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Re: Has ametop come to stay?

The authors of this paper need all appreciation in trying out this “magic cream” on babies, which already finds an established role in children as a topical anaesthetic.

However as one goes through this interesting article, a striking feature is the small numbers in the study. I find no mention as regards to the power of the study. The confidence limits while expressing significant p values is not mentioned.

Assessment of pain in neonates is a difficult area. The use of validated pain scores as a bedside tool is well taken. However in literature published on this subject, many authors express the importance of assessing the physiological response of babies to pain, like changes in heart rate, respiration, blood pressure,and saturation of oxygen. Moreover the level of arousal at the time of stimulation seems to hold a lot of importance. A baby who is asleep is far less prone to cry than one who is awake. In the present paper there seems to be no mention of the state of arousal of the baby at the moment of cannulation. Inclusion of neonatal behaviour scales would have boosted the value of this useful study.

As regards to the safety profile of the drug, it is not clear as to whether one could use 4% amethocaine in preterm babies as well. In preterm babies the risk of systemic absorption needs further looking into.

It is interesting to see in the future how topical amethocaine and oral sucrose fare against each other or add up to provide effective pain relief to the neonate.

Dr R Srinivasan
Department of Paediatrics
Scunthorpe General Hospital
North Lincolnshire, UK

References
(1) Jain A, Rutter N. Does topical amethocaine gel reduce the pain of venupuncture in newborn infants? A randomised double blind controlled trial. Arch Dis Child Fetal Neonatal Ed 2000:83:F207-10.

(2) Bozzette M. Observation of pain behavior in the NICU: an exploratory study. J Perinat Neonatal Nurs 1993;7:76-87.

(3) Grunau RV, Craig KD. Pain expression in neonates: facial action and cry. Pain 1987;28:395-410.

(4) Rushforth JA, Levene MI. Behavioral response to pain in healty neonates. Arch Dis Child Fetal Neonatal Ed 1994;70:F174-6.

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Re: Response to Dr Srinivasan

We thank Dr Srinivasan for his interest in our paper. For clarity, some of the original results were not included in the published paper. In response to his points:

To be clinically effective, a topical local anaesthetic agent should work in almost all cases. Whether the sample size was 20 or 100 seems less relevant. However, we considered that to be clinically effective, the proportion of newborn infants who feel pain in the topical amethocaine gel group should be no greater than 15%. In the placebo group, the rate of painful response to venepuncture was 70%. A Casagrande and Pike power computation (Fisher's Exact approximation) was conducted. A sample size of 11 per group would have a power of 83% to detect a statistically significant result (specifically a reduction from 70% to 15% painful response) (level of significance p=0.05).

As the data were non-parametric, a confidence limit was not calculated.

The Prechtl behaviour scores prior to venepuncture were not significantly different between treatment groups (amethocaine median 2 (IQR 1 - 3) vs. placebo median 0 (IQR 1 - 2), Z= -0.231, p= 0.841).