A survey of practice in the anesthetic management of adolescent idiopathic scoliosis spine fusion by the North American Pediatric Spine Anesthesiologists Collaborative

BACKGROUND

Adolescent Idiopathic Scoliosis (AIS) affects 2%-4% of the general pediatric population. While surgical correction remains one of the most common orthopedic procedures performed in pediatrics, limited consensus exists on the perioperative anesthetic management.

AIMS

To examine the current state of anesthetic management of typical AIS spine fusions at institutions which have a dedicated pediatric orthopedic spine surgeon.

METHODS

A web-based survey was sent to all members of the North American Pediatric Spine Anesthesiologists (NAPSA) Collaborative. This group included 34 anesthesiologists at 19 different institutions, each of whom has a Harms Study Group surgeon performing spine fusions at their hospital.

RESULTS

Thirty-one of 34 (91.2%) anesthesiologists completed the survey, with a missing response rate from 0% to 16.1% depending on the question. Most anesthesia practices (77.4%; 95% confidence interval [CI], 67.7-93.4) do not have patients come for a preoperative visit prior to the day of surgery. Intravenous induction was the preferred method (74.2%; 95% CI 61.3-89.9), with the majority utilizing two peripheral IVs (93.5%; 95% CI 90.3-100) and an arterial line (100%; 95% CI 88.8-100). Paralytic administration for intubation and/or exposure was divided (51.6% rocuronium/vecuronium, 45.2% no paralytic, and 3.2% succinylcholine) amongst respondents. While tranexamic acid was consistently utilized for reducing blood loss, dosing regimens varied. When faced with neuromonitoring signal issues, 67.7% employ a formal protocol. Most anesthesiologists (93.5%; 95% CI 78.6-99.2) extubate immediately postoperatively with patients admitted to an inpatient floor bed (77.4%; 95% CI 67.7-93.3).

CONCLUSION

Most anesthesiologists (87.1%; 95% CI 80.6-99.9) report the use of some form of an anesthesia-based protocol for AIS fusions, but our survey results show there is considerable variation in all aspects of perioperative care. Areas of agreement on management comprise the typical vascular access required, utilization of tranexamic acid, immediate extubation, and disposition to a floor bed. By recognizing the diversity of anesthetic care, we can develop areas of research and improve the perioperative management of AIS.

One-year Results of Minimally Invasive Sutured Fixation of the Slipped Ribs in the Pediatric Population

PURPOSE

Costal cartilage resection with or without rib resection is the gold standard surgery for slipping rib syndrome. Minimally invasive restoration of normal anatomy via nonabsorbable sutures has been described in the adult population with encouraging results. We sought to assess the efficacy of minimally invasive sutured fixation of the hypermobile rib in the pediatric population.

METHODS

A retrospective review was performed at Mayo Clinic involving 31 pediatric patients diagnosed with slipped rib syndrome. Minimally invasive sutured open reduction internal fixation was performed between 2020 and 2022. The standardized Örebro Musculoskeletal Pain Screening Questionnaire was given at dedicated time points pre- and post-operatively to assess efficacy. Significance was determined via the Wilcoxon rank sum test.

RESULTS

SRS was diagnosed clinically in 31 patients (24 females, 7 males, 1220 years-old). Symptoms were present for an average of 18.9 months and patients had seen an average of 4.7 specialists. Traumatic causes were identified in three patients and eight patients had hypermobility. At one month follow up, there were no surgical complications and patients reported significantly less pain (p < 0.001). Preoperative analgesics reduced by 80%. Ultimately, seven patients underwent a second operation; three patients underwent a third operation; one patient underwent five total operations. Recurrent pain was reported in six patients. Only nine patients followed-up at 1-year post-operation.

CONCLUSION

Pediatric patients with SRS demonstrated an early positive response to suture fixation without costal cartilage excision. Reoperation and recurrent pain, however, remain significant in this population.

LEVEL OF EVIDENCE

Level IV.

TYPE OF STUDY

Case series with no comparison group.

Patient and Process Outcomes Among Pediatric Patients Undergoing Appendectomy During the COVID-19 Pandemic - an International Retrospective Cohort study

BACKGROUND

COVID-19 forced healthcare systems to make unprecedented changes in clinical care processes. We hypothesized that the COVID-19 pandemic adversely impacted timely access to care, perioperative processes, and clinical outcomes for pediatric patients undergoing primary appendectomy.

METHODS

We conducted a retrospective, international, multicenter study using matched cohorts within participating centers of the international PEdiatric Anesthesia COVID-19 Collaborative (PEACOC). Patients < 18 years old were matched using age, ASA-PS status, and sex. The primary outcome was the difference in hospital length of stay of patients undergoing primary appendectomy during a 2-month period early in the COVID-19 pandemic (April-May 2020) compared to pre-pandemic (April-May 2019). Secondary outcomes included time to appendectomy and the incidence of complicated appendicitis.

RESULTS

3351 cases from 28 institutions were available with 1684 cases in the pre-pandemic cohort matched to 1618 in the pandemic cohort. Hospital length of stay was statistically significantly different between the two groups: 29 hours (IQR: 18, 67) in the pandemic cohort versus 28 hours (IQR: 18, 79) in the pre-pandemic cohort (adjusted coefficient, 1; 95% CI 0.39 to 1.61, P<0.001), but this difference was small. Eight centers demonstrated a statistically significantly longer hospital length of stay in the pandemic period compared to the pre-pandemic period, while 13 were shorter and 7 did not observe a statistically significant difference. During the pandemic period, there was a greater occurrence of complicated appendicitis, pre-pandemic 313 (18.6%) versus pandemic 389 (24.1%), absolute difference of 5.5% (adjusted OR, 1.32; [95% CI 1.1 to 1.59]; P=0.003). Preoperative SARS CoV-2 testing was associated with significantly longer time-to-appendectomy, 720 minutes (IQR: 430, 1112) with testing versus 414 minutes (IQR: 231, 770) without testing, adjusted coefficient, 306 minutes, (95% CI 241 to 371, P <0.001), and longer hospital length of stay, 31 hours (IQR: 20, 83) with testing versus 24 hours (IQR: 14, 68) without testing, adjusted coefficient, 7.0, (95% CI 2.7 to 11.3, P=0.002).

DISCUSSION

For children undergoing appendectomy, the COVID-19 pandemic did not significantly impact hospital length of stay.

Association Between Behavioral and Learning Outcomes and Single Exposures to Procedures Requiring General Anesthesia Before Age 3: Secondary Analysis of Data From Olmsted County, MN

BACKGROUND

Two prior population-based (children born in Olmsted County, MN), retrospective cohort studies both found that multiple exposures to anesthesia before age 3 were associated with a significant increase in the frequency of attention-deficit hyperactivity disorder (ADHD) and learning disabilities (LD) later in life. The primary purpose of this secondary analysis of these data was to test the hypothesis that a single exposure to anesthesia before age 3 was associated with an increased risk of ADHD. We also examined the association of single exposures with LD and the need for individualized educational plans as secondary outcomes.

METHODS

This analysis includes 5339 children who were unexposed to general anesthesia before age 3 (4876 born from 1976 to 1982 and 463 born from 1996 to 2000), and 1054 children who had a single exposure to anesthesia before age 3 (481 born from 1976 to 1982 and 573 born from 1996 to 2000). The primary outcome of interest was ADHD. Secondary outcomes included LD (reading, mathematics, and written language) and the need for individualized educational programs (speech/language and emotion/behavior). To compare the incidence of each outcome between those who were unexposed and singly exposed to anesthesia before the age of 3 years, an inverse probability of treatment weighted proportional hazards model was used.

RESULTS

For children not exposed to anesthesia, the estimated cumulative frequency (95% confidence interval [CI]) of ADHD at age 18 was 7.3% (95% CI, 6.5-8.1) and 13.0% (95% CI, 10.1-16.8) for the 1976-1982 and 1996-2000 cohorts, respectively. For children exposed to a single anesthetic before age 3, the cumulative frequency of ADHD was 8.1% (95% CI, 5.3-12.4) and 17.6% (95% CI, 14.0-21.9) for the 1976-1982 and 1996-2000 cohorts, respectively. In weighted analyses, single exposures were not significantly associated with an increased frequency of ADHD (hazard ratio [HR], 1.21; 95% CI, 0.91-1.60; P = .184). Single exposures were also not associated with an increased frequency of any LD (HR, 0.98; 95% CI, 0.78-1.23), or the need for individualized education plans.

CONCLUSIONS

This analysis did not find evidence that single exposures to procedures requiring general anesthesia, before age 3, are associated with an increased risk of developing ADHD, LD, or the need for individualized educational plans in later life.

Postoperative pain and psychological outcomes following minimally invasive pectus excavatum repair: A report from the Society for Pediatric Anesthesia Improvement Network

BACKGROUND

Minimally invasive repair of pectus excavatum (MIRPE) is associated with less tissue trauma; however, it may result in increased postoperative pain. Pain experience is a known risk factor for the development of posttraumatic stress symptoms, though there are little data on its relationship with long-term psychological outcomes following major surgery in pediatric patients.

AIMS

In this study, we examined the relationship between immediate postoperative pain and psychological outcomes at 2 weeks and three months after discharge in a cohort of pediatric patients who underwent MIRPE. We sought to determine whether immediate postoperative pain levels were associated with ongoing distress related to aspects of surgery at both time points. We were also interested in how psychological symptoms related to persistent pain concerns.

METHODS

Data on patients undergoing MIRPE across 14 institutions were collected as part of the Society for Pediatric Anesthesia Improvement Network (SPAIN). Patients were contacted at 2 weeks and three months following discharge to track pain levels and assess psychological distress using a self-report questionnaire. Patients were grouped into cohorts based on self-report of distress related to aspects of surgery, nonsurgical distress, or absence of distress.

RESULTS

Analysis revealed that a higher proportion of children reporting ongoing distress related to surgery at both 2 weeks and 3 months experienced higher immediate postoperative pain levels. A subset of patients with complete data sets for 2 weeks and 3 months (N = 76) was further examined. Among the 47 patients who endorsed surgical distress at 2 weeks, 25 (53.2%) continued to endorse surgical distress at 3 months. Additionally, report of surgical distress at 3 months was associated with longer-term postoperative pain.

CONCLUSIONS

Our data suggest that, in patients undergoing MIRPE, the presence of distress at 2 weeks and 3 months may be associated with higher immediate postoperative pain levels.

Patterns of neuropsychological changes after general anaesthesia in young children: secondary analysis of the Mayo Anesthesia Safety in Kids study

BACKGROUND

We hypothesised that exposure to multiple, but not single, procedures requiring general anaesthesia before age 3 yr is associated with a specific pattern of deficits in processing speed and fine motor skills.

METHODS

A secondary analysis (using factor and cluster analyses) of data from the Mayo Anesthesia Safety in Kids study was conducted, in which unexposed, singly exposed, and multiply exposed children born in Olmsted County, MN, USA from 1994 to 2007 were sampled using a propensity-guided approach and underwent neuropsychological testing at ages 8-12 or 15-20 yr.

RESULTS

In the factor analysis, the data were well fit to a five factor model. For subjects multiply (but not singly) exposed to anaesthesia, a factor reflecting motor skills, visual-motor integration, and processing speed was significantly lower [standardised difference of -0.35 (95% confidence interval {CI} -0.57 to -0.13)] compared with unexposed subjects. No other factor was associated with exposure. Three groups were identified in the cluster analysis, with 106 subjects (10.6%) in Cluster A (lowest performance in most tests), 557 (55.9%) in Cluster B, and 334 (33.5%) in Cluster C (highest performance in most tests). The odds of multiply exposed children belonging to Cluster A was 2.83 (95% CI: 1.49-5.35; P=0.001) compared with belonging to Cluster B; there was no other significant association between exposure status and cluster membership.

CONCLUSIONS

Multiple, but not single, exposures to procedures requiring general anaesthesia before age 3 yr are associated with a specific pattern of deficits in neuropsychological tests. Factors predicting which children develop the most pronounced deficits remain unknown.

An automated real-time method for the detection of patients at risk for malignant hyperthermia

BACKGROUND

Malignant hyperthermia (MH) is a rare anesthetic pharmacogenetic disorder that can be difficult to detect in its earliest phases. Prompt treatment is known to improve outcomes. The modern anesthesia information management systems (AIMS) collect enormous amounts of data. However, data lack context and are not able to provide real-time guidance. Utilizing our AIMS, we developed the capacity to incorporate decision support.

AIMS

We describe the creation and evaluation of a real-time detection tool for MH.

METHODS

Cases of MH from 2003 to 2013 were retrospectively reviewed to confirm the diagnosis of MH and to calculate a MH clinical grading scale score. The index cases were utilized to develop four electronic data Rules, based on endtidal CO2 (ETCO2 ) and temperature criteria. The Rules were then applied retrospectively to the index cases and to a full cohort of general operating room (OR) patients from January 2012 to June 2012. If criteria for possible MH was met, the detection tool generated an alert on the monitor at the patient's bedside.

RESULTS

We identified seven patients with confirmed MH with MH Scores ranging from 28 to 70. Using four data Rules, all of our seven index cases were captured and generated an appropriate alert. Median time from MH computer alert time to dantrolene administration time among our index cases was 23 min (IQR 17-77). There were 938 false-positive alerts for possible MH (1.8%) when the Rules were applied to a general OR cohort of 51 579 total cases from January 2012 to June 2012.

CONCLUSIONS

We demonstrated a real-time MH detection tool based on established physiologic criteria that is sensitive enough to capture cases suspicious for MH, while limiting false positives to prevent alarm fatigue. This has the potential to notify the provider of possible MH such that treatment may be rapidly initiated.

Construction and Characterization of a Population-Based Cohort to Study the Association of Anesthesia Exposure with Neurodevelopmental Outcomes

Exposure to general anesthesia at an early age has been associated with adverse neurodevelopmental outcomes in both animal and human studies, but some of these studies employed anesthetic agents that are no longer in clinical use. In this manuscript, we describe the methods used to construct a new population-based study cohort to study the association between early anesthetic exposure and subsequent neurodevelopmental outcomes. A birth cohort of all children born in Olmsted County, MN from January 1, 1996 to December 31, 2000 was identified. For each, school enrollment status in the Independent School District (ISD) 535 at age 5 or 6 and all episodes of anesthetic exposure before age 3 were identified. A study cohort was created by matching children enrolled in ISD 535 based on the propensity of receiving general anesthesia. Three analyses were performed to characterize the study cohort by comparing the birth and parental information, comorbidities, and socioeconomic status. The first analysis compared the characteristics of birth cohort children who were and were not enrolled in ISD 535. The second analysis evaluated the success of the propensity matching schemes in creating groups of children that were similar in measured characteristics except for anesthesia exposure. The third analysis compared the characteristics of children with anesthesia exposures who were and were not included in the final cohort based on propensity matching. Results of these analyses demonstrate only slight differences among the comparison groups, and therefore these are unlikely to compromise our future analysis of anesthetic exposure and neurodevelopmental outcomes.

Neurodevelopment of children exposed to anesthesia: design of the Mayo Anesthesia Safety in Kids (MASK) study

There is increasing evidence that exposure of developing brains in animals, including nonhuman primates, to commonly-utilized anesthetic agents may cause adverse effects on cognition and behavior. In this paper, we summarize our methodology for a population-based, propensity-matched study to evaluate possible anesthesia-related sequelae in preschool children when evaluated in elementary or high school. A cohort of all children born in Olmsted County, Minnesota between the years 1994 and 2007 who are currently local residents has been identified. Existing medical records are being used to identify all episodes of exposure to general anesthesia prior to the age of 3 years (i.e., prior to their 3rd birthday). Children with multiple, single, and no anesthesia exposure are sampled for testing between the ages of 8 and 12 years or 15 and 19 years during the period 2012-2016. To match children in different exposure groups as closely as possible, sampling is guided by propensity-matching for the likelihood of receiving anesthesia. Selected children are invited to participate in a single 4-hour session of neuropsychological testing, including the National Center for Toxicological Research-Operant Test Battery, which has been used to study anesthetic neurotoxicity in nonhuman primates. The results of this testing will be compared among children with different anesthetic exposure histories. The expected products of this research will be a detailed phenotype of possible anesthetic-associated neurotoxicity in humans, utilizing a robust patient database and neuropsychological testing battery, and the first comparison of effects of anesthetic exposure in children and nonhuman primates performing nearly identical behavioral tasks.

Management of neonatal abstinence syndrome from opioids

Most infants at risk for neonatal abstinence syndrome have opioid plus another drug exposure; polypharmacy is the rule rather than the exception. Scales for evaluation of neonatal abstinence syndrome are primarily based for opioid withdrawal. A standard protocol to treat neonatal abstinence syndrome has not been developed. Institute nonpharmacologic strategies for all neonates at risk. The American Academy of Pediatrics recommends mechanism-directed therapy (treat opioid withdrawal with an opioid) as the first-line therapy. Second-line medications are currently under evaluation.

Attention-deficit/hyperactivity disorder after early exposure to procedures requiring general anesthesia

OBJECTIVE

To study the association between exposure to procedures performed under general anesthesia before age 2 years and development of attention-deficit/hyperactivity disorder (ADHD).

PATIENTS AND METHODS

Study patients included all children born between January 1, 1976, and December 31, 1982, in Rochester, MN, who remained in Rochester after age 5. Cases of ADHD diagnosed before age 19 years were identified by applying stringent research criteria. Cox proportional hazards regression assessed exposure to procedures requiring general anesthesia (none, 1, 2 or more) as a predictor of ADHD using a stratified analysis with strata based on a propensity score including comorbid health conditions.

RESULTS

Among the 5357 children analyzed, 341 ADHD cases were identified (estimated cumulative incidence, 7.6%; 95% confidence interval [CI], 6.8%-8.4%). For children with no postnatal exposure to procedures requiring anesthesia before the age of 2 years, the cumulative incidence of ADHD at age 19 years was 7.3% (95% CI, 6.5%-8.1%). For single and 2 or more exposures, the estimates were 10.7% ( 95% CI, 6.8%-14.4%) and 17.9% ( 95% CI, 7.2%-27.4%), respectively. After adjusting for gestational age, sex, birth weight, and comorbid health conditions, exposure to multiple (hazard ratio, 1.95; 95% CI, 1.03-3.71), but not single (hazard ratio,1.18; 95% CI, 0.79-1.77), procedures requiring general anesthesia was associated with an increased risk for ADHD.

CONCLUSION

Children repeatedly exposed to procedures requiring general anesthesia before age 2 years are at increased risk for the later development of ADHD even after adjusting for comorbidities.

Cognitive and behavioral outcomes after early exposure to anesthesia and surgery

BACKGROUND

Annually, millions of children are exposed to anesthetic agents that cause apoptotic neurodegeneration in immature animals. To explore the possible significance of these findings in children, we investigated the association between exposure to anesthesia and subsequent (1) learning disabilities (LDs), (2) receipt of an individualized education program for an emotional/behavior disorder (IEP-EBD), and (3) scores of group-administered achievement tests.

METHODS

This was a matched cohort study in which children (N = 8548) born between January 1, 1976, and December 31, 1982, in Rochester, Minnesota, were the source of cases and controls. Those exposed to anesthesia (n = 350) before the age of 2 were matched to unexposed controls (n = 700) on the basis of known risk factors for LDs. Multivariable analysis adjusted for the burden of illness, and outcomes including LDs, receipt of an IEP-EBD, and the results of group-administered tests of cognition and achievement were outcomes.

RESULTS

Exposure to multiple, but not single, anesthetic/surgery significantly increased the risk of developing LDs (hazard ratio: 2.12 [95% confidence interval: 1.26-3.54]), even when accounting for health status. A similar pattern was observed for decrements in group-administered tests of achievement and cognition. However, exposure did not affect the rate of children receiving an individualized education program.

CONCLUSIONS

Repeated exposure to anesthesia and surgery before the age of 2 was a significant independent risk factor for the later development of LDs but not the need for educational interventions related to emotion/behavior. We cannot exclude the possibility that multiple exposures to anesthesia/surgery at an early age may adversely affect human neurodevelopment with lasting consequence.

Neuraxial labor analgesia for vaginal delivery and its effects on childhood learning disabilities

BACKGROUND

In prior work, children born to mothers who received neuraxial anesthesia for cesarean delivery had a lower incidence of subsequent learning disabilities compared with vaginal delivery. The authors speculated that neuraxial anesthesia may reduce stress responses to delivery, which could affect subsequent neurodevelopmental outcomes. To further explore this possibility, we examined the association between the use of neuraxial labor analgesia and development of childhood learning disabilities in a population-based birth cohort of children delivered vaginally.

METHODS

The educational and medical records of all children born to mothers residing in the area of 5 townships of Olmsted County, Minnesota from 1976 to 1982 and remaining in the community at age 5 years were reviewed to identify those with learning disabilities. Cox proportional hazards regression was used to compare the incidence of learning disabilities between children delivered vaginally with and without neuraxial labor analgesia, including analyses adjusted for factors of either potential clinical relevance or that differed between the 2 groups in univariate analysis.

RESULTS

Of the study cohort, 4684 mothers delivered children vaginally, with 1495 receiving neuraxial labor analgesia. The presence of childhood learning disabilities in the cohort was not associated with use of labor neuraxial analgesia (adjusted hazard ratio, 1.05; 95%confidence interval, 0.85-1.31; P = 0.63).

CONCLUSION

The use of neuraxial analgesia during labor and vaginal delivery was not independently associated with learning disabilities diagnosed before age 19 years. Future studies are needed to evaluate potential mechanisms of the previous finding indicating that the incidence of learning disabilities is lower in children born to mothers via cesarean delivery under neuraxial anesthesia compared with vaginal delivery.

Risk factors for laryngospasm in children during general anesthesia

BACKGROUND

Laryngospasm is a common and often serious adverse respiratory event encountered during anesthetic care of children. We examined, in a case control design, the risk factors for laryngospasm in children.

MATERIAL AND METHODS

The records of 130 children identified as having experienced laryngospasm under general anesthesia were examined. Cases were identified from those prospectively entered into the Mayo Clinic performance improvement database between January 1, 1996 and December 31, 2005. Potential demographic, patient, surgical and anesthetic related risk factors were determined in a 1 : 2 case-control study.

RESULTS

No individual demographic factors were found to be significantly associated with risk for laryngospasm. However, multivariate analysis demonstrated significant associations between laryngospasm and intercurrent upper respiratory infection (OR 2.03 P = 0.022) and the presence of an airway anomaly (OR = 3.35, P = 0.030). Among those experiencing laryngospasm during maintenance or emergence, the use of a laryngeal mask airway was strongly associated even when adjusted for the presence of upper respiratory infection and airway anomaly (P = 0.019). Ten patients experienced postoperatively one or more complications whereas only three complications were observed among controls (P = 0.008). No child required cardiopulmonary resuscitation and there were no deaths in either study cohort.

CONCLUSIONS

In our pediatric population, the risk of laryngospasm was increased in children with upper respiratory tract infection or an airway anomaly. The use of laryngeal mask airway was found to be associated with laryngospasm even when adjusted for the presence of upper respiratory tract infection and airway anomaly.

Management of Pediatric Patients With Complex Regional Pain Syndrome

This review summarizes current information about diagnosis and treatment of complex regional pain syndrome (CRPS) in children. Although it has been widely held that CRPS in children is intrinsically different from adults, there appear to be relatively few differences. However, there is a marked preponderance of lower extremity cases in children. Historically, psychological factors have been invoked to explain the genesis and persistence of CRPS in children, but the evidence is not compelling. Treatment outcome studies are limited but indicate that children generally respond to a primary focus on physical therapy. Multidisciplinary treatment reports are particularly encouraging. The general perception that children have a milder course may relate to the potentially greater willingness of children to actively participate in appropriately targeted treatment rather than to innate differences in the disease process itself. Recurrence rates appear higher than in adults, but response to reinitiation of treatment seems to proceed efficiently. Clinical judgment dictates the extent of medication or interventional therapy added to the treatment to facilitate rehabilitation. In many ways, the approach to the treatment of children mirrors that of adults, with perhaps greater restraint in the use of medications and invasive procedures. The rehabilitation of children with CRPS, like that of adults with CRPS, needs further rigorous investigation.

Effects of repeated injection of local anesthetic on sciatic nerve blocks response

In order to examine whether repeated sciatic nerve blocks showed tachyphylaxis and continuity of sciatic nerve with spinal cord affected development of tachyphylaxis when assayed in vivo by duration of depression compound action potentials (CAP), rats were anesthetized with halothane, ventilated, monitored and supported with stable hemodynamics and temperature. Posterior tibial nerve distally and sciatic nerve in thigh were exposed, placed on bipolar silver electrodes for stimulation and recording respectively. Three sequential sciatic nerve blocks were performed between these electrodes using 0.15 ml of 3% chloroprocaine. Nine rats were chosen to observe the effects of repeated sciatic nerve blocks on CAP. In another 18 rats, a second investigator exposed the sciatic nerve near its origin at spinal cord and randomly performed nerve cut and sham (n=9), and closed the incision blinding the electrophysiologic investigator. The results showed that electrical stimulated tibial nerve induced sciatic nerve Aalpha/beta, Adelta, C fiber mediated CAP waves. CAP amplitudes were remained stable during whole experimental procedure. CAP amplitudes were decreased completely with 3% chloroprocaine blocked sciatic nerve and recovered fully. The duration of CAP depression were reduced with repeated blocks. There were no selective blocked effects on Aalpha/beta, Adelta, C fiber mediated CAP. With sciatic nerve cut proximally, there was no statistical significant tachyphylaxis with 3% chloroprocaine repeated blocked sciatic nerve, and the duration of first and third blocked Adelta fiber mediated CAP was 108+/-20 and 92+/-14 min respectively (P>0.05). In normal rats the duration of first and third blocked Adelta fiber mediated CAP was 110+/-20 and 75+/-16 min respectively (P<0.05). It was suggested that tachyphylaxis to local anesthetics can occur in rats repeated blocked sciatic nerve when assayed in vivo by duration of depression CAP. The continuity of sciatic nerve with spinal cord is one of the important factors affecting the development of tachyphylaxis.

Evidence that spinal segmental nitric oxide mediates tachyphylaxis to peripheral local anesthetic nerve block

BACKGROUND

Tachyphylaxis to sciatic nerve blockade in rats correlates with hyperalgesia. Spinal inhibition of nitric oxide synthase with N(G)nitro-L-arginine methyl ester (L-NAME) has been shown to prevent hyperalgesia. Given systemically, L-NAME also prevents tachyphylaxis. The action of L-NAME in preventing tachyphylaxis therefore may be mediated at spinal sites. We compared systemic versus intrathecal potency of L-NAME in modulating tachyphylaxis to sciatic nerve block.

METHODS

Rats were prepared with intrathecal catheters. Three sequential sciatic nerve blocks were placed. Duration of block of thermal nocifensive, proprioceptive and motor responses was recorded. We compared spinal versus systemic dose-response to L-NAME, and examined effects of intrathecal arginine on tachyphylaxis. An additional group of rats underwent testing after T10 spinal cord transection. In these rats duration of sciatic nerve block was assessed by determining the heat-induced flexion withdrawal reflex.

RESULTS

L-NAME was 25-fold more potent in preventing tachyphylaxis given intrathecally than intraperitoneally. Intrathecal arginine augmented tachyphylaxis. Spinalized rats exhibited tachyphylaxis to sciatic block.

CONCLUSION

The increased potency of intrathecal versus systemic L-NAME suggests a spinal site of action in inhibiting tachyphylaxis. Descending pathways are not necessary for the development of tachyphylaxis since it occurs even after T10 spinal cord transection. Thus tachyphylaxis, like hyperalgesia, is mediated at least in part by a spinal site of action.

Local anesthetics for the pediatric patient

Local anesthetics are often extremely useful in the management of acute, chronic, and procedural pain. They have a low therapeutic ratio, so physicians should not exceed established dosing guidelines for a single bolus or long-term infusions. New local anesthetics that promise better safety and longer duration of action are on the horizon.

NG-nitro-L-arginine methyl ester (L-NAME) prevents tachyphylaxis to local anesthetics in a dose-dependent manner

A model of local anesthetic tachyphylaxis was developed in our group previously using repeated sciatic nerve blocks in rats. In this model, thermal hyperalgesia accelerated tachyphylaxis, and the noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, MK-801, prevented both hyperalgesia and tachyphylaxis. Nitric oxide is thought to be a second messenger for NMDA pathways in the spinal cord, and appears to be involved in spinal mechanisms of hyperalgesia. We hypothesized that nitric oxide synthase inhibitors would also inhibit the development of tachyphylaxis. Repeated rat sciatic nerve blocks were placed by percutaneous injection of 2-chloroprocaine. Block duration was tested by measuring hot-plate latency at 56 degrees C. Two hours before the first nerve block, rats received intraperitoneal injections with saline or one of six concentrations of NG-nitro-L-arginine methyl ester (L-NAME) in a randomized, blinded pattern. Control rats developed tachyphylaxis as seen previously: the duration of the third block was 30% that of the first. L-NAME inhibited the development of tachyphylaxis in a dose-dependent manner; tachyphylaxis was inhibited by 50% using L-NAME at 0.2mg/kg and completely abolished by 50 mg/kg. Nitric oxide pathways may be involved in the development of tachyphylaxis to local anesthetic nerve block.

Safety of intravenous ketorolac therapy in children and cost savings with a unit dosing system

OBJECTIVE

To determine the incidence of side effects with the short-term use of intravenously administered ketorolac in children and the overall cost savings with a unit dosing system.

STUDY DESIGN

We prospectively examined the incidence of complications arising from the intravenous administration of ketorolac to 1747 children (14,810 doses) during a 3-year, 3-month period and assessed cost savings resulting from dividing 60 mg syringes into 7.5, 15, 30, and 60 mg unit doses. Complications were recorded prospectively into a computerized database. Estimated drug costs to the pharmacy were calculated on the basis of the total numbers of each drug fraction administered, with allowance for 1O% wastage as a result of drug expiration.

RESULTS

Side effects occurring with ketorolac administration were rare. Four patients (0.2%) had hypersensitivity reactions to the drug, two of them possibly on the basis of latex allergy. Two patients (O.1%) had renal complications but were subsequently found to have underlying causes that could account for their renal symptoms. One patient (0.05%) had massive gastrointestinal bleeding in the postoperative period. With fractionation of 60 mg syringes, total drug cost to the pharmacy was $34,786, rather than the $86,639 that would have been spent had a single syringe been used for each dose.

CONCLUSION

Ketorolac proved safe for short-term intravenous use in children more than 1 year of age when patients with known contraindications to the use of non-steroidal antiinflammatory drugs were excluded. A considerable reduction in drug costs can be achieved with fractionation of premixed syringes into unit doses.

Regional anesthesia for pain associated with terminal pediatric malignancy

The objectives of this study were to identify the characteristics of children who required regional anesthesia for pain associated with terminal malignancy and to identify the safety, tolerability and effectiveness of regional anesthesia as an analgesic modality in terminal pediatric malignancy. A retrospective examination was made of the medical records of children who died of malignancy following treatment at the Dana-Farber Cancer Institute and Children's Hospital, Boston, Massachusetts and who required either epidural or subarachnoid infusions, or neurolytic blockade for pain management (June, 1986--April, 1994) during the terminal phase of their illness. Eleven patients were identified, with a duration of epidural or subarachnoid infusions ranging from 3 days to 7 weeks. Indications for this intervention included limiting side effects of opioids, neuropathic pain unresponsive to either rapid escalation of opioids or massive opioid infusions, analgesia for thoracocenteses for the drainage of malignant pleural effusions and instillation of intrapleural chemotherapy. Pain was localized to one area in ll patients. Analgesia was judged to be satisfactory in all cases after regional anesthesia was instituted and remained satisfactory in all cases throughout the treatment course. Complications associated with regional anesthesia included dural puncture headache and mild respiratory depression. Five patients were nursed at home with either epidural or subarachnoid infusions.

Use of intraoperative corticosteroids in pediatric tonsillectomy

OBJECTIVE

To determine the effects of a single dose of dexamethasone sodium phosphate on postoperative morbidity in children undergoing tonsillectomy.

DESIGN

Randomized, double-blind, placebo-control clinical trial.

SETTING

Academic, tertiary care children's hospital.

PATIENTS

Sixty-nine children (35 boys, 34 girls), aged 3 to 18 years, undergoing tonsillectomy with or without adenoidectomy.

INTERVENTION

Patients were randomized to receive a single dose of intravenous dexamethasone or saline.

MAIN OUTCOME MEASURES

Pain scores, determined by a Faces Scale, were obtained at 4-hour intervals during the first postoperative day and daily for 7 days thereafter. Total use of an analgesic; type of diet; level of activity; presence of halitosis, nausea, emesis, or fever; and incidence of postoperative bleeding were also compared between the two groups.

RESULTS

The two groups of children were similar in age, gender, diagnosis, and surgical time. Pain scores in the postoperative period were identical while the patients were in the hospital and for the first 7 days after discharge. No statistically significant differences were noted in pain scores, nausea, emesis, halitosis, analgesic medications required, diet, or activity levels between the two groups of patients.

CONCLUSION

A single intraoperative dose of dexamethasone did not appreciably affect postoperative morbidity in children undergoing tonsillectomy.

The risk of infection from epidural analgesia in children: a review of 1620 cases

We reviewed cases to determine whether suspected or confirmed epidural infection was associated with epidural analgesia for 1620 infants, children, and adolescents treated over a 6-yr period at Children's Hospital, Boston. Postoperative patients (1458/1620) received epidural infusions for a median of 2 days (range, 0-8 days). No postoperative patient had an epidural abscess. One 10-yr-old with terminal malignancy received thoracic epidural analgesia via two successive catheters over a 4-wk period. She had Candida colonization of the epidural space along with necrotic epidural tumor. A second oncology patient and two patients with reflex sympathetic dystrophy were evaluated for epidural abscess, but none was found. We conclude that the risk of epidural infection is quite low in pediatric postoperative patients receiving short-term catheterization. Use of prolonged epidural analgesia in the management of chronic pain in children requires careful monitoring of warning signs of infection.

Thermal hyperalgesia accelerates and MK-801 prevents the development of tachyphylaxis to rat sciatic nerve blockade

BACKGROUND

Tachyphylaxis to local anesthetics has been shown to be promoted by longer interanalgesic intervals between injections. We hypothesized that thermal hyperalgesia also would accelerate the development of tachyphylaxis. The n-methyl-D-aspartate antagonist ((+)-5 methyl-10,11-dihydro-5H-dibenzo (a,d) cyclohepten-5,10-imine, or dizocilpine) (MK-801) has been shown to prevent thermal hyperalgesia. We therefore also hypothesized that MK-801 would prevent tachyphylaxis.

METHODS

Catheters were surgically implanted in rats along the sciatic nerve. After recovery and conditioning to the testing paradigm, they received repeated injections of lidocaine or 2-chloroprocaine followed by motor block testing with or without hot-plate testing at 48, 52, or 56 degrees C. In other experiments, MK-801 or saline was administered by intraperitoneal injection before sciatic nerve local anesthetic injection and sensory and motor testing.

RESULTS

Rats receiving repeated lidocaine or 2-chloroprocaine injections, when repeatedly subjected to hot-plate testing at 56 degrees C, developed thermal hyperalgesia and tachyphylaxis to motor and sensory blockade. Rats receiving either no hot-plate exposure or hot-plate exposure at 48 degrees C developed no tachyphylaxis or hyperalgesia. Rats tested at 52 degrees C developed milder hyperalgesia and developed tachyphylaxis more slowly than did rats tested at 56 degrees C. Control experiments excluded artifacts due to circadian rhythm, injection volume, and learning. Rats pretreated with MK-801 showed no tachyphylaxis over a series of three injections.

CONCLUSIONS

Thermal hyperalgesia accelerates the development of tachyphylaxis to rat sciatic nerve blockade, and MK-801 prevents tachyphylaxis in this model. n-Methyl-D-aspartate receptor antagonists may have future clinical utility in increasing the duration of effectiveness of prolonged local anesthetic administration.

Chronic exposure to lidocaine does not alter flux through sodium channels in cultured neuronal cells

BACKGROUND AND OBJECTIVES

Although tachyphylaxis to local anesthetics has been reported in the clinical literature for more than two decades, the molecular mechanism(s) remain unknown. The authors described an attempt to create an in vitro model for tachyphylaxis to local anesthetics using cultured neuronal cells.

METHODS

Murine neuroblastoma cells (N1E115) and rat pheochromocytoma cells (PC-12) were grown in the presence or absence of lidocaine or tetrodotoxin for between 1 and 14 days. Thereafter, the authors tested flux through sodium channels by measuring total and tetrodotoxin-sensitive flux of 14C-labeled guanidinium (a ligand for the sodium channel) into the cells using the technique of Jacques et al.

RESULTS

Chronic lidocaine or tetrodotoxin treatment caused no change relative to control cells in total or tetrodotoxin-sensitive guanidinium flux, or in the subsequent ability of lidocaine in the flux assay mixture to inhibit guanidinium flux.

CONCLUSIONS

The authors concluded that chronic lidocaine or tetrodotoxin application did not produce changes in stimulated sodium channel activity or subsequent lidocaine susceptibility in this model. To the extent that this model simulated the clinical situation, mechanisms other than up-regulation of sodium channel number or maximal stimulated flux per channel may have been responsible for producing tachyphylaxis.

Reflex sympathetic dystrophy in children. Clinical characteristics and follow-up of seventy patients

We report on the experience with our first seventy patients who had reflex sympathetic dystrophy and were less than eighteen years old (average age, 12.5 years). In our series, the patients were predominantly girls (male to female ratio, 11:59) and the lower extremity was involved most often (sixty-one of the seventy patients). The average time from the initial injury to the diagnosis was one year, which indicates that the syndrome remains under-recognized in patients in this age-group. Conservative treatment with physical therapy, transcutaneous electrical nerve stimulation, psychological therapies including cognitive-behavioral management and relaxation training, and tricyclic anti-depressants was effective in improving the average scores for pain and function for forty patients. Sympathetic blocks were helpful for twenty-eight of thirty-seven patients. Thirty-eight of the seventy patients in the series continued to have some degree of residual pain and dysfunction. Reflex sympathetic dystrophy in children differs in presentation and clinical course from the syndrome in adults. It is best treated in a multidisciplinary fashion.

Catalytic mechanism and interactions of NAD+ with glyceraldehyde-3-phosphate dehydrogenase: correlation of EPR data and enzymatic studies

Perdeuterated spin label (DSL) analogs of NAD+, with the spin label attached at either the C8 or N6 position of the adenine ring, have been employed in an EPR investigation of models for negative cooperativity binding to tetrameric glyceraldehyde-3-phosphate dehydrogenase and conformational changes of the DSL-NAD+-enzyme complex during the catalytic reaction. C8-DSL-NAD+ and N6-DSL-NAD+ showed 80 and 45% of the activity of the native NAD+, respectively. Therefore, these spin-labeled compounds are very efficacious for investigations of the motional dynamics and catalytic mechanism of this dehydrogenase. Perdeuterated spin labels enhanced spectral sensitivity and resolution thereby enabling the simultaneous detection of spin-labeled NAD+ in three conditions: (1) DSL-NAD+ freely tumbling in the presence of, but not bound to, glyceraldehyde-3-phosphate dehydrogenase, (2) DSL-NAD+ tightly bound to enzyme subunits remote (58 A) from other NAD+ binding sites, and (3) DSL-NAD+ bound to adjacent monomers and exhibiting electron dipolar interactions (8-9 A or 12-13 A, depending on the analog). Determinations of relative amounts of DSL-NAD+ in these three environments and measurements of the binding constants, K1-K4, permitted characterization of the mathematical model describing the negative cooperativity in the binding of four NAD+ to glyceraldehyde-3-phosphate dehydrogenase. For enzyme crystallized from rabbit muscle, EPR results were found to be consistent with the ligand-induced sequential model and inconsistent with the pre-existing asymmetry models. The electron dipolar interaction observed between spin labels bound to two adjacent glyceraldehyde-3-phosphate dehydrogenase monomers (8-9 or 12-13 A) related by the R-axis provided a sensitive probe of conformational changes of the enzyme-DSL-NAD+ complex. When glyceraldehyde-3-phosphate was covalently bound to the active site cysteine-149, an increase in electron dipolar interaction was observed. This increase was consistent with a closer approximation of spin labels produced by steric interactions between the phosphoglyceryl residue and DSL-NAD+. Coenzyme reduction (DSL-NADH) or inactivation of the dehydrogenase by carboxymethylation of the active site cysteine-149 did not produce changes in the dipolar interactions or spatial separation of the spin labels attached to the adenine moiety of the NAD+. However, coenzyme reduction or carboxymethylation did alter the stoichiometry of binding and caused the release of approximately one loosely bound DSL-NAD+ from the enzyme. These findings suggest that ionic charge interactions are important in coenzyme binding at the active site.

Structural and motional changes in glyceraldehyde-3-phosphate dehydrogenase upon binding to the band-3 protein of the erythrocyte membrane examined with [15N,2H]maleimide spin label and electron paramagnetic resonance

Binding of the glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase [GAPDHase; D-glyceraldehyde-3-phosphate:NAD+ oxidoreductase (phosphorylating EC 1.2.1.12], to the cytoplasmic segment of band-3 protein in the erythrocyte (RBC) membrane has been examined by electron paramagnetic resonance (EPR) and saturation transfer EPR (ST-EPR) spectroscopies. GAPDHase, which was isolated from rabbit muscle and labeled with the resolution-enhancing deuterated N-(15N-1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl)maleimide spin label ([15N,2H]MSL), showed the same binding specificity for the transmembrane band-3 protein of human erythrocyte membranes as reported for unlabeled GAPDHase from human RBC. Experimental EPR lineshapes from soluble and membrane-bound enzymes were analyzed by direct stimulation of spectra and indicated a structural alteration of the bound GAPDHase in the vicinity of the spin label, which was attached covalently to the active-site cysteine-149 residue. A rigorous theoretical analysis of the ST-EPR spectra of soluble and membrane-bound enzyme is presented and utilized in conjunction with model system analysis to demonstrate that the motion of membrane-bound GAPDHase could be characterized by an effective isotropic rotational correlation time of 20 microseconds. This indicated that the GAPDHase--band-4 complex exhibits motional freedom relative to the membrane-spanning segment of the band-3 protein or the RBC. The double substituted spin label [15N,2H]MSL affords gains in sensitivity and resolution that permit studies of membrane-bound enzymes at physiological levels and quantitative simulations of the EPR and ST-EPR lineshapes with reasonable computation times.