Visiting Veterinarian

Winter hazards threaten pets

By Michele Gerhard Jasny V.M.D. - February 15, 2007

When old man Winter finally blew in this year, he did so with a vengeance. It's freezing out there. Every year I get at least one call about a dog who is shaking all over and the owner doesn't know what's wrong. People somehow fail to notice that it's three degrees outside and their dog is more-or-less naked.

Dogs and cats get cold, just like we do. Okay, not exactly like us. Their fur coats provide insulation, but they do need time to get accustomed to weather changes. Little dogs, in particular, may have trouble handling sudden cold snaps. Animals who are old or injured have a greater risk of succumbing to the combined effects of illness and exposure. And even big healthy dogs can get chilled. On the other hand, I once had to defend the reputation of some poor fellow at a party who was being maligned for keeping his dogs outside year-round. The guests were sure this bordered on inhumane. Not necessarily true.

As long as a dog is acclimated to the cold, given adequate shelter from wind and rain, and is of appropriate age, breed, and robustness, outdoor living is fine. Admittedly, it's not the middle-class suburban vision of the life for a family dog, but nonetheless an acceptable option embraced by working dogs for centuries. As owners of northern breeds like Samoyeds will confirm, some dogs love the arctic weather. Just make sure their water bowls don't freeze. If really bitter weather or a storm is expected, I still advise bringing everyone inside.

So what happens when your pet, Snowball, gets cold? First, she will alter her behavior to try to conserve heat by seeking shelter or curling up. Her fur will puff up (called piloerection), trapping a layer of air close to the skin that serves as an insulator. She will shiver. The tiny muscular contractions generate internal heat. Her body will protect core functions by constricting the peripheral blood vessels, focusing the circulation of her warming blood to her heart and brain. If all of these mechanisms fail to maintain a normal core temperature, her body temperature drops below normal. That's hypothermia.

Any condition that impairs Snowy's heat production or conservation predisposes her to hypothermia. Smaller animals are more susceptible because of the larger skin surface in proportion to body mass. Short coats provide less insulation than heavy ones. In the very young and very old, thermoregulatory mechanisms may simply not function effectively. Thin animals have less heat-conserving body fat. Older, arthritic dogs, or those with any condition that impairs mobility, tend to move less. Physical activity keeps you warm. Sitting still outside, you get cold. Heart disease and endocrine abnormalities such as hypothyroidism also increase risk. If Snowy is a fat, fluffy, healthy, two-year-old Samoyed, with a sturdy insulated doghouse, who has been living outside all fall, she won't even notice when it drops below freezing. If she's a scrawny, 14-year-old Chihuahua invalid who never leaves Mama's lap, that's another story.

One common situation resulting in hypothermia is when a pet is injured or lost outside. Take Gramps, a skinny, old, arthritic, partially blind terrier. One fall afternoon his owners took him out in the yard. In the past, Gramps had basked happily on the sunny deck while the owners did their landscaping, but this time he wandered off. Busy raking leaves, they didn't notice his disappearance until dusk. A frantic search of the surrounding woods yielded no clues. Calling his name was fruitless. Gramps was completely deaf. They alerted their neighbors and the Animal Control Officer. Everyone was mobilized, searching. Midmorning the next day, he was found half a mile away. He had waded across a little creek; then, wet and confused, he stumbled into a ditch, injured his leg, and was unable to extricate himself.

Early signs of hypothermia include mental depression, stiff gait, and lethargy. Shivering may be present but ceases as hypothermia worsens. Pupillary responses become sluggish. Breathing is shallow and irregular. The heart rate slows profoundly slowed and arrhythmias may develop. Blood pressure plummets. Eventually reflexes disappear, pupils are fixed and dilated and the individual falls into a coma. Severe cases may be mistaken for dead. (In human medicine they say, "You're not dead until you are warm and dead.")

Moderate to severe hypothermia is life-threatening, but treatment must be handled appropriately to avoid worsening the situation. Too much movement may precipitate lethal heart problems. Patients should be transported slowly and carefully. Then rewarming can begin. There are three types: passive, active external, and core. Passive rewarming is for mild cases and consists of wrapping in blankets and letting the body's natural heat-producing abilities correct the problem. Active external rewarming adds additional heat sources such as hot water bottles or heating pads. These should not be applied directly to the skin. They should be concentrated around the chest, focusing on restoring core temperature first, not extremities. Core therapy uses internal methods such as warm intravenous fluids, warm air to the lungs, warm fluids into the stomach or colon, or into the abdominal cavity by a technique called peritoneal lavage. The complicated interplay of circulation, fluid balance, and heat transfer involved can occasionally result in sudden death called "rewarming shock."

As I rubbed Gramps's legs, I thought back to other cases. There was the Samoyed who fell through the ice on Tashmoo. He struggled for a long time in the frigid water before being rescued, but bounced back with little more than a bowl of warm broth and a blanket. At the other extreme was a horse that had fallen at the top of a steep hill during a blizzard and couldn't get up. By the time I arrived, the owners had been trying several hours to get him to his feet. Fighting through the driving snow, they led me to where he lay on the exposed crest. He was stiff and stuporous, his extremities icy cold. They had thrown a few blankets over him but not enough, and his lower legs protruded from the meager covers. Barking instructions, I placed an i.v. catheter into his jugular vein. One helper was assigned to stand holding the bag of fluids up in the air while I attached the line to the catheter. The wind was so fierce the fluids froze in the tubing as we tried to get the drip running. People ran back and forth to the house for hot water bottles. I lost the feeling in my fingers. My feet went numb. Somehow we managed to warm and rouse the horse sufficiently that he began to try to get up, but his feet kept slipping on the ice and he didn't have the strength to rise.

We got buckets of sand, bags of shavings and kitty litter - anything we could think of - and spread it around for traction. Finally, after multiple attempts, we got him up. He shifted unsteadily back and forth on half-frozen legs. He needed to get out of the storm and into the barn. With people supporting him on all sides, we started gingerly down the hill. One step. Two steps. Three. On the fourth step, he collapsed into the snow. This time, there was no getting him up. So cold I could barely hold the syringe, I euthanized him where he lay.

As Gramps began to rally, I hoped for a happier outcome, but he was too badly injured. Although we restored him to normal body temperature, the leg injury was severe. This, combined with his age, and other disabilities, led to the decision for euthanasia.

It's cold out there. Keep close track of your pets, especially the elderly. And get the Chihuahua a sweater.

Portions of Ms. Jasny's column this week were previously published in The Times.