'Kiddie caudal' anesthesia seems safe, but still more to learn

The database study reported a low overall complication rate, and no serious complications, in a very large series of caudal nerve blocks. "However, there are reasons to be cautious about interpretation of the data," according to the editorial by Drs Karen R. Boretsky and James A. DiNardo of Boston Children's Hospital.

Study Isn't the Last Word on Caudal Nerve Block in Children

In caudal block, a small dose of local anesthetic is injected into the base of the spine to numb feeling in the lower body. It is usually added to general anesthesia in infants, with the aim of controlling pain after surgery while reducing the required dose of general anesthetic.

Dr Santhanam Suresh and colleagues of Northwestern University, Chicago, assessed the safety of surgery with "kiddie caudal" anesthesia in 18,650 children, average age 14 months. The study used data from the Pediatric Regional Anesthesia Network (PRAN) -- a centralized database collecting detailed information on regional anesthesia techniques in children. The study reported a complication rate of less than two percent, with no serious or permanent complications. The study, published online in November, appears in the January print issue of Anesthesia & Analgesia.

In their accompanying editorial, Drs Boretsky and DiNardo raise some methodological concerns -- particularly related to the use of the PRAN data. Like other large databases, PRAN lacks many key details on the patients' characteristics and the treatments they receive. That makes it difficult to evaluate some of the variations observed in the study, and to determine the true safety of the caudal nerve block procedure.

For example, the study found significant variations in local anesthetic dose. Dr Suresh and coauthors suggest that about one-fourth of children receiving "potentially toxic" doses -- particularly younger children.

But the variations in dose may be related to other factors, such as differences in the surgical procedures performed, according to Drs Boretsky and DiNardo. They write, "[A]lthough it is true that proportionally higher doses were given in younger patients, the reason and significance of this finding are unclear."

In addition, Drs Boretsky and DiNardo question the study's definition of "potentially unsafe doses." They note that the only two children with systemic (generalized) toxic effects received doses well within standard guidelines. They also point out issues related to unexplained variations in dosing with different anesthetics (ropivacaine versus bupivacaine) and the detection block failure -- the most common complication.

Studies using large databases such as PRAN are valuable. By combining data from many different hospitals, they can detect infrequent complications and adverse effects that may not occur in smaller studies. But such studies may also be "overpowered," introducing certain types of statistical errors. Very large database studies may find differences that are "statistically significant," but too small to be clinically significant.

While the study adds to the evidence on the overall good safety record of caudal nerve block in infants and young children, further research is needed to address some of the unanswered questions that remain, Drs Boretsky and DiNardo believe. They conclude, "Despite the lack of evidence for complications, the article is not a carte blanche on the safety of the kiddie caudal."