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Biomedical subjects

N Rutter

Publications and source records attributed to N Rutter.

At least 19 recordsLinked to original sources

Ultrasound study of heel to calcaneum depth in neonates.

AIM: To investigate whether it would be safe to extend the currently recommended area of sampling to the whole heel in neonates. METHODS: Eighty newborn infants were studied, weight range 0.56 to 4.34 kg, gestation 24 to 42 weeks. Ultrasound scanning was used to measure the shortest distance between the skin and the perichondrium of the calcaneum. RESULTS: The shortest depth of perichondrium was in the centre of the heel and ranged from 3 to 8 mm. In 78 of the 80 infants the distance was 4 mm or more. There was a small but significant positive correlation with weight. CONCLUSIONS: Standard automated lancets for preterm use that puncture to a depth of 2.4 mm may be safely used anywhere over the plantar surface of the heel. The posterior aspect of the heel should be avoided. Reducing the density of heel pricks should reduce the associated pain.

Blood Specimen Collection

The childhood scars of newborn intensive care.

Many of the techniques used in newborn intensive care damage the skin and may lead to scarring. We have investigated a cohort of consecutive survivors of newborn intensive care for the presence of scars. Ninety of the original 100 children between the ages of 8 and 9 years were examined in detail by a single observer--the number, site and severity of the scars were noted and compared with the findings when the children were 2 years old. There was an overall reduction in the number of scars with time, regardless of gestational age. Scars from needlemarks were reduced by 41% and those from intravenous accidents by 70%, compared with those seen at 2 years. Scars from chest drains were still visible, in two cases requiring corrective surgery. Nine children and their families found that the scars caused them embarrassment. The only scars which did not usually improve with time and which were often judged to be worse cosmetically were those caused by surgery.

Bandages

Urinary excretion of 5-L-oxoproline (pyroglutamic acid) during early life in term and preterm infants.

Urinary 5-L-oxoproline was measured in term and preterm infants from shortly after birth until 6 weeks of postnatal age to determine their ability to synthesise glycine. In term infants the excretion was five to 10 times that seen in normal adults, increasing from 105 mumol/mmol creatinine in the first 72 hours after birth to 170 mumol/mmol creatinine at 6 weeks of age. There was a significant inverse linear correlation between the excretion of 5-L-oxoproline and length of gestation or birthweight. By 6 weeks of age there was no longer a significant difference in 5-L-oxoproline between term and preterm infants. There was no difference in the excretion of 5-L-oxoproline between boys and girls, or between infants fed on human milk or an artificial formula. If, in part, variability in the excretion of 5-L-oxoproline is determined by the extent to which the endogenous formation of glycine is adequate, then glycine formation may be marginal during early life, more so in preterm than in term infants, providing additional evidence that glycine is a conditionally essential amino acid in the neonate.

Birth Weight

The immature skin.

The skin of the extremely preterm infant is structurally and functionally immature at birth, although there is rapid postnatal maturation. The consequences of this immaturity are a high transepidermal water loss (leading to hypothermia and difficulty in fluid balance) accidental percutaneous absorption and toxicity, and skin trauma (leading to infection). Neonatologists must be aware of these and take measures to limit them.

Humans

Morphine, morphine-6-glucuronide and morphine-3-glucuronide pharmacokinetics in newborn infants receiving diamorphine infusions.

1. The pharmacokinetics of morphine, morphine-6-glucuronide (M6G) and morphine-3-glucuronide (M3G) were studied in 19 ventilated newborn infants (24-41 weeks gestation) who were given a loading dose of 50 micrograms kg-1 or 200 micrograms kg-1 of diamorphine followed by an intravenous infusion of 15 micrograms kg-1 h-1 of diamorphine. Plasma concentrations of morphine, M3G and M6G were measured during the accrual to steady-state and at steady state of the diamorphine infusion. 2. Following both the 50 micrograms kg-1 or 200 micrograms kg-1 loading doses the mean steady-state plasma concentration (+/- s.d.) of morphine, M3G and M6G were 86 +/- 52 ng ml-1, 703 +/- 400 ng ml-1 and 48 +/- 28 ng ml-1 respectively and morphine clearance was found to be 4.6 +/- 3.2 ml min-1 kg-1. 3. M3G formation clearance was estimated to be 2.5 +/- 1.8 ml min-1 kg-1, and the formation clearance of M6G was estimated to be 0.46 +/- 0.32 ml min-1 kg-1. 4. M3G metabolite clearance was 0.46 +/- 0.60 ml min-1 kg-1, the elimination half-life was 11.1 +/- 11.3 h and the volume of distribution was 0.55 +/- 1.13 l kg-1. M6G metabolite clearance was 0.71 +/- 0.36 ml min-1 kg-1, the elimination half-life was 18.2 +/- 13.6 h and the volume of distribution was 1.03 +/- 0.88 l kg-1. 5. No significant effect of the loading dose (50 micrograms kg-1 or 200 micrograms kg-1) on the plasma morphine or metabolite concentrations or their derived pharmacokinetic parameters was found. 6. We were unable to identify correlations between gestational age of the infants and any of the determined pharmacokinetic parameters. 7. M3G: morphine and M6G: morphine steady-state plasma concentration ratios were 11.0 +/- 10.8 and 0.8 +/- 0.8, respectively. 8. The metabolism of morphine in neonates, in terms of the respective contributions of each glucuronide pathway, was similar to that in adults.

Analgesics, Opioid

Capillary blood sampling: should the heel be warmed?

The hypothesis that capillary blood sampling is made easier by warming the heel was examined in a randomised, controlled trial of healthy newborn infants. Sampling was performed using an automated lancet with or without prior warming. The time taken to collect a standard volume of blood, the number of repeat procedures needed, and the infants' behavioural responses were measured. Eighty one procedures were studied in 57 infants. Warming produced a median rise in heel skin temperature of 4.7 degrees C. However, there were no significant differences between the warmed and unwarmed groups in any of the outcome measures. Heel skin temperature is not an important factor in capillary blood sampling. Attention should be directed towards improving sampling devices and technique.

Blood Specimen Collection

Stress, severity of illness, and outcome in ventilated preterm infants.

AIM: To determine physiological and hormonal stress responses in ventilated preterm infants. METHODS: Physiological and hormonal stress responses were studied in 47 ventilated preterm infants who were judged clinically to require sedation. The correlation between the stress response and severity of illness was examined, and responses were compared between infants with different clinical outcomes. RESULTS: Stress hormone concentrations were significantly correlated with severity of illness, assessed using the arterial: alveolar oxygen partial pressure ratio. Noradrenaline showed the strongest correlation, with an exponential pattern of increased secretion. Catecholamine concentrations before sedation were significantly higher among infants who subsequently died (n = 15, at a median age of 6 days) than among survivors: median noradrenaline 4.31 vs 2.16 nmol/l, median adrenaline 0.69 vs 0.31 nmol/l. The observed fall in noradrenaline with sedation was lower among those who died than survivors (median fall 2% vs 40%). CONCLUSION: Preterm infants are capable of hormonal stress responses appropriate for the severity of their illness. Extreme catecholamine responses, in the sickest infants, are associated with the worst outcome.

Epinephrine

Neonatal hypertension and cardiac failure.

Two newborn infants developed cardiac failure due to severe hypertension which was recognised as the heart failure was treated. Renal abnormalities were found in both infants who are normotensive off treatment at 18 months follow up. The finding of hypertension rather than hypotension in the presence of cardiac failure and the apparent absence of a cardiac abnormality should prompt a search for a renal or renovascular cause.

Female

Exposure to invasive procedures in neonatal intensive care unit admissions.

The nature and numbers of invasive procedures were studied in 54 consecutive infants admitted to a neonatal intensive care unit. Over 3000 procedures were recorded, 74% in infants below 31 weeks of gestation. One infant (23 weeks' gestation, birth weight 560 g) underwent 488 procedures. Heel prick blood sampling was the most common procedure (56%), followed by endotracheal suction (26%) and intravenous cannula insertion (8%). Invasive procedures which would cause pain or distress to a child are frequently performed on infants admitted to the neonatal intensive care unit. A reduction in the number of procedures, modifying them, or providing adequate analgesia could relieve some of this pain and distress.

Blood Specimen Collection

Lignocaine ointment and local anaesthesia in preterm infants.

The ability of topically applied lignocaine ointment to produce surface anaesthesia was examined in 45 preterm infants (gestational age 25 to 35 weeks) at a median age of 2 days. Two strengths of ointment, 5% and 30%, were tested at 30 and 60 minutes after application to the dorsum of the foot. Anaesthesia was assessed by comparing the response to skin stimulation at the test and control sites, using von Frey hairs. In 84% of cases responses indicated that there was no surface anaesthesia. Topically applied lignocaine ointment is not an effective local anaesthetic in preterm infants, presumably due to poor absorption.

Administration, Topical

Randomised, double blind trial of two loading dose regimens of diamorphine in ventilated newborn infants.

AIMS: To compare the safety and efficacy of two loading doses of diamorphine in 27 ventilated newborn infants in a randomised double blind trial. METHODS: Fifty or 200 mcg/kg were infused intravenously over 30 minutes, followed by a 15 mcg/kg/hour continuous infusion. Serial measurements were made of physiology, behaviour, and stress hormones. RESULTS: Both loading doses produced small but significant falls in blood pressure. The 200 mcg/kg dose produced greater respiratory depression, and two infants deteriorated clinically, requiring resuscitation. Loading reduced respiratory effort in most of the infants, but had little effect on behavioural activity. Stress hormone concentrations were reduced at six hours in both dosage groups; differences between loading doses were not significant. Morphine, morphine-3-glucuronide, and morphine-6-glucuronide were detected in the plasma of all patients. No significant differences in concentrations between loading doses were found. CONCLUSIONS: Diamorphine reduces the stress response in ventilated newborn infants. A high loading dose confers no benefit, and may produce undesirable physiological effects. A 50 mcg/kg loading dose seems to be safe and effective.

Analgesics, Opioid

Percutaneous lignocaine absorption in newborn infants.

The permeability of the skin of newborn infants to lignocaine was examined in vitro using excised skin. Samples were studied from 24 infants of gestational age 25 to 40 weeks and postnatal age 0 to 7 days. Mature skin was relatively impermeable to lignocaine, but the more premature infants showed a marked increase in absorption. There was a strong inverse correlation between gestational age and skin permeability. These findings suggest that topical lignocaine would be an effective local anaesthetic in preterm infants. Calculations indicate that there is negligible risk of toxicity due to systemic absorption.

Anesthetics, Local

Heel blood sampling in preterm infants: which technique?

Preterm infants undergoing heel blood sampling were randomly allocated to specimen collection by heel puncture (Autolet II Clinisafe) or incision (Tenderfoot 'preemie'). A total of 187 procedures was observed in 47 infants. No significant difference was found in the infants' behavioural response, increase in heart rate, or in the frequency of specimen haemolysis. Collection times for small to medium sized samples were similar, but for large samples (> 1 ml) the Tenderfoot method was superior and fewer repeat procedures were necessary. Tenderfoot has the added advantage of improved safety, but it is too costly for routine use.

Blood Specimen Collection

Transdermal delivery and the premature neonate.

Drugs can penetrate more readily through the skin of preterm neonates compared to adults. This observation suggests that transdermal drug delivery may offer advantages compared with the traditional intravenous or oral routes of drug administration used in neonatal intensive care. The transdermal route of drug delivery is potentially a convenient, painless, and noninvasive method of drug therapy without the difficulties, discomfort, and scope for error of intravenous or oral administration. Successful transdermal therapy in the neonate has been achieved with the drugs theophylline and caffeine, with therapeutic blood drug concentrations being achieved for up to 7 days after topical application. Several other drugs in common use in neonatal intensive care therapy have good potential for transdermal delivery. However, there is a need for further development of neonatal transdermal delivery systems to provide a controlled rate of drug delivery.

Administration, Cutaneous