Severe bleeding in critical care M. GIRARDIS, S. BUSANI, M. MARIETTA Severe bleeding and haemorrhagic shock are frequent and challenging conditions in anaesthesiologic and intensive-care clinical practice. Major haemorrhage may occur in trauma patients, during and after surgery, and in other variety of critical pathologies, such as oesophageal bleeding in cirrhotic patients and intracranial haemorrhage. Uncontrolled haemorrhage is the most common cause of death in trauma patients and accounts for at least 60% of deaths in patients after hospital admission [1]. Mortality after an episode of intracerebral haemorrhage is very high (20–40%), and 80% of the survivors suffer severe neurological impairment [2]. Perioperative bleeding depends on the extent and complexity of surgical proce- dures and on the coagulation status of the patient. However, unexpected and massive bleeding may complicate any surgical procedure, leading to a significant increase in perioperative mortality from < 1% up to 20% [3]. Despite the significant improvement in surgical technique, major surgery for liver diseases, such as partial hepatectomy and orthotopic liver transplantation (OLT), is still associated with significant blood losses due to both technical factors and poor haemostasis of cirrhotic patients. The degree of blood losses during OLT has important effects on postoperative infection, graft survival, intensive-care stay, and mortality [4]. Ex- cessive bleeding is a crucial problem also in cardiac surgery: massive blood loss is associated with an eight-fold increase in the odds of death [5], and up to 5% of patients need a second operation to control severe post-operative bleeding [6]. The most common cause of intraoperative and postoperative bleeding is ina- dequate surgical haemostasis, and more than 70% of episodes are due to technique problems. Moreover, surgical technique per se affects the rate of postoperative bleeding [7, 8]. Nevertheless, surgery exposes patient to haemostatic stress, testing, in extreme conditions, the limits of the haemostatic system in maintaining a delicate balance between bleeding and clotting (thrombosis). Therefore, in patients with inherited or acquired defects in coagulation processes (e.g. haemophilia, liver dysfunction, anticoagulant therapy), severe bleeding can occur also following minimal procedure with faultless surgical technique. Whatever the cause, massive bleeding and its therapeutic correction lead to an unavoidable secondary coagulo- pathy caused by consumption and dilution of clotting factors, acidosis, and hypo- thermia [3]. Of these risk factors, hypothermia is without doubt the most important as it causes a depression in platelet activity, hinders the reactions of clotting enzymes, and impairs the fibrinolytic balance. At temperatures lower than 34°C, the dysfunction of haemostasis is equivalent to that observed in haemophilia B patients Chapter 62