Sub-tenon anesthesia - A prospective study 6,000 blocks

Background. An initial pilot study of 300 sub-Tenon local anesthetic blocks (STBs) for intraocular surgery established the effectiveness and patient acceptability of the technique. Following this, a decision was made in 1995 to change from sharp needle techniques to STB for all eye surgeries performed during local anesthesia at Auckland Hospital (Auckland, New Zealand) by reeducation of anesthetists and surgeons. At this point, sufficient data were not available to confirm that STB would avoid the complications associated with the passage of sharp needles into the orbit or would cause a different set of serious complications. Methods: A prospective study of the next 6,000 consecutive STBs performed at Auckland Hospital was carried out over a period of 6 yr (from 1995 to 2000). Results: Sub-Tenon block is very effective, with a surgeon and patient acceptability rate of 98.8%. Insertion of the sub-Tenon cannula and administration of the anesthetic produces minimal discomfort, being completely painless in 68.8% of cases. There were no serious block-related complications in this series, supporting the safety of the sub-Tenon technique. Conclusion: The experience at Auckland Hospital provides further support for the avoidance of passing sharp needles into the orbit.