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> "The drugs that render patients unconscious also make them hypothermic. That’s useful because chilled patients bleed less during surgery ..." Coagulation is

> "The drugs that render patients unconscious also make them hypothermic. That’s useful because chilled patients bleed less during surgery ..." Coagulation is an enzymatic reaction. You might not be surprised, then, to learn that low temperatures retard, not enhance, coagulation. Cold temperatures make the patient bleed more, not less. The article gets this part exactly wrong.

pavedwalden 15y ago
Is it possible that this is counterbalanced by the circulatory system's reaction to cold? For instance, perhaps surgery on the limbs is easier when the body is reducing peripheral circulation as it does in someone experiencing hypothermia.
- bluedanieru 15y ago
  That's exactly what they're talking about. If the reason they bled less was that their blood was coagulating all over the place, they would also bleed less because they would be dead.
- carbocation 15y ago
  Empirically, my understanding is that no, the harm of cold temperatures (decreased coagulation) is not counterbalanced by the gain (decreased peripheral circulation). Patients undergoing surgery are coagulopathic, moreso when they are cooled, and in fact they are often actively warmed now.
billswift 15y ago
Cold causes blood vessels to constrict, restricting blood flow. It is a totally different response from coagulation.
- carbocation 15y ago
  And yet coagulation is the relevant thing to discuss when we talk about blood loss from surgery, which is all I am trying to address because I am uncomfortable with the fact that the journalist got his facts exactly wrong. Being cold during surgery makes you bleed more. You and others have noted that cold causes constriction of blood vessels, so if that were the driving fact during surgery, cold would be beneficial. In fact, it is not. The decreased effectiveness of the clotting cascade outweighs the decrease in peripheral blood flow, leading to increased blood loss due to cold. The journalist stated something as fact, and then tried to explain why it was so. But he started from a false fact.

pavedwalden 15y ago

Is it possible that this is counterbalanced by the circulatory system's reaction to cold? For instance, perhaps surgery on the limbs is easier when the body is reducing peripheral circulation as it does in someone experiencing hypothermia.

bluedanieru 15y ago
That's exactly what they're talking about. If the reason they bled less was that their blood was coagulating all over the place, they would also bleed less because they would be dead.
carbocation 15y ago
Empirically, my understanding is that no, the harm of cold temperatures (decreased coagulation) is not counterbalanced by the gain (decreased peripheral circulation). Patients undergoing surgery are coagulopathic, moreso when they are cooled, and in fact they are often actively warmed now.

billswift 15y ago

Cold causes blood vessels to constrict, restricting blood flow. It is a totally different response from coagulation.

carbocation 15y ago
And yet coagulation is the relevant thing to discuss when we talk about blood loss from surgery, which is all I am trying to address because I am uncomfortable with the fact that the journalist got his facts exactly wrong. Being cold during surgery makes you bleed more. You and others have noted that cold causes constriction of blood vessels, so if that were the driving fact during surgery, cold would be beneficial. In fact, it is not. The decreased effectiveness of the clotting cascade outweighs the decrease in peripheral blood flow, leading to increased blood loss due to cold. The journalist stated something as fact, and then tried to explain why it was so. But he started from a false fact.