Stephan Malherbe

Total intravenous anesthesia and spontaneous respiration for airway endoscopy in children – a prospective evaluation

Introduction:  Inhalational anesthesia with spontaneous respiration is traditionally used to facilitate airway endoscopy in children. The potential difficulties in maintaining adequate depth of anesthesia using inhalational anesthesia and the anesthetic pollution of the surgical environment are significant disadvantages of this technique. We report our institutional experience using total intravenous anesthesia (TIVA) and spontaneous respiration.

Relationship between age and spontaneous ventilation during intravenous anesthesia in children

Background:  Maintaining spontaneous ventilation in children, using total intravenous anesthesia (TIVA), is often desirable, particularly for airway endoscopy. The aim of this study was to evaluate the effect of age on the dose of remifentanil tolerated during spontaneous ventilation under anesthesia maintained with infusions of propofol and remifentanil and to provide guidelines for the administration of remifentanil and propofol to maintain spontaneous ventilation in children.

The effect of age on the dose of remifentanil for tracheal intubation in infants and children.

Introduction:  This study aimed to determine the age‐specific bolus dose of remifentanil (ED50) to facilitate tracheal intubation without the use of neuromuscular blocking agents.

Intravenous nalbuphine 50 µg·kg -1 is ineffective for opioid-induced pruritus in pediatrics

PurposeThis investigation evaluated the efficacy of nalbuphine in treating postoperative opioid-induced pruritus (Pr) in pediatric patients.MethodsAfter Ethics Board approval, the dual site, tertiary care teaching centre study recruited 212 subjects, age ≥ seven years, who received opioid analgesia postoperatively. A modified, self-report colour analogue scale (CAS) scored pruritus intensity (PrI). Subjects who reported PrI score ≥ 5/10 were randomized to treatment with nalbuphine 50 µg·kg-1 iv (max 5 mg) or saline placebo. A pruritus intensity difference (PrID) ≥ 50% was considered a positive outcome.ResultsOf 260 subjects approached, 212 consented and 184 received opioids. Median age was 13 yr (range 7-19) and median weight was 51 kg (range 19.6-134.8 kg). Pruritus intensity ≥ 5/10 occurred in 37 (20.1%) subjects. Intravenous morphine [patient-controlled analgesia (PCA)/continuous infusion] was associated with Pr in 68% of subjects over a wide dose range (9.4-63.2 µg·kg-1·hr-1). Pruritis occurred in 36% of patients in the PCA group compared to continuous opioid infusion (27%) and epidural administration (27%). Pruritus intensity difference ≥ 50% was achieved in 55.6% of nalbuphine and 57.9% of saline-treated subjects.ConclusionThis preliminary report suggests that nalbuphine 50 µg·kg-1 iv is not effective in treating postoperative opioidinduced pruritus in pediatric patients. The modified CAS score and PrID warrant further investigation.ObjectifÉvaluer l’efficacité de la nalbuphine contre le prurit (Pr) postopératoire induit par les opioïdes chez des patients pédiatriques.MéthodeNous avons recruté 212 sujets de ≥ sept ans qui ont reçu une analgésie opioïde postopératoire. Une échelle analogique de couleur (EAC) modifiée pour l’auto-évaluation a mesuré les scores d’intensité du prurit (IPr). Répartis au hasard, les sujets dont les scores d’IPr étaient ≥ 5/10 ont reçu de la nalbuphine à 50 µg·kg-1 iv (5 mg maximal) ou un placebo salin. Une différence d’intensité de prurit (DIPr) ≥50% était considérée positive.RésultatsDes 260 sujets rencontrés, 212 ont participé à l’étude et 184 ont reçu des opioïdes. L’âge moyen a été de 13 ans (7-19) et le poids moyen de 51 kg (19,6-134,8 kg). Un prurit ≥ 5/10 a été noté chez 37 (20,1 %) des sujets. De la morphine intraveineuse [en analgésie auto-contrôlée (AAC) ou en perfusion continue] a été associée à du Pr chez 68 % des sujets pour un grand éventail de doses (9,4-63,2 µg·kg-1·h-1). Le prurit s’est manifesté chez 36 % des patients avec l’AAC comparée à la perfusion d’opioïde continue (27 %) et à l’administration péridurale (27 %). Une différence d’intensité du prurit ≥ 50 % a été atteinte chez 55,6 % des sujets qui recevaient la nalbuphine et 57,9 % de ceux qui avaient le placebo.ConclusionLa nalbuphine iv à 50 µg·kg-1 n’est pas efficace pour traiter le prurit postopératoire induit par les opioïdes chez des patients pédiatriques. Le score modifié à l’EAC et la DIPr devront être étudiés plus à fond.

Usability and performance characteristics of the pediatric air-Q® intubating laryngeal airway

PurposeThe air-Q® intubating laryngeal airway (ILA) is a supraglottic device (SGD) designed specifically to function as both a primary airway and a bridging device and conduit for fibreoptic intubation in difficult airway scenarios. This observational study evaluated the usability and performance characteristics of pediatric air-Q ILA sizes 1.0, 1.5, 2.0, and 2.5 when used as a primary airway.MethodsOne hundred ten children, American Society of Anesthesiologists physical status I-III and undergoing elective surgery, received a weight-appropriate air-Q ILA following induction of anesthesia. The evaluation criteria included ease of insertion, quality of ventilation, presence of gastric insufflation, oropharyngeal leak pressures (OLPs) and maximum tidal volumes (VT max) in five different head positions, and fibreoptic view of the glottis.ResultsFor sizes 1.0, 1.5, 2.0, and 2.5, the median [P25,P75] neutral OLPs (cm H2O) were 23.0 [20.0,30.0], 16.5 [15.0,20.8], 14.0 [10.0,17.8], and 14.0 [11.3,16.8], respectively. The median [P25,P75] neutral VT max values (mL·kg−1) were 17.4 [14.3,19.7], 20.3 [16.8,25.5], 17.8 [14.5,22.1], and 14.0 [11.6,16.0], respectively. Median [P25,P75] ease of insertion scores (0-10; 0 = easiest ever, 10 = most difficult ever) were 1 [1,2], 2 [2,3], 2 [1,2.8], and 2 [2,3] respectively. Ventilation was adequate in 108/110 cases, and a fibreoptic view of the vocal cords was obtained in 102/110 cases.ConclusionsThe air-Q ILA functions acceptably as a primary SGD in infants and children. The OLPs are lower than published values for the ProSeal laryngeal mask airway (LMA ProSeal™), the current pediatric SGD of choice, but adequate tidal volumes are readily achievable. The fibreoptic views of the glottis portend well for fibreoptic intubation through the device. (This trial was registered at clinicaltrials.gov number, NCT00885911).RésuméObjectifLe masque laryngé d’intubation air-Q® est un dispositif supraglottique (DSG) conçu spécialement pour fonctionner aussi bien seul comme instrument de gestion des voies aériennes que comme pont et guide d’intubation fibroscopique en cas de voies aériennes difficiles. Cette étude observationnelle a évalué les caractéristiques de convivialité et de performance du masque laryngé air-Q de tailles 1,0, 1,5, 2,0 et 2,5 utilisé seul.MéthodeAprès l’induction de l’anesthésie, on a inséré un masque laryngé d’intubation air-Q adapté au poids chez 110 enfants de statut physique I-III selon la classification de l’American Society of Anesthesiologists devant subir une chirurgie non urgente. Les critères d’évaluation comprenaient la facilité d’insertion, la qualité de la ventilation, la présence d’insufflation gastrique, les pressions de fuite oropharyngée (OLP) et les volumes courants maximaux (VT max) dans cinq positions différentes de la tête, ainsi que la vue fibroscopique de la glotte.RésultatsPour les tailles 1,0, 1,5, 2,0, et 2,5, les OLP neutres médianes [P25,P75] (cm H2O) étaient de 23,0 [20,0,30,0], 16,5 [15,0,20,8], 14,0 [10,0,17,8], et 14,0 [11,3,16,8], respectivement. Les valeurs VT maximales neutres médianes [P25,P75] (mL·kg−1) étaient de 17,4 [14,3,19,7], 20,3 [16,8,25,7], 17,8 [14,5,22,1], et 14,0 [11,6,16,0], respectivement. Les scores médians [P25,P75] de facilité d’insertion (0-10; 0 = le plus facile, 10 = le plus difficile) étaient de 1 [1,2], 2 [2,3], 2 [1,2.8], et 2 [2,3] respectivement. La ventilation était adéquate dans 108/110 cas, et une vue fibroscopique des cordes vocales a été obtenue dans 102/110 cas.ConclusionLe fonctionnement du masque laryngé d’intubation air-Q est acceptable utilisé seul chez les nourrissons et les enfants. Les OLP sont plus basses que les valeurs publiées pour le masque laryngé ProSeal (LMA ProSeal™), le DSG actuellement privilégié en pédiatrie, mais on peut facilement atteindre des volumes courants adéquats. Les vues fibroscopiques de la glotte laissent présager une bonne intubation fibroscopique via le dispositif. (Cette étude a été enregistrée au numéro ClinicalTrials.gov NCT00885911).

Total Intravenous Anesthesia and Spontaneous Ventilation for Foreign Body Removal in Children: How Much Drug?

To the Editor In a recent study, Chen et al. compared the risk factors for hypoxia when using 4 different anesthetic techniques for removal of foreign bodies in children younger than 5 years old. The fact that the authors found that patients breathing spontaneously and receiving total IV anesthesia (TIVA) had more movement, breath holding, and a lower success rate with foreign body removal is not surprising and is, in our opinion, attributable to the too small doses of propofol and remifentanil administered. Subjects received a bolus of propofol (3–5 mg/kg) and remifentanil (1 g/kg) followed by infusions of propofol (100–150 g/kg/min) and remifentanil (0.1 g/kg/min). Simulations (TIVATrainer ) of the doses described would have produced near steady-state (15 minutes) effectsite concentration of propofol of 2.9 g/mL based on the Paedfusor model and remifentanil of 0.55 g/mL based on the Rigby-Jones model. These concentrations would be considered low even in adults. Moreover, most children will tolerate larger does of remifentanil (and propofol) while maintaining spontaneous respiration. Our institutional practice is to use TIVA with remifentanil and propofol for most of our patients undergoing airway endoscopy. In a prospective study, we found the mean remifentanil dose to be 0.21 (SD 0.31) g/kg/min and propofol infusion rate to be 368 (SD 103) g/kg/min. The wide interindividual variability dictates that drugs are titrated to clinical effect within a wide dose range. The greater incidence of laryngospasm in the TIVA group might also reflect the too small dose of the drugs. Reflex laryngeal responses occur less frequently and of shorter duration with propofol anesthesia compared with sevoflurane, and propofol is often used for treatment of mild laryngospasm. We conclude that the increased complication rate seen in the group using TIVA and spontaneous ventilation may have been due to the low doses used and not a result of the technique selected.

Cranial conjoined twins: Surgical and anesthetic challenges for a routine procedure: Adenoidectomy and examination of ears

Craniopagus conjoined twins have long been the subject of interest because of the rarity and peculiarity of their juxtaposition. We present the surgical, airway and anesthetic challenges in craniopagus conjoined twins, in which one of the twins underwent adenoidectomy for obstructive sleep breathing disorder. The surgical procedure required a special setting from an anesthetic perspective whereby both children needed anesthesia due to the complex physiology of their brains and cardiovascular systems. As well, we took the opportunity to do bilateral ear examinations of both twins.

The effect of age on spontaneous breathing using propofol and remifentanil in children

Introduction:  Maintaining spontaneous ventilation in children, using total intravenous anaesthesia, is often desirable, particularly for invasive airway procedures such as diagnostic airway endoscopy and removal of inhaled foreign bodies. The maximum tolerated infusion rate of remifentanil during spontaneous ventilation in combination with a volatile anaesthetic (sevoflurane) has been studied in children (1), where a large dose variation was found. This also seemed to vary widely compared to adults, who tolerated significantly less (2). Contrary to expectations however, younger children appeared to be more resistant to the respiratory depressant effect of the opioid. The aim of this study was therefore to determine what the effect of age is on spontaneous respiration when anaesthesia is maintained using infusions of propofol and remifentanil.

Greenhouse gases: the choice of volatile anesthetic does matter

To the Editor, Global warming, considered one of the greatest health threats of the 21st century, is linked to greenhouse gas emissions. The major greenhouse gases – carbon dioxide (CO2), methane, nitrous oxide, and chlorofluorocarbons – have been well studied and regulated. The contributions from the healthcare industry, however, have been largely ignored or excused under the guise of medical necessity. Nevertheless, a considerable portion of hospital waste is generated in the operating room, and anesthesiologists are in an ideal position to take a leadership role to minimize the hospital-related negative environmental impact. Volatile anesthetic drugs are halogenated fluorocarbons and potent greenhouse gases, as measured by their global warming potential (GWP), which is a relative measure of how much heat a given gas traps in the atmosphere compared with a similar mass of CO2. Because most volatile agents remain in the atmosphere for one to 15 years, the GWP is often expressed over a 20-year time horizon (GWP20). This value represents the amount of heat trapped by the gas over a 20-year period, compared with a similar mass of CO2. For example, the GWP20 values for desflurane, isoflurane, and sevoflurane are 6810, 1800, and 440, respectively. The carbon dioxide equivalent (CDE20) is the product of the GWP20 and the quantity of the gas. Colloquially referred to as the ‘‘carbon footprint,’’ it represents the amount of CO2 that would have the same global warming potential over a 20-year period. Concerted efforts by the University of British Columbia’s (UBC) Department of Anesthesiology have increased awareness about the deleterious environmental effects of volatile anesthetics. This effort resulted in the purchase of modern, low-flow anesthetic machines that closely regulate expired end-tidal anesthetic gas concentrations. It also contributed to a change in the Department’s preference to use volatile anesthetics with the lowest GWP20 values. To quantify these changes, we undertook a quality assurance project (Research Ethics Board approval not required as per Article 2.5, TCPS2) to assess the volume of volatile anesthetics used during the years 2012-2016 according to data from seven UBC-affiliated hospital pharmacies. In 2012, these sites combined used 1,318 L of desflurane and 385 L of sevoflurane. Using published values, this resulted in a calculated CDE20 for desflurane and sevoflurane of 13,190,098 kg and 257,655 kg, respectively, for a total of 13.4 million kg of CO2 equivalence (Figure). Subsequently, the use of desflurane has steadily decreased whereas sevoflurane use increased, such that in 2016, desflurane use was 401 L and sevoflurane use was 772 L. Thus, the calculated CDE20 of 4,009,886 kg for desflurane and 515,979 kg for sevoflurane combined for a total carbon footprint of 4.5 million kg of CO2 equivalence. Of note, the total volume of volatile anesthetics used decreased from 1,703 L to 1,173 L R. Alexander, MD, BSc (&) A. Poznikoff, BSc S. Malherbe, MBChB, MMed, FRCPC Department of Anesthesiology, Pharmacology & Therapeutics, University of British Columbia, Vancouver, BC, Canada e-mail: richard.f.alexander@gmail.com

Placebo equal to nalbuphine for pruritus in pediatrics

METHODS After approval by the University Research Ethics Boards, the dual centre study planned to recruit 268 subjects, age ≥ 7, receiving continuous opioid analgesia post-operatively who understood the self-report Colour Analogue Scale (CAS) to score pruritus intensity (PrI). Sample size was estimated to demonstrate a 25% improvement compared to placebo (α=0.05 and 1-β=0.8). Subjects who reported PrI score ≥ 5/10 were randomized to treatment with nalbuphine 50 mcg/kg IV (max 5 mg) or saline placebo. PrI, analgesia (VAS), sedation (5 point score), and side effects of headache, vomiting, and dizziness (yes/no) were recorded at 30 and 60 min. A Pruritus Intensity Difference (PrID) of ≥ 50% was considered a positive outcome. Subjects with PrI score ≥ 5/10 at 60 min. received nalbuphine 50 mcg/kg IV (max 5 mg).