Christer Jonmarker

Intravenous boluses of fentanyl, 1 µg kg−1, and remifentanil, 0.5 µg kg−1, give similar maximum ventilatory depression in awake volunteers

BACKGROUNDnThe relative respiratory effects of fentanyl and remifentanil, administered as i.v. bolus, have not previously been studied. We determined what remifentanil bolus dose gave the same maximum depression of ventilation as 1 µg kg(-1) of fentanyl.nnnMETHODSnTwelve healthy volunteers rebreathed in a system designed to dampen variations in end-tidal carbon dioxide tension PECO2 so that measurements would be obtained at similar levels of CO(2) stimulation. The minute ventilation was measured before (V(preinj)) and after injection (V(nadir)) of fentanyl, 1 µg kg(-1), and remifentanil, 0.25, 0.5, and 1 µg kg(-1). The remifentanil doses were plotted against V(nadir)/V(preinj) in a log-probit diagram to determine what amount gave the same maximum ventilatory depression as the fentanyl dose.nnnRESULTSnV(nadir) was [median (inter-quartile range)] 51 (38-64)% of V(preinj) after fentanyl, and 70 (61-77), 50 (46-56), and 29 (24-38)%, respectively, after remifentanil. The nadir occurred 5.0 (4.4-7.0) min after fentanyl, and 3.8 (2.7-4.6), 2.9 (2.7-3.2), and 3.0 (2.7-3.2) min after remifentanil injection. PECO2 at ventilation nadir was 6.26 (5.98-6.62) kPa after fentanyl, and 6.18 (6.12-6.50), 6.11 (5.91-6.45), and 6.11 (5.93-6.45) kPa after remifentanil 0.25, 0.5, and 1 µg kg(-1), respectively. A remifentanil dose of 0.47 (0.42-0.62) µg kg(-1) was equidepressant to 1 µg kg(-1) of fentanyl. Fifteen minutes after fentanyl injection, the median minute ventilation was 30-40% less than after injection of remifentanil, 0.25 and 0.5 µg kg(-1) (P<0.05).nnnCONCLUSIONSnFentanyl, 1 µg kg(-1), and remifentanil, 0.5 µg kg(-1), gave similar maximum ventilatory depression. The onset of and recovery from ventilatory depression were faster with remifentanil.

Are preformed endotracheal tubes appropriately designed for pediatric patients

The aim of the study was to examine different brands of preformed oral and nasal endotracheal tubes (ETT) and to assess whether the bend placement gave acceptable guidance for ETT depth positioning in children.

Absent Aortocoronary Connections in a Neonate With Pulmonary Atresia and an Intact Ventricular Septum

m t i w t o f p M g p a a a I n o v m ( m t URING FETAL DEVELOPMENT, pulmonary atresia can cause important changes in the growth and function of he right ventricle (RV). If there is no ventricular septal defect ie, if the fetus has pulmonary atresia with an intact ventricular eptum [PA-IVS]), the RV becomes severely hypertrophic and he RV cavity develops into a small, high-pressure chamber.1-3 resumably, the high RV pressure promotes maintenance and rowth of RV to distal coronary artery communications (venriculocoronary arterial connections) and development of cornary abnormalities. Sometimes an “RV-dependent coronary irculation (RVDCC)” where major portions of the myocarium are perfused directly from the RV will be present. Most nfants with RVDCC, however, will also have antegrade cornary blood supply from the aorta, and staged surgical palliaion with or without RV decompression can be accomplished ith good results.4,5 This report describes the authors experince with a neonate with absent aortocoronary connections and hus a total RVDCC.

Nares-to-carina distance in children: does a ‘modified Morgan formula’ give useful guidance during nasal intubation?

Knowledge of the normal nares‐to‐carina (NC) distance might prevent accidental bronchial intubation and be helpful when designing preformed endotracheal tubes (ETT).

Anesthesia for pheochromocytoma resection in a child with Fontan circulation

PurposeTo report the anesthetic management of a successful resection of a pheochromocytoma in a child with a completed Fontan circulation.Clinical featuresThe patient was an 11-yr-old boy with Ivemark syndrome who had undergone Fontan palliation at three years of age. Six weeks earlier, he had been diagnosed with a norepinephrine-producing pheochromocytoma, and he had been pretreated with oral propranolol and phenoxybenzamine. During surgery, intravenous administration of magnesium sulphate, esmolol, and phentolamine provided good hemodynamic control. Postoperatively, the patient tended to be hypotensive, and treatment with fluid administration resulted in prolonged intensive care.ConclusionAlthough intraoperative management was not problematic, postoperative care of this 11-yr old child with pheochromocytoma was complicated by residual sympathetic blockade.RésuméObjectifRapporter la prise en charge anesthésique d’une résection réussie d’un phéochromocytome chez un enfant avec une circulation de Fontan complétée.Éléments cliniquesLe patient était un garçon de 11 ans atteint d’un syndrome d’Ivemark ayant subi une palliation de Fontan à l’âge de trois ans. Six semaines plus tôt, un diagnostic de phéochromocytome produisant de la norépinéphrine avait été posé, et l’enfant avait été prétraité à l’aide de propranolol oral et de phénoxybenzamine. Pendant la chirurgie, l’administration intraveineuse de sulfate de magnésium, d’esmolol et de phentolamine a permis de maintenir un bon contrôle de l’hémodynamie. En période postopératoire, le patient a eu tendance à être hypotendu, et un traitement liquidien a entraîné un séjour prolongé aux soins intensifs.ConclusionBien que la prise en charge peropératoire n’ait pas été problématique, les soins postopératoires prodigués à cet enfant de 11 ans atteint d’un phéochromocytome ont été compliqués par un bloc sympathique résiduel.

Total spinal in an infant: can ‘dry taps’ occur with 20G Tuohy needles?

The loss‐of‐resistance technique was used to place a 20G epidural needle in the lumbar region in an anesthetized and paralyzed infant. There was no cerebrospinal fluid (CSF) leakage and a 24G catheter was inserted through the needle. At end of surgery, when the patient was breathing spontaneously and a bupivacaine bolus was given through the catheter, a total spinal block was identified. A bench test demonstrated that CSF leakage from a 20G needle can be delayed if CSF pressure is low and if air bubbles are present in the needle.

Airway patency matters

To the Editor, In their review of preoxygenation, Tanoubi et al. calculated that a preoxygenated adult patient has a pulmonary oxygen reserve that would last nine minutes should the patient become apneic. They base this calculation on estimates of available pulmonary oxygen reserves and oxygen consumption. Although the calculation is theoretically attractive because it illustrates the difference in oxygen reserves in non-preoxygenated and preoxygenated patients, we would argue that the calculation has little clinical relevance. What really matters under those circumstances is whether or not the upper airway is open. The principles of apneic oxygenation (well described 50 years ago) apply in a patient with an open airway. As long as oxygen is flushing over the airway, desaturation might not occur for 50 min or longer. Unfortunately, the nine-minute calculation is also misleading when the upper airway is not open, because the fact that oxygen causes resorption atelectasis is not taken into account. Functional residual capacity will decrease in a healthy adult patient by about 200 mL during the first minute after airway occlusion. Pulmonary shunting can then cause more rapid desaturation, even in patients who are well preoxygenated. Therefore, to take advantage of the principles of apneic oxygenation, it is important to maintain an open airway during induction and to retain an open airway during apnea while oxygen is dispersed over the patient’s face. Although Tanoubi et al. gave an otherwise good review of an interesting subject, we feel that clarifying these issues would have improved their article. Funding The authors have had no funding for the present work and have no association with any individuals or organization that could constitute a conflict of interest in relation to this submission.

Response to comments by Drs Elakkumanan and Thangaswamy

Murphy eye (Figure 1c, d and e). Case 3: A 6.5-year-old boy was scheduled for right tympanoplasty. After routine IV anesthesia induction, the trachea was intubated with a size 5.5 PVC cuffed tube under direct visualization of laryngoscopy. Anesthesia was maintained as above. Approximately, 40 min after initiation of surgery, ventilator alarm was triggered by a PAP of >30 cmH2O and manual ventilation was difficult. Chest auscultation revealed bilaterally diminished breath sounds. Palpation of the pilot balloon revealed the cuff overinflation, but cuff deflation could not improve ventilation. Also a lubricated F8 suction catheter could not pass fully down the tube. The tube was immediately replaced with a size 5.5 PVC uncuffed tube under laryngoscopy. Adequate lung ventilation with normal respiratory impedance was built. Inspection of the removed tube revealed that a blood clot of about 3 cm long had obstructed 80% of the lumen at the level of the cuff and part of the Murphy eye (Figure 1f and g). There are three pediatric case reports regarding the delayed ETT obstruction by blood clot (1–3). In contrast to the cases reported in the literature, three cases in our report are healthy children and their preoperative laboratory tests show no unusual findings. Also all intubations are uneventfully completed under direct visualization of laryngoscopy. The different head surgeries are involved in three children, but it is certain that no blood from the surgical site enters the pharynx. Moreover, bleeding from the supraglottic and laryngeal injuries may not be origin of the blood clot within the tub because the cuff tubes are used. Therefore, we speculate that mechanism of formation of blood clot within the tube may be bleeding from local tracheal injury by following factors. First, when the PVC tube with a rigid texture and a significant anterior natural curvature is used, the tube tip can impact anterior wall of the upper trachea during intubation. This impaction may cause the tracheal mucosal tear or abrasion. It has been shown that even if care is applied during intubation, superficial lesions to the larynx and tracheobronchial tree are unavoidable (4). Second, an overinflated cuff may result in tracheal trauma. In three cases, the PVC tubes with the high pressure–low volume cuffs are used and anesthesia is maintained with the mixed gases including N2O. As all cuffs are permeable to N2O and thus will expand during anesthesia (5). As soon as the diameter of the cuff exceeds the maximum diameter of the airway, mechanical disruption of the airway may occur. After occurrence of airway obstruction in our patients, cuff overinflation is confirmed. Third, because of head position changes during surgery, impaction of the tube tip and friction of the cuff on the upper trachea by the tube movement may cause the mucosal injury, especially when the tube with an overinflated cuff moves within the trachea. When one of above factors or their combination causes the tracheal injury concomitance with local bleeding, the supine position of children pools the blood in the dependent portion of the tube and the clot formation follows. When the clot mass within the tube becomes large enough to obstruct the most lumen, signs of airway obstruction emerge. To prevent occurrence of this severe airway complication in children, care must be taken to avoid forceful attempts to introduce the tube through the trachea, especially for when the PVC tubes with rigid texture and greater inherent anterior curvature are used. If the cuffed tubes are used, the intracuff pressure should be monitored and kept below 20 cmH2O. Other measures to minimize the tracheal damage also include the use of a satin-slip intubating stylet, prevention of tube tip malposition, and avoidance of adverse tube movement because of head position change or insecure tube stabilization. Moreover, use of the laryngeal mask airway to secure the airway during surgery may be a useful alternative to endotracheal intubation in suitable pediatric patients. F U S H A N X U E* N O N G H E† M A O P I N G L U O* X U L I A O* Y A N M I N G Z H A N G* *Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China †Department of Anesthesiology, Shou-Gang Hospital, Peking University, Beijing, China (email: fruitxue@yahoo.com.cn)