Local anaesthetic effect of topical amethocaine gel in neonates: randomised controlled trial

Mucoadhesive, Thermoreversible Hydrogel, Containing Tetracaine-Loaded Nanostructured Lipid Carriers for Topical, Intranasal Needle-Free Anesthesia

Recent advances have been reported for needle-free local anesthesia in maxillary teeth by administering a nasal spray of tetracaine (TTC) and oxymetazoline, without causing pain, fear, and stress. This work aimed to assess whether a TTC-loaded hybrid system could reduce cytotoxicity, promote sustained permeation, and increase the anesthetic efficacy of TTC for safe, effective, painless, and prolonged analgesia of the maxillary teeth in dental procedures. The hybrid system based on TTC (4%) encapsulated in nanostructured lipid carriers (NLC) and incorporated into a thermoreversible hydrogel of poloxamer 407 (TTCNLC-HG4%) displayed desirable rheological, mechanical, and mucoadhesive properties for topical application in the nasal cavity. Compared to control formulations, the use of TTCNLC-HG4% slowed in vitro permeation of the anesthetic across the nasal mucosa, maintained cytotoxicity against neuroblastoma cells, and provided a three-fold increase in analgesia duration, as observed using the tail-flick test in mice. The results obtained here open up perspectives for future clinical evaluation of the thermoreversible hybrid hydrogel, which contains TTC-loaded NLC, with the aim of creating an effective, topical, intranasal, needle-free anesthesia for use in dentistry.

Effectiveness of topical anesthetics on reducing tactile sensitivity in the paws of newborn rats

The aim of this study was to evaluate the effectiveness of three local, topical anesthetics on touch response thresholds of the paws of 1-day-old rats. Touch response thresholds were measured using Semmes Weinstein monofilaments after treatment of the paws with EMLA (2.5% lidocaine and 2.5% prilocaine), alcaine (.5% proparacaine), triocaine (20% benzocaine, 6% lidocaine, and 4% tetracaine), or petroleum jelly (treatment control). Touch thresholds significantly increased after treatment with EMLA 18% of the time, and there was no evidence of a systemic effect. Touch thresholds were not significantly altered after treatment with alcaine, triocaine, or petroleum jelly. Therefore, EMLA appears to be a slightly effective topical anesthetic for reducing tactile sensitivity in newborn rats.

Sweet-tasting solutions for needle-related procedural pain in infants one month to one year of age

BACKGROUND

Administration of oral sucrose or glucose with and without non-nutritive sucking is frequently used as a non-pharmacological intervention for needle-related procedural pain relief in infants.

OBJECTIVES

To determine the effectiveness of sweet-tasting solutions for needle-related procedural pain in infants one month to one year of age compared with no treatment, placebo, other sweet-tasting solutions, or pharmacological or other non-pharmacological pain-relieving methods.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012); MEDLINE via Ovid (1966 to 2012); CINAHL via OVID (1982 to 2012). The World Health Organization International Clinical Trials Registry Platform was also searched for any ongoing trials. Clinical trial registries, conference proceedings and references for randomised controlled trials (RCTs) were also searched. An updated search was run to capture any new publications before finalising the review in April 2012 and no new included studies were identified. Two review authors (MK & JF) independently abstracted data and assessed quality using a standard form. Authors have been contacted for missing data.

SELECTION CRITERIA

Randomised-controlled trials using a sweet-tasting solution to treat pain in healthy term infants (gestational age 37 weeks and over), between one month and 12 months of age who required needle-related procedures. These procedures included but were not limited to: subcutaneous or intramuscular injections, venepuncture, and heel lance. Studies in which the painful procedure was circumcision, lumbar puncture or supra-pubic bladder aspiration were not included as they are more severe and painful than needle-related procedures. Control conditions included no treatment or placebo (water) or any other identical intervention (same appearance and consistency) without active ingredient, another sweet-tasting solution, a pharmacological pain-relieving method (e.g. paracetamol, topical anaesthetic cream), non-pharmacological pain-relieving method (e.g. distraction method, non-nutritive sucking).

DATA COLLECTION AND ANALYSIS

Assessment of trial quality, data extraction and synthesis of data were performed using standard methods of the Cochrane Pain, Palliative and Supportive Care Group. We report mean differences (MD) with 95% confidence intervals (CI) using fixed-effect models as appropriate for continuous outcome measures. We planned to report risk ratio (RR) and risk difference (RD) for dichotomous outcomes. The Chi(2) test and I(2) statistic were used to assess between-study heterogeneity.

MAIN RESULTS

Sixty-five (65) studies were identified for possible inclusion in this review. Fourteen published RCTs with a total of 1551 participants met the inclusion criteria. Duration of cry was significantly reduced in infants who were administered a sweet-tasting solution [MD -13.47 (95% CI -16.80 to -10.15)], P < 0.00001 compared with water. However, there was considerable heterogeneity between the studies (I(2) = 94%) that we were unable to explain. Meta-analysis was not able to be undertaken for any of the other outcome measures, except for cry duration, because of differences in study design. However, most of the individual studies that measured pain found sucrose to significantly reduce pain compared with the control group. One study compared sucrose and Lidocaine-prilocaine cream and no significant difference was found between the two treatments for the outcomes pain and cry duration. Due to the differences between the studies, we were unable to identify the optimal concentration, volume or method of administration of sweet-tasting solutions in infants aged one to 12 months. Further large RCTs are needed.

AUTHORS' CONCLUSIONS

There is insufficient evidence to confidently judge the effectiveness of sweet-tasting solutions in reducing needle-related pain in infants (one month to 12 months of age). The treatments do, however, appear promising. Data from a series of individual trials are promising, as are the results from a subset meta-analysis of studies measuring duration of crying. Further well controlled RCTs are warranted in this population to determine the optimal concentration, volume, method of administration, and possible adverse effects.

Does topical amethocaine gel reduce pain from heel prick blood sampling in premature infants? A randomized double-blind cross-over controlled study

BACKGROUND

Heel prick blood sampling is the most common painful invasive procedure performed on neonates. Currently, there are no effective ways to provide pain relief from this painful procedure.

OBJECTIVE

To assess the efficacy of the topical anesthetic amethocaine 4% gel (Ametop, Smith & Nephew Inc, St Laurent) in reducing the pain of heel prick blood sampling in neonates.

METHODS

A randomized, double-blind, placebo controlled, crossover trial was conducted. Neonates between 33 to 37 weeks' gestational age in their first seven days of life were eligible. Heel prick blood sampling was performed on each participant twice. Each infant was randomly assigned to receive either amethocaine 4% gel or placebo to the heel for the first prick, and then received the alternative agent for the second prick. Prick pain was assessed using both Premature Infant Pain Profile (PIPP) and Neonatal Infant Pain Scale (NIPS). Squeeze pain was assessed by NIPS.

RESULTS

Ten babies were recruited. There were no significant differences in the average PIPP and NIPS scores between the treatment and placebo groups for both prick and squeeze pains from heel prick blood sampling. For prick pain, linear-regression showed significant correlation between the PIPP and NIPS scores. No adverse reactions were observed after application of either the active or placebo agents.

CONCLUSION

Topical amethocaine 4% gel is not shown to reduce prick and squeeze pains significantly from heel prick blood sampling in neonates between 33 to 37 weeks' gestational age. Further studies are needed to find ways to provide effective pain relief from this common procedure.

Procedural pain guidelines for the newborn in the United Kingdom

OBJECTIVE

To assess the use of analgesia guidelines for newborn infants in the United Kingdom.

STUDY DESIGN

Postal questionnaire to every neonatal unit in the United Kingdom.

RESULT

A total of 192 of 244 units replied (78.7% response). Most units had a guideline for elective intubation (70%), sedation for ventilation (78%) post-operative pain (when appropriate) (74%). Less prevalent were guidelines for painful minor procedures (35%). Only 33% of units gave a sweet-tasting solution for analgesia before routine painful procedures and 12% used a topical anesthetic cream.

CONCLUSION

Since the last survey in 2000 there has been a modest increased uptake in measures to prevent pain neonatal pain in the United Kingdom, but no pain guideline was present in almost 25% of units and no guideline for routine painful procedures in the majority.

Contact dermatitis and bradycardia in a preterm infant given tetracaine 4% gel

The use of analgesics for procedural pain management in the newborn infant has been steadily increasing during the past decade. With this trend of increased analgesic utilization, there is the potential for infants to suffer from drug-induced side effects. There also is the potential to wrongfully blame drugs for all adverse events that occur during analgesic use. Two adverse events that occurred in a neonate exposed to tetracaine gel and the probability that the adverse events were caused by the drug are presented. During administration of the topical local anesthetic tetracaine for analgesia during percutaneous central venous catheter placement, a preterm infant experienced bradycardia. Several hours later, a local cutaneous reaction that progressed to skin desquamation occurred at the site. The authors assessed the probability that tetracaine caused 2 adverse events using a validated adverse drug reaction probability scale by Naranjo et al. According to the algorithm developed by Naranjo et al, it was determined that bradycardia was unlikely caused by the drug; however, the dermal reaction was probably the result of the drug.The authors determined that tetracaine caused a serious local skin reaction, but not bradycardia, in a preterm infant. This is the first report of a serious skin reaction in a neonate treated with tetracaine. Based on these findings, tetracaine gel can continue to be used to treat pain in neonates with careful evaluation of the skin.

Analgesia and local anesthesia during invasive procedures in the neonate

BACKGROUND

Preterm and full-term neonates admitted to the neonatal intensive care unit or elsewhere in the hospital are routinely subjected to invasive procedures that can cause acute pain. Despite published data on the complex behavioral, physiologic, and biochemical responses of these neonates and the detrimental short- and long-term clinical outcomes of exposure to repetitive pain, clinical use of pain-control measures in neonates undergoing invasive procedures remains sporadic and suboptimal. As part of the Newborn Drug Development Initiative, the US Food and Drug Administration and the National Institute of Child Health and Human Development invited a group of international experts to form the Neonatal Pain Control Group to review the therapeutic options for pain management associated with the most commonly performed invasive procedures in neonates and to identify research priorities in this area.

OBJECTIVE

The goal of this article was to review and synthesize the published clinical evidence for the management of pain caused by invasive procedures in preterm and full-term neonates.

METHODS

Clinical studies examining various therapies for procedural pain in neonates were identified by searches of MEDLINE (1980-2004), the Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2004), the reference lists of review articles, and personal files. The search terms included specific drug names, infant-newborn, infant-preterm, and pain, using the explode function for each key word. The English-language literature was reviewed, and case reports and small case series were discarded.

RESULTS

The most commonly performed invasive procedures in neonates included heel lancing, venipuncture, IV or arterial cannulation, chest tube placement, tracheal intubation or suctioning, lumbar puncture, circumcision, and SC or IM injection. Various drug classes were examined critically, including opioid analgesics, sedative/hypnotic drugs, nonsteroidal anti-inflammatory drugs and acetaminophen, injectable and topical local anesthetics, and sucrose. Research considerations related to each drug category were identified, potential obstacles to the systematic study of these drugs were discussed, and current gaps in knowledge were enumerated to define future research needs. Discussions relating to the optimal design for and ethical constraints on the study of neonatal pain will be published separately. Well-designed clinical trials investigating currently available and new therapies for acute pain in neonates will provide the scientific framework for effective pain management in neonates undergoing invasive procedures.

Pathology of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is one of the leading causes of death and morbidity worldwide. Despite intensive investigation, its pathology and pathophysiology are not well understood. The hallmarks of the disease are irreversible airflow limitation and chronic inflammation. Small airway obstruction due to progressive inflammation and fibrosis, and the loss of elastic recoil mediated by elastolysis and apoptosis equally contribute to pathologic changes. However, it is debated to what extent the obstruction of large airways leads to altered lung function. Three morphologic entities are described in the literature under one disease; chronic bronchitis, obstructive bronchiolitis and emphysema may appear in the same patient at the same time. The authors review pathologic changes observed in chronic obstructive pulmonary disease, including acute exacerbations and secondary pulmonary hypertension as severe but common complications of the disease. Furthermore, we detail recent scientific evidences for major cellular and molecular inflammatory pathway activation. These mechanisms result in accelerated apoptosis, remodeling and increased proinflammatory cytokine release. Targeting intracellular pathological changes may lead to the discovery of a new generation of drugs that could reduce chronic obstruction before airway irreversibility is established.

Rapid Human Skin Permeation and Topical Anaesthetic Activity of a New Amethocaine Microemulsion

We developed a fast-acting, topical, 4% (w/w) amethocaine microemulsion and tested its in vitro permeation in isolated human skin. Comparison with a commercial amethocaine gel (Ametop((R)) ) was performed using Franz diffusion cells. Permeability coefficient (k(p)), flux (J) and percentage permeation after 10 h of microemulsion application were, in all cases, 1.5 times higher than those of the gel. The values obtained for the P(1) parameter [1], 1.06.10(-2) cm (microemulsion) and 0.724.10(-2) cm (gel) indicate that the microemulsion excipients favour amethocaine deposition in the skin, increasing the permeability coefficient, amount of drug retained in the skin, and the flux achieved. Analgesic activity was also examined in rats made hyperalgesic or allodynic after carrageenan-induced inflammation. The rats were distributed into four groups (n = 5-9 per group), each group receiving topically either amethocaine microemulsion, amethocaine gel (Ametop), amethocaine subcutaneous infiltration or nothing (controls). In edematous paws, anti-hyperalgesic activity appeared at 4.2 and 13.8 min after application of amethocaine microemulsion and gel, respectively. These effects are lower than after 0.5% w/w amethocaine infiltration. Amethocaine microemulsion was the only topical formulation with an anti-allodynic effect, although this effect was less than with amethocaine infiltration. These results suggest that microemulsion could be a valuable formula for improving amethocaine permeation and thus bringing rapid pain relief.

A critical review of the topical local anesthetic amethocaine (Ametop) for pediatric pain

A topical formulation of the ester-type local anesthetic amethocaine (tetracaine) [Ametop ] is currently available for reducing pain from cutaneous procedures such as venipuncture. The Ametop mark preparation contains 40 mg of amethocaine base (4% w/w) and produces anesthesia within 30-45 minutes of application; duration of action ranges from 4 to 6 hours. Clinical studies have demonstrated the superiority of the 4% amethocaine preparation over placebo in pediatric populations for indications such as intravenous cannulation, vaccination, and venipuncture. Amethocaine has been shown to produce anesthesia comparable to that of 5% lidocaine-prilocaine for procedures such as venipuncture and accessing centrally placed devices; in general, anesthesia was achieved more rapidly with amethocaine than lidocaine-prilocaine. In the neonatal population amethocaine was found to be ineffective at reducing the pain of heel prick and peripherally inserted central catheters. Depending on the type of procedure, amethocaine application times between 30 and 60 minutes have produced clinically acceptable anesthesia; application times <30 minutes have not been associated with reliable anesthesia. The 4% amethocaine preparation is well tolerated; the most commonly reported local skin reaction is transient local erythema while local edema and itching have been reported more rarely. There have been no accounts of systemic toxicity with topical use of the preparation. Several cases of sensitization have been described in adults upon repeated exposure to topical amethocaine. In summary, the novel preparation of 4% amethocaine gel has been shown to be clinically effective for managing pain associated with minor cutaneous procedures while maintaining a good tolerability profile. Amethocaine has also demonstrated similar efficacy to lidocaine-prilocaine when appropriate application times are used; the more rapid onset of action and extended duration of action of amethocaine may make it more useful than lidocaine-prilocaine in busy clinical settings.

Treatment of neonatal pain without a gold standard: the case for caregiving interventions and sucrose administration

Although many different neonatal pain assessment scales are used in clinical research, no gold-standard instrument exists. The multitude of pain assessment scales used has, in fact, threatened the validity of many studies and confused the construct of pain. This integrative review of the neonatal pain literature provides the recommendations from practice guidelines and the current evidence for modifying the pain response prior to and during common painful procedures.

Assessment of airway function in young children with asthma: comparison of spirometry, interrupter technique, and tidal flow by inductance plethsmography

The assessment of airway function in young children requires adaptation of techniques designed for adults and/or application of techniques that do not require complex respiratory maneuvers. We sought to assess two methods of measuring airway function: time to peak expiratory flows as a ratio of expiratory time (T(PTEF)/T(E)), derived from respiratory inductance plethysmography, and total respiratory resistance by the interrupter technique (Rint), both obtained during quiet tidal breathing. Both techniques were referenced to FEV1 and flow at 50% expired volume (FEF50) from conventional spirometry in 30 children aged 4-8 years (median age, 6.9; range, 4.5-8.5 years) with a physician diagnosis of asthma and who were able to perform FEV1 with a repeatability of at least 8%. T(PTEF)/T(E) and Rint were performed in random order followed by spirometry, in order to reduce the possible effects of pulmonary stretch on tidal breathing measures. Coefficients of variation (CV) and mean absolute change/baseline standard deviation were derived for each measurement. Baseline FEV1 did not correlate significantly with T(PTEF)/T(E) (r = 0.025), but did correlate with Rint (r = 0.737, P < 0.001); respective relationships for change after bronchodilator were r = 0.09 (ns) and r = 0.64 (P < 0.001). FEF50 also correlated significantly with Rint (R = 0.769, P < 0.001) but not with T(PTEF)/T(E). FEV1 and FEF50 both increased postbronchodilator, with respective mean changes of 11.4% and 28% (P < 0.001), while Rint decreased by 24.3% (P < 0.001). No significant changes were noted for T(PTEF)/T(E). T(PTEF)/T(E) derived from inductance plethysmography does not detect mild airway obstruction or modest changes in airway caliber following bronchodilator in young children with asthma. The interrupter technique may have a role in assessing baseline airway function and response to therapy in children unable to perform reliable spirometry, and/or when the investigator wishes to avoid the possible influence of forced maneuvers on airway tone.

Rapid Skin Anesthesia Using a New Topical Amethocaine Formulation: A Preclinical Study

We developed a fast-acting topical amethocaine emulsion and tested its analgesic activity against heat or mechanically induced pain in a rat paw model. The first experiment was performed in rats made hyperalgesic or allodynic after carrageenan-induced inflammation. Rats were distributed in five subgroups, each receiving topically one of the following: amethocaine microemulsion, amethocaine gel (Ametopgel), EMLA (Eutectic Mixture of Local Anesthetics) cream, amethocaine infiltration, or nothing (controls). The second experiment was conducted on healthy, selected heat- or touch-hypersensitive rats, which were distributed as in the first experiment. Paw withdrawal time from a heat and a mechanical stimulus was used as a pain index. In the first experiment, antihyperalgesic activity appeared at 4.2, 13.8, and 14 min after amethocaine microemulsion, gel, or EMLA cream, respectively. Amethocaine microemulsion was the only topical formulation with an antiallodynic effects, although less than with amethocaine infiltration. In healthy rats (second experiment), all topical formulations produced similar analgesic effects in heat-induced pain of the ipsilateral paw. Activity in the contralateral paw appeared earlier with amethocaine microemulsion, which was also the only one that increased touch-induced withdrawal time in the ipsi- and contralateral paws. Therefore, the microemulsion could be valuable for improving amethocaine skin penetration and thus bringing rapid pain relief.

IMPLICATIONS

Topical anesthetics are used in several painful clinical procedures, but they tend to have a slow onset time. A new amethocaine microemulsion with a faster onset of analgesia than commercial formulations was developed and its activity tested in pain states induced by heat or mechanical stimulus in inflamed and healthy rat paws.

A randomized controlled trial evaluating the efficacy of tetracaine gel for pain relief from peripherally inserted central catheters in infants

BACKGROUND

Insertion of peripherally inserted central catheters (PICC) is a commonly performed procedure in both preterm and term infants. Tetracaine 4% gel (Ametop; Smith & Nephew Inc, St. Laurent, Quebec), a topical anesthetic, although reported to be effective for reducing the pain of venipuncture in neonates, has not been investigated for the management of pain associated with the PICC procedure.

PURPOSE

To determine the efficacy of tetracaine gel for managing the pain associated with the PICC procedure in preterm and term infants.

METHODS

A double-blind, placebo-controlled, randomized controlled trial (RCT) design was used. Infants undergoing nonurgent PICC insertion were randomized to receive either the treatment (1.0 g of tetracaine 4% gel) or placebo control (1.0 g of eucerin-plus cream) applied to the skin under occlusion for 30 minutes before the procedure. Data on the behavioral (facial expression) and physiologic (heart rate and oxygen saturation) indicators of pain were collected via videotaping and computer monitoring throughout the procedure. Data then were coded and measured by independent observers using the Premature Infant Pain Profile (PIPP; Stevens et al, 1996), and analyzed using descriptive statistics and repeated-measures analyses of variance.

RESULTS

Forty-nine infants, gestational age 27 to 41 weeks (mean = 33; SD = 4.2) and age at time of insertion 2 to 85 days (mean = 18; SD = 22.5) participated. No differences were found between the groups at the time of randomization. There were no adverse cardiorespiratory events or local skin reactions in either group. There was a significant within-subjects main effect of time across the procedure (F[48,3] = 11.03; P < 0.0001). There was no significant between-subjects main effect of group (F[48,1] = 0.11; P = 0.74) and no (group x time) interaction (F[48,3] = 0.45; P = 0.72).

CONCLUSION

Tetracaine gel was not effective for pain relief for PICC insertion in infants. Its use for pain relief cannot be recommended based on the results of this study. Other pharmacologic, behavioral, and physical interventions should be investigated for safety and relief of procedural pain in this population of infants.

Assessment and management of pain in infants

Infants, including newborn babies, experience pain similarly and probably more intensely than older children and adults. They are also at risk of adverse long term effects on behaviour and development, through inadequate attention towards pain relief in early life. However, the issue of analgesia in young babies has been largely neglected in most clinical settings, despite subjecting them to painful diagnostic and therapeutic procedures. Several therapeutic and preventive strategies, including systemic and local pharmacological and non-pharmacological interventions, are reported to be effective in relieving pain in infants. A judicious application of these interventions, backed by awareness and sensitivity to pain perception, on the part of the caregivers is likely to yield the best results. This article is a review of the mechanisms of pain perception, objective assessment, and management strategies of pain in infants.

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.

Wound sensitivity as a measure of analgesic effects following surgery in human neonates and infants

Postoperative wound sensitivity following abdominal surgery in neonates and infants has been little investigated, and is not well understood. Our aim was to quantify this sensitivity using the abdominal skin reflex (ASR), and to test the hypothesis that the threshold of this reflex would decrease following surgery, and would increase with the administration of analgesia. We measured ASR thresholds in infants under 1 year receiving unilateral abdominal surgery and in a small comparison group of non-surgical infants. The reflex was elicited by applying calibrated von Frey hairs to both sides of the abdomen at the same segmental level. In addition to threshold, the degree of reflex radiation as denoted by hip flexion was measured. The reflex threshold was significantly lowered at the wound site by up to 78% following surgery, and subsequently increased to varying degrees based on the type of analgesia used. The post-surgical drop in threshold was accompanied by an increase in reflex radiation. Thresholds remained below pre-operative values 24 h after surgery on the operated side. In addition, it was observed that infants in whom the indication for surgery was a chronic condition, displayed lower threshold values on the affected side prior to surgery. An objective and quantitative measure has been developed of wound sensitivity and level of analgesia in infants following surgery. The reflex threshold also provides a means of quantifying human central sensory processing, and may be used to detect referred visceral hypersensitivity in this age group.

Potential benefit of Bayesian forecasting for therapeutic drug monitoring in neonates

Therapeutic drug monitoring in neonate has been hampered by invasiveness of blood samplings raising ethical problems. A methodologic approach has been developped in adults and in children that is still unsufficiently developped in neonates, the Bayesian forecasting of drug plasma concentration. This method is particularly attractive in neonates using a few blood samples from an individual patient and more informations from a prior patient sample representative of the population the individual patient belongs to. The present article aims at reviewing the different procedures and methods to minimize invasiveness during therapeutic drug monitoring in neonate and at reviewing the methods for improving the quality of different dose adjustments using a Bayesian approach.

Pediatric anesthesia in dermatologic surgery: when hand-holding is not enough

BACKGROUND

Dermatologic procedures in children may require the use of topical and local anesthetics, sedatives, and general anesthesia.

OBJECTIVE

To review developments in topical and local anesthetics, sedatives, and general anesthesia relevant to dermatologic procedures in children.

METHODS

Review of the medical literature.

RESULTS

Topical anesthetics, including EMLA and liposome-encapsulated lidocaine cream, amethocaine, cetacaine, and benzocaine products may be useful for decreasing the pain of cutaneous procedures including intra-lesional lidocaine infiltration. A variety of sedative and hypnotic agents may be utilized for pediatric dermatology procedures, and guidelines for their appropriate use have been published. General anesthesia for dermatologic procedures in the pediatric population is appropriate for a variety of procedures including laser treatment of capillary malformations.

CONCLUSION

A variety of anesthetic, analgesic, and sedatives may be useful for pediatric cutaneous surgery.

Remodeling in asthma and chronic obstructive lung disease

Asthma and chronic obstructive lung disease (COPD) are both inflammatory conditions of the lung associated with structural "remodeling" inappropriate to the maintenance of normal lung function. The clinically observed distinctions between asthma and COPD are reflected by differences in the remodeling process, the patterns of inflammatory cells and cytokines, and also the predominant anatomic site at which these alterations occur. In asthma the epithelium appears to be more fragile than that of COPD, the epithelial reticular basement membrane (RBM) is significantly thicker, there is marked enlargement of the mass of bronchial smooth muscle, and emphysema does not occur in the asthmatic nonsmoker. In COPD, there is epithelial mucous metaplasia, airway wall fibrosis, and inflammation associated with loss of surrounding alveolar attachments to the outer wall of small airways: bronchiolar smooth muscle is increased also. Emphysema is a feature of severe COPD: in spite of the destructive process, alveolar wall thickening and focal fibrosis may be detected. The hypertrophy of submucosal mucus-secreting glands is similar in extent in asthma and COPD. The number of bronchial vessels and the area of the wall occupied by them increase in severe corticosteroid-dependent asthma: it is likely that these increases also occur in severe COPD as they do in bronchiectasis. Pulmonary vasculature is remodeled in COPD. In asthma several of these structural alterations begin early in the disease process, even in the child. In COPD the changes begin later in life and the associated inflammatory response differs from that in asthma. The following synopsis defines and compares the key remodeling processes and proposes several hypotheses.

Topical anesthetics in children: agents and techniques that equally comfort patients, parents, and clinicians

Topical anesthetics are increasingly important, as the number of outpatient surgeries for dermatologic problems in infants and children is steadily growing. This noninvasive modality of anesthetic delivery in conjunction with a reassuring environment may minimize the discomfort of otherwise painful procedures. Since the 1880s, when cocaine was first used as a topical ophthalmologic anesthetic, many ester-and amide-based local anesthetics have been developed for a variety of simple and complex procedures. The pediatric dermatologist's arsenal of topical anesthetic preparations is increasing with the development of novel vehicles of transdermal delivery and the use of anesthetics in combination. Eutectic mixture of local anesthetics is currently the most frequently prescribed topical agent, though the use of ELA-max, another lidocaine-containing preparation, is gaining momentum, especially in the neonatal population. Amethocaine, tetracaine, iontophoresis, and the S-caine patch, a product on the horizon for use in the pediatric population, also are included in this discussion.

The neurobiology of pain: developmental aspects

Invasive procedures that would be painful in children and adults are frequently performed on infants admitted to the neonatal intensive care unit. This article discusses sensory responses to these procedures in the immature nervous system and highlights the fact that, in addition to causing distress and delayed recovery, pain in infancy is also a developmental issue. First, the immaturity of sensory processing within the newborn spinal cord leads to lower thresholds for excitation and sensitization, therefore potentially maximizing the central effects of these tissue-damaging inputs. Second, the plasticity of both peripheral and central sensory connections in the neonatal period means that early damage in infancy can lead to prolonged structural and functional alterations in pain pathways that can last into adult life.

Topical amethocaine gel for pain relief of heel prick blood sampling: a randomised double blind controlled trial

BACKGROUND

Heel prick blood sampling is a commonly performed and painful procedure in the newborn infant. Use of a topical local anaesthetic does not relieve this pain. A 4% w/w amethocaine gel (Ametop) reduces the pain of venepuncture in the newborn but has not been tried with heel pricks.

AIM

To investigate the effect of topical amethocaine gel on the pain of heel prick in the newborn infant.

DESIGN

Randomised, double blind, placebo controlled trial.

SUBJECTS

Sixty newborn infants, gestation 28-42 weeks (median 36), postnatal age 1-16 days (median 5) undergoing routine heel prick blood sampling.

METHODS

A 1.5 g portion of 4% w/w amethocaine gel or placebo was applied to the skin under occlusion for one hour, then wiped away. Heel prick blood sampling with a spring loaded lance was performed five minutes later. The procedure was videotaped and pain assessed at one second intervals using an adaptation of the neonatal facial coding system (NFCS). No or minimal pain was defined as a cumulative score of less than 5 (out of 15) in the three seconds after firing of the lance and as lack of a cry in the first five seconds.

RESULTS

In terms of a low NFCS core and lack of cry (p = 0.12) 20 of 30 (67%) in the amethocaine group and 13 of 29 (45%) in the placebo group had no or minimal pain in response to the heel prick. The median cumulative NFCS score over the three seconds after firing the lance was 3 (interquartile range 0-6) in the amethocaine group compared with 5 (interquartile range 1-10) in the placebo group (p = 0.07). These differences are not significant.

CONCLUSIONS

Topical amethocaine gel does not have a clinically important effect on the pain of heel prick blood sampling and its use for this purpose cannot therefore be recommended. Alternative approaches to the relief of pain from this procedure should be explored.

Does topical amethocaine gel reduce the pain of venepuncture in newborn infants? A randomised double blind controlled trial

BACKGROUND

Topical amethocaine provides effective pain relief during venepuncture in children, and has been shown to have a local anaesthetic action in the newborn.

AIM

To investigate the effect of topical amethocaine on the pain of venepuncture in the newborn.

DESIGN

Randomised double blind placebo controlled trial.

SUBJECTS

Forty newborn infants, gestation 27-41 weeks (median 33), age 2-17 days (median 7), undergoing routine venepuncture.

METHOD

A 1.5 g portion of 4% (w/w) amethocaine gel (Ametop; Smith and Nephew, Hull, UK) or placebo was applied to the skin under occlusion for one hour, then wiped away. Venepuncture was performed five minutes later. Facial reaction and cry were recorded on videotape. Pain was assessed using a validated adaptation of the neonatal facial coding system. Five features were scored at one second intervals for five seconds before and after venepuncture. No or minimal pain was defined as a cumulative score of below 10 (out of 25) in the five seconds after needle insertion. Each author scored the tapes independently.

RESULTS

There was close agreement on scoring of the tapes. One infant was excluded because of restlessness before the venepuncture. Of 19 amethocaine treated infants, 16 (84%) showed little or no pain compared with six of 20 (30%) in the placebo group (p = 0.001). The median cumulative neonatal facial coding system score over five seconds after needle insertion was 3 compared with 16 in the placebo group (p = 0.001). Of the 19 amethocaine treated infants, 15 (79%) did not cry compared with five of 20 (25%) placebo treated infants (p = 0.001). No local reaction to amethocaine was seen.

CONCLUSION

Topical amethocaine provides effective pain relief during venepuncture in the newborn.

The dermis

All the dermal structures are less well developed in the newborn than in the older infant or child, but there are few important consequences of this. Sweating in response to a thermal stimulus occurs at birth in the term infant and can be detected in most preterm infants from 2 weeks of age. It is poorly developed though. Emotional (palmar/plantar) sweating is present from birth in term infants only. Skin blood flow can be regulated in term and preterm infants, and is often measured indirectly as a temperature gradient. Such a gradient is temperature as well as illness dependent which limits its use as a clinical tool. Sensory nerve endings are readily stimulated in the most immature infants. Finally, damage to the skin in the newborn period commonly leads to scarring, although this usually improves with time.

Topical amethocaine gel in the newborn infant: how soon does it work and how long does it last?

AIM

To explore the time of onset and duration of action of topical amethocaine gel in the newborn infant.

DESIGN

A randomised double blind placebo controlled trial.

SUBJECTS

Thirty six infants were studied after 30 minutes application and 36 after 60 minutes application. A total of 56 infants (gestation 27-42 weeks, weight 0. 79-4.1 kg) were studied in the first two weeks after delivery.

METHOD

1.5 g amethocaine or placebo was applied to the dorsum of either foot, occluded, and then left for 30 or 60 minutes. Local anaesthesia was assessed by observing the cutaneous withdrawal response to graded nylon filaments (von Frey hairs). If there was a difference between feet in filament thickness required to elicit a response, the infant was studied in an identical manner at hourly intervals until the difference had disappeared.

RESULTS

Evidence of local anaesthetic action of amethocaine was seen in 23 of 36 (64%) infants after 30 minutes and 26 of 36 (72%) infants after 60 minutes application (no significant difference). Evidence of local anaesthetic action was independent of gestation and order of testing. Amethocaine responders showed a significantly deeper anaesthetic action than placebo responders. The median duration of action was 1.5 hours (range 0.5-3.5) after 30 minutes and three hours (range 1-5) after 60 minutes (p<0.001).

CONCLUSION

Topical amethocaine gel has a local anaesthetic action after 30 minutes application, but application for 60 minutes results in longer duration of action.