The pediatric airway: Historical concepts, new findings, and what matters

New observations from novel imaging techniques regarding the anatomy, dimensions, and shape of the pediatric airway have emerged and provide insight for potential changes in the clinical management of the airway in infants and children. These new findings are challenging the historical concepts of a funnel-shaped upper airway with the cricoid ring as the narrowest dimension. Although these tenets have been accepted and used to guide clinical practice in airway management, there are limited clinical investigations in children to support the validity of these concepts. Imaging modalities such as magnetic resonance imaging, computed tomography (CT) scanning, multi-detector CT imaging, and videobronchoscopy suggest the need to revisit the historical view of the pediatric airway. This manuscript reviews the historical evolution of pediatric airway studies, summarizes important scientific observations from recent investigations relevant to our clinical understanding of pediatric airway anatomy, and discusses the importance of these findings for pediatric airway management.

Use of a Piglet Model for the Study of Anesthetic-induced Developmental Neurotoxicity (AIDN): A Translational Neuroscience Approach

Anesthesia cannot be avoided in many cases when surgery is required, particularly in children. Recent investigations in animals have raised concerns that anesthesia exposure may lead to neuronal apoptosis, known as anesthesia-induced developmental neurotoxicity (AIDN). Furthermore, some clinical studies in children have suggested that anesthesia exposure may lead to neurodevelopmental deficits later in life. Nonetheless, an ideal animal model for preclinical study has yet to be developed. The neonatal piglet represents a valuable model for preclinical study, as they share a striking number of developmental similarities with humans.

The anatomy and physiology of piglets allow for implementation of rigorous human perioperative conditions in both survival and non-survival procedures. Femoral artery catheterization allows for close monitoring, thus enabling prompt correction of any deviation of the piglet's vital signs and chemistries. In addition, there are multiple developmental similarities between piglets and human neonates. The techniques required to use piglets for experimentation will require experience to master. A pediatric anesthesiologist is a critical member of the investigative team. We describe, in a general sense, the appropriate use of a piglet model for neurodevelopmental study.

Effects of partial sleep deprivation on reaction time in anesthesiologists

BACKGROUND

Fatigue in anesthesiologists may have implications that extend beyond individual well-being.

AIM

The aim of the present study was to evaluate the impact of sleep deprivation on the reaction time in anesthesiologists either after an overnight call or regular working hours. Moderation of this effect by coping strategies was observed.

METHODS

Psychomotor vigilance test was used to assess reaction time in 23 anesthesiologists at two time-points: (i) on a regular non-call day and (ii) after a 17-h in-house call. Student's paired t-test was used to compare Psychomotor Vigilance Task data at these two moments. Change score regression was performed to determine the association between coping strategies, assessed using the Coping Strategy Indicator instrument, and decline in reaction time after night call.

RESULTS

Twenty-one colleagues completed the psychomotor vigilance test measurements after two decided to end their participation for personal reasons. Post-call psychomotor vigilance test mean reaction time decreased by an average of 31.2 ms (95% CI: 0.5, 61.9; P = 0.047) when compared to regular day. Reliance on specific coping mechanisms, indicated by Coping Strategy Indicator scale scores, included problem-solving (28 ± 4), followed by seeking social support (23 ± 5) and avoidance (19 ± 4). The change score regression model (r² = 0.48) found that greater reliance on avoidance was associated with greater increase in reaction time after night call.

CONCLUSION

Reaction time increased considerably in anesthesiologists after a night call duty. Greater subjective reliance on avoidance as a coping strategy was associated with greater deterioration in performance.

Selective induction of IL-1β after a brief isoflurane anesthetic in children undergoing MRI examination

PURPOSE

To determine if isoflurane anesthesia without surgery causes systemic inflammation in children. Inflammation is targeted as responsible for the development of many neurologic pathologies. The effect will be evaluated by measuring serum cytokine levels before and after isoflurane anesthesia. The possible neurotoxic effect of anesthetic agents is a concern in pediatric anesthesia. Questions remain as to the true effects of anesthesia alone on systemic inflammation. The current study assesses systemic inflammatory response to general anesthesia in children not exposed to surgical stress.

METHODS

Twenty-five patients, aged 6 months to 11 years undergoing MRI scanning were recruited. Patients with ASA Physical Status Classification >II, known neurologic disease, prematurity, recent infection, or current treatment with anti-inflammatory medications were excluded. Each patient received a sevoflurane induction, peripheral intravenous catheterization, and laryngeal mask airway placement. Isoflurane was titrated to ensure adequate depth of anesthesia. Two peripheral blood samples were obtained: one immediately after placement of the PIV and one upon arrival to the post-anesthesia care unit. Serum cytokine levels were compared between pre- and post-isoflurane time points using paired t tests.

RESULTS

For all patients, interleukin-1β increased after isoflurane when compared to pre-isoflurane samples (pre = 25.97 ± 9.01, post = 38.53 ± 16.56, p = 0.0002). Serum levels of IL-6 (pre = 2.28 ± 2.27, post = 2.04 ± 2.15, p = 0.146) and tumor necrosis factor-α (pre = 94.26 ± 18.07, post = 85.84 ± 12.12, p = 0.057) were not significantly changed. Interleukin-10 and vascular endothelial growth factor were undetectable in pre- and post-isoflurane samples at a minimum detection threshold of 6.6 and 10 pg/ml, respectively.

CONCLUSIONS

A brief (approximately 60 min) exposure to isoflurane general anesthesia, without induced surgical stress, significantly increased serum IL-1β, a selective activation marker of systemic inflammation (IL-1β pathway).

Postoperative pain management in patients undergoing thoracoscopic repair of pectus excavatum: A retrospective analysis of opioid consumption and adverse effects in adolescents

Introduction:

Although the Nuss procedure provides excellent cosmetic results for the correction of pectus excavatum, the provision of analgesia following such procedures can be challenging.

Methods:

The current study retrospectively reviews our experience over a 2.5 year period with thoracic epidural analgesia (TE), paravertebral blockade (PVB), and intravenous opioids delivered via patient-controlled analgesia (PCA) to provide postoperative analgesia.

Results:

The study cohort included 30 patients (mean age = 15.6 ± 1.5 years), 15 of whom were treated with PCA, 8 with TE, and 7 with PVB. There were no significant differences in pain scores between the 3 groups at any time point during the first 3 postoperative days. Compared to PCA, the PVB group had lower opioid consumption over the first 24 hours of hospitalization by 1.7 mg/kg morphine equivalents (95% CI of difference: 0.1, 3.3; p=0.035); but had higher opioid consumption by 2.0 mg/kg morphine equivalents than the TE group (95% CI of difference: 0.3, 3.7; p=0.024). There were no differences in opioid consumption between PVB and PCA or between PVB and TE at 48 or 72 hours. The number of intraoperative hypotension episodes was significantly lower in the PCA group when compared to the PVB group (p=0.001), with no difference between the PVB and TE groups.

Conclusions:

The use of regional anesthesia should be considered a viable option for the relief of postoperative pain in pediatric patients following the Nuss procedure albeit with a higher incidence of intraoperative hemodynamic effects. A randomized, prospective, study powered to compare all 3 techniques against one another would be necessary to confirm the significance of these findings.

Cricoid ring: Shape, size, and variability in infants and children

Background:

Knowledge regarding the shape, size, and variability of the cricoid ring is important to properly choose the correct endotracheal tube (ETT) in the pediatric patient. Studies have measured the size of the cricoid ring using methodologies such as moulages, magnetic resonance imaging, and video-bronchoscopy. In the present study, computed tomography (CT) -based images were used to determine the shape, size, and configuration of the cricoid ring in the pediatric population taking into considerations growth and development.

Methods:

This is a retrospective review using 130 CT images of children ranging in age from 1 month to 10 years undergoing radiological evaluation unrelated to airway symptomatology. The CT scans were obtained in spontaneously breathing patients during either natural sleep or procedural sedation. Anteroposterior (AP) and transverse (T) diameters were measured at the cricoid ring using these images.

Results:

The cricoid ring is generally round in children older than 1 year with a T/AP ratio ranging between 0.98 and 1.01. However, in infants (1–12 months of age), the cricoid ring is elliptical with the AP dimension an average of 0.31 mm larger than the T dimension with a T/AP ratio of 0.95. A statistically significant difference between the T and AP dimensions was only observed in infancy (P < 0.05).

Conclusion:

The cricoid ring is round in children older than 1 year of age. In infants, the cricoid shape presents a more elliptical configuration because the T-axis is narrower than the AP dimension. CT is recognized as the most accurate technique to study cricoid ring configuration, and the present data may help clinicians determine the appropriate type, size, and shape of ETTs, particularly in infants.

Age-based analysis of pediatric upper airway dimensions using computed tomography imaging

BACKGROUND

Recent studies have challenged the historically accepted fact that the larynx is cone-shaped in infants and children. The present study used computed tomography (CT)-based measurements to evaluate airway dimensions. The purpose of this investigation was to determine the dimensional transition between the subglottic area and the cricoid ring in children.

METHODS

This is a retrospective review of 220 CT scans of children aged 1 month to 10 years undergoing radiological evaluation unrelated to airways symptomatology. The CT scans were evaluated in children either sleeping naturally or sedated throughout the study period. Anteroposterior (AP) and Transverse (T) diameters were measured at the subglottic level and at the cricoid ring.

RESULTS

The mean (±SD) age was 47.4 ± 33.1 months. The mean AP and transverse diameters were 9.2 ± 1.9 and 7.5 ± 1.6 mm at the subglottic area and 8.5 ± 1.7 and 8.3 ± 1.5 mm at the cricoid. AP dimension showed a decrease from the subglottis to the cricoid ring. A more rapid enlargement of the airway from the subglottis to cricoid ring is observed in the transverse dimension (P < 0.05). A linear progression in the size of airway dimensions between both levels was observed with age (r > 0.7).

CONCLUSION

The narrower transverse dimension compared to the AP diameter suggests that the airway is elliptical immediately below the vocal cords. The present study demonstrates that the airway characteristics in children between the subglottic area and the cricoid change from an elliptical to a round (circular) shape. The cone-shaped airway characteristic, which has been historically proposed, was not observed. Given that subglottic transverse diameter is the smallest area dimension, one must assume this is the most likely area of resistance to the passage of an endotracheal tube rather than only the cricoid.

A novel, clinically relevant use of a piglet model to study the effects of anesthetics on the developing brain

Background

Anesthesia-induced neurotoxicity research in the developing brain must rely upon an unimpeachable animal model and a standardized treatment approach. In this manner, identification of mechanisms of action may be undertaken. The goal of this study was to develop a novel, clinically relevant, translational way to use a piglet model to investigate anesthesia effects on the developing brain.

Methods

29 newborn piglets were assigned to either: (1) control (no intervention, n = 10); (2) lipopolysaccharide (LPS; positive inflammatory control, n = 9); or (3) isoflurane anesthesia (n = 10). Positive inflammatory control animals were given 100 mcg/kg LPS from Escherichia coli intraperitoneally (IP) on the same day as those receiving isoflurane. Isoflurane was administered for 3 h while care was taken to ensure human perioperative conditions. To establish a clinical scenario, each animal was intubated and monitored with pulse oximetry, invasive and non-invasive blood pressure, electrocardiogram, temperature, end-tidal CO₂, anesthetic concentration, and iSTAT blood analysis. All animals were sacrificed after 48 h using transcardiac perfusion of ice-cold, heparinized phosphate buffered saline (PBS) followed by 4 % paraformaldehyde (PFA). Brains were collected and histopathological analysis focused on the entorhinal cortex looking for degenerative changes due to its critical role in learning and memory. Reliable identification of entorhinal cortex was achieved by using colored ink on the surface of the brains, which was then cross-referenced with microscopic anatomy. Hematoxylin & eosin-stained high-power fields was used to quantify cells. ImageJ™ (National Institutes of Health, Bethesda, MD, USA) was used to count absolute number of progenitor glial cells (PGC) and number of PGCs per cluster. Immunohistochemistry was also utilized to ensure positive identification of cellular structures.

Results

Histopathological sections of 28 brains were analyzed. One animal in the LPS group died shortly after administration, presumably from inadvertent intravascular injection. There was an acute basal ganglia ischemic infarct in one isoflurane-treated animal. A large number of small, round nucleated cells were seen throughout layer II of the entorhinal cortex in all animals. These cells were identified as PGCs using immunohistochemistry and light microscopy. Although there was no difference in the absolute number of PGCs between the groups, animals given isoflurane or LPS demonstrated a significant increase in cells forming ‘clusters’ in the entorhinal cortex. An apparent change in the pattern of doublecortin labeling also suggests changes in neuronal precursors and undifferentiated neurons.

Conclusions

This study represents the first novel use of a clinically relevant neonatal piglet model to study anesthesia effects on the developing brain. LPS induces neuroinflammation, and this is a potential mechanism for LPS and perhaps isoflurane in causing a change in progenitor cell distribution. We postulate that the isoflurane-induced change in glial progenitor cell distribution could have important implications for cell differentiation, maturation and neural circuit behavior in the rapidly developing brain.

Time to talk about work-hour impact on anesthesiologists: The effects of sleep deprivation on Profile of Mood States and cognitive tasks

BACKGROUND

A physician's fatigue raises significant concerns regarding personal and patient safety. Effects of sleep deprivation on clinical performance and the quality of patient care are major considerations of today's health care environment.

AIM

To evaluate the impact of partial sleep deprivation after a 17-h overnight call (3 pm-7 am) on the mood status and cognitive skills of anesthesiologists in an academic clinical hospital setting, as compared to these parameters during regular working hours.

METHODS

Taking circadian rhythm into account, the following measures were assessed in 21 pediatric anesthesiologists at two time points over the course of the study; (i) between 7 and 8 am on a regular non call day, and (ii) between 7 and 8 am after a 17-h in-house call (3 pm-7 am). Six mood states were assessed using the Profile of Mood States. A Total Mood Disturbance (TMD) score was obtained as the sum of all mood scores minus vigor. The total score provides a global estimate of affective state. Simple cognitive tests were similarly administered to assess cognitive skills. A two-tailed paired t-test was used to compare data between regular and post call days. A P < 0.05 was used.

RESULTS

The study cohort included 21 pediatric anesthesiologists at a tertiary care children's hospital. Tension, anger, fatigue, confusion, TMD, irritability, feeling jittery, and sleepiness were significantly affected (P < 0.05). A decrease in vigor, energy, and confidence was observed after a night call shift (P < 0.05). There was also a decrease in being "talkative" after the call shift (P < 0.05).

CONCLUSION

Partial sleep deprivation affects the total mood status of anesthesiologists and impacts their cognitive skills. These findings are particularly relevant in a context of increased work expectation, particularly on clinical performance in our modern medical system. Such observations suggest that there may be changes that impact the safety of our patients and the quality of health care that is provided.

Penicillin allergy and surgical prophylaxis: Cephalosporin cross-reactivity risk in a pediatric tertiary care center

BACKGROUND

First generation cephalosporins are commonly used as antibiotic prophylaxis prior to surgery. Patients labeled as penicillin-allergic are often precluded from receiving cephalosporins because of an allergic cross-reactivity. The aims of this study were to evaluate the clinical practice for surgical prophylaxis at Nationwide Children's Hospital and to determine the incidence of adverse effects and allergic reactions when using cephalosporins in patients labeled as penicillin-allergic.

METHODS

A retrospective chart review was performed to identify patients who were allergic to penicillin, penicillin antibiotic family, who required surgical treatment for an existing medical condition, and received an antibiotic to prevent surgical site infection.

RESULTS

Five hundred thirteen penicillin-allergic patients were identified, encompassing 624 surgical cases. Cephalosporins were administered in 153 cases (24.5%) with cefazolin used 83% of the time. Only one documented case of nonanaphylactic reaction was reported. Clindamycin was the most common cephalosporin substitute (n=387), and the reported adverse reaction rate was 1.5%. No cases of anaphylaxis were documented.

CONCLUSIONS

Our data suggest that the administration of cephalosporins for surgical prophylaxis following induction of anesthesia in a patient with a known or reported penicillin-allergy appears appropriate and results in a lower adverse event rate that when clindamycin is administered.

Plethysmography variability index response to isovolemic hemodilution in children prior to surgery for congenital heart disease

The aim of this study was to evaluate the response of pleth variability index (PVI) to phlebotomy in anesthetized children prior to surgery for congenital heart disease. After induction of general anesthesia and prior to surgical incision, approximately 10 mL/kg of blood was removed from 40 mechanically ventilated children over a 5-10 min period. The PVI was continuously monitored. Additionally, the volume of crystalloid required to ensure hemodynamic and near infrared spectroscopy stability was recorded. There was no difference between the pre-phlebotomy PVI (13% ± 6.2) and the post-phlebotomy PVI (16.4% ± 9.6) (P = 0.55). Patients who had a starting PVI ≤14% had a significant increase in PVI after phlebotomy from 9.1% ± 3 to 14.3% ± 7.2 (P = 0.0014). Although, patients with a pre-phlebotomy PVI of >14% required more crystalloid replacement (11 ± 9.4 mL/kg) than those with a PVI ≤14% (5.3 ± 4.7 mL/kg), this was not significant (P = 0.06). In patients who received less crystalloid replacement during phlebotomy, PVI did show a significant increase. Additionally, the data suggests that patients with a pre-phlebotomy PVI >14% required greater fluid replacement than those with a PVI < 14%. Further research is needed to better delineate the utility of PVI in this unique group of patients.

Effects of hemodilution after traumatic brain injury in juvenile rats

BACKGROUND

Normovolemic hemodilution (HD) in adult animal studies has shown exacerbation of traumatic brain injury (TBI) lesion volumes. Similar studies in juvenile rats have not been reported and outcomes are likely to be different. This study investigated the effects of normovolemic hemodilution (21% hematocrit) in a juvenile TBI (jTBI) model.

METHODS

Twenty 17-day-old rats underwent moderate cortical contusion impact injury (CCI) and were divided into four groups: CCI/hemodilution (HD) (group HD), CCI/no HD (group C), Sham/HD (group SHD), and Sham/no HD (group S). Regional laser Doppler flowmetry (LDF), edema formation (MRI-T2WI), water mobility assessed using diffusion weighted imaging (MRI-DWI), open field activity tests, and histological analyses were evaluated for lesion characteristics.

RESULTS

Hemodilution significantly increased blood flow in the HD compared to the C group after TBI. T2WI revealed a significantly increased extravascular blood volume in HD at 1, 7, and 14 days post-CCI. Edematous tissue and total contusional lesion volume were higher in HD-treated animals at 1 and 14 days. DWI revealed that HD, SHD, and C groups had elevated water mobility compared to S groups in the ipsilateral cortex and striatum. Histology showed a larger cortical lesion in the C than HD group. Open field activity was increased in HD, C, and SHD groups compared to the S group.

CONCLUSIONS

Hemodilution results in significant brain hyperemia with increased edema formation, extravascular blood volume, and water mobility after jTBI. Hemodilution results in less cortical damage but did not alter behavior. Hemodilution is likely not to be clinically beneficial following jTBI.

Continuous Bupivacaine Infusion Post-Iliac Crest Bone Graft Harvesting in Pediatric Cleft Surgery: Role and Comparison with Ketorolac

Objective

To investigate the use of intravenous ketorolac and iliac crest bupivacaine infusion in the management of iliac crest donor-site pain in the pediatric cleft population. The null hypothesis was there is no difference with respect to pain scores between ketorolac and iliac crest bupivacaine infusion as analgesic adjuncts to intravenous opioids.

Method

A total of 54 children and adolescents (27 boys, 27 girls) undergoing alveolar cleft repair or Le Fort I osteotomy were assigned randomly in a prospective, single-blinded fashion to one of three groups: intravenous ketorolac plus iliac crest normal saline infusion, intravenous ketorolac plus iliac crest bupivacaine infusion, or iliac crest bupivacaine infusion alone. Iliac crest infusions and ketorolac were administered for 48 hours or until discharge, whichever occurred first. All patients received morphine via a patient-controlled analgesia device.

Main outcome Measure(s)

Primary outcome was pain score, and secondary outcomes were morphine consumption and satisfaction scores.

Results

Pain scores, morphine consumption, and satisfaction scores were not significantly different among groups. Estimated costs were significantly higher for bupivacaine infusion than intravenous ketorolac.

Conclusions

Iliac crest donor-site pain is well managed in this patient population. Intravenous ketorolac and iliac crest bupivacaine infusion provide comparable analgesia for iliac crest bone graft donor-site pain in children and adolescents.

Brain temperature: heat production, elimination and clinical relevance

Neurological insults are a leading cause of morbidity and mortality, both in adults and especially in children. Among possible therapeutic strategies to limit clinical cerebral damage and improve outcomes, hypothermia remains a promising and beneficial approach. However, its advantages are still debated after decades of use. Studies in adults have generated conflicting results, whereas in children recent data even suggest that hypothermia may be detrimental. Is it because brain temperature physiology is not well understood and/or not applied properly, that hypothermia fails to convince clinicians of its potential benefits? Or is it because hypothermia is not, as believed, the optimal strategy to improve outcome in patients affected with an acute neurological insult? This review article should help to explain the fundamental physiological principles of brain heat production, distribution and elimination under normal conditions and discuss why hypothermia cannot yet be recommended routinely in the management of children affected with various neurological insults.

Fundamentals of neuronal apoptosis relevant to pediatric anesthesia

The programmed cell death or apoptosis is a complex biochemical process that has risen to prominence in pediatric anesthesia. Preclinical studies report a dose-dependent neuronal apoptosis during synaptogenesis following exposure to intravenous and volatile anesthetic agents. Although emerging clinical data do not universally indicate an increased neurodegenerative risk of general anesthesia in early human life, a great deal of uncertainty was created within the pediatric anesthesia community. This was at least partially caused by the demand of understanding of basic science concepts and knowledge of apoptosis frequently out of reach to the clinician. It is, however, important for the pediatric anesthesiologist to be familiar with the basic science concepts of neuronal apoptosis to be able to critically evaluate current and future preclinical data in this area and future clinical studies. This current review describes the extrinsic and intrinsic pathways involved in the cell death process and discusses techniques commonly employed to determine apoptosis. In addition, potential mechanisms of anesthesia-induced neuronal apoptosis are illustrated in this review.

The use of NSAIDs in pediatric scoliosis surgery - a survey of physicians' prescribing practice

BACKGROUND

Pediatric scoliosis surgery is associated with considerable postoperative pain requiring opioids for analgesia. Nonsteroidal antiinflammatory drugs (NSAIDs) can be used as adjuvants for analgesia; however, the potential of these agents to affect bone healing raises concerns. No large-scale prospective studies have been performed to evaluate the benefit-to-risk ratio of NSAID use after pediatric scoliosis surgery. Given the lack of evidence in the literature, a survey of practice patterns of anesthesiologists from around the world was conducted with respect to the use of NSAIDs after pediatric spinal fusion surgery for scoliosis.

METHODS

One hundred and fourteen anesthesiologists from international academic pediatric hospitals were asked to complete an online survey. After 1 month, nonresponders were sent a second e-mail asking for their participation. All questions were developed specifically for this study.

RESULTS

Out of 80 anesthesiologists who responded 61 were included in the final analysis. Fifty-nine percent routinely use NSAIDs, the most common agents being intravenous ketorolac and oral ibuprofen. The majority of respondents begin to administer NSAIDs within the first three postoperative days for a duration of four or more days. The primary reason for not routinely prescribing NSAIDs was the risk of bone nonunion.

CONCLUSIONS

This survey demonstrates that the practice patterns of pediatric anesthesiologists from around the world with respect to the administration of NSAIDs for the management of postoperative pain after pediatric spinal fusion reflects the conflicting evidence in the literature and the lack of high-quality studies in humans.

Airway management in children: ultrasonography assessment of tracheal intubation in real time?

BACKGROUND

Pediatric tracheal intubation requires considerable expertise and can represent a challenge to many anesthesiologists. Confirmation of correct tracheal tube position relies on direct visualization or indirect measures, such as auscultation and capnography. These methods have varying sensitivity and specificity, especially in the infant and young child. Ultrasonography is noninvasive and is becoming more readily available to the anesthesiologist. In this study, we investigated the characteristic real-time ultrasonographic findings of the normal pediatric airway during tracheal intubation and its suitability for clinical use.

METHODS

Thirty healthy children with normal airways requiring tracheal intubation were studied. Ultrasonographic measurements of the pediatric airway during tracheal intubation under deep inhaled anesthesia were performed using a Sonosite Titan (Sonosite, Bothell, WA) scanner while recording characteristic images during this process. Correct tracheal tube placement was further confirmed using auscultation and satisfactory end-tidal capnography.

RESULTS

The mean (+/- sd) age of studied patients was 48 +/- 37 mo, weight was 19.7. +/- 8.6 kg and the sex ratio (m/f) was 1:2. Successful tracheal intubation was verified using the following criteria: 1) identification of the trachea and tracheal rings, 2) visualization of vocal cords, 3) widening of glottis as the tracheal tube passes through, and 4) tracheal tube position above carina and demonstration of movement of the chest wall visceroparietal pleural interface (i.e., sliding sign) after manual ventilation of the lungs. One esophageal intubation was readily recognized by visualization of the tube in the left paratracheal space.

CONCLUSION

This study describes characteristic ultrasonographic findings of the pediatric airway during tracheal intubation. It suggests that ultrasonography may be useful for airway management in children.

Impact of anesthetic agents on cerebrovascular physiology in children

The role of the pediatric neuroanesthetist is to provide comprehensive care to children with neurologic pathologies. The cerebral physiology is influenced by the developmental stage of the child. The understanding of the effects of anesthetic agents on the physiology of cerebral vasculature in the pediatric population has significantly increased in the past decade allowing a more rationale decision making in anesthesia management. Although no single anesthetic technique can be recommended, sound knowledge of the principles of cerebral physiology and anesthetic neuropharmacology will facilitate the care of pediatric neurosurgical patients.

THIS ARTICLE HAS BEEN RETRACTED Anatomic relationship between the internal jugular vein and the carotid artery in pre-school children--an ultrasonographic study

BACKGROUND

Central venous cannulation (CVC) in young children is technically difficult and may lead to potentially serious complications especially when performed blindly or using anatomical landmarks only. The aim of this study was to determine the anatomical relationship of the internal jugular vein (IJV) and the common carotid artery (CA) in preschool children using ultrasound.

METHODS

Forty-five children aged 60 months and under were included prospectively and divided into three groups: Group 1: <6 months, Group 2: 7-18 months and Group 3: 19-60 months. With the head in neutral position the location of the left and right IJV was noted as anterior, anterolateral (AL), lateral or medial in relation to the CA at the level of the cricoid cartilage. Depths of IJV and CA as well as time taken to locate the vessels were recorded.

RESULTS

The IJV was more commonly found in the AL position in all groups. The mean depth was 0.96 cm in Group 1, 0.95 cm in Group 2 and 3. Mean duration for localization of the vessels was 4.2 s in Group 1, 4 s in Group 2 and 4.3 s in Group 3. The differences between the groups were not significant.

CONCLUSION

This study demonstrates that the IJV cover the CA in the majority of young children. Depth of the IJV is rarely more than 1 cm deep to the skin. Ultrasound location of the IJV and CA is easy and does not necessarily delay the procedure. The findings of this study support the use of ultrasound guidance for CVC in children.

Anatomic relationship between the internal jugular vein and the carotid artery in preschool children--an ultrasonographic study

BACKGROUND

Central venous cannulation in young children is technically difficult and may lead to potentially serious complications especially when performed blindly or using anatomical landmarks only.

AIM

The aim of this study was to determine the anatomical relationship of the internal jugular vein (IJV) and the common carotid artery (CA) in preschool children using ultrasound.

METHODS

Forty five children aged 60 months and under were included prospectively and divided into three groups: group 1: <6 months, group 2: 7-18 months and group 3: 19-60 months. With the head in neutral position the location of the left and right IJV was noted as anterior (A), anterolateral (AL), lateral (L) or medial (M) in relation to the CA at the level of the cricoid cartilage. Depths of IJV and CA as well as time taken to locate the vessels were recorded.

RESULTS

The IJV was more commonly found in the AL position in all groups. The mean depth was 0.96 cm in group 1, 0.95 cm in group 2 and 3. Mean duration for localization of the vessels was 4.2 s in group 1, 4 s in group 2 and 4.3 s in group 3. The differences between the groups were not significant.

CONCLUSION

This study demonstrates that the IJV cover the CA in the majority of young children. Depth of the IJV is rarely more than 1 cm deep to the skin. Ultrasound location of the IJV and CA is easy and does not necessarily delay the procedure. The findings of this study support the use of ultrasound guidance for CVC in children.

Clinical adaptation of a pharmacokinetic model of Propofol plasma concentrations in children

BACKGROUND

A previously published pharmacokinetic simulation suggested a simple manual infusion regimen to achieve propofol plasma concentrations of 3 microg.ml(-1). This study investigated if a simple variation in propofol infusion rates is able to achieve distinct propofol plasma concentrations and whether these are close to the propofol plasma concentrations predicted by the Kataria model.

METHODS

With Research Ethics Board approval and written parental consent, a total of 17 healthy children requiring general anaesthesia were enrolled. Following inhalational induction of anaesthesia, a propofol bolus of 5 mg.kg(-1) was given and anaesthesia maintained using an adaptation of the McFarlan continuous propofol infusion regimen to achieve three distinct depths of propofol anaesthesia. Weight and propofol infusion data were used to calculate simulated propofol concentrations using the Kataria dataset and the TIVA simulation program. The performance of the infusion regimen was assessed by calculating the median performance error, median absolute performance error, wobble, and divergence.

RESULTS

Measured propofol concentrations were (mean +/- sd) 7.15 +/- 1.4, 4.3 +/- 0.85, and 2.85 +/- 0.53 microg.ml(-1) against simulation values of 6.6, 4.1, and 2.8 microg.ml(-1), respectively, at 30, 50, and 70 min using the Kataria dataset. These differences were not significant. Formal assessment of the infusion regimen's performance was acceptable.

CONCLUSION

The manual propofol infusion regimen achieved three distinct depths of propofol anaesthesia. The manual infusion regimen produced higher plasma propofol concentrations than predicted during the early part of the infusion period but was more accurate for later time points.

Duchenne muscular dystrophy: an old anesthesia problem revisited

Patients with Duchenne and Becker muscular dystrophy suffer from a progressive deterioration in muscle secondary to a defect in the dystrophin gene. As such, they are susceptible to perioperative respiratory, cardiac and other complications, such as rhabdomyolysis. Inhalational anesthetic agents have been implicated as a cause of acute rhabdomyolysis that can resemble malignant hyperthermia (MH). This article reviews perioperative 'MH-like' reactions reported in muscular dystrophy patients and groups them into three categories according to clinical presentation. The etiology and underlying pathophysiological process responsible for these reactions is discussed and recommendations are proposed for the safe anesthetic management of these patients.

Awareness during pediatric anesthesia: what is the position of European pediatric anesthesiologists?

BACKGROUND

The incidence of awareness in the pediatric population is reported as high as 1 : 125. An online survey was conducted about the current perception and practice of members of the British and French pediatric anesthesia societies regarding awareness during general anesthesia.

METHODS

Following the approval of the executive committees of the British and French pediatric anesthesia societies, members with a valid email contact address were invited to participate in a web-based survey. Perceived risk factors, use of awareness monitors, pre- and postoperative discussions of awareness as well as personal experience were enquired.

RESULTS

A total of 302 (51%) responded to the email survey. More than 60% indicated that awareness is a problem in pediatric anesthesia with the majority estimating an incidence of 1 : 1000. Almost half (49%) the respondents believe that awareness is age-dependent and 50% are not concerned below 1 month of age. More than 86% of respondents do not discuss the risk of awareness with the parents or actively look for awareness despite 27% reporting at least one episode in their practice. Intra-operative monitoring almost exclusively consists of clinical signs and endtidal anesthetic concentrations. Bispectral index (BIS) monitoring is routinely used by approximately 10% of the surveyed members.

CONCLUSIONS

This survey demonstrates that European pediatric anesthesiologists perceive awareness as a major problem. However, none seems to address the issue openly or looks for its presence routinely. The vast majority of pediatric anesthesiologists rely almost exclusively on clinical monitoring and endtidal anesthetic concentrations for its detection.

The effect of varying continuous propofol infusions on plasma cyclic guanosine 3',5'-monophosphate concentrations in anesthetized children

BACKGROUND

The glutamate-nitric oxide-cyclic guanosine 3',5'-monophosphate (cGMP) pathway is potentially an effective target for general anesthetics. Plasma cGMP concentrations are reduced after an increase in predicted plasma propofol concentrations during sedation in healthy adult volunteers. We hypothesized that an increase in measured plasma propofol concentration leads to a reduction in plasma cGMP in anesthetized children.

METHODS

Eighteen healthy children aged 46.8 (+/-19.6) mo, requiring general anesthesia for lower body surgical procedures were enrolled. After inhaled induction, tracheal intubation and initiation of intermittent positive pressure ventilation, caudal epidural analgesia was performed. Anesthesia was maintained using a continuous propofol infusion adapted from a previously published regimen to achieve predicted propofol plasma concentration of 6, 3, and 1.5 microg/mL after 30, 50, and 70 min, respectively. Samples for propofol and cGMP plasma concentrations were collected and analyzed using high-performance liquid chromatography and an enzyme immunoassay system.

RESULTS

The plasma cGMP concentrations varied significantly (median [range]) 19.2 [11.8-23.5], 21.3 [14.6-30.8], and 24.9 [15.7-37.8] nmol/L among each predicted plasma propofol concentration, P < 0.0001. The correlation coefficient (r) was -0.62.

CONCLUSIONS

This study demonstrates that an increase in plasma propofol concentration leads to a decrease in plasma cGMP in healthy children, and could serve as a biochemical marker for depth of propofol anesthesia in children.

Therapeutic hypothermia

Therapeutic hypothermia, introduced more than 5 decades ago, remains an important neuroprotective factor in the surgery for the correction of congenital heart disease, in particular when intraoperative circulatory arrest is required. Hypothermia decreases cerebral metabolism and energy consumption and reduces the extent of degenerative processes such as the excitotoxic cascade, apoptotic and necrotic cell death, microglial activation, oxidative stress, and inflammation. Neurological outcome has become the focus of several studies in the recent years, and deep hypothermic circulatory arrest durations of more than 40 minutes are associated with increased mid- and long-term disability. Physiologic cerebral flow-metabolism coupling seems to be preserved with moderate and mild hypothermia, but cerebral blood flow autoregulation is probably altered after deep hypothermic circulatory arrest, suggesting disordered cerebral metabolism and oxygen use. Although evidence from animal studies suggests potential benefit from very low temperatures, postoperative development of choreoathetosis has been found to correlate with the degree of intraoperative hypothermia, recommending the use of central temperatures greater than 15 degrees C in the clinical practice. Cooling times longer than 20 minutes are needed to obtain homogeneous brain cooling and effective neuroprotection. Finally, there is evidence that the sites of temperature monitoring used in the clinical practice may underestimate brain temperature after cardiopulmonary bypass, with the risk of postoperative hyperthermic brain damage.

The Effect of Sevoflurane on Cerebral Autoregulation in Young Children as Assessed by the Transient Hyperemic Response

The transient hyperemic response (THR) test is a simple, noninvasive technique to evaluate cerebral autoregulation using transcranial Doppler. It has not yet been used in studies involving children. In this study we evaluated this response in children undergoing general anesthesia using sevoflurane. Twenty ASA physical status I children undergoing elective urological surgery sequentially received sevoflurane at 0.5, 1.0, and 1.5 MAC in a randomized order. Analgesia was solely provided by caudal anesthesia. The right middle cerebral artery flow velocities before (F1), during (F2), and after (F3) a 10-s ipsilateral carotid artery compression were recorded. The THR ratios (THRR) (+/- sd) for 0.5 MAC, 1.0 MAC, and 1.5 MAC were 1.24 +/- 0.11, 1.16 +/- 0.09, and 1.13 +/- 0.07, respectively. The THRR was significantly different between 0.5 MAC versus 1.0 and 1.5 MAC, respectively (P < 0.05). However, no difference was detected between 1.0 and 1.5 MAC. A THRR of more than 1.09 has previously been accepted as the lower limit of a positive response. The results in this study suggest that THR is affected by sevoflurane in a dose-dependent fashion but is maintained at up to 1.5 MAC. This suggests cerebral autoregulation is preserved in children anesthetized with up to 1.5 MAC sevoflurane.

Hemodynamic and Respiratory Effects of Pediatric Urological Retroperitoneal Laparoscopic Surgery: A Prospective Study

PURPOSE

Our understanding of the effects of retroperitoneal CO(2) insufflation on cardiopulmonary variables in children remains limited. This study was designed to investigate prospectively the effect of CO(2) insufflation in a pediatric population undergoing retroperitoneal laparoscopic surgery.

MATERIALS AND METHODS

We prospectively evaluated a consecutive series of patients enrolled between July 2003 and August 2004. Anesthesia was administered following a standardized protocol. Data collection included respiratory rate, PAP, O(2) saturation, ETCO(2), HR, MAP, electrocardiogram and insufflation pressure. All variables were recorded before, during and after CO(2) insufflation at regular intervals of 1 to 2 minutes, with up to 23 measurements recorded for each period.

RESULTS

A total of 18 participants were recruited. Mean +/- SD for age and weight were 79.4 +/- 53.2 months and 26.7 +/- 15.5 kg, respectively. Mean retroperitoneal CO(2) insufflation pressure was kept at 12 mm Hg. Significant differences (p <0.05) in average ETCO(2), PAP and MAP were noted after CO(2) insufflation compared to baseline (pre-pneumoretroperitoneum) values. HR and temperature did not change. At completion of the laparoscopic intervention physiological variables exhibited a trend to return to baseline values.

CONCLUSIONS

This prospective study documents significant changes in systemic hemodynamic variables that seem to be directly associated with the insufflation of CO(2) during pediatric retroperitoneal laparoscopic surgery. This ongoing evaluation confirms the effect of laparoscopic urological surgery and CO(2) insufflation on cardiopulmonary function in children.

The temperature and humidity of inspired gases in infants using a pediatric circle system: effects of high and low-flow anesthesia

BACKGROUND

The effects of low-flow anesthesia on the temperature and humidity of the inspired gas in infants during mechanical ventilation is unknown. This study was designed to evaluate the temperature and humidity of the inspired gas in infants using a pediatric circle absorber system with high and low fresh gas flow (HFGF and LFGF) anesthesia.

METHODS

Twenty infants participated in this observational, sequential, cross-over study. Each infant was mechanically ventilated with a Kion Anesthesia Workstation, using a pediatric anesthesia circle circuit with both HFGF (6 l.min(-1)) and LFGF (0.6 l.min(-1)) technique. Airway temperature was recorded continuously at 16 sites throughout the breathing circuit. The relative humidity of the inspired gas was measured at the elbow connector adjacent to the CO2 sampling line.

RESULTS

The mean airway temperatures of the inspired gas and the changes in mean airway temperatures throughout the breathing circuit during HFGF and LFGF did not differ significantly. The mean relative humidity of the inspired gas at steady state using a LFGF technique, 33.7 +/- 3.6%, was approximately threefold greater than it was with a HFGF technique, 11.9 +/- 5.1% (P < 0.05).

CONCLUSIONS

Low-flow anesthesia with a pediatric circle system in infants neither increases the temperature of the inspired gas, nor achieves the minimum humidity of 50% reported to prevent ciliary damage, although the humidity during LFGF did increase threefold compared with HFGF. To maintain the temperature and humidity of the inspired gas during mechanical ventilation in infants, passive or active gas humidification should be used.

Cerebral blood flow velocity increases when propofol is changed to desflurane, but not when isoflurane is changed to desflurane in children

BACKGROUND

Children may exhibit delayed emergence following maintenance of anesthesia with propofol or isoflurane. Desflurane is often used towards the end of procedures to facilitate emergence. This study evaluated the effect on middle cerebral artery blood flow velocity (Vmca) in anesthetized children when propofol or isoflurane was substituted with desflurane.

METHODS

Forty-two healthy children aged 1-6 years were enrolled. A standardized anesthetic induction was used. Anesthesia was maintained with remifentanil (0.5 microg.kg(-1) bolus followed by an infusion of 0.2 microg.kg(-1).min(-1)) and a randomly selected sequence of propofol/desflurane/propofol, desflurane/propofol/desflurane, isoflurane/desflurane/isoflurane or desflurane/isoflurane/desflurane. Propofol was administered to maintain a steady-state serum concentration of 3 microg.ml(-1). Desflurane and isoflurane were administered at age-corrected 1 MAC. Hemodynamic stability was maintained. Transcranial Doppler sonography was used to measure Vmca. Hemodynamic variables as well as Vmca were measured 30 min after skin incision and repeated 30 min after each change in anesthetic maintenance agent.

RESULTS

The mean age and weight was 2.3 +/- 1.3 years and 13.0 +/- 3.7 kg, respectively. The Vmca (mean) increased by 35% from 37.7 +/- 10.5 cm s(-1) to 57.8 +/- 14.6 cm s(-1) (P < 0.0001) when propofol was changed to desflurane but was unaffected when desflurane replaced isoflurane.

CONCLUSION

When propofol is changed to desflurane, cerebral blood flow velocity increases significantly in normal children. This cerebral vasodilatory effect may have important implications in the neurosurgical setting.

The effect of remifentanil on cerebral blood flow velocity in children anesthetized with propofol

BACKGROUND

Cerebrovascular stability and rapid anesthetic emergence are desirable features of a neuroanesthetic regimen. In this randomized crossover study the effect of a low-dose remifentanil infusion on cerebral blood flow velocity (CBFV) in children anesthetized with propofol was evaluated.

METHODS

Twenty healthy children aged 1-6 years undergoing urological surgery were enrolled. Following face mask induction with sevoflurane, anesthesia was maintained with a standardized propofol infusion. Rocuronium was used to facilitate tracheal intubation and normothermia, and normocapnia were maintained. All children received a caudal epidural block, and a transcranial Doppler probe was placed to measure middle cerebral artery blood flow velocity (Vmca). Each patient received a remifentanil regimen of 0.5 microg x kg(-1) followed by 0.2 microg x kg(-1) x min(-1) in a predetermined order of remifentanil + propofol or propofol alone. Vmca, mean arterial pressure (MAP) and heart rate (HR) were recorded simultaneously at equilibrium with and without remifentanil.

RESULTS

The combination of remifentanil and propofol caused an 8.1% decrease in MAP (P = 0.0005) and an 11.8% decrease in HR (P < 0.0001) compared with propofol alone. Vmca was not different between the two groups (P = 0.4041).

CONCLUSION

The addition of remifentanil to propofol anesthesia in children causes a reduction in MAP and HR without affecting CBFV. This may imply that cerebral blood pressure autoregulation is preserved in children under propofol and remifentanil anesthesia.

The Cerebrovascular Response to Hypocapnia in Children Receiving Propofol

Hypocapnia is used to treat acute increases in intracranial pressure during neurosurgery. Cerebrovascular reactivity to carbon dioxide (CCO(2)R) is preserved above 35 mm Hg ETco(2) in children during propofol anesthesia; however, a plateau effect has been suggested below 35 mm Hg. To further delineate this phenomenon, we measured CCO(2)R by transcranial Doppler (TCD) sonography over small increments in ETco(2) in 27 healthy children. Anesthesia comprised a standardized propofol infusion and a caudal epidural block. A TCD probe was placed to measure middle cerebral artery blood flow velocity (V(mca)). ETco(2) was adjusted between 24 and 40 mm Hg at 1-2 mm Hg increments using an exogenous source of CO(2). There was an exponential relationship between ETco(2) and V(mca) above an ETco(2) value of 30 mm Hg (r = 0.82). However, V(mca) did not change with ETco(2) less than 30 mm Hg (r = 0.06). There were no significant changes in heart rate or arterial blood pressure. We conclude that when contemplating methods to decrease brain volume and intracranial pressure, hyperventilation to ETco(2) values less than 30 mm Hg may not be necessary in children receiving propofol, as no further reduction in cerebral blood flow velocity will be achieved.

Pupillary reflex dilation and skin temperature to assess sensory level during combined general and caudal anesthesia in children

BACKGROUND

Regional anesthesia causes sympathetic blockade, vasodilation and higher skin temperature in anesthetized dermatomes. Measurement of skin temperature changes might provide a useful estimate of the level of caudal anesthesia in children. Pupillary reflex dilation (PRD) allows estimation of the sensory level during combined general/epidural anesthesia in adults, but has not been assessed in children. This study was designed to evaluate skin temperature and PRD as methods of estimating sensory level in children receiving combined general/caudal epidural anesthesia.

METHODS

Twenty ASA I and II children aged 10 months-5 years were enrolled. Anesthesia was induced with sevoflurane and N2O in O2 and maintained with 1 MAC isoflurane and air in O2. Caudal epidural anesthesia was achieved by injection of 1 ml x kg(-1) 0.25% bupivacaine. Skin temperature was measured by rapid response infrared thermometry. PRD was measured using an ophthalmic ultrasound biomicroscope (UBM). The three criteria used to estimate sensory level were a drop in skin temperature of 0.5 degrees C between dermatomes, PRD of 50% and PRD of 0.2 mm.

RESULTS

A drop in skin temperature of 0.5 degrees C between dermatomes allowed estimation of the sensory level in only 20% of patients. PRD of 50%, and PRD of 0.2 mm allowed estimation of the sensory level in 45 and 100% of patients, respectively. PRD was significantly greater above the T10 dermatome compared with L2 (P < 0.01). The maximum pupillary dilation was significantly greater in children over 2 years of age [1.3 +/- 0.8 mm sd)] compared with children less than two years of age [0.6 +/- 0.3 mm sd)].

CONCLUSIONS

Skin temperature cannot be used to estimate sensory level during combined general/caudal epidural anesthesia. PRD of 0.2 mm is sensitive to the loss of analgesia but is not clinically useful. PRD may be useful above 2 years of age.

The effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with sevoflurane

To determine the effects of nitrous oxide on middle cerebral artery blood flow velocity (CBFV) during sevoflurane anaesthesia in children, CBFV was measured using transcranial Doppler sonography in 16 ASA I or II children. Anaesthesia consisted of 1.0 MAC sevoflurane in 30% oxygen with intermittent positive pressure ventilation maintaining FEco2 at 38 mmHg (5.0 kPa) and a caudal epidural block using 0.25% bupivacaine 1.0 ml.kg-1. The remainder of the inspired gas was varied in one of two sequences either air/nitrous oxide/air or nitrous oxide/air/nitrous oxide. The results showed that CBFV decreased when nitrous oxide was replaced by air (p = 0.03) and returned to its initial value when nitrous oxide was reintroduced. CBFV increased when air was replaced by nitrous oxide (p = 0.04) and returned to its initial value when air was reintroduced. Mean heart rate and blood pressure remained constant. We conclude that nitrous oxide increases cerebral blood flow velocity in healthy children anaesthetised with 1.0 MAC sevoflurane.

The effect of sevoflurane on cerebral blood flow velocity in children

BACKGROUND

Sevoflurane is a suitable agent for neuroanesthesia in adult patients. In children, cerebrovascular carbon dioxide reactivity is maintained during hypo- and normocapnia under sevoflurane anesthesia. To determine the effects of sevoflurane on middle cerebral artery blood flow velocity (Vmca) in neurologically normal children, Vmca was measured both at different MAC values and at one MAC over a specified time period, using transcranial Doppler sonography.

METHODS

Twenty-six healthy children undergoing elective urological surgery were enrolled (16 patients in part I and 10 in part II). In part I of the study anesthesia comprised sevoflurane 0.5, 1.0 and 1.5 MAC in 30% oxygen and a caudal epidural block. Once steady state had been reached at each sevoflurane MAC level, three measurements of Vmca, mean arterial pressure (MAP) and heart rate (HR) were recorded. In part II of the study patients received sevoflurane 1.0 MAC over a 90-min period, with the same variables being recorded at 15-min intervals.

RESULTS

Vmca did not vary significantly at 0.5, 1.0 and 1.5 MAC sevoflurane. There was a significant decrease in MAP between 0.5 MAC and 1.0 MAC sevoflurane (P < 0.005) and also between 1.0 MAC and 1.5 MAC (P < 0.01). There was no significant change in Vmca over 90 min at 1.0 MAC sevoflurane.

CONCLUSION

Sevoflurane does not significantly affect cerebral blood flow velocity in healthy children at working concentrations.

Hemodynamic and respiratory effect of pediatric urological laparoscopic surgery: a retrospective study

PURPOSE

We investigate the impact of extraperitoneal and intraperitoneal CO2 insufflation on cardiopulmonary variables in children undergoing laparoscopic surgery.

MATERIALS AND METHODS

The records of 73 patients who underwent laparoscopic urological surgery between December 2000 and April 2002 were retrospectively reviewed. Data collection included respiratory rate (RR), peak airway pressure (PAP), O2 saturation, end tidal CO2 (ETCO2), heart rate, systolic and diastolic blood pressure, electrocardiogram and insufflation pressure. All variables were recorded before and after CO2 insufflation. Only patients with complete records were included in the analysis.

RESULTS

The study included 62 participants. Of the patients 16 boys and 13 girls with a mean age +/- SD of 7.2 +/- 5.1 years underwent extraperitoneal surgeries, 14 partial or total nephrectomy and 5 pyeloplasty. Mean retroperitoneal CO2 insufflation pressure was 12.1 +/- 1.5 mm Hg and mean operative time was 3.6 +/- 1 hours. We operated on 13 children on the right and 16 on the left decubitus lateral position. Significant increase in ETCO2, RR and PAP was recorded after CO2 insufflation in the extraperitoneal group. Use of the left lateral position resulted in a significant increase in ETCO2 (37.1 +/- 3.6 vs 40 +/- 3.8, p = 0.04) after CO2 insufflation compared to the right decubitus lateral position. Transperitoneal surgery was performed in 32 boys and 1 girl with a mean age of 3.8 +/- 4.1 years for cryptorchidism (32) and attempted pyeloplasty (1). Mean intraabdominal CO2 insufflation pressure was 11 +/- 2.4 mm Hg and mean operative time was 1.7 +/- 0.8 hours. A significant increase in RR (16.5 +/- 3.1 vs 17.9 +/- 3.4, p = 0.0002) and PAP (13.2 +/- 4.8 vs 16.1 +/- 5.7, p <0.0001), and a decrease in O2 saturation (99.6 +/- 0.6 vs 98.7 +/- 7.1, p = 0.0003) and heart rate (116 +/- 19 vs 113 +/- 18, p = 0.019) were recorded after CO2 insufflation.

CONCLUSIONS

Our study documented significant hemodynamic and respiratory changes during pediatric laparoscopic surgeries. A similar effect on the respiratory parameters was observed in both groups. Although there were no apparent complications associated with either approach, further prospective studies are warranted to confirm the effect of laparoscopic urological surgery on cardiopulmonary function in children.

The effect of nitrous oxide on cerebrovascular reactivity to carbon dioxide in children during propofol anesthesia

Nitrous oxide (N(2)O) increases cerebral blood flow when used alone and in combination with propofol. We investigated the effects of N(2)O on cerebrovascular CO(2) reactivity (CCO(2)R) during propofol anesthesia in 10 healthy children undergoing elective urological surgery. Anesthesia consisted of a steady-state propofol infusion and a continuous caudal epidural block. A transcranial Doppler probe was used to measure middle cerebral artery blood flow velocity. Randomization determined the sequence order of N(2)O (N(2)O/air or air/N(2)O) and end-tidal (ET)CO(2) concentration (25, 35, 45, and 55 mm Hg) using an exogenous source of CO(2). At steady state, three sets of measurements of middle cerebral artery blood flow velocity, mean arterial blood pressure, and heart rate were recorded. A linear preservation of CCO(2)R was observed above 35 mm Hg of ETCO(2), irrespective of N(2)O. A decrease in CCO(2)R to 1.4%-1.9% per millimeters of mercury was seen in the hypocapnic range (ETCO(2) 25-35 mm Hg) with both air and N(2)O. We conclude that N(2)O does not affect CCO(2)R during propofol anesthesia in children. When preservation of CCO(2)R is required, the combination of N(2)O with propofol anesthesia in children would seem suitable. The cerebral vasoconstriction caused by propofol would imply that hyperventilation to ETCO(2) values less than 35 mm Hg may not be required because no further reduction in cerebral blood flow velocity would be achieved.

Effect of nitrous oxide on cerebrovascular reactivity to carbon dioxide in children during sevoflurane anaesthesia

BACKGROUND

Sevoflurane and nitrous oxide have intrinsic cerebral vasodilatory activity. To determine the effects of nitrous oxide on cerebrovascular reactivity to carbon dioxide (CCO(2)R) during sevoflurane anaesthesia in children, middle cerebral artery blood flow velocity (V(mca)) was measured over a range of end-tidal carbon dioxide concentrations (E'(CO(2))), using transcranial Doppler (TCD) ultrasonography.

METHODS

Ten children aged 1.5-6 yr were anaesthetized with sevoflurane and received a caudal block. Patients were allocated randomly to receive either air-nitrous oxide or nitrous oxide-air. Further randomization determined the sequence of E'(CO(2)) (25, 35, 45, and 55 mm Hg) and sevoflurane (1.0 then 1.5 MAC or 1.5 then 1.0 MAC) concentrations. Once steady state had been reached, three measurements of V(mca), mean arterial pressure (MAP), and heart rate (HR) were recorded.

RESULTS

Cerebrovascular carbon dioxide reactivity was reduced in the 25-35 mm Hg E'(CO(2)) range on the addition of nitrous oxide to 1.5 MAC, but not 1.0 MAC sevoflurane. A plateau in CCO(2)R of 0.4-0.6% per mm Hg was seen in all groups between E'(CO(2)) values of 45 and 55 mm Hg. Mean HR and MAP remained constant throughout the study period.

CONCLUSIONS

Cerebrovascular carbon dioxide reactivity is reduced at and above an E'(CO(2)) of 45 mm Hg during 1.0 and 1.5 MAC sevoflurane anaesthesia. The addition of nitrous oxide to 1.5 MAC sevoflurane diminishes CCO(2)R in the hypocapnic range. This should be taken into consideration when hyperventilation techniques for reduction of brain bulk are being contemplated in children with raised intracranial pressure.

Cerebral blood flow velocity in children anaesthetized with desflurane

BACKGROUND

Desflurane allows for rapid emergence and changes in depth of anaesthesia which makes it especially suitable for neuroanaesthesia. This study was designed to determine the effects of different desflurane concentrations on cerebral blood flow velocity (CBFV) in healthy children.

METHODS

Twenty children, aged 1-7 years undergoing urological surgery were studied. Anaesthesia was induced with sevoflurane in oxygen. After tracheal intubation, sevoflurane was discontinued and ventilation with desflurane in air/oxygen was initiated and normoventilation maintained. A caudal block was performed. The patients were randomized to receive three different desflurane concentrations (0.5, 1.0 and 1.5 MAC). Fifteen minutes were allowed to reach steady-state at which time CBFV was measured by transcranial Doppler sonography. Mean arterial pressure (MAP) and heart rate (HR) were simultaneously recorded at 1-min intervals.

RESULTS

Cerebral blood flow velocity increased from 0.5 to 1.0 MAC (P < 0.05), but not from 1.0 to 1.5 MAC. HR increased from 0.5 to 1.0 (P < 0.001) and from 1.0 to 1.5 MAC (P < 0.001), whereas the MAP decreased only from 0.5 to 1.0 MAC (P < 0.001).

CONCLUSIONS

Desflurane in concentrations of 1.0 and 1.5 MAC in children increases CBFV significantly when compared with 0.5 MAC. These changes were associated with a significant increase in HR and decrease in MAP.

The effect of nitrous oxide on cerebral blood flow velocity in children anesthetized with propofol

BACKGROUND

Propofol for maintenance of anesthesia by continuous infusion is gaining popularity for use in pediatric patients. Nitrous oxide (N2O) has been shown to increase cerebral blood flow velocity (CBFV) in both children and adults. To determine the effects of N2O on middle cerebral artery blood flow velocity (Vmca) during propofol anesthesia in children, Vmca was measured with and without N2O using transcranial Doppler (TCD) sonography.

METHODS

Thirty ASA I or II children aged 18 months to 6 years undergoing elective urological surgery were enrolled. Anesthesia comprised propofol aimed at producing an estimated steady-state serum concentration of 3 micro g.ml-1 and a caudal epidural block. A transcranial Doppler probe was used to measure middle cerebral artery blood flow velocity. Each patient was randomized to receive a sequence of either Air/N2O/Air or N2O/Air/N2O in 35% oxygen. Fifteen min after each change in the N2O concentration, three measurements of cerebral blood flow velocity, blood pressure and heart rate were recorded. Ventilatory parameters and EtCO2 were kept constant throughout the study period.

RESULTS

CBFV increased by 12.4% when air was replaced by N2O, and returned to baseline when N2O was subsequently removed. There was a 14% decrease in CBFV when N2O was replaced with air, which increased to baseline when air was subsequently replaced with N2O. Mean heart rate and blood pressure remained constant throughout the study period.

CONCLUSION

The effects of nitrous oxide on CBFV are preserved in children during propofol anesthesia.

Cerebrovascular reactivity to carbon dioxide is preserved during hypocapnia in children anesthetized with 1.0 MAC, but not with 1.5 MAC desflurane

PURPOSE

Maintenance of cerebrovascular reactivity to CO(2) (CCO(2)R) is important during neurosurgical anesthesia. This study was designed to determine the effect of different desflurane concentrations on CCO(2)R in children.

METHODS

Children undergoing urological surgery were enrolled. Anesthesia was induced with sevoflurane in air/oxygen. After intubation, sevoflurane was switched to desflurane. Analgesia was provided with an epidural neuraxial block. Mechanical ventilation was adjusted to an initial EtCO(2) of 30 mmHg. Exogenous CO(2) was used to achieve an EtCO(2) of 40 and 50 mmHg. Patients were randomized to the sequence of desflurane concentration (1.0 and 1.5 MAC) and the EtCO(2). Transcranial Doppler was used to measure middle cerebral artery blood flow velocity (Vmca). Five minutes were allowed to reach steady state after each change in EtCO(2) and 15 min after changing the desflurane concentration.

RESULTS

Sixteen patients were studied. The mean age and weight were 3.5 +/- 1.5 yr and 14.4 +/- 3.1 kg, respectively. Mean arterial pressure remained stable throughout the study, while at an EtCO(2) of 50 mmHg, heart rate decreased at both desflurane concentrations (P < 0.05). At 1.0 MAC, Vmca increased from 30 to 40 mmHg (P < 0.05), but not from 40 to 50 mmHg EtCO(2). At 1.5 MAC, Vmca increased between 30 and 50 mmHg (P < 0.05).

CONCLUSION

CCO(2)R is preserved during hypocapnia in children anesthetized with 1.0 MAC, but not with 1.5 MAC desflurane. The lack of further increase in Vmca at higher EtCO(2) concentrations implies that desflurane may cause significant cerebral vasodilatation in children. This may have important implications in children with reduced intracranial compliance.

The effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with desflurane

The aim of this study was to determine the effect of nitrous oxide on cerebral blood flow velocity in children anaesthetised with desflurane. Eighteen healthy children scheduled for elective surgery were enrolled into the study. Anaesthesia was induced using sevoflurane, and a caudal block was performed following tracheal intubation. Anaesthesia was maintained with 1 age-adjusted MAC desflurane. A transcranial Doppler probe was used to measure middle cerebral artery blood flow velocity. Each patient was randomised to receive a sequence of either air/nitrous oxide/air or nitrous oxide/air/nitrous oxide in 30% oxygen. Fifteen minutes after each change in the nitrous oxide concentration, three measurements of cerebral blood flow velocity, blood pressure and heart rate were recorded. Neither the addition nor removal of nitrous oxide caused any significant changes in middle cerebral artery blood flow velocity, heart rate or blood pressure. This may be due to a more potent cerebral vasodilatory effect of desflurane in children.