Thirteenth Annual Meeting of the Society for Pediatric Anesthesia, Dallas, Texas, October 8, 1999

The Society for Pediatric Anesthesia (SPA) held its 13th annual meeting on October 8, 1999, in Dallas, TX, in conjunction with the annual meeting of the American Society of Anesthesiologists. The society president, Dr. Steven C. Hall (Northwestern University School of Medicine, Children’s Memorial Hospital, Chicago, IL) emphasized the importance of combining both basic science and clinical advances in our practice in his opening remarks. SPA Program Chair, Dr. Lynn D. Martin (University of Washington School of Medicine, Children’s Hospital and Regional Medical Center, Seattle, WA), then introduced the day’s program–an update on current knowledge in the area of neonatal intensive care, followed by current controversy in the selection of anesthetic technique in the afternoon session. The morning program focused on scientific advances in our understanding of the neonatal central nervous system. The first session, moderated by Dr. Jayant K. Deshpande (Vanderbilt University Medical Center, Nashville, TN), centered on the plasticity of the developing brain and its response to extended exposure to opioids. Speakers for this session were Dr. Michael V. Johnston (Johns Hopkins University and Kennedy-Krieger Institute, Baltimore, MD) and Dr. Santhanam Suresh (Northwestern University Medical School, Children’s Memorial Hospital, Chicago, IL). Dr. Michael V. Johnston Plasticity of the Neonatal Brain. Our understanding of how the brain assigns regions of the cerebral cortex to a particular function has advanced because of development in functional brain imaging. “Functional MRI imaging” has supplanted PET (positron emission tomography) scanning as a means of studying metabolically active regions of the brain without radioactive substances. This imaging technique is able to discern areas of lower oxygen saturation and can distinguish the individual areas of the brain used for hearing and generating words, sight, and speech. Beginning with the homunculus, that gargoyle-like mapping of skin sensation onto the sensory cortex, Dr. Johnston showed with several examples that this map is dynamic and responds to repeated sensory input. Monkeys subjected to repeated fingertip stimulation will increase the area of the sensory cortex devoted to fingertip sensation. In a series of people skilled at tuning violins, the brain region assigned to tuning the instrument was larger in those who had begun playing at an earlier age. It’s not just that we “use it or lose it,” but rather we grow new neurons to handle more frequently used information. Our brain map continually changes with human experience. Even more intriguing is the ability of the brain to reassign neuronal function to a new task. In monkeys subjected to a stroke affecting their hand, extensive physiotherapy increased the amount of brain reassigned from the damaged hand area to the more proximal arm area. In a patient who had become blind, functional imaging showed that the occipital or visual cortex had been reassigned to the sensory task of reading braille! Likewise, in children who have half their brain removed for refractory seizure disorders, “cross system reassignment” occurs (especially in the youngest patients) to allow a remarkable amount of function bilaterally. What is happening at the synaptic level? There is a complex interplay of trophic hormones and cellular processes that can respond to repeated neuronal firing by enhancing a particular pathway, growing new synaptic connections, or even growing new neurons. One such phenomenon, “long-term potentiation,” is not merely the gradual enhancement of a well worn path like those in ancient stone steps. In this process, repeated stimulation of a synaptic pathway will suddenly cause a quantum leap in the signals generated as cellular processes reorganize to facilitate that pathway. The metabolic basis is being elucidated for this finding that “neurons that fire together, wire together.” A molecular basis is also coming to light for certain behavioral phenomena. The density of synapses in the brain reaches a dramatic peak at age two and declines to adult levels beyond age eight. This overabundance of synapses at age two facilitates the ability of toddlers to learn complexities like language so readily, but may also overload their processors, leading to the hyperactive behavior affectionately referred to as the “terrible two’s.” This excess of synapses is pruned or “sculpted” down to the adult level by repeated use as we interact with our world. At age two, the brain is at its peak of plasticity. There is a price to pay for such tremendous brain plasticity. A global hypoxic insult produces a very different clinical picture in the elderly than in the neonate. The basal ganglia are very active at birth and use glutamate as the predominant neurotransmitter. Glutamate is taken up from the synapses by a very energy-rich process, much like the bilge pump in a boat. It may, in fact, be the glutamate buildup from the hypoxic insult that causes the damage that leads to spastic diplegia in newborns. Dr. Johnston concluded by stating that we are in an exciting era for research in brain plasticity–neuronal reassignment and neuronal circuitry are a physical and architectural reality that can actually be studied in detail with current techniques. Dr. Santhanam Suresh Pharmacologic Plasticity of the Brain: Opioid Tolerance. In this presentation, the molecular mechanisms surrounding opioid tolerance in the neonate were discussed. Tolerance is defined as the requirement for increasing doses to attain the same clinical effect after repeated administration of a drug. Receptor studies have demonstrated that this occurs as a result of adaptation of the neuronal cells and is not caused by altered drug metabolism. These adaptations of receptor-mediated effects are being studied in detail. For the opioid receptor, these adaptations are best studied at the locus ceruleus in the floor of the fourth ventricle. The opioids decrease signal transmission in pain pathways through an array of cellular effects, including decreased neuron excitability, decreased cyclic AMP production, and increase nitric oxide synthetase. When the opioid receptor is chronically stimulated, this is met with altered cellular mechanisms that attempt to restore neuronal function and response to baseline levels. For instance, as tolerance develops, there is up-regulation of the cyclic AMP pathway to restore this pathway to baseline levels before opioid treatment. In addition, down-regulation and desensitization of the receptors occurs. There is also an internalization or endocytosis of the opioid receptors, which begins with the first dose and continues in a dynamic pattern with subsequent doses. The response is complex and follows a unique pattern for chronic administration of each opioid, invoking each of these adaptations to a different degree. These studies may have particular relevance for two groups of neonates–those born to opioid-addicted mothers and those subjected to chronic opioid administration during prolonged intensive care treatment. Neonates are particularly susceptible to developing tolerance because more opioid reaches their brain through a more permeable blood-brain barrier; they metabolize opioids more slowly and have lower protein binding. Opioid withdrawal is a significant concern in premature infants. Studies have shown that a fentanyl infusion for as little as five days can lead to withdrawal symptoms, and after nine days, 100% of neonates manifested withdrawal in one study. Dr. Suresh reviewed the symptom scoring system being used to evaluate children for evidence of withdrawal. Symptoms such as tremor, irritability, diaphoresis, and fist-sucking compose the score. Subacute symptoms of withdrawal can last as long as six months. He emphasized that withdrawal symptoms can interfere with feeding and weight gain and are more important than achieving rapid withdrawal of opioids. Withdrawal is treated with oral opioid agonists, sedatives, and antihypertensives, in addition to supportive care. Methadone is the mainstay of oral therapy, because many of the oral morphine preparations contain alcohol or other additives. Clonidine is also very effective in treating the symptoms of withdrawal and led to a 30-fold reduction in symptom scores in one study. One benefit of research on the molecular mechanisms of receptors is the discovery of previously unsuspected beneficial interactions. Based on cellular mechanisms, the development of tolerance has been found to hinge on the NMDA receptor. Dextrome- thorphan, an over-the-counter cough suppressant, happens to be an excellent NMDA antagonist and could help prevent tolerance. If theory is borne out by clinical studies, physicians may in the future be giving cough suppressant along with chronic opioids. The second morning session moved from basic science into the clinical arena. It was moderated by Dr. David M. Polaner (Tufts University School of Medicine, Floating Hospital for Children, Boston, MA), who remarked on the dramatic changes that have taken place in neonatal care over the last 15 years. An informative discussion regarding sequalae of prematurity was provided by Dr. Claire M. Brett, (University of California at San Francisco, San Francisco, CA). This lecture was followed by an examination of the implications of prematurity on anesthesia practice by Dr. Peter T. Rothstein (College of Physicians and Surgeons, Columbia University, New York, NY). Dr. Claire M. Brett Sequelae of Prematurity in the 1990s. There has been a tremendous improvement in all measures of outcome between infants born at 24 weeks and those at 26 weeks gestation. It is remarkable that the current survival rate for 500–700-g babies is now greater than 70%. The most significant advance that accounts for this was the release of surfactant in 1990. Babies that would not have survived the effects of prematurity only a few years ago are now surviving in ever-increasing numbers, albeit with more severe chronic disease. Dr. Brett emphasized that “expremature” is not a diagnosis but an ever-broadening spectrum of disease in these survivors. Prematurity is the biggest contributor to chronic lung disease in children. Infant Respiratory Distress Syndrome is characterized not only by surfactant deficiency, but also by neutrophil inflammation and the release of elastase and other inflammatory mediators. Elastase destroys the elastic fibers that provide a structural support for alveolar septal development. Babies that develop chronic lung disease, also called bronchopulmonary dysplasia (BPD), are characterized by persistent neutrophil infiltration and inflammation in the lungs. The primary late sequela of BPD is obstructive airway disease. In expremature children with BPD, when respiratory variables were followed through during the preteen years, there appeared to be continuing improvement even at this age. Humans continue to grow new alveoli for years after birth (one new alveolus every second for eight years). This continuing growth of new alveoli may help the expremature child to improve some variables of lung function. However, it appears that this growth of alveoli never reaches normal adult numbers, at least in a baboon model of BPD. Why is a high oxygen concentration so harmful in premature infants? In normal development, protective vitamin A is delivered transplacentally, and there is a surge in antioxidant enzyme production during late gestation. The premature infant, whose PO2 would otherwise be approximately 40 torr in utero, is missing both of these benefits, yet must contend with high inspired oxygen levels during treatment. Dr. Brett suggested that, in the future, treatment of premature lung disease might be aimed more at the root cause, with manipulation of the antioxidant enzyme systems, or forcing transcription of their genes ahead of schedule. Dr. Peter T. Rothstein Anesthetic Implications of Prematurity in the 1990s. Dr. Rothstein reviewed the anesthetic concerns for premature infants, starting with the basics of temperature regulation and fluid requirements. Neuromuscular blockade is quite variable in the neonatal period, because the neuromuscular junction has not yet matured. He pointed out that the obstructive airway disease in BPD impedes not only inspiration by creating turbulent flow, but expiration because of slow alveolar emptying times; therefore, slower respiratory rates during controlled ventilation may be advantageous. An equipment issue for premature infants is the elbow connector between the circuit Y-piece and the endotracheal tube, which can contribute a proportionately large circuit dead space for the tiny infant. Another issue of importance to anesthesiologists caring for expremature infants is postoperative apnea. This issue has been difficult to deal with because of varying definitions and measurement methods in the literature. Anemia is clearly a contributing risk factor for postoperative apnea. Dr. Rothstein emphasized the need to develop a consistent policy in one’s institution on this issue so that colleagues and staff will know what to expect. A brief business meeting was conducted during the noon luncheon. SPA President, Dr. Hall, paid tribute to Dr. Martin for serving as the SPA Program Chair for the last two years and introduced Dr. Frank H. Kern (Duke University Medical Center) as the SPA Program Chair for the next two years. He then divulged that there were more than 300 attendees at this year’s meeting, more than 2500 active SPA members, and that more than $10,000 had been raised by SPA to fund research efforts. The afternoon session, titled “Pediatric Anesthesia in the Next Millennium,” provided a lively and entertaining review of advances in pediatric anesthesia techniques. This session was moderated by Dr. Peter J. Davis (University of Pittsburgh, Children’s Hospital of Pittsburgh, Pittsburgh, PA). He prepared us for a lively debate on the merits of total IV anesthesia by Dr. Gregory B. Hammer (Stanford University School of Medicine, Packard Children’s Hospital, Stanford, CA) versus inhaled anesthesia by Dr. Jerrod R. Lerman (University of Toronto, Hospital for Sick Children, Toronto, Canada) versus regional anesthesia by Dr. Myron Yaster (Johns Hopkins University, Baltimore, MD). Dr. Gregory B. Hammer Total IV Anesthesia—the Only Way to Go! With skillful allusions to Stanley Kubrick’s Space Odyssey 2001, Dr. Hammer humorously described all alternatives to total IV anesthesia as prehistoric. Short-acting drugs, such as propofol and remifentanil, are extremely titratable, even with large doses, and in the presence of substantial systemic disease. Propofol has an increased volume of distribution and clearance in children, such that greater infusion rates than in adults are required. In extolling the virtues of using a propofol-remifentanil combination, he explained that they are synergistic. There is a requirement for much smaller doses of two agents given together than would be expected if the combination of their effects was simply additive. He described using 0.1 mg of remifentanil mixed with 100 mg of propofol, which is then titrated to give between 25 and 100 μg · kg−1 · min−1 of propofol. Dr. Hammer explained that the cost of inhaled anesthesia is similar in adults and children because similar fresh gas flow rates are used, whereas the cost of IV anesthesia is markedly less in children than in adults because of the children’s smaller weight. He showed that a typical hour of anesthesia with is as as with is 40 as However, total IV anesthesia for a child with a propofol-remifentanil combination for an hour an as much as as with the 100 as much as for a However, he that on drug cost little weight because the anesthetic for only of a Dr. Hammer his by on us that total IV anesthesia is of the of A or and He then the use of a propofol-remifentanil combination in airway and In the future, we may have of agents to of anesthesia With an he used the and of the in Space Odyssey 2001, to us that inhaled anesthesia would be Dr. R. Lerman for Dr. Lerman by inhaled anesthesia as and well IV both and can be and The alveolar are well for these ventilation can be in many which is in a some of of the inhaled have been ventilation with in administration of the concentration at the or the technique for those than years). The or of anesthetic is in children. This is because of their high alveolar their high to the and the and of the the Dr. Lerman that the fresh gas flow rate could have a large on He even so as to is fresh gas flow, provided gas is Even with a or other levels are not a because the also contain and anesthetic What the issue of slow from inhaled This on how the the because the concentration can be during the to the the issue is not the drug from the but from the for which is than both are than In a by the and were all similar for groups of children who and in which was for during the last of the However, more rapid is not for is it what they would the issue of the of generated in the Dr. Lerman pointed out that damage has been shown only in and not in a of not Dr. Myron Yaster Anesthesia and in the of Pediatric Dr. Yaster was given a difficult that regional anesthesia in He to the of with An anesthetic many in it sensory from the transmission from the to the and over sensory input. the regional anesthesia in children was had been that children that can that treating pain and that pain that these are and are to on the risk of a after the regional anesthesia is a The of regional anesthesia the and the and the for anesthetic anesthetic is into a of the the must for The session of the was moderated by Dr. (University of Washington School of Medicine, Children’s Hospital and Regional Medical Center, Seattle, Dr. T. (University of was to provide to the rapid advances in anesthesia care for children in the world. He the and its on anesthesia care in in years, the meeting with an entertaining on a important to For this a and was to give a of the surrounding the of in in Dr. T. Pediatric Anesthesia for the Next The of the The birth rate in developing is such that of is years The to patient is and the of an can be similar to that of a only are children of or or but their or result in late of disease. Dr. this from his with of a and a He described how in one region would and their with in they during He described the by and the of from their and the are the of basic equipment like IV IV anesthesia and there is at best an of and The of anesthetic is very Dr. not to to which every can A practice of anesthesiologists can a their to the their and equipment and and or up an and discussion Anesthesia devoted to help the unique of anesthesia in the developing world. The or and a on the surrounding the of a and He was in on the in and his of the and of the subsequent He provided evidence from the staff from Hospital and the at Medical in described the of the that was to first and He also explained the with the particularly the of firing and a in a of six with a An discussion with of the The meeting to a at the with from an in a It was a to new and new The day’s meeting had a from to in pediatric and the unique of the developing world. The meeting of the with the American of of is for at the and in J. Program The annual meeting of the SPA will the annual meeting in San Francisco, on October Frank H. Program A of program and from the meeting are at cost from the is by from the by or by at or our at

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.