Concentration-dependent effect of hypocalcaemia on in vitro clot strength in patients at risk of bleeding: a retrospective cohort study.

Ionised calcium concentrations had a concentration-dependent association with in vitro clot strength after adjusting for other coagulation abnormalities in patients with coexisting coagulopathy. Maintaining a normal ionised calcium concentration, >1 mmol L(-1) , during critical bleeding is recommended.