Benjamin J. Walker

Pediatric Regional Anesthesia Network (PRAN): a multi-institutional study of the use and incidence of complications of pediatric regional anesthesia.

BACKGROUND: Regional anesthesia is increasingly used in pediatric patients to provide postoperative analgesia and to supplement intraoperative anesthesia. The Pediatric Regional Anesthesia Network was formed to obtain highly audited data on practice patterns and complications and to facilitate collaborative research in regional anesthetic techniques in infants and children. METHODS: We constructed a centralized database to collect detailed prospective data on all regional anesthetics performed by anesthesiologists at the participating centers. Data were uploaded via a secure Internet connection to a central server. Data were rigorously audited for accuracy and errors were corrected. All anesthetic records were scrutinized to ensure that every block that was performed was captured in the database. Intraoperative and postoperative complications were tracked until their resolution. Blocks were categorized by type and as single-injection or catheter (continuous) blocks. RESULTS: A total of 14,917 regional blocks, performed on 13,725 patients, were accrued from April 1, 2007 through March 31, 2010. There were no deaths or complications with sequelae lasting >3 months (95% CI 0–2:10,000). Single-injection blocks had fewer adverse events than continuous blocks, although the most frequent events (33% of all events) in the latter group were catheter-related problems. Ninety-five percent of blocks were placed while patients were under general anesthesia. Single-injection caudal blocks were the most frequently performed (40%), but peripheral nerve blocks were also frequently used (35%), possibly driven by the widespread use of ultrasound (83% of upper extremity and 69% of lower extremity blocks). CONCLUSIONS: Regional anesthesia in children as commonly performed in the United States has a very low rate of complications, comparable to that seen in the large multicenter European studies. Ultrasound may be increasing the use of peripheral nerve blocks. Multicenter collaborative networks such as the Pediatric Regional Anesthesia Network can facilitate the collection of detailed prospective data for research and quality improvement.

Asleep versus awake: does it matter?: Pediatric regional block complications by patient state: a report from the Pediatric Regional Anesthesia Network.

Background and Objectives The impact of the patient state at time of placement of regional blocks on the risk of complications is unknown. Current opinion is based almost entirely on case reports, despite considerable interest in the question. Analyzing more than 50,000 pediatric regional anesthesia blocks from an observational prospective database, we determined the rate of adverse events in relation to the patient’s state at the time of block placement. Primary outcomes considered were postoperative neurologic symptoms (PONSs) and local anesthetic systemic toxicity (LAST). Secondary outcome was extended hospital stay due to a block complication. Methods The Pediatric Regional Anesthesia Network is a multi-institutional research consortium that was created with an emphasis on rigorous, prospective, and complete data collection including a data validation and audit process. For the purpose of the analysis, blocks were divided in major groups by single injection versus continuous and by block location. Rates were determined in aggregate for these groups and classified further based on the patient’s state (general anesthesia [GA] without neuromuscular blockade [NMB], GA with NMB, sedated, and awake) at the time of block placement. Results Postoperative neurological symptoms occurred at a rate of 0.93/1000 (confidence interval [CI], 0.7–1.2) under GA and 6.82/1000 (CI, 4.2–10.5) in sedated and awake patients. The only occurrence of PONSs lasting longer than 6 months (PONSs-L) was a small sensory deficit in a sedated patient (0.019/1000 [CI, 0–0.1] for all, 0.48/1000 [CI, 0.1–2.7] for sedated patients). There were no cases of paralysis. There were 5 cases of LAST or 0.09/1000 (CI, 0.03–0.21). The incidence of LAST in patients under GA (both with and without NMB) was 0.08/1000 (CI, 0.02–0.2) and 0.34/1000 (CI, 0–1.9) in awake/sedated patients. Extended hospital stays were described 18 times (0.33/1000 [CI, 0.2–0.53]). The rate for patients under GA without NMB was 0.29/1000 (CI, 0.13–0.48); GA with NMB, 0.29/1000 (CI, 0.06–0.84); sedated, 1.47/1000 (CI, 0.3–4.3); and awake, 1.15/1000 (CI, 0.02–6.4). Conclusions The placement of regional anesthetic blocks in pediatric patients under GA is as safe as placement in sedated and awake children. Our results provide the first prospective evidence for the pediatric anesthesia community that the practice of placing blocks in anesthetized patients should be considered safe and should remain the prevailing standard of care. Prohibitive recommendations based on anecdote and case reports cannot be supported.

Evolving compartment syndrome not masked by a continuous peripheral nerve block: evidence-based case management.

Abstract Compartment syndrome is a potentially devastating complication of many orthopedic surgeries. Whether regional anesthesia can delay the diagnosis of compartment syndrome remains a subject of debate. Previous case reports have described compartment syndrome primarily in the setting of an epidural infusion, but also following single-injection peripheral nerve blocks. A case of evolving compartment syndrome in an ambulatory setting that was not masked by a continuous peripheral nerve block is presented, followed by a discussion of the literature pertaining specifically to peripheral nerve blockade and the diagnosis of compartment syndrome. Diagnosis depends on close postoperative monitoring of analgesic use and pain trends, and patients with ambulatory catheters require thorough education about compartment syndrome so they can be evaluated in a timely manner. The current literature on compartment syndrome diagnosis and regional anesthesia is limited to case reports and expert opinion, making evidence-based recommendations difficult.

Peripheral nerve catheters in children: an analysis of safety and practice patterns from the pediatric regional anesthesia network (PRAN)

BACKGROUND Peripheral nerve catheters (PNCs) are used with increasing frequency in children. Although adult studies have demonstrated safety with this technique, there have been few safety studies in children. The main objective of the current investigation was to examine the incidence of PNC complications in children undergoing surgery. METHODS This is an observational, multi-institutional study using the Pediatric Regional Anesthesia Network (PRAN) database. Data pertaining to PNCs were entered prospectively into a secure, online database by each participating centre. Patient characteristics, anatomic location, localization techniques, medications used, and complications were recorded for each catheter. All complications and any sequelae were followed until resolution. RESULTS There were 2074 PNCs included in the study. 251 adverse events and complications were recorded, resulting in an overall incidence (95% CI) of complications of 12.1% (10.7-13.5%). The most common complications were catheter malfunction, block failure, infection, and vascular puncture. There were no reports of persistent neurologic problems, serious infection, or local anaesthetic systemic toxicity, resulting in an estimated incidence (95% CI) of 0.04% (0.001-0.2%). Patients who developed an infection had used the catheters for a greater number of days, median (IQR) of 4.5 (3-7) days compared with 3 (1-3) days in the patients who did not develop an infection, P<0.0001. CONCLUSIONS Our data support the safety of placing PNCs in children, with adverse event rates similar to adult studies. Catheter problems are common, yet minor, in severity.

Ultrasound‐guided rectus sheath block or wound infiltration in children: a randomized blinded study of analgesia and bupivacaine absorption

Rectus sheath block can provide analgesia following umbilical hernia repair. However, conflicting reports on its analgesic effectiveness exist. No study has investigated plasma local anesthetic concentration following ultrasound‐guided rectus sheath block (USGRSB) in children.

Altered neurovascular control of the resting circulation in human metabolic syndrome

•  Young healthy adults exhibit a balance between muscle sympathetic nerve activity (MSNA) and α‐adrenergic‐mediated vasoconstriction such that those with higher MSNA exhibit lower vascular‐adrenergic responsiveness. •  In contrast to healthy adults, the balance between MSNA and α1‐adrenergic‐mediated vasoconstriction is lost in adults with metabolic syndrome. In addition, adults with metabolic syndrome exhibit increased α2‐adrenergic responsiveness. •  This study uncovered some of the earliest sympathetic–haemodynamic changes in the progression from metabolic syndrome to cardiovascular disease and diabetes. •  Considering metabolic syndrome subjects were relatively young and free of overt cardiovascular disease, it is reasonable to speculate as the disease progresses the observed uncoupling between MSNA and α‐adrenergic responsiveness may lead to reduced whole‐limb blood flow, altered blood flow distribution, reduced glucose delivery and/or increased hypertension severity.

Predicting lumbar plexus depth in children and adolescents.

BACKGROUND:Lumbar plexus block provides effective analgesia for hip, thigh, and knee surgery. A simple measurement that accurately predicts lumbar plexus depth would be invaluable for clinicians performing this block in children, in whom plexus depth varies with age. METHODS:Surface anatomy measurements were taken on children having lower extremity surgery and lumbar plexus block. All blocks were placed under general anesthesia using peripheral nerve stimulation. The distance from the posterior superior iliac spine (PSIS) to the intercristal line (ICL), i.e., PSIS-ICL distance, and from midline to the intersection of a perpendicular line drawn from the PSIS and the ICL were measured. Lumbar plexus depth was recorded at the point at which maximum quadriceps stimulation was elicited using the lowest current output. Linear regression was used to explore the least squares line of best fit for each measure. RESULTS:Measurements were made on 350 consecutive patients aged 1 month to 24 years. A very strong linear relationship between lumbar plexus depth and PSIS-ICL distance was noted. The median (interquartile range) absolute difference between observed lumbar plexus depth and that predicted by PSIS-ICL distance was 2 mm (1–5 mm), 95% CI for median = 1.36 to 2.64. Ninety-two percent of patients (95% CI, 88.7%–94.6%) had lumbar plexus depths within ±10 mm of the predicted depth. The strongest correlation to lumbar plexus depth was found with PSIS-ICL distance (R2 = 0.89, P < 0.0001). Weaker correlations were found for weight, height, body mass index, midline-PSIS line distance, and age. CONCLUSION:PSIS-ICL distance provides an accurate, patient-specific predictor for lumbar plexus depth in children over a wide range of age and body habitus. The strong linear relationship obviates the need for complex calculations. This measurement can be used as a guide for ultrasound location, to choose an appropriate needle length, and may reduce complications associated with this block.

Greater Beta-Adrenergic Receptor Mediated Vasodilation in Women Using Oral Contraceptives

Background: β-adrenergic receptors play an important role in mitigating the pressor effects of sympathetic nervous system activity in young women. Based on recent data showing oral contraceptive use in women abolishes the relationship between muscle sympathetic nervous system activity and blood pressure, we hypothesized forearm blood flow responses to a β-adrenergic receptor agonist would be greater in young women currently using oral contraceptives (OC+, n = 13) when compared to those not using oral contraceptives (OC–, n = 10). Methods: Women (18–35 years) were studied during the early follicular phase of the menstrual cycle (days 1–5) or placebo phase of oral contraceptive use. Forearm blood flow (FBF, Doppler ultrasound) and mean arterial blood pressure (MAP, brachial arterial catheter) were measured at baseline and during graded brachial artery infusion of the β-adrenergic receptor agonist, Isoproterenol (ISO), as well as Acetylcholine (ACH, endothelium-dependent vasodilation) and Nitroprusside (NTP, endothelium-independent vasodilation). Forearm vascular conductance was calculated (FVC = FBF/MAP, ml/min/100 mmHg) and the rise in FVC from baseline during infusion quantified vasodilation (ΔFVC = FVCinfusion − FVCbaseline). Results: ISO increased FVC in both groups (p < 0.01) and ISO-mediated ΔFVC was greater in OC+ compared to OC– (Main effect of group, p = 0.02). Expressing data as FVC and FBF resulted in similar conclusions. FVC responses to both ACH and NTP were also greater in OC+ compared to OC–. Conclusions: These data are the first to demonstrate greater β-adrenergic receptor-mediated vasodilation in the forearm of women currently using oral contraceptives (placebo phase) when compared to those not using oral contraceptives (early follicular phase), and suggest oral contraceptive use influences neurovascular control.

Preserved Microvascular Endothelial Function in Young, Obese Adults with Functional Loss of Nitric Oxide Signaling

Data indicate endothelium-dependent dilation (EDD) may be preserved in the skeletal muscle microcirculation of young, obese adults. Preserved EDD might be mediated by compensatory mechanisms, impeding insight into preclinical vascular dysfunction. We aimed to determine the functional roles of nitric oxide synthase (NOS) and cyclooxygenase (COX) toward EDD in younger obese adults. We first hypothesized EDD would be preserved in young, obese adults. Further, we hypothesized a reduced contribution of NOS in young, obese adults would be replaced by increased COX signaling. Microvascular EDD was assessed with Doppler ultrasound and brachial artery infusion of acetylcholine (ACh) in younger (27 ± 1 year) obese (n = 29) and lean (n = 46) humans. Individual and combined contributions of NOS and COX were examined with intra-arterial infusions of l-NMMA and ketorolac, respectively. Vasodilation was quantified as an increase in forearm vascular conductance (ΔFVC). Arterial endothelial cell biopsies were analyzed for protein expression of endothelial nitric oxide synthase (eNOS). ΔFVC to ACh was similar between groups. After l-NMMA, ΔFVC to ACh was greater in obese adults (p < 0.05). There were no group differences in ΔFVC to ACh with ketorolac. With combined NOS-COX inhibition, ΔFVC was greater in obese adults at the intermediate dose of ACh. Surprisingly, arterial endothelial cell eNOS and phosphorylated eNOS were similar between groups. Younger obese adults exhibit preserved EDD and eNOS expression despite functional dissociation of NOS-mediated vasodilation and similar COX signaling. Compensatory NOS- and COX-independent vasodilatory mechanisms conceal reduced NOS contributions in otherwise healthy obese adults early in life, which may contribute to vascular dysfunction.

Spinal epidural hematoma following a thoracic epidural in a child with sickle cell disease

Acute liver dysfunction in the perioperative period may increase the risk of epidural hematoma in a patient with a neuraxial catheter. Coagulation testing needs to be carefully monitored in these patients. An epidural hematoma should be ruled out urgently by CT or MRI in cases of a persistent motor block.