I was recently asked why TXA should not be used in subarachnoid hemorrhage. A recent cochrane review (one of the most respected sources of review articles) discussed a search of 10 trials invovling 1904 patients. A SAH commonly occurs as a result of an aneurysm or weak spot in the brain rupturing and leaking blood into the space immediately around the brain. Two common consequences of this are devastating rebleeding (about 30% will die!) and hydrocephalus (clotted blood blocks the openings that allow the CSF to drain out of the brain and around the spinal cord - it occurs in as much as 20-30% for all SAH cases).
Treatment with TXA ranged from < 72 hours to 6 weeks.
It was theorized that TXA would decrease the rebleed rate by preventing breakdown of the clot in the damaged vessel. In fact it did reduce rebleeding rates by 35%. However, TXA also increased the rate of cerebral ischemia and completely offset any benefit of preventing rebleeding. It is likely that the reason for worsening ischemi is prevention of recanalization of blocked blood vessels and the restoration of blood flow to surviving brain tissue.
There was no effect on rates of hydrocephalus.
Bottom line: This has little impact on TXA use for bleeding in trauma in a tactical environment- but if you should be asked, now you know why TXA is contraindicated in SAH.
M. Baharoglu, M Germans, G Rinkel, A Algra, M Vermeulen, J van Gijn, Y Roos, "Antifibrinolytic therapy for aneurysmal suabarachnoid haemorrhage." Cochrane Database Systematic Review, 30 Aug 2013.
T Eastin, C Snipes, R Seupaul, "Are antifibrinolytic agents effective in the treatment of aneurysmal subarachnoid hemorrhage?". Annals of Emergency Medicine V 64: 6, pp 658-659. 01 Dec 2014.