Effectiveness of sensorial saturation in relieving pain in term newborns

Newborns feel pain (1, 2). Repeated painful stimuli lower their pain threshold (3, 4) by overstimulation of NMDA receptors, which may lead to excitotoxic brain damage (5). Until a few years ago, it was claimed that the word pain was inappropriate for newborns, as pain is a subjective experience that newborns, because of their age, cannot have (6). Until the 1980s, analgesics were rarely administered to newborns even in the case of surgery (7). Now we know that anesthesia reduces brain damage due to hypoxemia, hypertension, tachycardia, variations in heart rate, and increased intracranial pressure (8, 9), all of which are particularly dangerous because of immature cerebral vasoregulation in the premature (10).
The number of painful stimuli needs to be kept to a minimum, and every effort should be made to render them less painful. Guidelines for neonatal analgesia have been suggested (11–15), especially for the most routine type of pain, blood sampling, which is usually performed by heel prick. To avoid the drawbacks of general and local analgesics (16–21), types of nonpharmacologic analgesia have been proposed, including nonnutritional sucking and instillation of glucose or other sweet liquids on the newborn’s tongue (22). The analgesic effect of glucose is thought to stimulate an increase in plasma concentrations of β-endorphin (23–27) by a preabsorptive mechanism (28).
Sensory stimuli combined with oral glucose during heel prick greatly reduced manifestations of pain in preterm babies (29). This combination was even more effective in premature babies than oral glucose. It was called sensorial saturation (SS) because it works through competition between nonpainful and painful stimuli, not to indicate that nonpainful stimuli cause saturation of sensorial pathways. In the present study, we investigate whether SS promotes analgesia in term babies and whether it is more effective than that obtained with sugar alone.

Material and methods
The retrospective study was performed in the San Filippo Neri Hospital, Rome (Italy). In our hospital babies routinely underwent two types of non-pharmacological analgesia when undergoing heelprick for blood sampling: oral 12% sucrose or sensorial saturation. Sensorial saturation consists of a multisensory stimulation composed of sweet taste (12% oral sucrose), touch (massaging the baby’s face) and talk (voice is used to distract the baby). Sucrose is instilled on the tip of the tongue with a sterile syringe, introduced in the infant’s mouth and moved to stimulate sucking. The amount of liquid, administered drop by drop, is that necessary to maintain sucking until after the heel-prick, i.e. 1 ml 2 minutes before heelprick. Sensorial saturation is administered as follows. After administering oral sucrose, the nurse began talking to the baby and massaging its face to distract him/her; two minutes after the beginning of these manoeuvres, heel prick was performed.
We usually give a pain score to all babies during these procedures using the NIPS scale, a validated pain scale scoring from 0 (no pain) to 7 (maximum pain).
We retrospectively included in this study all babies with the following features: (1) postconceptional age >35 weeks; (2) intraventricular hemorrhage (IVH) Mean scores in the two study groups were statistically compared using the Student’s t test.

Babies who fulfilled the inclusion criteria were divided into two groups of 1360 babies each: one receiving oral 12% sucrose and one receiving Sensorial Saturation. The main pain scores of the two groups were respectively 4.16 (SD=0.64) and 0.71 (SD=0.84), with a statistically significant difference (p<0.001). Figure 1 reports the rate of presence in both groups (oral sucrose or sensorial saturation), of babies with distinct grades of NIPS scores.

Figure 1 - Pain scores with oral sucrose (A) and with sensorial saturation (B)
Figure 1 – Pain scores with oral sucrose (A) and with sensorial saturation (B)

This is the widest study ever conducted in the field of nonpharmacological analgesia in neonates, and the first that compares sensorial saturation with oral sucrose. The evidence that sensorial saturation is more effective than oral sucrose results from the statistical comparation and from the rate of high pain scores in the two study groups. These data confirm previous studies on the effectiveness of sensorial saturation. With SS, we found an almost complete absence of pain reaction during heel prick; the babies rarely cried, and if they did, only for a few seconds. Other researchers (30-34) succeeded in reducing crying of premature babies with oral sucrose, but the infants nevertheless cried for many seconds and in some cases for more than 1 min, much more than with our technique, which reduced the mean crying time in the 30 s after heel prick to 2.8 s. Haouari et al. (34) were on the right track when they wrote, “We don’t know whether simply cuddling an infant after heel prick is as effective in reducing crying as 50% sucrose.” In actual fact, concentrated sugar solution is much more effective than cuddling, but the latter or at least its sensory component, i.e. massage, voice, rocking, eye fixing, adds further analgesia to the analgesic effect of glucose and provides a human factor in the form of company to a baby facing pain. SS is a technique that can be used for all newborns undergoing blood samples or other minor painful procedures. This study included a high number of babies, and it is one of the most numerous studies in this field, with a consequent high strength. A major limitation is its retrospectiveness and the fact that it could not be blinded, since the nurse who scored pain was present at the procedure and could not ignore the type of analgesia the infant received.
More studies are necessary to assess the best analgesic treatment for babies during procedural pain; this study is an important benchmark.

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