3 The technology
3.1 Fluid replacement therapy (intravenous infusion of fluid) attempts to reverse the effects of hypovolaemia by increasing circulatory blood volume and blood pressure back towards normal, in order to maintain the perfusion of vital organs and to reduce the risk of death from multiple organ failure.
3.2 IV fluids used in the treatment of trauma patients are regulated as medicines, and are broadly classified as crystalloids, colloids, or combination fluids consisting of hypertonic saline with either starch or dextran. Paramedics may legally administer crystalloid and colloid solutions, including succinylated modified fluid gelatine, compound sodium lactate intravenous infusion, and sodium bicarbonate and sodium chloride infusions. Crystalloids are solutions of small ionic or non-ionic particles in water (salt or small sugars such as glucose), which pass through cell membranes into different body fluid compartments but over time become eliminated from the intravascular compartment. Fluid replacement with crystalloid solutions requires three to four times the volume of fluid to produce a given expansion in the intravascular compartment. Colloid solutions contain large molecules (molecular weight > 10kDa) of albumin, gelatins, polysaccharides or starch, which are unable to cross cell membranes, and remain in the intravascular fluid compartment for much longer. Smaller infusion volumes are required for fluid replacement with colloid fluids than with crystalloids.
3.3 According to manufacturers' list prices, the cost of crystalloid solutions is about £1–£1.80 per 500 ml unit, compared with about £4–£16.50 per 500 ml unit for colloid solutions, excluding VAT. The list price of HyperHAES (a combination fluid comprising hypertonic saline solution and starch) is £28 per 250 ml unit, which is higher than for other colloids. HyperHAES is intended for single-dose administration and may be followed by standard volume-replacement therapy. Costs may vary in different settings because of negotiated procurement discounts.
3.4 There are two approaches to the timing of IV fluid replacement in trauma. One approach is to start IV fluid replacement in the pre-hospital setting; this may be done by paramedics or doctors trained in ALS, either at the accident scene or in the ambulance en route to hospital. Administration of IV fluid before arrival at hospital may reduce the risk of tissue and organ damage in patients with severe hypovolaemia and may improve survival. However, potential benefits from stabilising the patient before transportation should be balanced against risks associated with increased delays in reaching hospital and with the possibility that restoring the blood volume and increasing the blood pressure back towards normal may exacerbate haemorrhage. Initiation of fluid replacement en route to hospital confers any potential benefits of early fluid replacement while minimising time delays at the accident scene.
3.5 The other approach is to delay IV fluid replacement until patients arrive at hospital, where they receive definitive treatment for their injuries. Fluid may be administered before, or in conjunction with, the surgical management of haemorrhage. Delaying fluid replacement minimises time delay at the accident scene. Delaying fluid replacement is also believed to reduce the risk of re-bleeding caused by the mechanical disruption of blood clots and the dilution of clotting factors, which can occur, particularly when large volumes of IV fluid are administered.
3.6 The setting for the initiation of fluid replacement is the main focus of this appraisal; other issues, such as delayed hospital arrival and the efficacy of different fluid types, are subsidiary considerations.
3.7 A professional Consensus Statement on pre-hospital administration of fluid in trauma patients has been developed by the Faculty of Pre-hospital Care and the Royal College of Surgeons of Edinburgh, with representation from the Faculty of Accident and Emergency Medicine, the United Kingdom Military Defence Forces, the Ambulance Service Association, BASICS, the London Helicopter Emergency Medical Service and researchers with an interest in pre-hospital care. There are also clinical guidelines, developed by the Joint Royal Colleges Ambulance Liaison Committee (JRCALC). Both of these documents recommend a cautious policy on IV fluid resuscitation.
3.8 In the absence of data on the audit and monitoring of the JRCALC guidelines for IV fluid replacement in trauma, it is difficult to establish current adherence to them.