This is inadequate perfusion of tissues and is classifed as:
1) Grade I
0-15% bood loss which is similar to donating blood. Patient is usually anxious but no other signs of blood loss. Manage with crystalloid.
2) Grade II
750-1500ml or 15-30% blood loss. Signs are tachycardia, tachypnoea and narrow pulse pressure. Manage with colloid.
3) Grade III
1500-2000ml or 30-40% blood loss. Signs are as with grade II and drop in systolic , urine output as well as reduced cerebral perfusion. Manage with colloids and blood.
4) Grade IV
>2000ml blood loss with signs as above and negligible urine out put. Manage with colloids and blood.
It is important to identify signs of shock early and realise that although classification is helpful, it should not delay treatment. Ideally Arterial and central lines should be placed in patients with grade 3-4 shock and blood is requested early. The priority is fluid resus and haemorrhage control. Patients who are then stabilised may be safe to CT to assess cause of haemorrhage however those who are unstable may need to be taken to theatre.