Hemorrhagic (Hypovolemic) Shock

Hemorrhagic shock is a condition of reduced tissue perfusion, resulting in the inadequate delivery of oxygen and nutrients that are necessary for cellular function. 

• Whenever cellular oxygen demand outweighs supply, both the cell and the organism are in a state of shock.

Classes Of Shock

Class 1– < 15 % loss blood volume (< 750 mL in a male weighing 70 kg)

• (No change in BP, pulse pressure, respiratory rate or capillary refill)
• Minimal tachycardia < 100 bpm
• Skin pallor possible

Class 2– 15–30 per cent loss blood volume (750–1500 mL)

• (No change in systolic blood pressure)
• ↓Peripheral perfusion with cool, pale, clammy skin
• Capillary refill > 2 seconds
• Tachycardia > 100 bpm
• ↓Pulse pressure as diastolic bp rises
• Increased respiratory rate (tachypnoea) of 20–30 /min
• Subtle mental status changes: anxiety, fear, aggression

Class 3– 30–40 per cent loss blood volume (1500– 2000 mL)

• Marked tachycardia > 120 bpm
• Measurable fall in systolic blood pressure from patient’s normal, e.g. < 100 mmHg
• Thready peripheral pulses
• Flat/empty veins
• Marked tachypnoea > 30/min
• Significant mental status changes: agitated ++
• Dropping urine output

Class 4– > 40 per cent loss blood volume (> 2000 mL)

• Severe tachycardia > 140 bpm
• Moribund, decreased conscious level
• Significant drop in systolic blood pressure, e.g. < 70 mmHg
• Impalpable peripheral pulses, weak central pulses
• Respiratory distress
• Central and peripheral cyanosis
• Minimal urine output

Management

• Control of the airway (with cervical spine control), optimal oxygenation and ventilation are prerequisites to shock management.
• Immediate management of haemorrhagic shock depends on control of the bleeding and administration of intravenous fluids and blood to restore intravascular volume and haematocrit.

1. Control Of Haemorrhage:

• This is achieved by direct pressure on the bleeding wounds with appropriate dressings, and elevation where practicable.
• Wounds can be packed with a dressing, and a circumferential bandage applied around and over the packed wound.
• The bandage can then be twisted in a windlass technique to press the pack down into the wound. 
• Tourniquets have been developed for controlling peripheral limb haemorrhage.

• Once in place and controlling the bleeding, the tourniquet should not be loosened or removed until a surgeon is available to definitively repair the injury.

• Haemostatic dressings are useful for emergency control of arterial and venous haemorrhage from proximal sites where tourniquets cannot be applied, eg. Quikclot, HemCon.
• Clamping of bleeding points can be performed by an experienced surgeon.
• Fracture of the pelvis can result in devastating retroperitoneal haemorrhage

• This can be reduced by compressing the pelvis to approximate the bleeding fracture sites.

2. Peripheral Venous Cannulation:

• Intravenous access must be secured at the earliest opportunity.
• The ATLS guideline for in-hospital trauma cannulation is insertion of two cannulae, minimum size 16-gauge, but preferably 14-gauge, into large peripheral veins, typically in the antecubital fossae.

3. Central Venous Cannulation:

• This is an option reserved for those with appropriate expertise

• it can be very difficult and carries a significant risk of life-threatening complications (pneumothorax and arterial damage most commonly).

4. Intraosseus Cannulation: 

• Intraosseous cannulation has previously been reserved for young children up to the age of about 5 years, where intravenous cannulation is not possible.
• The bone cortex is thin and relatively soft in children, and the marrow plentiful and vascular.
• A specialized 16-gauge intraosseus needle can be pushed or screwed into the bone of the tibia, below and medial to the knee joint.
• Response time to drug administration is close to IV administration, and entire resuscitations can be performed through intraosseus cannulae, including all anaesthetic drugs and fluids.

5. Fluid Administration:

• The traditional ATLS approach for trauma circulation resuscitation, is to site two large-bore IV cannulae and administer an initial bolus of 2 L of warmed Ringer’s lactate or Hartmann’s solution. 

• This is certainly successful in improving perfusion in bleeding patients, but is now not recommended for pre-hospital use where haemorrhage cannot be surgically controlled and blood is not available for transfusion. 

• Casualties bleeding to a level 3 or 4 shock can reach a steady state as the blood pressure drops to a point where active bleeding may cease.

• Restoring vascular volume with crystalloids or colloids can restore the blood pressure to a point where bleeding resumes
• Further administration of clear fluids repeats the cycle until the haemoglobin level drops below a point where adequate oxygen can be carried.
• Cardiac arrest and death then result from anaemic hypoxia.

• In the UK, NICE guidance on Pre-hospital Initiation of Fluid Replacement Therapy in Trauma (National Institute for Clinical Excellence, 2004), relating to traumatized casualties with likely haemorrhage, is to titrate intravenous crystalloid fluids in 250 mL boluses against the radial pulse. 

• If a radial pulse cannot be felt, the fluids are administered until the pulse returns, then withheld. 
• NICE emphasizes the importance of not delaying transfer to hospital, and suggest fluids are administered if necessary en route. 
• In penetrating chest wounds, fluids are titrated against a palpable central pulse. 
• This strategy is known as permissive hypotension. 
• Assuming O Rhesus-negative blood is immediately available in the Emergency Department, the blood pressure can be brought up with crystalloids pending rapid transfusion.
• The dynamic response to a fluid challenge will give information as to whether bleeding is continuous or controlled. 

• A 2 L volume of warmed Hartmann’s is initially given (20 mL/kg in children), and the response in vital signs recorded:

A. Rapid Responders– respond rapidly & remain haemodynamically normal, having lost < 20 % blood volume.

• No further fluid is required and surgical intervention may be required.

B. Transient Responders– respond to the initial bolus, then deteriorate, having lost 20–40 % blood volume.

• These patients will need further fluid administration and blood transfusion, with probable surgical intervention.

C. Non-Responders– show minimal or no response to the initial bolus.

• These patients are likely to require immediate transfusion and surgery to stop exsanguinating haemorrhage.
• There may be other causes such as tension pneumothorax, cardiac tamponade or non-haemorrhagic shock.

• Fluids should be titrated against response, with optimum organ & peripheral tissue perfusion the goal. 

• Blood pressure, pulse rate, peripheral perfusion and CVP are all used to assess response.

• Serial measurement of metabolic acidosis parameters such as bicarbonate, base deficit and lactate levels can be used to gauge adequate response to fluid therapy.
• More sophisticated methods such as Oesophageal Doppler and arterial waveform analysis are also used in the critical care setting.
• Research with 7.5 percent saline and dextran (as opposed to isotonic 0.9 percent) suggests that mean arterial blood pressure and oxygen delivery are improved.
• Capillary damage is lessened, and organ perfusion improved, with a much larger increase in the intravascular volume.
• Short-term survival is improved.
• Blood transfusion should be given early if haemorrhagic shock is demonstrated, with O Rhesus negative, type-specific or cross-matched blood.
• Transfusion should be titrated against the haematocrit, and blood products such as fresh-frozen plasma, platelet concentrates and clotting factors given during massive transfusions on the advice of the haematologists.