GURPS Blood

[Varyon]

EDIT: This system has been modified, simplified, and divorced from HP. See here.

As was brought up in the "GURPS deadliness" thread, GURPS apparently lacks any sort of rules for blood transfusions. For this discussion, I'm focusing on the situation of a character suffering from massive bleeding that requires Surgery to fix (say, from a hit to the Vitals), although discussion of other situations are welcome.
A summary of this post, and its application to the above situation, is in post #2. If you'd like to skip the justifications and musings, feel free to jump down a step.

In that thread, I suggested the idea of a single unit (~pint) of blood being good to negate up to 6 HP of blood loss. Note this implies an HT 10 person with a 4 HP injury is going to be pouring out about a pint every 12 minutes, which may be a bit much. Doing some further research, I noticed that somewhere around 50% blood loss is considered to be the maximum one can get to before death (actually, what I found noted that at above 40% loss you're toast without immediate assistance; I decided to go with 50% being absolute death to make things easier). I've also found that humans typically regenerate about a unit of blood per month (blood banks appear to require between 2 and 3 months between donations to be safe).

Altogether, what does this mean? Well, that 6 HP figure I came to by assuming a human would reach -5xHP once they lost all their blood (although I rounded average amount of blood down from ~11 to 10). If we assume 50% blood loss is instead -5xHP, that implies a unit of blood is worth around 12 HP. Interestingly, using GURPS natural recovery rules, an HT 10 person would regenerate around 15 HP in a month, which is quite close to this figure.

Of course, this introduces a potential problem - if we go straight with a blood-to-HP value, giving a unit of blood will drop an average person to negative HP, easily causing unconsciousness and greatly weakening them for quite some time thereafter. As a workaround, I'd say that giving blood causes a form of "virtual" damage, at least up to a unit (after this, it causes real damage). For every full 5 HP of this, you take a -1 to HT checks to resist bleeding, avoid FP loss, regain FP, and whatever else the GM deems is appropriate (resisting knockdown/stunning may be more difficult, for example, as may some Self-Control rolls). Such damage regenerates at the same rate as (optionally, concurrently with) HP.

This could even be expanded out to function as something like FP - a character could have "Blood Points" or similar. For every 1/3 of BP a character loses, he suffers a -1 penalty to "blood-related" HT checks (as noted above). BP can go negative but, like FP, every point of negative BP inflicts 1 HP of injury (optionally, this damage is only restored by regenerating BP). BP is an abstract quantity - for any given character, a "unit" (1/10th total volume) of blood is equal to their maximum BP, which is itself equal to 1.5xHP - more resilient characters/creatures don't necessarily have more blood, even if they have more HP. Blood Mages and the like would be able to fuel spells/powers with BP; I leave it to GM's to work out fair values here (similarly, a character could have particularly strong or weak blood, getting more or less BP than his HP implies).

All told, the above works out to a typical human having 15 BP. He can lose up to 15 BP - one unit - of blood before suffering anything serious, although at lesser values he has a bit less endurance. After that point, he begins to suffer real damage from loss of blood, losing some faculty at 3 HP (15% blood loss, Class II hemorrhage), risking death at -10 HP (23% blood loss, far more severe Class II), -20 HP (30% blood loss, Class III hemorrhage), -30 HP (37%, Class III), and -40 HP (43%, Class IV hemorrhage), and finally dying automatically at -50 HP (50% blood loss, Class IV).

[Varyon]

To summarize the first post:

We introduce a new secondary characteristic, Blood Points (BP), which is equal to 1.5xHP (round down). Any damage from bleeding is subtracted from BP rather than HP (an exception is that critical failure represents both massive blood loss and resulting tissue damage - the character suffers 3 BP and 1 HP of damage). For every full third of BP a character has taken in damage (every 5 points for an HP 10 character) imposes a -1 penalty to bleeding checks, attempts to resist FP loss, attempts to restore lost FP, and anything else the GM deems appropriate. Once a character has been reduced to 0 BP, further loss also causes equivalent HP damage. Optionally, HP lost due to blood loss cannot be restored until BP is above 0.

For natural recovery, roll against HT every day. Success typically restores 1 BP, although characters with very high BP may restore more (follow the same guidelines as for HP, except restoring 1/15th BP rather than 1/10th HP). Things like total bed rest and an appropriate diet may give bonuses to this recovery roll, at the GM's option. BP recovery occurs concurrently with HP recovery; roll for each seperately. It is up to the GM if things like Fast Healing, Regeneration, etc apply to BP.

For purposes of transfusions and the like, a single "unit" of blood represents 1/10th of a character's total blood volume, and is also equal to their full allotment of BP. However, 1 BP doesn't necessarily have a true volume associated with it - rather, a unit from any human (provided blood types match) is worth a full allotment of BP for the one being infused (so 12 BP - one unit - of blood from an HP 8 human is equivalent to 24 BP - one unit - of blood for an HP 16 human).

Giving a blood transfusion requires an appropriate skill roll (likely Physician, although a penalized First Aid should work in a pinch). Success allows the physician to restore up to 1d BP per minute (adjust this for characters with high/low BP - 1dx2 for one with 30 BP, for example). Critical success maximizes this roll (to 6), failure minimizes it (to 1), and critical failure typically results in the physician ruining the supply (for example, ripping the bag such that all the blood spills out) or mismatching the blood type (causing toxic damage to the patient). As above, each unit (~1 pint for humans) of blood restores up to the character's BP allotment (so if a character with 15 max BP is currently at -20, a unit will get them up to -5). Restoring BP when it's in the negative can restore some HP - allow the character to roll against HT for every BP (or some multiple thereof) restored - success restores an equal amount of HP. If a bleeding character is hooked up to a constant blood drip that can match his rate of BP loss, he simply ceases to take HP damage (no roll required).

Using plasma instead of blood is easier (less need for refridgeration) and safer (no risk of mismatched blood types) but less effective. Plasma functions in all ways like blood with the exception of restoring/preventing loss of HP. For that purpose only, it is about 2/3 as effective as blood - every third BP restored (while negative) gets no HT roll to restore HP, and a bleeding character hooked up to a constant plasma drip still takes 1 HP of damage for every 3 BP "lost."


So, to open the floodgates - questions? Comments? Concerns?

[Gigermann]

Biotech p. 130, "Blood Transfusion"

[Ulzgoroth]

Originally Posted by Gigermann

Biotech p. 130, "Blood Transfusion"

Yeah, it's inaccurate to say that GURPS has no rules for blood transfusion (and for the record, I didn't say it didn't).

However, if you look at what's actually written there, there is no effect given for replacing lost blood. In fact, IIRC there's no effect given for performing surgery without the 'mandatory' transfusion blood. There's an effect given for blood doping (on the next page) and I think there is something around for blood type mismatch.

EDIT: Actually I should qualify a little further: I think it's indicated that transfusion supplies are part of the higher-end First Aid equipment sets, but no special rules are provided.

[Gigermann]

Originally Posted by Ulzgoroth

there is no effect given for replacing lost blood.

Also from Biotech p.130

If blood is in short supply, assume each lost HP treated by surgery requires from half a pint to one pint of blood.

Otherwise, I'm presuming replacement of blood lost is just a 1:1 tradeoff—good enough for my purposes anyway.

[Ulzgoroth]

Originally Posted by Gigermann

Also from Biotech p.130

As I said: no effect given. If you don't have the blood, what happens? There's nothing in the text. (And we know surgery without transfusion is possible, because surgery predates blood transfusion.)

Though by 'replacing lost blood' I was referring to loss of blood to bleeding injuries rather than to surgery.

[Ulzgoroth]

Originally Posted by Gigermann

Otherwise, I'm presuming replacement of blood lost is just a 1:1 tradeoff—good enough for my purposes anyway.

A 1:1 tradeoff? What does that mean? In real terms or game terms?

[Gigermann]

Originally Posted by Ulzgoroth

As I said: no effect given. If you don't have the blood, what happens? There's nothing in the text. (And we know surgery without transfusion is possible, because surgery predates blood transfusion.)

Though by 'replacing lost blood' I was referring to loss of blood to bleeding injuries rather than to surgery.

I see what you mean, now. I suppose one could just extrapolate from the Bleeding rules in Basic—replacing HP for HP prevents further injury, with the 1HP/pint for surgery as a guideline (I'm presuming HP lost from Bleeding can be healed by transfusion at 1:1); if bleeding isn't stopped, the 1HP/min (or whatever) continues, including during surgery.

Just guessing, though.

[Anthony]

Realistically, blood loss should probably reduce your FP as well as your HP, but I wouldn't include a separate 'blood' category for damage -- most damage will result in some blood issues as a side effect.

[Gigermann]

Also for (indirect) reference, Low Tech Companion 1 p. 25:

In addition, apply the optional bleeding rules (p. B420) after any amputation or any surgical procedure that inflicts substantial injury. After very minor surgery, such as circumcision, a failed Surgery roll causes bleeding.