From Benchmark to Bedside, Use of Opioids in Neonates and Infants Undergoing Major Surgical Interventions: Essence for a Sufficient Nociceptive Blockade

While for a long time it has been perceived that neonates and young children do not perceive pain as the adult, this notion had to be corrected on the basis of neurophysiological data and the ontogenisis of the nociceptive system. Also, it has been demonstrated conclusively that neonates and the young infant perceive pain at a much lower nociceptive input which is largely due to a still immature inhibitory descending neuronal pathway. Minor inflictions are threfore perceived as a strong painful input, resulting in a greater size of the receptive field, long lasting pain sensations at high intensity, all which may have an impact on a lowering of the pain threshold, a change of behavioral patterns and a lesser performance at school at later life.Pain as being induced during surgery makes administration of potent opioids mandatory. One, however, has to take into consideration that because of the immature development of the opioid subreceptor system, before reaching a max. analgsic level, respiratory depression and muscular rigidity become apparent. In addition, because of the immaturity of liver enzymes, the age-related rapid change in the volume of distribution and the elimination half-life, the duration action of an opioid cannot be predicted. It is therefore is advisable to titrate the dose to effect and not on a mg/kg-basis.