The median (95% range) for the local anesthetic dose per weight for caudal blocks was 1.4 mg (0.78–2.51 mg) of bupivacaine equivalents/kg representing a large variation in clinical practice. There was a direct linear relationship between the total local anesthetic dose and patients’ weights; however, subjects’ weight was not sufficient to explain much of the variability in dose (Fig. 1). Variation in the local anesthetic dose was not better explained by variations in age of subjects (slope of regression line 0.32 ± 0.00; goodness of fit r 2 = 0.41 and slope significantly different from 0, P < 0.0001. Examination of a residual plot demonstrated a fairly random pattern).
The median (IQR) local anesthetic dose per weight was larger when epinephrine was used as a block adjunct compared to when no epinephrine was used, 1.4 mg (1.2–1.6 mg) and 1.3 mg (1.2–1.6 mg) of bupivacaine equivalents/kg, respectively (P < 0.001). After adjusting for different local anesthetic potencies, subjects who had a caudal block with ropivacaine received a greater dose of local anesthetics than those who had a caudal block with bupivacaine, median (IQR) of 1.66 mg (1.25–2.31 mg) and 1.34 mg (1.13–1.4 mg) of bupivacaine/kg equivalents, respectively, P < 0.001.
Four thousand four hundred-six of 17,867 (24.6%; 95% CI, 24%–25.2%) subjects received larger doses than 2 mg of bupivacaine equivalents/kg that potentially could have been unsafe. When a less conservative limit of 2.5 mg/kg dose of bupivacaine was evaluated, 968 of 17,867 (5.4%; 95% CI, 5.0%–5.4%) subjects received potentially toxic doses. Subjects who received doses larger than the maximal safe local anesthetic doses were younger than subjects who did not receive potentially unsafe doses, 11 (6–20) months and 15 (7–36) months, respectively (P < 0.001).
The most important finding of the current investigation was the low rate of complications when the caudal block was performed in pediatric patients undergoing surgical procedures. The upper incidence limit of severe complications such as cardiac arrest and seizure was 0.02%. More importantly, no cases of long-term sequelae were detected in any of the 18,650 patients in this cohort. Taken together, our results suggest that caudal block is a safe regional anesthesia technique when performed in children undergoing surgery.
Our results are clinically important since reports of complications associated with the performance of caudal block in the literature have questioned its safety in children.22–24 In addition, prior safety studies that specifically examined caudal block were limited by a small number of patients and the evaluation of only a single center.25,26 In Europe, a large study on the safety of several regional anesthesia techniques in children demonstrated a low incidence of complications for 8493 caudal blocks.14 Our study establishes the safety of caudal block in children across multiple pediatric hospitals in the United States. The current study is, to the best of our knowledge, the largest study to demonstrate safety of a single regional anesthesia technique in children.
Another important finding of the current investigation was the detection of a large variation in local anesthetic dose used in caudal blocks (IQR, 1.23 mg of bupivacaine/kg to 1.98 mg of bupivacaine/kg). In addition, the dose variation was not largely explained by changes in weight of the subjects R2 (95% CI) = 0.5 (0.48 to 0.52). Current data suggest that approximately 25% of patients undergoing a caudal block receive a local anesthetic dose that has the potential to cause local anesthetic toxicity.27–31 Younger children seem to be at greatest risk for receiving a toxic dose. Quality improvement projects should be implemented across different institutions to detect and avoid unsafe local anesthetic doses when caudal block is performed in pediatric patients.
We did not detect a beneficial role in the use of ultrasound to minimize complications of caudal block in children. It was also interesting that the use of ultrasound decreased across the years. The use of ultrasound assistance has been shown to minimize complications and/or improve efficacy of peripheral regional anesthesia techniques in adults when compared to nerve stimulation.32–35 Although the current data do not suggest that ultrasound improves safety of caudal block, future studies examining the role of ultrasound guidance on the efficacy of caudal blocks are still needed.
The efficacy of caudal block to minimize postoperative pain in specific surgical procedures has yet to be established.2 In addition, optimal dose regimens also need to be determined to help reduce the large variation in clinical practice we observed. Given the safety of caudal blocks in children demonstrated by the current analysis, the performance of randomized controlled trials is justified not only to establish procedure-specific efficacy but also to detect optimal local anesthetic dose regimens.
Our study should only be interpreted within the context of its limitations. We evaluated the safety of caudal block but did not examine its efficacy. Since the PRAN database does not capture type of surgical procedure, we were not able to investigate if specific types of surgical procedures carry a greater risk for patients to receive potentially toxic doses of local anesthetics or to have postoperative complications. Similar to other national quality improvement programs, site-specific contributions were not available and could not be incorporated into the analysis.36–39
In summary, we established a safety profile for caudal block in children using data from >20 pediatric hospitals in the United States in 18,650 pediatric patients. However, we detected a large variation in clinical practice regarding dose of local anesthetics for caudal block that may lead to local anesthetic toxicity. Safety concerns should not be a barrier to the development of randomized trials in order to test the efficacy of caudal block on analgesic outcomes in children pending the appropriate selection of local anesthetic doses.
We would like to acknowledge the PRAN steering committee members: Drs. Martin, Polaner, Krane, Bosenberg, Walker, and Taenzer for their dedication in conceptually forming the PRAN database, all sites that have contributed data to the consortium, and Christie Wolf from Axio Research whose contributions to the database are invaluable.
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