Effects of age on the serum concentration of alpha 1-acid glycoprotein and the binding of lidocaine in pediatric patients

The regional pattern of age-related synaptic loss in the human brain differs from gray matter volume loss: in vivo PET measurement with [11C]UCB-J

PURPOSE

Aging is a major societal concern due to age-related functional losses. Synapses are crucial components of neural circuits, and synaptic density could be a sensitive biomarker to evaluate brain function. [11C]UCB-J is a positron emission tomography (PET) ligand targeting synaptic vesicle glycoprotein 2A (SV2A), which can be used to evaluate brain synaptic density in vivo.

METHODS

We evaluated age-related changes in gray matter synaptic density, volume, and blood flow using [11C]UCB-J PET and magnetic resonance imaging (MRI) in a wide age range of 80 cognitive normal subjects (21-83 years old). Partial volume correction was applied to the PET data.

RESULTS

Significant age-related decreases were found in 13, two, and nine brain regions for volume, synaptic density, and blood flow, respectively. The prefrontal cortex showed the largest volume decline (4.9% reduction per decade: RPD), while the synaptic density loss was largest in the caudate (3.6% RPD) and medial occipital cortex (3.4% RPD). The reductions in caudate are consistent with previous SV2A PET studies and likely reflect that caudate is the site of nerve terminals for multiple major tracts that undergo substantial age-related neurodegeneration. There was a non-significant negative relationship between volume and synaptic density reductions in 16 gray matter regions.

CONCLUSION

MRI and [11]C-UCB-J PET showed age-related decreases of gray matter volume, synaptic density, and blood flow; however, the regional patterns of the reductions in volume and SV2A binding were different. Those patterns suggest that MR-based measures of GM volume may not be directly representative of synaptic density.

Advances in the Management of Acute Postsurgical Pain: A Review

Despite the millions of surgeries performed every year around the world, postoperative pain remains prevalent and is often addressed with inadequate or suboptimal treatments. Chronic postsurgical pain is surprisingly prevalent, and its rate varies with the type of surgery, as well as with certain patient characteristics. Thus, better clinical training is needed as well as patient education. As pain can be caused by more than one mechanism, multimodal or balanced postsurgical analgesia is appropriate. Pharmacological agents such as opioid and nonopioid pain relievers, as well as adjuvants and nonpharmacologic approaches, can be combined to provide better and opioid-sparing pain relief. Many specialty societies have guidelines for postoperative pain management that emphasize multimodal postoperative analgesia. These guidelines are particularly helpful when dealing with special populations such as pregnant patients or infants and children. Pediatric pain control, in particular, can be challenging as patients may be unable to communicate their pain levels. A variety of validated assessment tools are available for diagnosis. Related to therapy, most guidelines agree on the fact that codeine should be used with extreme caution in pediatric patients as some may be "rapid metabolizers" and its use may be life-threatening. Prehabilitation is a preoperative approach that prepares patients in advance of elective surgery with conditioning exercises and other interventions to optimize their health. Prehabilitation may have aerobic, strength-training, nutritional, and counseling components. Logistical considerations and degree of patient adherence represent barriers to effective prehabilitation programs. Notwithstanding all this, acute postoperative pain represents a clinical challenge that has not yet been well addressed.

Local anesthetics systemic toxicity in children: analysis of the French pharmacovigilance database

PURPOSE

To characterize clinical profile of pediatric local anesthetic (LA) systemic toxicity (LAST) and to identify determinants of life-threatening outcomes.

METHODS

Spontaneous reports notified to the French Pharmacovigilance Network were retrieved and followed by a case-by-case review, according to the following criteria: LA as suspected drug, age < 18 years, adverse drug reactions related to nervous system, cardiac, respiratory, psychiatric or general disorders. Multivariate logistic regression analysis was performed to identify factors leading to life-threatening reaction (i.e. continuous seizures or cardiorespiratory arrest).

RESULTS

Among 512 cases retrieved, 64 LAST cases were included (neonates 11%, infants 30%, children 36%, adolescents 23%) mainly involving lidocaine (47%), lidocaine + prilocaine (22%) and ropivacaine (14%). Toxicity profiles were neurological (58%), cardiac (11%) or mixed (20%) and 7 patients (11%) developed methemoglobinemia. LAST was life-threatening for 23 patients (36%) and 2 patients died. Doses were above recommendations in 26 patients (41%) and were not different between life-threatening and non-life-threatening cases. The context of use (general and orthopedic surgery, p = 0.006) and the type of LA agent (lidocaine, p = 0.016) were independently associated with a life-threatening outcome.

CONCLUSION

In this national retrospective analysis, LAST in children appear to be a rare event. Neurological and cardiac signs were the most frequently reported reactions. LAST in children can be life-threatening, even at therapeutic doses. Although a fatal outcome may anecdotally occur, the vast majority of patients recovered after appropriate medical care.

Estimation of Pediatric Dosage of Antimalarial Drugs, Using Pharmacokinetic and Physiological Approach

Most of the individuals who die of malaria in sub-Saharan Africa are children. It is, therefore, important for this age group to have access to the right treatment and correct dose. Artemether-lumefantrine is one of the fixed dose combination therapies that was approved by the World Health Organization to treat malaria. However, the current recommended dose has been reported to cause underexposure or overexposure in some children. The aim of this article was, therefore, to estimate the doses that can mimic adult exposure. The availability of more and reliable pharmacokinetic data is essential to accurately estimate appropriate dosage regimens. The doses in this study were estimated using the physiological information from children and some pharmacokinetic data from adults due to the lack of pediatric pharmacokinetic data in the literature. Depending on the approach that was used to calculate the dose, the results showed that some children were underexposed, and others were overexposed. This can lead to treatment failure, toxicity, and even death. Therefore, when designing a dosage regimen, it is important to know and include the distinctions in physiology at various phases of development that influence the pharmacokinetics of various drugs in order to estimate the dose in young children. The physiology at each time point during the growth of a child may influence how the drug is absorbed, gets distributed, metabolized, and eliminated. From the results, there is a very clear need to conduct a clinical study to further verify if the suggested (i.e., 0.34 mg/kg for artemether and 6 mg/kg for lumefantrine) doses could be clinically efficacious.

Evolving approaches in neonatal postoperative pain management

Neonates experience significant moderate and severe postoperative pain. Effective postoperative pain management in neonates is required to minimize acute and long-term effects of neonatal pain. Protecting the developing nervous system from persistent sensitization of pain pathways and developing primary hyperalgesia is essential. Opioids and acetaminophen are commonly analgesics used for pain control. Regional anesthesia provides adequate intraoperative and postoperative analgesia in neonates. It decreases exposure to opioids, reduces adverse drug effects, and facilitates early extubation. It suppresses the stress response and can prevent long-term behavioral responses to pain. The most common blocks performed in neonates are neuraxial blocks. Using ultrasound increased the number of peripheral nerve blocks performed in neonates. Recently, various peripheral nerve blocks (paravertebral, transverse abdominis plane, rectus sheath, quadratus lumborum, erector spinae plane blocks) were safely used. Many studies support analgesic efficacy but highlight neonates' unpredictability and variability of fascial blocks.

Population Pharmacokinetic Properties of Antituberculosis Drugs in Vietnamese Children with Tuberculous Meningitis

Optimal dosing of children with tuberculous meningitis (TBM) remains uncertain and is currently based on the treatment of pulmonary tuberculosis in adults. This study aimed to investigate the population pharmacokinetics of isoniazid, rifampin, pyrazinamide, and ethambutol in Vietnamese children with TBM, to propose optimal dosing in these patients, and to determine the relationship between drug exposure and treatment outcome. A total of 100 Vietnamese children with TBM were treated with an 8-month antituberculosis regimen.

Optimal dosing of children with tuberculous meningitis (TBM) remains uncertain and is currently based on the treatment of pulmonary tuberculosis in adults. This study aimed to investigate the population pharmacokinetics of isoniazid, rifampin, pyrazinamide, and ethambutol in Vietnamese children with TBM, to propose optimal dosing in these patients, and to determine the relationship between drug exposure and treatment outcome. A total of 100 Vietnamese children with TBM were treated with an 8-month antituberculosis regimen. Nonlinear mixed-effects modeling was used to evaluate the pharmacokinetic properties of the four drugs and to simulate different dosing strategies. The pharmacokinetic properties of rifampin and pyrazinamide in plasma were described successfully by one-compartment disposition models, while those of isoniazid and ethambutol in plasma were described by two-compartment disposition models. All drug models included allometric scaling of body weight and enzyme maturation during the first years of life. Cerebrospinal fluid (CSF) penetration of rifampin was relatively poor and increased with increasing protein levels in CSF, a marker of CSF inflammation. Isoniazid and pyrazinamide showed good CSF penetration. Currently recommended doses of isoniazid and pyrazinamide, but not ethambutol and rifampin, were sufficient to achieve target exposures. The ethambutol dose cannot be increased because of ocular toxicity. Simulation results suggested that rifampin dosing at 50 mg/kg of body weight/day would be required to achieve the target exposure. Moreover, low rifampin plasma exposure was associated with an increased risk of neurological disability. Therefore, higher doses of rifampin could be considered, but further studies are needed to establish the safety and efficacy of increased dosing.

Pharmacotherapy of neonatal opioid withdrawal syndrome: a review of pharmacokinetics and pharmacodynamics

INTRODUCTION

Neonatal opioid withdrawal syndrome (NOWS) often arises in infants born to mothers who used opioids during pregnancy. Morphine, methadone, and buprenorphine are the most common first-line treatments, whereas clonidine and phenobarbital are generally reserved for adjunctive therapy. These drugs exhibit substantial pharmacokinetic (PK) and pharmacodynamic (PD) variability. Current pharmacological treatments for NOWS are based on institutional protocols and largely rely on empirical treatment of patient symptoms.

AREAS COVERED

This article reviews the PK/PD of NOWS pharmacotherapies with a focus on the implication of physiological development and maturation. Body size-standardized clearance is consistently low in neonates, except for methadone. This can be ascribed to underdeveloped metabolic and elimination pathways. The effects of pharmacogenetics have been clarified especially for morphine. The PK/PD relationship of medications used in the treatment of NOWS is generally understudied.

EXPERT OPINION

Providing an appropriate opioid dose in neonates is challenging. Advancements in quantitative pharmacology and PK/PD modeling approaches facilitate identification of key factors driving PK/PD variability and characterization of exposure-response relationships. PK/PD model-informed simulations have been widely employed to define age-appropriate pediatric dosing regimens. The model-informed approach holds promise to aid more rational use of medications in the treatment of NOWS.

Updates on neurologic complications in pediatric regional anesthesia

Regional anesthesia has grown in popularity as a multimodal approach to analgesia. However, some anesthesiologists are fearful of regional blocks in pediatric patients as most require general anesthesia. One of the most alarming complications is neurologic injury. While there are limited case reports regarding the devastating neurologic injuries in pediatric patients, review of large databases has shown a level of safety in pediatric regional anesthesia that is comparable to that in adult patients. This review aimed to provide an update on the relevant literature regarding neurologic complications and the safety of regional blocks in pediatric patients. These large data sets have confirmed that regional anesthesia is a useful and safe modality in pediatric patients.

A Review of Regional Anesthesia in Infants

Regional anesthesia provides effective anesthesia and pain relief in infants with age-specific data attesting to safety and efficacy. Regional anesthesia decreases exposure to opioids and general anesthetic agents and associated adverse drug effects, suppresses the stress response, and provides better hemodynamic stability compared to general anesthesia. Regional anesthesia can prevent long-term behavioral responses to pain. As a result, the overall number and variety of nerve blocks being used in infants is increasing. While neuraxial blocks are the most common blocks performed in infants, the introduction of ultrasound imaging and a better safety profile has advanced the use of peripheral nerve blocks. Infant-specific pharmacokinetic and pharmacodynamic data of local anesthetic medications are reviewed including risk factors for the accumulation of high serum levels of unbound, pharmacologically active drug. Bupivacaine accumulates with continuous infusion and 2-chloroprocaine can be used as an alternative. Local anesthetic systemic toxicity has the highest incidence in infants less than 6 months of age and is associated with bolus dosing and penile nerve blocks. Local anesthetic toxicity is treated by securing the airway, suppression of seizure activity and implementation of cardiopulmonary resuscitation. Administration of intralipid (intravenous lipid emulsion) is initiated at the first sign of toxicity. A high level of expertise in regional anesthesia is needed when treating infants due to their unique development.

Pharmacokinetic and Pharmacodynamic Considerations for Drugs Binding to Alpha-1-Acid Glycoprotein

According to the free drug hypothesis only the unbound drug is available to act at physiological sites of action, and as such the importance of plasma protein binding primarily resides in its impact on pharmacokinetics and pharmacodynamics. Of the major plasma proteins, alpha-1-acid glycoprotein (AAG) represents an intriguing one primarily due to the high affinity, low capacity properties of this protein. In addition, there are marked species and age differences in protein expression, homology and drug binding affinity. As such, a thorough understanding of drug binding to AAG can help aid and improve the translation of pharmacokinetic/pharmacodynamic (PK/PD) relationships from preclinical species to human as well as adults to neonates. This review provides a comprehensive overview of our current understanding of the biochemistry of AAG; endogenous function, impact of disease, utility as a biomarker, and impact on PK/PD. Experimental considerations are discussed as well as recommendations for understanding the potential impact of AAG on PK through drug discovery and early development.

Improving Pediatric Protein Binding Estimates: An Evaluation of α1-Acid Glycoprotein Maturation in Healthy and Infected Subjects

BACKGROUND

Differences in plasma protein levels observed between children and adults can alter the extent of xenobiotic binding in plasma, resulting in divergent patterns of exposure.

OBJECTIVE

This study aims to quantify the ontogeny of α1-acid glycoprotein in both healthy and infected subjects.

METHODS

Data pertaining to α1-acid glycoprotein from healthy subjects were compiled over 26 different publications. For subjects diagnosed or suspected of infection, α1-acid glycoprotein levels were obtained from 214 individuals acquired over three clinical investigations. The analysis evaluated the use of linear, power, exponential, log-linear, and sigmoid E max models to describe the ontogeny of α1-acid glycoprotein. Utility of the derived ontogeny equation for estimation of pediatric fraction unbound was evaluated using average-fold error and absolute average-fold error as measures of bias and precision, respectively. A comparison to fraction unbound estimates derived using a previously proposed linear equation was also instituted.

RESULTS

The sigmoid E max model provided the comparatively best depiction of α1-acid glycoprotein ontogeny in both healthy and infected subjects. Despite median α1-acid glycoprotein levels in infected subjects being more than two-fold greater than those observed in healthy subjects, a similar ontogeny pattern was observed when levels were normalized toward adult levels. For estimation of pediatric fraction unbound, the α1-acid glycoprotein ontogeny equation derived from this work (average fold error 0.99; absolute average fold error 1.24) provided a superior predictive performance in comparison to the previous equation (average fold error 0.74; absolute average fold error 1.45).

CONCLUSION

The current investigation depicts a proficient modality for estimation of protein binding in pediatrics and will, therefore, aid in reducing uncertainty associated with pediatric pharmacokinetic predictions.

Plasma concentrations of alpha-1-acid glycoprotein in preterm and term newborns: influence of mode of delivery and implications for plasma protein binding of local anaesthetics

BACKGROUND

Alpha-1-acid glycoprotein (AAGP) is an acute-phase protein with high affinity for amide local anaesthetics (LAs), and a major determinant of free and potentially toxic concentrations of LAs in plasma. Neonates are known to have lower plasma concentrations of AAGP than adults, and are at risk of developing high free concentrations of LAs. Data regarding AAGP in newborns are so far sparse. The aim of this study was to determine plasma concentrations of AAGP after delivery of preterm and term infants, and to investigate correlations between AAGP and gestational age, birth weight, gender, and mode of delivery.

METHODS

In this prospective observational study, blood was sampled from umbilical cords of 70 newborn infants born at gestational weeks 27-42 immediately after delivery. Blood samples were subsequently analysed for AAGP plasma concentrations with an immunoturbidimetric assay.

RESULTS

We found higher concentrations of AAGP in infants born vaginally compared with those who were delivered by elective Caesarean section [median (inter-quartile range) 0.189 g litre^-1 (0.142-0.263 g litre^-1) vs 0.110 g litre^-1 (0.094-0.157 g litre^-1; P=0.0003)], respectively. There was a correlation between gestational age and AAGP concentrations (r=0.50; P=0.011), with significantly higher concentrations in the more mature infants. Gender and birth weight did not appear to influence the plasma concentrations of AAGP.

CONCLUSIONS

Alpha-1-acid glycoprotein concentrations in newborns are influenced both by gestational age and mode of delivery. Thus, when dosing local anaesthetics in a parturient, these factors should be taken into account.

Melatonin Pharmacokinetics Following Oral Administration in Preterm Neonates

Melatonin possesses potential efficacy in perinatal brain injuries, and has been proposed as adjunctive pharmacological therapy in combination with hypothermia in the clinical setting. However, the pharmacokinetics of melatonin in preterm and term newborns is still unknown. The aim of this study was to analyze the pharmacokinetics of melatonin after intragastric administration in preterm infants. Preterm newborns were enrolled 24–72 h after birth, and randomly assigned to three groups receiving a single bolus of 0.5 mg·kg⁻¹ melatonin, or 3 boluses of 1 or 5 mg·kg⁻¹ of melatonin at 24-h intervals. Blood samples were collected before and at selective times after melatonin administration. The half-life of melatonin in plasma ranged from 7.98 to 10.94 h, and the area under the curve (AUC) from 10.48 to 118.17 µg·mL⁻¹·h⁻¹. Our results indicate a different pharmacokinetic profile in premature newborns, compared to adults and experimental animals. The high peak plasma concentrations and the long half-life indicate that in the neonatal clinical setting, it is possible to obtain and maintain high serum concentrations using a single administration of melatonin repeated every 12/24 h.

Clindamycin Pharmacokinetics and Safety in Preterm and Term Infants

Clindamycin may be active against methicillin-resistant Staphylococcus aureus, a common pathogen causing sepsis in infants, but optimal dosing in this population is unknown. We performed a multicenter, prospective pharmacokinetic (PK) and safety study of clindamycin in infants. We analyzed the data using a population PK analysis approach and included samples from two additional pediatric trials. Intravenous data were collected from 62 infants (135 plasma PK samples) with postnatal ages of <121 days (median [range] gestational age of 28 weeks [23 to 42] and postnatal age of 17 days [1 to 115]). In addition to body weight, postmenstrual age (PMA) and plasma protein concentrations (albumin and alpha-1 acid glycoprotein) were found to be significantly associated with clearance and volume of distribution, respectively. Clearance reached 50% of the adult value at PMA of 39.5 weeks. Simulated PMA-based intravenous dosing regimens administered every 8 h (≤32 weeks PMA, 5 mg/kg; 32 to 40 weeks PMA, 7 mg/kg; >40 to 60 weeks PMA, 9 mg/kg) resulted in an unbound, steady-state concentration at half the dosing interval greater than a MIC for S. aureus of 0.12 μg/ml in >90% of infants. There were no adverse events related to clindamycin use. (This study has been registered at ClinicalTrials.gov under registration no. NCT01728363.).

Ontogeny of plasma proteins, albumin and binding of diazepam, cyclosporine, and deltamethrin

BACKGROUND

To characterize the ontogeny of plasma albumin and total proteins, due to the lack of a comprehensive pediatric database. Secondly, to establish the magnitude and duration of maturational changes in binding of highly-bound drugs/chemicals.

METHODS

Anonymized plasma samples from 296 donors were pooled in 6 age brackets from birth to adolescence. Total protein and albumin levels were measured in each age group, as was the age-dependency of plasma binding of diazepam (DZP), cyclosporine (CYC), and deltamethrin (DLM), a pyrethroid insecticide.

RESULTS

Plasma levels of albumin and total proteins steadily increased for the first 1-3 y of life. Unbound DZP and CYC fractions were elevated three- to fourfold in neonates, but decreased to adult levels after 1 and 3 y, respectively. Unbound DLM levels exceeded those in adults for just 1 mo.

CONCLUSION

Neonates and infants under 1-3 y may be at risk from increased amounts of free drug, when given standard doses of some highly-bound drugs. Pyrethroid insecticides might be anticipated to pose increased risk for 1 mo.

Metabolomic and proteomic analysis of serum from preterm infants with necrotising entercolitis and late-onset sepsis

BACKGROUND

Necrotising enterocolitis (NEC) and late-onset sepsis (LOS) are the leading causes of death among preterm infants in the developed world. This study aimed to explore the serum proteome and metabolome longitudinally in preterm infants with NEC or LOS, matched to controls.

METHODS

Nineteen patients (10 cases, 9 controls) were included. A sample 14 d prior to and following, as well as at disease diagnosis, was included for cases. Controls had serum matched at diagnosis for corresponding case. All samples (n = 39) underwent shotgun proteomic analysis, and 37 samples also underwent metabolomics analysis using ultra performance liquid chromatography-tandem mass spectrometry.

RESULTS

The proteomic and metabolomic profiles of serum were comparable between all infants. Eight proteins were associated with NEC and four proteins were associated with LOS. C-reactive protein was increased in all NEC patients at diagnosis.

CONCLUSION

No single protein or metabolite was detected in all NEC or LOS cases which was absent from controls; however, several proteins were identified which were associated with disease status. The differing expression of these proteins between diseased infants potentially relates to differing pathophysiology of disease. Thus, it is unlikely a single biomarker exists for NEC and/or LOS.

Caudal ropivacaine and bupivacaine for postoperative analgesia in infants undergoing lower abdominal surgery

Objective:

To compare the postoperative analgesic efficacy of ropivacaine 0.175% and bupivacaine 0.175% injected caudally into infants for lower abdominal surgery.

Methods:

Eighty infants, aged 3-12 months, ASA I-II scheduled to undergo lower abdominal surgery were randomly allocated to one of the two groups: Group R received 1ml.kg^-1 0.175% ropivacaine and Group B received 1ml.kg^-1 0.175% bupivacaine via caudal route. Postoperative analgesia, sedation and motor block were evaluated with modified objective pain scale, three-point scale and modified Bromage scale respectively. Postoperative measurements including mean arterial pressure (MAP), heart rate (HR), pain (OPS), sedation and motor block score were recorded for four hours in the postoperative recovery room. Parents were contacted by telephone after 24 hours to question duration of analgesia and side effects.

Results:

No significant differences were found among the groups in demographic data, MAP, HR, OPS and sedation scores during four hours postoperatively. The duration of analgesia was 527.5±150.62 minutes in Group R, 692.77±139.01 minutes in Group B (p=0.004). Twelve (30%) patients in Group R, 16 (40%) patients in groupB needed rescue analgesics (p=0.348). Rescue analgesics were administered (1 time/2 times) (9/3) (22.5/7.5%) in Group R and 16/0 (40/0%) in Group B, where no statistically significant difference was determined between the groups (p=0.071). Motor blockade was observed in 7 (17.5%) patients in Group R, and 8 (20%) patients in Group B (p=0.774).

Conclusion:

This study indicated, that a concentration of 0.175% ropivacaine and 0.175% bupivacaine administered to the infants via caudal route both provided effective and similar postoperative pain relief in infants, who underwent lower abdominal surgery.

Population pharmacokinetic modeling and simulation of amprenavir following fosamprenavir/ritonavir administration for dose optimization in HIV infected pediatric patients

Fosamprenavir (FPV) is the phosphate ester prodrug of the HIV-1 protease inhibitor amprenavir (APV). A pediatric population pharmacokinetic model for APV was developed and simulation was used to identify dosing regimens for pediatric patients receiving FPV in combination with ritonavir (RTV) which resulted in concentrations similar to those in adults receiving FPV/RTV 700/100 mg BID. Pharmacokinetic data was obtained from HIV infected subjects aged 2 months to 18 years receiving either FPV or FPV/RTV. A two-compartment model with first order absorption and elimination was an appropriate structural model. Significant covariates in the model included RTV coadministration on clearance, fed status on bioavailability for the oral suspension, body weight on clearance and volume terms, black race on clearance, and age on clearance. The following FPV/RTV twice daily dosing regimens in pediatric patients delivered plasma APV exposure similar to adults: 45/7 mg/kg in patients weighing <11 kg, 30/3 mg/kg in patients weighing 11 to <15 kg, 23/3 mg/kg in patients weighing 15 to <20 kg, and 18/3 mg/kg in patients weighting ≥20 kg. Additionally children weighing ≥39 kg can receive the adult regimen.

Pharmacokinetic profiles of epidural bupivacaine and ropivacaine following single-shot and continuous epidural use in young infants

AIMS

The primary aim of this study was to describe the pharmacokinetics of total and unbound bupivacaine and ropivacaine following epidural bolus and infusion in neonates and young infants. Secondary aims were to investigate the influence of alpha-1-acid glycoprotein (AAG) on the concentration-time profiles and to determine the efficacy and adverse event profile of the epidural regimen.

METHODS/MATERIALS

Thirty-one infants aged 40-63 weeks of postmenstrual age (PMA) undergoing hernia repair or abdominal surgery received an epidural injection of 1.5 mg · kg(-1) bupivacaine (0.25%) or ropivacaine (0.2%) followed 2 h later by an infusion of 0.2 mg · kg(-1) · h(-1) in those undergoing abdominal surgery. Total and unbound concentrations of bupivacaine and ropivacaine were analyzed using nonmem. Hourly pain scores and adverse effects were recorded.

RESULTS

Bupivacaine data were available from 11 infants (five had infusions) and ropivacaine from 13 infants (four had infusions). Alpha-1-acid glycoprotein and total bupivacaine and ropivacaine concentrations accumulated during infusions, but unbound concentrations did not. Maximum unbound concentrations for bupivacaine and ropivacaine were 0.12 mg · l(-1) (bupivacaine) and 0.13 mg · l(-1) (ropivacaine). Typical clearance/bioavailability estimates of total (unbound) bupivacaine were 0.215 (4.65) l · h(-1) · kg(-1) and of total (unbound) ropivacaine were 0.288 (3.31) l · h(-1) · kg(-1). Pain scores requiring pain team referral occurred once with bupivacaine and four times with ropivacaine. No toxicity was observed.

CONCLUSIONS

Epidural infusions of 0.2 mg(-1) · kg(-1) · h(-1) bupivacaine or ropivacaine appeared to be well tolerated and efficacious in this population. No accumulation of unbound drug concentrations occurred.

Toxicity of local anesthetic drugs: a pediatric perspective

The main mechanism of action of local anesthetics (LA) is to block sodium channels, thereby interrupting the propagation of nerve impulses. However, this action not only is localized to the sodium channels of nerve tissues involved with pain transmission but will have its effect on any tissue containing sodium channels. Thus, if there is a rapid absorption into the systemic circulation of locally injected LA or if LA inadvertently is injected into a blood vessel, then significant blockade of sodium channels in other tissues may also be blocked and serious complications may ensue. The two most important tissues associated with systemic toxicity of LA are the central nervous and the cardiovascular systems, which may lead to seizures, tachyarrhythmias, and ultimately death from apnea and cardiovascular collapse. The aim of this communication is to elucidate some issues that are associated with toxicity of LA and its treatment in the pediatric population.

Lipid emulsion for local anesthetic systemic toxicity

The accidental overdose of local anesthetics may prove fatal. The commonly used amide local anesthetics have varying adverse effects on the myocardium, and beyond a certain dose all are capable of causing death. Local anesthetics are the most frequently used drugs amongst anesthetists and although uncommon, local anaesthetic systemic toxicity accounts for a high proportion of mortality, with local anaesthetic-induced cardiac arrest particularly resistant to standard resuscitation methods. Over the last decade, there has been convincing evidence of intravenous lipid emulsions as a rescue in local anesthetic-cardiotoxicity, and anesthetic organisations, over the globe have developed guidelines on the use of this drug. Despite this, awareness amongst practitioners appears to be lacking. All who use local anesthetics in their practice should have an appreciation of patients at high risk of toxicity, early symptoms and signs of toxicity, preventative measures when using local anesthetics, and the initial management of systemic toxicity with intravenous lipid emulsion. In this paper we intend to discuss the pharmacology and pathophysiology of local anesthetics and toxicity, and the rationale for lipid emulsion therapy.

Acute pain management in children

The greatest advance in pediatric pain medicine is the recognition that untreated pain is a significant cause of morbidity and even mortality after surgical trauma. Accurate assessment of pain in different age groups and the effective treatment of postoperative pain is constantly being refined; with newer drugs being used alone or in combination with other drugs continues to be explored. Several advances in developmental neurobiology and pharmacology, knowledge of new analgesics and newer applications of old analgesics in the last two decades have helped the pediatric anesthesiologist in managing pain in children more efficiently. The latter include administering opioids via the skin and nasal mucosa and their addition into the neuraxial local anesthetics. Systemic opioids, nonsteroidal anti-inflammatory agents and regional analgesics alone or combined with additives are currently used to provide effective postoperative analgesia. These modalities are best utilized when combined as a multimodal approach to treat acute pain in the perioperative setting. The development of receptor specific drugs that can produce pain relief without the untoward side effects of respiratory depression will hasten the recovery and discharge of children after surgery. This review focuses on the overview of acute pain management in children, with an emphasis on pharmacological and regional anesthesia in achieving this goal.

Continuous lumbar/thoracic epidural analgesia in low-weight paediatric surgical patients: practical aspects and pitfalls

PURPOSE

Continuous epidural anaesthesia attenuates perioperative stress and avoids the need for systemic opioids. In addition, it may prevent the need for postoperative mechanical ventilation. The aim of the study was to prospectively follow the perioperative course of young infants treated with continuous thoracic/lumbar epidural anaesthesia for major surgery.

METHODS

Data were collected prospectively from 44 epidural anaesthetics in 40 infants (18 premature or former premature) weighing 1,400-4,300 g who underwent major abdominal surgery (33 cases), thoracic surgery (5), or both (1), or ano-rectal surgery (5) at our centre.

RESULTS

Epidural placement was achieved easily in all cases, with high quality analgesia for 24-96 h. Tracheal extubation was delayed after 4 anaesthetics due to muscle relaxant overdose (n = 1), surgeon's request (n = 2), and systemic opioid administration before epidural anaesthesia was considered (n = 1). Intraoperative complications included haemodynamic instability (n = 1) and vascular catheter placement (n = 5). Postoperative complications included meningitis (n = 1), insertion site erythema (n = 7), apnoea (n = 6; 4 premature and 2 full-term infants) and tracheal re-intubation (n = 6).

CONCLUSIONS

Continuous epidural analgesia is effective in low-weight infants undergoing major surgery. The trachea may be extubated immediately after surgery. Attention should be paid to the unique anatomical, physiological, and pharmacological aspects. The patients should be monitored carefully for pain, respiratory failure, and meningitis (an extremely rare complication).

Perioperative anesthetic and analgesic management of newborn bladder exstrophy repair

OBJECTIVE

Reconstruction of bladder exstrophy in newborn infants requires immobilization, sedation and pain management to prevent distracting forces from compromising the repair. We present a 6-year review of our experience.

SUBJECTS AND METHODS

We reviewed the perioperative management of newborn infants undergoing reconstruction between November 1999 and October 2006. Data are presented as means+/-SD.

RESULTS

Twenty-three newborn infants underwent surgery under a combined epidural and general anesthetic technique. Tunneled caudal epidural catheters were inserted in all patients and intermittently injected with 0.25% bupivacaine with 1:200,000 epinephrine. Postoperatively, a continuous infusion of 0.1% lidocaine, 0.8-1mg/kg/h was administered for 15+/-8 (range 4-30) days. Children were sedated with diazepam for 20+/-13 (range 2-40) days. Central venous catheters were maintained for 20+/-9 (range 1-34) days for fluids, drug administration and blood sampling. No patient experienced bladder prolapse or wound dehiscence.

CONCLUSION

Perioperative management with tunneled epidural and central venous catheters in newborn infants with bladder exstrophy facilitates immobilization, analgesia and sedation, resulting in an excellent cosmetic repair with no case of bladder prolapse or wound dehiscence.

Are one or two dangerous? Quinine and quinidine exposure in toddlers

Quinine and quinidine have been cited as drugs that may cause significant morbidity and mortality in toddlers who ingest one or two pills. The use of both of these drugs has declined in the United States since the 1980s. A review of the literature and Poison Control data reveals that large quinine and quinidine ingestions, although rare in this country, may lead to severe toxicity and death related to cardiovascular and neurological effects in both children and adults. Although the majority of cases of quinine and quinidine toxicity in toddlers occur after ingestions of more than two pills, a single report each of severe toxicity after the equivalent of an ingestion of two pills or less by a toddler exists for both quinine and quinidine. Although the risk to the toddler exposed to one or two tablets seems to be small, triage to an Emergency Department is warranted after quinidine ingestion of any amount and after quinine ingestion that exceeds the age-appropriate therapeutic dose.

Caudal Regional Anesthesia, Ropivacaine Concentration, Postoperative Analgesia, and Infants

In this randomized, double-blind trial we evaluated the quality and duration of analgesia and motor effects after caudal block using 1 mL/kg of ropivacaine 0.1% (Group 1), 0.15% (Group 2), 0.175% (Group 3) compared to 0.2% (Group 4) in infants 1-12 mo old. Postoperatively, the number of infants who received pain medication differed among the groups (P < 0.0005). There were more infants in Groups 1 and 2 compared with Group 4 and there was no difference between Groups 3 and 4. In the postanesthesia care unit, infants in Groups 1 and 2 received more pain medication than did those in Group 4 (P = 0.0098). In the day surgery unit, there was a significant difference among the groups (P = 0.0326); infants in Groups 3 and 4 required no pain medication. The analgesia duration differed among the groups (P = 0.034). Infants in Groups 1 and 2 had a shorter duration, and there was no difference between Groups 3 and 4. Infants in Group 4 took longer to regain their motor power compared with those in Group 3 (P = 0.0347). We conclude that in infants, ropivacaine 0.175% provided postoperative analgesia and duration similar to that of ropivacaine 0.2%, whereas ropivacaine 0.1% and 0.15% did not, and it was associated with fewer motor effects.

Postoperative pain management in children

There is increased awareness of the need for effective postoperative analgesia in infants and young children. A multi-modal approach to preventing and treating pain usually is used. Mild analgesics, local and regional analgesia, and opioids when indicated, frequently are combined to minimize adverse effects of individual drugs or techniques.

Pain and stress in the human fetus

It is not known if the fetus can actually feel pain, but noxious stimulation during fetal life does cause detectable stress responses. These responses cause both short and long-term changes in the central nervous system, which can affect subsequent pain behaviour. Reducing the stress response is known to be beneficial in children and adults and recent evidence suggests this is also true for the fetus. However, the optimal amount of suppression required and the best method of achieving this (opioid or regional anaesthesia techniques) remain unknown. Prevention and treatment of pain is a basic human right, regardless of age, and if the technique of fetal surgery is to progress then a greater understanding of nociception and the stress response is required.

Benefit and risks of local anesthetics in infants and children

Regional anesthesia has become a routine part of the practice of anesthesiology in infants and children. Local anesthetic toxicity is extremely rare in infants and children; however, seizures, dysrhythmias, cardiovascular collapse, and transient neuropathic symptoms have been reported. Infants and children may be at increased risk from local anesthetics compared with adults. Larger volumes of local anesthetics are used for epidural anesthesia in infants and children than in adults. Metabolism and elimination of local anesthetics can be delayed in neonates, who also have decreased plasma concentrations of alpha(1)-acid glycoprotein, leading to increased concentrations of unbound bupivacaine. Most regional anesthetic procedures in infants and children are performed with the patient heavily sedated or anesthetized; because of this, and because a test dose is not a particularly sensitive marker of intravenous injection in the anesthetized patient, detection of intravascular local anesthetic injection is extremely difficult. The same local anesthetics used in adult anesthetic practice are also used in infants and children. Because of its extremely short duration of action, chloroprocaine has been used primarily for continuous epidural techniques in infants and children. The use of tetracaine has generally been limited to spinal and topical anesthesia. Lidocaine (lignocaine) has been used extensively in infants and children for topical, regional, plexus, epidural and spinal anesthesia. The association between prilocaine and methemoglobinemia has generally restricted prilocaine use in infants and children to the eutectic mixture of local anesthetics (EMLA). Because of its greater degree of motor block compared with other long-acting local anesthetics, etidocaine has generally been limited to plexus blocks in infants and children. Mepivacaine has been used for both plexus and epidural anesthesia in infants and children. Because postoperative analgesia is often the primary justification for regional anesthesia in infants and children, bupivacaine, a long-acting local anesthetic, is the most commonly reported local anesthetic for pediatric regional anesthesia. Given the lower toxic threshold of bupivacaine compared with other local anesthetics, the risk-benefit ratio of bupivacaine may be greater than that of other local anesthetics. Two new enantiomerically pure local anesthetics, ropivacaine and levobupivacaine, offer clinical profiles comparable to that of bupivacaine but without its lower toxic threshold. The extreme rarity of major toxicity from local anesthetics suggests that widespread replacement of bupivacaine with ropivacaine or levobupivacaine is probably not necessary. However, there are clinical situations, including prolonged local anesthetic infusions, use in neonates, impaired hepatic metabolic function, and anesthetic techniques requiring a large mass of local anesthetic, where replacement of bupivacaine with ropivacaine, levobupivacaine or (for continuous techniques) chloroprocaine appears prudent.

Complications of neuraxial blockade

Epidural and spinal anesthesia enjoy wide usage in modern practice, and each can provide reliable and safe anesthesia. Although the techniques appear to the casual observer to require relatively straightforward technical skill, both are fraught with myriad hazards and potential complications. It is the familiarity with and the understanding of these complications that makes for safe and professional practice of these techniques.

Protein binding predictions in infants

Plasma binding protein levels are lower in the newborn than in the adult and gradually increase with age. At birth, human serum albumin (HSA) concentrations are close to adult levels (75%-80%), while alpha 1-acid glycoprotein (AAG) is initially half the adult concentration. As a result, the extent of drug binding to HSA is closer to that of the adult than are those drugs bound largely to AAG. A model that incorporates the fraction unbound in adults and the ratio of the binding protein concentration between infants and adults successfully predicted the fraction unbound in infants and children.

Plasma concentrations of ropivacaine following a single-shot caudal block of 1, 2 or 3 mg/kg in children

BACKGROUND

For documenting the properties of ropivacaine used for regional anaesthesia in children, the relationship between dose and resulting systemic exposure is essential. The aim of this pharmacokinetic part of a randomised, multicentre, double-blind study was to determine the free and total plasma levels of ropivacaine in children aged between 4 and 12 years following a single-shot caudal dose of 1, 2 or 3 mg/kg of ropivacaine for postoperative pain management.

METHOD

Following induction of a standardised general anaesthetic (halothane; nitrous oxide: oxygen 60:40), a caudal block using 1 ml/kg ropivacaine in concentrations of 1, 2 or 3 mg/ml was performed in 43 ASA I children (body weight 12-25 kg) scheduled for elective inguinal surgery. Blood samples were collected prior to and 15, 30, 45, 60 and 240 min after placement of the caudal block for determination of total and free ropivacaine plasma concentrations.

RESULTS

The peak plasma concentration of total ropivacaine, reached within 15-241 min after the block, increased in proportion to dose, with mean values at 0.27, 0.64 and 0.90 mg/l following 1, 2 and 3 mg/kg respectively. The peak plasma level of free ropivacaine also increased in a dose-proportional manner, with mean levels at 0.014, 0.030 and 0.042 mg/l. The highest individual peak plasma level of free ropivacaine was 0.070 mg/l, well below the threshold levels of CNS toxicity described in adults. No clinical signs of systemic toxicity were observed.

CONCLUSION

Following single-shot caudal doses of 1-3 mg/kg in children up to 25 kg and aged between 4 and 12 years, plasma levels of free ropivacaine increase in proportion to dose and all were shown to be within safe limits.

Pharmacokinetics and analgesic effect of ropivacaine following ilioinguinal/iliohypogastric nerve block in children

BACKGROUND

The aim was to investigate the efficacy, tolerance and pharmacokinetics of ropivavcaine when administered for ilioinguinal/iliohypogastric block in children.

METHODS

We examined the pharmacokinetics and analgesic efficacy after ilioinguinal/iliohypogastric nerve block with 3 mg.kg-1 ropivacaine 5 mg.ml-1 in 22 children, aged 1-12 years, who were scheduled for inguinal surgery. Sixteen of 22 patients had a postoperative pain score < 4 (Objective Pain Scale). Nine children were given supplementary analgesics during the first six postoperative hours.

RESULTS

The peak plasma concentration of total ropivacaine was 1.50 +/- 0.93 mg.l-1 (mean +/- SD) (range 0.64-4.77 mg.l-1) 15-64 min after the injection. The peak plasma concentration of free ropivacaine was 0.05 +/- 0.03 mg.l-1 (0.02-0.14 mg.l-1), which is well below the threshold for toxicity in adults. The terminal half-life was 2.0 +/- 0.7 h. No safety concerns or symptoms suggestive of systemic toxicity were observed.

CONCLUSION

A dose of 3 mg.kg-1 of ropivacaine given as a single ilioinguinal/iliohypogastric nerve block in 1-12-year-old children provides satisfactory postoperative pain relief, and is well tolerated.

Sedation-analgesia in the pediatric intensive care unit

The provision of sedation and analgesia is an integral aspect of the care of PICU patients. A careful systems approach to the provision of sedation and analgesia can minimize complications and maximize benefit to patients. Vigilance in monitoring and adherence to published guidelines are important for safety. Physicians must define the goals in clearly devising a plan and tailor the prescription to those goals rather than use a regimented protocol for all patients.

Human alpha-1-glycoprotein and its interactions with drugs

For about half a century, the binding of drugs to plasma albumin, the "silent receptor," has been recognized as one of the major determinants of drug action, distribution, and disposition. In the last decade, the binding of drugs, especially but not exclusively basic entities, to another plasma protein, alpha 1-acid glycoprotein (AAG), has increasingly become important in this regard. The present review points out that hundreds of drugs with diverse structures bind to this glycoprotein. Although plasma concentration of AAG is much lower than that of albumin, AAG can become the major drug binding macromolecule in plasma with significant clinical implications. Also, briefly reviewed are the physiological, pathological, and genetic factors that influence binding, the role of AAG in drug-drug interactions, especially the displacement of drugs and endogenous substances from AAG binding sites, and pharmacokinetic and clinical consequences of such interactions. It can be predicted that in the future, rapid automatic methods to measure binding to albumin and/or AAG will routinely be used in drug development and in clinical practice to predict and/or guide therapy.

Plasma concentrations and pharmacokinetics of bupivacaine with and without adrenaline following caudal anaesthesia in infants

BACKGROUND

The aim of this study was to determine whether the use of adrenaline 1/400000 added to 0.25% bupivacaine significantly delays the systemic absorption of the drug from the caudal epidural space in young infants.

METHODS

Fifteen infants less than 5 months of age undergoing minor lower abdominal procedures under a standardised general anaesthetic were randomised to receive a caudal block with either 0.25% plain bupivacaine 2.5 mg/kg (n=7) or bupivacaine 0.25% with 1/400000 adrenaline (n=8). Blood samples were drawn at 30, 60, 90, 180, 240 and 360 min according to the infant's weight and analysed for total and free bupivacaine concentrations using a gas chromatography-mass spectrometry (GC-MS) technique.

RESULTS

The total C(MAX) and T(MAX) were comparable in both groups. The total bupivacaine concentration at t=360 min was significantly higher in the "adrenaline" group compared to the "plain" group, i.e. a median (range) 742 ng/ml (372-1423 ng/ml) vs. 400.5 ng/ml (114-446 ng/ml), P=0.0080. The median "apparent" terminal half-life (t1/2) was significantly longer in the "adrenaline" group (363 min; range 238-537 min) compared to the "plain" group (n=6) (165 min; range 104-264 min), P=0.0087. The free bupivacaine concentrations (n=3 in both groups) ranged between 13 ng/ml and 52 ng/ml, corresponding to a percentage of free bupivacaine between 1.3% and 6.7%.

CONCLUSION

The addition of 1/400.000 adrenaline prolongs the systemic absorption of caudally administered bupivacaine in infants less than 5 months of age.

Ropivacaine pharmacokinetics after caudal block in 1-8 year old children

We studied the pharmacokinetics after caudal block of ropivacaine (2 mg ml-1, 1 ml kg-1) performed in 20 children aged 1-8 yr undergoing subumbilical surgery, in this open, non-comparative, multicentre study. Venous blood samples were collected up to 12-36 h. The mean (SD) peak plasma concentration, 0.47 (0.16) mg litre-1, was achieved after 12-249 min. The free fraction was 5% and the highest individual peak plasma concentration of free ropivacaine was 0.04 mg litre-1. Clearance was 7.4 (1.9) ml min-1 kg-1 and the terminal half-life 3.2 (0.8) h. Thus, the free plasma concentrations of ropivacaine were well below those associated with toxic symptoms in adults and the capacity to eliminate ropivacaine seems to be well developed in this age group. In this open study of 20 patients, ropivacaine was well tolerated and provided satisfactory postoperative pain relief without observable motor block.

Regional Anesthesia for Pain Relief in Children

Managing pain in children is a complex area that requires an understanding of the unique challenges offered by this young population. Regional anesthesia is emerging as an adjunct to pain management in children, particularly in the perioperative arena.The following article will assist the practitioner with the management of pain in children through regional techniques. Prior to the presentation of the regional techniques, an overview is presented to address the neurodevelopment of the child, the pharmacologic concerns in the younger patients, and the assessment of pain in the different age groups. Several of the commonly performed regional blocks with appropriate dosing guidelines are reviewed, with an emphasis on blocks that are more unique to the pediatric population.