1. Pro–con debate: intravenous vs inhalation induction of anesthesia in children. Pediatric Anesthesia 21: 159 - 168; 2011.
THE CASE FOR INTRAVENOUS INDUCTION Marzena Zielinska
The Department of Paediatric Anesthesiology and Intensive Care, The University of Medicine in Wroclaw, Wroclaw, Poland
THE CASE FOR INHALATION INDUCTION Helen Holtby
Department of Anaesthesia and Pain Medicine, Hospital for Sick Children, Toronto, ON, Canada
MODERATOR Andrew Wolf
Paediatric Intensive Care Unit, Bristol Royal Children’s Hospital, Bristol, UK
The choice of inhalational or intravenous induction in children, aside from a few specific scenarios, is largely determined by the preference and experience of the anaesthetist. This debate presents the advantages and disadvantages of each technique. The debate for inhalational technique also provides some useful hints on how to achieve a smooth inhalational induction. This topic lends itself to a debate because there is no right or wrong answer. Every paediatric anaesthetists needs to develop a technique that works for them and is appropriate for the particular anaesthetising environment. Proficiency in both techniques allows induction to be tailored to the individual child and to the clinical situation.
2. The difficult pediatric airway – a review of new devices for indirect laryngoscopy in children younger than two years of age. Holm-Knudsen R Pediatric Anesthesia 21: 98 - 103; 2011.
This review article examines four devices that can be used for indirect laryngoscopy and intubation in children under the age of 2: the AIRTRAQ optical laryngoscope, the GlideScope videolaryngoscope, the Storz DCI video laryngoscopes and the Truview PCD Infant. The authors have found that a good view of the glottic structures is achievable with all the devices but due to the small size of the mouth, advancing the ETT anteriorly was difficult. The AIRTRAQ has a channel to allow the tube to be directed towards the glottic opening. The other devices require the use of a stylet to direct the ETT anteriorly. In both situations there is the potential for significant trauma to the sensitive infant airway.
Take Home Message
The management of the difficult airway in paediatrics presents specific challenges that are not seen in the adult difficult airway. Fortunately the un-anticipated difficult airway is not common in infants and small children. Knowledge of syndromes that are associated with a difficult airway and a thorough clinical examination will identify most difficult intubations pre-operatively. The two main challenges are the requirement for general anaesthesia and the small size of some patients. The videolaryngoscope has been used to facilitate the management of difficult intubations in adults. Purpose designed paediatric videolaryngoscopes are now available and have been used in children younger than 2. It remains to be seen which device performs best in the truly difficult airway (usually anterior larynx) in an infant or small child.
3. A Clinical Evaluation of the Intubating Laryngeal Airway as a Conduit for Tracheal Intubation in Children
Jagannathan N, Kozlowski RJ, Sohn LE, et al. Anesthesia and Analgesia, 112 (1) 176 - 182. 2011
This prospective observational study examines the use of the air-Q Intubating Laryngeal Airway (ILA) in children. The air-Q is available in paediatric sizes and is specifically designed to facilitate intubation with cuffed tracheal tubes. The airway tube is wider, curved and more rigid. The connector can also be removed allowing for an increased internal diameter. The ILA is shortened to make it easier to remove. The ventilating orifice is elevated and is designed to prevent occlusion by the epiglottis. The sizing of the air-Q was different to the sizing of LMA we are more familiar with. Children between 7kg and 17 kg received a size 1.5 ILA and children between 17kg and 30 kg received a size 2. (Our LMAs: size 1.5 5kg-10kg, size 2 10 kg - 20 kg, size 2.5 20kg - 30 kg)
This study looked at children with normal airways who were scheduled for surgery requiring intubation. The study looked at ease of placement of the ILA, ease of fibreoptic placement, quality of the view obtained, ease of intubation and ease of removal of the ILA over the tracheal tube. The feasibility of blind tracheal intubation using the ILA was assessed by grading the quality of airway alignment with the ILA ventilating orifice. Larger patients tended to have a better fibreoptic view and therefore better epiglottic isolation. Smaller patients had higher rates of epiglottic down-folding despite adequate ventilation compared with larger patients. The authors propose that the combination of the larger floppy epiglottis in small children and the use of muscle relaxation may have made the epiglottis more likely to be pushed down by the tip of the ILA. Because of the higher incidence of epiglottic down folding, the authors recommend the use of a fibreoptic bronchoscope to assist tracheal intubation with this device.
Take Home Message
There are preformed laryngeal masks available for use in paediatrics that can be used as conduits for fibreoptic bronchoscopy. They are not purpose designed to facilitate blind intubation. The advantage of the intubating laryngeal mask in adult practice is the fact that it facilitates blind intubation. If a fibreoptic scope is recommended to facilitate intubation with the ILA, then the advantage of this device may be largely lost. In addition, it may in fact increase the difficulty of the procedure. It would be interesting to compare the results of the ILA using a fibreoptic scope to facilitate placement of the ETT versus the use of a fibreoptic bronchoscope on its own. If the ILA improves, speed, efficacy and safety, then it may have a role in paediatric difficult intubations.
4. Caudal block with 3 mg/Kg Bupivacaine for intra- abdominal surgery in pediatric patients: a randomized study. Loetwiriyakula W, Asampinwata T, Rujirojindakula P et al. Asian Biomedicine: 5 (1) 93-99; 2011.
This randomized double blinded trial examines the use of 3mg/kg of bupivacaine for caudal block in paediatric patients undergoing intra-abdominal surgery. Children between 6 months and 7 years were randomized to receive either 1.2 ml / kg of 0.25 % bupivacaine (grp A) or 1.5 ml / kg of 0.2 % bupivacaine (grp B) both with 50 mcg / kg of morphine. The study then assessed for effectiveness of intra-operative anesthesia, post operative analgesia and complications. Greater than 60 % of patients in both groups required rescue analgesia and 49 % in group A and 57 % in group B required muscle relaxation. They found that the two regimes provided equivalent intra-operative analgesia and surgical relaxation with the high volume low concentration preparation providing superior analgesia of longer duration.
Take Home Message
Infants and children may be at increased risk of local anaesthetic toxicity because of practical, pharmacokinetic and pharmacodynamic factors. Infants may have an increased unbound fraction of systemic local anaesthetic due to lower concentrations of plasma proteins. Metabolism and elimination of local anaesthetic can also be delayed. In children regional anaesthesia is done under general anaesthesia. The proceduralist is therefore reliant on haemodynamic and ventilatory changes as a marker of inadvertent intravascular or intrathecal injection. This is only possible if adrenaline is used in a test dose and appropriate monitoring with ECG and blood pressure is in place. In order to achieve surgical anaesthesia and sufficient muscle relaxation, this study uses a dose of 3 mg / kg of bupivacaine as a single shot. Whilst there have been studies that show acceptable plasma concentrations of bupivacaine after 3 mg / kg administered, this exceeds the recommended safe dose. In addition, given that large doses of local anaesthetic are being given as a bolus, it would seem that levobupivacaine and ropivacaine would be a much safer choice.
The authors conclude that the two preparations provide comparable anaesthesia and relaxation. However, it does not appear from this study that either of these two preparations provide sufficient anaesthesia and surgical relaxation to allow intra-abominal surgery. This raises the question of whether the benefits outweigh the risks. If post operative analgesia is the only benefit, this can be achieved safely with a single shot caudal of high volume, and low concentration (with or without adjuvants) given at the end of the procedure or by the use of an epidural. This study does reinforce the finding that using a high volume low concentration local anaesthetic provides a greater duration of analgesia than using a low volume and high concentration of the same dose of local anaesthetic
5. Management of hypertrophic pylorus stenosis with ultrasound guided single shot epidural anaesthesia – a retrospective analysis of 20 cases. Willschke H, Machata A, Rebhandl W, et al. Pediatric Anesthesia 21: 110 - 115; 2011.
In this study, infants received a rectal midazolam pre med. They were then sedated with nalbuphine and propofol and underwent ultra-sound guided single shot epidural between T10 and T11. The epidural was performed with 0.75 ml/kg of 0.475 % ropivacaine. Gentle assisted ventilation with inspiratory pressure less than 10 mmHg was used in case of hypoventilation. Anaesthetists were prepared for emergency rapid sequence induction in case of respiratory failure or insufficient blockade. The first 20 infants were retrospectively analyzed. Anaesthesia by this technique was successful in all cases with no infants requiring intubation for respiratory failure or failed block. One infant required ventilatory support via face mask.
Take Home Message
Pyloromyotomy is a straight forward procedure. It is usually carried out in healthy infants who, once resuscitated, tolerate a brief general anaesthetic well. In addition, infants are often past the post conceptual age at which they are at risk of apnoea after general anaesthesia. These infants are at risk of prolonged sedation following opioid use. However, opioids can be avoided in an open technique using infiltration of local anaesthetic. Infants with pyloric stenosis are at risk of aspiration due to inability of the stomach to empty. General anaesthesia with rapid sequence induction and intubation significantly reduces the risk of aspiration.
Pyloromyotomy requires a block between T4 and T6. Caudal block does not reliable reach these levels to provide sufficient density and duration of block. The authors state that spinal block may cause uncontrolled high block and subsequent respiratory insufficiency. The approach in this study used 3.6 mg / kg of ropivacaine injected as a bolus in to the T10/T11 epidural space. It would seem to me that the use of large volumes of local anaesthetic in a thoracic epidural on a background of sedation creates a real risk of hypoventilation requiring ventilatory support. This would further increase the risk of aspiration. In fact one out of the twenty infants in this study required assisted positive pressure ventilation via face mask for a period of desaturation. In addition, 3.6 mg / kg exceeds the recommended safe dose of local anaesthetic.
The authors state that they have extensive experience with ultrasound guided thoracic epidural anaesthesia in infants. I would not consider this a straight forward procedure for even experienced paediatric anaesthetists. I would question the overall utility of this technique for this particular procedure. Research on the neurodevelopmental effects of general anaesthesia versus regional anaesthesia in infancy may shed further light on this issue.
Disclaimer
Reasonable attempts are made to include articles representative of recent publications, but no attempt is made to include every important article. The commentaries and take-home messages are only some of many possible opinions/interpretations from the anaesthesia literature.
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