Effects of medication concerning Oxtox susceptibility??

[JT2]

I have heard and read that certain drugs such as insulin and others may increase the risk of oxtox in divers, my question is, why is this thought to be the case and is there any evidence to back it up medically? If there are medications that increase a divers chance of an oxtox hit my thinking is that there would surely be medicines the would be able to lessen the chances of an oxtox situation, am I off base here? Have there been any solid tests done on this topic or is it still in the theoritical stages? Thanks Docs!

[The Iceni]

Hi JT,

Where did you learn this?

In general it is thought that all stimulants can predispose to oxtox. Perhaps you should do a search on oxygen toxicity?

In general it is very unwise to take or prescribe any medicine just to counter the side effects of another. Better to avoid any medication when diving!

You mention insulin. As far as I am aware insulin does not have any effect of the mechanisms leading to oxygen toxicity but diabetics do have problems that may mitigate against diving.

These are BSAC's guidelines.

http://www.bsac.org/medical/g_diab.htm

Hope this helps.

[JT2]

Hi Dr. Paul, check out this thread http://www.scubaboard.com/showthread...hlight=insulin and scroll down to Scubadoc's first reply and you will see where I read this, it seems strange to me that insulin might have this effect and that is why I was looking for more information after doing a search on oxygen toxicity and not finding anything about the effects of insulin on oxtox. Thanks for the reply and once again it is Great to have you back!

[DocVikingo]

To the best of my knowledge, there are no studies in humans showing that stimulants affect oxtox one way or the other.

There has been speculation that the effects of CNS stimulants may be additive with those of increased partial pressures of 02, thereby predisposing to oxtox, but it remains just that.

I also know of no studies on insulin & oxtox, and rather suspect more conjecture based on its effects on metabolic rate.

As an aside, I endorse your remark, "Better to avoid any medication when diving!"

Best regards.

DocVikingo

[The Iceni]

JT2 once bubbled...
it seems strange to me that insulin might have this effect and that is why I was looking for more information after doing a search on oxygen toxicity

Well JT & DocVikingo,

Scubadoc's refers to a 30 year-old paper "Lambertsen and Clark in Pharmacol Rev 23:37-133, 1971 stated that the following increased the risk of O2 toxicity". They list what they consider the good and the bad, as far as I can see without any evidence one way or the other.

I doubt peer review would permit a current paper to claim such a list to be definitive without the evidence.

As you know CNS oxygen toxicity is quite rare. It is now known to be unpredicatable, both between subjects and for the same subject from day to day. As for medication, as I suggested pharmacologically there is a THEORETICAL risk with CNS sitimulants such as caffeine, ephedrine and pseudoephedrine (sudafed) but I fear these risks will never be proven let alone quantified.

As you know, I have a personal interest because it would appear I MAY HAVE suffered from acute CNS toxicity when using a pp O2 that is generally considered safe. In any case I was very unlucky.

Oxygen IS proven to be safe with a ppO2 of 1.4 or less.

[JT2]

Thanks for the reply scubadoc.

What I get from the article you put in your reply is that elevated blood glucose levels were shown to delay the onset of seizure, am I understanding that right? I know that it says the administration of glucose prior to oxygen exposure increased the time-to-seizure by 90%, but what I am wondering is was it the increased glucose in a "normal" rat that made the difference, or would increased blood glucose such as a diabetic might have from time to time also increase the time-to-seizure, what do you think? This interests me very much. Can any of you docs think of a reason why insulin or glucose might have an effect on the time-to-seizure?

[JT2]

Thanks for the link scubadoc!

[The Iceni]

scubadoc once bubbled...
Hyperbaric oxygenation (HBO) at different pressures produces significant increases in the regional cerebral metabolic rate for glucose (rCMRgl) of various neuroanatomical structures in conscious rats.

Hi Scubadoc,

I am not sure you understood what I was trying to say earlier. The research you quoted confirms that hyperbaric oxygen increases various markers for the excitability of the brain in laboratory rats.

I am trying to understand the practical apllication of these findings in human divers.

Are you and JT suggesting that insulin could be used to reduce the incidence of CNS oxygen toxicity in healthy divers or perhaps suggesting that insulin dependent divers should be encouraged to take a higher than normal insulin dose prior to a Nitrox dive?

This thread and the above posts and references suggest that high blood glucose is bad, low blood glucose (induced by oral hypoglycaemics or insulin) is good in preventing CNS oxygen toxicity.

I, for one, find this a little worrying.

[JT2]

Dr Paul Thomas once bubbled...

Are you and JT suggesting that insulin could be used to reduce the incidence of CNS oxygen toxicity in healthy divers or perhaps suggesting that insulin dependent divers should be encouraged to take a higher than normal insulin dose prior to a Nitrox dive?

:whoa: How in the world did you come up with that from my post????? The way I understand the article is that Insulin was shown to have decreased the time to seizure,(meaning that the subject given Insulin would have a seizure quicker) and that glucose was shown to increase the time to seizure(meaning that the subject given glucose could endure the exposure longer before seizing), am I understanding this wrong? Regardless of the article, I just simply asked if any of you doctors could think of reasons why Insulin or glucose might have an effect on time-to-seizure, that's all, in no way did I or do I recommend that anyone try any of these things on themselves or others.

[The Iceni]

JT2 once bubbled...
:whoa: How in the world did you come up with that from my post????? .

Hi agin JT,

I am having difficulty in working out what you are trying to say. Admittedly I read the various posts quite rapidly and it seems wrongly but I thought the results were contradictory, which is not to be unexpected in such laboratory research.

However, well spotted.

Hypoglycaemia is one cause of fitting.

In summary, Glucose good Insulin bad? (The reverse of what I posited earlier.)