Keeping an animal warm during anaesthesia is of critical importance. The HotDog warmer is one piece of equipment we have bought to help keep your pet warm, but it is only one of many steps we take before, during and after every anaesthetic. The methods we use are:
- Reducing heat loss by
- wrapping the animal in special blankets
- placing bubblewrap over unclipped areas
- placing socks to stop heat loss from the animal’s feet
- not overclipping the surgical site
- avoid the animal getting too wet
- keep the length of the anaesthetic to a minimum
- Using external heat source
- a thermostatically controlled heated operating table
- a HotDog warmer (sorry cats but you can use it too, we didn’t decide on the name!)
Want to know more?
When an animal (or a human) undergoes a general anaesthetic their body temperature will naturally reduce by 1 degree every 40 minutes. This happens because
- the anaesthetic suppresses the body’s normal responses to a decreasing temperature.
- lack of muscle activity means less heat is produced.
- if the surgery involves opening a body cavity (which is required in many operations) the rate of heat loss is increased significantly.
Once the body temperature drops, it is more difficult to warm them up, so keeping them warm from the outset will improve their care.
The normal body temperature of most animals is 38-39 degrees centigrade. If this drops below 37 degrees, it is classified as hypothermia. Hypothermia has been associated with a number of postoperative complications
- reduced cell metabolism- meaning it takes longer for drugs to be cleared from the body
- reduced carbon dioxide production- affecting breathing under anaesthesia
- swelling of red blood cells- causing the blood to become thicker and leading to reduced blood flow to the brain
- reduced oxygen transfer to the tissues
- increased clotting times- increasing the risk of bleeding
- increased wound infection rates
- increased risk of abnormal heart rhythms
- increased recovery times from anaesthetic
As a hypothermic patient recovers from anaesthesia; shivering and narrowing of the blood vessels (vasoconstriction), are some of the first responses to return. Although these increase heat production, they increase oxygen demand and cardiac workload significantly. They also lead to reduced blood flow to the skin, increasing the risk of wound complications.
There are 2 ways of preventing hypothermia
- insulating the animal against heat loss – this involves the use of blankets, bubble wrap, socks, minimal clipping, not over-wetting the animal when preparing the surgical site
- providing an external source of heat to the animal – external heat supplies include hot water bottles, snuggle safe, heat pads, warm air blowers and the HotDog Warmer
Complications of warming patients
Using external heat sources are not without risks. When an animal is asleep, it is unable to move away from uncomfortable temperatures and can result in thermal burns or scalds, which may not show until several days after the event. Equipment that is thermostatically controlled is much safer to use.
The HotDog patient warmer is an air-free, water-free, state-of-the-art warming system. Efficient warming is delivered by a flexible, lightweight conductive fabric inside of the HotDog blanket. It can be wrapped around the animal, meaning it can warm the animal from above and below simultaneously. It reduces the risk of thermal burns by not storing heat, only emitting it at the set temperature. It also radiates heat and so can create a warm micro-climate
Air-free HotDog patient warming is safer for surgeries involving implanted foreign materials—such as orthopedic and cardiac surgery—because there is no waste heat disrupting the sterile field with contaminants. Rising waste heat from forced-air warming contaminates the sterile surgical field above the table with dirty air from the floor by generating convection currents.
We also continually monitor our patient’s temperature as part of our anaesthetic monitoring.