Normative values of substance P and neurokinin A in neonates.

BACKGROUND: Substance P (SP) and neurokinin A (NKA) are neuropeptides that have been researched as pain markers in adults, as they are involved in transmission and modulation of pain signals. There is a potential role for them as neurochemical markers of pain in neonates, but this has never previously been investigated. AIM: To establish normative values of SP and NKA in neonates. METHODS: Longitudinal once-daily morning blood samples were collected over two weeks from 142 neonates, gestation 23-40 weeks. Peptides were extracted, and then quantified using an in-house radioimmunoassay. Infants with presumed painful conditions were excluded. RESULTS: SP concentrations ranged from <0.98 to 11.2 pmol/L (median 1.7 pmol/L) and NKA concentrations from <1.95 to 74.6 pmol/L (median 6.0 pmol/L). Gestation and birth weight had no significant correlation with peptide concentrations. Postnatally, there was a gradual rise in median SP during the first three days, which decreased again by day 14. Median NKA showed a similar rise, but was not statistically significant. This postnatal rise and fall were more apparent in preterm infants < or = 32 weeks gestation. CONCLUSIONS: This is the first description of normative values of SP and NKA in neonates. SP and NKA show changes with postnatal age, which are more marked in preterm infants.

Assessment of persistent pain or distress and adequacy of analgesia in preterm ventilated infants.

Indicators of persistent pain in preterm neonates are poorly defined. In the setting of a double blind, placebo-controlled trial investigating morphine use in ventilated preterm infants (NEOPAIN Trial) we aimed to identify factors that may be useful in assessing persistent pain. Twenty-two babies (morphine 12; placebo 10) were assessed for comfort, pain or distress and clinical staff described the factors they had considered. This assessment was performed during the first period of duty with the baby. Based on this, they stated which study drug they believed the infant was receiving. Eighty-nine assessments were made in total (1-14 per baby). The drug was correctly identified on 71% of occasions. Staff considered one or more of the following factors: infant activity; response to routine care; known pain-related behaviours; posture/quality of movements; respiratory effort; synchrony with ventilator; blood pressure and heart rate. Four factors most frequently identified babies receiving placebo: facial expressions of pain, high activity levels, poor response to handling and poor synchrony with ventilation. Absence of pain-related behaviour was less discriminating. Observation of a good response to handling, good synchrony with ventilation, a "settled" baby, normal blood pressure and heart rate were poor discriminators. Hypotension and poor respiratory drive were noted exclusively in babies receiving morphine infusions. Facial expressions of pain, high activity levels, poor response to routine care, and poor ventilator synchrony were associated with placebo versus morphine therapy, and may be considered useful markers for persistent pain in preterm infants.

A comparison of transcutaneous bilirubinometers: SpectRx BiliCheck versus Minolta AirShields.

BACKGROUND: Two devices are available for making transcutaneous estimates of serum bilirubin (SBR): the Minolta AirShields JM102 and the new SpectRx BiliCheck. OBJECTIVES: (a) To measure how well the readings produced by these devices agree with SBR measured in the laboratory; (b) to estimate for each device, the proportion of infants with clinical jaundice who would require blood sampling if the device was used as a screening tool to detect infants with SBR > or = 250 micromol/l. DESIGN: Prospective cohort study of jaundiced infants who required SBR at < or = 20 days of postnatal age. Those who had received phototherapy or exchange transfusion were excluded. SETTING: Tertiary neonatal service in South-East Scotland. INTERVENTIONS: Within 30 minutes of SBR sampling, transcutaneous bilirubinometry was performed using one Minolta and two SpectRx devices (designated A and B). RESULTS: Sixty-four neonates were enrolled, 19 of which were preterm (31-35 weeks). The 95% confidence intervals of a device reading corresponding to SBR were +/- 66.7, +/- 67.9, and +/- 66.4 micromol/l respectively. Using the devices to identify all SBR > or = 250 micromol/l would reduce SBR sampling by 23%, 16%, and 20% respectively. CONCLUSIONS: Given that SBR levels range from 50 to 400 micromol/l in jaundiced infants, the 95% confidence intervals of the devices are wide at +/- 67 micromol/l. The SpectRx can be used as a screening tool for hyperbilirubinaemia but there is no advantage in using it over the Minolta.