Can someone tell me how high the temperature of the blood in blood
vessels must be to be felt as pain? I am not looking for what
temperature is necessary to feel pain through the skin, but the
temperature threshold that blood vessels or any other organs must
reach to register as pain.

Some medical treatments involving magnetic fields, lasers, etc can
elevate blood temperature, and I want to understand how high the blood
temperature can be elevated before it becomes painful.

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Clarification of Question by lauren0125-ga on 20 Sep 2005 15:25 PDT

If you can't find the actual temperature, I will accept an answer that
provides sources that discuss this topic.

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Request for Question Clarification by welte-ga on 21 Sep 2005 15:25 PDT

Hi Lauren0125-ga,  Are you interested in a particular part of the body
(e.g. hyperthermia for treatment of breast cancer, etc.).

            -welte-ga

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Clarification of Question by lauren0125-ga on 26 Sep 2005 09:46 PDT

Any organ other than skin will be helpful. I need to know how high the
temperature needs to be in blood or internal organs to register as
pain.

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Request for Question Clarification by pafalafa-ga on 26 Sep 2005 12:33 PDT

lauren0125-ga,

I think that, for the most part, internal organs don't really feel
pain with anywhere near the same sensitivity as our skin.  As such, a
large rise in heat would do all sorts of damage to a body well before
it registered as a heat-related sensation of pain.

For instance, long before the blood were to heat up to a noticably
painful level (from the heat itself), the human body would be reeling
from the associated impacts of such a temperature rise.  Think about
how you feel when your blood temperature raises just three or four
degrees during a fever!  Now imagine a ten degree rise...you'd
probably be dead (or pretty close to it) long before any sensation of
pain arose directly from the heating up of the blood.


Perhaps if you can tell us a bit more about your interest in this
particular topic -- are you writing a story, for instance? -- then we
can provide some focused information as an answer to your question.

Thanks,


pafalafa-ga

Hi again Lauren0125-ga, and thanks for your question.

As I mentioned, probably the most data on this topic has been
accumulated from experience in the treatment of tumors via
hyperthermia.  Hyperthermia uses focused ultrasound, radio-frequency,
or microwaves to raise the temperature of  tissues (or organs) while
sparing the skin.  Hyperthermia is typically performed by a radiation
oncologist, often in conjunction with radiation therapy.  If you'd
like some specific details on hyperthermia itself, I suggest posting a
separate, focused question on this topic.


The Palo Alto Medical Foundation is one of the centers in the US that
administers hyperthermia treatments.  They have a patient oriented
site that discusses the basics:
http://www.pamf.org/radonc/tech/hyperthermia.html

"Discomfort: The most common side effect of hyperthermia treatment is
a sensation of warmth and discomfort during treatment, which can be
managed with pain medications prior to or during hyperthermia if
needed. In addition, there may be some tenderness at the probe
insertion sites for a couple days following treatment."

This site also gives the limiting temperatures for treatment:

"Local or regional hyperthermia treatment most often involves the use
of ultrasound, microwaves or radio-frequency (RF)-induced currents to
raise body temperatures at a specific site. The temperature range
achieved is 41-45 degrees Celsius or 106-113 degrees Fahrenheit,
similar to a hot bath."

Typically, the goal for treatment is 42.5-43 degrees Celsius (108.5 -
109.4 Fahrenheit). Most hyperthermia is aimed at tissues 1-8cm beneath
the skin surface.  Deeper treatments are more experimental, but is
becoming more widespread as techniques are developed. I've assisted in
the administration of such deep hyperthermia treatments and know that
pain secondary to heat in the deep tissues is typically the limiting
factor.  Another concern is causing fat necrosis, but this typically
occurs at a higher temperature and longer duration of treatment than
one can usually tolerate due to pain.

Obviously, different organs have different pain sensitivities.  For
example (ironically), the brain has no pain sensing neurons, while the
GI tract

Here's the NIH page on hyperthermia, with more details:
http://cis.nci.nih.gov/fact/7_3.htm

The American Cancer Society hyperthermia page:
http://www.cancer.org/docroot/ETO/content/ETO_1_2x_Hyperthermia.asp

==========
Here are some references for the above:

van der Zee J. Heating the patient: a promising approach?. [Review]
[114 refs] [Journal Article. Review] Annals of Oncology.
13(8):1173-84, 2002 Aug.
UI: 12181239

The free full text is available here:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12181239&query_hl=12
_______

Dick EA. Taylor-Robinson SD. Thomas HC. Gedroyc WM. Ablative therapy
for liver tumours. [Review] [54 refs] [Journal Article. Review.
Review, Tutorial] Gut. 50(5):733-9, 2002 May.
UI: 11950826

The free full text is here:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11950826&query_hl=14
_______

Goldberg SN. Gazelle GS. Mueller PR. Thermal ablation therapy for
focal malignancy: a unified approach to underlying principles,
techniques, and diagnostic imaging guidance.[see comment]. [Review]
[67 refs] [Journal Article. Review. Review, Tutorial] AJR. American
Journal of Roentgenology. 174(2):323-31, 2000 Feb.
UI: 10658699

Free full text is here:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10658699&query_hl=16

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Search terms: 
hyperthermia, organs
hyperthermia "radiation oncology" organs pain
=============

I hope this information was useful.  Please feel free to request any clarification.

Best,

      -welte-ga