between breeds and genotypes; the MHS Pietrain pigs had the lowest lipid quantities. The relative amounts of saturated FA in all tissues were highest in Landrace pigs (P < 0.05), whereas the relative contents of monoenic FA were lower. In addition, for both breeds, the MHN pigs had significantly higher saturated and lower polyunsaturated FA values in all tissues, compared with MHS pigs. More specifically, MHS females of both breeds had the highest relative amounts of polyunsaturated FA. In general, relative cholesterol contents were found to vary little between identified groups.

Conclusions

These data may indicate that, not only does mutation of the calcium release channel of the sarcoplasmatic reticulum, which occurs in MHS swine, influence secondary changes in lipid composition, but so do hormone concentrations and other genotypic factors. Observed differences in lipid content and FA composition could consequently influence specific membrane properties, such as fluidity and cell signaling. (Am J Vet Res 1997;58:738–743)

Free access
in American Journal of Veterinary Research

Summary:

To test the hypothesis that the mutation associated with porcine stress syndrome (pss; malignant hyperthermia) was present in a large proportion of North American and English swine, a simple and rapid laboratory protocol was used for cost-effective, large-scale diagnosis of susceptibility to pss. This pss test was applied to 10,245 breeding swine of various breeds from 129 farms in the United States, Canada, and England. Approximately 1 of 5 swine was a heterozygous carrier of the pss mutation, with approximately 1% being homozygotes. Prevalence of the pss mutation was 97% for 58 Pietrain, 35% for 1,962 Landrace, 15% for 718 Duroc, 19% for 720 Large White, 14% for 496 Hampshire, 19% for 1,727 Yorkshire, and 16% for 3,446 crossbred swine. The pss gene frequencies for these breeds were 0.72, 0.19, 0.08, 0.10, 0.07, 0.10, and 0.09, respectively. In addition to these breeds, we have identified the pss mutation in Poland China and Berkshire breeds. These gene frequencies were 30 to 75% lower in Canadian swine than in US swine, with the exception of Yorkshires, for which the gene frequency was threefold higher in Canadian swine. English swine were similarly, or more so, affected than were US swine. Accuracy was estimated at > 99%. Cost to perform the test was < $20/ animal. Depending on the perceived net balance of deleterious and beneficial effects of the mutation, the pss test could be used to eradicate the pss mutation from herds, or for controlled expression of the mutation.

Free access
in Journal of the American Veterinary Medical Association