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V. Conclusions.

In view of the results obtained from this lim-
ited study, we should remember that 130.0° F is
on the high side of the ambient temperature
seale to which dogs could be exposed during air
transport. With a dog’s average rectal tempera-
ture being 101.5° F, the question remains: At
what ambient temperature will a dog sustain
permanent damage from hyperthermia? We
should not assume that all dogs will respond to
a given temperature in the same manner. Aside
from health problems that can influence a dog’s
ability to withstand various temperatures, there

are at least three anatomical characteristics that
should be considered. First, there is a wide range
of size in breeds weighing from 3 to 175 pounds
and, therefore, considerable variation in the area
of body surface exposed. Second, the hair coats
of various breeds differ in density, length, and
texture. Third, the brachycephalic breeds of
dogs have short, narrow nasal passages, pen-
dulous soft palates, and heavily muscled throats—
characteristics that increase the effort of ac-
celerated breathing during panting. These fac-
tors should be studied further before the FAA
can recommend thermal limits for the air trans-
portation of dogs.

References

1. American Airlines: Freight Service Manual, Freight
Edition, 4, August 31, 1973.

2. Armistead, W. W.: Heat Stroke and Heat Prostra-
tion. In Canine Medicine. Haskins, H. P., Vv.
Lacroix, and K. Mayer (Ed.), 2d ed., American
Veterinary Publications, Inc., Santa Barbara, Calif.
708-712, 1971.

3. Freeman, W., and E. Dumoff: Cerebellar Syndrome
Following Heat Stroke, ARCH. NEUROL. PSY-
CHIATRY, 51:67-72, 1971.

4. Hall, W. W., and E, G. Wakefield: A Study of Ex-
perimental Heat-Stroke, TAMA, 89 1177-182, 1927.

5. Hartman, F. W., and R. C, Major: Pathological

Change Resulting From Accurately Controlled Arti-

ficial Fever, AM, J. CLIN. PATHOL. 5:392-410,

1935.

Higgins, BE. A.; Some Physiological Responses of

Dogs to Heat and Humidity, Ph.D. Thesis, Uni-

versity of Oklahoma, Norman, Okla., 1966.

7. Jampietro, P. F., M. J. Burr, V. Fiorica, J. M
McKenzie, and EB. A. Higgins: pH-Dependent Lysis
of Canine Erythrocytes, J. APPL. PHYSIOL,
28 505-510, 1967.

8. Jacobsen, V. C., and K. Hosoi: The Morphologic

Changes in Animal Tissues Due to Heating by an

Ultrahigh Frequency Oscillator, ARCH. PATHOL,

11::744-759, 1931.

Kanter, G. S.: Effect of Heat on Regulation of Body

Fluids and Electrolytes in Dogs, AM. J. PHYSIOL.

178 :259-262, 1954.

e

>

10. Kanter, G. S.: Cause of Hypoglycemia in Dogs Ex-
posed to Heat, AM. J. PHYSIOL., 196 619-624, 1959.

11, Kanter, G. S. and R. H. Lubinski: Effect of Heat
on Inorganic Phosphate Regulation in Dogs, AM. J.
PHYSIOL., 180 :559-562, 1955.

12, Knudson, A. and P. J. Schaible: Physiologic and
Biochemical Changes Resulting From Exposure to
an Ultrahigh Frequency Field, ARCH. PATHOL.,
11.:728-743, 1981.

48. Leithead, C. S, and A. R. Lind: Heat Stress and
Heat Disorders, F. A. Davis Company, Philadelphia,
Pa., 1964.

14. Malamud, N., W. Haymaker, and R. P. Custer: Heat
Stroke. THE MILITARY SURGEON, 431, Novem-
ber 1946.

45, Mortimer, B.: Experimental Hyperthermia Induced
by the High Frequency Current, RADIOLOGY,
16 :705-718, 1981.

‘emoto, E. M., and H. M. Frankel; Cerebral Oxy-

genation and Metabolism During Progressive Hyper-

thermia, AM. J. PHYSIOL., 219:1784-1788, 1970.

17. Special Studies Subcommittee, Committee on Gov-
ernment Operations, House of Representatives:
problems in Air Shipment of Domestic Animals, US
Government Printing Office, Washington, D.C., Hear-
ings held September 26-28, 1973.

18. Zachary, M.: Air Shipment of Pets, VET. MED.
SMALL ANIM. CLIN,, 925-928, August 1975.



were suggestive of early cortical necrosis. In
the tissues showing tubular necrosis, the changes
were present as early as 28 h and as late as 100 h
postexposure. In one dog necropsied at 28 h,
the changes were so profound that, in our ex-
perience, if the dog had been allowed to live it
would probably have experienced renal failure.

The lung from all the exposed dogs showed
some degree of pathology. Those necropsied at
4, 28, and 52 h revealed more Jung changes than
those sacrificed at 100 and 196 h. The predomi-
nant histopathological findings were thickening
and congestion of the alveoli septi, hemorrhage
and/or edema in the alveolar spaces, and engorge-
ment of the blood vessels, Occasionally, a speci-
men had hemorrhage or debris in a few of the
bronchi.

IV. Discussion.

The results of this study showed significant
(p<0.01) changes in heart rate, rectal tempera-
ture, Pvco , blood pH, Hb, RBC, PCV*, and

weight that can be related to the exposure en-
vironment. The effects of humidity produced
significant differences between the 15-percent-RH
and 35-percent-RH groups for Pvoo, 5 blood pH,

rectal temperature, and weight loss. Peak heart
rate increase occurred in 5 of the 10 dogs of the
15-percent-RH group before the end of the 30-
min exposure whereas 7 of the 10 in the 35-
percent-RH group peaked before the end of
exposure. Although no significant change was
found in BUN, 2 of 10 dogs showed a decrease
in BUN at the 15-percent-RH exposure whereas
7 of 10 at the 35-percent-RH exposure showed a
decrease. Some of the remaining parameters
showed changes that were not significant.

Hemolysis was also noted in samples from a
few of the dogs exposed to the 35-percent humid-
ity, but the quantity was not measurable.
Tampietro e¢ al." showed that hemolysis occurred
in dogs exposed to temperatures ranging from
70.0° to 120.0° F at 50-percent RH for up to 60
min. He states that hemolysis might have been
the result of extremely low blood CO, and/or
high pH brought about by hyperventilation
and/or high body temperature.

Throughout the available literature, we found
few reports that histology had been performed
on surviving victims of hyperthermia. Hartman
and Major® reported histological changes in
anesthetized dogs exposed to temperatures of
from 150.0° to 175.0° at 30- to 40-percent RH.
Histological changes in animal tissues have been
reported by Jacobsen and Hosoi® and by Morti-
mer’* in studies of experimental hyperthermia
induced by ultrahigh frequency oscillators or
high frequency current. Hall and Wakefield‘
showed that degenerative changes occurred in
the brain, heart, kidney, and lung of dogs that
died from experimental heatstroke. Malamud
et al. studied 125 fatal cases of heatstroke in
military personnel who had undergone strenuous
muscular exercise at high temperatures. Ac-
cording to their description, the histopathological
changes of the brain and viscera in these cases
closely parallel the changes found in our dogs.
Freeman and Dumoff,’ in their report on cere-
bellar syndrome following heatstroke in man,
state that periods of exposure must be brief
because at high temperatures the pathological
alterations in the body cells rapidly become ir-
reversible.

In our study, the histopathological changes in
the brain, heart, kidney, and lung examined pro-
vided the most interesting and valuable informa-
tion. It is our opinion that most of the changes
in the cerebellum and cerebral cortex are consid-
ered severe and permanent and that the neuronal
changes developed during the period of hyper-
thermia. We believe the fragmentation of the
myocardium, loss of myofibrillar striations, and
pyknotic nuclei are attributable to hyperthermia.
In those dogs whose kidneys showed acute corti-
cal necrosis, this was, we believe, related to hyper-
thermia in that none of the dogs experienced any
clinical signs of shock. In general, the changes
observed in the lungs were minimal to moderate
with those necropsied at 100 and 196 hours show-
ing signs of recovery. We were unable to detect
any qualitative or quantitative relationship in
tissue changes between the two humidity groups.
Although all dogs survived acute hyperthermia
with no signs of illness, there were histological
changes in the tissues examined.




Technical Report Documentation Page

1. Repert No. 2, Government Accession No. 3. Recipient's Catalog No.
FAA-AM-77-8

4, Title ond Subritle 3. Report Date

A STUDY OF EFFECTS OF HYPERTHERMIA ON LARGE, SHORT- March 1977

HAIRED MALE DOGS: A SIMULATED AIR TRANSPORT 6. Performing Organization Code

ENVIRONMENTAL STRESS

8. Performing Organization Report No.

7 hohotyy C.D. Hanneman, D.V.N., E. A. Wiggins, Ph.D.,

G.'T. Price, D.V.M., G. E. Funkhouser, P. M. Grape,
and_L Snyder

9. Performing Organization Name and Address 10. Work, Unit No. (TRAIS)
FAA Civil Aeromedical Institute TI Connector Gran N
P.O. Box 25082 ‘ontract or Grant Ne
Oklahoma City, Oklahoma 73125

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address
Office of Aviation Medicine OAM Report
Federal Aviation Administration
800 Independence Avenue, S.W.

Washington, D.C. 20591. PAA

15. Supplementary Notes

14. Sponsoring Agency Code

This research was conducted under Task AM~A-74-VM-1 and AM-E-75-VM-1.

16. Abstract

When dogs are shipped by air transport, they can encounter environmental temperatureg
as high as 130.0° F during the summer months. Normally, little concern is given to
the effects of hyperthermia on animals; however, heat-induced hyperthermia can be a
major problem in dogs. To assess some aspects of the heat stress problem, 20 dogs
were exposed to an ambient temperature of 130.0° F for 30 minutes--10 dogs at 15-
percent relative humidity and 10 at 35-percent relative humidity. Transient and
permanent changes were seen; however, no dogs died from exposure. All dogs exhibited
increases in heart rate, rectal temperature, blood pH, hemoglobin, packed cell
volume,and red blood cell count while body weight and blood carbon dioxide
decreased. There were also differences between the two groups for blood pH, blood
carbon dioxide, rectal temperature, and weight loss. The major histological tissue
changes attributed to hyperthermia were fragmentation of the myocardium, acute
cortical necrosis in the kidneys, and marked degenerative changes in the cerebellum
and cerebral cortex that were considered severe and permanent.

17. Key Words 18. Distibution Statement
Hyperthermia Histopathology | Document is available to the public
Environmental Stress Blood Chemistry | through the National Technical Information
Dogs Humidity Service, Springfield, Virginia 22161.
Transportation

19. Security Clossif, (of this report) 20. Security Classif. (of this page) Die No. of Pages | 22. Price
Unclassified Unclassified

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized





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A STUDY OF EFFECTS OF HYPERTHERMIA ON LARGE, SHORT-HAIRED
MALE DOGS: A SIMULATED AIR TRANSPORT
ENVIRONMENTAL STRESS

I. Introduction.

In the early 1970’s, the general public let it be
known that they were concerned about the safe,
efficient, and humane treatment of animals dur-
ing shipments by air freight. In 1978 the Special
Studies Subcommittee of the Committee on
Government Operations, House of Representa-
tives, conducted hearings on problems in air
shipment of domestic animals.’ Testimony be-
fore this committee made quite evident that of
the environmental stresses animals can be exposed
to during shipment, heat is the most serious. It
has been reported that in an air carrier on the
ground in the summer, temperatures may reach
180.0° F or higher in the cargo compartment.* *7 **

When animals are exposed to ambient tem-
peratures that exceed their normal body temper-
atures, they may experience hyperthermia.’
The degree of hyperthermia in an animal de-
pends on such factors as humidity, ventilation,
and the animal’s muscular exertion, hair coat,
and physical condition. During an episode of
hyperthermia, an animal may show little clinical
evidence of harm; however, transient and perma-
nent changes can occur. Because of public con-
cern more attention has been given to the dog
and its well-being than to other domestic small
animals,

The dog, unlike man, produces little sweat but
promotes heat loss through panting. By panting,
the dog is able to evaporate moisture from its
tongue and upper respiratory tract. However,
as the relative humidity (RH) increases or when
ventilation is inadequate, this process becomes
less effective in dissipating heat. Prolonged ex-
posure to these factors can tax a dog’s ability to
maintain a normal body temperature, and heat
hyperpyrexia or heatstroke can result.?

In the past decade, little progress has been
made in studying the biochemical and histopath-
ological effects of hyperthermia on animals. It
is a question, so far unanswered, of what degree
and duration of hyperthermia will damage the
central nervous system.% In 1927, Hall and
Wakefield‘ studied hyperthermia in female dogs
in an environment in which the dry-bulb tem-
perature ranged between 131.0° and 141.0° F and
the wet-bulb temperature ranged between 95.0°
and 115.0° F. After 20-75 minutes of exposure,
the dogs’ rectal temperatures ranged between
106.0° and 113.4° F. They noted increases in
blood urea nitrogen (BUN), sugar, chlorides,
lactic acid, creatinine, and calcium (Ca) and de-
creases in plasma carbon dioxide (CO,) combin-
ing power, inorganic phosphate, and serum pH.
Histopathology showed cellular degeneration in
the lung, kidney, liver, heart, and brain.

Jacobsen and Hosoi’ used radiothermy on dogs.
Eleven dogs received single exposures ranging
from 37 minutes to 12 hours with resultant maxi-
mum rectal temperatures of 108.0° to 111.0° F.
Of the 11 dogs exposed, 6 died within 40 minutes
after heating. Histopathology showed changes
in the heart, lung, spleen, gastrointestinal tract,
kidney, and brain. Knudson and Schaible”
studied canine physiological and biochemical
changes resulting from exposure to an ultrahigh
frequency field. Exposure times ranging from
30 minutes to 5 hours 15 minutes resulted in
rectal temperatures ranging from 104.0° to 109.9°
F. Weight loss ranged from 1.9 percent to 11.1
percent in dogs that were given no water during
treatment. Most dogs were exposed more than
once. The biochemical changes in the blood
were similar to those reported by Hall and
Wakefield. Hartman and Major* reported path-
ological changes in female dogs resulting from
5 to 7 hours of exposure at 150.0° to 157.0° F
and humidities of 30 percent to 40 percent. The