The Society of Pediatric Anesthesia: Fifteenth Annual Meeting, New Orleans, Louisiana, October 12, 2001
2002; Lippincott Williams & Wilkins; Volume: 94; Issue: 6 Linguagem: Inglês
10.1097/00000539-200206000-00057
ISSN1526-7598
Autores Tópico(s)Cardiac, Anesthesia and Surgical Outcomes
ResumoThe 15th Society of Pediatric Anesthesia Annual Meeting took place in the bayou country, New Orleans, LA, on October 12, 2001. Despite the recent events of September 11th and concerns surrounding air travel, the meeting was well attended and the lecturers well received. The morning session included a series of lectures discussing temperature. Normothermia, hypothermia, and hyperthermia (malignant) were serially discussed. In the first session, Dr. Steven Frank, of the Johns Hopkins Hospital, reviewed temperature regulation in the pediatric patient. He began by reviewing the physiology of temperature regulation. Dr. Frank stated that the hypothalamus integrates afferent information from multiple thermoreceptors throughout the body. The majority (80%) of the information derives from core body receptors and receptors in the hypothalamus itself. The hypothalamus compares the temperature data received from the receptors with a central set point for temperature. In response, efferent information is sent out to alter behavior (seek a warmer or colder environment, change clothing, etc.) and trigger physiologic responses to either conserve heat through shivering and vasoconstriction or enhance cooling through vasodilatation and sweating. In neonates, nonshivering thermogenesis is a major source of heat production but at a high energy expenditure. Dr. Frank went on to discuss the role of anesthesia on thermoregulation. Anesthesia significantly alters thermoregulation in the absence of active warming measures. Inhaled anesthetics provide the most profound decrease in temperature through impaired afferent, central, and efferent mechanisms. The decrease in core temperature during general anesthesia is approximately 1°C for the first 36 min and 1°C/h for the first 1–2 h. Vasoconstriction does not occur until the core temperature approaches 34°C. Dr. Frank presented work by Bissonnette and Sessler suggesting that the thresholds for vasoconstriction in infants and children are quite similar to those reported for adults, but because of the increased surface area/body mass ratio, children lose an increased amount of heat through radiant mechanisms. Stoen and Sessler suggest that higher brain concentrations of inhaled anesthesia reduce the thermoregulating response. Barbiturates induce skin vasodilatation, leading to heat loss, and opioids also impair thermoregulation, but through a more centrally mediated mechanism. Regional anesthetics do not affect central thermoregulation but cause significant vasodilatation, resulting in heat loss, and impair efferent feedback to the brain from peripheral thermoreceptors. The higher the block, the lower the core temperature. The combination of general and regional techniques has a synergistic effect on decreasing temperature, according to Dr. Frank. Active warming techniques have become an important component of anesthetic care. One of the early approaches to maintaining normothermia was the use of warming and humidifying inspired gases. This technique has been found to be suboptimal in adults, because 20 kg. Dr. Schulman emphasized that MH appears to be a phenotypic expression of multiple mutations involved in myocyte regulation of calcium, which can account for variable presentations. The treatment of MH is dantrolene sodium. Dantrolene blocks the release of calcium from the sarcoplasmic reticulum at the ryanodine receptor. The loading dose of dantrolene is 2.4 mg/kg, but doses of up to 10 mg/kg may be needed to initiate a reduction in the hypermetabolic state. Subsequent dosing of 1.2 mg/kg every 6 h is recommended. Dr. Barbara Brandom is in charge of the National MH registry at the Children’s Hospital of Pittsburgh. She noted that MH is a rare disease and that few anesthesiologists encounter an episode of MH in their training or even in practice. The registry therefore provides a repository of cases to assist clinicians in understanding the varied presentation of MH and to more accurately diagnose the disease in clinical situations. The MH hotline (800-644-9737) is maintained by the Malignant Hyperthermia Association of the United States, or MHAUS (http://www.mhaus.org). MHAUS provides a 365 days-per-year/24-h-per-day telephone consultation service to facilitate diagnosis and management of MH. Twenty-eight volunteer anesthesiologists maintain the MH hotline. Any case reported to the hotline that is suggestive of MH triggers an adverse metabolic/musculoskeletal reaction to anesthesia report. These reports are maintained in the MH registry. According to Dr. Brandom, >50% of the adverse metabolic/musculoskeletal reaction to anesthesia reports in the registry are pediatric cases. Dr. Brandom then discussed four cases. The first case was a 9-yr-old boy with a sudden increase in end-tidal CO2 and minute ventilation 20 min after a propofol, isoflurane, nitrous oxide, and mivacurium anesthetic for an orthopedic procedure. The minute ventilation required to keep the carbon dioxide 40% of the cases in which cardiac arrest occurred, an occult myopathy was subsequently diagnosed. The fourth and final case discussed by Dr. Brandom was a healthy high school graduate who sought a career in the US military. His family history was positive for MH. The military required a muscle biopsy, and the contracture test was positive. A series of genetic testing revealed a ryanodine receptor mutation. The afternoon session of the Society of Pediatric Anesthesia Society Annual Meeting began with a session on hospital-based pain management by Drs. Myron Yaster (Johns Hopkins University Hospitals) and Steven J. Weisman (Children’s Hospital of Wisconsin), a pro/con debate on the use of regional techniques for children undergoing cardiopulmonary bypass (CPB) by Drs. Gregory Hammer (Stanford University) and James M. Steven (Children’s Hospital of Philadelphia), and a review of bioterrorism by Dr. Frank H. Kern (Duke University Medical Center). Hospital-based pain management remains a conundrum for many pediatric hospitals and anesthesiologists. The first two lectures of the afternoon were organized to look at different approaches to both meeting Joint Commission on Accreditation of Healthcare Organizations (JCAHO) accreditation for pain management and optimizing patient care. Dr. Yaster began the session by reviewing the role of JCAHO in guiding hospital quality and discussed its 1999 standards for requiring the assessment and management of pain in hospitals and other health care settings. These standards were a joint venture of the JCAHO and the University of Wisconsin and were funded through the Robert Wood Johnson Foundation. The purpose was to clearly define the alleviation of pain as a “basic human right” irrespective of age, medical condition, treatment, primary service responsible for the patient’s care, or medical institution. Data collected over the past decade demonstrated significant undertreatment of pain by health care providers. Children are particularly at risk. The reasons cited by Dr. Yaster include fears of opioid addiction, parental and health care provider’s inability to recognize pain in the child, and fear of the consequences of pain treatment. The pain standard mandated by the JCAHO includes six points: 1. Patient rights and ethics. 2. Pain assessment. 3. Planning and providing pain care. 4. Education of patients. 5. Follow-up and discharge planning. 6. Improving organizational performance. In an attempt to meet these standards at the Johns Hopkins University Hospitals, Dr. Yaster developed a Web-based program. The program is multimedia, didactic, and case based. A live demonstration of the Web-based program was shown during the meeting. The program allows access by all providers within the hospital. At large institutions such as Johns Hopkins University Hospitals, thousands of providers can access the program and document certified knowledge in pain assessment and treatment. The cost of putting together the Web-based program is significant, but it pales in comparison to the cost of maintaining a continuous educational program for new employees and recertification of current members of the medical staff. The program is divided into separate segments, including initial screening, pain assessment, how to manage pain, and continuity of care after discharge from the hospital. Both pharmacologic and nonpharmacologic interventions are introduced. Comprehension is tested on-line, and a minimal level of performance satisfies competency. When the examination is passed, a certificate is provided to be printed, and an electronic database is maintained for institutional record keeping. According to Dr. Yaster, there remains a pervasive view that infants do not remember painful experiences and have reduced pain perception. This is untrue. In fact, Dr. Yaster states that recent data support that pain pathways are fully developed by 24 wk of gestation, and animal data suggest that persistent pain actually enhances the development of pain pathways and results in increased pain perception later in life. After Dr. Yaster’s presentation, Dr. Steven Weisman, the Jane B. Pettit Chair in Pain Management at the Children’s Hospital of Wisconsin, spoke. Dr. Weisman discussed “The Comfort Zone,” a comprehensive pain management initiative supported by the entire health system of the Children’s Hospital of Wisconsin, including funding from the Children’s Hospital Foundation. The program was oriented to patient, parent, nurse, and physician. Education was initiated to increase patient, parent, and provider awareness of pain policies and treatment options. Before the “Comfort Zone” initiative, comparative data with other institutions demonstrated that the Children’s Hospital of Wisconsin failed to match the standards of the National Association of Children’s Hospitals and Related Institutions survey of pain management and family satisfaction. In response, the Comfort Zone was developed. It was initially supported by a US$2,000,000 endowment for the Pain Center. The program includes two pediatric anesthesiologists, two clinical nurse specialists, one pediatric psychologist, one research associate, one administrative assistant, and support from the office of public relations to fund public awareness campaigns. Since the roll-out of the Comfort Zone, new outpatient referrals have increased from 62 children in 1998 to 130 children in 2000. Inpatient referrals to the acute pain service have increased from 554 to 911 over the same time period. Nursing assessment of pain improved dramatically. Pain assessment in postoperative cardiac patients improved from 1.6 assessments in the first 24 h to 3.8. Nursing compliance with procedural sedation guidelines is at 95%, and parental pain management education by the bedside nurse has achieved 100% compliance. The philanthropic component of the program has also been immensely successful. Over the last 2 yr, nearly US$2.5 million has been added to the endowment, and pain management has become a major feature of Children’s Hospital of Wisconsin promotional material, according to Dr. Weisman. Dr. Weisman stated that a program such as the Comfort Zone has a major influence on hospital culture, public awareness, and philanthropy. Its multidisciplinary approach and integration throughout the health system is a novel, yet comprehensive, approach to pain management. Its marketing arm and health system-wide approach has contributed to sustaining philanthropy for the pain management program, which is financially in the black. The second afternoon session was a pro/con debate on the use of regional anesthesia for congenital cardiac procedures requiring CPB. The two combatants were Drs. Gregory B. Hammer (Stanford University Medical Center) and James M. Steven (Children’s Hospital of Philadelphia). Dr. Hammer discussed the benefits of regional anesthesia for the congenital cardiac patient. He reviewed the recent literature supporting an attenuation of the neuroendocrine response to surgical stress and CPB, improved postoperative pulmonary function, reduced need for inotropic support, and a nearly pain-free postoperative course with regional anesthesia. In particular, Dr. Hammer cited the works by Shayevitz and colleagues (University of Michigan) and Rosen and colleagues (University of West Virginia) demonstrating a reduced opioid requirement with neuroaxial blockade in the intensive care unit and significantly lower pain scores. Dr. Hammer also cited a reduced number of opioid side effects, including a more rapid return of bowel function, decreased nausea and vomiting, and reduced hospital stay. He also stated that in contrast to adults, local anesthetic blockade at the T3-5 dermatome does not produce significant hypotension in infants and children. Further, with reduced doses of epidural opioids (bolus doses of 0.05 mg/kg) followed by infusions, children reported excellent analgesia with no evidence of respiratory depression in the absence of systemic opioids. The greatest concern for anesthesia providers remains epidural hematoma formation after neuroaxial anesthesia in children undergoing CPB. Dr. Hammer reviewed a series from Rao and colleagues (1981) of >4000 epidural or spinal anesthetics performed before anticoagulation with heparin for vascular surgery in adults. No cases of epidural hematoma were reported. In contrast to this report, Dr. Hammer also cited Vandermeulen (Anesthesia & Analgesia, 1994), who found 61 reported cases of epidural hematoma or subdural hematoma after neuroaxial anesthesia. Sixty-nine percent occurred in patients with preexisting coagulopathy, including 25 patients receiving heparin. Additionally, 25% had a traumatic or difficult needle placement. Dr. Hammer cited estimates from the literature of a 1:150,000 to 1:200,000 incidence of hematoma formation after neuroaxial blockade, with no data on coagulation status. Dr. Hammer currently uses spinal anesthesia or epidural anesthesia in combination with general anesthesia for patients whom he is planning to extubate in the operating room. Spinal anesthetics are placed immediately after intubation and before central venous or arterial line placement. IV opioids are avoided, and the dosing regimens are age dependent. For spinal anesthetics, children under 1 yr old receive tetracaine 2.0 mg/kg with 0.007 mg/kg of morphine in a hyperbaric solution. Children from 1 to 3 yr old receive tetracaine 1.0 mg/kg plus 0.007 mg/kg of morphine. Children from 4 to 8 yr old receive tetracaine 0.5 mg/kg plus 0.007 mg/kg of morphine, and children older than 8 yr are administered 0.01 mg/kg of morphine alone. Epidural anesthesia is usually administered through the caudal route; either a single dose of preservative-free morphine in doses of 0.05–0.1 mg/kg is administered, or a catheter is placed and a bolus dose of 0.04 mg/kg is administered, followed by a continuous infusion of 0.0075 mg · kg−1 · h−1. The infusion is maintained for 48–72 h. Dr. Hammer also discussed the use of combined epidural and local anesthetics via the epidural route. Because of local anesthetic toxicity, he advocates thoracic epidural blockade. In infants, he recommends sliding a catheter up from the caudal position 16–18 cm to place the catheter tip in proximity with the dermatomes of the surgical incision site. This correlates with the T4 to T8 level. In older children, he places a thoracic epidural between T4 and T8 immediately after tracheal intubation. Dr. Hammer’s recommendation is hydromorphone 0.007 mg/kg and 0.25% bupivacaine at 0.5 mL/kg initially, followed by subsequent doses of 0.3 mL/kg of 0.25% bupivacaine every 90 min intraoperatively. After surgery, a continuous infusion of 0.1% bupivacaine and hydromorphone 0.003 mg/mL at a rate of 0.3 mL · kg−1 · h−1 is administered. Dr. James Steven approached the discussion from the “con” position. He agreed that regional anesthetic techniques are feasible and effective adjuncts to general anesthesia. His concern, however, was determining whether the benefits afforded by regional anesthesia merit the rare but real risk of neurologic injury. Second, Dr. Steven argued that comparative studies of general anesthesia with using less invasive conventional strategies such as patient-controlled analgesia have not been performed. Dr. Steven also advocated focusing on more meaningful outcomes, such as death, morbidity, end-organ dysfunction, and prolonged hospitalization. He also questioned the surrogate variable of stress response as an end point. Recent data from Gruber and colleagues (Anesthesia & Analgesia, 2001) found that the measured stress response in neonates receiving opioid anesthesia in more moderate doses was appreciably less than previously reported, and outcome markers showed no relationship to the level of stress hormone release. In addition, fast-tracking approaches use much smaller doses of opioids for lower-risk cardiac patients, yet they achieve early extubation and reduced length of stay. Typical fast-track approaches reduce length of stay to 2–3 days; further reductions with regional techniques seem unlikely. Dr. Steven went further in his discussion of bleeding risk by stating that comparative data from adult studies or nonbypass pediatric studies do not account for the complex factors associated with congenital cardiovascular patients. These include cyanosis, polycythemia, preexisting coagulopathy, and more severe hemodilution in newborns and infants. Further, estimates of risk are based on statistical methodology targeting a maximum risk of 3/ n with 95% confidence. The assumption is based on similar comparative populations (i.e., not adults) and a high level of detection of epidural hematomas and reporting. If one substitutes the number of reported cases in the literature (n = 108), the estimated risk, at 95% confidence, would be 2.8% for children. Although this appears high, it points out the lack of information to make reliable risk as
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