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

Abstract

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. Midazolam-alfentanil 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 ≤ 90%; all received alfentanil with or without midazolam. It was not possible to predict oxygen saturation levels by any factors other than iv sedation and baseline SpO2 levels.