Andrea Irouschek

Incidence and predictors of difficult laryngoscopy in 11.219 pediatric anesthesia procedures

Objective:  Difficult laryngoscopy in pediatric patients undergoing anesthesia.

A priming technique accelerates onset of neuromuscular blockade at the laryngeal adductor muscles

PurposePriming is a known technique to accelerate onset of neuromuscular blockade (NMB). Its effect on NMB of the larynx has not been studied yet.MethodsWe compared a priming technique with a bolus application of rocuronium on the onset of NMB at the laryngeal adductor and the adductor pollicis muscles (AP). In 30 female patients, after induction of anesthesia a tube with a surface electrode was placed into the trachea prior to the administration of any neuromuscular blocking agent to monitor electromyography (EMG) of the laryngeal adductor muscles. Neuromuscular monitoring consisted of EMG of the laryngeal adductor muscles and the left AR Patients were randomized into two groups. After transcutaneous stimulation of the recurrent laryngeal nerve and ulnar nerve, a bolus of rocuronium 0.6 mg·kg−1 (Bolus group) or a priming dose of rocuronium 0.06 mg·kg−1 followed by rocuronium 0.54 mg·kg−1 three minutes later (Priming group) were injected. Lag time, onset 90%, onset time and peak effect of NMB were recorded and compared; aP < 0.05 was considered significant.ResultsThe onset 90% and onset time measured at the laryngeal adductor muscles (onset: 44.7 ± 7.4vs 74.0 ± 23.8 sec) and at the AP (onset: 105.4 ± 29.9vs 139.2 ±51.5 sec) were significantly shorter in the Priming group than in the Bolus group. Within groups, the onset times were significantly shorter at the laryngeal muscles in comparison to ARConclusionOur results indicate that a priming technique with rocuronium significantly accelerates the onset of NMB at the laryngeal adductor muscles. Our results further support the use of rocuronium as an alternative to succinylcholine for rapid sequence induction.RésuméObjectifLamorçage est une technique connue pour accélérer l’installation du blocage neuromusculaire (BNM). Son effet sur le BNM du larynx n’a pas encore été étudié.MéthodeNous avons comparé une technique d’amorçage et l’injection de bolus de rocuronium au début du BNM de l’adducteur du larynx et de l’adducteur du pouce (AP). Après l’induction de l’anesthésie chez 30 patientes, un tube muni d’une électrode superficielle a été placé dans la trachée avant l’administration d’agent myorelaxant pour permettre le monitorage électromyographique (EMG) des muscles adducteurs du larynx. Le monitorage de la transmission neuromusculaire consistait à l’EMG des muscles adducteurs du larynx et de l’AP gauche. Les patientes ont été réparties aléatoirement en deux groupes. Après la stimulation transcutanée du nerf laryngé récurrent et des nerfs cubitals, un bolus de rocuronium de 0,6 mg·kg−1 (groupe Bolus) ou une dose d’amorçage de 0,06 mg·kg−1 de rocuronium suivis de 0,54 mg·kg−1 de rocuronium trois minutes plus tard (groupe Amorçage) ont été injectés. La période latence, le moment où le bloc est installé à 90 %, le délai d’installation et le moment de l’effet maximal du BNM ont été notés et comparés; un P < 0,05 était considéré significatif.RésultatsLe bloc neuromusculaire à 90 % et le délai d’installation mesurés aux adducteurs du larynx (début: 44,7 ± 7,4 vs 74,0 ± 23,8 sec) et à l’AP (début: 105,4 ± 29,9 vs 139,2 ± 51,5 sec) ont été signifcativement plus courts dans le groupe Amorçage que dans le groupe Bolus. A l’intérieur des groupes, les délais d’installation du bloc ont été significativement plus courts aux muscles laryngés qu’à l’AP.ConclusionUne technique d’amorçage avec du rocuronium accélère de façon significative l’installation du BNM aux muscles adducteurs du larynx. De plus, nos résultats sont en faveur de l’usage de rocuronium pour remplacer la succinylcholine dans l’induction en séquence rapide.

Anesthetic management of patients with ornithine transcarbamylase deficiency

Ornithine transcarbamylase deficiency (OTCD) is the most common inborn error of the urea cycle. Several specific factors require care during anesthesia in patients with this condition to avoid metabolic decompensation with acute hyperammonemia and encephalopathy. We report monozygous twins with severe neonatal‐onset OTCD undergoing general anesthesia twice each, with midazolam, s‐ketamine, fentanyl and isoflurane in combination with surgical field infiltration with ropivacaine. Alternative pathway medication and high‐caloric diet with 10% glucose solutions were continuously administered during the perioperative course. Both children were extubated within 10 min of the final suture, and their neurological state remained unchanged. Perioperatively, blood ammonia levels remained within the normal range.

Incidence and predictors of poor laryngoscopic view in children undergoing pediatric cardiac surgery.

OBJECTIVE Previous investigations reported a higher incidence of poor laryngoscopic views in pediatric patients undergoing cardiac surgery. The objective of this study was to analyze why children undergoing cardiac surgery have such an increased incidence of poor laryngoscopic views during anesthesia induction. DESIGN This study was designed as a retrospective analysis. SETTING This analysis was based on a single-center cohort of a university hospital. PARTICIPANTS One thousand one hundred seventy-seven general anesthesia procedures, including a direct laryngoscopic view over a period of 6 consecutive years, in pediatric patients undergoing cardiac surgery. INTERVENTIONS Because of the retrospective character of this study, there were no study-related interventions. MEASUREMENTS AND MAIN RESULTS Poor laryngoscopic views were defined as Cormack and Lehane (CML) grade III and IV. The overall incidence of poor laryngoscopic views was 3.5%. In patients younger than 1 year of age, the incidence of CML III or IV was significantly higher than in the older patients (5.6% v 1.7%). None of the patients with CML III/IV findings had Down syndrome; whereas in 9 of 41 patients with CML grade III/IV, a concomitant congenital syndrome like DiGeorge syndrome or CHARGE syndrome was found. CONCLUSIONS The general incidence of CML III/IV findings during the induction of anesthesia for pediatric cardiac surgery is more than twice as high as reported in unselected pediatric cohorts. In patients below 1 year of age and in male patients, difficult laryngoscopy is more frequent. Concomitant Down syndrome was not associated with difficult laryngoscopy.

Recurrent laryngeal nerve monitoring during esophagectomy and mediastinal lymph node dissection: a novel approach using a single-lumen endotracheal EMG tube and the EZ-blocker.

To the Editor, We read with great interest the article by Gelpke and coworkers, who report their experience with recurrent laryngeal nerve (RLN) monitoring during esophagectomy and mediastinal lymph node dissection using a laryngeal surface electromyography (EMG) electrode attached to a doublelumen endobronchial tube in 12 consecutive patients [1]. Postoperative impairment and damage of the RLN has an incidence up to 31 % in left lung resection for malignancy [2] and between 34 and 80 % for surgery for esophageal cancer [3, 4]. We agree and support the thesis that intraoperative monitoring of the RLN may facilitate identification of the nerve during esophagectomy and lung surgery and may reduce the incidence of RLN injury. For successful monitoring of the RLN accurate positioning of the surface electrodes between the vocal cords is crucial. However, because of the small dimension of electrode recording part (1.5 9 1.5 cm), maintaining positioning could be challenging with a double-lumen endotracheal tube after the patient is brought into a lateral position. Therefore, we like to add a possible refinement to the method applied in another case report of a patient undergoing abdomino-right-thoracic-esophagectomy [5]. To cover a larger recording electrode area [5], we attach two surface electrodes, one after the other, on the double-lumen endobronchial tube starting 2 cm above the tracheal cuff. After patient positioning into the left lateral position, the RLN is stimulated transcutaneously. The surface electrode that obtains the better recording results is used for intraoperative monitoring. Generally, a double-lumen endobronchial tube is prone to displacement during patient positioning and surgery. Repositioning an electrode-bearing endobronchial tube interferes with single-lung ventilation. Gelpke and coworkers measured the distance between the true vocal cord and the main bronchus on the preoperative computed tomography (CT) scan to establish the ideal position of the surface electrode on the endobronchial tube; however, in one nerve at risk, electromyographic (EMG) recording was impossible. A possible explanation—most likely a displaced electrode—could be anatomic: e.g., the distance between vocal cord and main bronchus may differ between supine position (CT scan) and left lateral position (singlelung ventilation). However, after considering the risk of electrode displacement and trauma from in situ detachment of the surface electrode, we now use a ready-made EMGendotracheal tube system (Xomed-EMG-tube; Medtronic Xomed, Jacksonville, FL) in combination with a newly available bronchus blocker (EZ-blocker, AnesthetIQ, Delft, the Netherlands) to enable RLN monitoring during single lung ventilation [6]. After intubation with the Xomed tube, the Y-shaped EZ-blocker is placed under bronchoscopic visualization through the tube on the carina. If desired, the left or right main bronchus could be blocked with the two cuffs alternately. The advantages of this method are as follows: (1) it facilitates endotracheal intubation, especially during rapid sequence induction, (2) it allows the possibility of repositioning the endotracheal tube in case of lacking EMG signal without interfering with single lung ventilation, and J. Schmidt A. Irouschek S. Heinrich T. Birkholz (&) Department of Anesthesiology, University of ErlangenNuremberg, Krankenhausstr. 12, 91054 Erlangen, Germany e-mail: t.birkholz@gmx.de

Laryngeal morbidity after intubation with or without neuromuscular block in thyroid surgery using recurrent laryngeal nerve monitoring

OBJECTIVE The avoidance of neuromuscular blocking agents (NMBA) for endotracheal intubation is associated with a higher incidence of laryngeal discomfort and lesions, but could impair effectiveness of intra operative recurrent laryngeal nerve monitoring (IONM). METHODS In a retrospective quality assessment study over a period of 30 months, a collective that had been intubated without NMBA was compared with a group, which had received NMBA. Endolaryngeal EMG was accomplished with a MagStim(®)-EMG-electrode. RESULTS Out of the 127 patients with 224 nerves at risk (NAR; NMBA 102 NAR, no NMBA 122 NAR), more than 90% received a total intravenous anaesthesia with propofol, and 88% had remifentanil. Laryngeal side effects and damage scores did not differ significantly. CONCLUSIONS In this special setting of IONM and thyroid surgery, avoidance of NMBA for endotracheal intubation seems not to increase the incidence of laryngeal side effects and lesions. If endotracheal intubation without NMBA is required, the authors suggest a standardized approach using induction agents as propofol and remifentanil.

Comparison of two electromyographical endotracheal tube systems for intraoperative recurrent laryngeal nerve monitoring: reliability and side effects.

BackgroundRecurrent laryngeal nerve (RLN) monitoring systems should be reliable and safe. Monitoring via electromyographical systems on an endotracheal tube (ETT) is widely spread. The MagStim™ system consists of an adhesive electrode to be fixed on an endotracheal tube. The Xomed™ endotracheal tube provides integrated electrodes. Reliability and side effects had never been compared. As both systems have very different morphological properties, we hypothesized that there might be differences in reliability and the incidence of side effects.MethodsIn a retrospective quality management analysis of 118 patients (MagStim™ electrode, 57 patients; Xomed™ ETT, 61 patients), we compared laryngeal side effects according to the Chilla score and detection rate of the RLN.ResultsBoth systems had comparable detection rates of the RLN above 95%. Both electrode systems seemed to have similar reliability. Difficulties to detect the nerve were observed in seven patients (four with MagStim, three with Xomed). In the group with the Xomed™ ETT, significantly less mild laryngeal side effects were observed.ConclusionBoth MagStim™ and Xomed™ ETT were reliable in detecting the RLN. The Xomed™ ETT, however, might cause milder laryngeal side effects compared with the MagStim™ electrode.

Early recovery from anesthesia and extubation in an infant with very long chain acyl-CoA dehydrogenase deficiency using midazolam, mivacurium, and high dose remifentanil

1 Leeson RM, Harrison S, Ernst CC et al. Dyloject, a novel injectable diclofenac formulation, offers greater safety and efficacy than voltarol for postoperative dental pain. Reg Anesth Pain med 2007; 32(4): 303–310. 2 Colucci RD, Wright C IV, Mermelstein FH et al. Dyloject, a novel diclofenac solubilised with cyclodextrin: reduced incidence of thrombophlebitis compared to injectable diclofenac solubilised with polyethylene glycol and benzyl alcohol. Acute pain 2009; 11(1): 15–21. 3 BNF (British National Formulary) for children. 2008; Section 10.1.1, 590. 4 Van Der Marel CD, Anderson BJ, Rømsing J et al. Diclofenac and metabolite pharmacokinetics in children. Pediatr Anesth 2004; 14: 443–451.

Alternative anesthetic management of a child with spastic quadriplegia due to metachromatic leukodystrophy using total intravenous anesthesia

SIR—In patients with metachromatic leukodystrophy, distinct clinical problems are affecting the way to give anesthesia to those patients (1–3). With great respect we read the articles by Mattioli et al. and Hernandez-Palazon et al. in Pediatric Anesthesia (1,2) in preparation for the anesthetic management of a 13-year-old boy (20 kg, 135 cm) with seizures, severe cognitive impairment, the clinical picture of tetraspasm and marked scoliosis due to metachromatic leukodystrophy. The child was admitted for replacement of the dislocated percutaneous endoscopic gastrostomy (PEG) and resection of dermal fistulas induced by the PEG. In our patient, at the age of 3 years, a PEG was established and replaced six month before. Shortly after that, melena due to severe ulcerative gastroesophageal reflux with gastroesophageal hernia occurred. Recurrent aspiration pneumonias had occurred. Procedural sedations had often lead to postoperative hypothermia and pronounced shivering. To maintain effectiveness of the daily medication, anticonvulsive and proton pump inhibitor-therapy was continuedonthedayofoperation.Nosedationwasnecessary inthe somnolent patient. The pediatric operation suite was heated to 28 C air temperature. Standard monitoring was applied (Siemens SC 9000 XL; Siemens AG, Erlangen, Germany). We had to face typical main features of the disease, an immobile and spastic patient, who has a high risk of aspiration. Rapid sequence induction seemed to be the equate answer in our case. With the upper part of the body in a 30 upright position and after 3 mins of preoxygenation, a continuous infusion of remifentanil (0.5 lgÆkgÆ min) was started. After additional 2 mins, 175 mg thiopentone were administered. Succinylcholine was contraindicated due to the risk of hyperkaliaemia and rhabdomyolysis. With the loss of conscience, 0.9 mgÆkg Rocuronium were injected intravenously (4). 75 sec later, the patient was intubated endotracheally (5.5 mM, Endosoft ; Mallinckrodt, Athlone, Ireland) and ventilated pressure controlled (Kion, Siemens AG, Erlangen, Germany, FiO2 0.4, end tidal CO2 of 36–38 mmHg). Anesthesia was maintained as total intravenous anesthesia (TIVA) with propofol 6 mgÆkgÆh and remifentanil 0.5–0.25 lgÆ kgÆmin adapted to the hemodynamic response of the patient. The tetraspastic state of the patient excluded a facile use of acceleromyography at the adductor pollicis muscle. Therefore, the right forehead branch of the facial nerve was stimulated and the contraction sound of the corrugator supercilii muscle (CSM) was recorded by phonomyography (5). Propofol and remifentanil for TIVA minimizes residual hypnotic or opioid action. They should result in a very short recovery from anesthesia and an awakening free of excitation. With the impaired pharyngeal control, propofol’s antiemetic properties might be beneficial. Additionally, with remifentanil, an intra-operative fast response to surgical stimuli is rendered possible. The use of remifentanil requires a concept for preemptive analgesia. The patient received 300 mg of paracetamol 30 mins before the last suture and local analgesia with 8 ml of 0.375% ropivacain. In this patient, peridural anesthesia as it was described before (1) would have been complicated by the marked scoliosis. The surgical field was easy accessible for local anesthesia. Due to impaired temperature homeostasis, two active warming blanket systems maintained normal body temperature (below and over the patients’ body, esophageal temperature probe). Temperature management is a well known problem in patients with leukodystrophies and should be considered carefully in every single case. The surgical procedure took a total of 95 mins and showed no abnormalities. With the last suture, phonomyographic recordings had showed a train-of-four-ratio of >0.95 at the corrugator supercilii for >30 mins; 8 mins after that, extubation was successful in the presence of swallow reflexes. The neuromuscular recovery was within a normal range, as described before (3). While there is an exclusive correlation in the recovery of pharyngeal muscles and the adductor pollicis muscle (5), there was no perfect solution for neuromuscular monitoring in this patient. To strengthen the safety margin for the patient, a longer observation period for full recovery at the CSM and clinical signs of pharyngeal function were awaited. Postoperatively monitored on the pediatric ICU, there was sufficient pain control and stable respiratory function. The postoperative course was uneventful, and the neurological state was unchanged. Mattioli et al. described procedural sedation for brain magnetic resonance imaging with thiopentone or propofol in 18 children with metachromatic leukodystrophy (2). They reported no clinical signs of aspiration and discharged to the normal ward after 15 mins. For an anesthesia procedure on a patient with progressive state as described in our case, we would prefer a secure airway and a prolonged postoperative monitoring to detect late onset of respiratory problems as aspiration. We like to conclude that a TIVA using propofol and remifentanil, preceded by a rapid sequence induction with thiopentone and rocuronium and completed by a regimen of nonopiod-analgesic and local anesthetic infiltration, could be a safe alternative in the anesthesiological management of children with metachromatic leukodystrophy. CORRESPONDENCE 551

Green breast milk after propofol administration.

fluid-filled tissue. A homogeneous tissue model with attenuation coefficient of 0.3 decibels/cm megahertz throughout the beam path is commonly used when estimating exposure levels. The model is conservative in that it overestimates the in situ acoustic exposure when the path between the transducer and site of interest is composed entirely of soft tissue. When the path contains significant amounts of fluid, as in many firstand second-trimester pregnancies scanned transabdominally, this mode may underestimate the in situ acoustic exposure. The amount of underestimate depends on each specific situation. So as, we gaze appreciatively at the “donut” surrounding the nerves, what is that increased exposure time doing on a cellular basis? We do not know. But the injection of fluid may alter tissue acoustic attenuation factors to more closely resemble in vitro conditions favorable to inertial cavitation, the effects of which increase with exposure time. The same product literature notes that we should structure the performance of studies to minimize exposure times. In addition, bubbles represent an acoustical interface where energy release occurs. These bubbles may be iatrogenic or produced in the rarefaction phase of the acoustical wave. Are practitioners assiduous about avoiding bubbles in the injected local anesthetic? What happens to a room-temperature, nondegassed liquid injected into a body-temperature subject? What of bubbles in a local anesthetic to which sodium bicarbonate has been added? Data show that bubbles decrease the cavitation threshold from 1.9-2.4 MPa to less than 0.65 MPa (filtered water data). Product information for the SonoSite L38 /10-5 probe (SonoSite, Inc., Bothell, WA) shows an acoustical pressure of 2.345 MPa in the PW/Doppler mode or 2.89 MPa in the CPD mode. We have no information on the effect(s) of these potential sources of ultrasound cytotoxicity/neurotoxicity enhancement. Ongoing studies in which thousands of ultrasound-assisted regional anesthetics have been performed without notable adverse effects are reassuring. However, we remember other reports wherein the remarkable safety of spinals in tens of thousands of cases were discussed, and then a complication shows up; i.e., transient neurologic symptoms. The flip side to those observations is that if effects do occur, such as those I have been discussing above, they are unusual events with high significance. Again, for those of us familiar with product development, one would want to specifically identify and mitigate just such occurrences through risk analysis. However, we have not performed or obtained that risk analysis for ultrasound-guided regional anesthesia. In lieu of an outright moratorium on ultrasound-guided regional anesthesia, we must at least take reasonable precautions until additional research results are available: Limiting local anesthetic concentration to that necessary for achieving the desired result, limiting ultrasound exposure times, eliminating bubbles in injection solutions, not carbonating local anesthetics, warming local anesthetic solutions before use (degassing), and not spending time admiring the “donut.” Until safety questions have been definitively answered, ultrasound-guided regional anesthesia deserves a continued high level of scrutiny.