Background and objective: We tested the hypothesis that disturbances of the visual pathway persist following general anaesthesia, even after normal clinical discharge criteria have been met.
Methods: We 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.
Results: Latency 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 μV) compared to values before operation (248.1 ± 57.6 μV, 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 μV), compared to preoperative values (22 ± 6.4 μV, P = 0.04).
Conclusions: Postoperative 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.