Mark Ansermino

Nonopioid additives to local anaesthetics for caudal blockade in children: a systematic review

Background:  Caudal epidural injection with local anaesthetics is a popular regional technique used in infants and children. A disadvantage of caudal blockade is the relatively short duration of postoperative analgesia. Opioids have traditionally been added to increase the duration of analgesia but have been associated with unacceptable side‐effects. A number of nonopioid additives have been suggested to increase the duration of analgesia.

Continuous noninvasive blood pressure measurement by pulse transit time

Blood pressure measurement is performed either invasively by an intra arterial catheter or noninvasively by cuff sphygmomanometry. The invasive method is continuous and accurate but has increased risk; the cuff is safe but less reliable and infrequent. A reliable continuous noninvasive blood pressure measurement is highly desirable. While the possibility of using pulse transit time to monitor blood pressure has previously been investigated, most studies were limited to calculating the correlation of the pulse transit time and blood pressure under rather static conditions. The relationship between the pulse transit time and blood pressure is yet to be clearly identified. This paper focuses on the modeling between the two values and presents results on cases where dramatic variation in blood pressure of the patient was induced by drug administration or surgical stimulation.

The frequency of apneas in premature infants after inguinal hernia repair: do they need overnight monitoring in the intensive care unit?

BACKGROUND Postoperative apneas are reported in up to 49% of premature infants undergoing anesthesia for inguinal hernia repair. Our current practice is to monitor all of these babies in the intensive care unit (ICU) overnight after surgery. In addition to the considerable expense to the health care system, these cases are cancelled if no ICU bed is available. METHODS A retrospective chart review of all premature infants undergoing inguinal hernia repairs over the past 5 years was undertaken. All postoperative apneas were identified. Potential risk factors were evaluated. RESULTS Five (4.7%) of 126 premature infants had apneas after inguinal hernia repair. All of these babies had a previous history of apneas. They also had lower weights both at birth (1.08 vs 1.73 kg) and at the time of surgery (3.37 vs 4.4 kg) as well as lower gestational ages (29 vs 32.3 weeks). They were much more likely to have a complicated past medical history. Markers for this included intraventricular hemorrhage, patent ductus arteriosus, bronchopulmonary dysplasia, and requirement for mechanical ventilation and supplemental oxygen after birth. The use of sevoflurane was the only anesthetic factor which had significance. CONCLUSION Postoperative apnea in premature infants after inguinal hernia repair using current anesthetic techniques is much less common than previously reported. Infants with prior history of apneas are at highest risk. Other risk factors appear to include gestational age, birth weight, weight at time of surgery, and a complicated neonatal course. Selective use of postoperative ICU monitoring for high-risk patients could result in significant resource and cost savings to the health care system.

Canadian pediatric anesthesiologists prefer inhalational anesthesia to manage difficult airways: A survey

PurposeTo survey Canadian pediatric anesthesiologists to assess practice patterns in managing pediatric patients with difficult airways. Methods: Canadian pediatric anesthesiologists were invited to complete a web survey. Respondents selected their preferred anesthetic and airway management techniques in six clinical scenarios. The clinical scenarios involved airway management for cases where the difficulty was in visualizing the airway, sharing the airway and accessing a compromised airway.ResultsGeneral inhalational anesthesia with spontaneous respiration was the preferred technique for managing difficult intubation especially in infants (90%) and younger children (97%), however, iv anesthesia was chosen for the management of the shared airway in the older child (51 %) where there was little concern regarding difficulty of intubation. Most respondents would initially attempt direct laryngoscopy for the two scenarios of anticipated difficult airway (73% and 98%). The laryngeal mask airway is commonly used to guide fibreoptic endoscopy. The potential for complete airway obstruction would encourage respondents to employ a rigid bron-choscope as an alternate technique (17% and 44%). Conclusion: Inhalational anesthesia remains the preferred technique for management of the difficult pediatric airway amongst Canadian pediatric anesthesiologists. Intravenous techniques are relatively more commonly chosen in cases where there is a shared airway but little concern regarding difficulty of intubation. In cases of anticipated difficult intubation, direct laryngoscopy remains the technique of choice and fibreoptic laryngoscopy makes a good alternate technique. The use of the laryngeal mask airway was preferred to facilitate fibreoptic intubation.RésuméObjectifMener une enquête auprès des anesthésiologistes canadiens en pédiatrie pour évaluer les modèles de pratique face aux problèmes de voies aériennes.MéthodeL’enquête a été menée sur le Web. Les répondants ont sélectionné leurs techniques préférées d’anesthésie et de prise en charge des voies aériennes dans six scénarios cliniques dont des cas de visualisation difficile du larynx, de partage des voies aériennes et d’accès à des voies aériennes anormales. Résultats: L’anesthésie générale par inhalation avec respiration spontanée à été préférée pour gérer l’intubation difficile chez les bébés (90 %) et les jeunes enfants (97 %), mais l’anesthésie iv a été choisie en cas de voies aériennes partagées chez les enfants plus âgés (51 %) quand on n’avait pas à se soucier vraiment de difficulté d’intubation. La majorité des répondants essayeraient d’abord la laryngoscopie directe pour les deux scénarios de problèmes anticipés d’intubation (73 % et 98 %). Le masque laryngé sert couramment de guide dans l’endoscopie fibroscopique. La possibilité d’obstruction complète des voies aériennes inciterait les répondants à employer un bronchoscope rigide comme technique de remplacement (17 % et 44%).ConclusionL’anesthésie par inhalation demeure la technique préférée de prise en charge des problèmes de voies aériennes chez les enfants par les anesthésiologistes canadiens en pédiatrie. Les techniques intraveineuses sont choisies relativement plus souvent dans les cas de voies aériennes partagées, sans prévision d’intubation difficile. Pour une intubation difficile anticipée, la laryngoscopie directe demeure la technique de choix et la laryngoscopie fibroscopique remplace avantageusement. L’usage du masque laryngé est préféré pour faciliter l’intubation fibroscopique.

Beware the airway filter: deadspace effect in children under 2 years.

Background : Filters are increasingly used in breathing circuits as they protect the circuit from contamination and facilitate humidification of inspired gas. The use of filters, however, can augment the anatomical deadspace. This can be significant in children because they have much smaller tidal volumes.

Development and evaluation of multidimensional tactons for a wearable tactile display

We developed a novel wearable tactile display system as an alternative to the visual and audio displays routinely used by anesthesiologists to monitor patients in the operating room (OR). Visual displays and auditory alarms can be distracting or insufficient in their alarm transmission whereas a tactile display, which utilizes the sense of touch, can act as an effective conduit for alert delivery. A sophisticated alarm scheme is essential to convey the complex array of physiological information available in current monitoring systems; therefore, to report all relevant alerts to the attending anesthesiologist, it is essential that an augmenting or replacement display system be at least as effective and efficacious as conventional systems. Using multidimensional Tactons, we designed a tactile alert scheme consisting of 36 unique stimuli and evaluated the accuracy and response time in stimuli recognition using a tactile prototype worn as a belt. We observed an overall accuracy of 81% and a response time of 4.8 seconds. 4.18 bits (18.07 tokens) of messages were successfully communicated without loss of information. These results demonstrate that the novel tactile display represents an effective and potentially work-load-reducing method to convey vital information non-visually and non-aurally.

A Jehovah’s Witness child with hemophilia B and factor IX inhibitors undergoing scoliosis surgery

Purpose: To describe the successful perioperative hemostatic management of a Jehovah’s Witness patient with hemophilia B and anaphylactic inhibitors to factor IX, undergoing scoliosis surgery.Clinical features: A 14 ½-yr-old boy with severe hemophilia B who had a history of anaphylactic inhibitors to factor IX was scheduled to undergo corrective scoliosis surgery. He was initially started on epoetin alfa and iron supplementation to maximize preoperative red cell mass. Additionally, he was placed on a desensitization protocol of recombinant coagulation factor IX (rFIX) and was then treated with activated recombinant coagulation factor VII (rFVIIa) during the postoperative period. Tranexamic acid was given concomitantly. The intraoperative blood loss was approximately 350 mL. The nadir hemoglobin concentration was 111 g·L−1 on postoperative days one and two. On postoperative day 11, the patient was stable and discharged home with a hemoglobin of 138 g·L−1. He did not require blood transfusion and no adverse events were observed.Conclusions: The use of rFIX, rFVIIa, erythropoetin, iron, and tranexamic acid before, during and after scoliosis surgery may be a viable and safe option for hemophilia patients with inhibitors, who refuse blood products.RésuméObjectif: Décrire la prise en charge hémostatique péri-opératoire réussie d’un patient Témoin de Jéhovah souffrant d’hémophilie de type B et présentant des inhibiteurs anaphylactiques de forte teneur du facteur IX, lors d’une chirurgie de la scoliose.Éléments cliniques: Un garçon de 14 ans et demi souffrant d’hémophilie de type B et présentant des antécédents d’inhibiteurs anaphylactiques du facteur IX devait subir une chirurgie de correction de scoliose. On lui a d’abord administré de l’époiétine alpha et des suppléments de fer pour maximiser la masse érythrocytaire avant l’opération. De plus, il a reçu un traitement de désensibilisation à l’aide de facteur IX recombinant (rFIX), puis a été traité avec du facteur VII recombinant activé (rFVIIa) après l’opération. Il a simultanément reçu de l’acide tranexamique. Les pertes sanguines peropératoires étaient d’environ 350 mL. La concentration d’hémoglobine a atteint un minimum de 111 g·L−1 les premier et deuxième jours après l’opération. Le onzième jour postopératoire, le patient était stable et a pu recevoir son congé de l’hôpital. Son hémoglobine était alors 138 g·L−1. Il n’a pas nécessité de transfusion sanguine et il n’y a pas eu d’événements indésirables.Conclusion: L’administration de rFIX, de rFVIIa, d’érythropoiétine, de fer et d’acide tranexamique avant, pendant et après une chirurgie de correction de scoliose pourrait constituer une option viable et sécuritaire pour les patients hémophiles présentant des inhibiteurs et refusant la transfusion de produits sanguins.

Equipment limitations of a multichannel infusion pump

To the Editor, We report a case involving a propofol overdose that was associated with intravenous anesthesia delivered by an Alaris PC infusion system (Cardinal Health, San Diego, CA, USA). An infant weighing 4.5 kg underwent rigid bronchoscopy under general anesthesia. A total intravenous anesthetic was planned using remifentanil and propofol infusions for anesthetic maintenance. An Alaris PC 8015 infusion system, software version 9, equipped with two 8110 series syringe modules and one 8100 series infusion module, was used to deliver propofol, remifentanil, and intravenous fluid (Figure). The pump had not been powered down following the previous case. This step was omitted to facilitate efficient use of time and to avoid the delay inherent in the pump’s power-down and power-up sequence. During the programming of the syringe module delivering propofol, the operator scrolled through the page displaying the previous patient’s weight and thereby programmed the module to deliver propofol at 300 ug kg min (122.4 mL hr) based on the previous patient’s weight of 68 kg. This syringe module was set to pause, and the syringe module delivering remifentantil was subsequently programmed. In this case, the operator changed the patient’s weight to 4.5 kg and programmed the module based on this weight to deliver a dose of 0.2 ug kg min (5.4 mL hr). This syringe module was also set to pause. The infusion system gave no indication or warning that two attached modules were programmed with disparate weights with a more than tenfold difference between them. The two drug infusions, together with a normal saline infusion, were connected to the patient’s intravenous cannula and re-started. After approximately three minutes, the propofol dose was decreased to 200 ug kg min (81.6 mL hr) based on a weight of 68 kg in response to a decreased respiratory rate. Within four minutes, the attending anesthesiologist observed marked burst suppression on the bispectral index (BIS) monitor as well as the high infusion rate (in mL hr) on the infusion pump. The propofol infusion was stopped, at which time a total of 130 mg or 29 mg kg of propofol had been administered. Spontaneous respiration returned within 20 min and the procedure was completed successfully. The infant did not develop hypotension or bradycardia. He was awake within 45 min and made an uneventful recovery. Although operator error was the primary cause of this event because the propofol module was programmed without altering the weight of the previous patient, we believe that this case highlights a safety concern regarding the Alaris PC infusion system for intravenous anesthesia delivery. This system requires a cumbersome power-off and power-on procedure to reset the unit and clear the previous patient’s data. This limitation encourages the practice of not resetting the unit between cases during a busy surgical schedule. The system does not display the patient’s weight during normal operation, which decreases the likelihood of detecting a weight programming error. Most importantly, we are concerned that this device allows component modules to deliver drugs based on very different weights without providing any system alerts to the operator. We believe that this is an important safety N. Froese, MD (&) M. Ansermino, MD British Columbia’s Children’s Hospital, The University of British Columbia, Vancouver, BC, Canada

Designing an evidence-based mobile health decision aid for the management of hypertensive disorders of pregnancy (HDP) in low-resourced settings

Background Pre-eclampsia is one of the leading causes of maternal death and morbidity in low-resourced countries due to delays in case identification and a shortage of health workers trained to manage the disorder. The objective of the PIERS on the Move (POM) project was to provide mid-level health workers with an evidence-based and low-cost decision aid to improve diagnosis and management of pre-eclampsia, to improve outcomes.

Detrended fluctuation analysis of photoplethysmogram pulse rate intervals in sleep disordered breathing

The fluctuation of heartbeat intervals is irregular and erratic in healthy young individuals. Sleep disordered breathing (SDB) influences the fluctuation of heart rate. In this study, we investigated the effects of SDB on heart rate fluctuations by analyzing the short- and long-range correlation of photoplethysmogram pulse to pulse intervals (PPIs). We recruited 160 children referred to British Columbia Childrens Hospital for overnight polysomnography and recorded the photoplethysmogram (PPG) using the Phone Oximeter™. Detrended fluctuation analysis was applied to analyze the scaling behavior of PPIs time series in children with and without SDB. We found stronger short-range (10 to 40 pulses) and long-range (70 to 200 pulses) correlation in children with SDB. This reflects the loss of irregularity of heart rate in children with SDB.