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The Safety and Effectiveness of Continuous Peripheral Nerve Blockade in Children

2014; Lippincott Williams & Wilkins; Volume: 118; Issue: 3 Linguagem: Inglês

10.1213/ane.0000000000000110

1526-7598

Elliot J. Krane, David M. Polaner,

Pediatric Pain Management Techniques

Regional anesthesia and continuous peripheral nerve blocks are performed with increasing frequency in adults. The addition of ultrasound technology to the toolbox of the anesthesiologist has not only dramatically increased the number of regional blocks performed, but has increased their safety and effectiveness both by improving the accuracy of needle and catheter placement and by allowing reduction in doses of local anesthetics in many instances.1,2 The surge in interest and skill in regional anesthetic techniques has been mirrored in pediatric anesthesia practices around the world. Because children are generally, by their nature, fearful of needle insertions and uncooperative with procedures unless they are sedated or anesthetized, it has become the standard of care to perform single injection and continuous central and peripheral nerve blocks in sedated or anesthetized children, a practice generally not considered to be the standard of care for adult patients. Here lies a controversy much discussed in regional anesthesia circles and societies, and the resolution of this controversy depends entirely on an accurate estimate of the magnitude of risk to the patient, weighed against probable success rates and outcome benefits, 3 metrics that are not well defined at the present time. The authors Gurnaney et al.,3 working at the Children’s Hospital of Philadelphia (CHOP), have collated data of >1000 cases of continuous peripheral nerve blocks to begin to answer these questions. Their methodology was to retrospectively review their departmental regional anesthesia database, which included demographic information, methodology for block placement including pharmacologic agents used, and the results of daily telephone calls made by pain service personnel to patients who were discharged home with indwelling catheters. This large retrospective series did not identify any cases of long-term neurologic deficit and concluded that the use of peripheral nerve infusion catheters resulted in reduction of opioid use by the patients or a reduction of opioid administration by their parents or caretakers. A study of this nature and size inevitably invites comparison to the 3 previously published large studies of regional anesthetics in children,4–6 both regarding the results and the methodology. One significant difference is that all of the data in the Gurnaney et al.3 study came from a single institution, CHOP. To some degree, this results in uniformity of data collection and of care systems outside the control of the anesthesiologist, as well as practice patterns. However, that same data homogeneity reduces the applicability of the findings to a broader range of settings. By contrast, both French-Language Society of Paediatric Anaesthesiologists (ADARPEF) studies and the more recent Pediatric Regional Anesthesia Network (PRAN) study involved a wide range of both children’s hospitals and large general hospitals with significant pediatric expertise. There is a second, but vital, difference in the methodologies of these studies. Both the ADARPEF and PRAN studies were designed prospectively to acquire specific data elements with defined outcome parameters in mind. The investigators specified, in advance, what outcome measures would be studied and how those data would be collected and analyzed. Data veracity is still another distinction between the PRAN methodology and the CHOP study. The PRAN database is notable for a rigorous post hoc auditing system, ensuring data are accurate both in detail and in denominator. The CHOP data are retrospective, and while cross-correlated between the departmental regional anesthetic database and their pain service database to ensure accuracy, we are not told by the authors if any data errors were detected and, if so, how they were resolved. The CHOP data presented in this article are therefore not easily interpreted. For example, the data included a measure of supplemental analgesic used postoperatively. It is evident that the block alone, despite stated efficacy, sufficed as an analgesic modality without supplementation in only a minority of children, about 14%, which flies in the face of a stated 1.9% “failure rate.” Does not the need to resort to opioid analgesics constitute a failure of the regional anesthetic? And, if not, the authors do not tell us how they measured success and defined failure. Catheter dislodgement, which was identified as a major cause of premature technique failure in the PRAN database, was reported very infrequently in this study. Only about 1% of catheters were reported to have been prematurely dislodged or became nonfunctional, one-tenth the number in the prospective multi-institution data from PRAN. A recent prospective study from Marhofer et al.7 also found a much higher rate of peripheral nerve catheter dislodgement (5% for interscalene catheters and 25% for femoral nerve catheters as assessed by ultrasound). Is it possible that more catheters in the CHOP group were displaced than was recognized by the parents of the patients? Could this have contributed to the frequent use of opioid supplementation? Finally, in nearly 1500 cases of continuous peripheral nerve infusions in this report, there were 3 instances of a symptom suggestive of local anesthetic toxicity noted, a metallic taste in the mouth, despite infusion rates that were well below those expected to result in toxicity. Does this suggest that absorption of local anesthetic from these peripheral sites might be greater than we have previously suspected? Without more detailed real-time clinical observation and blood toxicology, it is impossible to determine whether these examples truly represented toxicity, or, perhaps more likely, were nocebo responses in children who may have been told to be on alert for metallic tastes in the mouth. The plural of anecdote, it is said, is not data, and this is true even if the anecdotes measure in the hundreds. Large retrospective analyses of data such as reported by Gurnaney et al.3 are impressive in their scope and for the sheer effort expended and may provide information that is either reassuring or troubling. In either case, the results do not answer many questions because retrospective series fail to definitively establish risk and benefit of treatments, serving rather to signal areas for concern and suggest prospective data collections that avoid the pitfalls of retrospective analyses: a lack of rigorous definition of outcomes, a lack of standardization of treatment variables, biases or inexperience of observers, bias introduced by underreporting of adverse outcomes, and incomplete datasets. Real-time observation and recording of data that are predefined and audited post hoc are and will remain the “gold standard” for clinical research. Nevertheless, the data of Gurnaney et al.,3 taken with the ADARPEF and PRAN databases, are reassuring and lend further credence to the belief that placement of peripheral nerve blocks in sedated or anesthetized children and continuous perineural analgesia have a very low incidence of serious complications, and with well-designed systems of follow-up and care are valuable modalities for postoperative analgesia in pediatric practice. DISCLOSURES Name: Elliot J. Krane, MD. Contribution: This author helped write the manuscript. Attestation: This author approved the final manuscript. Name: David Polaner, MD. Contribution: This author helped write the manuscript. Attestation: This author approved the final manuscript. This manuscript was handled by: Peter J. Davis, MD.