August 2024

Pediatric Anesthesia

Submitted July 2024 by Dr K C Law

Read by 190 Journal Watch subscribers

Rationale

This study is based upon the practice of inverse ratio ventilation (IRV) used in ARDS (acute respiratory distress syndrome) to improve oxygenation and lung function. IRV can be used to prevent alveoli collapse through constant maintenance of lung inflation by increasing inspiratory time, reducing airway pressure and elevating mean airway pressure.

In neonates with oesophageal atresia/tracheooesophageal fistula, it is thought that a ventilation strategy that can maintain oxygenation during one lung ventilation phase of their open thoracotomy surgery can reduce hypoxemia, reduce surgery time and reduce the incidence of surgery being paused due to oxygenation issues. Potential IRV downsides include air entrapment (auto-PEEP), barotrauma, volutrauma, air leaks, decreased venous return and increased pulmonary vascular resistance.

Design

This is a single centre, prospective, blinded study comparing conventional ratio ventilation (CRV) using I:E (inspiratory : expiratory) ratio of 1:2, with inverse ratio ventilation (IRV) using I:E of 2:1 in a sample of 40 term neonates undergoing open right thoracotomy to repair oesophageal atresia / tracheoesophageal fistula in a paediatric hospital in Cairo, Egypt.

The study was approved by their local medical ethics committee and potential participants' parent / guardian was approached for consent. Exclusion criteria were:
- prematurity ≤36 weeks
- low weight <2.5 kg
- age >28 days
- significant congenital heart disease including cyanotic heart disease
- single ventricle pathology, large intracardiac defect with significant left to right shunt
- severe pulmonary hypertension more than 50 mmHg
- pneumonia or severe chest infection prior to the surgery and parent/guardian refusal

Of the 47 potential participants, 40 were successfully recruited and allocated using 1:1 ratio randomly using a computer-generated list sealed in opaque envelope. The sample size of 20 per arm of study gives 83% power to detect difference between group proportions of 0.4.

All participants were cared for in a comparable way at a neonatal intensive care unit preoperatively under neonatologist guidance; had standardised anaesthesia monitoring including preductal and postductal pulse oximetry; standardised anaesthesia medication and maintenance aims specifically keeping FiO2 at lower limit to keep preductal saturations >=92% with minimum FiO2 of 0.3; mechanically ventilated with SIMV-PCV (synchronised intermittent mandatory ventilation-pressure controlled ventilation) peak inspiratory pressure (PIP) 10–15 cmH2O above positive end-expiratory pressure (PEEP) of 5 cmH2O to achieve expired tidal volume (VTE) from 7 to 10 mL/kg, respiratory rate (RR) ranging from 30 to 50 breath/min to achieve end-tidal CO2 (EtCO2) from 30 to 40 mmHg, and pressure support (PS) 12 cmH2O; and operated on by the same paediatric surgical team.

Results

The IRV group experienced 13 desaturation episodes, needed lower FiO2 and had shorter operative time of 113 ± 18 min (range of 97–150 min); compared with the CRV group with 38 desaturation episodes and operative time 130 ± 29 min (range of 80–170 min). There were no significant differences in other complications between the two groups, and no major complications were noted. The authors concluded that IRV may have a role in decreasing incidences of hypoxemia for neonates undergoing open repair of oesophageal atresia/tracheoesophageal fistula.

Take Home Message

This small study adds on to the paucity of neonatal intraoperative literature surrounding IRV use, and is based upon acceptable ventilation strategy in intensive care setting. The authors discussed limitations of the study including potential inaccuracy of estimating PaO2 from SpO2 as arterial lines were not used, not confirming exact position of endotracheal tube using bronchoscopy, small sample size and lack of similar neonatal studies to compare result with.

Personally, I ponder whether IRV results would be affected by other variables such as type of ventilator used and surgical techniques (e.g. thoracoscopic rather than open approach), and whether use of cerebral oximetry to further inform on perfusion state of the patient will be more useful rather than hypoxemia as outcome measure. Although I would not convert to use IRV as a routine, in the neonate who is difficult to ventilate and oxygenate using CRV, I will be more likely to seek advice and help from my NICU colleagues to institute IRV/oscillator ventilation as an alternative strategy.

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Pediatric Anesthesia

Submitted July 2024 by Dr Kevin McCarthy

Read by 241 Journal Watch subscribers

This was an RCT of microcuff oral RAE versus uncuffed oral RAE endotracheal tubes for cleft palate surgery.

The microcuff tubes were associated with a lower tube exchange rate (0% vs. 38%) and lower rate of endobronchial intubation (0% vs. 6%).

All patients had throat packs, and assessment of tube depth for the uncuffed tubes was not reported, so there are some limitations to the clinical ‘take home message’ from this study. There was no economic analysis in this study, however one could make the case that the greater per item cost of microcuff tubes may be offset by needing to use fewer of them.

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European Journal of Anaesthesiology

Submitted July 2024 by Dr Ben Blaise

Read by 262 Journal Watch subscribers

Study type:
This is a prospective randomised double blind trial in a single paediatric tertiary centre.

Methods:
64 children aged 1 to 10y referred for elective spinal dysraphism surgery.
Patients were randomly allocated to the intranasal atomised dexmedetomidine (2.5mcg/kg) or intranasal atomised ketamine (5mg/kg) groups. Premedication was given 30min before surgery.
The primary outcome was the level of sedation (using the University of Michigan Sedation Score). Secondary outcomes included ease of parental separation, intravenous cannulation, satisfactory mask acceptance and perioperative vitals.

Findings:
Better sedation was achieved in the dexmedetomidine group (UMSS 1.55 +/- 0.51 vs 1.13 +/- 0.34 at 20min; 2.32 +/- 0.6 vs 1.94 +/- 0.5 at 30min). There was no difference in ease of separation, cannulation and mask acceptance between the 2 groups. Heart rate was lower in the dexmedetomidine group at 10, 20 and 30 min but without clinical significance.

Take home message:
• Relevance of the study
a. Perioperative anxiety is a growing issue with some studies reporting up to 60% anxious patients in the immediate preoperative period.
b. Midazolam and dexmedetomidine are amongst the drugs widely used as premedication.
c. Focus on intranasal administration of these 2 drugs using a new device improving drug delivery.

• Recent research, evidence or study on the subject
2 papers per month published over the last 15 months on perioperative anxiety in children and premedication, exploring different drugs, ways of administering them, for different procedures, as well as effects on patient anxiety, clinical side effects (jarmo dynamic and respiratory) or organisational impact (staff, length of stay in PACU or before discharge).

• Strengths of the study
a. Robust methodology (prospective randomised double blind trial)
b. Investigation of the haemodynamic effects of dexmedetomidine
c. Well-designed trial, including power calculation, statistical analysis and recruitment targets were achieved,
d. Use of the mucosal atomisation device allowing a more efficient administration of intranasal premedication.

• Limitations of the study
a. Clinical relevance of the difference in UMSS found between the 2 groups. Although dexmedetomidine provides a statistically significant difference in terms of sedation compared to midazolam, there was no difference observed in terms of ease of parental separation, cannulation or mask acceptance.
b. Authors didn’t use the modified Yale Preoperative Anxiety Scale (usually considered as the gold standard for pre operative anxiety evaluation).
c. Authors’ self-declared limitations: single centre study with small sample size, absence of age stratification, baseline anxiety of the patients

• Applicable to our practice?
Yes, these results should be easily transferrable to other procedures and hospitals. Having robust data on the intranasal use of midazolam and dexmedetomidine is useful in children with behavioural issues likely to spit out any drug given orally.

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Pediatric Anesthesia

Submitted July 2024 by Dr John Burnett

Read by 141 Journal Watch subscribers

It is well known that ex-premature infants are a high risk patient group, particularly with regard to perioperative apnoea. A question that is front of mind for most paediatric anaesthetists is “how can we use regional anaesthesia safely and effectively to improve outcomes for this vulnerable group of patients?”

We know that spinal anaesthesia for infant hernia repair compared to GA is associated with a lower risk of apnoea, however it does have an appreciable failure rate. Additionally, for success it requires a relatively short surgical time and, although not necessarily borne out in the literature, many clinicians opine that there is a learning curve involved in performing spinals in this group.
Awake caudal anaesthesia is proposed as a potential solution to these limitations.

The aim of this narrative review was to determine, from the available literature, whether awake caudal anaesthesia is a feasible and reliable procedure with low complication rates in ex-prem infants having abdominal surgery.

The authors (both with significant knowledge and experience in awake regional techniques) concluded that there was insufficient evidence to validate or refute the benefits of the use of awake caudal anaesthesia in premature and ex-prem infants.

The overall quality of the data was poor, with 45 reports analysed in total, including 8 RCTs as well as non-randomised prospective and retrospective series. There was significant heterogeneity and incomplete data reporting, overall preventing a systematic review.

The review included 558 (36%) cases of awake caudal, 837 (54.1%) cases of “awake” caudal with sedation and 153 (9.9%) cases of combined spinal caudal epidural (CSEA) without sedation.
Main findings:
1) Marked variability in approaches to “awake” caudal anaesthesia. Original description of awake was using no sedation, but more recently the technique seems to involve sedation for initiation and/or throughout (for example with sevoflurane, propofol or dexmedetomidine)

2) Slow onset of surgical anaesthesia (although only 35% of papers reported onset times)

3) Overall failure rates and perioperative apnoea rates were considered high:
- Failure rates were highest for CSEA (13.7%), intermediate for awake caudal (6.6%) and lowest for “awake” caudal with sedation (5.85%). Non-significant differences.
- The incidence of perioperative apnoea was highest for “awake” caudal with sedation (8.16%), intermediate for awake caudal (7.62%) and lowest for CSEA (5.53%). These differences were not significant.

4) It was noted that large doses (often more than max recommended) of local anaesthetic was common and there was a significantly higher rate of high spinal blocks in the larger series.

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Canadian Journal of Anaesthesia

Submitted June 2024 by Dr Michael Tan

Read by 127 Journal Watch subscribers

Bleeding, often because of unintentional injury, is a leading cause of death in children
Massive haemorrhage protocols improve outcomes. Dedicated paediatric protocols are needed due to unique physiological needs of children.

This study surveyed Canadian university affiliated paediatric centres with a validated questionnaire
They asked for information regarding paediatric massive haemorrhage protocols and activation data
All 18 centres approached provided a response. 5 did not have a dedicated paediatric massive haemorrhage protocol.

There was huge variability in protocols with regards to activation criteria, and transport container contents.
Trauma was the most common cause for activation (54%). There was suggestion of underutilisation in non-traumatic bleeding.

The researchers conclude that in Canada, there is a need for consensus definition of paediatric massive haemorrhage, a validated activation tool along with a centralised data collection system.
In New Zealand, the Health Quality and Safety Commission has already created evidence-based care bundles to provide guidance for massive transfusion in a wide range of populations including paediatrics. Individual hospitals can then customise the care bundles to establish massive haemorrhage protocols suited to their institutions.

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Pediatric Anesthesia

Submitted June 2024 by Dr H Hack

Read by 304 Journal Watch subscribers

Study Aim & background
To determine the overall spinal failure rate, incidence of second spinal attempt and success rate and any associated adverse events in infants. The Royal Children's Hospital, Melbourne has a long established practice of providing (and teaching) awake spinal anaesthesia for infants undergoing lower abdominal surgery such as inguinal hernia repair (this reviewer learnt the technique whilst working at RCH many years ago!). Additionally it has a more recently established protocol for the management of a “failed” spinal anaesthetic involving the provision of a second “rescue” spinal anaesthetic by a more experienced anaesthetist.

Design
Retrospective review of infant spinal anaesthetics between May 2016 and June 2023.

Results
There were 551 cases (mean gestational age 33.9 weeks, mean PMA 42.9 weeks, mean Wt.3.8kg).
Overall success rate 90.6%

First attempt success rate 85.5%.

Common causes of failure were “dry tap” (23, 44.2%), poor motor block (16, 30.2%), repeat bloody taps (12, 23.5%).

First attempt failure was most commonly associated with operator inexperience. A repeat spinal anaesthetic by a more experienced operator was very likely to be successful (26/28) but associated with an increased incidence of adverse events: High block (2/28, 7.1% v 3/551, 0.5%) and apnoeas ( 4/28, 14.3% v 37/551, 6.7%). Both cases of high block were occurred in infants that had inadequate motor block following first spinal (suggesting an inadequate LA dose or only partial correct anatomical delivery of the initial LA dose?) and where the second spinal was performed at a higher level (L3,4). Both cases required intubation, IPPV and a brief period of CPR but they were not associated with any long term sequele.

Comments
The author reports valuable data from a centre with a huge amount of departmental experience of providing awake spinal anaesthesia for infant surgery. The vast majority of cases were done by a consultant or fellow. This experience is reflected in the high overall first time success rate of the technique and of a second rescue spinal.

The use of non styletted needles may be considered controversial by some but the rationale (including a lower dry tap rate) and evidence base behind it are cogently discussed.

Potentially concerning is the relatively rare but serious occurrence of a high block following a second spinal. Both cases occurred in the situation of an inadequate motor block following the first spinal anaesthetic, rather than a dry tap or repeated bloody tap and were characterised by the gradual creep upwards of a block causing respiratory depression and bradycardia necessitating intubation and CPR. The reviewer wonders whether one or both cases involved the delivery of an inadequate first LA dose, either an incorrect actual dose or only a partial delivery to the subarachnoid space of a “correct” dose due to technical reasons at injection time. Repeat, identical spinal doses of LA were given (as per protocol), albeit at a higher injection site (L3,4); although the total dose of LA given is below recommended safe limits associated with LA toxicity an excessive subarchnoid dose is likely.

Perhaps in such future, similar cases consideration should be given to a lower access level, use of techniques such as head up position and/or a reduced second dose? The author does not discuss the rationale and/or evidence behind the choice of second spinal anaesthesia rather than the alternative technique of a combined spinal followed by caudal anaesthesia.

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