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CDHB

Shock

Definition - inadequate delivery and utilization of oxygen by vital organs due to a problem with the circulation.

• The inadequacy may originate in the pump, the outflow from the pump, the location the blood travels to, the volume of blood, or a combination.
• Assessment of the degree of shock can be difficult, as signs and symptoms will vary with the cause, the speed of onset, the patient's pre-morbid state, and the treatment so far.
• Generally speaking, if the patient displays signs of shock, then the shock has reached a severity beyond the patient's ability to compensate and demands aggressive treatment.
• If not already instituted, apply oxygen and establish secure IV access with large bore IV cannulae. Trendelenberg position. Patient should be managed in an area capable of monitoring and with resuscitation capability. A urinary catheter should be inserted and urine output monitored.
• Invasive monitoring of the circulation (CVP or Swan Ganz catheter) provides useful objective information but requires expertise in application and interpretation. The change in CVP in response to fluid challenges is more useful than the exact numbers.

Cardiogenic Shock

• Arrhythmias, myocardial dysfunction, acute valvular dysfunction, ventricular or septal rupture, etc.
• Fluid therapy may occasionally be useful to increase filling pressure but more often specific therapy is necessary e.g., anti-arrhythmic agents, DC shock, inotropic agents etc.

Obstructive Shock

• Tension pneumothorax (obstructs venous return), pericardial tamponade or constriction, obstructive valvular disease (aortic or mitral), pulmonary hypertension, massive pulmonary emboli, cardiac tumours, etc.
• ED ultrasound may be used to determine whether there is right heart strain or pericardial effusion.
• JVP/CVP may be raised but this does not represent fluid overload in this context.
• Initial fluid therapy is commonly used but specific treatment is required.

Distributive Shock

• Septic shock, anaphylactic shock, neurogenic shock, vasodilator drugs, etc.
• Skin is warm and pink.
• Relative hypovolaemia due to expanded vascular space.
• Fluid resuscitation and specific treatment is required.

Hypovolaemic Shock

• Blood loss, third spacing etc.
• Urgent surgical consult is necessary should haemorrhagic shock be suspected.
• Ultrasound of the IVC may be a quick way of assessing volume status in the Emergency Department or ICU - this needs a practitioner trained in this technique.
• CVP may also be useful (see above). Pulmonary capillary wedge pressure measurements provide the ultimate measure of volume status but are only practicable in ICU, CCU, or theatre.
• The urine output is a useful objective measure of renal perfusion assuming no diuretics have been given.
• Haemorrhagic shock with hypotension suggests 1500-2000 mL of blood loss and demands rapid infusion of 2000 mL of crystalloid (see table below).

  Note: There is a trend in penetrating trauma (provided there is no neurotrauma) to limit fluid resuscitation until surgical arrest of the bleeding can be achieved - especially in young healthy adults. Overtly aggressive resuscitation may cause haemodilution of coagulation factors and hypertension which disturbs fragile clots. Aim for a systolic blood pressure >90 and treat hypertension with analgesia if needed. Discuss early with a Surgeon as to whether surgical correction of blood loss is indicated.

• For Class III or Class IV shock (see table below), transfusion of blood will invariably be required.
• If fluids do not restore satisfactory circulation, then blood transfusion is urgent and should occur prior to cross-match using Type O negative blood (available from the Blood Bank, Lower Ground Floor, Christchurch Hospital). See Collection of Blood from Blood Bank. Type specific blood may be available from the blood bank prior to full cross-match.
• Consider the Massive Transfusion Protocol (available on the CDHB website) if there is massive bleeding with either shock or abnormal coagulopathy. In general if there is not an adequate response to 3 units of blood then the protocol should be activated.
• Don't forget localized control (pressure on external bleeding, surgery for internal bleeding).

Note: The elderly and those on drugs such as beta-blockers are less able to compensate and therefore will become hypotensive earlier.

Note: There is a greater blood volume in advanced pregnancy and an ability to shunt blood from the placental circulation (at the fetus' expense); therefore shock manifests later in the mother (but earlier in the fetus).

Classification of Haemorrhagic Shock

Topic Code: 2238