Subcutaneous microdialysis for children - safe biochemical tissue monitoring based on a minimal traumatizing no touch...

Microdialysis (MD) enables analysis of extracellular metabolites without performing blood tests. Changes in the concentration of various metabolites can be monitored frequently on almost every type of human tissue. Microdialysis of subcutaneous tissue (sc MD) is of particular significance in the case of pediatric patients because diurnal profiles can be generated without repeated blood sampling. There are only a few scientific articles that describe the application of sc MD on neonates, infants, or children. So far, side effects have not been investigated comprehensively. This prospective study scrutinizes side effects of sc MD in pediatric patients, focusing on a Minimal Traumatizing Insertion Technique of the MD catheter.

42 pediatric patients within four age categories participated in the study which involved bedside monitoring using sc MD, including 5 extremely low birth weight (ELBW) infants with a body weight <1000g. A total of 48 sc MD catheters were inserted. Selection criteria were risk of hypoglycaemia (n = 29), elevated lactate levels (n = 16), or aminoacidopathies (n = 3). Duration of sc MD ranged from 1 to 16 days. We used a Minimal Traumatizing Insertion Technique to safely insert the MD catheter into the subcutaneous tissue, characterized by blunt dissection of the tissue and by the use of a plastic cannula guidance to avoid desterilisation of the catheter. Complications and side effects related to sc MD were documented in standardized forms.

The MD probe was easily placed even in the scanty adipose tissue of ELBW infants. During insertion of sc MD catheters accidental venous puncture occurred to 8%, and minor bleeding to 27%. Even with local anaesthesia insertion was painful for 40%. During the course of sc MD complications were rare: disturbance of perfusion flow 4%, catheter dislocation 4%, local bleeding 4%. No signs of systemic or local infection were observed, there were no cases of local incompatibility. All catheters were withdrawn completely without leaving a scar. Repeated measurements allowed the generation of diurnal metabolic profiles. In some cases (respiratory chain complex I deficiency, PDH-deficiency) significant therapeutical effects on the patients' metabolism were demonstrated.

The present study proves long-term sc MD to be suitable and safe for biochemical tissue monitoring. Using our insertion technique, it can be applied to children of all ages without causing discomfort or severe side effects. As it permits frequent sampling it allows evaluating and optimizing therapy and means a substantial progress for pediatric observation.