Optimal provision of nutrition support and accurate assessment of energy expenditure should form an integral component of paediatric critical care (Mehta et al, 2009a). Nutritional status has a profound effect on the metabolic response to injury and can impact significantly on patient outcome (Mitchell et al, 1994) including length of ventilated days and overall length of PICU stay (Larsen et al, 2008). The goal of nutrition support in the critical care setting aims to augment the short term benefits of the paediatric stress response while minimising the long term harmful consequences associated with undernutrition.
It is widely accepted that enteral nutrition is the preferred method of feeding due to its physiological advantages of maintaining gut integrity and reducing infectious complications compared with parenteral nutrition. There are numerous studies which suggest that early implementation of nutritional support (within 24hrs) is associated with improved clinical outcomes, shorter length of stay, decreased infection rates and enhanced immune function (Petrillo-Albarnano et al 2006). This supports the theory that systematic initiation of enteral nutrition may improve patient outcomes in critical illness.
Providing nutritional care in critically ill children poses a number of challenges including fluid restriction, digestive intolerance and interruptions in enteral feed delivery for diagnostic and therapeutic procedures (Lambe et al, 2007, Mara et al, 2004) resulting in a failure to deliver estimated energy requirements (Gentles et al. 2014, Mara et al. 2014, Cohen et al 2000 and de Neef et al, 2007). Failure to provide nutritional intake equal to or exceeding the predicted basal metabolic rate (PBMR) is associated with higher mortality and morbidity rates (Briassoulis et al, 2001).
The lack of controlled research and clinical trials in critically ill children has resulted in an absence of widely accepted evidence based guidelines for optimal nutritional management in this group (Van der Kuip et al, 2004). However many UK PICU’s have implemented local guidelines for introducing and establishing enteral nutrition in their critically ill populations. It has been reported that this has resulted in more rapid initiation of enteral feeding, shortened the time taken to reach nutritional goals and improved the tolerance of enteral feeding (Gentles et al. 2014, Petrillo—Albarnano et al, 2006 and Briassoulis et al, 2001).
Measurement of gastric residual volumes (GRVs) is used routinely to assess enteral feed tolerance in both adult and paediatric critical care units. Elevated GRVs are associated with sedation and catecholamine use (Mentec et al, 2001) and in paediatric patients are often attributed to gastroparesis. There is wide debate over the use of measuring GRVs to assess feed tolerance. Although McClave et al (2005) state that GRVs are inherently flawed as they have yet to be validated, current opinion also suggests that a GRV > 5ml/kg can be considered to be an indicator of poor feed tolerance and delayed gastric emptying (Cobb et al, 2004 and Horn et al, 2004).
A local guideline addressing both the introduction and advancement of enteral feed as well as the measurement of GRVs should improve nutritional delivery in PICU.
Initiating nutritional support in infants following cardiac surgery is influenced by a number of factors but principally the clinical assessment of cardiac output is crucial in deciding whether to initiate enteral or parenteral nutrition. Reduced cardiac output particularly when requiring inotropic support results in increased concern regarding splanchnic hypoperfusion and gut ischaemia. Patients with single ventricle physiology (i.e. HLHS following Norwood stage 1 palliation), reliant on a balanced circulation may be at increased risk of compromised splanchnic blood flow (Owens and Musa, 2009). Novel monitoring modalities have recently demonstrated impaired mesenteric/splanchnic tissue oxygenation in neonates who develop necrotising enterocolitis (NEC) (Fortune et al, 2001) and similarly in a case study of a patient with congenital heart disease who developed NEC (Stapleton et al 2007). The risk of NEC in neonates with congenital heart disease is substantial (McElhinney et al, 2000).
Following cardiopulmonary bypass Malagon et al (2005) identified that gut permeability is increased and damage to the intestinal mucosa is sustained, this once again leads to increased concern regarding the introduction and advancement of enteral nutrition in such a fragile patient group due increased concern of necrotising enterocolitis (NEC). Similarly, increased gut mucosal permeability leading to compromised intestinal integrity has been found in patients undergoing veno-arterial extracorporeal membrane oxygenation (ECMO), leading to bacterial translocation and sepsis (Kurundkar et al 2010; Piena et al, 1998). Introducing enteral nutrition in patients undergoing veno-venous ECMO has been reported to be safe in the adult population (Scott et al, 2004) and the use of enteral feeding in neonates on both VV and VA ECMO is advocated, however, the rate at which enteral feed should be advanced has yet to be examined (Piena et al, 1998, Pettignano et al, 1998 and Hanekamp et al, 2005).
A study in stable preterm neonates found that splanchnic oxygenation increases following bolus gastric feeding (Dave et al, 2009), however, in patients at risk of mesenteric ischaemia this increased oxygenation demand may further increase the risk of NEC and warrants further research. It could be argued that continuous feeding may be more appropriate than bolus, thereby reducing the demand on mesenteric oxygen consumption.
The introduction of feeding algorithms in patients with HLHS have been shown to enhance nutritional care and patient outcome (Castillo et al 2010; Braudis et al, 2009) and the introduction of such guidelines for patients identified as ‘High Risk Abdomen’ may also achieve similar improvements in patient morbidity and mortality.
