Correlation Between Injected Volume and Cranial Spread in Broad-Aged Pediatric Caudal Anesthesia: A Retrospective Ultrasound-Guided Study

Feng-Fang Tsai,1 Ming-Han Hsieh,2 Hsing-Hao Huang,1 Chih-Min Liu1 1Department of Anesthesiology, National Taiwan University Hospital, Taipei, Taiwan, Republic of China; 2Department of Anesthesiology, Taipei City Hospital Ho-Ping Branch, Taipei, Taiwan, Republic of ChinaCorrespondence: Chih-Min Liu, Department of Anesthesiology, National Taiwan University Hospital, No. 7, Zhongshan S. Road, Zhongzheng District, Taipei, 10002, Taiwan, Republic of China, Tel +886 2 23123456 #62158, Email [email protected]: Caudal block remains a standard regional anesthesia technique for pediatric lower abdominal and lower limb surgeries. The conventional weight-based Armitage formula does not consider patient body habitus, which can lead to under- or over-dosing—especially in lean or obese children. Ultrasound guidance permits visualization of epidural spread and may facilitate individualized dosing.Patients and Methods: In this retrospective single-center study, anesthetic records of 25 pediatric patients (age 10– 106 months) undergoing ultrasound-guided caudal blocks for lower abdominal or lower extremity surgery were analyzed. Volumes of 0.25% levobupivacaine required to achieve cranial spread to vertebral levels S1, L2 and L1 were recorded. Univariate and multivariate linear regression models, incorporating weight, height, age, and BMI, were compared using adjusted R2, mean squared error (MSE), Akaike information criterion (AIC), and Bayesian information criterion (BIC) to determine the most predictive dosing formulae.Results: Univariate regression revealed injected volume correlated strongest with weight: for S1 spread, volume = 0.1458 × weight (kg) (p = 0.006); for L2 spread, volume = 0.4898 × weight (kg) (p = 0.0079). The optimal multivariate model for S1-level spread combined weight and height: Volume (mL) = 0.1741 × weight (kg) − 0.0234 × height (cm) (adjusted R2 = 0.1369; lowest AIC/BIC). For L2-level spread, a weight-only model (volume = 0.5339 × weight [kg]) provided the best fit (adjusted R2 = 0.2112). Both models predicted lower volumes than the traditional Armitage guideline, reducing the likelihood of excessive cephalad spread.Conclusion: In pediatric caudal anesthesia, a dosing formula that uses both weight and height improves prediction of the volume required for S1-level blocks, whereas a weight-based formula is adequate for L2-level spread. Real-time ultrasound guidance enhances procedural accuracy and safety by confirming epidural spread and detecting anatomical variation. These data support development of an individualized dosing nomogram for pediatric caudal anesthesia.Keywords: pediatric, general anesthesia, caudal block, ultrasound