A. A. Van Den Berg

Choice of tracheal tube size for children: finger size or age‐related formula?

A study was undertaken to compare the size of tracheal tube used for paediatric anaesthesia derived from either the diameter of the distal phalanx of the little or index finger, or from a standard formula (age in years/4 + 4.5 mm). The results showed that the diameter of the terminal phalanx was a poor predictor of the external diameter of the tube that provided the best fit. The mean (SD) diameters were 9.34 (1.02), 10.24 (1.23) and 7.56 (0.97) mm for the little finger, index finger and tracheal tube providing ‘best fit’, respectively. The formula provided a better correlation with the internal diameter of the chosen tracheal tube. The mean (SD) figures were 5.61 (0.75) and 5.70 (0.67) mm for the formula and the chosen tracheal tube, respectively. The use of the diameter of the terminal phalanx of either the little or the index finger is an unreliable measurement for the prediction of tracheal tube size in paediatrics.

An audit of peribulbar blockade using 15 mm, 25 mm and 37.5 mm needles, and sub‐Tenon's injection*

The efficacy of peribulbar anaesthesia performed with short, medium and long needles, with sub‐Tenons injection as a control, was audited. Two hundred patients undergoing cataract surgery underwent peribulbar injection using 25G needles of the following lengths: 15 mm, 25 mm or 37.5 mm. Sub‐Tenons injections were performed with a curved 25‐mm sub‐Tenon anaesthesia cannula. The injection technique, ocular akinesia and analgesia scoring system, and supplementary injection protocols were standardised. After initial injections of local anaesthetic via the sub‐Tenons cannula or with 37.5 mm, 25 mm and 15 mm needles, supplementation was required in one (2%), 13 (26%), 22 (44%) and 32 (64%) of patients, respectively; the total number of supplementary injections required were 1, 16, 35 and 47, respectively. It is concluded that the efficacy of peribulbar anaesthesia depends upon the proximity of the deposition of local anaesthetic solution either to the globe or orbital apex. These data justify the classification of peribulbar anaesthesia into: circum‐ocular (sub‐Tenons, episcleral), peri‐ocular (anterior, superficial); peri‐conal (posterior, deep) and apical (ultra‐deep) for teaching purposes.