Pharmacokinetics of Local Anaesthetics in Infants and Children

Incisional continuous fascia iliaca block provides more effective pain relief and fewer side effects than opioids after pelvic osteotomy in children

BACKGROUND

Intravenous opioid therapy is frequently used for postoperative pain management in children after orthopedic surgery but causes side effects such as respiratory depression, vomiting, sedation, and urinary retention. To investigate whether a continuous incisional fascia iliaca compartment (FIC) block provides more effective postoperative pain relief with fewer side effects than IV morphine, we performed a prospective, double-blind, randomized study to compare both techniques.

METHODS

Thirty children (ASA physical status I-II) aged 3 mo to 6 yr undergoing a pelvic osteotomy were included in the study. The children were randomized for either morphine IV and placebo (saline) via a FIC catheter (Group M) or placebo (saline) IV and ropivacaine via a FIC catheter (Group R). All patients received general anesthesia using inhaled sevoflurane and IV fentanyl. Perioperatively, a FIC catheter was placed by the surgeon. All patients received either a bolus dose of morphine IV (Group M) or ropivacaine 0.75% via the FIC catheter (Group R) at the end of surgery. Postoperatively, Group M received morphine IV 20 microg x kg(-1) x h(-1) and Group R ropivacaine 0.2% 0.1 mL x kg(-1) x h(-1) via the FIC catheter. In both groups, saline was administered along the other route. All children were assessed for pain, sedation, time until first oral intake, and adverse effects for 48 h postoperatively. During this period, all children had a urinary catheter.

RESULTS

The study was completed by 28 children. In the anesthetic recovery room, children in Group M had significantly higher pain scores. These children were also significantly more sedated during the study period. The incidence of vomiting did not differ between the groups; however, children in Group R had first oral intake significantly earlier than Group M. A local retrospective study revealed an incidence of urinary retention of 4.7% in the ropivacaine-treated patients and 39% in the morphine-treated patients.

CONCLUSIONS

Continuous incisional FIC block provides excellent postoperative pain relief, less sedation, and better return of appetite than morphine IV after pelvic osteotomy in children.

The effects of topical levobupivacaine on morbidity in pediatric tonsillectomy patients

OBJECTIVE

To reduce the post-tonsillectomy morbidity by swab soaked with 5 ml levobupivacaine hydroclorur (25 mg/10 ml).

STUDY DESIGN

A double-blind prospective randomized controlled clinical study.

METHODS

In this randomized double-blind study in group I (30 children, mean age 7.5+/-2.6) we tightly packed swab soaked with 5 ml levobupivacaine hydroclorur (25mg/10 ml) and in group II (21 children, mean age 7.9+/-3.7) we used 5 ml saline swabs into each of the two tonsillar fossae after tonsillectomy for 5 min. We used McGrath's face scale to compare the two groups in respect of pain control.

RESULTS

There was statistically significant pain relieving effect in the levobupivacaine group in the first 24h (p<0.05). But after 24h pain relieving effect of levobupivacaine was not significant (p>0.05). We did not see any serious complications for both groups. Postoperative morbidity mean results (nausea, vomiting, fever, bleeding, halitosis and ear pain) were not statistically different between the two groups (p>0.05).

CONCLUSION

Topical levobupivacaine seems to be a safe and easy medication for postoperative pain control in pediatric tonsillectomy patients.

Physiology-based simulations of a pathological condition: prediction of pharmacokinetics in patients with liver cirrhosis

BACKGROUND

Liver cirrhosis is a progressive disease characterized by loss of functional hepatocytes with concomitant connective tissue and nodule formation in the liver. The morphological and physiological changes associated with the disease substantially affect drug pharmacokinetics. Whole-body physiologically based pharmacokinetic (WB-PBPK) modelling is a predictive technique that quantitatively relates the pharmacokinetic parameters of a drug to such (patho-)physiological conditions.

OBJECTIVE

To extend an existing WB-PBPK model, based on the physiological changes associated with liver cirrhosis, which allows for prediction of drug pharmacokinetics in patients with liver cirrhosis.

METHODS

The literature was searched for quantitative measures of the physiological changes associated with the presence of Child-Pugh class A through C liver cirrhosis. The parameters that were included were the organ blood flows, cardiac index, plasma binding protein concentrations, haematocrit, functional liver volume, hepatic enzymatic activity and glomerular filtration rate. Predictions of pharmacokinetic profiles and parameters were compared with literature data for the model compounds alfentanil, lidocaine (lignocaine), theophylline and levetiracetam.

RESULTS

The predicted versus observed plasma concentration-time profiles for alfentanil and lidocaine were similar, such that the pharmacokinetic changes associated with Child-Pugh class A, B and C liver cirrhosis were adequately described. The theophylline elimination half-life was greatly increased in Child-Pugh class B and C patients compared with controls, as predicted by the model. Levetiracetam urinary excretion was consistently reduced with disease progression and very closely resembled observed values.

CONCLUSION

Consideration of the physiological differences between healthy individuals and patients with liver cirrhosis was important for the simulation of drug pharmacokinetics in this compromised group. The WB-PBPK model was altered to incorporate these physiological differences with the result of adequate simulation of drug pharmacokinetics. The information provided in this study will allow other researchers to further validate this liver cirrhosis model within a WB-PBPK model.

The effects of levobupivacaine versus levobupivacaine plus magnesium infiltration on postoperative analgesia and laryngospasm in pediatric tonsillectomy patients

BACKGROUND

The aim of this study was to evaluate whether the addition of magnesium to levobupivacaine will decrease the postoperative analgesic requirement or not, and to investigate the possible preventive effects on laryngospasm.

METHODS

Seventy-five children undergoing elective tonsillectomy and/or adenoidectomy surgery. The drug was prepared as only NaCl 0.9% for the first group (Group S, n=25), levobupivacaine 0.25% for the second group (Group L, n=25), and levobupivacaine 0.25% plus magnesium sulphate 2mg/kg for the third group (Group M, n=25). Pain was recorded at 15th minute, 1st, 4th, 8th, 16th, and 24th hour postoperatively. Pain was evaluated using a modified Children's Hospital of Eastern Ontario pain scale (mCHEOPS). Incidence of postoperative nausea and vomiting (PONV) was assessed at various time intervals (0-2, 2-6, 6-24h) by numeric rank score. Patients were followed for laryngospasm for 1h in recovery room after extubation. Other complications appeared within 24h postoperatively were recorded.

RESULTS

All postoperative CHEOPS values were lower than control in both groups. Analgesic requirement was decreased significantly in both groups in comparison with control patients, but this requirement was significantly lower in Group M (p<0.05). Although laryngospasm was not observed in Group M, the difference between groups was not statistically significant. PONV was similar in both groups.

CONCLUSIONS

Levobupivacaine and Levobupivacaine plus magnesium infiltration decrease the post-tonsillectomy analgesic requirement. Insignificant preventive effect of low doses of magnesium infiltration on laryngospasm observed in this study needs to be clarified by larger series.

Postoperative methemoglobinemia following infiltrative lidocaine administration for combined anesthesia in pediatric craniofacial surgery

BACKGROUND

Infiltrative anesthesia of the scalp with lidocaine was used in an attempt to reduce blood loss and anesthetic requirements during pediatric craniofacial surgery. Lidocaine, however, has the potential to cause methemoglobinemia. In this retrospective cohort-study we analyzed the incidence and effects of postoperative methemoglobinemia following subcutaneous lidocaine administration.

METHODS

During 1999-2006, 50 infants (age: 3-31 months) undergoing elective craniofacial surgery were analyzed. All infants received general anesthesia and routine monitoring, including invasive arterial blood pressure measurement. Prior to incision, the scalp was infiltrated with 6-15 ml lidocaine 1% (with epinephrine 1 : 200.000). Blood loss and blood transfusions were recorded. Methemoglobin (Met-Hb) levels were determined postoperatively using co-oximetry.

RESULTS

Twenty percent of the operated infants showed elevated Met-Hb levels (median of maximal levels: 6%; range: 2.2-18%) at admission on the PICU. In 80% of these methemoglobinemia resolved spontaneously within 12 h, only two children received methylene blue because of visible cyanosis. The intra- and postoperative course was otherwise uneventful in all the children despite significant total blood loss (median of blood loss as percentage from total estimated blood volume: 43%; range: 11-110%). Lidocaine was the only substance identified to have the potential to cause methemoglobinemia. However, the average administered dose of lidocaine was not significantly different between patients with or without methemoglobinemia (13 +/- 3.1 vs 12 +/- 3.5 mg.kg(-1); P = 0.37).

CONCLUSIONS

Even though we did not measure lidocaine plasma levels, lidocaine was the most likely cause of postoperative methemoglobinemia. Despite a high incidence, methemoglobinemia occurred sporadically and was without dangerous consequences.

Influence of pain treatment by epidural fentanyl and bupivacaine on homing of opioid-containing leukocytes to surgical wounds

Endogenous opioids released from leukocytes extravasating into injured tissue can interact with peripheral opioid receptors to inhibit nociception. Animal studies have shown that the homing of opioid-producing leukocytes to the injured site is modulated by spinal blockade of noxious input. This study investigated whether epidural analgesia (EDA) influences the migration of beta-endorphin (END) and/or met-enkephalin (ENK)-containing leukocytes into the subcutaneous wound tissue of patients undergoing abdominal surgery. In part I patients received general anesthesia combined either with intra- and postoperative EDA (with bupivacaine and fentanyl) or with postoperative patient controlled intravenous analgesia (PCIA; with the opioid piritramide). In part II patients received general anesthesia combined with either epidural fentanyl or bupivacaine which was continued postoperatively. Samples of cutanous and subcutanous tissue were taken from the wound site at the beginning, at the end and at various times after surgery, and were examined by immunohistochemistry for the presence of END and ENK. We found that (i) epidural bupivacaine, fentanyl and PCIA provided similar and clinically acceptable postoperative pain relief; (ii) compared to PCIA, epidural bupivacaine or fentanyl did not change the gross inflammatory reaction within the surgical wound; (iii) opioid-containing leukocytes were almost absent in normal subcutaneous tissue but migrated to the inflamed wound tissue in ascending numbers within a few hours, reaching a peak at about 24 h after surgery; (iv) compared to PCIA, EDA resulted in significantly decreased homing of END-containing leukocytes to the injured site at 24 h after surgery; and (v) the magnitude of this decrease was similar regardless of the epidural medication. These findings suggest that nociceptive but not sympathetic neurons are primarily involved in the attraction of opioid-containing leukocytes during early stages of inflammation.

Effects of bupivacaine, levobupivacaine and ropivacaine on myocardial relaxation

PURPOSE

Ropivacaine and levobupivacaine were developed to reduce the risk of occasional toxicity reported with bupivacaine. While the effects of long-acting local anesthetics (LAAs) on myocardial contractility (inotropy) are well described, their effects on relaxation (lusitropy) remain largely unknown. The present study aimed to compare the effects of LAAs on rat myocardium.

METHODS

Left ventricular papillary muscles of male Wistar rats were used to compare the inotropic and lusitropic responses of increasing concentrations of LAAs (10(-8) to 10(-3) M) under isometric and isotonic conditions. Data are mean % (SD) of baseline value.

RESULTS

Long-acting local anesthetics induced a significant impairment of relaxation in isotonic and isometric conditions. As compared to ropivacaine, bupivacaine and levobupivacaine induced greater negative lusitropic effects in isotony [at 10(-3) M, maximum unloaded shortening velocity ((max)Vr) = 27 +/- 11 vs 13 +/- 6 and 8 +/- 5%] and isometry (at 10(-3) M, time-to-half-relaxation: 106 +/- 10 vs 127 +/- 17 and 133 +/- 17%). When the comparison was made with equipotent concentrations, the negative lusitropic effects induced with levobupivacaine were significantly greater than those of bupivacaine and ropivacaine in isometric and isotonic conditions (at 10(-3) M, (max)Vr = 7 +/- 4 vs 13 +/- 6 and 17 +/- 4 %). As previously described, LAAs also induced concentration-dependent negative inotropic effects that were greater for levobupivacaine compared to equivalent or equipotent concentrations of bupivacaine and ropivacaine.

CONCLUSIONS

Long-acting local anesthetics induce marked negative inotropic and lusitropic effects. Among LAAs, levobupivacaine exerts the greater depressant effects. Impairment of calcium handling and sarcoplasmic reticulum could explain the differential responses to local anesthetics.

Pharmacological therapy for analgesia and sedation in the newborn

Rapid advances have been made in the use of pharmacological analgesia and sedation for newborns requiring neonatal intensive care. Practical considerations for the use of systemic analgesics (opioids, non-steroidal anti-inflammatory agents, other drugs), local and topical anaesthetics, and sedative or anaesthetic agents (benzodiazepines, barbiturates, other drugs) are summarised using an evidence-based medicine approach, while avoiding mention of the underlying basic physiology or pharmacology. These developments have inspired more humane approaches to neonatal intensive care. Despite these advances, little is known about the clinical effectiveness, immediate toxicity, effects on special patient populations, or long-term effects after neonatal exposure to analgesics or sedatives. The desired or adverse effects of drug combinations, interactions with non-pharmacological interventions or use for specific conditions also remain unknown. Despite the huge gaps in our knowledge, preliminary evidence for the use of neonatal analgesia and sedation is available, but must be combined with a clear definition of clinical goals, continuous physiological monitoring, evaluation of side effects or tolerance, and consideration of long-term clinical outcomes.

Population analysis of weight-, age-, and sex-related differences in the pharmacokinetics of lopinavir in children from birth to 18 years

The pharmacokinetics of lopinavir were investigated by the use of a population approach performed with the nonlinear mixed effect modeling program NONMEM and 157 children ranging in age from 3 days to 18 years. The pharmacokinetics of lopinavir were well described by a one-compartment model in which the absorption and the elimination rate constants were equal. Typical population estimates of the apparent volume of distribution (V/F) and plasma clearance (CL/F) were 24.6 liters and 2.58 liters/h, respectively. The lopinavir V/F and CL/F were both related to body weight (BW), with an important increase in weight-normalized CL/F for the lowest BW. Combined treatment with lopinavir and nevirapine was found to increase the CL/F. The lopinavir CL/F was also age and sex related, as a 39% increase was observed after the age of 12 years for boys compared to the CL/F for girls. The consequences of these pharmacokinetic discrepancies and the necessity to modify the currently recommended dosage regimen should be further investigated.

Ultrasound-Guided Subgluteal Sciatic Nerve Blocks with Stimulating Catheters in Children: A Descriptive Study

We describe our clinical experience of combining ultrasound guidance and nerve stimulation for the insertion of subgluteal sciatic catheters in children. Ten children scheduled for lower limb surgery with a combined general anesthetic and a subgluteal sciatic catheter placement for both operative anesthesia and postoperative pain relief were studied. Under ultrasonographic guidance the sciatic catheter was placed using an 17-gauge 50-mm Arrow continuous peripheral nerve block needle and a 19-gauge stimulating catheter (Stimucath). The minimal electrical current required for muscle contraction on the stimulating needle and catheter differed widely among patients. Based on the visualization of the spread of local anesthetic during injection through the catheter, a successful prediction for the sciatic block was made in all patients. All catheters were successfully placed and provided excellent postoperative pain relief without complications.

Levobupivacaine caudal anesthesia in children: a randomized double-blind comparison with bupivacaine

BACKGROUND

Levobupivacaine is the pure S-enantiomer of bupivacaine. Despite obvious benefits in the event of accidental intravascular injection there has been no studies demonstrating a clinically significant benefit to levobupivacaine over racemic bupivacaine for pediatric regional anesthesia. Given the similar pharmacokinetic profiles of both drugs the studies to date have been underpowered to demonstrate what is likely to be a small difference in clinical effectiveness. Our aim was to determine if there are significant differences in the clinical effectiveness of levobupivacaine compared with racemic bupivacaine for caudal anesthesia in children having lower abdominal surgery. A secondary aim was to determine if there are differences in the incidence of postoperative motor blockade between these agents.

METHODS

Three hundred and ten children ranging in age from 1 month to 10.75 years in age having lower abdominal surgery were enrolled. Patients were randomized in a double blind manner to receive a caudal block with either 0.25% bupivacaine (n = 152) or 0.25% levobupivacaine (n = 155) to a total volume of 1 ml x kg(-1). Motor blockade (modified Bromage scale) and postoperative pain or distress (FLACC behavioral scale for postoperative pain) were measured at predetermined time points during the subsequent 120 min.

RESULTS

There were no significant adverse effects attributable to levobupivacaine. Success rates were defined as a lack of hemodynamic response to first surgical incision and low postoperative pain scores. At a mean duration of 5 min between block completion and first incision success for 1 ml x kg(-1) of 0.25% bupivacaine was 91% and 94% for 0.25% levobupivacaine. Satisfactory postoperative analgesia was present in 98% of patients after bupivacaine caudal anesthesia and 97.5% for levobupivacaine. At 30 min following caudal anesthesia the incidence of postoperative motor block with racemic bupivacaine was 84% and decreased to 7% at 120 min. For levobupivacaine motor block at 30 min postcaudal was present in 85% and decreased to 11% at 120 min.

CONCLUSIONS

Levobupivacaine is an effective agent for caudal anesthesia in children at a recommended dose of 2.5 mg x kg(-1). The rapidity of onset was suitable for establishment of surgical anesthesia and postoperative analgesia was achieved in greater than 97.5% of patients. It appears to be of equivalent potency to racemic bupivacaine in children requiring lower abdominal surgery.

Some current controversies in paediatric regional anaesthesia

PURPOSE OF REVIEW

Controversial topics in paediatric regional anaesthesia are discussed.

RECENT FINDINGS

The performance of blocks under general anaesthesia, new local anaesthetics, adjuvants, location techniques, and risks of masking compartment syndromes are contemplated.

SUMMARY

The performance of regional blocks in anaesthetized patients is generally contra-indicated in adults but accepted in children. Levobupivacaine displays the same pharmacokinetic profile as racemic bupivacaine with possibly less cardiac toxicity. Ropivacaine undergoes slower absorption and, in some studies, concomitant increase in peak plasma concentration in infants. Conversely, continuous infusion of ropivacaine offers the safest therapeutic index. Many adjuvants have been used but only epinephrine, clonidine, and preservative-free ketamine offer clear advantages. Midazolam and neostigmine are effective but have potential drawbacks and raise safety questions. Needle and catheter positioning is critical. Electrocardiogram guidance and electrical stimulation occasionally help identify the migration of epidural catheters. Stimulating catheters might be useful for continuous peripheral blockade. Ultrasonography will probably become the reference technique for peripheral catheter placement. Patients at risk of compartment syndrome must be monitored (measurement of compartmental pressures); adequate pain management does not 'hide' this complication but, on the contrary, can facilitate early diagnosis since the increase in requirement for pain medication precedes other clinical symptoms by an average of 7.3 h.

Anesthesia and analgesia during and after surgery in neonates

BACKGROUND

Historically, the use of anesthetics and analgesics in neonates and infants has been based on extrapolations from studies performed in adults and older children. Over the past 20 years, there has been a growing body of research on the clinical pharmacology and clinical outcomes of these agents in neonates and infants.

OBJECTIVE

This article summarizes clinical pharmacology and clinical outcomes studies of opioids, opioid antagonists, sedative-hypnotics, nonsteroidal anti-inflammatory drugs and acetaminophen, and local anesthetics in neonates and infants to highlight gaps in the available knowledge, review some concerns about study design, and identify drugs that should receive high priority for future study.

METHODS

Relevant studies were identified through a search of MEDLINE and a review of textbooks, conference proceedings, and abstracts. The available literature was subjected to expert committee-based review.

CONCLUSIONS

There is a growing body of information on analgesic and anesthetic pharmacokinetics, pharmacodynamics, and clinical outcomes in neonates and infants, permitting safe and effective use in some clinical settings. Major gaps in knowledge persist, however. Future research may involve a combination of clinical trials and preclinical studies in suitable infant animal surrogate models.

New local anesthetics for pediatric anesthesia

PURPOSE OF REVIEW

To evaluate the relevance of new local anesthetics in pediatric regional anesthesia.

RECENT FINDINGS

Several studies evaluate the pharmacokinetics of new local anesthetics, like ropivacaine and levobupivacaine, and compare their safety and efficacy with the old but widely used bupivacaine.

SUMMARY

The goal of anesthetists using regional anesthesia is to use local anesthestics that are as safe and effective as possible, with a rapid onset and a long duration. Even though adequate dose guidelines are available, several toxic effects are reported with the use of bupivacaine in children due to inadvertent intravenous injection, long-term infusion (> 48 h) or administration in newborn babies and infants with reduced metabolism. Ropivacaine and levobupivacaine are new local anesthetics with a wider safety margin that have similar characteristics: both of them are pure S-(-)-enantiomers whose main pharmacological features are less cardio- and neuro-affinity and -toxicity in comparison with the racemic formulae and R-isomers, and a differential neural blockade with less motor than sensory block. Several clinical studies in children compare ropivacaine and levobupivacaine with bupivacaine.

Anesthésiques locaux : qu'apportent les formes lévogyres ?

The use of levobupivacaine and of ropivacaine may increase the safety of regional anaesthesia. These pure enantiomers have similar pharmacokinetic properties as those of the racemic mixtures. However, they are less cardiotoxic than the racemic mixtures, especially at the high heart rate usually encountered in infants. We may then recommend the use of these agents in the paediatric patients.

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.

Liquid chromatography–electrospray mass spectrometry determination of free and total concentrations of ropivacaine in human plasma

A specific and sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for the determination of free and total ropivacaine in human plasma. The work-up procedure involved a simple precipitation of plasma proteins with methanol. Etidocaine served as the internal standard. After microscale equilibrium-dialysis, measurement of free ropivacaine levels was performed after direct injection of the dialysate into the chromatograph. The system used a Zorbax eclipse XD8 C8 analytical column packed with 5 microm diameter particles as the stationary phase. The mobile phase consisted of a 15-min gradient (mobile phase A: 0.05% (v/v) trimethylamine in acetonitrile, mobile phase B: 2mM ammonium formate buffer (pH 3)). Mass spectrometric data were acquired in single ion monitoring mode at m/z 275 for ropivacaine and m/z 277 for etidocaine. The drug/internal standard peak area ratios (plasma) or peak areas (dialysate) were linked via a quadratic relationship to concentrations. Precision ranged from 1 to 7.6% accuracy was between 92.6 and 109%. The lower limits of quantitation were 1 microg/l in plasma and 2 microg/l in the dialysate. This method was found suitable for the analysis of plasma samples collected during a clinical trial performed in 30 infants undergoing epidural anaesthesia or continuous psoas compartment block.

A Mechanistic Approach for the Scaling of Clearance in Children

BACKGROUND AND OBJECTIVE

Clearance is an important pharmacokinetic concept for scaling dosage, understanding the risks of drug-drug interactions and environmental risk assessment in children. Accurate clearance scaling to children requires prior knowledge of adult clearance mechanisms and the age-dependence of physiological and enzymatic development. The objective of this research was to develop and evaluate ontogeny models that would provide an assessment of the age-dependence of clearance.

METHODS

Using in vitro data and/or in vivo clearance values for children for eight compounds that are eliminated primarily by one process, models for the ontogeny of renal clearance, cytochrome P450 (CYP) 3A4, CYP2E1, CYP1A2, uridine diphosphate glucuronosyltransferase (UGT) 2B7, UGT1A6, sulfonation and biliary clearance were developed. Resulting ontogeny models were evaluated using six compounds that demonstrated elimination via multiple pathways. The proportion of total clearance attributed to each clearance pathway in adults was delineated. Each pathway was individually scaled to the desired age, inclusive of protein-binding prediction, and summed to generate a total plasma clearance for the child under investigation. The paediatric age range included in the study was premature neonates to sub-adults.

RESULTS

There was excellent correlation between observed and predicted clearances for the model development (R2 = 0.979) and test sets (Q2 = 0.927). Clearance in premature neonates could also be well predicted (development R2 = 0.951; test Q2 = 0.899).

CONCLUSION

Paediatric clinical trial development could greatly benefit from clearance scaling, particularly in guiding dosing regimens. Furthermore, since the proportion of clearance via different elimination pathways is age-dependent, information could be gained on the developmental extent of drug-drug interactions.

Pain management for the hospitalized pediatric patient

Pediatric hospitalists should make pain assessment and treatment a high priority and a central part of their daily practice. Efforts at improving pain treatment in pediatric hospitals should be multidisciplinary and should involve combined use of pharmacologic and nonpharmacologic approaches. Although available information can permit effective treatment of pain for most children in hospitals, there is a need for more research on pediatric analgesic pharmacology, various nonpharmacologic treatments, and different models of delivery of care.

Pain management for pediatric thoracic surgery

PURPOSE OF REVIEW

Pain management after thoracic surgery in children presents the challenge of providing adequate analgesia without excessive sedation, and maintaining adequate respiratory function in the face of compromise resulting from existing pathology, surgical trauma, single-lung ventilation and postoperative ventilation-perfusion abnormalities. In the pediatric population, pain assessment and reporting present additional challenges. The number and complexity of surgical procedures, including video-assisted thoracoscopic procedures, is increasing in the pediatric population. There is a need to explore pain management for these types of patients.

RECENT FINDINGS

There are effective and safe strategies whereby analgesia can be provided to this pediatric population. This review will outline the progress that has been made in this field, including the use of regional techniques. The routine use of caudal catheters in neonates and infants for thoracic surgical procedures and the use of electrical guidance of epidural catheters, the 'Tsui' technique, are reviewed.

SUMMARY

These techniques, applied within a comprehensive pain management strategy, can be extremely beneficial in the care of the pediatric thoracic patient.

Use of Photoaffinity Labeling and Site-directed Mutagenesis for Identification of the Key Residue Responsible for Extraordinarily High Affinity Binding of UCN-01 in Human α1-Acid Glycoprotein

7-Hydroxystaurosporine (UCN-01) is a protein kinase inhibitor anticancer drug currently undergoing a phase II clinical trial. The low distribution volumes and systemic clearance of UCN-01 in human patients have been found to be caused in part by its extraordinarily high affinity binding to human alpha1-acid glycoprotein (hAGP). In the present study, we photolabeled hAGP with [3H]UCN-01 without further chemical modification. The photolabeling specificity of [3H]UCN-01 was confirmed by findings in which other hAGP binding ligands inhibited formation of covalent bonds between hAGP and [3H]UCN-01. The amino acid sequence of the photolabeled peptide was concluded to be SDVVYTDXK, corresponding to residues Ser-153 to Lys-161 of hAGP. No PTH derivatives were detected at the 8th cycle, which corresponded to the 160th Trp residue. This strongly implies that Trp-160 was photolabeled by [3H]UCN-01. Three recombinant hAGP mutants (W25A, W122A, and W160A) and wild-type recombinant hAGP were photolabeled by [3H]UCN-01. Only mutant W160A showed a marked decrease in the extent of photoincorporation. These results strongly suggest that Trp-160 plays a prominent role in the high affinity binding of [3H]UCN-01 to hAGP. A docking model of UCN-01 and hAGP around Trp-160 provided further details of the binding site topology.