1. Evidence-based clinical update: Which local anesthetic drug for pediatric caudal block provides optimal efficacy with the fewest side effects? Dobereiner EFA, Cox RG, Ewej A, Lardner DR. Canadian Journal of Anesthesia 2010:
This evidence-based clinical update compares bupivacaine, ropivacaine and levobupivacaine for efficacy, side effects and toxicity when used in single shot paediatric caudal anaesthesia. 17 randomized controlled trials and 2 review articles were identified and assessed for quality of evidence. Onset time, intraoperative quality and duration of postoperative analgesia were compared to assess relative efficacy. Side effects were including motor block were also examined. A weakness of this review is that most of the studies compared nearly equipotent doses of the drugs in question and not equipotent doses. The authors acknowledge this limitation. It is difficult to find human evidence comparing toxicity profiles for rare complications.
Recommendations made in this Clinical Update.
2. The effect of volume of local anesthetic on the anatomic spread of caudal block in children aged 1 – 7 years. Thomas ML, Roebuck D, Yule C, Howard RF. Pediatric Anesthesia 2010; 20: 1017 – 1021.
The study aims to examine the anatomic spread of volumes of local anaesthetic that are less than 1 ml/kg. A volume of 0.5 ml/kg, 0.75 ml/kg and 1 ml/kg of caudal bupivacaine was administered depending on the type of surgery. A 22 gauge intravenous catheter was placed into the caudal space by a consultant anaesthetist and the local anaesthetic/contrast solution was injected at a constant rate by the use of an infusion pump. Omniopaque radio opaque dye was used and a single lateral x-ray taken. A radiologist blinded to the volume used reported the extent of spread as the highest whole vertebral level visualised.
The study was powered to detect a difference of two vertebral levels between incremental volumes of local anaesthetic. The study found no statistically significant difference in spread between incremental groups. There was a statistically significant difference between 0.5 ml / kg and 1 ml / kg. The authors stress that the median volume reached for 1 ml / kg volume was T12. Thus volumes of local anaesthetic less than 1 ml / kg are unlikely to reach of vertebral level higher than L2.
Take Home Message
The volume of local anaesthetic injected into the caudal space determines the spread. This study shows that small increases in volume between 0.5 to 1.0 ml/kg have a very small effect on spread. The x-rays were taken early when spread may have been continuing. This study did not look at clinical or analgesic efficacy. Quality and duration of block may be improved by incremental increases in volume even with a small increase in anatomical spread. In this population, 90 % effective dose is a more useful measure to aim for clinically.
The following paper is of interest:
Relative Analgesic Potencies of Levobupivacaine and Ropivacaine for Caudal Anesthesia in Children. P Ingelmo, G Frawley, M Astuto et al. Anesthesia and Analgesia 2009. Vol 108, No. 3: 805 – 813.
See Journal Watch October 2009 (two papers)
3. Oral Contrast for Abdominal Computed Tomography in Children: The Effects on Gastric Fluid Volume. M Mahmoud, J McAuliffe, H Kim et al. Anesthesia and Analgesia 2010’ 111 (5): 1252 – 1258.
This study aims to determine if children receiving oral contrast up to 1 hour before general anaesthesia have a residual gastric fluid volume of greater than 0.4 ml/kg. Children were identified retrospectively and information gathered by chart review. 365 children received enteric contrast medium (ECM) and IV contrast and 47 children who received only intravenous contrast prior to general anaesthesia or sedation. ECM was administered according to age. Children who were younger received more contrast in ml/kg than children who were older. The volume administered ranged from 12 ml/kg to 18 ml/kg. Contrast administration started 2 hours prior to anaesthesia and ended 1 hour prior to anaesthesia. Gastric fluid volume (GFV) was estimated by radiologists who evaluated the CT scans. In children receiving oral contrast, the residual GFV exceeded 0.4 ml/kg in 49 %. There was no evidence of pulmonary aspiration in any patient. Of the patients who underwent general anaesthesia, there was one incident of vomiting after awake extubation and one incident of vomiting after LMA removal at a deep plane of anaesthesia. Four patients had desaturation in PACU. All of these were related to airway obstruction.
Take Home
Message.
Ingestion of contrast within 2 hours prior to anaesthesia violates the nil by mouth guidelines. However, in children with rapid gastrointestinal transit, waiting for a longer period would result in an inadequate study. Aspiration of gastric contents is a relatively rare complication and would therefore require a much larger study to produce useful information. Residual GFV should in theory correlate with aspiration risk. 0.4 ml/kg is thought to be the maximum volume which if aspirated would not cause significant changes in the lungs. This figure is based on an old study done in obstetric patients. More recent studies have suggested that this maximum volume may be greater. A significant percentage of children had residual volumes exceeding 0.4 ml/kg. Residual GFV is only one of a number of factors that contribute to a risk of aspiration. In practice, when managing these children, it is important to be aware of the timing and volume of contrast administered. This may interact with other patient factors (systemic illness, history of nausea and vomiting, ascites) to determine an individuals risk of aspiration.
See Journal Watch September 2009
4. Anesthetic management of the pediatric bleeding tonsil. Fields, RG, Gencorelli FJ, Litman RS. Pediatric Anesthesia 2010 20: 982 – 986.
This retrospective cohort study investigates the incidence of ventilatory and hemodynamic complications in children undergoing surgery for post-tonsillectomy haemorrhage over a 7 year period. 475 patients required surgical intervention for post tonsillectomy haemorrhage giving an incidence of 2.9 % in this cohort.
The main findings were the following:
- 4.2 % of patients had bradycardia at induction (most had received sux)
- 2.5 % of patents had hypotension.
- 2.7 % of patients were noted to be difficult to intubate. None of these patients had been noted to be difficult at the time of initial surgery. Most were intubated on the first attempt.
- Witnessed aspiration of blood in the glottis occurred in 0.8 % of patients but was not associated with hypoxaemia or ventilatory sequelae.
- Hypoxemia was the most common adverse event, occurring in 9.9% of patients. Of note is the fact that most of these events occurred during extubation or emergence and were not related to difficult intubation.
Take Home Message
The paediatric bleeding tonsil is recognised as a high risk procedure because of the potential for significant undetected hypovolaemia and a difficult airway. Caution should extend to extubation and the immediate postoperative period.
5. Two-agent analgesia versus acetaminophen in children having bilateral myringotomies and tubes surgery. S Rampersad, N Jimenez, H Bradford et al. Pediatric Anesthesia 2010 20: 1028 – 1035.
This study aims to compare the incidence of emergence agitation in children who have received paracetamol alone or paracetamol with either intranasal fentanyl (1 mcg/kg) or intramuscular ketamine (1 mg/kg) for bilateral myringotomy. Analgesia was given via the non- intravenous route because the authors state that intravenous cannulation is uncommon for this procedure in North America. All children received oral midazolam (0.5 mg/kg) pre medication and then underwent inhalational induction and maintenance of anaesthesia with sevoflurane. Paracetamol was given rectally (40 mg/kg). Agitation was measured using the Watcha 4 point sedation scale. The validated and now more widely used PAED scale was unavailable at the time the study was commenced. Pain Scores were measured using the Children’s Hospital of Eastern Ontario Pain Scale (CHEOPS).
The study found that there were no differences between the three groups for the incidence of emergence agitation, pain scores or side effects. They conclude that two-agent-analgesia is not superior to acetaminophen alone for grommets when oral midazolam and sevoflurane are used. The study was 90 % powered to show 20 % difference in agitation scores. However, they did not recruit the required sample size and the power was in fact 86 %. In addition, the incidence of emergence agitation was low further reducing the likelihood of finding a difference.
Take Home Message
It would seem attractive to avoid insertion of an IV for myringotomy. However, I would question the relative invasiveness and practicality of inserting an IV versus rectal paracetamol followed by intranasal fentanyl or intramuscular ketamine. The authors chose fentanyl and ketamine hypothesising that these agents with more rapid onset may reduce pain and therefore agitation during the window period before the onset of rectal paracetamol. Oral paracetamol as pre-medication has a more reliable absorption and a more rapid onset than rectal paracetamol. If given with midazolam pre medication, the analgesic effect is usually present on completion of the procedure.
The study is measuring agitation but treating pain. The authors argue that inadequate analgesia is a potential contributor to emergence agitation. Although pain has been found to be a confounding factor in measuring for emergence delirium, it is important to distinguish between the two entities endeavouring to tailor treatment to each as appropriate.
6. Spinal Anesthesia in children: no longer an anathema. A Rukewe, T Alonge, A Fatiregun. Pediatric Anesthesia 2010 20: 1036 – 1039.
This is a small study that looked at 32 children between ages 2 and 12 who under went spinal anaesthesia for orthopaedic and plastic surgery procedures. They looked at cardiovascular changes, duration of block, length of surgery and length of needle to establish lumbar puncture.
Spinal anaesthesia is uncommonly used in paediatrics. An example of its use is in neonates undergoing inguinal herniotomy. Social and cultural factors would influence the acceptability of this technique to both parents and patients in our setting. In addition, where general anaesthesia is safe the benefit of a regional technique is significantly reduced. In countries where the cost and safety of general anaesthesia come in to play, spinal anaesthesia may be a useful alternative for lower extremity surgery.
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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