Effectiveness of oxygenation and suction in cataract surgery:: is suction of CO2-enriched air under the drape during cataract surgery necessary?

Purpose To investigate the effectiveness of aspiration of expired air by a suction system on peripheral oxygen saturation (SpO(2)) and end tidal carbon dioxide (EtCO2) during cataract surgery. Materials and methods In total, 160 premedicated patients aged between 40 and 70 years (ASA I-III, classification of patients according to the American Society of Anesthesiologists) scheduled for cataract surgery under retrobulbar or peribulbar block were examined in a randomised, single-blind manner. The patients were sedated with 3 mg midazolam i.v. 15min before operation and were monitored with an anaesthesia monitor. Heart rate (HR), non-invasive mean arterial pressure (MAP), SpO(2) and EtCO2 were continuously measured using a standardised monitor. The first group (non-suction group, n = 80) received 4 L min(-1) O-2 with nasal cannule while the second group (suction group, n = 80) received 4 L min(-1) O-2 with nasal cannule, and the expired air was aspired with a Y-piece suction system. EtCO2 was measured with the line of the sampling tube in the anaesthesia monitor. Respiratory rate (RR) was counted for a period of 1 min at each measurement time with thoracic excursions. The results were evaluated by unpaired t-test and analysis of variance. Results Severe reduction Of SpO(2) and raising of EtCO2 were observed significantly in the first group during the operation. RR, HR and MAP increased due to hypoxaemia. In the second group, SpO(2) was stabilised at high levels and EtCO2 did not increase. RR, HR and MAP levels remained within the normal limits. Differences between the two groups were statistically significant (P<0.05). Conclusion During cataract surgery with local anaesthesia, SpO(2) decreases and RR, HR and MAP increase because of reinspiration of expired air under the drape. Insufflation of O-2 and aspiration of expired air with a suction system have prevented severe reduction of SpO(2) and raising of EtCO2. It was suggested that O-2 delivery and use of an aspiration system decreased the risk of hypoxaemia significantly in the patients undergoing the cataract surgery.