| This info is from THE ILLUSTRATED VETERINARY ENCYCLOPEDIA
SHOCK
DEFINITION
Shock is the term used to describe an acute and progressive
failure of the peripheral circulation (blood circulation to the
outer body parts-legs, head, etc).
SYMPTOMS
There are many indicators of shock: apathy, prostration, rapid
shallow pulse, rapid breathing, subnormal temperature, cool skin,
sweating, low or falling blood pressure, and the mucous membranes
will be pale and slightly blue.
CAUSES
The specific causes are unknown, but it appears to follow events
which affect the peripheral circulatory system. This occurs after
most major injuries including severe trauma, massive hemorrhage,
internal obstruction, anemia, major infections, burns, cardiac
failure, dehydration, and anaphylaxis (allergic-like sensitization).
INTERNAL FUNCTIONS
Whether it is caused by massive blood loss, tissue toxins (from
damaged tissues)or fluid loss from the vascular system into the
tissues, the peripheral circulatory system begins to fail. In the
mild form of shock, the body can compensate automatically by
constricting the dilated vessels in the peripheral system. This
gives the heart sufficent back pressure to work against which is
neccessary for it to maintain circulation to the major organs.
It is when the damage or trauma is severe or extensivethat this
mechanism is not sufficent to maintain effective blood pressure.
When lowered blood pressure deprives the heart, the nerves that
stimulate constriction of the blood vessels, the vaso constrictor
muscles, of blood and oxygen, the heart weakens and cannot keep
the vessels consticted. This allows them to dilate, further lowering
blood pressure. This further reduces flow, and the body's ability
to maintain critical systems is reduced. It should be understood
that this tissue deprivation includes the major organs of the body.
Inadequate circulating blood results in cellular damage to the liver
and kidneys which sometimes cannot be repaired. Past a certain
point, this tissue deprivation becomes irreversable and death soon
follows.
TREATMENT
Primary treatment must be administered by a veterinarian because
it involves massive replacement of fluids to restore both blood
pressure and volume. Whole blood, plasma, plasma extenders, or
saline (salt) solution will be used, depending on the need of the
collapsing system. Hemorrhage should be controlled immediatly and
pain should be relieved because it aggrivates shock. Antibiotics
and coticosteroids are of great value and are used frequently.
The animal should be kept warm, but if the tempurature is raised,
the peripheral vessals will dilate, lowering the blood pressure
even more. All of these treatments should be balanced by a physician.
PREVENTION
Shock can be avoided or lessened by preventative treatment.
Avoiding dehydration of animals and calling a veterinarian before
mild shock becomes irreversible are the best prventative methods.
Shock treatment should be closely supervised because animals that
appear to be responding well can quickly and unexplanably relapse
and become critical once again.
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OVERHEATING AND WORK STRESS IN HORSES
A RESEARCH PAPER WRITTEN BY THE UNIVERSITY OF CALIFORNIA-DAVIS
and published in:
THE QUARTER HORSE JOURNAL, APRIL, 1992.
A horse's performance can be limited by extreme heat and/or physical
exertion which create competing demands for efficient cooling and maximum
energy output. When the horse's body fails to regulate its temperature in
response to heat and /or exercise, or when there are excessive fluid and
electrolyte losses, serious medical problems can occur. Effective treatment
depends on early recognition of impending problems.
HEAT STROKE
Heat stroke or heat exhaustion may occur in resting horses confined to
hot, poorly ventilated quarters, particularly during transport. Researchers
at the University of California, Davis, Veterinary Medical Teaching Hospital
have studied cases of horses with severe respiratory distress following
transport in enclosed trailers during the heat of the day and found overheating
to play a key role. More often, however, this problem develops in horses that
are poorly conditioned and overexerted in hot and humid climates.
The clinical signs of heat stroke are depression, weakness, lack of
appetite and a refusal to continue exercising. Pulse and respiratory rates
increase and rectal temperature may rise to 106-110 degrees Fahrenheit
(normal temperature is 98 to 101 degrees Fahrenheit). The capillary refill
time may also be prolonged, which can be checked by pressing a finger against
the horse's gums. When the pressure is released, the white space should
quickly return to a pink color. Despite elevated body temperature, the
sweating response is inadequate, therefore, hot, dry skin is indicative
of impending heat stroke. Depression and weakness may progress to ataxia
(inability to coordinate voluntary muscular movement), collapse, convulsions,
coma or death.
In treating heat stroke, it is essential to lower the body's temperature
rapidly. First, the horse should be moved into the shade in a well-ventilated
area and preferably made to stand in a breeze or in front of a fan. Cool to
cold water should be applied to the horse with either a hose, sprayer, sponge,
or towel. Ice packs and cold alcohol leg wraps may be of additional help.
The most effective way to cool the horses body is to apply the water or ice
packs over the large superficial vessels of the legs, head and neck instead
of the large muscle masses. With severely affected horses, however, applying
water over the entire body may be the quickest and most effective means of
cooling the body. Ice water enemas can also be effective in some situations
to reduce critically high body temperatures. Intravenous fluid therapy is
essential to keep the blood circulating properly.
ANHYDROSIS
Sweating is the principal means of regulating the horse's body temperature.
Hot and humid climates can interfere with this process. ANHYDROSIS is the
inability to sweat properly. Although anhydrosis is most commonly associated
with exercise, the disorder has also been reported in sedentary stabled horses
and broodmares maintained in hot and humid climates.
Most horses gradually develop anhydrosis over time. These horses initially
have a normal exercise-associated sweating response, but subsequently develop
a progressive failure to sweat. Less commonly, the onset may occur suddenly.
Anhydrosis was first recognized by Englishmen who shipped racing or polo
ponies to their tropical colonies. The initial reports in the British
literature stressed that the disease was principally a problem of performance
horses that were native to temperate regions and had been transported to the
tropics. More recent reports from Florida indicate, however, that even horses
reared in hot humid climates may develop anhydrosis.
Today,the disorder is widely recognized in horses maintained in climates that
are hot and humid all year round. In the United States, anhydrosis occurs
commonly in the Gulf states, particularly during the summer. Although
environmental temperatures are often higher in the arid southwest portion of
the United States, anhydrosis is not common, presumably due to the low
humidity.
Clinical signs include the inability to sweat normally, panting, exercise
intolerance, excessive exercise-associated fever, and, in some cases, hair
loss. Depression, lack of appetite and weight loss may also be observed.
Most horses will retain limited sweating capacity, as evidenced by residual
sweating under the mane, over the front of the chest, and under the hind legs
and tail.
The origin and development of anhydrosis is not completely understood. A
combination of persistently high humidity and high environmental temperature
is evidently necessary. Exhaustion of the sweat glands due to continuous
stimulation is considered a possible cause of this disorder.
Metabolic abnormalities associated with electrolytes lost through sweating
are also considered factors contributing to anhydrosis. Although low chloride
and low sodium levels in the blood have been reported with this disorder, they
are not consistent features. Nevertheless, salt should always be available to
working horses.
A partial anhydrosis has been seen following exercise in some of the heavy
breeds such as Warmbloods in California. Some of these horses do sweat, but
apparently not enough to cool their bodies effectively. They exhibit partial
signs of anhydrosis such as exercise intolerance, high rectal temperatures,
and elevated respiratory rates after exercise. This partial anhydrosis also
occurs with some horses in the early fall when their hair coats are getting
thicker but the temperatures are still hot. Some horses in the early spring
also have trouble when they haven't shed their winter coats, the temperatures
are rising and they may not be very fit.
At present, the only effective means of treating severely affected horses
with classic anhydrosis is to move the horse to a more temperate climate.
Milder cases may be prevented by providing horses with air-conditioned stalls.
For horses that exhibit partial anhydrosis, clipping hair coats in early fall
and spring will help as well as avoiding exercise during the heat of the day.
THE EXHAUSTED HORSE SYNDROME
Fatigue results from relatively brief maximal exercise as in racing and
exhaustion results fro protracted submaximal exercise as in endurance riding.
During short-term maximal exertion, energy is primarily generated by the
anaerobic (without oxygen) metabolic breakdown of carbohydrates. Muscle
energy stores deplete rapidly and fatigue correlates closely with the
excessive production of lactic acid.
With endurance exercise, energy is supplied by the aerobic (with oxygen)
metabolic breakdown of both fatty acids and carbohydrates with minimal
changes in lactic acid concentration. The long-term exercises allows time
for substantial fluid and electrolyte losses associated with sweating to
occur. Fatigue after endurance exercise is associated with the depletion
of energy sources as well as fluid and electrolyte imbalances. High
environmental temperatures and/or humidity impose additional stresses
on horses. Both the incidence and severity of the medical problems which
occur with endurance horses are greater during such periods.
When exhaustion is severe, the combined depletion of water and electrolytes
may result in diminished sweat production. When there is a combination of
high temperatures and high humidity, this impairment of the normal means of
cooling the body may result in persistently elevated body temperature with
heat-induced injury to a variety of tissues, including the central nervous
system. Fluid and electrolyte alterations thereby impair the normal function
of the cardiovascular, neuromuscular, digestive and urinary systems.
FLUID AND ELECTROLYTE IMBALANCES
On long endurance rides (100 miles), particularly those held on very hot
days, most horses drink copious amounts of water. Generally, horses that
exercise under these conditions should be allowed to drink at ever opportunity.
Despite frequent access to water, however, many endurance horses, even those
performing normally, develop clinical signs of of slight to moderate
dehydration.
Fluid losses of 20 to 40 liters or more are common on long endurance rides.
Horses that successfully complete these rides and continue to eat and drink
normally appear to replenish most of their fluid losses by the end of the ride
or early in the recovery period.
Electrolyte concentrations in the blood change predictably with endurance
exercise in hot environments, whereas relatively few changes are observed in
moderate to cooler climates. Electrolyte losses in horses sweat include
significant amounts of sodium, potassium, chloride, calcium and magnesium.
The combination of dehydration and sodium depletion results in increased
blood viscosity (thickening), decreased blood volume and inadequate
circulation. This may contribute to impaired kidney function and lead to
partial kidney shutdown as part of the overall cardiovascular effects. The
acid-base disturbance associated with depletion of potassium, calcium and
magnesium may alter nerve/muscle interaction and contribute to the lack of
gastrointestinal function, irregular heartbeat, muscle cramps and spasms.
RECOGNIZING AND TREATING EXHAUSTION
Table 1 lists the clinical signs of exhaustion. The severity of these
signs varies in individual horses. All affected horses have elevated rectal
temperatures, elevated pulse rates and variable dehydration. The most
reliable quantitative guide to impending exhaustion is the pulse recovery
rate. At mandatory rest stops on endurance rides, the 30-minute post-arrival
pulse rate should return to an acceptable level, usually 60 to 70 beats per
minute. At the veterinary checkpoints, which have shorter mandatory rest
periods of 10 to 15 minutes, slightly higher values may be used as a base
line reference. No horse should be allowed to continue exercising until its
pulse rate has recovered sufficiently.
Horses that are depressed and have persistently elevated pulses and
respiratory as their only problems may respond to rest, cooling out,
access to salt, and clean feed and water. A return of appetite and water
consumption is vital to the recovery of these horses. All should be closely
watched. If they do not improve within 30 minutes, they may require oral
an/or intravenous fluids from a veterinarian.
In most normal horses, rectal temperatures begin to return to normal 15
to 30 minutes after cessation of exercise. Horses with rectal temperatures
in excess of 105 degrees Fahrenheit, or persistently elevated rectal
temperatures, should be cooled with a spray of cold water in an open space
with free air movement. This is especially important when there is high
heat and humidity because sweating is less effective at cooling the body's
temperature during these conditions. Cold water enemas may be beneficial
in sever cases of overheating. Rapid cooling is essential in these horses.
Recognition of severely exhausted horses is relatively simple. These
animals are usually severely depressed and show little interest in food and
water despite their apparent dehydration. Most continue to sweat, although
at apparently reduced rates. Pulse and respiratory rates generally remain
elevated, despite a rest period. The pulse may be weak, heart rhythm may
be irregular, intestinal sounds are usually absent or markedly diminished
and anal tone is lacking. Some horses may also develop spasmodic colic.
Other horses may also develop synchronous diaphragmatic flutter (SDF).
Synchonous diaphragmatic flutter is the result of a contraction of the
diaphragm that is synchronous with the heartbeat. It is apparent as a
twitch or spasm in the flank. The twitch is not related to normal
respiratory movements and may become sufficiently violent to produce an
audible thumping sound, hence the descriptive term "thumps".
Synchronous diaphragmatic flutter is seen most frequently in endurance
horses performing in hot climates. This condition has also been reported
in horses with shipping fever, milk fever and electrolyte imbalances
associated with digestive disturbances such as impending enteritis
(inflammation of the intestines and diarrhea). Some race horses may develop
SDF following the administration of furosimide as a prerace medication for
exercise-induced pulmonary hemorrhage. By itself, SDF is probably not
dangerous, but is an index of significant electrolyte balances and, as such,
is generally considered grounds for removing an animal from competition.
Horses with signs of sever exhaustion need to be treated by a
veterinarian. Treatment may require prompt and vigorous fluid therapy to
restore adequate volume, correct electrolyte deficits and provide ready
sources of glucose (blood sugar) for metabolism. The principle problems in
these horses are dehydration and and sodium depletion, so rapid restoration
of the fluid volume with sodium-containing replacement fluids is essential.
Intravenous fluids can be supplemented or, in some cases, replaced by
fluids administered by stomach tube. Fluids given by this route seem to
be well tolerated and fairly rapidly absorbed. This route also offers the
advantages of speed and convenience, but should not be used in horses that
are down, show signs of colic or a lack of intestinal function.
MUSCLE PROBLEMS
Exercising horses frequently develop muscle problems, most commonly seen
as the tying-up syndrome (azoturia or "Monday Morning Disease") evidenced by
sweating, stiffness in the hind end and a reluctance to continue exercising.
Researchers originally believed that tying-up resulted from a massive
accumulation of lactic acid in the muscle cells. Recent research has shown
that this is not always true.
Most likely, a variety of factors produce the muscle damage or dysfunction
we recognize as tying-up syndrome. A partial list of causal factors include
nutritional deficiencies (selenium and vitamin E), excitement or fear,
postviral (influenza) effects, gait alteration secondary to mild rear limb
lameness, potassium depletion, electrolyte alterations (cramps), and
postexhaustion laminitis (founder).
Intracellular potassium in normally released by the contracting muscle
cells. This local potassium release is believed to be one of the key
mediators of the increased blood supply to exercising muscles. Potassium
depletion has been suggested as a cause of poor performance and muscle
problems in horses. Further research is necessary to evaluate the role
of potassium depletion in some forms of tying up.
Recent studies have indicated that some forms of tying-up syndrome may
be related to electrolyte imbalances. Screen tests using both blood and urine
may be helpful for determining if electrolyte deficits exist and, if so, what
type of electrolyte supplement would be beneficial.
Less severe muscle problems can occur instead of tying up. Among the
muscle problems believed to be related to fluid and electrolyte imbalances
are stiffness and pain associated with muscle cramping and spasms, as seen
most frequently in endurance horses. These signs may represent one form
of the exhaustive horse syndrome because muscle problems are more common in
hot weather wherein dehydration and electrolyte imbalances play a role.
These horses generally do not develop tying-up and the muscle cramping
usually subsides with walking. Whether this problem is associated with a
temporary alteration in blood flow or a combination of heat and electrolyte
disturbances, as seen in human athletes with "heat cramps" is unknown.
Once the cramps have resolved, these horses may be able to proceed with
exercise.
Those with tying-up syndrome, however, in which damage to muscle fibers
has occurred, may become worse with walking. Muscle pain, stiffness and
sweating are generally more severe. Treatment consists of rest, analgesics,
non-steroidal antiinflammatory drugs, such as phenylbutazone, and fluid
therapy to correct accumulated deficits and to assure adequate urine flow.
POSTEXHAUSTION DISORDERS
Researchers at the University of California, Davis, Veterinary Medical
Teaching Hospital (VMTH) have recognized an unusual and often disastrous
postexhaustion syndrome in endurance horses. Several horses had been on
endurance or long trail rides during the summer two to four days before
being seen at the VMTH. During the ride, they showed mild signs of
exhaustion and didn't recover well. Conditions seemed to stabilize in
these horses, but they remained depressed and had little appetite.
Treatment, if any, consisted of the administration of non-steroidal
antiinflammatory drugs, such as bute, with little or no fluid replacement
therapy.
These horses were later found to have sever muscle damage,
gastrointestinal ulcers, kidney damage, and in some cases, founder. The
cause of this postexhaustion disorder are unknown, but fluid and electrolyte
imbalances and compromised kidney function seem to play a central role.
Non-steroidal antiinflammatory drugs, sometimes given at high doses, had
been the sole treatment prior to the presentation in many of these cases.
Though it is common practice to give horses phenylbutazone (bute), the
similarities between the pathological features in these horses and those
described for for phenylbutazone intoxication may be more than coincidental.
Perhaps if more vigorous treatment, particularly corrective fluid therapy,
had been instituted earlier, the serious complications would not have developed.
It is necessary to be aware of the potentially disastrous complications in
horses that fail to recover normally following endurance exercise. If a horse
does not recover well in a day after a strenuous ride, a veterinarian should be
contacted immediately.
SUMMARY
The medical problems associated with overheating and work stress in horses
can be very serious. By recognizing the early signs of distress, one can
initiate prompt treatment before it progresses too far. Rigorous training
schedules several months before any competitive event are necessary to
condition the entire horse's body. The extended training and conditioning
period also provides a non-competitive period in which the horseman develops
an understanding of what his horse can and cannot do.
Hot and humid weather create and extra stress on a horse's system and
horsemen should be particularly aware of their horses' physical responses
during these conditions. If possible, avoid exercising during the heat of
the day when temperature and humidity are high. Horses should have access
to shade, a well ventilated area, salt and clean feed and water. Clip long
hair coats if training continues in late fall or early spring. Experienced
horsemen who know their mounts are often able to recognize impending
problems and initiate proper care before the problem becomes serious.
TABLE 1
Symptoms...Exhausted Horse Syndrome
1) Sever depression and lack of appetite
2) Dehydration with lack of thirst
3) Persistently elevated temperature, pulse and respiratory rates
4) Increased capillary refill time and weak pulse
5) Lack of intestinal sounds, dilated anus, occasional colic
6) Irregular heat beat
7) Muscle cramps
8) Synchronous diaphragmatic flutter (Thumps)
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THE PURPOSE OF VITAL SIGNS
by HELEN BIASATTI HILL
as published in THE QUARTER HORSE JOURNAL, April, 1992.
Your horse is not eating and drinking. Otherwise, he looks fine. Is
he sick?
Maybe.
Even though the horse cannot tell you that he's feeling bad, external
changes such as listlessness and a change of attitude let you know that
something's wrong.
"It's important for horse owners to look, be observant, and think,"
said Dr. Mike Martin, a veterinarian and instructor at Texas A & M's
College of Veterinary Medicine in College Station. "I always tell my
clients that for every nine things they'll miss for not looking, they'll
only miss one for not knowing," he said.
There are basically three things the horse owner should know in order
to tell if the horse is healthy or sick. Called vital signs, they are
temperature, heart rate and respiration rate. "These three vital signs
are specific measurements that can be performed by the horse owner.
However,they don't always answer the question of what is wrong with the
horse. If they are normal, they can rule out some problems. If they
are abnormal, then they alert the owner to certain ailments."
The horses normal temperature is 99 to 101 degrees Fahrenheit. His
average normal heart rate or pulse is about 35 to 40 beats per minute,
and the normal respiration rate needs to be anywhere from 8 to 16, with
an average of 12 beats per minute.
The temperature is acquired by placing a large animal thermometer in
the horse's rectum for about two to three minutes. "Anyone attempting
to take the temperature of their own horse should be careful," said
Martin. "Most equine thermometers have a clip that attaches to the tail
hairs to make sure the thermometer can be retrieved."
The animals digital pulse can be taken by placing the index finger on
the submandibular artery. Located under the jaw, this artery is where the
large cheek muscle meets the lower jaw bone. "It's almost the size of a
pencil and you can feel it," said Martin.
The pulse can also be taken on the digital artery, located at the widest
point at the back of the fetlock or ankle. "But using the jaw is much
easier," said Martin.
The veterinarian pointed out that if a stethoscope is available, you
can listen to the heart beats by placing it directly on the chest, behind
the left elbow.
To measure the pulse or heart rate, count the number of beats in 15
seconds, and then multiply the number by four. This is the fast way to
calculate the pulse rate, rather than counting the beats for a whole
minute.
The respiration rate is the number of times the horse breathes. Watch
the nostrils or the rib cage for breaths. Again, count for 15 seconds,
and then multiply the number of breaths by four in order to get a per
minute reading for respiration.
"You need to look at the quality of respiration, and see if the horse
has any labored breathing or unusual kinds of respiration," advised Martin.
Increased heart rate or pulse are often measurements of pain, especially
in colic cases. If increased, it is not uncommon for the veterinarian to
also listen for intestinal sounds in search of the source of pain. "The
best place to hear these sounds is the point just in front of the hip bone,
in the middle of the horses flank," said Martin.
By knowing the vital signs, an owner can better explain the horse's
abnormal conditions to the veterinarian. "If an owner is not sure of the
normal vital signs, I suggest he look at one or more normal horses and
compare his findings to the one he is concerned about," said Martin.
"Take the temperature of a normal horse, then take the temperature of the
one that you think is sick. The same goes for pulse and respiration."
But if the vital signs are normal on the horse you think is sick, then
you need to think of other possibilities. "A new approach to solving such
problems is called 'problem based learning,'" said Martin. "It's a method
of learning that's on the horizon in veterinary medicine and education."
Problem based learning is simply this: The problem is identified and all
of the possibilities that can cause the problem are investigated.
Case in point---Your horse is not eating or drinking water. His vital
signs are normal. He has plenty of fresh water, quality hay and good feed.
He is showing obvious signs of pain. Other neighboring horses are healthy
and eating well. What is wrong?
After turning the horse out for exercise the owner notices that he
immediately drinks water out of a puddle. The water source is examined
and the tank heater in the stall is found to have a short.
The answer---The horse is not drinking because of his fear of being
shocked, and due to the lack of water, he's now constipated and no longer
interested in eating.
Vital signs often tell you if your horse is sick or not, but sometimes
it's necessary to do some problem solving with some other facts and a little
common sense.
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