テノン囊下麻酔と球後麻酔との経時的なBモードエコー所見の変化および眼球に与える影響の比較

A comparison between sub-Tenon's and retrobulbar anesthesia in the B-mode echo findings over time and the effects on eyes

要約　目的：テノン囊下麻酔と球後麻酔との経時的なBモードエコー所見の変化，眼球運動抑制および眼圧の推移，術中疼痛について比較検討したので報告する。

方法：黄斑疾患（黄斑前膜，黄斑円孔）に対し硝子体手術を施行した22例24眼を対象とした。12眼ずつテノン囊下麻酔と球後麻酔を施行し，麻酔投与前後においてBモードエコー検査，眼球運動のスコアリング，眼圧測定を行った。術中の疼痛は11段階のNumerical Rating Scale（NRS）を用い術後に評価した。

結果：テノン囊下麻酔群では，投与直後において眼球後壁の視神経付着部に膨隆する低輝度エコー像を12例中11例で認めた。一方，球後麻酔群では，投与直後において筋円錐内全体に広がる低輝度エコー像を12例中5例に認めた。眼球運動スコアは，投与5分後においてテノン囊下麻酔群でより眼球運動が抑制される傾向にあったが，投与直後，5分後，10分後，15分後の各時点で有意差はなかった（p＝0.67，0.027，0.20，0.37）。投与前，投与直後，投与10分後の眼圧に有意差はなかったが（p＝0.58，0.52，0.48），テノン囊下麻酔群の1例で投与直後に45.6mmHgに上昇した。NRSはテノン囊下麻酔群で0.83±1.5，球後麻酔群では1.7±1.7と鎮痛効果に有意差はなかったが（p＝0.42），NRS＝0は前者で8例，後者で4例であった。

結論：テノン囊下麻酔は薬液分布の再現性が高く，より早期から安定した眼球運動抑制と鎮痛効果を発現する傾向を認めた。ただしテノン囊下麻酔では，投与直後の急激な眼圧上昇の可能性に注意する必要がある。

Abstract　Purpose：To report a comparison between sub-Tenon's and retrobulbar anesthesia in the changes of B-mode echo findings over time, the effect of akinesia, the changes in intraocular pressure, and the analgesic effect.

Methods：We reviewed 24 eyes of 22 cases who were treated for epiretinal membrane（ERM）or macular hole（MH）. We performed two types of anesthesia in 12 cases each, scanned the eye by ultrasonography, and measured the degree of eye movement and intraocular pressure before and after anesthesia. After surgery, we assessed intraoperative pain with Numerical Rating Scale（NRS）on a scale of 0 to 10.

Results：In the sub-tenon's group, the anesthetic fluid surrounded the optic nerve behind the globe immediately after injection. This image was visualized in 11 of 12 cases. On the other hand, in the retrobulbar, the anesthetic spread throughout the muscle cone. This finding of B-mode was seen in only 5 of 12 patients. In comparison of the mean eye movement scores, there was no significant difference between the two groups in any of the items immediately, 5 minutes, 10 minutes, and 15 minutes after injection（P＝0.67, 0.027, 0.20, 0.37）, however 5 minutes after anesthesia, the effect of akinesia tended to be stronger in the sub-Tenon anesthesia group. In the changes in intraocular pressure before and after injection, there was no significant difference between the two groups（P＝0.58, 0.52, 0.48）. But in the sub-Tenon's group, the intraocular pressure was elevated to 45.6 mmHg in only one patient immediately after anesthesia. When comparing the analgesic effects of the two groups, Numerical Rating Scale（NRS）was 0.83±1.5 in the sub-Tenon anesthesia group and 1.7±1.7 in the retrobulbar without significant difference between the two groups（P＝0.42）, but there were 8 patients who felt no pain at all（NRS＝0）in the former and 4 patients in the latter.

Conclusion：Sub-Tenon's anesthesia was highly reproducible in the distribution of injected fluid tended to exhibit a stable akinesia and analgesia from an earlier stage. But attention should be paid to the possibility of a sharp increase in intraocular pressure immediately after injection.