Trophic and individual efficiencies of size-structured communities.

Individual and trophic efficiencies of size-structured communities are derived from mechanistically based principles at the individual level. The derivations are relevant for communities with a size-based trophic structure, i.e. where trophic level is strongly correlated with individual size as in many aquatic systems. The derivations are used to link Lindeman's trophic theory and trophic theory based on average individuals with explicit individual-level size spectrum theory. The trophic efficiency based on the transfer of mass between trophic levels through predator-prey interactions is demonstrated to be valid only when somatic growth can be ignored. Taking somatic growth into account yields an average individual growth efficiency that is smaller than the trophic efficiency.

Life-history constraints on the success of the many small eggs reproductive strategy.

The reproductive strategy of most fishes is to produce a large number of tiny eggs, leading to a huge difference between egg size and asymptotic body size. The viability of this strategy is examined by calculating the life-time reproductive success R(0) as a function of the asymptotic body size. A simple criterion for the optimality of producing small eggs is found, depending on the rate of predation relative to the specific rate of consumption. Secondly it is shown that the success of the reproductive strategy is increasing with asymptotic body size. Finally the existence of both upper and lower limits on the allowed asymptotic sizes is demonstrated. A metabolic upper limit to asymptotic body size for all higher animals is derived.

Asymptotic size determines species abundance in the marine size spectrum.

The majority of higher organisms in the marine environment display indeterminate growth; that is, they continue to grow throughout their life, limited by an asymptotic size. We derive the abundance of species as a function of their asymptotic size. The derivation is based on size-spectrum theory, where population structure is derived from physiology and simple arguments regarding the predator-prey interaction. Using a hypothesis of constant satiation, which states that the average degree of satiation is independent of the size of an organism, the number of individuals with a given size is found to be proportional to the weight raised to the power -2.05, independent of the predator/prey size ratio. This is the first time the spectrum exponent has been derived solely on the basis of processes at the individual level. The theory furthermore predicts that the parameters in the von Bertalanffy growth function are related as K ∝ L⁻¹∞

Judging the effectiveness of analgesia for children and adolescents during vaso-occlusive events of sickle cell disease.

The effectiveness of analgesia during sickle cell crisis was examined in this descriptive, exploratory study. Pain scores (using the African-American Oucher and the Adolescent Pediatric Pain Tool) and analgesics administered were examined during a 2-hour observation/interview in the hospital while children/adolescents with sickle cell disease (SCD) experienced a vaso-occlusive episode (VOE). A convenience sample of twenty-one 6- to 16-year olds with SCD was included. Evidence indicated that 15 of the 21 children in the sample were in moderate to severe pain during their interviews, indicating that the analgesics did not effectively control their pain. Most participants (17) had received nalbuphine as the primary analgesic by intravenous infusion drip and/or patient-controlled analgesia pump. Many reasons were identified for the inadequate analgesia. The results suggested that the pain of SCD is very complex, requiring continuous adjustment of comfort measures, especially analgesics. More research is needed to examine pain control in children with SCD.

A chronology of pain and comfort in children with sickle cell disease.

OBJECTIVE: To examine the patterns of children's and caregivers' descriptions of pain and the comfort measures used to relieve the pain of sickle cell disease (SCD) at home and in the hospital. DESIGN: Qualitative and quantitative techniques were used to obtain data. Participants were seen twice, first with and then without a vaso-occlusive episode. Multiple simultaneous methodological triangulation was used to integrate the findings from ethnographic interviews and observations as well as limited quantitative findings about pain and comfort measures used. SETTING: A Midwestern children's hospital with a regional SCD service. PARTICIPANTS: Twenty-one African American children and adolescents with SCD, aged 6 to 15 years, and 21 family caregivers. RESULTS: An 8-phase chronology of pain and comfort was revealed from the data about pain and comfort in children with SCD. Although this chronology was an unexpected finding, it was consistent with the original aim of the investigation. Phase 1 (baseline) represented the usual state of the child's condition, which for most was free of pain. Phase 2 or the "pre-pain" state involved no vasoocclusive pain but the child began to show prodromal signs and symptoms of painful episodes, such as yellowing of the eyes or fatigue. Phases 2 through 7 involved increasing then decreasing levels of pain, including the pain start point (phase 3), pain acceleration (phase 4), peak pain experience (phase 5), pain decrease start point (phase 6), and steady pain decline (phase 7). A trip to the emergency department usually occurred during phase 5. In phase 8 (pain resolution), the pain had decreased to a manageable level so that the child could be discharged from the hospital. As pain increased and decreased, so did the number and variety of comfort measures. CONCLUSIONS: A chronology of the pain and comfort experiences for children and adolescents during a vasoocclusive event of SCD emerged from the descriptive data of this study. Findings need to be examined further in larger, quantitative, longitudinal studies that examine more closely the duration, intensity, and character of pain at different times during vaso-occlusive episodes as well as the comfort measures used during specific phases of the pain event.

Practice guidelines for the assessment of children with sickle cell pain.

ISSUES AND PURPOSE: Pain is the most frequent and important problem for children with sickle cell disease (SCD), but it has been undertreated and understudied. A multidisciplinary group of healthcare providers, academics, and people with SCD and their families met to (1) examine the pain of vaso-occlusive events (VOE) in children and adults with SCD and (2) reach consensus about necessary improvements in care. CONCLUSIONS: Accurate assessment of pain is at the crux of effective care for children with VOE. This requires a trusting interactive relationship among patient, family, and healthcare team. Comprehensive pain assessment is a lifelong process in need of continued updating. PRACTICE IMPLICATIONS: Children with SCD seek treatment from nurses in many settings. Traditional care has been frustrating to both families and care providers. Children and adolescents with SCD pain would benefit from nursing care that considers patients' perspectives about pain and comfort as key determinants for treatment. A unified approach to pain assessment may be a significant factor in improving pain control.

Construct validity estimation for the African-American and Hispanic versions of the Oucher Scale.

This study examined the construct validity of the African-American and Hispanic versions of the Oucher Scale as measures of pain in 104 children ages 3 to 12 years old. Scores on the Oucher Scale, Analogue Chromatic Continuous Scale, and Child Medical Fear Scale were obtained after being administered concurrently on one occasion, either before or after surgery. Additionally, Oucher scores were obtained before and after analgesic administration. Significant correlations were found between the two pain intensity measures, while weak, nonsignificant relationships were revealed between the pain and fear measures. Preanalgesic scores were significantly higher than postanalgesic scores. These findings support the construct validity of the two new ethnic versions of the Oucher.

The creation, validation, and continuing development of the Oucher: a measure of pain intensity in children.

This is the first article written by this group of authors/researchers who are collaborating on the development of the Oucher, an assessment tool to assist 3- to 12-year-olds describe the intensity of pain. The background and conceptual framework for its development, the research supporting the validation of the original Oucher, the research to create new ethnic versions, and the basic instructions for clinical use are described. In addition, several issues regarding the continued development and use of the Oucher are identified, including those relative to poster size and the gender and ethnicity of the photographed child. This article illustrates the precision and care needed to create clinically useful tools for obtaining information directly from young children.

Comparison of morphine and methadone for prevention of postoperative pain in 3- to 7-year-old children.

A randomized, double-blind, prospective study was performed to determine the effects of perioperative administration of morphine or methadone on postoperative analgesic requirements and pain scores in 35 children aged 3 to 7 years undergoing major surgery. After a standardized induction of anesthesia, methadone or morphine, 0.2 mg/kg, was blindly administered, and supplemental doses were titrated to achieve comfort in the recovery room. Pain was assessed during the next 36 hours with a combination of validated behavioral and self-report measures. Patients in the methadone group required fewer supplemental opioid analgesic drugs during the next 36 hours, and reported lower pain scores. No patient had prolonged emergence from anesthesia, and no patient required naloxone or postoperative ventilatory assistance. No major adverse events occurred. We conclude that perioperative intravenous administration of methadone is an effective, inexpensive, and technologically simple means for providing prolonged analgesia for children after surgery.

Discordance between self-report and behavioral pain measures in children aged 3-7 years after surgery.

This study examined concurrent self-reports of pain intensity and behavioral responses in 25 children aged 3-7 yr. Behavioral (Children's Hospital of Eastern Ontario Pain Scale, CHEOPS) and self-report (the Oucher and Analogue Chromatic Continuous Scale) measures of pain were obtained following major surgery. The two self-report measures were strongly and significantly correlated, and the pattern of scores over the 36-hr observation period was as expected. There was little relationship between the scores for the self-report and the behavioral measures. Many children who reported severe pain manifested few of the behavioral indicators of distress used in the CHEOPS. This behavioral response pattern may occur commonly in children experiencing pain after surgery and may limit the applicability of current behavioral scales as sole measures of pain intensity in younger children.

The assessment of pain in children.

This article focuses on the methods of pain measurement and assessment in children. The concepts of reliability and validity and the available types of physiologic, self-report, and behavioral measures are addressed. Methods of pain assessment in infants and toddlers, preschoolers, school-aged children, and adolescents are detailed. Finally, some practical suggestions for pediatric pain assessment are provided.

Assessment and management of postoperative pain in children.

This paper focuses on the knowledge base about the assessment and management of postoperative pain in children. The first section deals with the nature and characteristics of postoperative pain. A description of current pain management practices with children, focusing on analgesic administration, is derived from available research literature. These reports suggest that postoperative pediatric pain relief may be inadequate. Recent advances in pain assessment and measurement in all age groups, particularly with verbal children and the new self-report measures, are discussed. The latest developments in pharmacological and nonpharmacological techniques for the relief of children's postoperative pain are also described. Finally, the paper concludes with a few suggestions for pediatricians relative to their role in assisting in the search for better assessment and management techniques in the care of postoperative children.

Issues and advances in pain control in children.

Increased interest in the topic of pain has resulted in pharmacologic advances that provide new possibilities for pain relief in children. It has also resulted in new nonpharmacologic therapies that are now being used more frequently with children. It is hoped that these advances will continue so that health care providers will have a larger repertoire of pain control methods effective with children, and so that the traumatic aspects of hospitalization and health care can be reduced greatly. The pain experienced by children has heretofore been on the backroads of scientific and scholarly development. As a result, we actually know very little about pediatric pain, its measurement, and its treatment. The literature and research cited previously are strikingly limited for providing a base of knowledge to guide clinical practice. We avoided a "cookbook" approach to the discussion on pain control, because there are many of those available. Instead, we presented a summary of the research that is currently available in the attempt to help nurses better recognize the limitations in what we know with certainty about this important topic. We hope that this knowledge will spur readers to examine their own beliefs and knowledge, question former assumptions about pediatric pain, and promote a more inquiring approach to assessment and management of children's pain. Pain is a multidisciplinary problem. Although health care providers from the various disciplines each approach the pain problem from different angles, each approach has its place in the overall picture of solving the problems of pediatric pain control. Nurses have been and will continue to be a vital part of clinical and scientific advancements to move pediatric pain out of the realm of mystery and into the realm of the known.

Methodological issues in the measurement of children's pain.

This paper focuses on some of the major issues surrounding the measurement of children's pain, particularly as they relate to problems of definition, level of measurement, dimensionality, reliability, and validity. The authors briefly describe some of the tools used with children and point out some of the problems that have resulted from the lack of well-tested, thoroughly validated instruments for children. As a common experience of hospitalized children, pediatric pain is creating concern within the health care community. The authors recommend that more attention be paid to the measurement issues surrounding this clinical phenomenon.

Methylene chloride: a two-year inhalation toxicity and oncogenicity study in rats and hamsters.

A long-term study was conducted to determine the possible chronic toxicity and oncogenicity of methylene chloride. Rats and hamsters were exposed by inhalation to 0, 500, 1500, or 3500 ppm of methylene chloride for 6 hr per day, 5 days a week, for 2 years. No exposure-related cytogenetic effects were present in male or female rats exposed to 500, 1500, or 3500 ppm. Females rats exposed to 3500 ppm had an increased mortality rate while female hamsters exposed to 1500 or 3500 ppm had decreased mortality rates. Carboxyhemoglobin values were elevated in rats and hamsters exposed to 500, 1500, or 3500 ppm with the percentage increase in hamsters greater than in rats. Minimal histopathologic effects were present in the livers of rats exposed to 500, 1500, or 3500 ppm. Decreased amyloidosis was observed in the liver and other organs in hamsters exposed to 500, 1500 or 3500 ppm. While the number of female rats with a benign tumor was not increased, the total number of benign mammary tumors was increased in female rats in an exposure-related manner. This effect was also evident in male rats in the 1500- and 3500-ppm exposure groups. Finally, male rats exposed to 1500 or 3500 ppm had an increased number of sarcomas in the ventral neck region located in or around the salivary glands. Therefore, in this 2-year study, some effects were observed in male and female rats exposed to 500, 1500, or 3500 ppm of methylene chloride. In contrast, hamsters exposed to the same exposure concentrations had less extensive spontaneous geriatric changes, decreased mortality (females), and lacked evidence of definite target organ toxicity.