Varela Lopez O, Alvarez Vazquez J C, Gonzalez Cantalapiedra A, Rosolen S G
Hospital Clinico Veterinario Rof Codina, Lugo, Spain.
Doc Ophthalmol. 2010 Aug;121(1):9-20. doi: 10.1007/s10633-010-9223-4. Epub 2010 Feb 10.
To evaluate the effects of induced hypercapnia on the electroretinogram (ERG) in beagle dogs anaesthetized with isoflurane and sevoflurane. Binocular, full-field flash photopic and scotopic ERGs were obtained from six healthy neutered female beagle dogs. In order to determine Vmax and the photopic negative response (PhNR), photopic ERG luminance-response curves were generated with 17 different light stimuli. Photopic flicker ERGs were obtained at 30-Hz temporal frequency. Scotopic ERGs were recorded after 35 min of dark adaptation. For all animals, this procedure was performed once in four different sessions: isoflurane + end-tidal [CO(2)] at 35 mmHg +/- 3 mmHg (ISON), isoflurane + end-tidal [CO(2)] at 65 mmHg +/- 3 mmHg (ISOH), sevoflurane + end-tidal [CO(2)] at 35 mmHg +/- 3 mmHg (SEVON), isoflurane + end-tidal [CO(2)] at 65 mmHg +/- 3 mmHg (SEVOH). In photopic conditions, b-wave amplitudes were significantly smaller in hypercapnic groups (ISON = 170.6 +/- 12.1 microV; ISOH = 132.6 +/- 24.9 microV; SEVON = 170.9 +/- 14.4 microV; SEVOH = 130.2 +/- 22.8 microV). Similarly, in scotopic conditions, b-wave amplitudes were significantly decreased when CO(2) was increased (ISON = 89.4 +/- 14.7 microV; ISOH = 58.2 +/- 17.6 microV; SEVON = 93.4 +/- 24.1 microV; SEVOH = 56.2 +/- 22.2 microV). Flicker peak times were significantly increased in hypercapnic groups (ISON = 25.9 +/- 0.4 ms; ISOH = 27.7 +/- 1.2 ms; SEVON = 25.9 +/- 1.5 ms; SEVOH = 27.2 +/- 0.7 ms). Our results clearly indicate that induced hypercapnia significantly alters the genesis of the electroretinogram at level of ON-pathway and suggest that OFF-pathway is unaffected and that ERGs obtained from isoflurane or sevoflurane anaesthetized dogs are almost identical. Control of hypercapnia must be taken into consideration when ERGs are performed under inhaled anaesthesia in dogs.
评估诱导性高碳酸血症对异氟烷和七氟烷麻醉的比格犬视网膜电图（ERG）的影响。从6只健康的绝育雌性比格犬获得双眼全视野闪光明视和暗视ERG。为了确定最大反应速度（Vmax）和明视负反应（PhNR），用17种不同的光刺激生成明视ERG亮度-反应曲线。在30赫兹时间频率下获得明视闪烁ERG。暗适应35分钟后记录暗视ERG。对于所有动物，此程序在四个不同阶段各进行一次：异氟烷+呼气末[CO₂] 35 mmHg±3 mmHg（ISON）、异氟烷+呼气末[CO₂] 65 mmHg±3 mmHg（ISOH）、七氟烷+呼气末[CO₂] 35 mmHg±3 mmHg（SEVON）、七氟烷+呼气末[CO₂] 65 mmHg±3 mmHg（SEVOH）。在明视条件下，高碳酸血症组的b波振幅显著较小（ISON = 170.6±12.1微伏；ISOH = 132.6±24.9微伏；SEVON = 170.9±14.4微伏；SEVOH = 130.2±22.8微伏）。同样，在暗视条件下，当CO₂增加时b波振幅显著降低（ISON = 89.4±14.7微伏；ISOH = 58.2±17.6微伏；SEVON = 93.4±24.1微伏；SEVOH = 56.2±22.2微伏）。高碳酸血症组的闪烁峰值时间显著增加（ISON = 25.9±0.4毫秒；ISOH = 27.7±1.2毫秒；SEVON = 25.9±1.5毫秒；SEVOH = 27.2±0.7毫秒）。我们的结果清楚地表明，诱导性高碳酸血症在ON通路水平显著改变视网膜电图的发生机制，并表明OFF通路未受影响，且从异氟烷或七氟烷麻醉的犬获得的ERG几乎相同。在犬吸入麻醉下进行ERG检查时，必须考虑控制高碳酸血症。
