Intravenous sedation prior to peribulbar anaesthesia for cataract surgery in elderly patients

Purpose

To investigate if pre-block iv sedation using midazolam, alfentanil, or a midazolam-alfentanil combination minimizes pain, reduces pain recall, and attenuates haemodynamic responses to peribulbar block; and to determine other factors influencing oxygen saturation (SpO₂) following iv sedation.

Methods

In a randomized, double-blind, placebo-controlled study, 120 patients, mean age 73 yr, having cataract surgery with peribulbar anaesthesia, were randomized to receive either normal saline, 1 mg midazolam, 500 μg alfentanil, or 0.5 mg midazolam plus 250 μg alfentanil. Blood pressure (BP), heart rate (HR) and pulse oximetry readings were recorded before injection of the study drugs, immediately after completion of the peribulbar block, and 10 min after the block. Pain from the anaesthetic block was assessed immediately after the block and after surgery using a visual analog scale, and recall of pain was assessed by telephone on the day after surgery.

Results

Pain scores were low in all four groups. Midazolamalfentanil reduced pain perception, and all iv sedation used reduced pain recall. Midazolam reduced systolic BP; alfentanil ± midazolam reduced HR. All iv sedation reduced SpO₂ more than did saline, but not usually to a clinically important level. Nine patients had a SpO₂ S 90%; all had received alfentanil with or without midazolam. It was not possible to predicoxygen saturation levels by any factors other than iv sedation and baseline SpO₂ levels.

Conclusion

Intravenous sedation with midazolam or alfentanil or in combination reduced pain perception, pain recall, and haemodynamic responses from peribulbar anaesthesia. Fifteen percent of patients given alfentanil developed clinically important oxygen desaturation. The use of fine gauge needles combined with slow injection of anaesthetic solution causes minimal discomfort, and routine iv sedation may be unnecessary.