• G Iohom, A Whyte, T Flynn, G O'Connor, and G Shorten.
• Cork University Hospital and University College Cork, Department of Anaesthesia and Intensive Care Medicine, Cork, Ireland. iohom@hotmail.com
• Eur J Anaesthesiol. 2004 Apr 1;21(4):272-8.

Background And ObjectiveWe tested the hypothesis that disturbances of the visual pathway persist following general anaesthesia, even after normal clinical discharge criteria have been met.MethodsWe performed full-field flash electroretinography in the right eye of 10 unpremedicated ASA I patients who underwent N2O/sevoflurane anaesthesia. Electroretinograms were recorded preoperatively, immediately after discharge from the recovery room and 2 h after discontinuation of sevoflurane. The time at which postanaesthesia discharge score first exceeded 9 was also noted. Data were analysed using paired, one-tailed Student's t-test.ResultsLatency of the b-wave on the photopic electroretinogram was greater at each postoperative time point (30.5 +/- 0.9 and 30 +/- 1.3 ms), compared to preoperative values (29.2 +/- 0.8 ms, P < 0.001 and P = 0.04, respectively). The A-B amplitude of the b-wave was less postoperatively (220.3 +/- 52.7 and 210.3 +/- 42.7 pV) compared to values before operation (248.1 +/- 57.6 microV, P = 0.03 and P = 0.01, respectively). Oscillatory potential latencies were greater at each postoperative time point (21.4 +/- 0.5 and 20.8 +/- 0.6 ms) compared to before operation (20.4 +/- 0.4 ms, P < 0.001 and P = 0.03, respectively). Oscillatory potential amplitudes were less at the first postoperative time point (17.5 +/- 6.1 microV), compared to preoperative values (22 +/- 6.4 microV, P = 0.04).ConclusionsPostoperative electroretinogram abnormalities are consistently present in patients who have undergone N2O/sevoflurane anaesthesia. These abnormalities persist beyond the time at which standard clinical discharge criteria have been met.

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