1. The problem – The solution
Patient Warming
The problem – The solution

2. Peri-Anesthetic Hypothermia
Peri-Anesthesia Hypothermia occurs in up to 80% of anesthetized cats and dogs

3. Peri-Anesthetic Hypothermia
Hypothermia is associated with:
Prolonged healing
Increased dysrhythmias
Increased blood loss
Increased infection
Patient morbidity
Technician/nurse time
Dentistry is the #3 procedure most likely to end in anesthetic death
50% of anesthetic deaths occur during recovery
Go to Making Anesthesia Easier blog post
“Hypothermia and the Veterinary Dental Patient”

4. Peri-Anesthetic Hypothermia
A review of the survival rates of Yorkshire Terriers after portosystemic shunt surgery showed the single most prognostic indicator for survival was postoperative temperature.

5. Peri-Anesthetic Hypothermia
Contributors:
Small body size
Drug-altered peripheral perfusion
Intubation bypasses the nose
Breathing cold gases
Radiated heat loss from skin surface
Open body cavities
Water during dentals

6. Each stage of a procedure presents unique hypothermia challenges…
Premedication
Clip and Prep
Surgery
Recovery

7. Peri-Anesthesia Hypothermia Study

8. During Premedication
Premedication causes the first signs of hypothermia. Dogs and cats typically lose 1º to 2ºF over 30 to 45 minutes before induction of anesthesia (blue line).

9. During Clip and Prep
The precipitous, critical loss of 2º to 5ºF body heat occurs in the first 15 to 30 minutes after induction: during clip and prep time (blue line).
The patient may lose as much as 7ºF before you ever begin the procedure

10. During Surgery
Once the animal is draped for surgery, heat loss slows (blue line).

11. During Recovery
Warming hypothermic animals recovering from anesthesia is a slow and labor-intensive process, often taking more than 1 to 2 hours

12. Traditional prevention ineffective
Prevention and treatment of hypothermia has focused on body surface warming and has proven to be ineffective (blue line) …And sometimes dangerous

13. Common devices can cause harm
The margin of safety to prevent significant thermal injury is surprisingly narrow.
Skin can burn from as little as 115ºF of constant surface heat for one hour. (Hot tap water is warmer than 115ºF)
Warm water jugs, heated rice or wheat bags, 'on-off' electric heat pads, and any other warming device not specifically designed for sedated or anesthetized animals can cause severe burns.

14. Common devices can cause harm
Sedated, anesthetized, and recovering animals can't move away from excessive heat.

15. Common devices can cause harm
Zelda – February 2017
Standard electric heating pad used during dental
Skin changes took several days to manifest
Hair loss
Redness
Moist desquamation
Ulceration
Progressed over the next week
Underwent three reconstructive surgeries at referral hospital (WSU)
Died during the third surgery
20 days after dentistry

16. Safe and effective warming
Thermostatically controlled warm air blankets safely distribute heat evenly and constantly.

17. Solving Peri-Anesthesia Hypothermia
It’s easier to prevent hypothermia than to overcome it

18. 3-step solution to hypothermia
Pre-warming
Warmed inspired gases
Warm air blankets

19. 1. Pre-warming

20. Pre-warming; like pre-oxygenating
Thermal support before anesthesia prevents the initial 1o – 2oF drop in body temperature and slows the critical rapid heat loss immediately following anesthesia induction

21. Pre-warming safely
A Warm Air Blanket System can safely deliver air at a constant 109ºF and effectively pre-warm caged animals before anesthesia.

22. 2. Warmed Inspired Gases

23. Warm from Within
Patient warming is now as simple as using a better breathing circuit

24. Capture Control at Intubation
Warmed inspired gas allows you to capture control of a patient’s body temperature from the moment of intubation, at induction.

25. Warmed inspired gases
Rapid heat loss occurs after induction as an animal is moved during the clip and prep period
Positioning results in poor surface heat transfer from heated pads or mats.
Surface heating is not sufficient to overcome this stage of hypothermia

26. Warmed gases prevent heat loss
The rapid loss of 2o – 5oF that occurs during the clip and prep period can be prevented by delivering warmed inspired anesthetic gases from the moment of intubation.

27. Your choice of circuit is important

28. Rebreathing Circle System + / -
Advantages:
Disadvantages:
Keeps patients warmer
Retains moisture
Efficient use of gas
Versatile – use with a wide range of patient sizes
Lower gas flow = lower cost
Lower gas flow = less pollution
Lower gas flow = less heat loss
Increased resistance
Many parts
Slow % concentration change

29. Non-Rebreathing System + / -
Advantages:
Disadvantages:
Minimal resistance
Few parts
Rapid % concentration change
Patient loses body heat
Patient loses moisture
Inefficient use if gas
Narrow range of patient sizes
Higher gas flow = higher cost
Higher gas flow = more pollution
Higher gas flow = more heat loss

30. Overcome the high cost of NRB circuits
Non-Rebreathing Circuits are expensive to use:
They cost more money to use
10 X more oxygen flow than rebreathing circuit
10 X more anesthetic gas flow than rebreathing circuit
They cost patient body heat
High oxygen flow syphons heat from patients
They cost the environment
10 X more anesthetic gas flows into the atmosphere

31. Examine hospital policy
When do you use a non-rebreathing circuit?
Choose a non-rebreathing circuit for patients weighing less than ? pounds
Why that number?
I’ve seen target weights from 20# to 5#

32. For more information “Rebreathing or Non-rebreathing?”
Read Making Anesthesia Easier blog post:
“Rebreathing or Non-rebreathing?”
Go to DarvallVet.com and follow the link to the blog

33. 3. Warm Air Blankets

34. Warm Air Blanket Systems
Warm air blankets with high surface air flow (designed for humans) are unable to raise the body temperature of hypothermic dogs and cats during anesthesia. Warm air blanket systems designed with a porous patient contact surface permit the hair-coat to trap warm air, holding it close to the patient’s body.

35. Warming effectively
Recent research shows that only the Darvall warm air blankets can consistently raise body temperature under anesthesia.
Darvall Blankets make all warm air blowers work better

36. Peri-Anesthetic Hypothermia
Hypothermia is associated with:
Prolonged healing
Increased dysrhythmias
Increased blood loss
Increased infection
Patient morbidity
Technician/nurse time
Dentistry is the #3 procedure most likely to end in anesthetic death
50% of anesthetic deaths occur during recovery
Hypothermia is a likely contributor
Go to Making Anesthesia Easier blog post
“Hypothermia and the Veterinary Dental Patient”

37. To recap: 3-step solution
Pre-warming
Prevents initial 1o – 2oF heat loss
Warm inspired gases
Prevents 2o – 5oF loss during clip and prep
Warm air blankets
Porous blanket / low air flow traps heat, warms animals

38. Thank you for your attention

39. Questions?

40. This presentation is provided with support from:
For a copy of this slide deck Ken Crump