To the Editor:
A recent letter described sacrococcygeal ligament bulging as a sign of successful needle placement in caudal block . This appears useful for older children; however, it could be dangerous in small infants. The recommended 3-mL anesthetic dose may represent the entire anesthetic volume used in these patients. Due to the increased likelihood of intraosseous, intravenous, or subarachnoid injection in children, most authors strongly advocate test dosing . Do smaller boluses produce "bulging" in infants? Also, sacrococcygeal anatomy of infants is more uniform , and "decoy hiatuses" are usually not entered. A method that many have successfully used to address these concerns is performing caudal block with a 22-gauge intravenous cannula. When the "pop" is felt indicating penetration of the ligament, the needle is held and the cannula advanced. A T-connector and syringe are attached, allowing movement while cannula position remains stable. After aspiration, subcutaneous air can be palpated and a test dose of anesthetic with epinephrine can be given. In this manner, subcutaneous, intrathecal, or intravascular injection due to inadvertent needle movement can be avoided during test dosing and anesthetic administration. Also, the soft cannula may reduce injury to underlying structures. This technique may permit safer and more accurate administration of caudal blocks.
Howard B. Gutstein, MD
Section of Pediatric Anesthesiology, Mental Health Research Institute, The University of Michigan, Ann Arbor, MI 48109
1. Schwartz RE, Stayer SA, Pasqariello CA. An additional sign of correct needle placement when performing a caudal block in pediatric patients [letter]. Anesth Analg 1994;79:818.
2. Kester Brown TC, Schulte-Steinberg O. Neural blockade for pediatric surgery. In: Cousins MJ, Bridenbaugh PO, eds. Neural blockade. 2nd ed. Philadelphia: JB Lippincott, 1988:675-8.
3. Willis RJ. Caudal epidural blockade. In: Cousins MJ, Bridenbaugh PO, eds. Neural blockade. 2nd ed. Philadelphia: JB Lippincott, 1988:361-83.