A comparison of local anaesthetics for venepuncture
- Dr J Arrowsmith, Department of Plastic Surgery, Leicester Royal Infirmary, Leicester LE1 5WW, UK
- Accepted 19 January 2000
AIM To compare the effectiveness of EMLA cream and Ametop gel in providing analgesia for venous cannulation.
METHODS Single blind study in 120 children.
RESULTS Both anaesthetic agents produced adequate analgesia. However, Ametop gel was more effective, with a statistically significant difference in the pain scores of the two groups (p < 0.05).
Topical local anaesthetic agents are proven to reduce the distress caused to children during venepuncture and venous cannulation.1 EMLA (eutectic mixture of local anaesthetics) has been available for a number of years and requires an application time of at least 60 minutes.2 Ametop gel (4% w/w amethocaine base preparation), a more recent preparation, has been shown to have a faster onset of maximum anaesthesia of 30–45 minutes.2
Previous comparative studies of the quality of anaesthesia have produced conflicting results. When both preparations were applied to adults for the recommended time for maximum anaesthesia, there was no statistical difference between the two preparations.3However, when applied to children, for a time shorter than that recommended for EMLA, Ametop gel appeared to provide superior anaesthesia.4 5
After obtaining ethics committee approval and informed parental verbal consent, 120 children undergoing a variety of routine and emergency procedures were studied.
Sixty boys and 60 girls, aged from 1 to 15 years old, were randomly allocated to receive either EMLA cream or Ametop gel. The preparations were applied to the dorsum of the hands and/or the feet and covered with an occlusive dressing. When the child was scheduled to go to theatre, the preparation was removed and both the duration of application and any local reaction of the skin noted. Either the paediatric nurse or the anaesthetist, who were blinded to the topical anaesthetic used, assessed the pain experienced by the child during venous cannulation using a five point behavioural scale.
The EMLA and Ametop groups were well matched. Table 1 shows the times of application, time to cannulation, and number of attempts at cannulation. These results were not significantly different, using the Yates corrected χ2 test.
EMLA produced significantly more blanching (p < 0.0001) and Ametop significantly more erythema (p < 0.018) at the site of application. There were no cases of hypersensitivity to either preparation.
The observed pain scores were significantly different between the two groups, the Ametop gel group exhibiting less response to cannulation than the EMLA group (p < 0.05; table 2). Excluding children who had more than one attempt at cannulation or children whose cannulation occurred later than four hours after application of the EMLA or five hours after application of the Ametop did not alter this result. These data were analysed using the Mann–Whitney test.
One boy experienced conjunctival irritation caused by rubbing his eye shortly after the Ametop gel had been removed from his hand. On review by an ophthalmologist, no corneal damage was identified and the conjunctivitis settled with conservative treatment.
The results of this study show that both topical anaesthetic preparations provide effective anaesthesia for venous cannulation in children.
EMLA cream produced more blanching of the skin and Ametop gel more erythema owing to the different actions of the anaesthetic agents, the lignocaine and prilocaine in EMLA cream being predominantly vasoconstrictive and amethocaine a vasodilator. The difference in local skin reaction did not, however, appear to influence the number of attempts needed for successful venous cannulation.
In this study, 72% of children in the Ametop group exhibited either no response or a mild facial grimace on cannulation compared with 55% of children in the EMLA group. Overall the children in the Ametop group showed significantly less pain than the EMLA group.