September 2024

British Journal of Anaesthesia

Submitted August 2024 by Dr Rory Walsh

Read by 106 Journal Watch subscribers

Study Overview:
This was a systematic review and meta-analysis of 13 randomised controlled trials that compared post-operative pain between sevoflurane and propofol anaesthesia in children.

Methods:
The primary outcome was overall post-operative pain - assessed via the need for rescue analgesia or pain scores.

Secondary outcomes were:
(1) pain scores from pain assessment tools only, and
(2) the requirement of rescue analgesia only

Findings:
For the primary outcome the meta-analysis showed higher odds of post-operative pain in the sevoflurane group vs the propofol group (OR 1.88, 95% confidence interval 1.12 – 3.15).

In studies reporting pain scores only, the sevoflurane group had higher odds of post-operative pain (OR 3.18, 95% CI 1.83 – 5.53).

In studies reporting rescue analgesia requirements the sevoflurane group had higher odds of post-operative pain (OR 1.6, 95% CI 0.89 – 2.88).

Hence the review suggests that children maintained on sevoflurane are at greater risk of post-operative pain than those maintained on propofol. However, the authors recommend that further study is warranted.

Take Home Messages and Commentary

1) Does the study address a relevant and / or important question?
Identifying whether propofol or sevoflurane is associated with superior post-operative pain control would help with agent selection - especially for patients at risk of significant post-operative pain.

2) Is there any recent research, evidence, or study on a similar question?
To date it has been unclear whether post-operative pain is significantly affected by the choice of propofol or sevoflurane anaesthesia.

In 2016 Peng et al published a meta-analysis of adult RCTs. This analysis found that compared to volatile anaesthesia, propofol anaesthesia was associated with reduced post-operative pain. However, due to substantial heterogeneity of the included trials, the authors could not draw firm conclusions and recommended further large RCTs be performed. There have been no prior meta-analyses of paediatric trials where post-operative pain was a primary outcome.

3) What are the strengths of the study?
The main strengths of the current meta-analysis is that it included a large number of studies covering a broad range of surgical procedures.

4) What are the limitations of the study?
The authors acknowledged moderately high heterogeneity among the studies, and that some studies did not report the use of intra-operative analgesia. Controlling for intra-operative analgesia would seem to be fundamental in an RCT assessing post-operative pain.

5) Is the study applicable to our practice or to our population?
The included studies incorporated a broad range of paediatric surgical procedures with patient ages ranging from 2 months to 12 years. However, there is limited information regarding the intraoperative analgesia, regional blocks or local anaesthetic used. This might affect applicability to local practice.

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Anesthesia Analgesia

Submitted August 2024 by Dr Marlene Johnson

Read by 91 Journal Watch subscribers

Summary:
This study describes the development of a simple, predictive nomogram using pre-operative variables for heparin resistance in neonates and young infants undergoing cardiac surgery.

Methods:
Heparin resistance was defined as the failure to achieve an ACT of 410 seconds or greater after the administration of 400U/kg heparin. In this single-centre retrospective study of 296 patients, patients were divided into a development cohort (70%), and a validation cohort (30%). The development cohort was used to identify predictors of heparin resistance and to establish a nomogram, whilst the validation cohort was used to test the efficacy of the nomogram.

Key Findings:
The predictors of heparin resistance were identified as:
- Antithrombin activity
- Platelet count
- Fibrinogen level

Using these 3 factors, the prediction model achieved an area under the receiver operating characteristic curve of 0.88 and 0.87 in the development and validation cohorts, indicating the clinical utility of the prediction model. The model performed well in both neonatal and infant sub-groups.

Discussion:
The authors present a simple to use clinical tool that can be used pre-operatively to identify young patients at risk of heparin resistance. The authors argue that their nomogram may help to tailor the heparin dose to the patient, thereby avoiding “over-anticoagulation” (which may lead to heparin rebound and post-operative bleeding) as well as “under-anticoagulation” (which may result in repeated dosing and prolonged overall operative time). They did not provide suggestions for tailored anti-coagulation management, or a threshold for the risk score to trigger active management.

Apart from the usual limitations of a small, single centre, retrospective study, there were several other limitations. First, baseline ACT values were not measured, so the heparin sensitivity index (a more robust method of determining heparin responsiveness) could not be calculated. Second, the authors tried to identify as many “potential predictors” of heparin resistance as possible in the initial stage of the study, before the final three (listed above) were selected. This increases the type I error, or likelihood of a false positive error. Finally, heparin resistance is commonly defined as an ACT >480s. In this study, it was defined as ACT >410s due to differences in their assay equipment and technology, thereby reducing the external validity of their result.

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Pediatric Anesthesia

Submitted August 2024 by Dr Chloe Heath

Read by 100 Journal Watch subscribers

Endoscopic removal of oesophageal foreign bodies (EFB) in children is an urgent or emergency procedure traditionally performed with endotracheal intubation under general anaesthesia. A shift in practice has seen use of a natural airway combined with propofol based anaesthesia, a technique referred to as Monitored Anaesthesia Care (MAC) in select patients.

This single-centre retrospective cohort study looked at flexible endoscopic EFB removal in children (aged 1.6 – 8.2 years) comparing the MAC and endotracheal intubation techniques. Investigators analysed 326 cases using descriptive statistics to compare the safety and efficacy of techniques. Factors related to initial choice of airway technique, perioperative complications and conversion rates (MAC to endotracheal intubation) were examined. In the cohort, 23% were planned for intubation and 77% were planned for MAC with an intubation conversion rate of 0.9% (n = 3). Conversion related to airway reactivity and challenging airway anatomy, with two of the patients requiring hospitalisation for exacerbation of airway reactivity.

Regarding other complications, no patients had reflux of gastric content, dislodgement of the foreign body to the airway or need for cardiopulmonary support. Factors associated with choice of MAC over intubation were:
- Fasting time of > 6 hours
- Coin foreign body

Intubation was conducted for all patients under 2 years of age, all patients with a button battery EFB and was favoured in cases of proximal versus distal EFB. Intubation was associated with a median of 15 minutes extra operating time. Post anaesthesia care unit times were similar between groups (no statistically significant difference).

Commentary and Take Home Messages.
The conduct of MAC in the setting of elective endoscopic oesophageal procedures is well established so there is merit in examining the safety and efficacy of MAC in the management of endoscopic EFB removal. Benefits could include avoiding risk of airway trauma and reducing theatre time to improve cost-effectiveness. However, risks associated with performing procedures under sedation with an unprotected airway must be considered. This study shows that MAC is potentially safe in select paediatric patients undergoing flexible endoscopic removal of EFB, namely those with a coin foreign body, patients fasted > 6 hours, patients with no signs or history of airway reactivity and patients expected to undergo a short uncomplicated procedure. However, no recommendations on best practice can be made.

The study has several key limitations. This is a single-centre retrospective analysis and therefore low quality of evidence. Furthermore, no clinically meaningful outcomes were suggested by findings. No difference in anaesthesia adverse events based on choice of technique or time to recovery were found. Whilst intubation cases were associated with longer operating time, this could be attributed to the more complex nature of the cases associated with higher risk foreign bodies such as button batteries.

Choice of MAC versus endotracheal intubation in this patient cohort remains dependent on expert case by case assessment and risk benefit analysis by the treating anaesthesia care provider. Prospective multi-site studies are needed to guide evidence-based practice and assess clinically meaningful outcomes.

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Pediatric Anesthesia

Submitted August 2024 by Dr Aisling Gormley

Read by 65 Journal Watch subscribers

This single centre, prospective observational study, performed in a paediatric endoscopy unit between November 2021 and June 2022 examines the relationship between ultrasound measured gastric antrum cross-sectional areas (CSAs), and volumes aspirated by endoscopic suction. It aims to determine a cutoff for antral CSA that correlates with empty stomach diagnosis and assess the utility of a three-point qualitative grading system for identifying the “at risk” stomach.

46 children <2 years, fasted to standard guidelines for age, ASA I or II, undergoing elective gastroscopy were recruited. All children were lightly sedated to tolerate examination whilst maintaining spontaneous ventilation.

A single experienced operator undertook ultrasound of the gastric antrum in supine and right lateral decubitus (RLD). Antral CSA, and gastric contents were assessed. Gastroscopy was then undertaken. All gastric content was aspirated under direct vision and recorded. The 3-point grading system stratified patients as Grade 0 for empty appearances in supine and RLD, Grade 1 for gastric content seen in RLD only, Grade 2 for gastric content seen in both supine and RLD.

• Significant correlation was found between aspirated gastric volume and RLD CSA (p 0.003), but not for supine CSA.
• Mean aspirate was 0.13± 0.22ml/kg, indicating all patients had aspirates below the volume considered at risk for paediatric patients (1.25ml/kg).
• Optimal CSA cutoff for an empty antrum was determined by Youden’s Index as <2.40cm2, measured in RLD (sens 100% spec 68.6%).
• The grading system classified patients as Grade 0- 76.1%, Grade 1- 23.9%, and Grade 2- 0%. Patients with a Grade 0 antrum had minimal or no gastric aspirate (median 0.0ml/kg; 0.0-0.09 IQR; sig p<0.001). Those with Grade 1 antrum had significantly higher CSA when measured in RLD compared with supine.

Discussion points:
This was a small study, but findings are in keeping in with similar work. RLD CSA measurement predictably correlates better than supine CSA for aspirated gastric volume. Findings suggest that measurement of supine CSA alone has limited diagnostic value. A CSA of 2.40cm2 measured in RLD is 100% sensitive for diagnosing an empty stomach, allowing the assessing anaesthetist to confidently treat as fasted. However, where CSA is greater a more detailed assessment including mathematical formulae is advocated.

The grading system provided additional information on gastric “fullness” and should be used in conjunction with RLD CSA measurement to assist in decision-making.

ASA III and above children were excluded. This limits extrapolation as these groups will be more likely to have conditions or take medications altering gastric motility. Further research is needed in this area and this group may benefit most from gastric ultrasound.

Take home Message:
This study demonstrates that gastric ultrasound can be used to safely identify fasted and “at risk” stomachs and avoid unnecessary cancellation or intubation.

Given that co-operation can be challenging, isolated measurement of antral CSA taken in RLD can be used to confirm fasted state, but additional measurements and grading can add to operator confidence. A note of caution- the operator in this study was highly experienced in imaging techniques, but those of us less experienced with gastric ultrasound may need to upskill prior to committing to anaesthesia based on our ultrasound findings alone.

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Anesthesia Analgesia

Submitted August 2024 by Dr Aileen Fenelon

Read by 49 Journal Watch subscribers

Summary
This prospective comparative analysis study aimed to evaluate the feasibility of recording cAMP’s (compound muscle action potentials) from the lower extremity and compared paired responses from the foot and the hand in paediatric patients undergoing surgical procedures requiring the administration of neuromuscular blocking agents.

50 paediatric patients ranging in age from 3 months to 7.9 years, undergoing inpatient surgery requiring neuromuscular blocking agent administration were included. Patients with a history of a peripheral neurologic, myopathic, or neuropathic disease, or peripheral oedema were excluded. Electromyographic (EMG) monitoring was performed simultaneously in each participant at the hand (ulnar nerve, adductor pollicis muscle) and the foot (posterior tibial nerve, flexor hallucis brevis muscle). Specially designed paediatric recording electrodes (TetraSens Paediatric) were applied.

• The baseline T1 was higher at the foot than the hand by an average of 4.47mV (P<0.0001).
• The TOFR at baseline and the maximum TOFR achieved were not different at the hand versus the foot.
• The onset time of the change in the T1 amplitude to either 10% or 5% of the baseline T1 amplitude was delayed at the foot compared to the hand by approximately 90 seconds.
• The recovery time to a TOFR >0.9 at the foot after it had already reached a value of 0.9 at the hand was approximately 3 minutes.
• The final TOFR achieved at recovery was approximately 100% and was not different between the two sites.

Take Home Message
- Routine neuromuscular monitoring is possible in paediatric anaesthesia.
- The foot is an acceptable alternative when upper limbs inaccessible.
- Slight delay in block onset time at the foot may result in:
o Delayed laryngoscopy, reduced clinical productivity, but have similar if not better intubating conditions.
o In the case of mRSI, delay may result in patient harm.
- Delay in recovery of TOFR at foot after sugammadex administration may result in slight efficiency implications but may have a greater level of safety.
- A strength of this study was the wide range of patient ages included.

There are several limitations to consider. The researchers were unable to accurately determine block onset times from the first administration of the neuromuscular blocking agent due to inaccuracy in recording time. Given the intrinsic time pressure of the operating theatre, they were also unable to ensure that neuromuscular monitoring and calibration of monitors always preceded the administration of neuromuscular blocking agents.

Considering that neuromuscular monitoring has become a standard of care in adult anaesthesia, this study is clinically relevant and timely. As a small single centre study, it is unlikely to change clinical practise but demonstrates the feasibility of routine neuromuscular monitoring in paediatric anaesthesia, and the possibility of safe and effective alternatives to adductor pollicis muscle monitoring. The authors correctly conclude that additional studies correlating the neuromuscular response at the foot with conditions for tracheal intubation and extubation are needed to develop recommendations on the timing of these events.

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Anaesthesia

Submitted August 2024 by Dr Heather Patterson

Read by 68 Journal Watch subscribers

The focus for the 7th National Audit Project (NAP7) was perioperative cardiac arrest. This paper by Oglesby and colleagues synthesizes the paediatric data from NAP7, highlighting risk factors and management practices in the United Kingdom. Of note, 62% of cases were assessed to have had ‘good’ quality of care, suggesting scope for improvement in the remaining cases. Review of the major findings invites reflection on these themes in the Australian and New Zealand context.

Methods
All NHS hospitals undertaking anaesthesia care in the UK were invited to participate. Data collection included a baseline survey of anaesthesia departments, 4-day activity survey (extrapolated to provide denominator data), and a 12-month prospective registry of perioperative cardiac arrests. Critically ill children undergoing anaesthesia before retrieval to tertiary centres were also included. Multidisciplinary peer review allowed qualitative analysis of events surrounding arrests.

Key Findings
• Incidence: Cardiac arrest occurred in 3 per 10, 000 paediatric cases
• Mortality: Immediate mortality rate was 17%
• Setting: 85% of cases occurred in tertiary paediatric hospitals, with 39% occurring postoperatively, primarily in paediatric ICUs.
• Precipitating events: severe hypoxaemia (22%), bradycardia (11%), and major haemorrhage (8%). Tamponade and isolated severe hypotension were important precipitants in cardiac surgery and cardiac interventional procedures.

Major themes:
• Patient factors
Highest incidence occurred in neonates, infants and children with congenital heart disease (CHD). 86% of arrests occurred in children with ASA 3 or higher. Authors noted that ASA status was under-scored in 5.8% of cases, a trend also observed in the adult data.

• Surgical factors
Majority of arrests were associated with non-elective procedures, particularly in cardiac surgery (29%), ENT (13%), interventional cardiology (12%), and lower gastrointestinal surgery (11%).

• Anaesthetic factors
The authors reported several modifiable anaesthetic factors, including inappropriate dose intravenous induction agents in hemodynamically compromised patients and high concentration volatile agents at induction. There were several cases in which bradycardia requiring chest compressions was treated with atropine or glycopyrrolate instead of adrenaline.

Monitoring was also cited as an issue, including lack of basic monitoring at induction, and inadequate monitoring during interventional cardiac procedures in patients with known CHD. In their discussion, the authors recommend early invasive BP (IBP) monitoring, with a second/additional IABP line if prolonged periods without access to an IBP placed by the proceduralist is anticipated. This recommendation is not without controversy. In practice, higher risk patients (neonates and infants with CHD) often present the greatest technical challenge and vulnerability to associated risks of IABP insertion.

• Airway management
Airway events were a major cause for postoperative arrests in PICU and NICU, including ETT dislodgement or obstruction, highlighting the importance of focused patient handover, and rescue airway plan.

Authors made comment on gaps in preparedness for paediatric airway emergencies, with 15% of departments lacking access to advanced paediatric airway equipment (e.g. video laryngoscopes) in all anaesthetising locations.

• Training and Education
While 94% of cases had a consultant present at induction, only 66% of anaesthetists had up- to-date paediatric advanced life support training, compared to 90% in adult cases. Centralisation of specialist paediatric services and the need for focused education for those not routinely anaesthetising children were noted as challenges.

Conclusion
The NAP7 findings underscore the importance of risk stratification, early appropriate monitoring, and appropriate drug selection and dosing in paediatric anaesthesia. The results are relevant to practitioners in Australia and New Zealand, particularly regarding the management of high-risk groups. The authors raise some contentious points regarding invasive blood pressure monitoring in patients undergoing interventional cardiology procedures.

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