Shock Series- part 4 of 6 hypovolaemia

Part 4 of 6 - Hypovolaemic Shock

Hypovolaemic Shock part 4 of a 6 part shock series

Recapping: Shock is a syndrome characterised by poor cellular perfusion. It can be preceded by

• blood volume loss (Hypovolaemia),
• obstruction of blood flow into the heart (obstructive),
• failure to pump (cardiogenic), or
• available blood being maldistributed (distributive).

This trauma pearl edition looks at blood loss as a cause of shock.
Haemorrhagic or Hypovolaemic shock is poor tissue perfusion due to a decrease in circulating blood volume. It is the most common type of shock in trauma patients.
Recapping our physiology, blood is s suspension of particles, cells, electrolytes, proteins and water. An average adult has about 60-65 ml/kg... Approximately 5.5 litres.
Hypovolaemia literally means low volume of blood and is classified into four stages according to the percentage of blood loss. A nice easy way to remember the stages is by recalling the game of tennis.
Stage 1 = 0-15% volume loss Stage 2 = 15-30% (750-1500ml) Stage 3 = 30-40% Stage 4 = more than 40% ( >2L)
With out stopping bleeding I guess it's "game, set, match!!"
Most hypovolaemia is caused through bleeding, but other causes can be dehydration, diarrhoea and severe burns where plasma leakage can be acutely life threatening.
Treatment for this shock focuses mostly on stopping bleeding. Door to theatre times in major trauma centres have improved, as have our accessory treatments. The old surgical adage that the only effective way to stop bleeding was "bright lights and sharp steel" still rings true, however a lot can be said for direct pressure, and elevation. Judicial use of tourniquet devices remain a valid option if there is delay to life saving surgery.
Therapy with clot activating mesh has proved successful, with products like Quickclot, Oxicel etc.
Drug therapy with Tranexamic Acid, and VitK, fresh frozen plasma (FFP) infusions, and platelet infusions has improved outcomes.
Fluid resuscitation IV or IOss has featured as a primary survey intervention for decades, however this is being challenged by the newest school of thought; is that of permissible hypotension. We have dedicated a trauma pearl to this topic; see below.
The gold standard management is to insert 2 x large bore IV cannulas, and attach the patient to a crystalloid (normal saline or Hartmann's (lactated Ringers).
Where 5-10 years ago it was commonplace to rapidly infuse 1-2litres; today the standard fluid bolus is 100-200 aliquots of saline to titrate systolic BP of 80-90 mmHg.
Fear of haemodilution, acidosis, coagulopathy, inadvertent cooling of the patient, and disruption of a haemostatic clot is rationale enough to be judicious with fluid resuscitation. In head trauma patients with potentially raised ICP, maintaining a SBP up to 100 mmHg is standard management.
Maintaining a balance of colloids, crystalloids and Blood products is an ongoing area of research, and whilst experts can't agree on any one protocol, a ratio of 3:1 crystalloid to colloid, appears to be most common. A blood product replacement regime using a ratio of 1:1:1 or for every bag of packed RBC, give a bag of FFP, and a bag of Platelets, yields favourable outcomes, but nigh impossible in remote and some rural areas.
Burns patients loose massive volumes of plasma. Special fluid resuscitation regimes include large volume replacment.
The Parkland formula is the most commonly used regimen.
Parkland is:

• 3-4ml X. Kg X. % of burn.
• Half of the volume given in the first 8 hours post burn ( back dated to the time of the injury)
• Remainder of volume over the following 16 hours.
• Eg: a 75kg man is 50% burnt at 10am.
• 4ml x 75= 300ml
• 300ml x 50 = 15000ml
• So by 6pm tonight he will require 7500ml.

Summary: Hypovolaemic shock is the most common of the shock syndromes in trauma, the principles of treatment are simple: stop bleeding, replace loss. However there is no one protocol to achieve this goal, and treatment is tailored to the individual on a case by case basis.