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Royal Hospital For Sick Children
The absence of a licensed, ready-to-use aqueous total parenteral nutrition (TPN) formulation in the UK for children from birth to two years old means that at the Royal Hospital for Sick Children (RHSC), Edinburgh – a 150-bed teaching hospital – TPN has always been aseptically compounded from constituent ingredients by pharmacy staff. This is a labour-intensive process and there are risks of dispensing errors.
TPN formulations were previously tailored to the exact fluid requirements of the patient, with the advantage that regardless of the volume available, nutrition could be maximised. Unlike older children and adults, this patient group normally receives two separate solutions for infusion – an aqueous bag containing nitrogen, glucose, water, electrolytes, trace elements and water-soluble vitamins and a lipid bag containing fat and fat-soluble vitamins. The volume and content of the aqueous bag varies hugely depending on the age of the patient, a neonate often requiring less than 100 ml/day compared to a 13 kg two-year-old who requires around 1 l.
In 2005 a combination of factors indicated that at our hospital this method of TPN preparation was unsustainable. Increasing numbers of TPN patients meant pharmacy technical staff were aseptically preparing up to 15 bags per day. Our validated transfer of all materials into the two TPN preparation cabinets from the support room involved wiping and then spraying with sterile alcohol, which is time- and resource-intensive during busy periods. Additionally, the constant use of isolator cabinets meant that pharmacy technicians were suffering from repetitive strain injury (RSI) to their arms and backs.
It was decided to consider options for service redesign, with the intention of making the service more efficient without detriment to patient care or to pharmacy staff. Investigations began to determine whether a standard off-the-shelf aqueous TPN bag could be formulated which met the nutritional requirements of children up to two years old.
Analysis of 12 months of TPN prescriptions for patients in this age group (n = 1,540 prescriptions) confirmed that 80–90% received regimens that were theoretically amenable to standardisation. Discussion with peers in six paediatric centres in the UK, and with Intra-Tech, a supplier of unlicensed “TPN specials”, confirmed that no single standard formulation was available. There is a Scottish neonatal standard bag (SNB), but this provides insufficient calories in the volume provided (300 ml or 500 ml), for all but the most premature of neonates.
Current national nutrition guidelines for the age group were reviewed and a 1 l RHSC TPN regimen formulated (see Table 1). The aim was to provide 24 hours’ nutrition for the larger patients with the benefit of infusing for 48 hours continuously for our smaller patients, according to RHSC practice. The electrolyte requiring most frequent individualisation in the hospital was potassium and consequently this was left out of the formulation, to allow its addition in the pharmacy aseptic unit.
Chemical stability information for the formulation provided from Fresenius Kabi supported a 90-day shelf-life in the fridge. Further stability with the addition of a range of electrolytes, vitamins and trace elements gave up to seven days in the fridge plus one day at room temperature or six days refrigerated plus two days at room temperature.
The RHSC bag was manufactured by Intra-Tech at costs comparable to those for in-house aseptic preparation. To enable electronic formulation and production of worksheets and labels, its formulation was set up on our ASCribe TPN database.
A written TPN prescribing scheme was developed and agreed with the multidisciplinary hospital nutrition team. Younger patients start on the SNB before stepping up to the RHSC bag after 1–2 days. At its maximum and when clinically appropriate, the RHSC bag provides nutrition of 0.58 g/kg nitrogen and 18.3 g/kg glucose in approximately 116 ml/kg of fluid (total daily intake of approximately 135 ml/kg when taking into account 3.5 g/kg lipid). Larger children (9–13 kg) start and reach maintenance TPN solely using the RHSC bag (see Table 2).
In the 20 months since starting this prescribing regime, 1,558 patient days have resulted in 178 (11.4%) prescriptions for the SNB, 1,106 (71%) for the RHSC bag and 274 (17.6%) for individually tailored regimens. Trace elements, water-soluble vitamins and potassium are the only additions to the RHSC bag for the majority of patients. Tailor-made bags are now reserved for very specific uses, including long-term TPN patients with short-bowel syndrome or severely fluid-restricted patients in ICU. For the remainder of patients, for whom TPN provides only a short-term nutritional requirement, the RHSC bag has been a resounding success: no clinical problems have been detected by the RHSC nutrition team since the standardisation regime started.
For pharmacy the new working practice has many benefits, including:
Using the combination of the RHSC and Scottish neonatal bags it has been shown that a standard-bag approach to TPN in the 0–2 age group does provide suitable nutrition for the majority of patients without compromising clinical care. The pharmacy department has benefited hugely from streamlining the whole TPN prescribing and dispensing process. Those involved with TPN now have more time to spend carrying out other clinical and aseptic commitments, while having to work overtime is now a rarity in the aseptic unit.
1. Koletzko B, Goulet O, et al. Guidelines on paediatric parenteral nutrition of the European Society of Paediatric Gastoenterology, Hepatology and Nutrition and the European Society for Clinical Nutrition and Metabolism, supported by the European Society of Paediatric Research. J Paediatr Gastro Nutr 2005;41:S1-87.
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