Why does anestesthia make me cold?

Factual Questions
1

Day surgery, dentist visit, gas, Novocaine. I get a similar effect regardless.

I get a chill that I can’t throw. No amount of clothing or blankets seems to help. I’m not a very big person, slight, under 110 lbs probably, but that shouldn’t make a difference since the drugs would be in ratio to that, right?

I recently returned from the dentist, never fully sedated, gas, lots, I mean, lots of shots of Novocaine (trouble getting it frozen) and was so chill my teeth began to chatter.

I was fully dressed, had a fleece vest, a very heavy wool sweater and two wool blankets on me and I still felt cold.

Experience has taught me to just wait it out, it does wear off after a few hours.

But I’m wondering why is this? What’s going on in my body?

2

The drug that causes the numbing has a side effect of making your blood vessels dilate, allowing more blood to flow around the area of the injection. This is undesired because you want the numbing drug to stay where the operation is going take place as long as possible and not spread out all over your body. The dilation effect is countered by combining it with another drug to constrict the blood vessels, which would make you feel colder.

From the Novocaine Wikipedia page (Procaine - Wikipedia):

“procaine is a vasodilator, and is often coadministered with epinephrine for the purpose of vasoconstriction. Vasoconstriction helps to reduce bleeding and prevents the drug from reaching systemic circulation in large amounts”

3

FYI dentists stopped using Novocaine decades ago because a lot of people are allergic to it. They use lidocaine now.

4

Really? I had a lot of dental work and my dentist always said novocaine but he could’ve been saying that and using lidocaine.

5

They probably use the term Novocaine because people expect to hear that - no need to get people worried for no reason. Sort of like people saying Band Aid when they use another brand.

 I don't think any dentist ever told me what they use but when I found out they use lidocaine I asked my dentist and she said  lidocaine is what she uses.
6

Thanks for the explanation ICBM, I understand what you said but still don’t quite understand why that makes me cold.

Like my dental visit, the gas had worn off almost immediately upon stopping inhaling it and the Novocaine was only pumped into my face. How does that make my whole body cold?

7

epinephrine is mixed with the anesthetic to cause blood vessel constriction with the intent of keeping the anesthetic in the area it was injected. if you got a number of shots there is more of this that might migrate out into the rest of your body. also with a number of shots it is possible that one got close to a larger vessel and had some amount make it into your general circulation.

8

And this is doing what, exactly? Keeping my internal body heat from circulating? Dropping my core temperature?

Sorry, I’m an arty not a science nerd, so I’m not quite getting it.

9

it would reduce blood flow to your skin, nerves in your skin would sense being cooler.

10

Thank you for the clarification, that does make it more understandable.

But I have one more question, if you don’t mind.

The injections were all in my jaw. Shouldn’t just my face or head feel cold? That would make more sense to me, rather than my whole body thinking it’s cold. The drugs they injected me with only affected that area, nothing else grew numb.

11

I don’t quite understand the effects of having dental work, either. I get the full sedation dentistry, and they swaddle me in heated blankets while the work is being done (which, frankly, is quite nice). I don’t plan anything for days where I go to the dentist (even without sedation) except coming home and resting - it seems to be a shock to your system.

12

Note that this is only a false sensation caused by these drugs.
If you were to use a thermometer to take your temperature, it would actually be at your normal body temperature, something around 98.6º. You are not really chilled, it just feels that way.

13

That’s a good point Cat Whisperer, whenever I’ve had surgery, they always give you a warm blanket before putting you out, I’d forgotten about that.

I am very surprised to learn it’s a false sensation, although that would explain why I truly can’t get warm no matter how many blankets I use.

And although the main chilling effect wears off after several hours, for the next couple of days I still get a chill really easily.

14

Many different anesthetics can mess with postoperative hermoregulation.
Here’s one study concerned with limiting the effect:
Amino acid infusions during general anesthesia induce thermogenesis and prevent postoperative hypothermia.

15

if one of the injections were near a blood vessel some of the fluid would get into your whole circulation system. the anesthetic would affect sensory nerves be too dilute to affect your body. the epinephrine would have an effect on your circulatory system elsewhere.

16

So how do I get more amino acids?

17

Protein, baby.

18

The last time I had a jaw numbing injection for a filling, I suddenly felt the same as if in the grip of a surge of panic. I’m not a white knuckle dental patient, so I asked the dentist if there was some sort of stimulant in the injection and he said “Yes, caffeine”.

Are there Novocaine variations with caffeine or was my dentist wrong and they’re all made with epinephrine?

19

I think there may be some psychological thing to it. I used to get shot with novocaine or lidocaine or whatever and that night I would sleep so well. Now I know that getting a shot at 2pm and having it wear off completely by 4pm, there’s no way when I go to bed at 11pm I should have any after effect.

But I tell you I always slept better. I’m 99% certain that had to be a psychological effect.

20

For surgery it’s not a false sensation. ORs are kept cold and you’re not moving and not generating much heat.