Hypothermia, a body temperature below 99 degrees Fahrenheit, can lead to many harmful consequences for your warm-blooded patient under sedation or anesthesia.
The condition slows metabolism. It reduces transformation of anesthetic drugs and in turn, delays recovery of the patient. “Cold” patients are more prone to infections and delayed healing.1
Ask yourself these questions next time you see an anesthetized patient in your hospital:
- Is the patient covered by a towel or a blanket?
- Is the patient on a cold X-ray table while waiting for the doctor to review radiographs?
- Is the patient on a cold metal grid on a wet sink?
- Is this patient skinny or young, i.e. with little body fat to prevent heat loss?
- Are you overly generous with the scrub solution and the alcohol rinse before surgery?
- Is the patient on a heating pad during surgery?
- What is the temperature of the IV fluids?
When you become aware that you are pouring IV fluids at room temperature (let’s say 70 degrees Fahrenheit) into a patient with a body temperature hopefully above 100 degrees, you understand this is simply not a good way to keep a patient warm.
Let’s review 25 of the many ways you can prevent and treat hypothermia before, during and after surgery.
During Patient Preparation
1. This is the period between induction of anesthesia and the skin incision. It entails multiple steps, including intubation, catheter placement, clipping, X-rays, setting up on the operating table, placing ECG leads and scrubbing the skin. As much as possible, keep a towel or a blanket over and under your patient when outside the operating room.
2. Strive to minimize soaking the patient with scrub solutions while scrubbing, as well as with alcohol when placing ECG leads. Since alcohol evaporates, you may want to switch to a special gel to maintain good contact during the entire surgery.
3. Minimize anesthesia time. One study2 showed that each additional minute of anesthesia increases the risk of skin infection by 0.5 percent. That doesn’t sound like much until you figure out that each additional hour under anesthesia increases the risk by 30 percent.
It is therefore important to become as efficient as possible while placing IV catheters, taking X-rays, clipping and prepping. Then you need to get your doctor into the OR as quickly as possible.
4. The surgery table should be covered by a towel to avoid contact between the patient and the cold surface.
5. The heating pad should be covered by a towel to reduce the risk of skin burns.
6. If the doctor uses electrocautery, warm up the cautery plate on the heating pad well in advance, again to avoid contact between the patient and the cold metal. Obviously, the size of the cautery plate does not match the size of the patient. So this is even more important in a toy poodle than in a German shepherd.
7. Place warm fluid bags (strictly reserved for this purpose) against the body or near major blood vessels like arm pits and inner thighs.
8. Some practitioners use microwaved bubble wrap on non-clipped body parts. Whether it is efficient or not is debatable.
9. Wrap cellophane or foil or towels around the feet, or use socks. Even better, according to one study3: Wrap the feet with a warming blanket if possible. This may be helpful because the feet offer a rich arteriovenous network, which leads to heat loss.
10. Place the endotracheal tube between two warm fluid bags.
11. Decrease the oxygen rate as much as reasonable.
12. Use a Humid-Vent adapter on the endotracheal tube. It is meant to minimize the loss of humidity from the patient and may reduce heat loss.
13. Use a coaxial anesthesia hose (type F) instead of a regular anesthesia hose. The warm exhaled gas warms the cold inhaled gas.
14. Use a forced-air warming blanket (e.g. Bair Hugger).
Work From the Inside
Because the techniques described above may not prevent hypothermia, especially in small pets, you may need to warm your patient during surgery. This can be done from the inside out.
16. Warm the fluids in the IV line. You can purchase a fluid warmer or simply coil the IV line around a warm fluid bag. You also can lay it on the heating pad. Regardless of the system, it is important to do it as close to the IV catheter as possible so the fluids don’t cool before entering the patient.
17. Use warm IV fluids, kept in an incubator or heated in a microwave. They should be at body temperature.
18. Use warm lavage fluids when rinsing the abdomen, again from an incubator or microwave. One study4 showed that fluids at about 110 degrees increased the patients’ temperature from 94 degrees to 97. The only problem is persuading your doctor to leave the lavage fluids in the abdomen for two to six minutes.
19. A little bit fancier for severe hypothermia: Give an enema with warm fluids, or infuse the bladder via a urinary catheter. Please note that a warm enema will preclude using a rectal thermometer, so you will need an ear thermometer to monitor the temp afterward.
20. Purchase an esophageal warmer (Gaymar 800-828- 7311). The device, placed in the esophagus, warms the patient “from the inside out.”
Your best efforts still may not prevent hypothermia. Therefore, it is important to continue to warm your patient after surgery.
21. Check and record the rectal temperature every 30 minutes until it is normal. Without vigilant monitoring, it is easy to go from hypothermia to hyperthermia, especially in cats and small dogs.
22. Some clinics use heating lamps. They may be acceptable as long as hyperthermia or skin burns don’t occur.
23. A heating pad or warming blanket can be moved from the OR to the recovery area. If possible, it would be ideal to have a dedicated warming device just to recover patients.
24. Use towels or a blanket warmed in the dryer. Be sure to cover the feet to decrease heat loss.
25. Continue any of the above techniques as needed during the post-op period. Example: Warm the IV fluids or use warm bottles.
As you become familiar with the techniques, you will notice that some work better for you than others. Or that you like some methods and dislike others. What matters is that you become proficient enough to tailor your techniques to each patient. In other words, it will be more challenging to maintain the temperature of a Yorkie during a lengthy laparotomy than the temp of an overweight Labrador during a quick ear flush.
Fighting hypothermia should become part of your standard protocol with any patient under sedation or anesthesia, whether they need X-rays, dental work, surgery or any other procedure.
Fighting hypothermia is good patient care.
Dr. Zeltzman is a small-animal board-certified surgeon at Valley Central Veterinary Referral Center in Whitehall, Pa. His website is www.DrPhilZeltzman.com.
*All photos courtesy of Dr. Zeltzman
- MW Beal, et al. “The effects of perioperative hypothermia and the duration of anesthesia on postoperative wound infection rate in clean wounds: a retrospective study.” Vet. Surgery 2000, Vol 29, N 2, p. 123-7.
- LW Cabell, et al. “The effects of active peripheral skin warming on perioperative hypothermia in dogs.” Vet. Surgery 1997, Vol 26, N 2, p. 79-85.
- MA Nawrocki, et al. “The effects of heated and room-temperature abdominal lavage solutions on core body temperature in dogs undergoing celiotomy.” JAAHA 2005, Vol 41, N 1, p. 61-67.