Objective

To develop a comprehensive formula for calculating the volume of local anaesthetic solution used for retrobulbar anaesthesia in dogs with different skull morphologies.

Study design

Retrospective cohort imaging study.

Animals

Skull computed tomography (CT) images of 188 dogs of different breeds collected between January 2009 and December 2017.

Methods

Anatomical integrity of the orbit and adjacent structures, presenting complaint, clinical signs and CT findings were verified to exclude ocular abnormalities. The volume of the retrobulbar cone of 376 eyes was calculated using CT scans of the dogs’ skulls. Additional data recorded included morphology of the skull, body weight, sex and size of the dogs, all of which were matched for possible association to the retrobulbar cone volume through univariable and multivariable linear regression models. Results of linear regression models were expressed as estimated beta coefficients with the corresponding 95% confidence intervals (95% CIs).

Results

Using univariate analysis, the retrobulbar cone volume was positively associated with weight and male sex. In addition, brachycephalic and dolichocephalic dogs showed a larger retrobulbar cone volume than mesocephalic dogs, while sex was no longer significantly associated with the retrobulbar cone volume. In multivariate analysis, when considering all variables in the model, weight emerged as the strongest predictor (beta coefficient: 0.062 mL kg^–1, 95% CI: 0.056–0.067 mL kg^–1, p < 0.001).

Conclusions

and clinical relevance In the veterinary literature, there is no agreement on the precise volume of local anaesthetic solution that should be used to achieve intraconal retrobulbar anaesthesia in dogs. Here we suggest a formula to calculate the retrobulbar cone volume and, accordingly, the injection volume of local anaesthetic solution for effective retrobulbar anaesthesia.

中文翻译：

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基于计算机断层扫描的眼科麻醉犬球后锥体体积评估方法

客观的

开发用于计算不同颅骨形态犬球后麻醉局麻药体积的综合公式。

学习规划

回顾性队列成像研究。

动物

2009 年 1 月至 2017 年 12 月期间收集的 188 只不同品种狗的头骨计算机断层扫描 (CT) 图像。

方法

对眼眶和相邻结构的解剖完整性、主诉、临床体征和 CT 结果进行了验证，以排除眼部异常。使用狗头骨的 CT 扫描计算了 376 只眼睛的球后锥体的体积。记录的其他数据包括颅骨的形态、体重、性别和狗的大小，所有这些都通过单变量和多变量线性回归模型与球后锥体体积的可能关联进行了匹配。线性回归模型的结果表示为具有相应 95% 置信区间 (95% CI) 的估计 Beta 系数。

结果

使用单变量分析，球后锥体体积与体重和男性呈正相关。此外，短头和长头犬的球后锥体积比中头犬更大，而性别不再与球后锥体积显着相关。在多变量分析，考虑模型中的所有变量时，重量成为最强的预测因子（贝塔系数：0.062毫升千克^-1，95％CI：0.056-0.067毫升千克^-1，p <0.001）。

结论

和临床相关性在兽医文献中，对于用于实现犬球内球后麻醉的局麻药溶液的精确体积没有一致意见。在这里，我们提出了一个公式来计算球后锥体体积，从而计算有效球后麻醉的局部麻醉溶液的注射量。