Protein kinases modulate the cellular adaptations associated with opioid tolerance and dependence

Prolonged opioid exposure occurs frequently as a result of clinical use or drug abuse. Research using different ligands, cell lines, and animal models in the past three decades has elucidated some correlation between the biochemical events and behavioral changes resulting from opioid tolerance, dependence and addiction. For the most part, opioid tolerance and dependence are associated with up-regulation of the cAMP pathway, mediated by the supersensitization of adenylyl cyclase and by the altered coupling of opioid receptors to stimulatory G proteins. Neuroadaptive changes in signal transduction following prolonged opioid exposure are mediated by protein kinase systems, such as protein kinase C (PKC), cyclic AMP-dependent protein kinase (PKA), Ca2+/camodulin-dependent protein kinase II (CaMKII), G protein-coupled receptor kinases (GRKs) and mitogen-activated protein kinases (MAPKs). Intermediate steps between opioid receptor activation and the second- or third-messenger cascades include GRK-mediated receptor endocytosis and intracellular trafficking, as well as interactions with excitatory amino acid receptors and regulation of nitric oxide synthesis. Thus, prolonged occupancy by opioid receptor agonists can have differential effects on opioid receptor internalization, down-regulation and desensitization, and in the supersensitization of adenylyl cyclase, which contribute to the development of opioid tolerance and dependence. We discuss the role of various protein kinases in the signaling mechanisms underlying these differences. Clearer understanding of the molecular mechanisms of opioid tolerance and dependence will help in the treatment of patients suffering from acute and chronic pain, or drug dependence and addiction.

Hormonal and metabolic stress responses after major surgery in children aged 0-3 years: a double-blind, randomized trial comparing the effects of continuous versus intermittent morphine

Children aged 0-3 yr were stratified for age and randomized to receive either continuous morphine (CM, 10 microg x kg(-1) x h(-1)) with three-hourly placebo boluses or intermittent morphine (IM, 30 microg x kg(-1) every 3 h) with a placebo infusion for postoperative analgesia. Plasma concentrations of epinephrine, norepinephrine, insulin, glucose and lactate were measured before and at the end of surgery and 6, 12 and 24 h after surgery. Pain was assessed with validated pain scales [the COMFORT scale and a visual analogue scale (VAS)] with the availability of additional morphine doses. Minor differences occurred between the randomized treatment groups, the oldest IM group (aged 1-3 yr) having a higher blood glucose concentration (P=0.003), mean arterial pressure (P=0.02) and COMFORT score (P=0.02) than the CM group. In the neonates, preoperative plasma concentrations of norepinephrine (P=0.01) and lactate (P<0.001) were significantly higher, while the postoperative plasma concentrations of epinephrine were significantly lower (P<0.001) and plasma concentrations of insulin significantly higher (P<0.005) than in the older age groups. Postoperative pain scores (P<0.003) and morphine consumption (P<0.001) were significantly lower in the neonates than in the older age groups. Our results show that continuous infusion of morphine does not provide any major advantages over intermittent morphine boluses for postoperative analgesia in neonates and infants.

Statistical models to predict the need for postoperative intensive care and hospitalization in pediatric surgical patients

OBJECTIVE

To develop statistical models for predicting postoperative hospital and ICU stay in pediatric surgical patients based on preoperative clinical characteristics and operative factors related to the degree of surgical stress. We hypothesized that preoperative and operative factors will predict the need for ICU admission and may be used to forecast the length of ICU stay or postoperative hospital stay.

DESIGN

Prospective data collection from 1,763 patients.

SETTING

Tertiary care children's hospital.

PATIENTS AND PARTICIPANTS

All pediatric surgical patients, including those undergoing day surgery. Patients undergoing dental or ophthalmologic surgical procedures were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

A logistic regression model predicting ICU admission was developed from all patients. Poissonregression models were developed from 1,161 randomly selected patients and validated from the remaining 602 patients. The logistic regression model for ICU admission was highlypredictive (area under the receiver operating characteristics (ROC) curve = 0.981). In the data set used for development of Poisson regression models, significant correlations occurred between the observed and predicted ICU stay (Pearson r = 0.468, p < 0.0001, n = 131) and between the observed and predicted hospital stay for patients undergoing general (r = 0.695, p < 0.0001), orthopedic (r = 0.717, p < 0.0001), cardiothoracic (r = 0.746, p < 0.0001), urologic (r = 0.458, p < 0.0001), otorhinolaryngologic (r = 0.962, p < 0.0001), neurosurgical (r = 0.7084, p < 0.0001) and plastic surgical (r = 0.854, p < 0.0001) procedures. In the validation data set, correlations between predicted and observed hospital stay were significant for general (p < 0.0001), orthopedic (p < 0.0001), cardiothoracic (p = 0.0321) and urologic surgery (p = 0.0383). The Poisson models for length of ICU stay, otorhinolaryngology, neurosurgery or plastic surgery could not be validated because of small numbers of patients.

CONCLUSIONS

Preoperative and operative factors may be used to develop statistical models predicting the need for ICU admission in pediatric surgical patients, and hospital stay following general surgical, orthopedic, cardiothoracic and urologic procedures. These statistical models need to be refined and validatedfurther, perhaps using data collection from multiple institutions.

Interactions of inflammatory pain and morphine in infant rats: long-term behavioral effects

Neonatal rat pups exposed to repetitive acute pain show decreases in pain threshold and altered behavior during adulthood. A model using prolonged inflammatory pain in neonatal rats may have greater clinical relevance for investigating the long-term behavioral effects of neonatal pain in ex-preterm neonates. Neonatal rat pups were exposed to repeated formalin injections on postnatal (P) days 1-7 (P1-P7), with or without morphine pretreatment, and were compared with untreated controls. Behavioral testing during adulthood assessed pain thresholds using hot-plate (HP) and tail-flick (TF) tests, alcohol preference, and locomotor activity (baseline and postamphetamine). Adult rats exposed to neonatal inflammatory pain exhibited longer HP latencies than controls and male rats had longer HP thresholds compared to females. Male rats exposed to neonatal morphine alone exhibited longer TF latencies than controls. Both neonatal morphine treatment and neonatal inflammatory pain decreased ethanol preference, but their effects were not additive. During adulthood, male rats exposed to neonatal inflammatory pain exhibited less locomotor activity than untreated controls. We conclude that neonatal formalin and morphine treatment have specific patterns of long-term behavioral effects in adulthood, some of which are attenuated when the two treatments are combined.

Abnormal cognition and behavior in preterm neonates linked to smaller brain volumes

Volumetric measurements of the brain regions in eight-year-old children indicate that the poor cognitive and behavioral outcomes noted in ex-preterm neonates are associated with reduced volumes of specific regions in the brain. Recent literature suggests that this reduction might result from enhanced apoptosis or excitotoxic damage to highly susceptible immature neurons.

Consensus statement for the prevention and management of pain in the newborn

OBJECTIVE

To develop evidence-based guidelines for preventing or treating neonatal pain and its adverse consequences. Compared with older children and adults, neonates are more sensitive to pain and vulnerable to its long-term effects. Despite the clinical importance of neonatal pain, current medical practices continue to expose infants to repetitive, acute, or prolonged pain.

DESIGN

Experts representing several different countries, professional disciplines, and practice settings used systematic reviews, data synthesis, and open discussion to develop a consensus on clinical practices that were supported by published evidence or were commonly used, the latter based on extrapolation of evidence from older age groups. A practical format was used to describe the analgesic management for specific invasive procedures and for ongoing pain in neonates.

RESULTS

Recognition of the sources of pain and routine assessments of neonatal pain should dictate the avoidance of recurrent painful stimuli and the use of specific environmental, behavioral, and pharmacological interventions. Individualized care plans and analgesic protocols for specific clinical situations, patients, and health care settings can be developed from these guidelines. By clearly outlining areas where evidence is not available, these guidelines may also stimulate further research. To use the recommended therapeutic approaches, clinicians must be familiar with their adverse effects and the potential for drug interactions.

CONCLUSION

Management of pain must be considered an important component of the health care provided to all neonates, regardless of their gestational age or severity of illness.

Clinical importance of pain and stress in preterm neonates

Clinical and laboratory investigations of neonatal pain suggest that preterm neonates have an increased sensitivity to pain and that acute painful stimuli lead to the development of prolonged periods of hyperalgesia. Non-noxious stimuli during these periods of hyperalgesia may expose preterm neonates to established or chronic pain. Acute physiologic changes caused by painful or stressful stimuli can be implicated as important factors in the causation or subsequent extension of early intraventricular hemorrhage (IVH) or the ischemic changes leading to periventricular leukomalacia (PVL). Therapeutic interventions that provide comfort/analgesia in preterm neonates were correlated with a decreased incidence of severe IVH. Long-term follow-up studies of preterm neonates may substantiate the preliminary data associating repetitive painful experiences with some of the neurobehavioral and developmental sequelae resulting from neonatal intensive care.

Effects of perinatal pain and stress

Neonatal intensive care exposes preterm neonates to a series of repeated, randomly occurring invasive procedures and handling, resulting in acute pain, chronic pain, and prolonged stress during a critical window associated with epochal brain development. Characteristics of the immature pain system in preterm neonates (such as a low pain threshold, prolonged periods of windup, overlapping receptive fields, immature descending inhibition) predisposes them to greater clinical and behavioral sequelae from inadequately treated pain than older age groups. Evidence for developmental plasticity in the neonatal brain suggests that repetitive painful experiences during this period or prolonged exposure to analgesic drugs may alter neuronal and synaptic organization permanently. Traditionally, clinicians have chosen the perspective that routine use of analgesic or sedative drugs in preterm neonates may create more problems than minimal therapy. However, the immediate and long-term consequences of inadequately treated pain have forced them to reconsider the risk-benefit ratios for such therapy. Whereas the short-term consequences of prolonged analgesic therapy in human neonates are well-known (tolerance, withdrawal, ventilator dependency), long-term consequences are relatively unknown. Advances in the study of repetitive pain associated with routine NICU care have challenged the perspective that prolonged pain and stress were inevitable consequences of premature birth.

Can adverse neonatal experiences alter brain development and subsequent behavior?

Self-destructive behavior in current society promotes a search for psychobiological factors underlying this epidemic. Perinatal brain plasticity increases the vulnerability to early adverse experiences, thus leading to abnormal development and behavior. Although several epidemiological investigations have correlated perinatal and neonatal complications with abnormal adult behavior, our understanding of the underlying mechanisms remains rudimentary. Models of early experience, such as repetitive pain, sepsis, or maternal separation in rodents and other species have noted multiple alterations in the adult brain, correlated with specific behavioral phenotypes depending on the timing and nature of the insult. The mechanisms mediating such changes in the neonatal brain have remained largely unexplored. We propose that lack of N-methyl-D-aspartate (NMDA) receptor activity from maternal separation and sensory isolation leads to increased apoptosis in multiple areas of the immature brain. On the other hand, exposure to repetitive pain may cause excessive NMDA/excitatory amino acid activation resulting in excitotoxic damage to developing neurons. These changes promote two distinct behavioral phenotypes characterized by increased anxiety, altered pain sensitivity, stress disorders, hyperactivity/attention deficit disorder, leading to impaired social skills and patterns of self-destructive behavior. The clinical important of these mechanisms lies in the prevention of early insults, effective treatment of neonatal pain and stress, and perhaps the discovery of novel therapeutic approaches that limit neuronal excitotoxicity or apoptosis.

Long-term effects of pain in infants

Pain and stress have been shown to induce significant physiological and behavioral reactions in newborn infants, even in those born prematurely. Infants who are born prematurely or seriously ill are commonly exposed to multiple painful and stressful events as part of their prolonged hospitalizations and required medical procedures. There is now evidence that these early events not only induce acute changes, but that permanent structural and functional changes may also result. This article reviews the growing body of evidence of likely long-term effects of early pain and stress on the human infant. It is hoped that a better understanding of this literature will promote more responsive and sensitive management of infants and young children during their encounters with the medical community and will ultimately facilitate the healthy growth and development of all children.

Long-term behavioral effects of repetitive pain in neonatal rat pups

Human preterm neonates are subjected to repetitive pain during neonatal intensive care. We hypothesized that exposure to repetitive neonatal pain may cause permanent or long-term changes because of the developmental plasticity of the immature brain. Neonatal rat pups were stimulated one, two, or four times each day from P0 to P7 with either needle prick (noxious groups N1, N2, N4) or cotton tip rub (tactile groups T1, T2, T4). In groups N2, N4, T2, T4 stimuli were applied to separate paws at hourly intervals;each paw was stimulated only once a day. Identical rearing occurred from P7 to P22 days. Pain thresholds were measured on P16, P22, and P65 (hot-plate test), and testing for defensive withdrawal, alcohol preference, air-puff startle, and social discrimination tests occurred during adulthood. Adult rats were exposed to a hot plate at 62 degrees C for 20 s, then sacrificed and perfused at 0 and 30 min after exposure. Fos expression in the somatosensory cortex was measured by immunocytochemistry. Weight gain in the N2 group was greater than the T2 group on P16 (p < 0.05) and P22 (p < 0.005); no differences occurred in the other groups. Decreased pain latencies were noted in the N4 group [5.0 +/- 1.0 s vs. 6.2 +/- 1.4 s on P16 (p < 0.05); 3.9 +/- 0.5 s vs. 5.5 +/- 1.6 s on P22 (p < 0.005)], indicating effects of repetitive neonatal pain on subsequent development of the pain system. As adults, N4 group rats showed an increased preference for alcohol (55 +/- 18% vs. 32 +/- 21%; p = 0.004); increased latency in exploratory and defensive withdrawal behavior (p < 0.05); and a prolonged chemosensory memory in the social discrimination test (p < 0.05). No significant differences occurred in corticosterone and ACTH levels following air-puff startle or in pain thresholds at P65 between N4 and T4 groups. Fos expression at 30 min after hot-plate exposure was significantly greater in all areas of the somatosensory cortex in the T4 group compared with the N4 group (p < 0.05), whereas no differences occurred just after exposure. These data suggest that repetitive pain in neonatal rat pups may lead to an altered development of the pain system associated with decreased pain thresholds during development. Increased plasticity of the neonatal brain may allow these and other changes in brain development to increase their vulnerability to stress disorders and anxiety-mediated adult behavior. Similar behavioral changes have been observed during the later childhood of expreterm neonates who were exposed to prolonged periods of neonatal intensive care.

Analgesia and sedation in preterm neonates who require ventilatory support: results from the NOPAIN trial. Neonatal Outcome and Prolonged Analgesia in Neonates

BACKGROUND

Preterm neonates are exposed to multiple painful procedures after birth and exhibit acute physiological responses to pain. Occurrence of early intraventricular hemorrhage within 24 to 72 hours after birth suggests a role of pain and stress in the multifactorial causation of severe intraventricular hemorrhage and periventricular leukomalacia. We proposed that such neurologic outcomes in preterm neonates who require ventilatory support may be reduced by morphine analgesia or midazolam sedation compared with a placebo.

OBJECTIVES

To define the incidence of clinical outcomes in the target study population, to estimate the effect size and adverse effects associated with analgesia and sedation, and to calculate the sample size for a definitive test of this hypothesis.

METHODS

Sixty-seven preterm neonates were randomized in a pilot clinical trial from 9 centers. Neonates of 24 to 32 weeks gestation were eligible if they had been intubated and required ventilatory support for less than 8 hours and if they were enrolled within 72 hours after birth. Exclusion criteria included major congenital anomalies, severe intrapartum asphyxia, and participation in other research studies. Severity of illness was assessed by the Clinical Risk Index for Babies, and neonates were randomized to receive continuous infusions of morphine sulfate, midazolam hydrochloride, or 10% dextrose (placebo). Masked study medications were continued as long as clinically necessary, then weaned and stopped according to predefined criteria. Levels of sedation (COMFORT scores) and responses to pain (Premature Infant Pain Profile scores) were measured before, during, and 12 hours after discontinuation of drug infusion. Cranial ultrasound examinations were performed as part of routine practice, and poor neurologic outcomes were defined as neonatal death, severe intraventricular hemorrhage (grade III or IV), or periventricular leukomalacia.

RESULTS

No significant differences occurred in the demographic, clinical, and socioeconomic variables related to mothers and neonates in the 3 groups or in the severity of illness at birth as measured by Clinical Risk Index for Babies scores. Two neonates in the placebo group and 1 neonate in the midazolam group died; no deaths occurred in the morphine group. Poor neurologic outcomes occurred in 24% of neonates in the placebo group, 32% in the midazolam group, and 4% in the morphine group (likelihood ratio chi2 = 7.04, P = .03). Secondary clinical outcomes and neurobehavioral outcomes at 36 weeks' postconceptional age were similar in the 3 groups. Responses elicited by endotracheal tube suction (Premature Infant Pain Profile scores) were significantly reduced during the morphine (P<.001) and midazolam (P = .002) infusions compared with the placebo group.

CONCLUSIONS

This pilot trial suggests that preemptive analgesia given by continuous low-dose morphine infusion may reduce the incidence of poor neurologic outcomes in preterm neonates who require ventilatory support. Limitations in the sample size of this pilot study suggest that these results should be confirmed in a large multicenter randomized trial.

Pharmacokinetics and metabolism of rectally administered paracetamol in preterm neonates

AIM

To investigate the pharmacokinetics, metabolism, and dose-response relation of a single rectal dose of paracetamol in preterm infants in two different age groups.

METHODS

Preterm infants stratified by gestational age groups 28-32 weeks (group 1) and 32-36 weeks (group 2) undergoing painful procedures were included in this study. Pain was assessed using a modified facies pain score.

RESULTS

Twenty one infants in group 1 and seven in group 2 were given a single rectal dose of 20 mg/kg body weight. Therapeutic concentrations were reached in 16/21 and 1/7 infants in groups 1 and 2, respectively. Peak serum concentrations were significantly higher in group 1. Median time to reach peak concentrations was similar in the two groups. As serum concentration was still in the therapeutic range for some infants in group 1, elimination half life (T1/2) could not be determined in all infants: T1/2 was 11.0 +/- 5.7 in 11 infants in group 1 and 4.8 +/- 1.2 hours in group 2. Urinary excretion was mainly as paracetamol sulphate. The glucuronide:sulphate ratio was 0.12 +/- 0.09 (group 1) and 0.28 +/- 0.35 (group 2). The pain score did not correlate with therapeutic concentrations.

CONCLUSIONS

A 20 mg/kg single dose of paracetamol can be safely given to preterm infants in whom sulphation is the major pathway of excretion. Multiple doses in 28-32 week old neonates would require an interval of more than 8 hours to prevent progressively increasing serum concentrations.

Opioid tolerance in neonates: mechanisms, diagnosis, assessment, and management

Opioid tolerance and withdrawal have been challenges for decades. The neurochemical mechanisms of tolerance and dependence are clinically important only because they can affect weaning schedules and the adjustment of doses for neonates. Analgesic effects are characterized by an increased depolarization threshold for the neuron, shorter duration of the action potential generated, and reduced release of neurotransmitters. Tolerance and withdrawal are associated with the reversal of these cellular effects. Adverse clinical effects associated with the use of opioids in neonates include respiratory depression, chest wall rigidity, urinary retention, and decreased gastrointestinal motility. The physiological systems most prominently affected by opioid withdrawal include the central nervous system, gastrointestinal system, and the autonomic nervous system. Opioid withdrawal symptoms in neonates can be assessed by using easily available scoring systems, although these need to be validated for different populations. Management of opioid withdrawal includes the use of other opioids, benzodiazepines and alpha-2 adrenergic receptor antagonist, clonidine. Careful titration of opioids with attention given to appropriate weaning schedules can reduce the incidence of withdrawal in neonates.

Practical approach to analgesia and sedation in the neonatal intensive care unit

The anatomic and physiological bases for nociception are present even in very preterm neonates. Neonates show the same behavioral, endocrine, and metabolic responses to noxious stimuli as older subjects. Preterm infants appear to be more sensitive to painful stimuli and have heightened responses to successive stimuli. Infants receiving intensive care are subjected to frequent stressful procedures and also chronic noxious influences related to the environment of care. Inflammatory conditions such as necrotizing enterocolitis may also cause pain. Untreated pain in babies is associated with increased major morbidity and mortality. Nonpharmacological interventions, including environmental modification and comforting during procedures reduce stress. Intravenous opiates are the mainstay of pharmacological analgesia. A pure sedative agent can provide physiological stability in settings in which there are less acutely painful stimuli or when there are adverse effects from, or tolerance to, opiates. Local anesthesia of skin and mucous membranes is helpful for invasive procedures. Antipyretic analgesics such as acetaminophen have a role in inflammatory pain.

Bilateral vocal cord paralysis after meningitis due to Streptococcus pneumoniae

We report the clinical course of a 15-month-old boy who had fever, decreased activity, and weakness, with severe respiratory distress during transport to the hospital. Laboratory evaluation confirmed the diagnosis of meningitis due to Streptococcus pneumoniae. He was intubated on arrival and required 4 days of ventilatory support. Soon after extubation, he had marked stridor and dyspnea that were unresponsive to standard therapy with nebulized racemic epinephrine and intravenous dexamethasone. Magnetic resonance imaging of the brain revealed nonspecific findings, and airway endoscopy showed bilateral vocal cord paralysis. Repeated endoscopy showed no improvement in vocal cord function and a deficient swallowing mechanism. Tracheostomy was done to facilitate airway management before discharge from the pediatric intensive care unit. We propose that the diagnosis of vocal cord paralysis must be considered in patients with meningitis and respiratory compromise.

Lidocaine iontophoresis for topical anesthesia before intravenous line placement in children

In a double-blind randomized trial including 42 children aged 7 to 18 years, less pain occurred with intravenous placement after iontophoresis of 2% lidocaine with epinephrine, as reported by patients (p = 0.005), parents (p = 0.001), intravenous personnel (p = 0.009), and investigators (p = 0.0002) compared with placebo therapy. Lidocaine iontophoresis provides rapid and effective topical anesthesia for intravenous access in children.

Physiological, hormonal, and behavioral responses to a single fentanyl dose in intubated and ventilated preterm neonates

OBJECTIVE

To study the responses of ventilated preterm neonates to a single dose of opioid.

STUDY DESIGN

In a randomized, double-blind, controlled trial, 22 mechanically ventilated preterm infants (< or = 32 weeks) were observed before medication and at 30 and 60 minutes after administration of fentanyl (3 micrograms/kg) or placebo. Heart rate, blood pressure, arterial blood gases, ventilator settings, and behavioral measures (Neonatal Facial Coding System and Modified Postoperative Comfort Score) were recorded during each period. Blood cortisol, growth hormone, glucose, and lactate were measured before and at 60 minutes after analgesia. Behavioral measures were assessed at the bedside and from video films recorded during each observation period.

RESULTS

Patients presented high basal levels of cortisol, growth hormone, and lactate. Behavioral scales indicated the presence of pain before any medication. In the fentanyl group, the maximum and minimum heart rate decreased and growth hormone level increased after analgesia. At the video analysis of behavioral measures, postoperative comfort score increased and neonatal facial coding system score decreased in the fentanyl group.

CONCLUSION

Single doses of fentanyl analgesia can reduce the physiologic/behavioral measures of pain and stress associated with mechanical ventilation in preterm infants.

A cross-sectional survey of pain and pharmacological analgesia in Canadian neonatal intensive care units

OBJECTIVE

To determine current practices for the use of analgesia term and preterm neonates cared for in Neonatal Intensive Care Units (NICUs).

DESIGN

One-week survey of medical charts of current patients.

SETTING

NICUs in Canada.

PARTICIPANTS

A total of 14 of 38 invited NICUs participated. These units were not different on number of beds, admissions per year, or university affiliation from the nonparticipating units.

MAIN OUTCOME MEASURES

Daily logs were kept of the frequency and type of procedures and analgesia administration for all ill neonates in each NICU during the study period.

RESULTS

The sample consisted of 239 patients. A total of 2,134 invasive procedures were performed. Medication was given specifically 18 times for 17 invasive procedures (0.8%). For another 129 invasive procedures, the patient was receiving analgesia for reasons other than the procedure. Sixteen patients had surgery during the survey period, and another 14 had surgery prior to but within 4 days of the survey. Fifty-one patients received anaesthesia or analgesia specifically related to surgery (39 times), procedures (35 times), or other reasons (34 times), a total of 108 courses. Opioids were the most frequently used medications and were given for all reasons, by continuous infusion, intermittent bolus, or sometimes both methods for the same patient.

CONCLUSIONS

Postoperative pain in neonates in Canadian NICUs appears to be consistently treated, primarily with opioid analgesics, but analgesia, opioid or nonopioid is rarely given for nonsurgical invasive procedures.

Pain management in the pediatric intensive care unit

Critically ill pediatric patients are frequently exposed to acute, established, and chronic pain as a result of their disease processes or intensive care therapies. Despite the availability of many drugs and techniques for providing analgesia, these painful conditions are not adequately treated in a large proportion of children. This article reviews some of the reasons for provision of adequate analgesia and sedation, describes the various classes of drugs commonly used in the pediatric intensive care unit, and lists the techniques and indications for regional and topical anesthesia as well as specific clinical applications for adjuvant analgesic agents. Analgesic approaches that do not have an established record of safety and efficacy in pediatric patients are not reviewed. We propose that adequate and early analgesic interventions will minimize patient's discomfort, maintain metabolic homeostasis, and improve a patient's tolerance of intensive care unit therapies and nursing interventions. Adequate analgesia can be provided to even the sickest child using the drugs, techniques, and novel approaches reviewed.

Laceration repair using a tissue adhesive in a children's emergency department

OBJECTIVE

To determine the effectiveness of a tissue adhesive, Histoacryl Blue (HAB), for laceration repair in children.

DESIGN

Prospective, randomized clinical trial.

SETTING

A tertiary care pediatric emergency center at Egleston Children's Hospital.

PARTICIPANTS

Children who presented for laceration repair between October 1994 and February 1995 were prospectively evaluated. Patients less than 1 or greater than 18 years of age, those with lacerations greater than 5 cm, and those with lacerations located on the eyelids, ears, nose, lips, hands, feet, joints, or perineum were excluded.

INTERVENTIONS

Following consent and routine wound management, including subcutaneous closure when deemed necessary, patients were randomized to receive skin sutures or HAB for cutaneous closure.

METHODS

Length of time required for laceration repair was recorded. Parental perception of the pain experienced by their child was assessed using a visual analogue scale. Photographic documentation of scar appearance at the 2-month follow-up visit was evaluated by plastic surgeons using a visual analogue scale.

RESULTS

Sixty-one children were enrolled: HAB group (N = 30), suture group (N = 31). No differences occurred between groups in laceration length, depth, location, or patient demographics. Length of time required for repair was decreased (median, HAB 7 minutes vs suture 17.0 minutes) and parental assessment of their child's pain was significantly less in the HAB group. Parents were more likely to recommend HAB over suturing to other parents or guardians. Cosmetic outcome in the HAB group was assessed to be as good as, or better than, the cosmetic outcome in the suture group as evaluated by two plastic surgeons.

CONCLUSION

The use of HAB for laceration repair is an acceptable alternative to conventional suturing with a comparable cosmetic outcome. Advantages include less pain to the child, no need for suture removal, and more efficient use of physician time. Parents were also more likely to recommend HAB over suturing for laceration repair.

Intratracheal administration of fentanyl: pharmacokinetics and local tissue effects

OBJECTIVE

To study the pharmacokinetics and local tissue effects resulting from the intratracheal administration of preservative-free fentanyl.

DESIGN

Prospective, randomized, blinded and controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Eighteen adult male New Zealand rabbits.

INTERVENTIONS

Preservative-free fentanyl citrate or normal saline was administered by the intratracheal (i.t.) and intravenous (i.v.) routes to randomized groups of rabbits. The animals were killed at 24, 48 and 72 h following administration.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of fentanyl were measured before administration and at 2, 5, 10, 30, 60 and 120 min following administration by a specific radioimmunoassay. A detailed histological examination of the lung and tracheal tissue was performed to identify local side effects. There were no significant differences in the plasma fentanyl concentrations resulting from the i.v. or i.t. route of administration. In both groups, the concentrations of fentanyl were within the therapeutic range (i.t. 2.37 ng/ml, i.v. 2.53 ng/ml) by 2 min after injection and reached a maximum concentration within 5 min. The bioavailability of i.t. fentanyl was 71%. Microscopic examination of the respiratory system did not show significant differences between the two random groups overall. However, in the sub-group of animals killed at 24 h, more animals in the i.t. group showed signs of inflammation in the lung parenchyma.

CONCLUSIONS

There is rapid absorption of fentanyl following i.t. administration. Pharmacokinetic parameters for fentanyl were not significantly altered by the route of administration. Although there were no signs that i.t. administration of preservative-free fentanyl produces lung injury, a transient and mild inflammatory response was detected at 24 h after administration.

Opioid tolerance and dependence in infants and children

OBJECTIVES

To review the definitions and scientific basis for opioid tolerance and dependence in neonates and older children; to assess objective methods for the clinical evaluation of opioid abstinence syndromes in this age group; and to suggest therapeutic strategies for the treatment of opioid abstinence in critically ill neonates and children.

DATA SOURCES

The published literature on opioid tolerance and dependence in pediatric patients was reviewed. Data from current clinical practices, nursing procedures, and ongoing clinical research were evaluated.

DATA SYNTHESIS

Currently proposed mechanisms of opioid tolerance and dependence are assessed, with particular relevance to the developing human central nervous system. The validity and clinical role of currently available objective methods for the assessment of opioid abstinence in neonates and older infants are defined. The efficacy of various pharmacologic and nonpharmacologic modalities for the treatment of opioid abstinence is evaluated and compared, and a therapeutic approach based on receptor mechanisms, clinical monitoring data, and pharmacologic efficacy is suggested.

CONCLUSIONS

Important parallels for therapeutically-induced opioid tolerance and withdrawal may be drawn from the assessment and management of neonates born from opioid-addicted mothers. Opioid withdrawal can be prevented with appropriate weaning schedules, diagnosed by objective clinical methods, and treated by a variety of pharmacologic and non-pharmacologic means. Pharmacologic therapy includes the use of opioids, with adjuvant drugs such as diazepam, clonidine, or chlorpromazine. The pathophysiology and assessment of therapeutically induced opioid tolerance and withdrawal merit further research in critically ill pediatric patients.

Neonatal pain management

Neonatal pain management is a challenge for the clinician. Research is just beginning to uncover the neonates' capability of expression of pain, explore pharmacologic management strategies, and identify the spectrum of intrusions that may precipitate pain or distress in the critically ill neonate. This article reviews the neonatal biologic, behavioral, and physiologic responses to pain and describes recommendations for clinical management and decision-making.

Halothane-morphine compared with high-dose sufentanil for anesthesia and postoperative analgesia in neonatal cardiac surgery

BACKGROUND

Extreme hormonal and metabolic responses to stress are associated with increased morbidity and mortality in sick adults. We hypothesized that administering deep opioid anesthesia to critically ill neonates undergoing cardiac surgery would blunt their responses to stress and might improve clinical outcomes.

METHODS

In a randomized trial, 30 neonates were assigned to receive deep intraoperative anesthesia with high doses of sufentanil and postoperative infusions of opiates for 24 hours; 15 neonates were assigned to receive lighter anesthesia with halothane and morphine followed postoperatively by intermittent morphine and diazepam. Hormonal and metabolic responses to surgery were evaluated by assay of arterial blood samples obtained before, during, and after the operations.

RESULTS

The neonates who received deep anesthesia (with sufentanil) had significantly reduced responses of beta-endorphin, norepinephrine, epinephrine, glucagon, aldosterone, cortisol, and other steroid hormones; their insulin responses and ratios of insulin to glucagon were greater during the operation. The neonates who received lighter anesthesia (with halothane plus morphine) had more severe hyperglycemia and lactic acidemia during surgery and higher lactate and acetoacetate concentrations postoperatively (P less than 0.025). The group that received deep anesthesia had a decreased incidence of sepsis (P = 0.03), metabolic acidosis (P less than 0.01), and disseminated intravascular coagulation (P = 0.03) and fewer postoperative deaths (none of 30 given sufentanil vs. 4 of 15 given halothane plus morphine, (P less than 0.01).

CONCLUSIONS

In neonates undergoing cardiac surgery, the physiologic responses to stress are attenuated by deep anesthesia and postoperative analgesia with high doses of opioids. Deep anesthesia continued postoperatively may reduce the vulnerability of these neonates to complications and may reduce mortality.

Hormonal-metabolic stress responses in neonates undergoing cardiac surgery

Hormonal and metabolic responses were measured in 15 neonates who underwent repair of complex congenital heart defects during a standardized anesthetic protocol. Four of the 15 neonates died postoperatively in the intensive care unit. Analysis of arterial plasma samples obtained before, during, and 24 h after surgery showed that plasma epinephrine, norepinephrine, cortisol, glucagon, and beta endorphin increased in all patients (P less than 0.05). Insulin levels increased only at the end of surgery but remained elevated for 24 h postoperatively (P less than 0.02). Intraoperative metabolic changes were characterized by hyperglycemia and lactic acidemia that persisted postoperatively. This pattern of neonatal stress responses is distinct from and more extreme than that seen in adult cardiac surgical patients. The four neonates who died postoperatively tended to have higher stress responses intra- and postoperatively despite having been indistinguishable from survivors by the usual clinical and hemodynamic criteria. These preliminary results suggest that neonatal hormonal and metabolic responses to cardiac surgical operations in neonates are extreme and are associated with a high hospital mortality rate.

Neonatal stress responses to anesthesia and surgery

Neonatal stress responses have been investigated only in recent years. Term neonates mount substantial hormonal and metabolic responses, which are distinct from those of adult patients. These responses can be altered significantly by the effects of prematurity, the effects of graded surgical stress, and the anesthetic techniques used during surgery. In addition, neonatal stress responses may have important implications for the clinical outcome following surgery in neonates.

The neuroanatomy, neurophysiology, and neurochemistry of pain, stress, and analgesia in newborns and children

Beginning with a brief description of mature anatomic pathways and neurotransmitters in the "pain system," this article details their development in the human fetus, neonate, and child. Special emphasis is given to the basic mechanisms and physiologic effects of opioid analgesia. The clinical implications of these data are described, particularly with regard to the maintenance of cardiovascular stability and hormonal-metabolic homeostasis in newborns and children undergoing surgery or other forms of stress.

Management of pain in the postoperative neonate

Only recently has the use of anesthesia and analgesia become widely accepted in the newborn infant. This is largely a result of the overwhelming evidence that neonates have the neurologic substrate for the perception of pain and display characteristic behavioral, physiologic, metabolic, and hormonal responses to noxious stimuli. The management of postoperative pain in the surgical neonate begins in the operating room, where techniques can be chosen that will ease the transition into the postoperative period. For postoperative analgesia, the most widely used and effective agents are the narcotics morphine and fentanyl. They may be administered either intermittently or continuously, and with proper precautions may be given to both intubated and nonintubated newborns. Other medications for analgesia and sedation are not as well studied in the newborn, but chloral hydrate and the benzodiazepines are useful for sedation, and acetaminophen may be used for analgesia alone or for potentiating the effect of narcotics. In addition, a number of creative nonpharmacologic techniques are being developed and promise to further decrease the discomfort experienced by postoperative neonates.

The ontogeny of the metabolic and endocrine stress response in the human fetus, neonate and child

Evidence of an endocrine and metabolic response to stress is evident from the mid trimester of fetal life. The ontogeny of this response is seen in the different patterns of response evident in the fetus, neonate, infant and child. These data raise important issues concerning the management of pain and stress in early life.

Antenatal fetal heart rate variation in relation to the respiratory and metabolic status of the compromised human fetus

Three groups of women were delivered by caesarean section before labour: for an abnormal fetal heart rate (FHR) trace (21 cases, group 1), or for maternal deterioration in severe pre-eclampsia without gross fetal heart rate abnormalities (20 cases, group 2), or to avoid mechanical difficulties in labour at term (30 cases, group 3). The mean gestational ages of the first two groups were 32 weeks with a high proportion of infants small-for-gestational-age. In group 1, FHR variation (mean range of pulse intervals) was less than half (20.6 SE 1.2 ms) of the normal value at the same age (44.4 SE 1.5 ms). This was associated with hypoxaemia (mean umbilical artery PO2 of 6 mmHg at delivery), with evidence of compensation shown by an elevated amniotic fluid erythropoietin. The fetuses were hypoglycaemic and had greater umbilical artery blood alanine concentrations, but no large changes in adenine nucleotide or endorphin plasma concentrations. Although there was a minor degree of respiratory acidaemia at birth, there was not significant metabolic acidaemia. The results demonstrate that the reduced variation of 'suboptimal' and 'decelerative' fetal heart rate records is associated with fetal hypoxaemia and evidence of nutritional deprivation, but not with asphyxia.

Measuring the severity of surgical stress in newborn infants

Measurement of the severity of surgery would greatly facilitate the design and interpretation of studies in neonates undergoing surgery. A scoring method, based on the amount of blood loss, superficial dissection, and visceral trauma, the site and duration of surgery, cardiac surgical factors, and associated stress factors for surgical neonates, was formulated and applied to 94 neonates undergoing surgery. Perioperative management was standardized for all patients and hormonal-metabolic variables were measured in blood samples drawn preoperatively at the end of the operation, and at six, 12, and 24 hours after operation. The stress scores were correlated significantly with the plasma epinephrine (P less than .0001), norepinephrine (P less than .0001), insulin (P less than .001), glucagon (P less than .005), and cortisol (P less than .02) responses, and with changes in blood glucose (P less than .0001), lactate (P less than .0001), pyruvate (P less than .0001), and alanine (P less than .005) during and after operation. Discriminant function analysis was used for further validation and this scoring method was found to predict accurately the severity of surgical stress in 89.4% cases. Discrepancies in the remaining cases were found to be related to specific clinical factors. On comparison of the hormonal and metabolic responses of neonates in the minor (N = 71), moderate (N = 12), and severe (N = 11) stress groups, increasing severity of surgical stress was found to be associated with greater and more prolonged changes in plasma catecholamines, blood glucose, and gluconeogenic substrates during and after operation. Clinical outcome following operation was also significantly different between the three stress groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Does halothane anaesthesia decrease the metabolic and endocrine stress responses of newborn infants undergoing operation?

Concern about the side effects of various anaesthetic agents in newborn infants has led to the widespread use of anaesthesia with unsupplemented nitrous oxide and oxygen with muscle relaxants in such patients. To investigate the efficacy of such a regimen 36 neonates undergoing operations were randomised to two groups: one group received anaesthesia with nitrous oxide and curare alone and the other was additionally given halothane. Concentrations of metabolites and hormones were measured before and at the end of operation and at six, 12, and 24 hours after operation and the values compared between the two groups. Neonates given halothane anaesthesia showed decreased hormonal responses to operation, with significant differences between the two groups in the changes in adrenaline, noradrenaline, and cortisol concentrations and the ratio of insulin to glucagon concentration. Changes in blood concentrations of glucose and total ketone bodies and plasma concentrations of non-esterified fatty acids were also decreased in neonates receiving halothane anaesthesia. Neonates given anaesthesia with unsupplemented nitrous oxide showed significantly greater increases in the urinary ratio of 3-methylhistidine to creatinine concentration and their clinical condition was also more unstable during and after operation. Unless specifically contraindicated potent anaesthesia with halothane or other anaesthetic agents should be given to all neonates undergoing surgical operations as it decreases their stress responses and improves their clinical stability during and after operation.

Randomised trial of fentanyl anaesthesia in preterm babies undergoing surgery: effects on the stress response

In a randomised controlled trial, preterm babies undergoing ligation of a patent ductus arteriosus were given nitrous oxide and d-tubocurarine, with (n = 8) or without (n = 8) the addition of fentanyl (10 micrograms/kg intravenously) to the anaesthetic regimen. Major hormonal responses to surgery, as indicated by changes in plasma adrenaline, noradrenaline, glucagon, aldosterone, corticosterone, 11-deoxycorticosterone, and 11-deoxycortisol levels, in the insulin/glucagon, molar ratio, and in blood glucose, lactate, and pyruvate concentrations were significantly greater in the non-fentanyl than in the fentanyl group. The urinary 3-methylhistidine/creatinine ratios were significantly greater in the non-fentanyl group on the second and third postoperative days. Compared with the fentanyl group, the non-fentanyl group had circulatory and metabolic complications postoperatively. The findings indicate that preterm babies mount a substantial stress response to surgery under anaesthesia with nitrous oxide and curare and that prevention of this response by fentanyl anaesthesia may be associated with an improved postoperative outcome.

Randomised trial of fentanyl anaesthesia in preterm babies undergoing surgery: effects on the stress response

In a randomised controlled trial, preterm babies undergoing ligation of a patent ductus arteriosus were given nitrous oxide and d-tubocurarine, with (n = 8) or without (n = 8) the addition of fentanyl (10 micrograms/kg intravenously) to the anaesthetic regimen. Major hormonal responses to surgery, as indicated by changes in plasma adrenaline, noradrenaline, glucagon, aldosterone, corticosterone, 11-deoxycorticosterone, and 11-deoxycortisol levels, in the insulin/glucagon, molar ratio, and in blood glucose, lactate, and pyruvate concentrations were significantly greater in the non-fentanyl than in the fentanyl group. The urinary 3-methylhistidine/creatinine ratios were significantly greater in the non-fentanyl group on the second and third postoperative days. Compared with the fentanyl group, the non-fentanyl group had circulatory and metabolic complications postoperatively. The findings indicate that preterm babies mount a substantial stress response to surgery under anaesthesia with nitrous oxide and curare and that prevention of this response by fentanyl anaesthesia may be associated with an improved postoperative outcome.

Can the human neonate mount an endocrine and metabolic response to surgery?

Little is known of the ability of the human newborn infant to mount an endocrine and metabolic response to surgical trauma. Blood concentrations of glucose, lactate, pyruvate, alanine, hydroxybutyrate, acetoacetate, and glycerol together with plasma concentrations of insulin, glucagon, adrenaline, and nonadrenaline were measured in 33 infants (26 term, 7 preterm) subjected to surgery during the neonatal period. The results show that newborn infants can indeed mount a substantial endocrine and metabolic stress response, the main features of which are hyperglycemia and hyperlactatemia associated with the release of catecholamines and the inhibition of insulin secretion. There are specific differences between preterm and term neonates and between neonates anesthetised by different anesthetic techniques in the pattern of this response.