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#84052 - 01/27/07 12:08 AM Reaction to blood loss
Tmpx Offline

Registered: 01/15/06
Posts: 26
Dear all,

Today I needed to have some blood drawn for lab work.

Even this small amount seemed to have quite a big impact on my body, making me feel lightheaded and dizzy.

This made me think how debilitating this could be in a survival situation.

Can somebody explain why this happens and if there is something I can do to offset it's effects?

Thanks in advance for your help.



#84053 - 01/27/07 12:25 AM Re: Reaction to blood loss
MOAlan Offline

Registered: 12/31/06
Posts: 14
Loc: central Missouri
I used to have that reaction when I gave blood until a friend that works drawing the blood told me how to counter the effects.
You need to increase the iron in your body and the best way she said was to eat a steak. If you will eat the steak the day before, should help you counter the dizziness and light headedness.
When you go to give a pint of blood, they always check your iron level before you are allowed to give for those exact reasons.

#84054 - 01/27/07 12:45 AM Re: Reaction to blood loss
Arney Offline

Registered: 09/15/05
Posts: 2485
Loc: California
Normally, only a small quanitity of blood is collected for tests, so my guess is that you weren't actually feeling the effects of blood loss (well, unless they actually did collect many tubes of blood). Many people also have a mental reaction to needles which manifests as physical symptoms. I normally don't mind needles, but one time, I was watching TV and a woman was having collagen injected into her lips. The camera did a close-up on the needle being stuck into this woman's lips over and over again and to my surprise, I soon ended up feeling weak and a bit nauseous. I was just watching the the needle on TV! Many people are similarly affected by the sight of blood or dead bodies and so forth. Even the brief pain of the needle being inserted can trigger certain physiologic reactions.

You are probably feeling dizzy due to low blood pressure. Whatever is actually causing the reaction, your blood vessels are relaxing, increasing the space available for blood in your ciruclatory system, and reducing the overall pressure. The classic method to deal with this lower pressure is to sit with your head down between your knees so your brain is at or below the level of the heart. Another method shown effective in clinical studies is to cross your ankles, then squeeze them, tightening the muscles in your legs and abdomen to increase the blood pressure to your brain. The flight suits of fighter pilots pulling high G maneuvers have air bladders that inflate and constrict their bodies to try and keep the blood from rushing to their legs and causing the pilots to pass out. Same principle.

I am not a doctor, so if you have concerns about this, please consult with a medical professional.

#84055 - 01/27/07 12:49 AM Re: Reaction to blood loss
Lasd02 Offline

Registered: 12/14/05
Posts: 130
Loc: Pasadena, Calif.
I'm not a medical professional, but my understanding is that we can lose up to 15% of our blood volume without noticable changes in vital signs. It sounds to me like the lightheadedness you felt was more a psychological as opposed to a physiological effect. The best advice I have for someone who is planning on donating blood or giving a sample or two, is to drink lot's of water at least 2 hours prior and stay away from coffee.

#84056 - 01/27/07 01:12 AM Re: Reaction to blood loss
haertig Offline

Registered: 03/13/05
Posts: 1960
Loc: Colorado
Even this small amount seemed to have quite a big impact on my body, making me feel lightheaded and dizzy.
That is called a vasovagal response. It wasn't due to blood loss.

When your vagus nerve gets stimulated, quite often due to some kind of emotional reaction, your blood vessels dilate and your blood pressure drops. "fainting" falls into this category. If you were to check your vital signs during one of these episodes, you'd find your blood pressure would be down, and so would your pulse rate. Blood loss ("hypovolemia") on the other hand, results first in a rapid pulse, then a drop in blood pressure when the elevated pulse rate is no longer able to compensate for the blood loss.

I used to be a paramedic and dealt with this often. And yes, even having been a paramedic for many many years, the sight of my OWN blood in significant quantities makes me vagal out sometimes. "Vagal out" sounds more manly than "feel faint"! <img src="/images/graemlins/blush.gif" alt="" /> If you're sitting when this happens, it's usually easy to make yourself feel much better by bending over and putting your head between your legs. Not TOO far between your legs mind you, lest you generate the wrong impression for bystanders! <img src="/images/graemlins/tongue.gif" alt="" />

#84057 - 01/27/07 01:15 AM Re: Reaction to blood loss
Frankie Offline
Old Hand

Registered: 09/19/03
Posts: 734
Loc: Montréal, Québec, Canada
I participated in some clinical trials (only currently marketed drugs) and they have to watch how long the drug stays in the organism before being eliminated so they take a blood draw every 2 min, than every 30 min, etc. Sometimes they took more than what the donners give to the Red Cross when collecting blood. I never had problems, just sometimes headaches and feeling tired. But there was always one or two participant that felt dizzy and had to rest on a medical chair but it's only due to anxiety.


#84058 - 01/27/07 02:01 AM Re: Reaction to blood loss
gunsmith Offline

Registered: 03/16/06
Posts: 35
Loc: Co.'Douglas 80125
I used to have a "cast iron stomach" as to my own blod loss - an in - well danm, guess I'm going to have to fix this-kinda thing (aka sew, glue, wrap)

But the last time I delt myself a good gash, I felt kind of sick, I mean, I got it done like usual - but it was like....Different in the "gut" feeling,(if this question had been asked 40- 50 years ago, I would have described it as a 'queer"feeling),, I did'nt like it at all, and I usually don't give much of a damn about my blood. Anyway, splashed somo water in my face & got er done...

I've patched myself (and others) up often enough over the years to include super-glue in all my kits, and have delt with several "borderline" serious injuries. All with good outcomes, but I understand when plain ole blood goes "creepey".
Never been lost, But I've been "Powerfull confused"

#84059 - 01/27/07 02:15 AM Re: Reaction to blood loss
OldBaldGuy Offline

Registered: 09/30/01
Posts: 5695
Loc: Former AFB in CA, recouping fr...
Simply put, in the amount you are talking about, it is all in your head. I donate blood all the time, never feel anything but ready to get out of there and on with my day. I have watched minor surgery on my own body (under a local) with no ill effects. My ex, on the other hand, would almost faint at the sight of blood, anyones blood. Don't know why some people are different, they just are. Don't know if there is any way to change it either...

#84060 - 01/27/07 04:23 AM Re: Reaction to blood loss
Susan Offline

Registered: 01/21/04
Posts: 5163
Loc: W. WA
OBG is right, it's all in your head. If it makes you feel better, take Geritol (iron for anemia) for a few days before you donate blood for any reason.

I had some serious blood loss (we won't go into details) a few years ago. Here's how it goes:

Psychologically, you may feel funny right away. This is just the fear factor. Settle down & apply pressure with a lump of bandage or a fingertip if it's small, or the heel of your hand if it's larger. If it requires the heel of your hand, you need medical assistance. Call 911 or have someone take you. You can't drive and hold pressure at the same time, so don't try to do it yourself unless there are simply no other options. Asking a stranger for help is an option.

If the bleeding is due to trauma, you may be feeling the beginnings of shock. Deal with the most life-threatening of the injuries first. You can bleed out from a large arterial tear in 1.5 to 2 minutes. You'll be unconscious very quickly, so move fast or give instructions to someone nearby, preferably not an idiot.

If you can't stop mild but continuous bleeding due to lack of access (internal, etc), and you can't get to medical attention right away, try to drink a cup of water every hour to keep your blood pressure stable. (This is from my doctor.)

As you continue to lose blood, you really start feeling sick. You will feel weak and probably start to vomit because you're going into shock. You'll be shivering. You aren't focusing on anything else except how awful you feel. If you are lying down and then you sit up, you will probably vomit and possibly pass out. Raising the victim's legs will help keep what blood is still in the body in the important areas, the chest, heart and brain.

If you need to apply a pressure bandage, see the instructions below. A pressure bandage is either held in place with your hand or a wrap-around bandage with a lump over the bleeding. The lump can be a stack of gauze squares, a handkerchief or a torn piece of clothing folded several times, etc. It doesn't have to be sterile, so use what you've got.

Please pay attention to the parts below where they mention peeking (don't), removing the bandage to apply a fresh bandage (don't), signs of flow restriction to the arm, leg or brain, and the inadvisibility of using tourniquets.



A 150-lb person has about 5.25 quarts of blood in them. Most people can donate a pint (10%) with no ill effects.

If they lose 15-30% of their blood (3 cups to 1.5 quarts), they will probably look pale and have a rapid heartbeat, their skin will feel cool, and they may act odd. They should have IV fluids, but usually don't need a transfusion. Their own body can replace it in a week.

If they lose 30-40% (1.5 to 2 quarts), their blood pressure drops, the heart rate increases & their mental status gets worse. They will need both IV fluids and a blood transfusion.

If they lose more than 40% of their blood, they will need a lot of help to avoid death.

BTW, transfusions are a temporary loam of red blood cells to carry oxygen. Your body can replace them after a while, but until you do, you will find that climbing a few steps will make you sweat and pant! <img src="/images/graemlins/shocked.gif" alt="" /> So, don't make any plans for any immediate vigorous exercise.

Sue ("Liver? You want me to eat LIVER? YUCK!!!")

#84062 - 01/27/07 07:15 AM Re: Reaction to blood loss
TomP Offline

Registered: 01/16/07
Posts: 56
The autonomic nervous system is a funny thing. Most people can lose a significant amount of blood without many symptoms. In Vascular Surgery we have a saying- "It's not really bleeding unless you can hear it" Trust me- if it's really bleeding you really can hear it!

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