Effective reduction of anxiety and pain during venous cannulation in children: a comparison of analgesic efficacy conferred by nitrous oxide, EMLA and combination

Background: EMLA cream is the current technique of choice to reduce pain during venous cannulation in most paediatric practice. Its use is limited by logistic arrangements and failure to improve cooperation and allay anxiety. Nitrous oxide (N2O) would appear to be an effective alternative. A combination technique may be useful in selected patients. Methods: One hundred and twenty unpremedicated ASA 1 and 2 day surgery patients, aged 8-15 years were randomized into group 1 (EMLA + air/O-2), group 2 (50% N-2 O/50% O-2) and group 3 (EMLA + 50% N-2 O/50% O-2). All patients underwent cannulation on the dorsum of the hand with a 22-G intravenous catheter. Pain behaviour before cannulation was assessed by an observer with Children's Hospital of Eastern Ontario Pain Scale (CHEOPS). Pain during cannulation was evaluated with CHEOPS by an observer and Visual Analogue Scale (VAS) (0-100 mm) by the patient. Satisfaction score (0-100%) for the experience were reported by the patient. Degree of ease of cannulation, time for cannulation were assessed. Heart rate, oxygen saturation were compared before, during and after cannulation. Results: The self-reported VAS for group 3 (10.10 +/- 14.99) was significantly lower than group 1 (26.13 +/- 27.59) and group 2 (18.35 +/- 18.11) (P = 0.003). No significant difference existed between VAS for group 1 and 2. There were also significantly more patients with VAS = 0 in group 3 (23/40) versus group 2 (11/40) versus group 1 (10/40), P = 0.004. The satisfactory score in group 3 (93 +/- 9.96) was significantly higher (P = 0.039) than group 1 (81.13 +/- 24.61) and group 2 (84 +/- 22.02). The increase in CHEOPS from before to during cannulation was significant only in group 1 (P = 0.002). There was no significant difference between frequency of patients with side-effects, ease of cannulation and time taken for cannulation in the three groups. Conclusions: EMLA and 50% N2O are equally effective for pain reduction while a combination technique provides superior analgesia and satisfaction. N2O has an advantage over EMLA in reduction of pain related behaviour in older children.