Calculation skills for nurses: intravenous fluid therapy

Abstract

T topic of calculation skills this time is intravenous (IV) fluid therapy. In May 2013, the National Institute for Health and Care Excellence (NICE) published draft guidelines on intravenous fluid therapy for adults in hospital. IV fluid therapy is amongst the most common interventions in hospitalized patients, but prescribing is often left to junior prescribers, particularly in noncritical care areas. An estimated 1 in 5 patients on IV fluid and electrolyte therapy is harmed through mismanagement, including death caused by either too much or too little fluid. NICE recommends that all healthcare professionals involved in prescribing and delivering IV fluid therapy need to be trained to assess fluid needs, and to prescribe, administer and monitor therapy. An individual 24-hour IV fluid management plan should include the type(s) of fluid, volume to be given and rate of administration. Fluid and electrolyte needs are estimated using the patient’s history, clinical examination, clinical monitoring and laboratory investigations. The regimen varies depending on whether the fluids are for routine replacement or resuscitation, and also considering the volume and electrolyte content of abnormal fluid losses and existing deficits or excesses. This articles considers the calculation of routine maintenance fluids. The initial prescription is restricted to: ■ Water: 25–30 ml/kg/day ■ Potassium, sodium and chloride: approximately 1 mmol/kg/day ■ Glucose: approximately 50–100 g/day to limit starvation ketosis. Prescribing thereafter varies according to the patient’s clinical and biochemical monitoring parameters. Fluid requirement may be reduced, for example, to 25 ml/kg/ day for elderly or frail patients and those with renal impairment or cardiac failure. For obese patients, the fluid requirement is based on ideal body weight (IBW) (Box 1): Expert advice is needed for patients with a body mass index greater than 40 kg/m2.