Emergency medicine - The management of shock in primary care

The management of shock varies. This article considers hypovolaemic, cardiogenic and septic shock.

Hypovolaemic shock
Regardless of the cause, the key intervention in the management of hypovolaemia secondary to blood loss is to stop the bleeding. This is rarely possible in the out-of-hospital setting as significant external haemorrhage in this context is rare.

Internal haemorrhage, whether it arises as a result of a traumatic injury or from a medical condition, such as a leaking aortic aneurysm, commonly requires the intervention of a surgeon to arrest bleeding.

The two most effective interventions are therefore a short insult to surgery time, best facilitated by rapid transfer in an ambulance, and pre-alerting the receiving hospital.

Moving the patient should only be delayed to ensure the airway is patent and protected, oxygen is administered and any life-threatening breathing problems are corrected.

On the rare occasions in which significant external bleeding is present, it should be managed with direct pressure to the wound, laying the patient flat, elevating the injured limb and applying a second pressure dressing over the first.

If necessary, the bandage can be tightened using a windlass - a pen inserted under a layer of the bandage, which is then twisted and tied off.

Ribbon gauze impregnated with haemostatic agents has recently become available and is highly effective in promoting clotting when used to pack wounds when bleeding cannot otherwise be controlled.

If no other interventions are successful, a tourniquet should be applied close to but proximal to a limb wound. Ideally it should be broad and should be tightened until the bleeding stops, and never be loosened outside of an operating theatre. An adequately tightened tourniquet will be painful, requiring IV analgesia.

Oxytocic agents can be used to control significant primary post partum haemorrhage and severe bleeding subsequent to an incomplete miscarriage.

Hartmann’s solution should only be used if the radial pulse is absent

Fluid therapy
Transporting the hypovolaemic patient to hospital must not be delayed to obtain IV access: the evidence to support administering salt water, which has neither clotting nor oxygen carrying properties, is limited.

Paramedics will normally attempt to gain IV access en route to hospital, and are increasingly using the intra- osseous route when cannulation is impossible.

'Permissive hypotension' is the current recommended approach to fluid replacement in non-compressible haemorrhage, with 250ml aliquots of normal saline or Hartmann's solution being administered only if the radial pulse is absent.

The aim is to avoid raising the BP to a level which will dislodge fragile clots. In the presence of a penetrating injury to the trunk, which has a greater risk of damage to a large blood vessel, fluids should be administered even more cautiously and withheld unless the carotid pulse is absent.

There are two key exceptions to using the absence of pulses to direct fluid therapy. In multi-system trauma, which includes a significant head injury (defined as any episode of unconsciousness), fluids should be given with the aim of maintaining a mean arterial pressure of 80-90mmHg to ensure an adequate cerebral perfusion pressure.

In pregnancy, most of the physiological mechanisms which would be activated to compensate for blood loss are already in play. The only effective mechanism available to maintain maternal BP is to divert the circulation away from the placental bed, sacrificing the fetus.

Consequently, practitioners should have a lower threshold for giving fluids and aim for a target systolic BP of 100mmHg. This can be exceeded if the patient has an altered mental status, significant arrhythmias, or blood loss exceeding 500ml.

Cardiogenic shock
Cardiogenic shock may occur subsequent to heart failure following an acute MI, following rupture of a septal infarction, or due to an arrhythmia.

Patients with evidence of hypoxia should be given high concentration oxygen and will usually be more comfortable sitting up.

Brady arrhythmias resulting in hypotension should be managed with IV atropine 500 micrograms, repeated to effect at three-minute intervals to a maximum of 3mg.

The preferred treatment of tachycardia with shock is cardioversion and this will commonly be delayed until arrival at hospital.

IV fluids should be avoided in cardiogenic shock with the exception of acute right ventricular infarction, when a fluid challenge of 200ml saline is sometimes helpful.

Both nitrates (glyceryl trinitrate spray) and continuous positive airway pressure ventilation are recommended in acute cardiogenic pulmonary oedema.

However, the former will result in further falls in BP and should be given judiciously, and the latter is not commonly available outside hospitals.

Septic shock
Hypotension in septic shock results from leakage of circulating volume into the interstitial space through a leaky capillary bed.

Although septicaemia will occur following the systemic spread of any infection, meningococcal septicaemia is arguably the greatest concern in pre-hospital care.

Any patient with recent onset of flu-like symptoms and pyrexia should trigger suspicion if these are associated with a rapid deterioration and any combination of headache, altered mental status or conscious level, photophobia, stiff neck, convulsions or cardiovascular compromise.

The presence of a non-blanching petechial rash is pathognomonic of meningococcal septicaemia, but a rash that blanches does not rule out this diagnosis. Treatment consists of high concentration oxygen and early IV (preferred) or IM administration of ceftriaxone (or benzylpenicillin if unavailable): this should not be delayed until hospital admission.

IV fluids should be given to correct shock - en route to hospital if intravascular access has not been obtained before the arrival of an ambulance.

• Professor Woollard is honorary consultant paramedic and director, pre-hospital, emergency and cardiovascular care applied research group, Coventry University

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