Shock

There is between 65-85 mls of blood/kg in an average adult, i.e. 4900 mls in the average 70 kg adult.

Shock is defined as clinical appreciation of the presence of inadequate organ perfusion and tissue oxygenation. No laboratory test diagnoses shock. Haemorrhage is a common cause of shock in surgical patients. Classification of haemorrhage based on percentage of acute blood volume loss, are outlined below.

Volume replacement should be guided by response rather than relying solely on the initial classification. It is dangerous to wait until the trauma patient fits a precise physiologic classification before initiating resuscitation. Fluid resuscitation MUST BE initiated when early signs and symptoms of blood lost are apparent or suspected, not when blood pressure is falling or absent!!

	Class I	Class II	Class III	Class IV
Blood loss (ml)	Up to 750	750-1500	1500-2000	2000
Blood loss (% blood volume)	Up to 15%	15-30%	30-40%	40%
Pulse Rate (beats per minute)	100	100	120	140
Blood Pressure	Normal	Normal	Decreased	Decreased
Pulse Pressure	Normal or $\uparrow$	Decreased	Decreased	Decreased
Respiratory Rate (breaths per minute)	14-20	20-30	30-40	35
Urine Output (ml/hr)	30	20-30	5-15	Negligible
CNS/Mental Status	Slightly anxious	Mildly anxious	Anxious confused	Confused, lethargic
Fluid Replacement (3:1 rule)	Crystalloid	Crystalloid	Crystalloid and blood	Crystalloid and blood

``3-for-1'' rule - this rule derives from the empiric observation that most patients in haemorrhagic shock requires as much as 300 ml of electrolyte solution for each 100 ml of blood loss.