ABSTRACT
Changes in intra-ocular pressure during spontaneous ventilation with a laryngeal mask were compared with controlled ventilation using a tracheal tube in 40 patients undergoing intra-ocular surgery Under general anaesthesia. Intra-ocular pressure was measured before induction, after establishing the airway, at the end of the operation and after removal of the airway device. Anaesthesia was induced with propofol and maintained with isoflurane and nitrous oxide in oxygen. Mean end -tidal carbon dioxide tension was significantly higher during spontaneous ventilation than during controlled ventilation 5 minutes after establishing the airway [42 +/- 0.7 Torr versus 38.5 +/- 0.5 Torr] and at the end of surgery [45.7 +/- 0.7 Torr versus 31.5 +/- 0.2 Torr] [p < 0.001]. Despite this, intra-ocular pressures were lower than the base line and similar in the two groups throughout anaesthesia. At the end of surgery, intraocular pressure [mmHg] was [11.0 +/- 4.5] and [8.2 +/- 3.1] during spontaneous or controlled ventilation respectively, one minute after removal of the device, mean intra-ocular pressure [mmHg] in the tracheal tube group [16.1 +/- 4.5] was slightly higher than base line [15.5 +/- 3.1] and was significantly higher than the laryngeal mask group [10.7 +/- S.4] [p <0.01]. Spontaneous ventilation with a laryngeal mask is an acceptable alternative to controlled ventilation with tracheal intubation in elective intraocular surgery