Complications of ophthalmic regional blocks: their treatment and prevention

Comparison of i.v. cannula and Stevens' cannula for sub-Tenon's block

BACKGROUND

Sub-Tenon's local anaesthesia (STLA) is growing in popularity for ophthalmic surgery, and is widely regarded as safer than the alternative sharp needle techniques. Although safe, STLA is not devoid of risk. Therefore, the effectiveness of a plastic i.v. cannula was compared with the traditional metal Stevens' cannula for delivering STLA.

METHODS

In a randomized, controlled trial, the efficacy of STLA administered by either a Stevens' sub-Tenon's metal cannula or a standard 20 G Optiva i.v. plastic cannula was compared; 120 patients, undergoing cataract surgery, were randomly allocated to one of the two groups. After STLA, the primary outcome measure, kinesia of the globe, was recorded at 5 and 10 min.

RESULTS

There was no significant difference in the mean total ocular movement scores after STLA performed by either the 20 G i.v. cannula or standard 19 G sub-Tenon's cannula (P = 0.10). There was also no significant difference in any of the secondary outcome measures.

CONCLUSIONS

A 20 G Optiva i.v. cannula and the Stevens' sub-Tenon's cannula were equally effective at providing STLA.

Death potentially secondary to sub-Tenon's block

An 82-year-old ASA 2 patient underwent routine sub-Tenon's block for cataract surgery. One minute after injection of the local anaesthetic, the patient had a generalised tonic-clonic seizure and developed refractory ventricular fibrillation; subsequent resuscitation was unsuccessful. With no evidence for intravascular injection, the lack of structural brain abnormalities, and the most striking feature on post mortem examination being severe triple vessel coronary artery disease, it was concluded that this was primarily cardiac in origin; however, the possibility of brainstem anaesthesia should also be considered.