I only know human medicine, but not animal medicine. The two can differ greatly. I’ve experienced hyperthermia a couple times myself and treated others that have succumbed heat stroke. Hyperthermia is one of the risks of sailing, working out on a deck while exposed to the hot sun. The guys I watch closely are the ones who have partied heavily the night before, or are known to be on certain prescription meds.
Initial Stage:
Excessive sweating.
They appear to be excessively red in the face.
Fatigue
Mild confusion. You will first notice this in their speech and hesitant movement. They aren’t thinking straight.
Lack of balance and coordination.
Dizziness
Muscle cramps.
Mild to severe tremors due to lack of electrolytes.
Hyperventilation.
Headache
Tachycardia: a regular heart rhythm over 120 bpm.
Hypertension
Slight nausea: difficulty holding down water, but they must try. Short of an IV, this is the only way to get water into them.
Since dogs sweat primarily from their tongues, there should be excessive saliva. If the dog looks ratty and damp, that is very extreme. Normal heart rate for small dogs is anywhere between 60 and 140bpm. Normal for big dogs is 60 to 100bpm.
Body temp of about 102–3F. If these guys don’t get into the shade quick, drink room temp water, dowse themselves with water, or wrap themselves in a wet sheet, and lie down, it can quickly progress to symptoms of heat stroke. Placing ice packs where the arteries are close to the surface such as under their arms, under their crotch and at their neck will quickly reduce their body temps. O2 is nice, if it is available. Have someone monitor the victim closely, especially their pulse and skin color.
The victim should be OK in about a half hour, but they are done for the day. At this point, it is all about hydration, hydration, hydration. Foods with magnesium, potassium and calcium are recommended to replace important electrolytes that were lost during excessive sweating. A banana or two is good. Sleep. I have no idea what food you would offer a dog.
Counterintuitively, ice water is not recommended because as it passes down the throat and along the aorta and past the struggling, overheated heart, the heart can be thrown into shock resulting in sudden cardiac arrest.
Signs and symptoms of advanced hyperthermia:
Nausea and vomiting.
The sweating stops. Body temp of 104+. They become dry, cold, very pale and are in and out of consciousness. The victim is now in real danger as their parasympathetic system has gone haywire. It has reached the tipping point.
Their body temp is so much higher than the air temp around them that the parasympathetic system is now reacting as though they are in cold weather and those reactions to cold are now kicking in, which includes shivering, muscle rigidity and other involuntary actions that raise the body temp further.
Extreme confusion when conscious.
Muscle rigidity.
Tremors and shivering.
Agonal breathing.
Irregular Tachycardia: An irregular heart rate of about 120 bpm or more with *hypo*tension. The pulse is weak and thready The blood pressure drops because the heart is beating so fast and irregularly—inefficiently—that there is very little real cardiac output. This is a sign that the person is now in risk of stroking due to clots forming at sharper curves in the arterial system throughout the body, especially the brain, lungs and coronary arteries.. If this continues, you will lose them. It is also possible that they have lost so much body fluids that their blood volume is too low to handle this emergency. This is hypovolemia due to prolonged hyperthermia.
Then, Bradycardia. The heart rate slows down significantly below 40 bpm. You are losing them.
First aid while waiting for the EMTs: This is where first aid people differ. Some say the person needs to be wrapped in a dry blanket and removed to a dark, cool place in a reclining position with their head at the same level of their heart and turned to the side to prevent aspiration of vomit, The other school of thought is that the body temp must be lowered as quickly as possible without causing a cardiac event. So, I will do all the above, but still wrap them in a wet sheet regardless and monitor their vitals closely—but I have a stethoscope and BP cuff onboard and know how to use them—it can be quite some time before the coast guard helicopter gets to my position. 02 is very helpful to help them remain conscious and deliver badly needed O2 to the heart muscle. If I don’t have an 02 tank available, I put them on regular air via a scuba outfit. The delivery is much better. If they stop breathing altogether, CPR breathing is recommended, or better yet, employment of an ambu-bag. Less work and leaves you the ability to simultaneously monitor vitals.
Then, when conscious, they should be offered room temp water when conscious. Be prepared for projectile vomiting. But don’t give up. Cool, wet rags to arteries after the shivering stops and the BP rises and the HR is regular. When condition improves, go with the ice packs. O2 is very helpful.
Sorry about the length. I’m trying to cover all bases.