The effect of dexmedetomidine on motor-evoked potentials during pediatric posterior spinal fusion surgery: a retrospective case-control study.

PURPOSE: Motor-evoked potentials (MEPs) are frequently used in pediatric posterior spinal fusion surgery (PSFS) to detect spinal cord ischemia. Dexmedetomidine is increasingly being used as an adjunct to total intravenous anesthesia, but its effect on MEP amplitude has been variably reported. The purpose of this study was to evaluate the effect of an infusion of dexmedetomidine on the amplitude of MEPs. METHODS: We performed a retrospective case-control study of 30 pediatric patients who received a 0.5 µg·kg-1·hr-1 infusion of dexmedetomidine, ten patients who received 0.3 µg·kg-1·hr-1 dexmedetomidine, and 30 control patients who did not receive dexmedetomidine during PSFS. Two neurophysiologists reviewed the MEP amplitudes in six muscle groups at three time points: when the patient was turned prone (baseline; T1), one hour after incision (T2), and after exposure of the spine but before insertion of the first screw (T3). RESULTS: In all muscles tested, the mean MEP amplitude was reduced by T3 when dexmedetomidine was infused at 0.5 µg·kg-1·hr-1. The greatest reduction from baseline MEP amplitude was 829 µV (95% confidence interval, 352 to 1230; P < 0.001) seen in first right dorsus interosseous. When dexmedetomidine was infused at 0.3 µg·kg-1·hr-1, there was a significant reduction in MEP amplitude in four of the six muscles tested at T3 compared with the control group. CONCLUSIONS: Dexmedetomidine at commonly used infusion rates of 0.3 µg·kg-1·hr-1 or 0.5 µg·kg-1·hr-1 causes a significant decrease in MEP amplitude during pediatric PSFS. We suggest that dexmedetomidine should be avoided in children undergoing PSFS so as not to confuse the interpretation of this important neurophysiological monitor.

RéSUMé: OBJECTIF: Les potentiels évoqués moteurs (PEM) sont fréquemment utilisés lors de chirurgies de fusion spinale postérieure chez l'enfant afin de détecter une ischémie de la moelle épinière. La dexmédétomidine est de plus en plus utilisée comme adjuvant à l'anesthésie intraveineuse totale, mais son effet sur l'amplitude des PEM n'a été rapporté que de façon variable. L'objectif de cette étude était d'évaluer l'effet d'une perfusion de dexmédétomidine sur l'amplitude des PEM. MéTHODE: Pendant une chirurgie de fusion spinale postérieure, nous avons réalisé une étude cas témoins rétrospective auprès de 30 patients pédiatriques ayant reçu une perfusion 0,5 µg·kg−1·h−1 de dexmédétomidine, 10 patients ayant reçu 0,3 µg·kg−1·h−1 de dexmédétomidine, et 30 patients témoins n'ayant pas reçu de dexmédétomidine. Deux neurophysiologistes ont passé en revue les amplitudes des PEM dans six groupes musculaires à trois moments de la chirurgie : lorsque le patient a été tourné sur le ventre (valeur de base; T1), une heure après l'incision (T2), et après l'exposition de la colonne mais avant l'insertion de la première vis (T3). RéSULTATS: Dans tous les muscles testés, l'amplitude moyenne des PEM était réduite à T3 lorsque la dexmédétomidine était perfusée à 0,5 µg·kg−1·h−1. La plus grande réduction par rapport à l'amplitude de base des PEM était de 829 µV (intervalle de confiance 95 %, 352 à 1230; P < 0,001) et a été observée au niveau du premier interosseux dorsal. Lorsque la dexmédétomidine était perfusée à 0,3 µg·kg−1·h−1, une réduction significative de l'amplitude des PEM a été observée dans quatre des six muscles testés à T3 par rapport au groupe témoin. CONCLUSION: La dexmédétomidine, administrée à des taux de perfusion fréquemment utilisés de 0,3 µg·kg−1·h−1 ou 0,5 µg·kg−1·h−1, a entraîné une réduction significative de l'amplitude des PEM pendant une chirurgie de fusion spinale postérieure chez l'enfant. Nous proposons d'éviter l'administration de dexmédétomidine chez les enfants devant subir une chirurgie de fusion spinale postérieure afin de ne pas brouiller l'interprétation de ce moniteur neurophysiologique important.

Recommendations for the management of MPS IVA: systematic evidence- and consensus-based guidance.

INTRODUCTION: Mucopolysaccharidosis (MPS) IVA or Morquio A syndrome is an autosomal recessive lysosomal storage disorder (LSD) caused by deficiency of the N-acetylgalactosamine-6-sulfatase (GALNS) enzyme, which impairs lysosomal degradation of keratan sulphate and chondroitin-6-sulphate. The multiple clinical manifestations of MPS IVA present numerous challenges for management and necessitate the need for individualised treatment. Although treatment guidelines are available, the methodology used to develop this guidance has come under increased scrutiny. This programme was conducted to provide evidence-based, expert-agreed recommendations to optimise management of MPS IVA. METHODS: Twenty six international healthcare professionals across multiple disciplines, with expertise in managing MPS IVA, and three patient advocates formed the Steering Committee (SC) and contributed to the development of this guidance. Representatives from six Patient Advocacy Groups (PAGs) were interviewed to gain insights on patient perspectives. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with experience managing patients with MPS IVA and the manuscript was evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers. RESULTS: A total of 87 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) disease-modifying interventions (enzyme replacement therapy [ERT] and haematopoietic stem cell transplantation [HSCT]); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions (including spinal, limb, ophthalmic, cardio-thoracic and ear-nose-throat [ENT] surgeries). Consensus was reached on all statements after two rounds of voting. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance). CONCLUSION: This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS IVA and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Recommendations for the management of MPS VI: systematic evidence- and consensus-based guidance.

INTRODUCTION: Mucopolysaccharidosis (MPS) VI or Maroteaux-Lamy syndrome (253200) is an autosomal recessive lysosomal storage disorder caused by deficiency in N-acetylgalactosamine-4-sulfatase (arylsulfatase B). The heterogeneity and progressive nature of MPS VI necessitates a multidisciplinary team approach and there is a need for robust guidance to achieve optimal management. This programme was convened to develop evidence-based, expert-agreed recommendations for the general principles of management, routine monitoring requirements and the use of medical and surgical interventions in patients with MPS VI. METHODS: 26 international healthcare professionals from various disciplines, all with expertise in managing MPS VI, and three patient advocates formed the Steering Committee group (SC) and contributed to the development of this guidance. Members from six Patient Advocacy Groups (PAGs) acted as advisors and attended interviews to ensure representation of the patient perspective. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with expertise and experience managing patients with MPS VI and the manuscript has been evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers. RESULTS: A total of 93 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions. Consensus was reached on all statements after two rounds of voting. The greatest challenges faced by patients as relayed by consultation with PAGs were deficits in endurance, dexterity, hearing, vision and respiratory function. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance). CONCLUSION: This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS VI and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Midline posterior glossectomy and lingual tonsillectomy in obese and nonobese children with down syndrome: Biomarkers for success.

OBJECTIVES/HYPOTHESIS: To examine outcomes following midline posterior glossectomy (MPG) plus lingual tonsillectomy (LT) for the treatment of significant obstructive sleep apnea (OSA) in children with Down syndrome (DS). METHODS: Patients with DS who had persistent OSA following tonsillectomy and adenoidectomy (TA) and were relatively intolerant of positive airway pressure (PAP) therapy were evaluated by physical examination and sleep/CINE magnetic resonance imaging to determine the etiology of upper airway obstruction. Patients with relative macroglossia underwent MPG plus LT if required. Successful surgical outcome was defined as the resolution of OSA or the ability to tolerate PAP. RESULTS: Thirteen children (8 male, 5 female), mean (standard deviation) age 14.2 (4.0) years underwent MPG plus LT. Fifty-four percent of patients were obese (Body mass index [BMI] > 95th centile) and 8% were overweight (BMI 85th-95th centile) preoperatively. All patients underwent pre- and postoperative polysomnography. Postoperatively, the obstructive apnea-hypopnea index fell significantly from 47.0/hour to 5.6/hour (P <.05) in normal weight individuals who did not become obese, but not in obese patients or those who became obese postoperatively. Successful surgical outcome was seen in all (N = 6) children who were normal weight or overweight preoperatively compared with none who were obese preoperatively (N = 7). CONCLUSION: Midline posterior glossectomy and LT are beneficial in normal weight and overweight children with DS who have persistent OSA following TA and are intolerant of PAP therapy. Obesity pre- or postoperatively portends a worse prognosis following MPG, suggesting that aggressive weight loss initiatives should be considered as an adjunct to surgery in this population. LEVEL OF EVIDENCE: 4. Laryngoscope, 127:757-763, 2017.

Repeated nonanesthetic malignant hyperthermia reactions in a child.

A series of life-threatening nonanesthetic-related MH reactions in a child was the inspiration for a proactive, novel solution allowing for early prehospital, potentially lifesaving intravenous dantrolene administration. Multidisciplinary collaboration is essential and parent education must be comprehensive and ongoing. This case underlines the importance of considering nonanesthetic MH susceptibility in the child who has a history of unspecified myopathy and who presents with fever and total body stiffness.

Managing the challenging pediatric airway: Continuing Professional Development.

PURPOSE: This module will give the anesthesia provider the information needed to identify, prepare for, and clinically manage a difficult airway in children. PRINCIPAL FINDINGS: Although the incidence of difficult intubation is lower in children than in adults, the anesthesiologist who even occasionally cares for children must be prepared to manage the pediatric patient with a known or suspected difficult airway. Many of the predictors of a difficult intubation that are useful in adults do not apply to children. Predictably, many children with a challenging airway also have a syndrome or diagnosis known to be associated with difficult intubation. Due to the unique emotional, physiological, and anatomical characteristics of small children, the approach to airway management is different from that in adults. Awake intubation is almost never an option, and recently, there has been a trend towards using cuffed tracheal tubes and apneic intubation. The flexible fibrescope has seen less action as the sole intubating device with the recent introduction of the various video laryngoscopes designed for pediatric use. Supraglottic airways are now being used in children with a difficult airway, not only as a rescue device in the event of failed intubation but also as a first-choice airway device and as a conduit for tracheal intubation. CONCLUSION: Although direct laryngoscopy can still be used to manage the care of the majority of children with a known or suspected challenging airway, there is now a noticeable trend towards the use of a supraglottic airway and apneic intubation using fibreoptic and video laryngoscopic equipment.

US-guided percutaneous needle biopsy of anterior mediastinal masses in children.

BACKGROUND: Anterior mediastinal masses in children are clinically challenging, requiring prompt histological diagnosis. OBJECTIVE: The purpose of this study was to review the experience with US-guided percutaneous core needle biopsy (PCNB) of anterior mediastinal masses in children, particularly with respect to safety and diagnostic accuracy. MATERIALS AND METHODS: We retrospectively reviewed the clinical presentation, imaging, sedation approach, procedural details and pathology results of US-guided PCNB of mediastinal masses that occurred during an 8-year period (2001-2008). Complications were graded and pathology was categorized into four groups based on adequacy and diagnostic yield. RESULTS: 32 US-guided PCNBs were performed on 32 children, mean age 12 years (range 18 months to 17 years), mean weight 48 kg (range 11.5 to 109 kg, median 49 kg). A coaxial US-guided technique was used, with a mean of 8.2 passes and a mean 7.6 cores obtained (range 2-15). There were no major complications. The biopsies were adequate in volume and quality of specimens in 29/32, and 25/32 were diagnostic. PCNB was diagnostic in all cases of non-Hodgkin disease. CONCLUSIONS: Experience with anterior mediastinal masses suggests that US-guided PCNB can be considered a viable, safe and accurate method of reaching a diagnosis in the pediatric population.

Physiological changes in transperitoneal versus retroperitoneal laparoscopy in children: a prospective analysis.

PURPOSE: The choice of minimally invasive surgical approaches in pediatric urology is largely influenced by surgeon preference and experience. Little is known about the differences in physiological variables that might objectively influence the choice of surgical approach. We compared the cerebral and systemic hemodynamic effects of transperitoneal vs retroperitoneal CO(2) insufflation in children. MATERIALS AND METHODS: After receiving ethical review board approval and written parental consent 36 pediatric patients undergoing transperitoneal (18) or retroperitoneal (18) laparoscopic surgery were enrolled in this study. A standardized anesthetic technique of isoflurane 1 MAC and remifentanil 0.2 mcg/kg per minute was used. Measured parameters included end tidal CO(2), middle cerebral artery blood flow velocity, heart rate and noninvasive mean arterial blood pressure. Transcranial Doppler ultrasound was used to measure middle cerebral artery blood flow velocity. Data were collected before, during and after CO(2) insufflation to 12 mm Hg pneumoperitoneum at regular intervals, including every minute for 10 minutes and every 2 minutes thereafter. Within group analysis was done using repeated measures ANOVA. Nonlinear regression analysis was used to determine the best fit and the relationship of each variable with time with p <0.05 considered significant. RESULTS: Patient age and weight were comparable in the 2 groups. Transperitoneal CO(2) insufflation resulted in a rapid parallel increase in middle cerebral artery blood flow velocity, mean arterial pressure and end tidal CO(2) during the first 8 minutes of pneumoperitoneum (p <0.05). Despite a continued increase in end tidal CO(2) thereafter middle cerebral artery blood flow velocity and mean arterial pressure attained a plateau within the first 8 minutes (p <0.05). In contrast, middle cerebral artery blood flow velocity and end tidal CO(2) increased progressively throughout the retroperitoneal CO(2) insufflation period (p <0.01). CONCLUSIONS: Cerebral blood flow velocity and end tidal CO(2) seem to increase progressively and gradually during retroperitoneal laparoscopy, in contrast to the more rapid increase and plateau effect during transperitoneal laparoscopy. Presumably the smaller absorptive surface in the retroperitoneal space explains this physiological difference.

Percutaneous interventional radiology procedures in patients with epidermolysis bullosa: modifications and challenges.

OBJECTIVE: The purpose of this study is to describe the role of interventional radiology in palliation and maintenance of nutritional support in children with epidermolysis bullosa, with a focus on safety and required procedural modifications. MATERIALS AND METHODS: This was a retrospective study of all patients diagnosed with epidermolysis bullosa who underwent interventional radiology procedures between January 1991 and December 2008 at a pediatric tertiary care institution. The type of epidermolysis bullosa, the patient's age, the indication and type of interventional radiology procedure, modifications used, and complications were recorded. RESULTS: Fifteen patients (9 boys and 6 girls) with a diagnosis of epidermolysis bullosa underwent a total of 87 procedures during 82 different patient interventional radiology visits. Twenty-seven esophageal dilatations for symptoms of dysphagia, 11 percutaneous gastrostomy tube placements resulting from failure to thrive, 30 maintenance procedures, 15 central venous access device insertions, and three other procedures (nasojejunal tube insertion, liver biopsy, and inferior vena cava filter insertion) were performed. Modifications were related to anesthetic management, access, tissue handling, and dressings. Complications were categorized according to Society of Interventional Radiology grades: Minor A (n = 6), Minor B (n = 4), Major C (n = 7), Major D (n = 2), Major E (n = 0), and Major F (n = 0). CONCLUSION: Our experience suggests that interventional radiology procedures can be done successfully and safely when utmost care is given to skin and mucosal protection. Wound healing is adequate and should not deter intervention.

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.

Management of the patient with a large anterior mediastinal mass: recurring myths.

PURPOSE OF REVIEW: This editorial review summarizes the current anesthetic management of patients with anterior mediastinal masses. RECENT FINDINGS: With increased appreciation of the correct intraoperative management of these cases severe intraoperative respiratory or cardiovascular collapse is less likely to occur during general anesthesia. Maintenance of spontaneous ventilation is the anesthetic goal whenever possible. Major life-threatening complications now occur more frequently postoperatively. SUMMARY: General anesthesia is not safe in patients with severe positional symptoms from an anterior mediastinal mass. With modern imaging techniques, general anesthesia is rarely needed for diagnostic procedures in these patients. Preoperative flow-volume loops are not useful in the management of these patients and the concept of cardiopulmonary bypass on 'standby' is not appropriate during induction of anesthesia.

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 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.

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.

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.

Cerebrovascular carbon dioxide reactivity in children anaesthetized with propofol.

BACKGROUND: Propofol, by virtue of its favourable pharmacokinetic profile, is suitable for maintenance of anaesthesia by continuous infusion during neurosurgical procedures in adults. It is gaining popularity for use in paediatric patients. To determine the effects of propofol on carbon dioxide cerebrovascular reactivity in children, middle cerebral artery blood flow velocity was measured at different levels of endtidal (PECO2) by transcranial Doppler sonography. METHODS: Ten ASA I or II children, aged 1-6 years undergoing elective urological surgery were enrolled. Anaesthesia comprized propofol aimed at producing an estimated steady-state serum concentration of 3 microg x ml-1 and a caudal epidural block. PECO2 was adjusted randomly in an increasing or decreasing fashion between 3.3, 5.2 and 7.2 kPa (25, 40 and 55 mmHg) with an exogenous source of CO2 while maintaining ventilation parameters constant. RESULTS: Cerebral blood flow velocity increased as PECO2 increased from 3.3 to 5.2 kPa (25-40 mmHg) (P < 0.001) and from 5.2 to 7.2 kPa (40-55 mmHg) (P < 0.001). Mean heart rate and blood pressure did not change significantly. CONCLUSIONS: This study demonstrates that cerebrovascular CO2 reactivity is maintained over PECO2 values of 3.3, 5.2 and 7.2 kPa (25, 40 and 55 mmHg) in healthy children anaesthetized with propofol.

Fentanyl is more effective than remifentanil at preventing increases in cerebral blood flow velocity during intubation in children.

PURPOSE: Controlling the cerebral and systemic hemodynamic responses to laryngoscopy and tracheal intubation may play a role in determining clinical outcome in pediatric neurosurgical patients. This study compared the effects of remifentanil and fentanyl on cerebral blood flow velocity (CBFV) and hemodynamic profile during laryngoscopy and tracheal intubation in children under sevoflurane anesthesia. METHODS: Sixty healthy children aged two to six years undergoing dental surgery under general anesthesia were enrolled. Each child was randomly assigned to receive a remifentanil or fentanyl infusion, at a rate of 0.75, 1.0, or 1.5 microg x kg(-1) x min(-1) after induction of anesthesia with 2% sevoflurane. Middle cerebral artery blood flow velocity was measured by transcranial Doppler (TCD) sonography. Once a baseline set of hemodynamic variables and TCD measurements were recorded, the opioid infusion was started. Measurements were taken at two-minute intervals, starting four minutes prior to laryngoscopy until four minutes following naso-tracheal intubation. RESULTS: Remifentanil caused a more significant decrease in mean arterial pressure and CBFV prior to tracheal intubation than did fentanyl (P < 0.001). During laryngoscopy and for two minutes following tracheal intubation, CBFV increased in all remifentanil groups (P < 0.05), whereas it remained stable in all fentanyl groups. CONCLUSION: This study suggests that fentanyl was more effective than remifentanil at preventing increases in CBFV during and immediately following laryngoscopy and tracheal intubation in children undergoing sevoflurane anesthesia. Fentanyl also seemed to provide a more stable hemodynamic profile prior to laryngoscopy and tracheal intubation when compared to remifentanil.